Sample records for mass balance ice
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Greenland Ice Sheet Mass Balance
NASA Technical Reports Server (NTRS)
Reeh, N.
1984-01-01
Mass balance equation for glaciers; areal distribution and ice volumes; estimates of actual mass balance; loss by calving of icebergs; hydrological budget for Greenland; and temporal variations of Greenland mass balance are examined.
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The mass balance of the ice plain of Ice Stream B and Crary Ice Rise
NASA Technical Reports Server (NTRS)
Bindschadler, Robert
1993-01-01
The region in the mouth of Ice Stream B (the ice plain) and that in the vicinity of Crary Ice Rise are experiencing large and rapid changes. Based on velocity, ice thickness, and accumulation rate data, the patterns of net mass balance in these regions were calculated. Net mass balance, or the rate of ice thickness change, was calculated as the residual of all mass fluxes into and out of subregions (or boxes). Net mass balance provides a measure of the state of health of the ice sheet and clues to the current dynamics.
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Autonomous Ice Mass Balance Buoys for Seasonal Sea Ice
NASA Astrophysics Data System (ADS)
Whitlock, J. D.; Planck, C.; Perovich, D. K.; Parno, J. T.; Elder, B. C.; Richter-Menge, J.; Polashenski, C. M.
2017-12-01
The ice mass-balance represents the integration of all surface and ocean heat fluxes and attributing the impact of these forcing fluxes on the ice cover can be accomplished by increasing temporal and spatial measurements. Mass balance information can be used to understand the ongoing changes in the Arctic sea ice cover and to improve predictions of future ice conditions. Thinner seasonal ice in the Arctic necessitates the deployment of Autonomous Ice Mass Balance buoys (IMB's) capable of long-term, in situ data collection in both ice and open ocean. Seasonal IMB's (SIMB's) are free floating IMB's that allow data collection in thick ice, thin ice, during times of transition, and even open water. The newest generation of SIMB aims to increase the number of reliable IMB's in the Arctic by leveraging inexpensive commercial-grade instrumentation when combined with specially developed monitoring hardware. Monitoring tasks are handled by a custom, expandable data logger that provides low-cost flexibility for integrating a large range of instrumentation. The SIMB features ultrasonic sensors for direct measurement of both snow depth and ice thickness and a digital temperature chain (DTC) for temperature measurements every 2cm through both snow and ice. Air temperature and pressure, along with GPS data complete the Arctic picture. Additionally, the new SIMB is more compact to maximize deployment opportunities from multiple types of platforms.
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Antarctic Ice Mass Balance from GRACE
NASA Astrophysics Data System (ADS)
Boening, C.; Firing, Y. L.; Wiese, D. N.; Watkins, M. M.; Schlegel, N.; Larour, E. Y.
2014-12-01
The Antarctic ice mass balance and rates of change of ice mass over the past decade are analyzed based on observations from the Gravity Recovery and Climate Experiment (GRACE) satellites, in the form of JPL RL05M mascon solutions. Surface mass balance (SMB) fluxes from ERA-Interim and other atmospheric reanalyses successfully account for the seasonal GRACE-measured mass variability, and explain 70-80% of the continent-wide mass variance at interannual time scales. Trends in the residual (GRACE mass - SMB accumulation) mass time series in different Antarctic drainage basins are consistent with time-mean ice discharge rates based on radar-derived ice velocities and thicknesses. GRACE also resolves accelerations in regional ice mass change rates, including increasing rates of mass gain in East Antarctica and accelerating ice mass loss in West Antarctica. The observed East Antarctic mass gain is only partially explained by anomalously large SMB events in the second half of the record, potentially implying that ice discharge rates are also decreasing in this region. Most of the increasing mass loss rate in West Antarctica, meanwhile, is explained by decreasing SMB (principally precipitation) over this time period, part of the characteristic decadal variability in regional SMB. The residual acceleration of 2+/-1 Gt/yr, which is concentrated in the Amundsen Sea Embayment (ASE) basins, represents the contribution from increasing ice discharge rates. An Ice Sheet System Model (ISSM) run with constant ocean forcing and stationary grounding lines both underpredicts the largest trends in the ASE and produces negligible acceleration or interannual variability in discharge, highlighting the potential importance of ocean forcing for setting ice discharge rates at interannual to decadal time scales.
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Trends in ice sheet mass balance, 1992 to 2017
NASA Astrophysics Data System (ADS)
Shepherd, A.; Ivins, E. R.; Smith, B.; Velicogna, I.; Whitehouse, P. L.; Rignot, E. J.; van den Broeke, M. R.; Briggs, K.; Hogg, A.; Krinner, G.; Joughin, I. R.; Nowicki, S.; Payne, A. J.; Scambos, T.; Schlegel, N.; Moyano, G.; Konrad, H.
2017-12-01
The Ice Sheet Mass Balance Inter-Comparison Exercise (IMBIE) is a community effort, jointly supported by ESA and NASA, that aims to provide a consensus estimate of ice sheet mass balance from satellite gravimetry, altimetry and mass budget assessments, on an annual basis. The project has five experiment groups, one for each of the satellite techniques and two others to analyse surface mass balance (SMB) and glacial isostatic adjustment (GIA). The basic premise for the exercise is that individual ice sheet mass balance datasets are generated by project participants using common spatial and temporal domains to allow meaningful inter-comparison, and this controlled comparison in turn supports aggregation of the individual datasets over their full period. Participation is open to the full community, and the quality and consistency of submissions is regulated through a series of data standards and documentation requirements. The second phase of IMBIE commenced in 2015, with participant data submitted in 2016 and a combined estimate due for public release in 2017. Data from 48 participant groups were submitted to one of the three satellite mass balance technique groups or to the ancillary dataset groups. The individual mass balance estimates and ancillary datasets have been compared and combined within the respective groups. Following this, estimates of ice sheet mass balance derived from the individual techniques were then compared and combined. The result is single estimates of ice sheet mass balance for Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula. The participants, methodology and results of the exercise will be presented in this paper.
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Ice-sheet mass balance and climate change.
Hanna, Edward; Navarro, Francisco J; Pattyn, Frank; Domingues, Catia M; Fettweis, Xavier; Ivins, Erik R; Nicholls, Robert J; Ritz, Catherine; Smith, Ben; Tulaczyk, Slawek; Whitehouse, Pippa L; Zwally, H Jay
2013-06-06
Since the 2007 Intergovernmental Panel on Climate Change Fourth Assessment Report, new observations of ice-sheet mass balance and improved computer simulations of ice-sheet response to continuing climate change have been published. Whereas Greenland is losing ice mass at an increasing pace, current Antarctic ice loss is likely to be less than some recently published estimates. It remains unclear whether East Antarctica has been gaining or losing ice mass over the past 20 years, and uncertainties in ice-mass change for West Antarctica and the Antarctic Peninsula remain large. We discuss the past six years of progress and examine the key problems that remain.
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The Ice Sheet Mass Balance Inter-comparison Exercise
NASA Astrophysics Data System (ADS)
Shepherd, A.; Ivins, E. R.
2015-12-01
Fluctuations in the mass of ice stored in Antarctica and Greenland are of considerable societal importance. The Ice Sheet Mass Balance Inter-Comparison Exercise (IMBIE) is a joint-initiative of ESA and NASA aimed at producing a single estimate of the global sea level contribution to polar ice sheet losses. Within IMBIE, estimates of ice sheet mass balance are developed from a variety of satellite geodetic techniques using a common spatial and temporal reference frame and a common appreciation of the contributions due to external signals. The project brings together the laboratories and space agencies that have been instrumental in developing independent estimates of ice sheet mass balance to date. In its first phase, IMBIE involved 27 science teams, and delivered a first community assessment of ice sheet mass imbalance to replace 40 individual estimates. The project established that (i) there is good agreement between the three main satellite-based techniques for estimating ice sheet mass balance, (ii) combining satellite data sets leads to significant improvement in certainty, (iii) the polar ice sheets contributed 11 ± 4 mm to global sea levels between 1992 and 2012, and (iv) that combined ice losses from Antarctica and Greenland have increased over time, rising from 10% of the global trend in the early 1990's to 30% in the late 2000's. Demand for an updated assessment has grown, and there are now new satellite missions, new geophysical corrections, new techniques, and new teams producing data. The period of overlap between independent satellite techniques has increased from 5 to 12 years, and the full period of satellite data over which an assessment can be performed has increased from 19 to 40 years. It is also clear that multiple satellite techniques are required to confidently separate mass changes associated with snowfall and ice dynamical imbalance - information that is of critical importance for climate modelling. This presentation outlines the approach
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Recent Changes in Ices Mass Balance of the Amundsen Sea Sector
NASA Astrophysics Data System (ADS)
Sutterley, T. C.; Velicogna, I.; Rignot, E. J.; Mouginot, J.; Flament, T.; van den Broeke, M. R.; van Wessem, M.; Reijmer, C.
2014-12-01
The glaciers flowing into the Amundsen Sea Embayment (ASE) sector of West Antarctica were confirmed in the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) to be the dominant contributors to the current Antarctic ice mass loss, and recently recognized to be undergoing marine ice sheet instability. Here, we investigate their regional ice mass balance using a time series of satellite and airborne data combined with model output products from the Regional Atmospheric and Climate Model (RACMO). Our dataset includes laser altimetry from NASA's ICESat-1 satellite mission and from Operation IceBridge (OIB) airborne surveys, satellite radar altimetry data from ESA's Envisat mission, time-variable gravity data from NASA/DLR's GRACE mission, surface mass balance products from RACMO, ice velocity from a combination of international synthetic aperture radar satellites and ice thickness data from OIB. We find a record of ice mass balance for the ASE where all the analyzed techniques agree remarkably in magnitude and temporal variability. The mass loss of the region has been increasing continuously since 1992, with no indication of a slow down. The mass loss during the common period averaged 91 Gt/yr and accelerated 20 Gt/yr2. In 1992-2013, the ASE contributed 4.5 mm global sea level rise. Overall, our results demonstrate the synergy of multiple analysis techniques for examining Antarctic Ice Sheet mass balance at the regional scale. This work was performed at UCI and JPL under a contract with NASA.
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NASA Astrophysics Data System (ADS)
Ivins, E. R.; Wahr, J. M.; Schrama, E. J.; Milne, G. A.; Barletta, V.; Horwath, M.; Whitehouse, P.
2012-12-01
In preparation for the Inter-govermental Panel on Climate Change: Assessment Report 5 (IPCC AR5), ESA and NASA have formed a committee of experts to perform a formal set of comparative experiments concerning space observations of ice sheet mass balance. This project began in August of 2011 and has now concluded with a report submitted for Science (Shepherd et al., 2012). The focus of the work conducted is to re-evaluate scientific reports on the mass balance of Greenland ice sheet (GIS) and Antarctic ice sheet (AIS). The most serious discrepancies have been reported for the AIS, amounting to as much as 0.9 mm/yr in discrepant sea level contribution. A direct method of determining the AIS is by space gravimetry. However, for this method to contribute to our understanding of sea level change, we require knowledge of present-day non-elastic vertical movements of bedrock in Antarctica. Quantifying the uncertainty and bias caused by lack of observational control on models of regional glacial isostatic adjustment (GIA), was a major focus for our experiments. This regional process is the most problematic error source for GRACE-determinations of ice mass balance in Antarctica. While GIA likely dominates some large vertical motions in Antarctica that are now observed with GPS (Thomas et al., 2011, GRL), interpretations still require models. The reported uncertainty for space gravimetric (GRACE) based sea level sourcing is roughly 0.20 to 0.35 mm/yr. The uncertainty is also part of the error budget for mass balances derived from altimetry measurements, though at a much lower level. Analysis of the GRACE time series using CSR RL04 (2003.0-2010.10) for AIS mass balance reveals a small trend of order +1 to -24 Gt/yr without a GIA correction. Three periods were selected over which to perform inter-comparisons (see Table). One class of GIA models, that relies primarily on far field sea level reconstructions (e.g. ICE-5G), provide a GIA correction that places AIS mass imbalance (
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A reconciled estimate of ice-sheet mass balance.
Shepherd, Andrew; Ivins, Erik R; A, Geruo; Barletta, Valentina R; Bentley, Mike J; Bettadpur, Srinivas; Briggs, Kate H; Bromwich, David H; Forsberg, René; Galin, Natalia; Horwath, Martin; Jacobs, Stan; Joughin, Ian; King, Matt A; Lenaerts, Jan T M; Li, Jilu; Ligtenberg, Stefan R M; Luckman, Adrian; Luthcke, Scott B; McMillan, Malcolm; Meister, Rakia; Milne, Glenn; Mouginot, Jeremie; Muir, Alan; Nicolas, Julien P; Paden, John; Payne, Antony J; Pritchard, Hamish; Rignot, Eric; Rott, Helmut; Sørensen, Louise Sandberg; Scambos, Ted A; Scheuchl, Bernd; Schrama, Ernst J O; Smith, Ben; Sundal, Aud V; van Angelen, Jan H; van de Berg, Willem J; van den Broeke, Michiel R; Vaughan, David G; Velicogna, Isabella; Wahr, John; Whitehouse, Pippa L; Wingham, Duncan J; Yi, Donghui; Young, Duncan; Zwally, H Jay
2012-11-30
We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth's polar ice sheets. We find that there is good agreement between different satellite methods--especially in Greenland and West Antarctica--and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by -142 ± 49, +14 ± 43, -65 ± 26, and -20 ± 14 gigatonnes year(-1), respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 ± 0.20 millimeter year(-1) to the rate of global sea-level rise.
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Overview of Ice-Sheet Mass Balance and Dynamics from ICESat Measurements
NASA Technical Reports Server (NTRS)
Zwally, H. Jay
2010-01-01
The primary purpose of the ICESat mission was to determine the present-day mass balance of the Greenland and Antarctic ice sheets, identify changes that may be occurring in the surface-mass flux and ice dynamics, and estimate their contributions to global sea-level rise. Although ICESat's three lasers were planned to make continuous measurements for 3 to 5 years, the mission was re-planned to operate in 33-day campaigns 2 to 3 times each year following failure of the first laser after 36 days. Seventeen campaigns were conducted with the last one in the Fall of 2009. Mass balance maps derived from measured ice-sheet elevation changes show that the mass loss from Greenland has increased significantly to about 170 Gt/yr for 2003 to 2007 from a state of near balance in the 1990's. Increased losses (189 Gt/yr) from melting and dynamic thinning are over seven times larger'than increased gains (25 gt/yr) from precipitation. Parts of the West Antarctic ice sheet and the Antarctic Peninsula are losing mass at an increasing rate, but other parts of West Antarctica and the East Antarctic ice sheet are gaining mass at an increasing rate. Increased losses of 35 Gt/yr in Pine Island, Thwaites-Smith, and Marie-Bryd.Coast are more than balanced by gains in base of Peninsula and ice stream C, D, & E systems. From the 1992-2002 to 2003-2007 period, the overall mass balance for Antarctica changed from a loss of about 60 Gt/yr to near balance or slightly positive.
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A Reconciled Estimate of Ice-Sheet Mass Balance
NASA Technical Reports Server (NTRS)
Shepherd, Andrew; Ivins, Erik R.; Geruo, A.; Barletta, Valentia R.; Bentley, Mike J.; Bettadpur, Srinivas; Briggs, Kate H.; Bromwich, David H.; Forsberg, Rene; Galin, Natalia;
2012-01-01
We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth's polar ice sheets. We find that there is good agreement between different satellite methods-especially in Greenland and West Antarctica-and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by -142 plus or minus 49, +14 plus or minus 43, -65 plus or minus 26, and -20 plus or minus 14 gigatonnes year(sup -1), respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 plus or minus 0.20 millimeter year(sup -1) to the rate of global sea-level rise.
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Greenland ice sheet mass balance: a review.
Khan, Shfaqat A; Aschwanden, Andy; Bjørk, Anders A; Wahr, John; Kjeldsen, Kristian K; Kjær, Kurt H
2015-04-01
Over the past quarter of a century the Arctic has warmed more than any other region on Earth, causing a profound impact on the Greenland ice sheet (GrIS) and its contribution to the rise in global sea level. The loss of ice can be partitioned into processes related to surface mass balance and to ice discharge, which are forced by internal or external (atmospheric/oceanic/basal) fluctuations. Regardless of the measurement method, observations over the last two decades show an increase in ice loss rate, associated with speeding up of glaciers and enhanced melting. However, both ice discharge and melt-induced mass losses exhibit rapid short-term fluctuations that, when extrapolated into the future, could yield erroneous long-term trends. In this paper we review the GrIS mass loss over more than a century by combining satellite altimetry, airborne altimetry, interferometry, aerial photographs and gravimetry data sets together with modelling studies. We revisit the mass loss of different sectors and show that they manifest quite different sensitivities to atmospheric and oceanic forcing. In addition, we discuss recent progress in constructing coupled ice-ocean-atmosphere models required to project realistic future sea-level changes.
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Changes in ice dynamics and mass balance of the Antarctic ice sheet.
Rignot, Eric
2006-07-15
The concept that the Antarctic ice sheet changes with eternal slowness has been challenged by recent observations from satellites. Pronounced regional warming in the Antarctic Peninsula triggered ice shelf collapse, which led to a 10-fold increase in glacier flow and rapid ice sheet retreat. This chain of events illustrated the vulnerability of ice shelves to climate warming and their buffering role on the mass balance of Antarctica. In West Antarctica, the Pine Island Bay sector is draining far more ice into the ocean than is stored upstream from snow accumulation. This sector could raise sea level by 1m and trigger widespread retreat of ice in West Antarctica. Pine Island Glacier accelerated 38% since 1975, and most of the speed up took place over the last decade. Its neighbour Thwaites Glacier is widening up and may double its width when its weakened eastern ice shelf breaks up. Widespread acceleration in this sector may be caused by glacier ungrounding from ice shelf melting by an ocean that has recently warmed by 0.3 degrees C. In contrast, glaciers buffered from oceanic change by large ice shelves have only small contributions to sea level. In East Antarctica, many glaciers are close to a state of mass balance, but sectors grounded well below sea level, such as Cook Ice Shelf, Ninnis/Mertz, Frost and Totten glaciers, are thinning and losing mass. Hence, East Antarctica is not immune to changes.
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Estimates of Ice Sheet Mass Balance from Satellite Altimetry: Past and Future
NASA Technical Reports Server (NTRS)
Zwally, H. Jay; Zukor, Dorothy J. (Technical Monitor)
2001-01-01
A major uncertainty in predicting sea level rise is the sensitivity of ice sheet mass balance to climate change, as well as the uncertainty in present mass balance. Since the annual water exchange is about 8 mm of global sea level equivalent, the 20% uncertainty in current mass balance corresponds to 1.6 mm/yr in sea level change. Furthermore, estimates of the sensitivity of the mass balance to temperature change range from perhaps as much as - 10% to + 10% per K. A principal purpose of obtaining ice sheet elevation changes from satellite altimetry has been estimation of the current ice sheet mass balance. Limited information on ice sheet elevation change and their implications about mass balance have been reported by several investigators from radar altimetry (Seasat, Geosat, ERS-1&2). Analysis of ERS-1&2 data over Greenland for 7 years from 1992 to 1999 shows mixed patterns of ice elevation increases and decreases that are significant in terms of regional-scale mass balances. Observed seasonal and interannual variations in ice surface elevation are larger than previously expected because of seasonal and interannUal variations in precipitation, melting, and firn compaction. In the accumulation zone, the variations in firn compaction are modeled as a function of temperature leaving variations in precipitation and the mass balance trend. Significant interannual variations in elevation in some locations, in particular the difference in trends from 1992 to 1995 compared to 1995 to 1999, can be explained by changes in precipitation over Greenland. Over the 7 years, trends in elevation are mostly positive at higher elevations and negative at lower elevations. In addition, trends for the winter seasons (from a trend analysis through the average winter elevations) are more positive than the corresponding trends for the summer. At lower elevations, the 7-year trends in some locations are strongly negative for summer and near zero or slightly positive for winter. These
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Determination of Interannual to Decadal Changes in Ice Sheet Mass Balance from Satellite Altimetry
NASA Technical Reports Server (NTRS)
Zwally, H. Jay; Busalacchi, Antonioa J. (Technical Monitor)
2001-01-01
A major uncertainty in predicting sea level rise is the sensitivity of ice sheet mass balance to climate change, as well as the uncertainty in present mass balance. Since the annual water exchange is about 8 mm of global sea level equivalent, the +/- 25% uncertainty in current mass balance corresponds to +/- 2 mm/yr in sea level change. Furthermore, estimates of the sensitivity of the mass balance to temperature change range from perhaps as much as - 10% to + 10% per K. Although the overall ice mass balance and seasonal and inter-annual variations can be derived from time-series of ice surface elevations from satellite altimetry, satellite radar altimeters have been limited in spatial coverage and elevation accuracy. Nevertheless, new data analysis shows mixed patterns of ice elevation increases and decreases that are significant in terms of regional-scale mass balances. In addition, observed seasonal and interannual variations in elevation demonstrate the potential for relating the variability in mass balance to changes in precipitation, temperature, and melting. From 2001, NASA's ICESat laser altimeter mission will provide significantly better elevation accuracy and spatial coverage to 86 deg latitude and to the margins of the ice sheets. During 3 to 5 years of ICESat-1 operation, an estimate of the overall ice sheet mass balance and sea level contribution will be obtained. The importance of continued ice monitoring after the first ICESat is illustrated by the variability in the area of Greenland surface melt observed over 17-years and its correlation with temperature. In addition, measurement of ice sheet changes, along with measurements of sea level change by a series of ocean altimeters, should enable direct detection of ice level and global sea level correlations.
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Improving Surface Mass Balance Over Ice Sheets and Snow Depth on Sea Ice
NASA Technical Reports Server (NTRS)
Koenig, Lora Suzanne; Box, Jason; Kurtz, Nathan
2013-01-01
Surface mass balance (SMB) over ice sheets and snow on sea ice (SOSI) are important components of the cryosphere. Large knowledge gaps remain in scientists' abilities to monitor SMB and SOSI, including insufficient measurements and difficulties with satellite retrievals. On ice sheets, snow accumulation is the sole mass gain to SMB, and meltwater runoff can be the dominant single loss factor in extremely warm years such as 2012. SOSI affects the growth and melt cycle of the Earth's polar sea ice cover. The summer of 2012 saw the largest satellite-recorded melt area over the Greenland ice sheet and the smallest satellite-recorded Arctic sea ice extent, making this meeting both timely and relevant.
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Calibrating a surface mass-balance model for Austfonna ice cap, Svalbard
NASA Astrophysics Data System (ADS)
Schuler, Thomas Vikhamar; Loe, Even; Taurisano, Andrea; Eiken, Trond; Hagen, Jon Ove; Kohler, Jack
2007-10-01
Austfonna (8120 km2) is by far the largest ice mass in the Svalbard archipelago. There is considerable uncertainty about its current state of balance and its possible response to climate change. Over the 2004/05 period, we collected continuous meteorological data series from the ice cap, performed mass-balance measurements using a network of stakes distributed across the ice cap and mapped the distribution of snow accumulation using ground-penetrating radar along several profile lines. These data are used to drive and test a model of the surface mass balance. The spatial accumulation pattern was derived from the snow depth profiles using regression techniques, and ablation was calculated using a temperature-index approach. Model parameters were calibrated using the available field data. Parameter calibration was complicated by the fact that different parameter combinations yield equally acceptable matches to the stake data while the resulting calculated net mass balance differs considerably. Testing model results against multiple criteria is an efficient method to cope with non-uniqueness. In doing so, a range of different data and observations was compared to several different aspects of the model results. We find a systematic underestimation of net balance for parameter combinations that predict observed ice ablation, which suggests that refreezing processes play an important role. To represent these effects in the model, a simple PMAX approach was included in its formulation. Used as a diagnostic tool, the model suggests that the surface mass balance for the period 29 April 2004 to 23 April 2005 was negative (-318 mm w.e.).
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Land motion due to 20th century mass balance of the Greenland Ice Sheet
NASA Astrophysics Data System (ADS)
Kjeldsen, K. K.; Khan, S. A.
2017-12-01
Quantifying the contribution from ice sheets and glaciers to past sea level change is of great value for understanding sea level projections into the 21st century. However, quantifying and understanding past changes are equally important, in particular understanding the impact in the near-field where the signal is highest. We assess the impact of 20th century mass balance of the Greenland Ice Sheet on land motion using results from Kjeldsen et al, 2015. These results suggest that the ice sheet on average lost a minimum of 75 Gt/yr, but also show that the mass balance was highly spatial- and temporal variable, and moreover that on a centennial time scale changes were driven by a decreasing surface mass balance. Based on preliminary results we discuss land motion during the 20th century due to mass balance changes and the driving components surface mass balance and ice dynamics.
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NASA Astrophysics Data System (ADS)
Visnjevic, Vjeran; Herman, Frédéric; Licul, Aleksandar
2016-04-01
With the end of the Last Glacial Maximum (LGM), about 20 000 years ago, ended the most recent long-lasting cold phase in Earth's history. We recently developed a model that describes large-scale erosion and its response to climate and dynamical changes with the application to the Alps for the LGM period. Here we will present an inverse approach we have recently developed to infer the LGM mass balance from known ice extent data, focusing on a glacier or ice cap. The ice flow model is developed using the shallow ice approximation and the developed codes are accelerated using GPUs capabilities. The mass balance field is the constrained variable defined by the balance rate β and the equilibrium line altitude (ELA), where c is the cutoff value: b = max(βṡ(S(z) - ELA), c) We show that such a mass balance can be constrained from the observed past ice extent and ice thickness. We are also investigating several different geostatistical methods to constrain spatially variable mass balance, and derive uncertainties on each of the mass balance parameters.
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Antarctic and Greenland ice sheet mass balance products from satellite gravimetry
NASA Astrophysics Data System (ADS)
Horwath, Martin; Groh, Andreas; Horvath, Alexander; Forsberg, René; Meister, Rakia; Barletta, Valentina R.; Shepherd, Andrew
2017-04-01
Because of their important role in the Earth's climate system, ESA's Climate Change Initiative (CCI) has identified both the Antarctic Ice Sheet (AIS) and the Greenland Ice Sheet (GIS) as Essential Climate Variables (ECV). Since respondents of a user survey indicated that the ice sheet mass balance is one of the most important ECV data products needed to better understand climate change, the AIS_cci and the GIS_cci project provide Gravimetric Mass Balance (GMB) products based on satellite gravimetry data. The GMB products are derived from GRACE (Gravity Recovery and Climate Experiment) monthly solutions of release ITSG-Grace2016 produced at TU Graz. GMB basin products (i.e. time series of monthly mass changes for the entire ice sheets and selected drainage basins) and GMB gridded products (e.g. mass balance estimates with a formal resolution of about 50km, covering the entire ice sheets) are generated for the period from 2002 until present. The first GMB product was released in mid 2016. Here we present an extended and updated version of the ESA CCI GMB products, which are freely available through data portals hosted by the projects (https://data1.geo.tu-dresden.de/ais_gmb, http://products.esa-icesheets-cci.org/products/downloadlist/GMB). Since the initial product release, the applied processing strategies have been improved in order to further reduce GRACE errors and to enhance the separation of signals super-imposed to the ice mass changes. While a regional integration approach is used by the AIS_cci project, the GMB products of the GIS_cci project are derived using a point mass inversion. The differences between both approaches are investigated through the example of the GIS, where an alternative GMB product was generated using the regional integration approach implemented by the AIS_cci. Finally, we present the latest mass balance estimates for both ice sheets as well as their corresponding contributions to global sea level rise.
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Antarctic Ice-Sheet Mass Balance from Satellite Altimetry 1992 to 2001
NASA Technical Reports Server (NTRS)
Zwally, H. Jay; Brenner, Anita C.; Cornejo, Helen; Giovinetto, Mario; Saba, Jack L.; Yi, Donghui
2003-01-01
A major uncertainty in understanding the causes of the current rate of sea level rise is the potential contributions from mass imbalances of the Greenland and Antarctic ice sheets. Estimates of the current mass balance of the Antarctic ice sheet are derived from surface- elevation changes obtained from 9 years of ERS - 1 & 2 radar altimeter data. Elevation time-series are created from altimeter crossovers among 90-day data periods on a 50 km grid to 81.5 S. The time series are fit with a multivariate linear/sinusoidal function to give the average rate of elevation change (dH/dt). On the major Rome-Filchner, Ross, and Amery ice shelves, the W d t are small or near zero. In contrast, the ice shelves of the Antarctic Peninsula and along the West Antarctic coast appear to be thinning significantly, with a 23 +/- 3 cm per year surface elevation decrease on the Larsen ice shelf and a 65 +/- 4 cm per year decrease on the Dotson ice shelf. On the grounded ice, significant elevation decreases are obtained over most of the drainage basins of the Pine Island and Thwaites glaciers in West Antarctica and inland of Law Dome in East Antarctica. Significant elevation increases are observed within about 200 km of the coast around much of the rest of the ice sheet. Farther inland, the changes are a mixed pattern of increases and decreases with increases of a few centimeters per year at the highest elevations of the East Antarctic plateau. The derived elevation changes are combined with estimates of the bedrock uplift from several models to provide maps of ice thickness change. The ice thickness changes enable estimates of the ice mass balances for the major drainage basins, the overall mass balance, and the current contribution of the ice sheet to global sea level change.
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Surface mass balance contributions to acceleration of Antarctic ice mass loss during 2003-2013
NASA Astrophysics Data System (ADS)
Seo, Ki-Weon; Wilson, Clark R.; Scambos, Ted; Kim, Baek-Min; Waliser, Duane E.; Tian, Baijun; Kim, Byeong-Hoon; Eom, Jooyoung
2015-05-01
Recent observations from satellite gravimetry (the Gravity Recovery and Climate Experiment (GRACE) mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies. However, on the Antarctic Peninsula and other parts of West Antarctica, mass changes are not explained by precipitation and are likely associated with ice discharge rate increases. The total apparent GRACE acceleration over all of the AIS between 2003 and 2013 is -13.6 ± 7.2 Gt/yr2. Of this total, we find that the surface mass balance component is -8.2 ± 2.0 Gt/yr2. However, the GRACE estimate appears to contain errors arising from the atmospheric pressure fields used to remove air mass effects. The estimated acceleration error from this effect is about 9.8 ± 5.8 Gt/yr2. Correcting for this yields an ice discharge acceleration of -15.1 ± 6.5 Gt/yr2.
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Surface Mass Balance Contributions to Acceleration of Antarctic Ice Mass Loss during 2003- 2013
NASA Astrophysics Data System (ADS)
Seo, K. W.; Wilson, C. R.; Scambos, T. A.; Kim, B. M.; Waliser, D. E.; Tian, B.; Kim, B.; Eom, J.
2015-12-01
Recent observations from satellite gravimetry (the GRACE mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies. However, on the Antarctic Peninsula and other parts of West Antarctica mass changes are not explained by precipitation and are likely associated with ice discharge rate increases. The total apparent GRACE acceleration over all of the AIS between 2003 and 2013 is -13.6±7.2 GTon/yr2. Of this total, we find that the surface mass balance component is -8.2±2.0 GTon/yr2. However, the GRACE estimate appears to contain errors arising from the atmospheric pressure fields used to remove air mass effects. The estimated acceleration error from this effect is about 9.8±5.8 GTon/yr2. Correcting for this yields an ice discharge acceleration of -15.1±6.5 GTon/yr2.
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Improving Estimates of Greenland Ice Sheet Surface Mass Balance with Satellite Observations
NASA Astrophysics Data System (ADS)
Briggs, K.
2016-12-01
Mass losses from the Greenland Ice Sheet have been accelerating over recent years (e.g. McMillan et al., 2016; Velicogna et al., 2014). This acceleration has predominantly been linked to increasing rates of negative surface mass balance, and in particular, increasing ice surface melt rates (e.g. McMillan et al., 2016; Velicogna et al., 2014). At the ice sheet scale, SMB is assessed using SMB model outputs, which in addition to enabling understanding of the origin of mass balance signals, are required as ancillary data in mass balance assessments from altimetry and the mass budget method. Due to the importance of SMB for mass balance over Greenland and the sensitivity of mass balance assessments to SMB model outputs, high accuracy of these models is crucial. A critical limiting factor in SMB modeling is however, a lack of in-situ data that is required for model constraint and evaluation. Such data is limited in time and space due to inherent logistical and financial constraints. Remote sensing datasets, being spatially extensive and relatively densely sampled in both space and time, do not suffer such constraints. Here, we show satellite observations of Greenland SMB. McMillan, M., Leeson, A., Shepherd, A., Briggs, K., Armitage, T. W.K., Hogg, A., Kuipers Munneke, P., van den Broeke, M., Noël, B., van de Berg, W., Ligtenberg, S., Horwath, M., Groh, A. , Muir, A. and Gilbert, L. 2016. A high resolution record of Greenland Mass Balance. Geophysical Research Letters. 43, doi:10.1002/2016GL069666 Velicogna, I., Sutterley, T. C. and van den Broeke, M. R. 2014. Regional acceleration in ice mass loss from Greenland and Antarctica using GRACE time-variable gravity data. Geophysical Research Letters. 41, 8130-8137, doi:10.1002/2014GL061052
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Surface mass balance of Greenland mountain glaciers and ice caps
NASA Astrophysics Data System (ADS)
Benson, R. J.; Box, J. E.; Bromwich, D. H.; Wahr, J. M.
2009-12-01
Mountain glaciers and ice caps contribute roughly half of eustatic sea-level rise. Greenland has thousands of small mountain glaciers and several ice caps > 1000 sq. km that have not been included in previous mass balance calculations. To include small glaciers and ice caps in our study, we use Polar WRF, a next-generation regional climate data assimilation model is run at grid resolution less than 10 km. WRF provides surface mass balance data at sufficiently high resolution to resolve not only the narrow ice sheet ablation zone, but provides information useful in downscaling melt and accumulation rates on mountain glaciers and ice caps. In this study, we refine Polar WRF to simulate a realistic surface energy budget. Surface melting is calculated in-line from surface energy budget closure. Blowing snow sublimation is computed in-line. Melt water re-freeze is calculated using a revised scheme. Our results are compared with NASA's Gravity Recovery and Climate Experiment (GRACE) and associated error is calculated on a regional and local scale with validation from automated weather stations (AWS), snow pits and ice core data from various regions along the Greenland ice sheet.
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NASA Astrophysics Data System (ADS)
Rodehacke, C. B.; Mottram, R.; Boberg, F.
2017-12-01
The Devon Ice Cap is an example of a relatively well monitored small ice cap in the Canadian Arctic. Close to Greenland, it shows a similar surface mass balance signal to glaciers in western Greenland. Here we various boundary conditions, ranging from ERA-Interim reanalysis data via global climate model high resolution (5km) output from the regional climate model HIRHAM5, to determine the surface mass balance of the Devon ice cap. These SMB estimates are used to drive the PISM glacier model in order to model the present day and future prospects of this small Arctic ice cap. Observational data from the Devon Ice Cap in Arctic Canada is used to evaluate the surface mass balance (SMB) data output from the HIRHAM5 model for simulations forced with the ERA-Interim climate reanalysis data and the historical emissions scenario run by the EC-Earth global climate model. The RCP8.5 scenario simulated by EC-Earth is also downscaled by HIRHAM5 and this output is used to force the PISM model to simulate the likely future evolution of the Devon Ice Cap under a warming climate. We find that the Devon Ice Cap is likely to continue its present day retreat, though in the future increased precipitation partly offsets the enhanced melt rates caused by climate change.
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Surface mass balance contributions to acceleration of Antarctic ice mass loss during 2003-2013.
Seo, Ki-Weon; Wilson, Clark R; Scambos, Ted; Kim, Baek-Min; Waliser, Duane E; Tian, Baijun; Kim, Byeong-Hoon; Eom, Jooyoung
2015-05-01
Recent observations from satellite gravimetry (the Gravity Recovery and Climate Experiment (GRACE) mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies. However, on the Antarctic Peninsula and other parts of West Antarctica, mass changes are not explained by precipitation and are likely associated with ice discharge rate increases. The total apparent GRACE acceleration over all of the AIS between 2003 and 2013 is -13.6 ± 7.2 Gt/yr 2 . Of this total, we find that the surface mass balance component is -8.2 ± 2.0 Gt/yr 2 . However, the GRACE estimate appears to contain errors arising from the atmospheric pressure fields used to remove air mass effects. The estimated acceleration error from this effect is about 9.8 ± 5.8 Gt/yr 2 . Correcting for this yields an ice discharge acceleration of -15.1 ± 6.5 Gt/yr 2 .
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Dual-sensor mapping of mass balance on Russia's northernmost ice caps
NASA Astrophysics Data System (ADS)
Nikolskiy, D.; Malinnikov, V.; Sharov, A.; Ukolova, M.
2012-04-01
Mass balance of Russia's northernmost ice caps is poorly known and scarcely mapped. Thorough information about glacier fluctuations in the outer periphery of Russian shelf seas is both lacking and highly desired since it may constitute the relevant benchmark for judging and projecting climate change impacts in the entire Arctic. The present study is focussed on geodetic measurements and medium-scale mapping of the mass balance on a dozen insular ice caps, some large and some smaller, homogeneously situated along the Eurasian boundary of Central Arctic Basin. The study region extends for approx. 2.200 km from Victoria and Arthur islands in the west across Rudolph, Eva-Liv, Ushakova, Schmidt and Komsomolets islands in the north to Bennett and Henrietta islands in the east thereby comprising the most distant and least studied ice caps in the Russian Arctic. The situation of insular ice masses close to the edge of summer minimum sea ice proved helpful in analysing spatial asymmetry of glacier accumulation signal. The overall mapping of glacier elevation changes and quantification of mass balance characteristics in the study region was performed by comparing reference elevation models of study glaciers derived from Russian topographic maps 1:200,000 (CI = 20 or 40 m) representing the glacier state as in the 1950s-1960s with modern elevation data obtained from satellite radar interferometry and lidar altimetry. In total, 14 ERS and 4 TanDEM-X high-quality SAR interferograms of 1995/96 and 2011 were acquired, processed in the standard 2-pass DINSAR manner, geocoded, calibrated, mosaicked and interpreted using reference elevation models and co-located ICESat altimetry data of 2003-2010. The DINSAR analysis revealed the existence of fast-flowing outlet glaciers at Arthur, Rudolph, Eva-Liv and Bennett islands. The calculation of separate mass-balance components is complicated in this case because of generally unknown glacier velocities and ice discharge values for the mid-20
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The Greenland Ice Sheet's surface mass balance in a seasonally sea ice-free Arctic
NASA Astrophysics Data System (ADS)
Day, J. J.; Bamber, J. L.; Valdes, P. J.
2013-09-01
General circulation models predict a rapid decrease in sea ice extent with concurrent increases in near-surface air temperature and precipitation in the Arctic over the 21st century. This has led to suggestions that some Arctic land ice masses may experience an increase in accumulation due to enhanced evaporation from a seasonally sea ice-free Arctic Ocean. To investigate the impact of this phenomenon on Greenland Ice Sheet climate and surface mass balance (SMB), a regional climate model, HadRM3, was used to force an insolation-temperature melt SMB model. A set of experiments designed to investigate the role of sea ice independently from sea surface temperature (SST) forcing are described. In the warmer and wetter SI + SST simulation, Greenland experiences a 23% increase in winter SMB but 65% reduced summer SMB, resulting in a net decrease in the annual value. This study shows that sea ice decline contributes to the increased winter balance, causing 25% of the increase in winter accumulation; this is largest in eastern Greenland as the result of increased evaporation in the Greenland Sea. These results indicate that the seasonal cycle of Greenland's SMB will increase dramatically as global temperatures increase, with the largest changes in temperature and precipitation occurring in winter. This demonstrates that the accurate prediction of changes in sea ice cover is important for predicting Greenland SMB and ice sheet evolution.
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NASA Astrophysics Data System (ADS)
Grima, C.; Koch, I.; Greenbaum, J. S.; Soderlund, K. M.; Blankenship, D. D.; Young, D. A.; Fitzsimons, S.
2017-12-01
The McMurdo ice shelves (northern and southern MIS), adjacent to the eponymous station and the Ross Ice Shelf, Antarctica, are known for large gradients in surface snow accumulation and snow/ice impurities. Marine ice accretion and melting are important contributors to MIS's mass balance. Due to erosive winds, the southern MIS (SMIS) shows a locally negative surface mass balance. Thus, marine ice once accreted at the ice shelf base crops out at the surface. However, the exact processes that exert primary control on SMIS mass balance have remained elusive. Radar statistical reconnaissance (RSR) is a recent technique that has been used to characterize the surface properties of the Earth's cryosphere, Mars, and Titan from the stochastic character of energy scattered by the surface. Here, we apply RSR to map the surface density and roughness of the SMIS and extend the technique to derive the basal reflectance and scattering coefficients of the ice-ocean interface. We use an airborne radar survey grid acquired over the SMIS in the 2014-2015 austral summer by the University of Texas Institute for Geophysics with the High Capability Radar Sounder (HiCARS2; 60-MHz center frequency and 15-MHz bandwidth). The RSR-derived snow density values and patterns agree with directly -measured ice shelf surface accumulation rates. We also compare the composition of SMIS ice surface samples to test the ability of RSR to discriminate ices with varying dielectric properties (e.g., marine versus meteoric ice) and hypothesize relationships between the RSR-derived basal reflectance/scattered coefficients and accretion or melting at the ice-ocean interface. This improved knowledge of air-ice and ice-ocean boundaries provides a new perspective on the processes governing SMIS surface and basal mass balance.
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Mass Balance of the West Antarctic Ice-Sheet from ICESat Measurements
NASA Technical Reports Server (NTRS)
Zwally, H. Jay; Li, Jun; Robins, John; Saba, Jack L.; Yi, Donghui
2011-01-01
Mass balance estimates for 2003-2008 are derived from ICESat laser altimetry and compared with estimates for 1992-2002 derived from ERS radar altimetry. The net mass balance of 3 drainage systems (Pine Island, Thwaites/Smith, and the coast of Marie Bryd) for 2003-2008 is a loss of 100 Gt/yr, which increased from a loss of 70 Gt/yr for the earlier period. The DS including the Bindschadler and MacAyeal ice streams draining into the Ross Ice Shelf has a mass gain of 11 Gt/yr for 2003-2008, compared to an earlier loss of 70 Gt/yr. The DS including the Whillans and Kamb ice streams has a mass gain of 12 Gt/yr, including a significant thickening on the upper part of the Kamb DS, compared to a earlier gain of 6 Gt/yr (includes interpolation for a large portion of the DS). The other two DS discharging into the Ronne Ice Shelf and the northern Ellsworth Coast have a mass gain of 39 Gt/yr, compared to a gain of 4 Gt/yr for the earlier period. Overall, the increased losses of 30 Gt/yr in the Pine Island, Thwaites/Smith, and the coast of Marie Bryd DSs are exceeded by increased gains of 59 Gt/yr in the other 4 DS. Overall, the mass loss from the West Antarctic ice sheet has decreased to 38 Gt/yr from the earlier loss of 67 Gt/yr, reducing the contribution to sea level rise to 0.11 mm/yr from 0.19 mm/yr
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Surface Mass Balance of the Greenland Ice Sheet Derived from Paleoclimate Reanalysis
NASA Astrophysics Data System (ADS)
Badgeley, J.; Steig, E. J.; Hakim, G. J.; Anderson, J.; Tardif, R.
2017-12-01
Modeling past ice-sheet behavior requires independent knowledge of past surface mass balance. Though models provide useful insight into ice-sheet response to climate forcing, if past climate is unknown, then ascertaining the rate and extent of past ice-sheet change is limited to geological and geophysical constraints. We use a novel data-assimilation framework developed under the Last Millennium Reanalysis Project (Hakim et al., 2016) to reconstruct past climate over ice sheets with the intent of creating an independent surface mass balance record for paleo ice-sheet modeling. Paleoclimate data assimilation combines the physics of climate models and the time series evidence of proxy records in an offline, ensemble-based approach. This framework allows for the assimilation of numerous proxy records and archive types while maintaining spatial consistency with known climate dynamics and physics captured by the models. In our reconstruction, we use the Community Climate System Model version 4, CMIP5 last millennium simulation (Taylor et al., 2012; Landrum et al., 2013) and a nearly complete database of ice core oxygen isotope records to reconstruct Holocene surface temperature and precipitation over the Greenland Ice Sheet on a decadal timescale. By applying a seasonality to this reconstruction (from the TraCE-21ka simulation; Liu et al., 2009), our reanalysis can be used in seasonally-based surface mass balance models. Here we discuss the methods behind our reanalysis and the performance of our reconstruction through prediction of unassimilated proxy records and comparison to paleoclimate reconstructions and reanalysis products.
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NASA Astrophysics Data System (ADS)
Berger, Sophie; Drews, Reinhard; Helm, Veit; Sun, Sainan; Pattyn, Frank
2017-11-01
Ice shelves control the dynamic mass loss of ice sheets through buttressing and their integrity depends on the spatial variability of their basal mass balance (BMB), i.e. the difference between refreezing and melting. Here, we present an improved technique - based on satellite observations - to capture the small-scale variability in the BMB of ice shelves. As a case study, we apply the methodology to the Roi Baudouin Ice Shelf, Dronning Maud Land, East Antarctica, and derive its yearly averaged BMB at 10 m horizontal gridding. We use mass conservation in a Lagrangian framework based on high-resolution surface velocities, atmospheric-model surface mass balance and hydrostatic ice-thickness fields (derived from TanDEM-X surface elevation). Spatial derivatives are implemented using the total-variation differentiation, which preserves abrupt changes in flow velocities and their spatial gradients. Such changes may reflect a dynamic response to localized basal melting and should be included in the mass budget. Our BMB field exhibits much spatial detail and ranges from -14.7 to 8.6 m a-1 ice equivalent. Highest melt rates are found close to the grounding line where the pressure melting point is high, and the ice shelf slope is steep. The BMB field agrees well with on-site measurements from phase-sensitive radar, although independent radar profiling indicates unresolved spatial variations in firn density. We show that an elliptical surface depression (10 m deep and with an extent of 0.7 km × 1.3 km) lowers by 0.5 to 1.4 m a-1, which we tentatively attribute to a transient adaptation to hydrostatic equilibrium. We find evidence for elevated melting beneath ice shelf channels (with melting being concentrated on the channel's flanks). However, farther downstream from the grounding line, the majority of ice shelf channels advect passively (i.e. no melting nor refreezing) toward the ice shelf front. Although the absolute, satellite-based BMB values remain uncertain, we have
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Radar Interferometry Studies of the Mass Balance of Polar Ice Sheets
NASA Technical Reports Server (NTRS)
Rignot, Eric (Editor)
1999-01-01
The objectives of this work are to determine the current state of mass balance of the Greenland and Antarctic Ice Sheets. Our approach combines different techniques, which include satellite synthetic-aperture radar interferometry (InSAR), radar and laser altimetry, radar ice sounding, and finite-element modeling. In Greenland, we found that 3.5 times more ice flows out of the northern part of the Greenland Ice Sheet than previously accounted for. The discrepancy between current and past estimates is explained by extensive basal melting of the glacier floating sections in the proximity of the grounding line where the glacier detaches from its bed and becomes afloat in the ocean. The inferred basal melt rates are very large, which means that the glaciers are very sensitive to changes in ocean conditions. Currently, it appears that the northern Greenland glaciers discharge more ice than is being accumulated in the deep interior, and hence are thinning. Studies of temporal changes in grounding line position using InSAR confirm the state of retreat of northern glaciers and suggest that thinning is concentrated at the lower elevations. Ongoing work along the coast of East Greenland reveals an even larger mass deficit for eastern Greenland glaciers, with thinning affecting the deep interior of the ice sheet. In Antarctica, we found that glaciers flowing into a large ice shelf system, such as the Ronne Ice Shelf in the Weddell Sea, exhibit an ice discharge in remarkable agreement with mass accumulation in the interior, and the glacier grounding line positions do not migrate with time. Glaciers flowing rapidly into the Amudsen Sea, unrestrained by a major ice shelf, are in contrast discharging more ice than required to maintain a state of mass balance and are thinning quite rapidly near the coast. The grounding line of Pine Island glacier (see diagram) retreated 5 km in 4 years, which corresponds to a glacier thinning rate of 3.5 m/yr. Mass imbalance is even more negative
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NASA Astrophysics Data System (ADS)
Villamil-Otero, G.; Zhang, J.; Yao, Y.
2017-12-01
The Antarctic Peninsula (AP) has long been the focus of climate change studies due to its rapid environmental changes such as significantly increased glacier melt and retreat, and ice-shelf break-up. Progress has been continuously made in the use of regional modeling to simulate surface mass changes over ice sheets. Most efforts, however, focus on the ice sheets of Greenland with considerable fewer studies in Antarctica. In this study the Weather Research and Forecasting (WRF) model, which has been applied to the Antarctic region for weather modeling, is adopted to capture the past and future surface mass balance changes over AP. In order to enhance the capabilities of WRF model simulating surface mass balance over the ice surface, we implement various ice and snow processes within the WRF and develop a new WRF suite (WRF-Ice). The WRF-Ice includes a thermodynamic ice sheet model that improves the representation of internal melting and refreezing processes and the thermodynamic effects over ice sheet. WRF-Ice also couples a thermodynamic sea ice model to improve the simulation of surface temperature and fluxes over sea ice. Lastly, complex snow processes are also taken into consideration including the implementation of a snowdrift model that takes into account the redistribution of blowing snow as well as the thermodynamic impact of drifting snow sublimation on the lower atmospheric boundary layer. Intensive testing of these ice and snow processes are performed to assess the capability of WRF-Ice in simulating the surface mass balance changes over AP.
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NASA Astrophysics Data System (ADS)
Schäfer, Martina; Möller, Marco; Zwinger, Thomas; Moore, John
2016-04-01
Using a coupled simulation set-up between a by statistical climate data forced and to ice-cap resolution downscaled mass balance model and an ice-dynamic model, we study coupling effects for the Vestfonna ice cap, Nordaustlandet, Svalbard, by analysing the impacts of different imposed coupling intervals on mass-balance and sea-level rise (SLR) projections. Based on a method to estimate errors introduced by different coupling schemes, we find that neglecting the topographic feedback in the coupling leads to underestimations of 10-20% in SLR projections on century time-scales in our model compared to full coupling (i.e., exchange of properties using smallest occurring time-step). Using the same method it also is shown that parametrising mass-balance adjustment for changes in topography using lapse rates is a - in computational terms - cost-effective reasonably accurate alternative applied to an ice-cap like Vestfonna. We test the forcing imposed by different emission pathways (RCP 2.4, 4.5, 6.0 and 8.5). For most of them, over the time-period explored (2000-2100), fast-flowing outlet glaciers decrease in impacting SLR due to their deceleration and reduced mass flux as they thin and retreat from the coast, hence detaching from the ocean and thereby losing their major mass drainage mechanism, i.e., calving.
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Surface Energy and Mass Balance Model for Greenland Ice Sheet and Future Projections
NASA Astrophysics Data System (ADS)
Liu, Xiaojian
The Greenland Ice Sheet contains nearly 3 million cubic kilometers of glacial ice. If the entire ice sheet completely melted, sea level would raise by nearly 7 meters. There is thus considerable interest in monitoring the mass balance of the Greenland Ice Sheet. Each year, the ice sheet gains ice from snowfall and loses ice through iceberg calving and surface melting. In this thesis, we develop, validate and apply a physics based numerical model to estimate current and future surface mass balance of the Greenland Ice Sheet. The numerical model consists of a coupled surface energy balance and englacial model that is simple enough that it can be used for long time scale model runs, but unlike previous empirical parameterizations, has a physical basis. The surface energy balance model predicts ice sheet surface temperature and melt production. The englacial model predicts the evolution of temperature and meltwater within the ice sheet. These two models can be combined with estimates of precipitation (snowfall) to estimate the mass balance over the Greenland Ice Sheet. We first compare model performance with in-situ observations to demonstrate that the model works well. We next evaluate how predictions are degraded when we statistically downscale global climate data. We find that a simple, nearest neighbor interpolation scheme with a lapse rate correction is able to adequately reproduce melt patterns on the Greenland Ice Sheet. These results are comparable to those obtained using empirical Positive Degree Day (PDD) methods. Having validated the model, we next drove the ice sheet model using the suite of atmospheric model runs available through the CMIP5 atmospheric model inter-comparison, which in turn built upon the RCP 8.5 (business as usual) scenarios. From this exercise we predict how much surface melt production will increase in the coming century. This results in 4-10 cm sea level equivalent, depending on the CMIP5 models. Finally, we try to bound melt water
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NASA Astrophysics Data System (ADS)
Wilson, Nat; Straneo, Fiammetta; Heimbach, Patrick
2017-12-01
Ice-shelf-like floating extensions at the termini of Greenland glaciers are undergoing rapid changes with potential implications for the stability of upstream glaciers and the ice sheet as a whole. While submarine melting is recognized as a major contributor to mass loss, the spatial distribution of submarine melting and its contribution to the total mass balance of these floating extensions is incompletely known and understood. Here, we use high-resolution WorldView satellite imagery collected between 2011 and 2015 to infer the magnitude and spatial variability of melt rates under Greenland's largest remaining ice tongues - Nioghalvfjerdsbræ (79 North Glacier, 79N), Ryder Glacier (RG), and Petermann Glacier (PG). Submarine melt rates under the ice tongues vary considerably, exceeding 50 m a-1 near the grounding zone and decaying rapidly downstream. Channels, likely originating from upstream subglacial channels, give rise to large melt variations across the ice tongues. We compare the total melt rates to the influx of ice to the ice tongue to assess their contribution to the current mass balance. At Petermann Glacier and Ryder Glacier, we find that the combined submarine and aerial melt approximately balances the ice flux from the grounded ice sheet. At Nioghalvfjerdsbræ the total melt flux (14.2 ± 0.96 km3 a-1 w.e., water equivalent) exceeds the inflow of ice (10.2 ± 0.59 km3 a-1 w.e.), indicating present thinning of the ice tongue.
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Balance Mass Flux and Velocity Across the Equilibrium Line in Ice Drainage Systems of Greenland
NASA Technical Reports Server (NTRS)
Zwally, H. Jay; Giovinetto, Mario B.; Koblinsky, Chester J. (Technical Monitor)
2001-01-01
Estimates of balance mass flux and the depth-averaged ice velocity through the cross-section aligned with the equilibrium line are produced for each of six drainage systems in Greenland. (The equilibrium line, which lies at approximately 1200 m elevation on the ice sheet, is the boundary between the area of net snow accumulation at higher elevations and the areas of net melting at lower elevations around the ice sheet.) Ice drainage divides and six major drainage systems are delineated using surface topography from ERS (European Remote Sensing) radar altimeter data. The net accumulation rate in the accumulation zone bounded by the equilibrium line is 399 Gt/yr and net ablation rate in the remaining area is 231 Gt/yr. (1 GigaTon of ice is 1090 kM(exp 3). The mean balance mass flux and depth-averaged ice velocity at the cross-section aligned with the modeled equilibrium line are 0.1011 Gt kM(exp -2)/yr and 0.111 km/yr, respectively, with little variation in these values from system to system. The ratio of the ice mass above the equilibrium line to the rate of mass output implies an effective exchange time of approximately 6000 years for total mass exchange. The range of exchange times, from a low of 3 ka in the SE drainage system to 14 ka in the NE, suggests a rank as to which regions of the ice sheet may respond more rapidly to climate fluctuations.
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Mass balance of the Antarctic ice sheet.
Wingham, D J; Shepherd, A; Muir, A; Marshall, G J
2006-07-15
The Antarctic contribution to sea-level rise has long been uncertain. While regional variability in ice dynamics has been revealed, a picture of mass changes throughout the continental ice sheet is lacking. Here, we use satellite radar altimetry to measure the elevation change of 72% of the grounded ice sheet during the period 1992-2003. Depending on the density of the snow giving rise to the observed elevation fluctuations, the ice sheet mass trend falls in the range -5-+85Gtyr-1. We find that data from climate model reanalyses are not able to characterise the contemporary snowfall fluctuation with useful accuracy and our best estimate of the overall mass trend-growth of 27+/-29Gtyr-1-is based on an assessment of the expected snowfall variability. Mass gains from accumulating snow, particularly on the Antarctic Peninsula and within East Antarctica, exceed the ice dynamic mass loss from West Antarctica. The result exacerbates the difficulty of explaining twentieth century sea-level rise.
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A Range Correction for Icesat and Its Potential Impact on Ice-sheet Mass Balance Studies
NASA Technical Reports Server (NTRS)
Borsa, A. A.; Moholdt, G.; Fricker, H. A.; Brunt, Kelly M.
2014-01-01
We report on a previously undocumented range error in NASA's Ice, Cloud and land Elevation Satellite (ICESat) that degrades elevation precision and introduces a small but significant elevation trend over the ICESat mission period. This range error (the Gaussian-Centroid or 'G-C'offset) varies on a shot-to-shot basis and exhibits increasing scatter when laser transmit energies fall below 20 mJ. Although the G-C offset is uncorrelated over periods less than1 day, it evolves over the life of each of ICESat's three lasers in a series of ramps and jumps that give rise to spurious elevation trends of -0.92 to -1.90 cm yr(exp -1), depending on the time period considered. Using ICESat data over the Ross and Filchner-Ronne ice shelves we show that (1) the G-C offset introduces significant biases in ice-shelf mass balance estimates, and (2) the mass balance bias can vary between regions because of different temporal samplings of ICESat.We can reproduce the effect of the G-C offset over these two ice shelves by fitting trends to sample-weighted mean G-C offsets for each campaign, suggesting that it may not be necessary to fully repeat earlier ICESat studies to determine the impact of the G-C offset on ice-sheet mass balance estimates.
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Snow contribution to first-year and second-year Arctic sea ice mass balance north of Svalbard
NASA Astrophysics Data System (ADS)
Granskog, Mats A.; Rösel, Anja; Dodd, Paul A.; Divine, Dmitry; Gerland, Sebastian; Martma, Tõnu; Leng, Melanie J.
2017-03-01
The salinity and water oxygen isotope composition (δ18O) of 29 first-year (FYI) and second-year (SYI) Arctic sea ice cores (total length 32.0 m) from the drifting ice pack north of Svalbard were examined to quantify the contribution of snow to sea ice mass. Five cores (total length 6.4 m) were analyzed for their structural composition, showing variable contribution of 10-30% by granular ice. In these cores, snow had been entrained in 6-28% of the total ice thickness. We found evidence of snow contribution in about three quarters of the sea ice cores, when surface granular layers had very low δ18O values. Snow contributed 7.5-9.7% to sea ice mass balance on average (including also cores with no snow) based on δ18O mass balance calculations. In SYI cores, snow fraction by mass (12.7-16.3%) was much higher than in FYI cores (3.3-4.4%), while the bulk salinity of FYI (4.9) was distinctively higher than for SYI (2.7). We conclude that oxygen isotopes and salinity profiles can give information on the age of the ice and enables distinction between FYI and SYI (or older) ice in the area north of Svalbard.
Plain Language SummaryThe role of snow in sea <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> is largely two fold. Firstly, it can slow down growth and melt due to its high insulation and high reflectance, but secondly it can actually contribute to sea <span class="hlt">ice</span> growth if the snow cover is turned into <span class="hlt">ice</span>. The latter is largely a consequence of high <span class="hlt">mass</span> of snow on top of sea <span class="hlt">ice</span> that can push the surface of the sea <span class="hlt">ice</span> below sea level and seawater can flood the <span class="hlt">ice</span>. This mixture of seawater and snow can then freeze and add to the growth of sea <span class="hlt">ice</span>. This is very typical in the Antarctic but not believed to be so important in the Arctic. In this work we show, for the first time, that snow actually contributes significantly to the growth of Arctic sea <span class="hlt">ice</span>. This is likely a consequence of the thinning of the Arctic sea <span class="hlt">ice</span>. The conditions in the Arctic, with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33D1227B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33D1227B"><span>Modelling the contribution of supraglacial <span class="hlt">ice</span> cliffs to the <span class="hlt">mass-balance</span> of glaciers in the Langtang catchment, Nepalese Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buri, P.; Steiner, J. F.; Miles, E.; Ragettli, S.; Pellicciotti, F.</p> <p>2017-12-01</p> <p>Supraglacial cliffs are typical surface features of debris-covered glaciers worldwide, affecting surface evolution, and <span class="hlt">mass</span> <span class="hlt">balance</span> by providing a direct <span class="hlt">ice</span>-atmosphere interface where melt rates can be very high. As a result, <span class="hlt">ice</span> cliffs act as windows of energy transfer from the atmosphere to the <span class="hlt">ice</span>, and enhance melt and <span class="hlt">mass</span> losses of otherwise insulated <span class="hlt">ice</span>. However, their contribution to glacier <span class="hlt">mass</span> <span class="hlt">balance</span> has never been quantified at the glacier scale, and all inference has been obtained from upscaling results of point-scale models or observations at select individual cliffs. Here we use a 3D, physically-based backwasting model to estimate the volume losses associated with the melting and backwasting of supraglacial <span class="hlt">ice</span> cliffs for the entire debris-covered glacier area of the Langtang catchment. We estimate <span class="hlt">mass</span> losses for the 2014 melt season and compare them to recent values of glacier <span class="hlt">mass</span> <span class="hlt">balance</span> determined from geodetic and numerical modelling approached. Cliff outlines and topography are derived from high-resolution stereo SPOT6-imagery from April 2014. Meteorological data to force the model are provided by automatic weather stations on- and off-glacier within the valley. The model simulates <span class="hlt">ice</span> cliff backwasting by considering the cliff-atmosphere energy-<span class="hlt">balance</span>, reburial by debris and the effects of adjacent ponds. In the melt season of 2014, cliffs' distribution and patterns of <span class="hlt">mass</span> losses vary considerably from glacier to glacier, and we relate rates of volume loss to both glaciers' and cliffs' characteristics. Only cliffs with a northerly aspect account for substantial losses. Uncertainty in our estimates is due to the quality of the stereo DEM, uncertainties in the cliff delineation and the fact that we use a conservative approach to cliff delineation and discard very small cliffs and those for which uncertainty in topography is high. Despite these uncertainties, our work presents the first estimate of the importance of supraglacial <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C33D..05V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C33D..05V"><span>Improved estimate of accelerated Antarctica <span class="hlt">ice</span> <span class="hlt">mass</span> loses from GRACE, Altimetry and surface <span class="hlt">mass</span> <span class="hlt">balance</span> from regional climate model output</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Velicogna, I.; Sutterley, T. C.; A, G.; van den Broeke, M. R.; Ivins, E. R.</p> <p>2016-12-01</p> <p>We use Gravity Recovery and Climate Experiment (GRACE) monthly gravity fields to determine the regional acceleration in <span class="hlt">ice</span> <span class="hlt">mass</span> loss in Antarctica for 2002-2016. We find that the total <span class="hlt">mass</span> loss is controlled by only a few regions. In Antarctica, the Amundsen Sea (AS) sector and the Antarctic Peninsula account for 65% and 18%, respectively, of the total loss (186 ± 10 Gt/yr) mainly from <span class="hlt">ice</span> dynamics. The AS sector contributes most of the acceleration in loss (9 ± 1 Gt/yr2 ), and Queen Maud Land, East Antarctica, is the only sector with a significant <span class="hlt">mass</span> gain due to a local increase in SMB (57 ± 5 Gt/yr). We compare GRACE regional <span class="hlt">mass</span> <span class="hlt">balance</span> estimates with independent estimates from ICESat-1 and Operation <span class="hlt">Ice</span>Bridge laser altimetry, CryoSat-2 radar altimetry, and surface <span class="hlt">mass</span> <span class="hlt">balance</span> outputs from RACMO2.3. In the Amundsen Sea Embayment of West Antarctica, an area experiencing rapid retreat and <span class="hlt">mass</span> loss to the sea, we find good agreement between GRACE and altimetry estimates. Comparison of GRACE with these independent techniques in East Antarctic shows that GIA estimates from the new regional <span class="hlt">ice</span> deglaciation models underestimate the GIA correction in the EAIS interior, which implies larger losses of the Antarctica <span class="hlt">ice</span> sheet by about 70 Gt/yr. Sectors where we are observing the largest losses are closest to warm circumpolar water, and with polar constriction of the westerlies enhanced by climate warming, we expect these sectors to contribute more and more to sea level as the <span class="hlt">ice</span> shelves that protect these glaciers will melt faster in contact with more heat from the surrounding oc</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33D1236L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33D1236L"><span>Geodetic <span class="hlt">mass</span> <span class="hlt">balance</span> measurements on debris and clean-<span class="hlt">ice</span> tropical glaciers in Ecuador</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>La Frenierre, J.; Decker, C. R.; Jordan, E.; Wigmore, O.; Hodge, B. E.; Niederriter, C.; Michels, A.</p> <p>2017-12-01</p> <p>Glaciers are recognized as highly sensitive indicators of climate change in high altitude, low latitude environments. In the tropical Andes, various analyses of glacier surface area change have helped illuminate the manifestation of climate change in this region, however, information about actual glacier <span class="hlt">mass</span> <span class="hlt">balance</span> behavior is much more limited given the relatively small glaciers, difficult access, poor weather, and/or limited local resources common here. Several new technologies, including aerial and terrestrial LIDAR and structure-from-motion photogrammetry using small unmanned aerial vehicles (UAVs), make <span class="hlt">mass</span> <span class="hlt">balance</span> measurements using geodetic approaches increasingly feasible in remote mountain locations, which can both further our understanding of changing climatic conditions, and improve our ability to evaluate the downstream hydrologic impacts of <span class="hlt">ice</span> loss. At Volcán Chimborazo, Ecuador, these new technologies, combined with a unique, 5-meter resolution digital elevation model derived from 1997 aerial imagery, make possible an analysis of the magnitude and spatial patterns of <span class="hlt">mass</span> <span class="hlt">balance</span> behavior over the past two decades. Here, we evaluate <span class="hlt">ice</span> loss between 1997 and 2017 at the tongues of two adjacent glaciers, one debris-covered and detached from its accumulation area (Reschreiter Glacier), and one debris-free and intact (Hans Meyer Glacier). Additionally, we incorporate data from 2012 and 2013 terrestrial LIDAR surveys to evaluate the behavior of the Reschreiter at a finer temporal resolution. We find that on the Hans Meyer, the mean surface deflation rate since 1997 at the present-day tongue has been nearly 3 m yr-1, while on the lower-elevation Reschreiter, the mean deflation rate has been approximately 1 m yr-1. However, the processes by which debris-covered <span class="hlt">ice</span> becomes exposed results in highly heterogeneous patterns of <span class="hlt">ice</span> loss, with some areas experiencing surface deflation rates approaching 15 m yr-1 when energy absorption is unimpeded.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1918364H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1918364H"><span>Sea <span class="hlt">Ice</span> <span class="hlt">Mass</span> <span class="hlt">Balance</span> Buoys (IMBs): First Results from a Data Processing Intercomparison Study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoppmann, Mario; Tiemann, Louisa; Itkin, Polona</p> <p>2017-04-01</p> <p>IMBs are autonomous instruments able to continuously monitor the growth and melt of sea <span class="hlt">ice</span> and its snow cover at a single point on an <span class="hlt">ice</span> floe. Complementing field expeditions, remote sensing observations and modelling studies, these in-situ data are crucial to assess the <span class="hlt">mass</span> <span class="hlt">balance</span> and seasonal evolution of sea <span class="hlt">ice</span> and snow in the polar oceans. Established subtypes of IMBs combine coarse-resolution temperature profiles through air, snow, <span class="hlt">ice</span> and ocean with ultrasonic pingers to detect snow accumulation and <span class="hlt">ice</span> thermodynamic growth. Recent technological advancements enable the use of high-resolution temperature chains, which are also able to identify the surrounding medium through a „heating cycle". The temperature change during this heating cycle provides additional information on the internal properties and processes of the <span class="hlt">ice</span>. However, a unified data processing technique to reliably and accurately determine sea <span class="hlt">ice</span> thickness and snow depth from this kind of data is still missing, and an unambiguous interpretation remains a challenge. Following the need to improve techniques for remotely measuring sea <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>, an international IMB working group has recently been established. The main goals are 1) to coordinate IMB deployments, 2) to enhance current IMB data processing and -interpretation techniques, and 3) to provide standardized IMB data products to a broader community. Here we present first results from two different data processing algorithms, applied to selected IMB datasets from the Arctic and Antarctic. Their performance with regard to sea <span class="hlt">ice</span> thickness and snow depth retrieval is evaluated, and an uncertainty is determined. Although several challenges and caveats in IMB data processing and -interpretation are found, such datasets bear great potential and yield plenty of useful information about sea <span class="hlt">ice</span> properties and processes. It is planned to include many more algorithms from contributors within the working group, and we explicitly invite</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000038172&hterms=BALANCE+SHEET&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DBALANCE%2BSHEET','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000038172&hterms=BALANCE+SHEET&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DBALANCE%2BSHEET"><span><span class="hlt">Balance</span> Velocities of the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Joughin, Ian; Fahnestock, Mark; Ekholm, Simon; Kwok, Ron</p> <p>1997-01-01</p> <p>We present a map of <span class="hlt">balance</span> velocities for the Greenland <span class="hlt">ice</span> sheet. The resolution of the underlying DEM, which was derived primarily from radar altimetry data, yields far greater detail than earlier <span class="hlt">balance</span> velocity estimates for Greenland. The velocity contours reveal in striking detail the location of an <span class="hlt">ice</span> stream in northeastern Greenland, which was only recently discovered using satellite imagery. Enhanced flow associated with all of the major outlets is clearly visible, although small errors in the source data result in less accurate estimates of the absolute flow speeds. Nevertheless, the <span class="hlt">balance</span> map is useful for <span class="hlt">ice</span>-sheet modelling, <span class="hlt">mass</span> <span class="hlt">balance</span> studies, and field planning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12.1273R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12.1273R"><span>Changing pattern of <span class="hlt">ice</span> flow and <span class="hlt">mass</span> <span class="hlt">balance</span> for glaciers discharging into the Larsen A and B embayments, Antarctic Peninsula, 2011 to 2016</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rott, Helmut; Abdel Jaber, Wael; Wuite, Jan; Scheiblauer, Stefan; Floricioiu, Dana; Melchior van Wessem, Jan; Nagler, Thomas; Miranda, Nuno; van den Broeke, Michiel R.</p> <p>2018-04-01</p> <p>We analysed volume change and <span class="hlt">mass</span> <span class="hlt">balance</span> of outlet glaciers on the northern Antarctic Peninsula over the periods 2011 to 2013 and 2013 to 2016, using high-resolution topographic data from the bistatic interferometric radar satellite mission TanDEM-X. Complementary to the geodetic method that applies DEM differencing, we computed the net <span class="hlt">mass</span> <span class="hlt">balance</span> of the main outlet glaciers using the <span class="hlt">mass</span> budget method, accounting for the difference between the surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) and the discharge of <span class="hlt">ice</span> into an ocean or <span class="hlt">ice</span> shelf. The SMB values are based on output of the regional climate model RACMO version 2.3p2. To study glacier flow and retrieve <span class="hlt">ice</span> discharge we generated time series of <span class="hlt">ice</span> velocity from data from different satellite radar sensors, with radar images of the satellites TerraSAR-X and TanDEM-X as the main source. The study area comprises tributaries to the Larsen A, Larsen Inlet and Prince Gustav Channel embayments (region A), the glaciers calving into the Larsen B embayment (region B) and the glaciers draining into the remnant part of the Larsen B <span class="hlt">ice</span> shelf in Scar Inlet (region C). The glaciers of region A, where the buttressing <span class="hlt">ice</span> shelf disintegrated in 1995, and of region B (<span class="hlt">ice</span> shelf break-up in 2002) show continuing losses in <span class="hlt">ice</span> <span class="hlt">mass</span>, with significant reduction of losses after 2013. The <span class="hlt">mass</span> <span class="hlt">balance</span> numbers for the grounded glacier area of region A are -3.98 ± 0.33 Gt a-1 from 2011 to 2013 and -2.38 ± 0.18 Gt a-1 from 2013 to 2016. The corresponding numbers for region B are -5.75 ± 0.45 and -2.32 ± 0.25 Gt a-1. The <span class="hlt">mass</span> <span class="hlt">balance</span> in region C during the two periods was slightly negative, at -0.54 ± 0.38 Gt a-1 and -0.58 ± 0.25 Gt a-1. The main share in the overall <span class="hlt">mass</span> losses of the region was contributed by two glaciers: Drygalski Glacier contributing 61 % to the <span class="hlt">mass</span> deficit of region A, and Hektoria and Green glaciers accounting for 67 % to the <span class="hlt">mass</span> deficit of region B. Hektoria and Green glaciers accelerated significantly in 2010</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C41E0728S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C41E0728S"><span>On the Utilization of <span class="hlt">Ice</span> Flow Models and Uncertainty Quantification to Interpret the Impact of Surface Radiation Budget Errors on Estimates of Greenland <span class="hlt">Ice</span> Sheet Surface <span class="hlt">Mass</span> <span class="hlt">Balance</span> and Regional Estimates of <span class="hlt">Mass</span> <span class="hlt">Balance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schlegel, N.; Larour, E. Y.; Gardner, A. S.; Lang, C.; Miller, C. E.; van den Broeke, M. R.</p> <p>2016-12-01</p> <p>How Greenland <span class="hlt">ice</span> flow may respond to future increases in surface runoff and to increases in the frequency of extreme melt events is unclear, as it requires detailed comprehension of Greenland surface climate and the <span class="hlt">ice</span> sheet's sensitivity to associated uncertainties. With established uncertainty quantification tools run within the framework of <span class="hlt">Ice</span> Sheet System Model (ISSM), we conduct decadal-scale forward modeling experiments to 1) quantify the spatial resolution needed to effectively force distinct components of the surface radiation budget, and subsequently surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB), in various regions of the <span class="hlt">ice</span> sheet and 2) determine the dynamic response of Greenland <span class="hlt">ice</span> flow to variations in components of the net radiation budget. The Glacier Energy and <span class="hlt">Mass</span> <span class="hlt">Balance</span> (GEMB) software is a column surface model (1-D) that has recently been embedded as a module within ISSM. Using the ISSM-GEMB framework, we perform sensitivity analyses to determine how perturbations in various components of the surface radiation budget affect model output; these model experiments allow us predict where and on what spatial scale the <span class="hlt">ice</span> sheet is likely to dynamically respond to changes in these parameters. Preliminary results suggest that SMB should be forced at at least a resolution of 23 km to properly capture dynamic <span class="hlt">ice</span> response. In addition, Monte-Carlo style sampling analyses reveals that the areas with the largest uncertainty in <span class="hlt">mass</span> flux are located near the equilibrium line altitude (ELA), upstream of major outlet glaciers in the North and West of the <span class="hlt">ice</span> sheet. Sensitivity analysis indicates that these areas are also the most vulnerable on the <span class="hlt">ice</span> sheet to persistent, far-field shifts in SMB, suggesting that continued warming, and upstream shift in the ELA, are likely to result in increased velocities, and consequentially SMB-induced thinning upstream of major outlet glaciers. Here, we extend our investigation to consider various components of the surface radiation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11.1501B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11.1501B"><span>Winter <span class="hlt">mass</span> <span class="hlt">balance</span> of Drangajökull <span class="hlt">ice</span> cap (NW Iceland) derived from satellite sub-meter stereo images</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Belart, Joaquín M. C.; Berthier, Etienne; Magnússon, Eyjólfur; Anderson, Leif S.; Pálsson, Finnur; Thorsteinsson, Thorsteinn; Howat, Ian M.; Aðalgeirsdóttir, Guðfinna; Jóhannesson, Tómas; Jarosch, Alexander H.</p> <p>2017-06-01</p> <p>Sub-meter resolution, stereoscopic satellite images allow for the generation of accurate and high-resolution digital elevation models (DEMs) over glaciers and <span class="hlt">ice</span> caps. Here, repeated stereo images of Drangajökull <span class="hlt">ice</span> cap (NW Iceland) from Pléiades and WorldView2 (WV2) are combined with in situ estimates of snow density and densification of firn and fresh snow to provide the first estimates of the glacier-wide geodetic winter <span class="hlt">mass</span> <span class="hlt">balance</span> obtained from satellite imagery. Statistics in snow- and <span class="hlt">ice</span>-free areas reveal similar vertical relative accuracy (< 0.5 m) with and without ground control points (GCPs), demonstrating the capability for measuring seasonal snow accumulation. The calculated winter (14 October 2014 to 22 May 2015) <span class="hlt">mass</span> <span class="hlt">balance</span> of Drangajökull was 3.33 ± 0.23 m w.e. (meter water equivalent), with ∼ 60 % of the accumulation occurring by February, which is in good agreement with nearby ground observations. On average, the repeated DEMs yield 22 % less elevation change than the length of eight winter snow cores due to (1) the time difference between in situ and satellite observations, (2) firn densification and (3) elevation changes due to <span class="hlt">ice</span> dynamics. The contributions of these three factors were of similar magnitude. This study demonstrates that seasonal geodetic <span class="hlt">mass</span> <span class="hlt">balance</span> can, in many areas, be estimated from sub-meter resolution satellite stereo images.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/wri/2000/4074/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/wri/2000/4074/report.pdf"><span><span class="hlt">Mass</span> <span class="hlt">balance</span>, meteorological, <span class="hlt">ice</span> motion, surface altitude, runoff, and <span class="hlt">ice</span> thickness data at Gulkana Glacier, Alaska, 1995 <span class="hlt">balance</span> year</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>March, Rod S.</p> <p>2000-01-01</p> <p>The 1995 measured winter snow, maximum winter snow, net, and annual <span class="hlt">balances</span> in the Gulkana Glacier basin were evaluated on the basis of meteorological, hydrological, and glaciological data obtained in the basin. Averaged over the glacier, the measured winter snow <span class="hlt">balance</span> was 0.94 meter on April 19, 1995, 0.6 standard deviation below the long-term average; the maximum winter snow <span class="hlt">balance</span>, 0.94 meter, was reached on April 25, 1995; the net <span class="hlt">balance</span> (from September 18, 1994 to August 29, 1995) was -0.70 meter, 0.76 standard deviation below the long-term average. The annual <span class="hlt">balance</span> (October 1, 1994, to September 30, 1995) was -0.86 meter. <span class="hlt">Ice</span>-surface motion and altitude changes measured at three index sites document seasonal <span class="hlt">ice</span> speed and glacier-thickness changes. Annual stream runoff was 2.05 meters averaged over the basin, approximately equal to the long-term average. The 1976 <span class="hlt">ice</span>-thickness data are reported from a single site near the highest measurement site (180 meters thick) and from two glacier cross profiles near the mid-glacier (270 meters thick on centerline) and low glacier (150 meters thick on centerline) measurement sites. A new area-altitude distribution determined from 1993 photogrammetry is reported. Area-averaged <span class="hlt">balances</span> are reported from both the 1967 and 1993 area-altitude distribution so the reader may directly see the effect of the update. Briefly, loss of ablation area between 1967 and 1993 results in a larger weighting being applied to data from the upper glacier site and hence, increases calculated area-averaged <span class="hlt">balances</span>. The <span class="hlt">balance</span> increase is of the order of 15 percent for net <span class="hlt">balance</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110006429','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110006429"><span>Changes in the <span class="hlt">Mass</span> <span class="hlt">Balance</span> of the Greenland <span class="hlt">Ice</span> Sheet in a Warming Climate During 2003-2009</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Luthcke, Scott</p> <p>2010-01-01</p> <p><span class="hlt">Mass</span> changes of the Greenland <span class="hlt">ice</span> sheet (GIS) derived from ICESat and GRACE data both show that the net <span class="hlt">mass</span> loss from GIS during 2003-2009 is about 175 Gt/year, which contributes 0.5mm/yr global sea-level rise. The rate of <span class="hlt">mass</span> loss has increased significantly since the 1990's when the GIS was close to <span class="hlt">mass</span> <span class="hlt">balance</span>. Even though the GIS was close to <span class="hlt">mass</span> <span class="hlt">balance</span> during the 1990's, it was already showing characteristics of responding to8 warmer climate, specifically thinning at the margins and thickening inland at higher elevations. During 2003-2009, increased <span class="hlt">ice</span> thinning due to increases in melting and acceleration of outlet glaciers began to strongly exceed the inland thickening from increases in accumulation. Over the entire GIS, the <span class="hlt">mass</span> loss between the two periods, from increased melting and <span class="hlt">ice</span> dynamics, increased by about 190 Gt/year while the <span class="hlt">mass</span> gain, from increased precipitation and accumulation, increased by only about 15Gt/year. These <span class="hlt">ice</span> changes occurred during a time when the temperature on GIS changed at rate of about 2K/decade. The distribution of elevation and <span class="hlt">mass</span> changes derived from ICESat have high spatial resolution showing details over outlet glaciers, by drainage systems, and by elevation. However, information on the seasonal cycle of changes from ICESat data is limited, because the ICESat lasers were only operated during two to three campaigns per year of about 35 days duration each. In contrast, the temporal resolution of GRACE data, provided by the continuous data collection, is much better showing details of the seasonal cycle and the inter-annual variability. The differing sensitivity of the ICESat altimetry and the GRACE gravity methods to motion of the underlying bedrock from glacial isostatic adjustment (GIA) is used to evaluate the GIA corrections provided by models. The two data types are also combined to make estimates of the partitioning of the <span class="hlt">mass</span> gains and losses among accumulation, melting, and <span class="hlt">ice</span> discharge from outlet</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.C11A0094S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.C11A0094S"><span>Estimation of Greenland's <span class="hlt">Ice</span> Sheet <span class="hlt">Mass</span> <span class="hlt">Balance</span> Using ICESat and GRACE Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Slobbe, D.; Ditmar, P.; Lindenbergh, R.</p> <p>2007-12-01</p> <p>Data of the GRACE gravity mission and the ICESat laser altimetry mission are used to create two independent estimates of Greenland's <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> over the full measurement period. For ICESat data, a processing strategy is developed using the elevation differences of geometrically overlapping footprints of both crossing and repeated tracks. The dataset is cleaned using quality flags defined by the GLAS science team. The cleaned dataset reveals some strong, spatially correlated signals that are shown to be related to physical phenomena. Different processing strategies are used to convert the observed temporal height differences to <span class="hlt">mass</span> changes for 6 different drainage systems, further divided into a region above and below 2000 meter elevation. The results are compared with other altimetry based <span class="hlt">mass</span> <span class="hlt">balance</span> estimates. In general, the obtained results confirm trends discovered by others, but we also show that the choice of processing strategy strongly influences our results, especially for the areas below 2000 meter. Furthermore, GRACE based monthly variations of the Earth's gravity field as processed by CNES, CSR, GFZ and DEOS are used to estimate the <span class="hlt">mass</span> <span class="hlt">balance</span> change for North and South Greenland. It is shown that our results are comparable with recently published GRACE estimates (mascon solutions). On the other hand, the estimates based on GRACE data are only partly confirmed by the ICESat estimates. Possible explanations for the obvious differences will be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11.2655S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11.2655S"><span>GPS-derived estimates of surface <span class="hlt">mass</span> <span class="hlt">balance</span> and ocean-induced basal melt for Pine Island Glacier <span class="hlt">ice</span> shelf, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shean, David E.; Christianson, Knut; Larson, Kristine M.; Ligtenberg, Stefan R. M.; Joughin, Ian R.; Smith, Ben E.; Stevens, C. Max; Bushuk, Mitchell; Holland, David M.</p> <p>2017-11-01</p> <p>In the last 2 decades, Pine Island Glacier (PIG) experienced marked speedup, thinning, and grounding-line retreat, likely due to marine <span class="hlt">ice</span>-sheet instability and <span class="hlt">ice</span>-shelf basal melt. To better understand these processes, we combined 2008-2010 and 2012-2014 GPS records with dynamic firn model output to constrain local surface and basal <span class="hlt">mass</span> <span class="hlt">balance</span> for PIG. We used GPS interferometric reflectometry to precisely measure absolute surface elevation (zsurf) and Lagrangian surface elevation change (Dzsurf/ Dt). Observed surface elevation relative to a firn layer tracer for the initial surface (zsurf - zsurf0') is consistent with model estimates of surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB, primarily snow accumulation). A relatively abrupt ˜ 0.2-0.3 m surface elevation decrease, likely due to surface melt and increased compaction rates, is observed during a period of warm atmospheric temperatures from December 2012 to January 2013. Observed Dzsurf/ Dt trends (-1 to -4 m yr-1) for the PIG shelf sites are all highly linear. Corresponding basal melt rate estimates range from ˜ 10 to 40 m yr-1, in good agreement with those derived from <span class="hlt">ice</span>-bottom acoustic ranging, phase-sensitive <span class="hlt">ice</span>-penetrating radar, and high-resolution stereo digital elevation model (DEM) records. The GPS and DEM records document higher melt rates within and near features associated with longitudinal extension (i.e., transverse surface depressions, rifts). Basal melt rates for the 2012-2014 period show limited temporal variability despite large changes in ocean temperature recorded by moorings in Pine Island Bay. Our results demonstrate the value of long-term GPS records for <span class="hlt">ice</span>-shelf <span class="hlt">mass</span> <span class="hlt">balance</span> studies, with implications for the sensitivity of <span class="hlt">ice</span>-ocean interaction at PIG.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120002070','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120002070"><span>Assessment of Antarctic <span class="hlt">Ice</span>-Sheet <span class="hlt">Mass</span> <span class="hlt">Balance</span> Estimates: 1992 - 2009</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Giovinetto, Mario B.</p> <p>2011-01-01</p> <p>Published <span class="hlt">mass</span> <span class="hlt">balance</span> estimates for the Antarctic <span class="hlt">Ice</span> Sheet (AIS) lie between approximately +50 to -250 Gt/year for 1992 to 2009, which span a range equivalent to 15% of the annual <span class="hlt">mass</span> input and 0.8 mm/year Sea Level Equivalent (SLE). Two estimates from radar-altimeter measurements of elevation change by European Remote-sensing Satellites (ERS) (+28 and -31 Gt/year) lie in the upper part, whereas estimates from the Input-minus-Output Method (IOM) and the Gravity Recovery and Climate Experiment (GRACE) lie in the lower part (-40 to -246 Gt/year). We compare the various estimates, discuss the methodology used, and critically assess the results. Although recent reports of large and accelerating rates of <span class="hlt">mass</span> loss from GRACE=based studies cite agreement with IOM results, our evaluation does not support that conclusion. We find that the extrapolation used in the published IOM estimates for the 15 % of the periphery for which discharge velocities are not observed gives twice the rate of discharge per unit of associated <span class="hlt">ice</span>-sheet area than the 85% faster-moving parts. Our calculations show that the published extrapolation overestimates the <span class="hlt">ice</span> discharge by 282 Gt/yr compared to our assumption that the slower moving areas have 70% as much discharge per area as the faster moving parts. Also, published data on the time-series of discharge velocities and accumulation/precipitation do not support <span class="hlt">mass</span> output increases or input decreases with time, respectively. Our modified IOM estimate, using the 70% discharge assumption and substituting input from a field-data compilation for input from an atmospheric model over 6% of area, gives a loss of only 13 Gt/year (versus 136 Gt/year) for the period around 2000. Two ERS-based estimates, our modified IOM, and a GRACE-based estimate for observations within 1992 to 2005 lie in a narrowed range of +27 to - 40 Gt/year, which is about 3% of the annual <span class="hlt">mass</span> input and only 0.2 mm/year SLE. Our preferred estimate for 1992-2001 is - 47 Gt</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.6251B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.6251B"><span>Quantifying <span class="hlt">ice</span> cliff contribution to debris-covered glacier <span class="hlt">mass</span> <span class="hlt">balance</span> from multiple sensors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brun, Fanny; Wagnon, Patrick; Berthier, Etienne; Kraaijenbrink, Philip; Immerzeel, Walter; Shea, Joseph; Vincent, Christian</p> <p>2017-04-01</p> <p><span class="hlt">Ice</span> cliffs on debris-covered glaciers have been recognized as a hot spot for glacier melt. <span class="hlt">Ice</span> cliffs are steep (even sometimes overhanging) and fast evolving surface features, which make them challenging to monitor. We surveyed the topography of Changri Nup Glacier (Nepalese Himalayas, Everest region) in November 2015 and 2016 using multiple sensors: terrestrial photogrammetry, Unmanned Aerial Vehicle (UAV) photogrammetry, Pléiades stereo images and ASTER stereo images. We derived 3D point clouds and digital elevation models (DEMs) following a Structure-from-Motion (SfM) workflow for the first two sets of data to monitor surface elevation changes and calculate the associated volume loss. We derived only DEMs for the two last data sets. The derived DEMs had resolutions ranging from < 5 cm to 30 m. The derived point clouds and DEMs are used to quantify the <span class="hlt">ice</span> melt of the cliffs at different scales. The very high resolution SfM point clouds, together with the surface velocity field, will be used to calculate the volume losses of 14 individual cliffs, depending on their size, aspect or the presence of supra glacial lake. Then we will extend this analysis to the whole glacier to quantify the contribution of <span class="hlt">ice</span> cliff melt to the overall glacier <span class="hlt">mass</span> <span class="hlt">balance</span>, calculated with the UAV and Pléiades DEMs. This research will provide important tools to evaluate the role of <span class="hlt">ice</span> cliffs in regional <span class="hlt">mass</span> loss.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.6823K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.6823K"><span>Antarctic <span class="hlt">mass</span> <span class="hlt">balance</span> changes from GRACE</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kallenberg, B.; Tregoning, P.</p> <p>2012-04-01</p> <p>The Antarctic <span class="hlt">ice</span> sheet contains ~30 million km3 of <span class="hlt">ice</span> and constitutes a significant component of the global water <span class="hlt">balance</span> with enough freshwater to raise global sea level by ~60 m. Altimetry measurements and climate models suggest variable behaviour across the Antarctic <span class="hlt">ice</span> sheet, with thickening occurring in a vast area of East Antarctica and substantial thinning in West Antarctica caused by increased temperature gradients in the surrounding ocean. However, the rate at which the polar <span class="hlt">ice</span> cap is melting is still poorly constrained. To calculate the <span class="hlt">mass</span> loss of an <span class="hlt">ice</span> sheet it is necessary to separate present day <span class="hlt">mass</span> <span class="hlt">balance</span> changes from glacial isostatic adjustment (GIA), the response of the Earth's crust to <span class="hlt">mass</span> loss, wherefore it is essential to undertake sufficient geological and geomorphological sampling. As there is only a limited possibility for this in Antarctica, all models (i.e. geological, hydrological as well as atmospheric) are very poorly constrained. Therefore, space-geodetic observations play an important role in detecting changes in <span class="hlt">mass</span> and spatial variations in the Earth's gravity field. The Gravity Recovery And Climate Experiment (GRACE) observed spatial variations in the Earth's gravity field over the past ten years. The satellite detects <span class="hlt">mass</span> variations in the Earth system including geophysical, hydrological and atmospheric shifts. GRACE itself is not able to separate the GIA from <span class="hlt">mass</span> <span class="hlt">balance</span> changes and, due to the insufficient geological and geomorphological database, it is not possible to model the GIA effect accurately for Antarctica. However, the results from GRACE can be compared with other scientific results, coming from other geodetic observations such as satellite altimetry and GPS or by the use of geological observations. In our contribution we compare the GRACE data with recorded precipitation patterns and <span class="hlt">mass</span> anomalies over East Antarctica to separate the observed GRACE signal into its two components: GIA as a result of <span class="hlt">mass</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....13008H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....13008H"><span>Glaciological constraints on current <span class="hlt">ice</span> <span class="hlt">mass</span> changes from modelling the <span class="hlt">ice</span> sheets over the glacial cycles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huybrechts, P.</p> <p>2003-04-01</p> <p>The evolution of continental <span class="hlt">ice</span> sheets introduces a long time scale in the climate system. Large <span class="hlt">ice</span> sheets have a memory of millenia, hence the present-day <span class="hlt">ice</span> sheets of Greenland and Antarctica are still adjusting to climatic variations extending back to the last glacial period. This trend is separate from the direct response to <span class="hlt">mass-balance</span> changes on decadal time scales and needs to be correctly accounted for when assessing current and future contributions to sea level. One way to obtain estimates of current <span class="hlt">ice</span> <span class="hlt">mass</span> changes is to model the past history of the <span class="hlt">ice</span> sheets and their underlying beds over the glacial cycles. Such calculations assist to distinguish between the longer-term <span class="hlt">ice</span>-dynamic evolution and short-term <span class="hlt">mass-balance</span> changes when interpreting altimetry data, and are helpful to isolate the effects of postglacial rebound from gravity and altimetry trends. The presentation will discuss results obtained from 3-D thermomechanical <span class="hlt">ice</span>-sheet/lithosphere/bedrock models applied to the Antarctic and Greenland <span class="hlt">ice</span> sheets. The simulations are forced by time-dependent boundary conditions derived from sediment and <span class="hlt">ice</span> core records and are constrained by geomorphological and glacial-geological data of past <span class="hlt">ice</span> sheet and sea-level stands. Current simulations suggest that the Greenland <span class="hlt">ice</span> sheet is close to <span class="hlt">balance</span>, while the Antarctic <span class="hlt">ice</span> sheet is still losing <span class="hlt">mass</span>, mainly due to incomplete grounding-line retreat of the West Antarctic <span class="hlt">ice</span> sheet since the LGM. The results indicate that altimetry trends are likely dominated by <span class="hlt">ice</span> thickness changes but that the gravitational signal mainly reflects postglacial rebound.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70015528','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70015528"><span><span class="hlt">Mass</span> <span class="hlt">balance</span> and sliding velocity of the Puget lobe of the cordilleran <span class="hlt">ice</span> sheet during the last glaciation</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Booth, D.B.</p> <p>1986-01-01</p> <p>An estimate of the sliding velocity and basal meltwater discharge of the Puget lobe of the Cordilleran <span class="hlt">ice</span> sheet can be calculated from its reconstructed extent, altitude, and <span class="hlt">mass</span> <span class="hlt">balance</span>. Lobe dimensions and surface altitudes are inferred from <span class="hlt">ice</span> limits and flow-direction indicators. Net annual <span class="hlt">mass</span> <span class="hlt">balance</span> and total ablation are calculated from relations empirically derived from modern maritime glaciers. An equilibrium-line altitude between 1200 and 1250 m is calculated for the maximum glacial advance (ca. 15,000 yr B.P.) during the Vashon Stade of the Fraser Glaciation. This estimate is in accord with geologic data and is insensitive to plausible variability in the parameters used in the reconstruction. Resultant sliding velocities are as much as 650 m/a at the equilibrium line, decreasing both up- and downglacier. Such velocities for an <span class="hlt">ice</span> sheet of this size are consistent with nonsurging behavior. Average meltwater discharge increases monotonically downglacier to 3000 m3/sec at the terminus and is of a comparable magnitude to <span class="hlt">ice</span> discharge over much of the glacier's ablation area. Palcoclimatic inferences derived from this reconstruction are consistent with previous, independently derived studies of late Pleistocene temperature and precipitation in the Pacific Northwest. ?? 1986.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active"><span>3</span></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_3 --> <div id="page_4" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="61"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030020763','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030020763"><span>Understanding Recent <span class="hlt">Mass</span> <span class="hlt">Balance</span> Changes of the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>vanderVeen, Cornelius</p> <p>2003-01-01</p> <p>The ultimate goal of this project is to better understand the current transfer of <span class="hlt">mass</span> between the Greenland <span class="hlt">Ice</span> Sheet, the world's oceans and the atmosphere, and to identify processes controlling the rate of this transfer, to be able to predict with greater confidence future contributions to global sea level rise. During the first year of this project, we focused on establishing longer-term records of change of selected outlet glaciers, reevaluation of <span class="hlt">mass</span> input to the <span class="hlt">ice</span> sheet and analysis of climate records derived from <span class="hlt">ice</span> cores, and modeling meltwater production and runoff from the margins of the <span class="hlt">ice</span> sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18..575B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18..575B"><span>Investigating <span class="hlt">ice</span> cliff evolution and contribution to glacier <span class="hlt">mass-balance</span> using a physically-based dynamic model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buri, Pascal; Miles, Evan; Ragettli, Silvan; Brun, Fanny; Steiner, Jakob; Pellicciotti, Francesca</p> <p>2016-04-01</p> <p>Supraglacial cliffs are a surface feature typical of debris-covered glaciers, affecting surface evolution, glacier downwasting and <span class="hlt">mass</span> <span class="hlt">balance</span> by providing a direct <span class="hlt">ice</span>-atmosphere interface. As a result, melt rates can be very high and <span class="hlt">ice</span> cliffs may account for a significant portion of the total glacier <span class="hlt">mass</span> loss. However, their contribution to glacier <span class="hlt">mass</span> <span class="hlt">balance</span> has rarely been quantified through physically-based models. Most cliff energy <span class="hlt">balance</span> models are point scale models which calculate energy fluxes at individual cliff locations. Results from the only grid based model to date accurately reflect energy fluxes and cliff melt, but modelled backwasting patterns are in some cases unrealistic, as the distribution of melt rates would lead to progressive shallowing and disappearance of cliffs. Based on a unique multitemporal dataset of cliff topography and backwasting obtained from high-resolution terrestrial and aerial Structure-from-Motion analysis on Lirung Glacier in Nepal, it is apparent that cliffs exhibit a range of behaviours but most do not rapidly disappear. The patterns of evolution cannot be explained satisfactorily by atmospheric melt alone, and are moderated by the presence of supraglacial ponds at the base of cliffs and by cliff reburial with debris. Here, we document the distinct patterns of evolution including disappearance, growth and stability. We then use these observations to improve the grid-based energy <span class="hlt">balance</span> model, implementing periodic updates of the cliff geometry resulting from modelled melt perpendicular to the <span class="hlt">ice</span> surface. Based on a slope threshold, pixels can be reburied by debris or become debris-free. The effect of ponds are taken into account through enhanced melt rates in horizontal direction on pixels selected based on an algorithm considering distance to the water surface, slope and lake level. We use the dynamic model to first study the evolution of selected cliffs for which accurate, high resolution DEMs are available</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10903198','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10903198"><span>Greenland <span class="hlt">Ice</span> Sheet: High-Elevation <span class="hlt">Balance</span> and Peripheral Thinning.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Krabill; Abdalati; Frederick; Manizade; Martin; Sonntag; Swift; Thomas; Wright; Yungel</p> <p>2000-07-21</p> <p>Aircraft laser-altimeter surveys over northern Greenland in 1994 and 1999 have been coupled with previously reported data from southern Greenland to analyze the recent <span class="hlt">mass-balance</span> of the Greenland <span class="hlt">Ice</span> Sheet. Above 2000 meters elevation, the <span class="hlt">ice</span> sheet is in <span class="hlt">balance</span> on average but has some regions of local thickening or thinning. Thinning predominates at lower elevations, with rates exceeding 1 meter per year close to the coast. Interpolation of our results between flight lines indicates a net loss of about 51 cubic kilometers of <span class="hlt">ice</span> per year from the entire <span class="hlt">ice</span> sheet, sufficient to raise sea level by 0.13 millimeter per year-approximately 7% of the observed rise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930022703&hterms=balance+sheet&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dbalance%2Bsheet','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930022703&hterms=balance+sheet&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dbalance%2Bsheet"><span><span class="hlt">Mass</span> <span class="hlt">balance</span> assessment using GPS</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hulbe, Christina L.</p> <p>1993-01-01</p> <p><span class="hlt">Mass</span> <span class="hlt">balance</span> is an integral part of any comprehensive glaciological investigation. Unfortunately, it is hard to determine at remote locations where there is no fixed reference. The Global Positioning System (GPS) offers a solution. Simultaneous GPS observations at a known location and the remote field site, processed differentially, will accurately position the camp site. From there, a monument planted in the firn atop the <span class="hlt">ice</span> can also be accurately positioned. Change in the monument's vertical position is a direct indicator of <span class="hlt">ice</span> thickness change. Because the monument is not connected to the <span class="hlt">ice</span>, its motion is due to both <span class="hlt">mass</span> <span class="hlt">balance</span> change and to the settling of firn as it densifies into <span class="hlt">ice</span>. Observations of relative position change between the monument and anchors at various depths within the firn are used to remove the settling effect. An experiment to test this method has begun at Byrd Station on the West Antarctic <span class="hlt">Ice</span> Sheet and the first epoch of observations was made. Analysis indicates that positioning errors will be very small. It appears likely that the largest errors involved with this technique will arise from ancillary data needed to determine firn settling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C11B0906W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C11B0906W"><span>Gaussian Process Model for Antarctic Surface <span class="hlt">Mass</span> <span class="hlt">Balance</span> and <span class="hlt">Ice</span> Core Site Selection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>White, P. A.; Reese, S.; Christensen, W. F.; Rupper, S.</p> <p>2017-12-01</p> <p>Surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) is an important factor in the estimation of sea level change, and data are collected to estimate models for prediction of SMB on the Antarctic <span class="hlt">ice</span> sheet. Using Favier et al.'s (2013) quality-controlled aggregate data set of SMB field measurements, a fully Bayesian spatial model is posed to estimate Antarctic SMB and propose new field measurement locations. Utilizing Nearest-Neighbor Gaussian process (NNGP) models, SMB is estimated over the Antarctic <span class="hlt">ice</span> sheet. An Antarctic SMB map is rendered using this model and is compared with previous estimates. A prediction uncertainty map is created to identify regions of high SMB uncertainty. The model estimates net SMB to be 2173 Gton yr-1 with 95% credible interval (2021,2331) Gton yr-1. On average, these results suggest lower Antarctic SMB and higher uncertainty than previously purported [Vaughan et al. (1999); Van de Berg et al. (2006); Arthern, Winebrenner and Vaughan (2006); Bromwich et al. (2004); Lenaerts et al. (2012)], even though this model utilizes significantly more observations than previous models. Using the Gaussian process' uncertainty and model parameters, we propose 15 new measurement locations for field study utilizing a maximin space-filling, error-minimizing design; these potential measurements are identied to minimize future estimation uncertainty. Using currently accepted Antarctic <span class="hlt">mass</span> <span class="hlt">balance</span> estimates and our SMB estimate, we estimate net <span class="hlt">mass</span> loss [Shepherd et al. (2012); Jacob et al. (2012)]. Furthermore, we discuss modeling details for both space-time data and combining field measurement data with output from mathematical models using the NNGP framework.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRF..118..667S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRF..118..667S"><span>Decadal-scale sensitivity of Northeast Greenland <span class="hlt">ice</span> flow to errors in surface <span class="hlt">mass</span> <span class="hlt">balance</span> using ISSM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schlegel, N.-J.; Larour, E.; Seroussi, H.; Morlighem, M.; Box, J. E.</p> <p>2013-06-01</p> <p>The behavior of the Greenland <span class="hlt">Ice</span> Sheet, which is considered a major contributor to sea level changes, is best understood on century and longer time scales. However, on decadal time scales, its response is less predictable due to the difficulty of modeling surface climate, as well as incomplete understanding of the dynamic processes responsible for <span class="hlt">ice</span> flow. Therefore, it is imperative to understand how modeling advancements, such as increased spatial resolution or more comprehensive <span class="hlt">ice</span> flow equations, might improve projections of <span class="hlt">ice</span> sheet response to climatic trends. Here we examine how a finely resolved climate forcing influences a high-resolution <span class="hlt">ice</span> stream model that considers longitudinal stresses. We simulate <span class="hlt">ice</span> flow using a two-dimensional Shelfy-Stream Approximation implemented within the <span class="hlt">Ice</span> Sheet System Model (ISSM) and use uncertainty quantification tools embedded within the model to calculate the sensitivity of <span class="hlt">ice</span> flow within the Northeast Greenland <span class="hlt">Ice</span> Stream to errors in surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) forcing. Our results suggest that the model tends to smooth <span class="hlt">ice</span> velocities even when forced with extreme errors in SMB. Indeed, errors propagate linearly through the model, resulting in discharge uncertainty of 16% or 1.9 Gt/yr. We find that <span class="hlt">mass</span> flux is most sensitive to local errors but is also affected by errors hundreds of kilometers away; thus, an accurate SMB map of the entire basin is critical for realistic simulation. Furthermore, sensitivity analyses indicate that SMB forcing needs to be provided at a resolution of at least 40 km.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10903197','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10903197"><span><span class="hlt">Mass</span> <span class="hlt">Balance</span> of the Greenland <span class="hlt">Ice</span> Sheet at High Elevations.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thomas; Akins; Csatho; Fahnestock; Gogineni; Kim; Sonntag</p> <p>2000-07-21</p> <p>Comparison of <span class="hlt">ice</span> discharge from higher elevation areas of the entire Greenland <span class="hlt">Ice</span> Sheet with total snow accumulation gives estimates of <span class="hlt">ice</span> thickening rates over the past few decades. On average, the region has been in <span class="hlt">balance</span>, but with thickening of 21 centimeters per year in the southwest and thinning of 30 centimeters per year in the southeast. The north of the <span class="hlt">ice</span> sheet shows less variability, with average thickening of 2 centimeters per year in the northeast and thinning of about 5 centimeters per year in the northwest. These results agree well with those from repeated altimeter surveys, except in the extreme south, where we find substantially higher rates of both thickening and thinning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRC..123.2422L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRC..123.2422L"><span>Seasonal and Interannual Variations of Sea <span class="hlt">Ice</span> <span class="hlt">Mass</span> <span class="hlt">Balance</span> From the Central Arctic to the Greenland Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lei, Ruibo; Cheng, Bin; Heil, Petra; Vihma, Timo; Wang, Jia; Ji, Qing; Zhang, Zhanhai</p> <p>2018-04-01</p> <p>The seasonal evolution of sea <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> between the Central Arctic and Fram Strait, as well as the underlying driving forces, remain largely unknown because of a lack of observations. In this study, two and three buoys were deployed in the Central Arctic during the summers of 2010 and 2012, respectively. It was established that basal <span class="hlt">ice</span> growth commenced between mid-October and early December. Annual basal <span class="hlt">ice</span> growth, ranging from 0.21 to 1.14 m, was determined mainly by initial <span class="hlt">ice</span> thickness, air temperature, and oceanic heat flux during winter. An analytic thermodynamic model indicated that climate warming reduces the winter growth rate of thin <span class="hlt">ice</span> more than for thick <span class="hlt">ice</span> because of the weak thermal inertia of the former. Oceanic heat flux during the freezing season was 2-4 W m-2, which accounted for 18-31% of the basal <span class="hlt">ice</span> energy <span class="hlt">balance</span>. We identified two mechanisms that modified the oceanic heat flux, i.e., solar energy absorbed by the upper ocean during summer, and interaction with warm waters south of Fram Strait; the latter resulted in basal <span class="hlt">ice</span> melt, even in winter. In summer 2010, <span class="hlt">ice</span> loss in the Central Arctic was considerable, which led to increased oceanic heat flux into winter and delayed <span class="hlt">ice</span> growth. The Transpolar Drift Stream was relatively weak in summer 2013. This reduced sea <span class="hlt">ice</span> advection out of the Arctic Ocean, and it restrained <span class="hlt">ice</span> melt because of the cool atmospheric conditions, weakened albedo feedback, and relatively small oceanic heat flux in the north.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000088622','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000088622"><span>Airborne Laser Altimetry Mapping of the Greenland <span class="hlt">Ice</span> Sheet: Application to <span class="hlt">Mass</span> <span class="hlt">Balance</span> Assessment</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Abdalati, W.; Krabill, W.; Frederick, E.; Manizade, S.; Martin, C.; Sonntag, J.; Swift, R.; Thomas, R.; Wright, W.; Yungel, J.</p> <p>2000-01-01</p> <p>In 1998 and '99, the Arctic <span class="hlt">Ice</span> Mapping (AIM) program completed resurveys of lines occupied 5 years earlier revealing elevation changes of the Greenland <span class="hlt">ice</span> sheet and identifying areas of significant thinning, thickening and <span class="hlt">balance</span>. In planning these surveys, consideration had to be given to the spatial constraints associated with aircraft operation, the spatial nature of <span class="hlt">ice</span> sheet behavior, and limited resources, as well as temporal issues, such as seasonal and interannual variability in the context of measurement accuracy. This paper examines the extent to which the sampling and survey strategy is valid for drawing conclusions on the current state of <span class="hlt">balance</span> of the Greenland <span class="hlt">ice</span> sheet. The surveys covered the entire <span class="hlt">ice</span> sheet with an average distance of 21.4 km between each location on the <span class="hlt">ice</span> sheet and the nearest flight line. For most of the <span class="hlt">ice</span> sheet, the elevation changes show relatively little spatial variability, and their magnitudes are significantly smaller than the observed elevation change signal. As a result, we conclude that the density of the sampling and the accuracy of the measurements are sufficient to draw meaningful conclusions on the state of <span class="hlt">balance</span> of the entire <span class="hlt">ice</span> sheet over the five-year survey period. Outlet glaciers, however, show far more spatial and temporal variability, and each of the major ones is likely to require individual surveys in order to determine its <span class="hlt">balance</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1712737V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712737V"><span>Clouds enhance Greenland <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Van Tricht, Kristof; Gorodetskaya, Irina V.; L'Ecuyer, Tristan; Lenaerts, Jan T. M.; Lhermitte, Stef; Noel, Brice; Turner, David D.; van den Broeke, Michiel R.; van Lipzig, Nicole P. M.</p> <p>2015-04-01</p> <p>Clouds have a profound influence on both the Arctic and global climate, while they still represent one of the key uncertainties in climate models, limiting the fidelity of future climate projections. The potentially important role of thin liquid-containing clouds over Greenland in enhancing <span class="hlt">ice</span> sheet melt has recently gained interest, yet current research is spatially and temporally limited, focusing on particular events, and their large scale impact on the surface <span class="hlt">mass</span> <span class="hlt">balance</span> remains unknown. We used a combination of satellite remote sensing (CloudSat - CALIPSO), ground-based observations and climate model (RACMO) data to show that liquid-containing clouds warm the Greenland <span class="hlt">ice</span> sheet 94% of the time. High surface reflectivity (albedo) for shortwave radiation reduces the cloud shortwave cooling effect on the absorbed fluxes, while not influencing the absorption of longwave radiation. Cloud warming over the <span class="hlt">ice</span> sheet therefore dominates year-round. Only when albedo values drop below ~0.6 in the coastal areas during summer, the cooling effect starts to overcome the warming effect. The year-round excess of energy due to the presence of liquid-containing clouds has an extensive influence on the <span class="hlt">mass</span> <span class="hlt">balance</span> of the <span class="hlt">ice</span> sheet. Simulations using the SNOWPACK snow model showed not only a strong influence of these liquid-containing clouds on melt increase, but also on the increased sublimation <span class="hlt">mass</span> loss. Simulations with the Community Earth System Climate Model for the end of the 21st century (2080-2099) show that Greenland clouds contain more liquid water path and less <span class="hlt">ice</span> water path. This implies that cloud radiative forcing will be further enhanced in the future. Our results therefore urge the need for improving cloud microphysics in climate models, to improve future projections of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> and global sea level rise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10.1965S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10.1965S"><span>Application of GRACE to the assessment of model-based estimates of monthly Greenland <span class="hlt">Ice</span> Sheet <span class="hlt">mass</span> <span class="hlt">balance</span> (2003-2012)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schlegel, Nicole-Jeanne; Wiese, David N.; Larour, Eric Y.; Watkins, Michael M.; Box, Jason E.; Fettweis, Xavier; van den Broeke, Michiel R.</p> <p>2016-09-01</p> <p>Quantifying the Greenland <span class="hlt">Ice</span> Sheet's future contribution to sea level rise is a challenging task that requires accurate estimates of <span class="hlt">ice</span> sheet sensitivity to climate change. Forward <span class="hlt">ice</span> sheet models are promising tools for estimating future <span class="hlt">ice</span> sheet behavior, yet confidence is low because evaluation of historical simulations is challenging due to the scarcity of continental-wide data for model evaluation. Recent advancements in processing of Gravity Recovery and Climate Experiment (GRACE) data using Bayesian-constrained <span class="hlt">mass</span> concentration ("mascon") functions have led to improvements in spatial resolution and noise reduction of monthly global gravity fields. Specifically, the Jet Propulsion Laboratory's JPL RL05M GRACE mascon solution (GRACE_JPL) offers an opportunity for the assessment of model-based estimates of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> (MB) at ˜ 300 km spatial scales. Here, we quantify the differences between Greenland monthly observed MB (GRACE_JPL) and that estimated by state-of-the-art, high-resolution models, with respect to GRACE_JPL and model uncertainties. To simulate the years 2003-2012, we force the <span class="hlt">Ice</span> Sheet System Model (ISSM) with anomalies from three different surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) products derived from regional climate models. Resulting MB is compared against GRACE_JPL within individual mascons. Overall, we find agreement in the northeast and southwest where MB is assumed to be primarily controlled by SMB. In the interior, we find a discrepancy in trend, which we presume to be related to millennial-scale dynamic thickening not considered by our model. In the northwest, seasonal amplitudes agree, but modeled <span class="hlt">mass</span> trends are muted relative to GRACE_JPL. Here, discrepancies are likely controlled by temporal variability in <span class="hlt">ice</span> discharge and other related processes not represented by our model simulations, i.e., hydrological processes and <span class="hlt">ice</span>-ocean interaction. In the southeast, GRACE_JPL exhibits larger seasonal amplitude than predicted by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10.2361N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10.2361N"><span>A daily, 1 km resolution data set of downscaled Greenland <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> <span class="hlt">balance</span> (1958-2015)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Noël, Brice; van de Berg, Willem Jan; Machguth, Horst; Lhermitte, Stef; Howat, Ian; Fettweis, Xavier; van den Broeke, Michiel R.</p> <p>2016-10-01</p> <p>This study presents a data set of daily, 1 km resolution Greenland <span class="hlt">ice</span> sheet (GrIS) surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) covering the period 1958-2015. Applying corrections for elevation, bare <span class="hlt">ice</span> albedo and accumulation bias, the high-resolution product is statistically downscaled from the native daily output of the polar regional climate model RACMO2.3 at 11 km. The data set includes all individual SMB components projected to a down-sampled version of the Greenland <span class="hlt">Ice</span> Mapping Project (GIMP) digital elevation model and <span class="hlt">ice</span> mask. The 1 km mask better resolves narrow ablation zones, valley glaciers, fjords and disconnected <span class="hlt">ice</span> caps. Relative to the 11 km product, the more detailed representation of isolated glaciated areas leads to increased precipitation over the southeastern GrIS. In addition, the downscaled product shows a significant increase in runoff owing to better resolved low-lying marginal glaciated regions. The combined corrections for elevation and bare <span class="hlt">ice</span> albedo markedly improve model agreement with a newly compiled data set of ablation measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120010516','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120010516"><span>Greenland <span class="hlt">Ice</span> Sheet <span class="hlt">Mass</span> <span class="hlt">Balance</span>: Distribution of Increased <span class="hlt">Mass</span> Loss with Climate Warming; 2003-07 Versus 1992-2002</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Li, Jun; Benner, Anita C.; Beckley, Matthew; Cornejo, Helen G.; DiMarzio, John; Giovinetto, Mario B.; Neumann, Thomas A.; Robbins, John; Saba, Jack L.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20120010516'); toggleEditAbsImage('author_20120010516_show'); toggleEditAbsImage('author_20120010516_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20120010516_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20120010516_hide"></p> <p>2011-01-01</p> <p>We derive <span class="hlt">mass</span> changes of the Greenland <span class="hlt">ice</span> sheet (GIS) for 2003-07 from ICESat laser altimetry and compare them with results for 1992-2002 from ERS radar and airborne laser altimetry. The GIS continued to grow inland and thin at the margins during 2003 07, but surface melting and accelerated flow significantly increased the marginal thinning compared with the 1990s. The net <span class="hlt">balance</span> changed from a small loss of 7 plus or minus 3 Gt a 1(sup -1) in the 1990s to 171 plus or minus 4 Gt a (sup -1) for 2003-07, contributing 0.5 mm a(sup -1) to recent global sea-level rise. We divide the derived <span class="hlt">mass</span> changes into two components: (1) from changes in melting and <span class="hlt">ice</span> dynamics and (2) from changes in precipitation and accumulation rate. We use our firn compaction model to calculate the elevation changes driven by changes in both temperature and accumulation rate and to calculate the appropriate density to convert the accumulation-driven changes to <span class="hlt">mass</span> changes. Increased losses from melting and <span class="hlt">ice</span> dynamics (17-206 Gt a(sup-1) are over seven times larger than increased gains from precipitation (10 35 Gt a(sup-1) during a warming period of approximately 2 K (10 a)(sup -1) over the GIS. Above 2000m elevation, the rate of gain decreased from 44 to 28 Gt a(sup-1), while below 2000m the rate of loss increased from 51 to 198 Gt a(sup-1). Enhanced thinning below the equilibrium line on outlet glaciers indicates that increased melting has a significant impact on outlet glaciers, as well as accelerating <span class="hlt">ice</span> flow. Increased thinning at higher elevations appears to be induced by dynamic coupling to thinning at the margins on decadal timescales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhDT........67W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhDT........67W"><span><span class="hlt">Ice</span>-atmosphere interactions in the Canadian High Arctic: Implications for the thermo-mechanical evolution of terrestrial <span class="hlt">ice</span> <span class="hlt">masses</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wohlleben, Trudy M. H.</p> <p></p> <p>Canadian High Arctic terrestrial <span class="hlt">ice</span> <span class="hlt">masses</span> and the polar atmosphere evolve codependently, and interactions between the two systems can lead to feedbacks, positive and negative. The two primary positive cryosphere-atmosphere feedbacks are: (1) The snow/<span class="hlt">ice</span>-albedo feedback (where area changes in snow and/or <span class="hlt">ice</span> cause changes in surface albedo and surface air temperatures, leading to further area changes in snow/<span class="hlt">ice</span>); and (2) The elevation - <span class="hlt">mass</span> <span class="hlt">balance</span> feedback (where thickness changes in terrestrial <span class="hlt">ice</span> <span class="hlt">masses</span> cause changes to atmospheric circulation and precipitation patterns, leading to further <span class="hlt">ice</span> thickness changes). In this thesis, numerical experiments are performed to: (1) quantify the magnitudes of the two feedbacks for chosen Canadian High Arctic terrestrial <span class="hlt">ice</span> <span class="hlt">masses</span>; and (2) to examine the direct and indirect consequences of surface air temperature changes upon englacial temperatures with implications for <span class="hlt">ice</span> flow, <span class="hlt">mass</span> flux divergence, and topographic evolution. Model results show that: (a) for John Evans Glacier, Ellesmere Island, the magnitude of the terrestrial snow/<span class="hlt">ice</span>-albedo feedback can locally exceed that of sea <span class="hlt">ice</span> on less than decadal timescales, with implications for glacier response times to climate perturbations; (b) although historical air temperature changes might be the direct cause of measured englacial temperature anomalies in various glacier and <span class="hlt">ice</span> cap accumulation zones, they can also be the indirect cause of their enhanced diffusive loss; (c) while the direct result of past air temperature changes has been to cool the interior of John Evans Glacier, and its bed, the indirect result has been to create and maintain warm (pressure melting point) basal temperatures in the ablation zone; and (d) for Devon <span class="hlt">Ice</span> Cap, observed <span class="hlt">mass</span> gains in the northwest sector of the <span class="hlt">ice</span> cap would be smaller without orographic precipitation and the <span class="hlt">mass</span> <span class="hlt">balance</span>---elevation feedback, supporting the hypothesis that this feedback is playing a role in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1912332S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1912332S"><span>Geodetic glacier <span class="hlt">mass</span> <span class="hlt">balancing</span> on <span class="hlt">ice</span> caps - inseparably connected to firn modelling?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saß, Björn L.; Sauter, Tobias; Seehaus, Thorsten; Braun, Matthias H.</p> <p>2017-04-01</p> <p>Observed melting of glaciers and <span class="hlt">ice</span> caps in the polar regions contribute to the ongoing global sea level rise (SLR). A rising sea level and its consequences are one of the major challenges for coastal societies in the next decades to centuries. Gaining knowledge about the main drivers of SLR and bringing it together is one recent key-challenge for environmental science. The high arctic Svalbard archipelago faced a strong climatic change in the last decades, associated with a change in the cryosphere. Vestfonna, a major Arctic <span class="hlt">ice</span> cap in the north east of Svalbard, harbors land and marine terminating glaciers, which expose a variability of behavior. We use high resolution remote sensing data from space-borne radar (TanDEM-X, TerraSAR-X, Sentinel-1a), acquired between 2009 and 2015, to estimate glacier velocity and high accurate surface elevation changes. For DEM registration we use space-borne laser altimetry (ICESat) and an existing in-situ data archive (IPY Kinnvika). In order to separate individual glacier basin changes for a detailed <span class="hlt">mass</span> <span class="hlt">balance</span> study and for further SLR contribution estimates, we use glacier outlines from the Global Land <span class="hlt">Ice</span> Measurements from Space (GLIMS) project. Remaining challenges of space-borne observations are the reduction of measurement uncertainties, in the case of Synthetic Aperture Radar most notably signal penetration into the glacier surface. Furthermore, in order to convert volume to <span class="hlt">mass</span> change one has to use the density of the changed <span class="hlt">mass</span> (conversion factor) and one has to account for the <span class="hlt">mass</span> conservation processes in the firn package (firn compaction). Both, the conversion factor and the firn compaction are not (yet) measurable for extensive <span class="hlt">ice</span> bodies. They have to be modelled by coupling point measurements and regional gridded climate data. Results indicate a slight interior thickening contrasted with wide spread thinning in the ablation zone of the marine terminating outlets. While one glacier system draining to the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12..811N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12..811N"><span>Modelling the climate and surface <span class="hlt">mass</span> <span class="hlt">balance</span> of polar <span class="hlt">ice</span> sheets using RACMO2 - Part 1: Greenland (1958-2016)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Noël, Brice; van de Berg, Willem Jan; Melchior van Wessem, J.; van Meijgaard, Erik; van As, Dirk; Lenaerts, Jan T. M.; Lhermitte, Stef; Kuipers Munneke, Peter; Smeets, C. J. P. Paul; van Ulft, Lambertus H.; van de Wal, Roderik S. W.; van den Broeke, Michiel R.</p> <p>2018-03-01</p> <p>We evaluate modelled Greenland <span class="hlt">ice</span> sheet (GrIS) near-surface climate, surface energy <span class="hlt">balance</span> (SEB) and surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) from the updated regional climate model RACMO2 (1958-2016). The new model version, referred to as RACMO2.3p2, incorporates updated glacier outlines, topography and <span class="hlt">ice</span> albedo fields. Parameters in the cloud scheme governing the conversion of cloud condensate into precipitation have been tuned to correct inland snowfall underestimation: snow properties are modified to reduce drifting snow and melt production in the <span class="hlt">ice</span> sheet percolation zone. The <span class="hlt">ice</span> albedo prescribed in the updated model is lower at the <span class="hlt">ice</span> sheet margins, increasing <span class="hlt">ice</span> melt locally. RACMO2.3p2 shows good agreement compared to in situ meteorological data and point SEB/SMB measurements, and better resolves the spatial patterns and temporal variability of SMB compared with the previous model version, notably in the north-east, south-east and along the K-transect in south-western Greenland. This new model version provides updated, high-resolution gridded fields of the GrIS present-day climate and SMB, and will be used for projections of the GrIS climate and SMB in response to a future climate scenario in a forthcoming study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C13D0861C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C13D0861C"><span>High Artic Glaciers and <span class="hlt">Ice</span> Caps <span class="hlt">Ice</span> <span class="hlt">Mass</span> Change from GRACE, Regional Climate Model Output and Altimetry.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ciraci, E.; Velicogna, I.; Fettweis, X.; van den Broeke, M. R.</p> <p>2016-12-01</p> <p>The Arctic hosts more than the 75% of the <span class="hlt">ice</span> covered regions outside from Greenland and Antarctica. Available observations show that increased atmospheric temperatures during the last century have contributed to a substantial glaciers retreat in all these regions. We use satellite gravimetry by the NASA's Gravity Recovery and Climate Experiment (GRACE), and apply a least square fit mascon approach to calculate time series of <span class="hlt">ice</span> <span class="hlt">mass</span> change for the period 2002-2016. Our estimates show that arctic glaciers have constantly contributed to the sea level rise during the entire observation period with a <span class="hlt">mass</span> change of -170+/-20 Gt/yr equivalent to the 80% of the total <span class="hlt">ice</span> <span class="hlt">mass</span> change from the world Glacier and <span class="hlt">Ice</span> Caps (GIC) excluding the <span class="hlt">Ice</span> sheet peripheral GIC, which we calculated to be -215+/-32 GT/yr, with an acceleration of 9+/-4 Gt/yr2. The Canadian Archipelago is the main contributor to the total <span class="hlt">mass</span> depletion with an <span class="hlt">ice</span> <span class="hlt">mass</span> trend of -73+/-9 Gt/yr and a significant acceleration of -7+/-3 Gt/yr2. The increasing <span class="hlt">mass</span> loss is mainly determined by melting glaciers located in the northern part of the archipelago.In order to investigate the physical processes driving the observed <span class="hlt">ice</span> <span class="hlt">mass</span> loss we employ satellite altimetry and surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) estimates from Regional climate model outputs available for the same time period covered by the gravimetry data. We use elevation data from the NASA ICESat (2003-2009) and ESA CryoSat-2 (2010-2016) missions to estimate <span class="hlt">ice</span> elevation changes. We compare GRACE <span class="hlt">ice</span> <span class="hlt">mass</span> estimates with time series of surface <span class="hlt">mass</span> <span class="hlt">balance</span> from the Regional Climate Model (RACMO-2) and the Modèle Atmosphérique Régional (MAR) and determine the portion of the total <span class="hlt">mass</span> change explained by the SMB signal. We find that in Iceland and in the and the Canadian Archipelago the SMB signal explains most of the observed <span class="hlt">mass</span> changes, suggesting that <span class="hlt">ice</span> discharge may play a secondary role here. In other region, e.g. in Svalbar, the SMB signal</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110015161','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110015161"><span>Thickening and Thinning of Antarctic <span class="hlt">Ice</span> Shelves and Tongues and <span class="hlt">Mass</span> <span class="hlt">Balance</span> Estimates</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Li, Jun; Giovinetto, Mario; Robbins, John; Saba, Jack L.; Yi, Donghui</p> <p>2011-01-01</p> <p>Previous analysis of elevation changes for 1992 to 2002 obtained from measurements by radar altimeters on ERS-l and 2 showed that the shelves in the Antarctic Peninsula (AP) and along the coast of West Antarctica (WA), including the eastern part of the Ross <span class="hlt">Ice</span> Shelf, were mostly thinning and losing <span class="hlt">mass</span> whereas the Ronne <span class="hlt">Ice</span> shelf also in WA was mostly thickening. The estimated total <span class="hlt">mass</span> loss for the floating <span class="hlt">ice</span> shelves and <span class="hlt">ice</span> tongues from <span class="hlt">ice</span> draining WA and the AP was 95 Gt/a. In contrast, the floating <span class="hlt">ice</span> shelves and <span class="hlt">ice</span> tongues from <span class="hlt">ice</span> draining East Antarctica (EA), including the Filchner, Fimbul, Amery, and Western Ross, were mostly thickening with a total estimated <span class="hlt">mass</span> gain of 142 Gt/a. Data from ICESat laser altimetry for 2003-2008 gives new surface elevation changes (dH/dt) with some similar values for the earlier and latter periods, including -27.6 and -26.9 cm a-Ion the West Getz <span class="hlt">ice</span> shelf and -42.4 and - 27.2 cm/a on the East Getz <span class="hlt">ice</span> shelf, and some values that indicate more thinning in the latter period, including -17.9 and -36.2 cm/a on the Larsen C <span class="hlt">ice</span> shelf, -35.5 and -76.0 cm/a on the Pine Island Glacier floating, -60.5 and -125.7 .cm/a on the Smith Glacier floating, and -34.4 and -108.9 cm/a on the Thwaites Glacier floating. Maps of measured dH/dt and estimated thickness change are produced along with <span class="hlt">mass</span> change estimates for 2003 - 2008.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C41E0718L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C41E0718L"><span>Firn Thickness Changes (1982-2015) Driven by SMB from MERRA-2, RACMO2.3, ERA-Int and AVHRR Surface Temperature and the Impacts to Greenland <span class="hlt">Ice</span> Sheet <span class="hlt">Mass</span> <span class="hlt">Balance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, J.; Medley, B.; Neumann, T.; Smith, B. E.; Luthcke, S. B.; Zwally, H. J.</p> <p>2016-12-01</p> <p>Surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) data are essential in the derivation of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span>. This is because <span class="hlt">ice</span> sheet <span class="hlt">mass</span> change consists of short-term and long-term variations. The short-term variations are directly given by the SMB data. For altimetry based <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> studies, these short-term <span class="hlt">mass</span> changes are converted to firn thickness changes by using a firn densification-elevation model, and then the variations are subtracted from the altimetry measurements to give the long-term <span class="hlt">ice</span> thickness changes that are associated with the density of <span class="hlt">ice</span>. So far various SMB data sets such as ERA-Interim, RACMO and MERRA are available and some have been widely used in large number of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> studies. However theses data sets exhibit the clear discrepancies in both random and systematic manner. In this study, we use our time dependent firn densification- elevation model, driven by the SMB data from MERRA-2, RACMO2.3 and ERA-Int for the period of 1982-2015 and the temperature variations from AVHRR for the same period to examine the corresponding firn thickness variations and the impacts to the <span class="hlt">mass</span> changes over the Greenland <span class="hlt">ice</span> sheet. The model was initialized with the1980's climate. Our results show that the relative smaller (centimeter level) differences in the firn thickness driven by the different data set occur at the early stage (1980's) of the model run. As the time progressing, the discrepancies between the SMB data sets accumulate, and the corresponding firn thickness differences quickly become larger with the value > 2m at the end of the period. Although the overall rates for the whole period driven by each of the three data sets are small ranging -0.2 - 0.2 cm a-1 (-3.0-2.7 Gt a-1), the decadal rates can vary greatly with magnitude > 3 cm a-1 and the impact to the Greenland <span class="hlt">mass</span> change exceeds 30 Gt a-1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C21D0667A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C21D0667A"><span>An Analysis of <span class="hlt">Mass</span> <span class="hlt">Balance</span> of Chilean Glaciers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ambinakudige, S.; Tetteh, L.</p> <p>2013-12-01</p> <p>Glaciers in Chile range from very small glacierets found on the isolated volcanoes of northern Chile to the 13,000 sq.km Southern Patagonian <span class="hlt">Ice</span> Field. Regular monitoring of these glaciers is very important as they are considered as sensitive indicators of climate change. Millions of people's lives are dependent on these glaciers for fresh water and irrigation purpose. In this study, <span class="hlt">mass</span> <span class="hlt">balances</span> of several Chilean glaciers were estimated using Aster satellite images between 2007 and 2012. Highly accurate DEMs were created with supplementary information from <span class="hlt">Ice</span>Sat data. The result indicated a negative <span class="hlt">mass</span> <span class="hlt">balance</span> for many glaciers indicating the need for further monitoring of glaciers in the Andes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_4 --> <div id="page_5" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="81"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012TCD.....6.5225G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012TCD.....6.5225G"><span>A <span class="hlt">balanced</span> water layer concept for subglacial hydrology in large scale <span class="hlt">ice</span> sheet models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goeller, S.; Thoma, M.; Grosfeld, K.; Miller, H.</p> <p>2012-12-01</p> <p>There is currently no doubt about the existence of a wide-spread hydrological network under the Antarctic <span class="hlt">ice</span> sheet, which lubricates the <span class="hlt">ice</span> base and thus leads to increased <span class="hlt">ice</span> velocities. Consequently, <span class="hlt">ice</span> models should incorporate basal hydrology to obtain meaningful results for future <span class="hlt">ice</span> dynamics and their contribution to global sea level rise. Here, we introduce the <span class="hlt">balanced</span> water layer concept, covering two prominent subglacial hydrological features for <span class="hlt">ice</span> sheet modeling on a continental scale: the evolution of subglacial lakes and <span class="hlt">balance</span> water fluxes. We couple it to the thermomechanical <span class="hlt">ice</span>-flow model RIMBAY and apply it to a synthetic model domain inspired by the Gamburtsev Mountains, Antarctica. In our experiments we demonstrate the dynamic generation of subglacial lakes and their impact on the velocity field of the overlaying <span class="hlt">ice</span> sheet, resulting in a negative <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>. Furthermore, we introduce an elementary parametrization of the water flux-basal sliding coupling and reveal the predominance of the <span class="hlt">ice</span> loss through the resulting <span class="hlt">ice</span> streams against the stabilizing influence of less hydrologically active areas. We point out, that established <span class="hlt">balance</span> flux schemes quantify these effects only partially as their ability to store subglacial water is lacking.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45..789I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45..789I"><span>Contribution of Deformation to Sea <span class="hlt">Ice</span> <span class="hlt">Mass</span> <span class="hlt">Balance</span>: A Case Study From an N-<span class="hlt">ICE</span>2015 Storm</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Itkin, Polona; Spreen, Gunnar; Hvidegaard, Sine Munk; Skourup, Henriette; Wilkinson, Jeremy; Gerland, Sebastian; Granskog, Mats A.</p> <p>2018-01-01</p> <p>The fastest and most efficient process of gaining sea <span class="hlt">ice</span> volume is through the mechanical redistribution of <span class="hlt">mass</span> as a consequence of deformation events. During the <span class="hlt">ice</span> growth season divergent motion produces leads where new <span class="hlt">ice</span> grows thermodynamically, while convergent motion fractures the <span class="hlt">ice</span> and either piles the resultant <span class="hlt">ice</span> blocks into ridges or rafts one floe under the other. Here we present an exceptionally detailed airborne data set from a 9 km2 area of first year and second year <span class="hlt">ice</span> in the Transpolar Drift north of Svalbard that allowed us to estimate the redistribution of <span class="hlt">mass</span> from an observed deformation event. To achieve this level of detail we analyzed changes in sea <span class="hlt">ice</span> freeboard acquired from two airborne laser scanner surveys just before and right after a deformation event brought on by a passing low-pressure system. A linear regression model based on divergence during this storm can explain 64% of freeboard variability. Over the survey region we estimated that about 1.3% of level sea <span class="hlt">ice</span> volume was pressed together into deformed <span class="hlt">ice</span> and the new <span class="hlt">ice</span> formed in leads in a week after the deformation event would increase the sea <span class="hlt">ice</span> volume by 0.5%. As the region is impacted by about 15 storms each winter, a simple linear extrapolation would result in about 7% volume increase and 20% deformed <span class="hlt">ice</span> fraction at the end of the season.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70155990','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70155990"><span>Surface melt dominates Alaska glacier <span class="hlt">mass</span> <span class="hlt">balance</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Larsen Chris F,; Burgess, E; Arendt, A.A.; O'Neel, Shad; Johnson, A.J.; Kienholz, C.</p> <p>2015-01-01</p> <p>Mountain glaciers comprise a small and widely distributed fraction of the world's terrestrial <span class="hlt">ice</span>, yet their rapid losses presently drive a large percentage of the cryosphere's contribution to sea level rise. Regional <span class="hlt">mass</span> <span class="hlt">balance</span> assessments are challenging over large glacier populations due to remote and rugged geography, variable response of individual glaciers to climate change, and episodic calving losses from tidewater glaciers. In Alaska, we use airborne altimetry from 116 glaciers to estimate a regional <span class="hlt">mass</span> <span class="hlt">balance</span> of −75 ± 11 Gt yr−1 (1994–2013). Our glacier sample is spatially well distributed, yet pervasive variability in <span class="hlt">mass</span> <span class="hlt">balances</span> obscures geospatial and climatic relationships. However, for the first time, these data allow the partitioning of regional <span class="hlt">mass</span> <span class="hlt">balance</span> by glacier type. We find that tidewater glaciers are losing <span class="hlt">mass</span> at substantially slower rates than other glaciers in Alaska and collectively contribute to only 6% of the regional <span class="hlt">mass</span> loss.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012cosp...39...44A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012cosp...39...44A"><span>Remote Sensing of Cryosphere: Estimation of <span class="hlt">Mass</span> <span class="hlt">Balance</span> Change in Himalayan Glaciers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ambinakudige, Shrinidhi; Joshi, Kabindra</p> <p>2012-07-01</p> <p>Glacial changes are an important indicator of climate change. Our understanding <span class="hlt">mass</span> <span class="hlt">balance</span> change in Himalayan glaciers is limited. This study estimates <span class="hlt">mass</span> <span class="hlt">balance</span> of some major glaciers in the Sagarmatha National Park (SNP) in Nepal using remote sensing applications. Remote sensing technique to measure <span class="hlt">mass</span> <span class="hlt">balance</span> of glaciers is an important methodological advance in the highly rugged Himalayan terrain. This study uses ASTER VNIR, 3N (nadir view) and 3B (backward view) bands to generate Digital Elevation Models (DEMs) for the SNP area for the years 2002, 2003, 2004 and 2005. Glacier boundaries were delineated using combination of boundaries available in the Global land <span class="hlt">ice</span> measurement (GLIMS) database and various band ratios derived from ASTER images. Elevation differences, glacial area, and <span class="hlt">ice</span> densities were used to estimate the change in <span class="hlt">mass</span> <span class="hlt">balance</span>. The results indicated that the rate of glacier <span class="hlt">mass</span> <span class="hlt">balance</span> change was not uniform across glaciers. While there was a decrease in <span class="hlt">mass</span> <span class="hlt">balance</span> of some glaciers, some showed increase. This paper discusses how each glacier in the SNP area varied in its annual <span class="hlt">mass</span> <span class="hlt">balance</span> measurement during the study period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ISPAr41B8..481B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ISPAr41B8..481B"><span><span class="hlt">Mass</span> <span class="hlt">Balance</span> Changes and <span class="hlt">Ice</span> Dynamics of Greenland and Antarctic <span class="hlt">Ice</span> Sheets from Laser Altimetry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Babonis, G. S.; Csatho, B.; Schenk, T.</p> <p>2016-06-01</p> <p>During the past few decades the Greenland and Antarctic <span class="hlt">ice</span> sheets have lost <span class="hlt">ice</span> at accelerating rates, caused by increasing surface temperature. The melting of the two big <span class="hlt">ice</span> sheets has a big impact on global sea level rise. If the <span class="hlt">ice</span> sheets would melt down entirely, the sea level would rise more than 60 m. Even a much smaller rise would cause dramatic damage along coastal regions. In this paper we report about a major upgrade of surface elevation changes derived from laser altimetry data, acquired by NASA's <span class="hlt">Ice</span>, Cloud and land Elevation Satellite mission (ICESat) and airborne laser campaigns, such as Airborne Topographic Mapper (ATM) and Land, Vegetation and <span class="hlt">Ice</span> Sensor (LVIS). For detecting changes in <span class="hlt">ice</span> sheet elevations we have developed the Surface Elevation Reconstruction And Change detection (SERAC) method. It computes elevation changes of small surface patches by keeping the surface shape constant and considering the absolute values as surface elevations. We report about important upgrades of earlier results, for example the inclusion of local <span class="hlt">ice</span> caps and the temporal extension from 1993 to 2014 for the Greenland <span class="hlt">Ice</span> Sheet and for a comprehensive reconstruction of <span class="hlt">ice</span> thickness and <span class="hlt">mass</span> changes for the Antarctic <span class="hlt">Ice</span> Sheets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/7061','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/7061"><span>Columbia Glacier stake location, <span class="hlt">mass</span> <span class="hlt">balance</span>, glacier surface altitude, and <span class="hlt">ice</span> radar data, 1978 measurement year</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Mayo, L.R.; Trabant, D.C.; March, Rod; Haeberli, Wilfried</p> <p>1979-01-01</p> <p>A 1 year data-collection program on Columbia Glacier, Alaska has produced a data set consisting of near-surface <span class="hlt">ice</span> kinematics, <span class="hlt">mass</span> <span class="hlt">balance</span>, and altitude change at 57 points and 34 <span class="hlt">ice</span> radar soundings. These data presented in two tables, are part of the basic data required for glacier dynamic analysis, computer models, and predictions of the number and size of icebergs which Columbia Glacier will calve into shipping lanes of eastern Prince William Sound. A metric, sea-level coordinate system was developed for use in surveying throughout the basin. Its use is explained and monument coordinates listed. A series of seven integrated programs for calculators were used in both the field and office to reduce the surveying data. These programs are thoroughly documented and explained in the report. (Kosco-USGS)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.2985B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.2985B"><span>50 years of <span class="hlt">mass</span> <span class="hlt">balance</span> observations at Vernagtferner, Eastern Alps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Braun, Ludwig; Mayer, Christoph</p> <p>2016-04-01</p> <p>The determination and monitoring of the seasonal and annual glacier <span class="hlt">mass</span> <span class="hlt">balances</span> of Vernagtferner, Austria, started in 1964 by the Commission of Glaciology, Bavarian Academy of Sciences. Detailed and continuous climate- and runoff measurements complement this <span class="hlt">mass</span> <span class="hlt">balance</span> series since 1974. Vernagtferner attracted the attention of scientists since the beginning of the 17th century due to its rapid advances and the resulting glacier lake outburst floods in the Ötztal valley. This is one reason for the first photogrammetric survey in 1889, which was followed by frequent topographic surveys, adding up to more than ten digital elevation models of the glacier until today. By including the known maximum glacier extent at the end of the Little <span class="hlt">Ice</span> Age in 1845, the geodetic glacier volume <span class="hlt">balances</span> cover a time span of almost 170 years. The 50 years of glacier <span class="hlt">mass</span> <span class="hlt">balance</span> and 40 years of water <span class="hlt">balance</span> in the drainage basin are therefore embedded in a considerably longer period of glacier evolution, allowing an interpretation within an extended frame of climatology and <span class="hlt">ice</span> dynamics. The direct <span class="hlt">mass</span> <span class="hlt">balance</span> observations cover not only the period of alpine-wide strong glacier <span class="hlt">mass</span> loss since the beginning of the 1990s. The data also contain the last period of glacier advances between 1970 and 1990. The combination of the observed surface <span class="hlt">mass</span> exchange and the determined periodic volumetric changes allows a detailed analysis of the dynamic reaction of the glacier over the period of half a century. The accompanying meteorological observations are the basis for relating these reactions to the climatic changes during this period. Vernagtferner is therefore one of the few glaciers in the world, where a very detailed glacier-climate reaction was observed for many decades and can be realistically reconstructed back to the end of the Little <span class="hlt">Ice</span> Age.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1352361-present-day-future-antarctic-ice-sheet-climate-surface-mass-balance-community-earth-system-model','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1352361-present-day-future-antarctic-ice-sheet-climate-surface-mass-balance-community-earth-system-model"><span>Present-day and future Antarctic <span class="hlt">ice</span> sheet climate and surface <span class="hlt">mass</span> <span class="hlt">balance</span> in the Community Earth System Model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Lenaerts, Jan T. M.; Vizcaino, Miren; Fyke, Jeremy Garmeson; ...</p> <p>2016-02-01</p> <p>Here, we present climate and surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) of the Antarctic <span class="hlt">ice</span> sheet (AIS) as simulated by the global, coupled ocean–atmosphere–land Community Earth System Model (CESM) with a horizontal resolution of ~1° in the past, present and future (1850–2100). CESM correctly simulates present-day Antarctic sea <span class="hlt">ice</span> extent, large-scale atmospheric circulation and near-surface climate, but fails to simulate the recent expansion of Antarctic sea <span class="hlt">ice</span>. The present-day Antarctic <span class="hlt">ice</span> sheet SMB equals 2280 ± 131Gtyear –1, which concurs with existing independent estimates of AIS SMB. When forced by two CMIP5 climate change scenarios (high mitigation scenario RCP2.6 and high-emission scenariomore » RCP8.5), CESM projects an increase of Antarctic <span class="hlt">ice</span> sheet SMB of about 70 Gtyear –1 per degree warming. This increase is driven by enhanced snowfall, which is partially counteracted by more surface melt and runoff along the <span class="hlt">ice</span> sheet’s edges. This intensifying hydrological cycle is predominantly driven by atmospheric warming, which increases (1) the moisture-carrying capacity of the atmosphere, (2) oceanic source region evaporation, and (3) summer AIS cloud liquid water content.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120002071','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120002071"><span>Analysis of Antarctic <span class="hlt">Ice</span>-Sheet <span class="hlt">Mass</span> <span class="hlt">Balance</span> from ICESat Measurements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Li, Jun; Robbins, John; Saba, Jack L.; Yi, Donghui</p> <p>2011-01-01</p> <p>If protoplanets formed from 10 to 20 kilometer diameter planetesimals in a runaway accretion process prior to their oligarchic growth into the terrestrial planets, it is only logical to ask where these planetesimals may have formed in order to assess the initial composition of the Earth. We have used Weidenschilling's model for the formation of comets (1997) to calculate an efficiency factor for the formation of planetesimals from the solar nebula, then used this factor to calculate the feeding zones that contribute to material contained within 10, 15 and 20 kilometer diameter planetesimals at 1 A.V. as a function of nebular <span class="hlt">mass</span>. We find that for all reasonable nebular <span class="hlt">masses</span>, these planetesimals contain a minimum of 3% water as <span class="hlt">ice</span> by <span class="hlt">mass</span>. The fraction of <span class="hlt">ice</span> increases as the planetesimals increase in size and as the nebular <span class="hlt">mass</span> decreases, since both factors increase the feeding zones from which solids in the final planetesimals are drawn. Is there really a problem with the current accretion scenario that makes the Earth too dry, or is it possible that the nascent Earth lost significant quantities of water in the final stages of accretion?</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24910517','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24910517"><span>A century of variation in the dependence of Greenland iceberg calving on <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> <span class="hlt">balance</span> and regional climate change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bigg, G R; Wei, H L; Wilton, D J; Zhao, Y; Billings, S A; Hanna, E; Kadirkamanathan, V</p> <p>2014-06-08</p> <p>Iceberg calving is a major component of the total <span class="hlt">mass</span> <span class="hlt">balance</span> of the Greenland <span class="hlt">ice</span> sheet (GrIS). A century-long record of Greenland icebergs comes from the International <span class="hlt">Ice</span> Patrol's record of icebergs (I48N) passing latitude 48° N, off Newfoundland. I48N exhibits strong interannual variability, with a significant increase in amplitude over recent decades. In this study, we show, through a combination of nonlinear system identification and coupled ocean-iceberg modelling, that I48N's variability is predominantly caused by fluctuation in GrIS calving discharge rather than open ocean iceberg melting. We also demonstrate that the episodic variation in iceberg discharge is strongly linked to a nonlinear combination of recent changes in the surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) of the GrIS and regional atmospheric and oceanic climate variability, on the scale of the previous 1-3 years, with the dominant causal mechanism shifting between glaciological (SMB) and climatic (ocean temperature) over time. We suggest that this is a change in whether glacial run-off or under-<span class="hlt">ice</span> melting is dominant, respectively. We also suggest that GrIS calving discharge is episodic on at least a regional scale and has recently been increasing significantly, largely as a result of west Greenland sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33C1211G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33C1211G"><span>Is snow-<span class="hlt">ice</span> now a major contributor to sea <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> in the western Transpolar Drift region?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Graham, R. M.; Merkouriadi, I.; Cheng, B.; Rösel, A.; Granskog, M. A.</p> <p>2017-12-01</p> <p>During the Norwegian young sea <span class="hlt">ICE</span> (N-<span class="hlt">ICE</span>2015) campaign, which took place in the first half of 2015 north of Svalbard, a deep winter snow pack (50 cm) on sea <span class="hlt">ice</span> was observed, that was 50% thicker than earlier climatological studies suggested for this region. Moreover, a significant fraction of snow contributed to the total <span class="hlt">ice</span> <span class="hlt">mass</span> in second-year <span class="hlt">ice</span> (SYI) (9% on average). Interestingly, very little snow (3% snow by <span class="hlt">mass</span>) was present in first-year <span class="hlt">ice</span> (FYI). The combination of sea <span class="hlt">ice</span> thinning and increased precipitation north of Svalbard is expected to promote the formation of snow-<span class="hlt">ice</span>. Here we use the 1-D snow/<span class="hlt">ice</span> thermodynamic model HIGHTSI forced with reanalysis data, to show that for the case study of N-<span class="hlt">ICE</span>2015, snow-<span class="hlt">ice</span> would even form over SYI with an initial thickness of 2 m. In current conditions north of Svalbard, snow-<span class="hlt">ice</span> is ubiquitous and contributes to the thickness growth up to 30%. This contribution is important, especially in the absence of any bottom thermodynamic growth due to the thick insulating snow cover. Growth of FYI north of Svalbard is mainly controlled by the timing of growth onset relative to snow precipitation events and cold spells. These usually short-lived conditions are largely determined by the frequency of storms entering the Arctic from the Atlantic Ocean. In our case, a later freeze onset was favorable for FYI growth due to less snow accumulation in early autumn. This limited snow-<span class="hlt">ice</span> formation but promoted bottom thermodynamic growth. We surmise these findings are related to a regional phenomenon in the Atlantic sector of the Arctic, with frequent storm events which bring increasing amounts of precipitation in autumn and winter, and also affect the duration of cold temperatures required for <span class="hlt">ice</span> growth in winter. We discuss the implications for the importance of snow-<span class="hlt">ice</span> in the future Arctic, formerly believed to be non-existent in the central Arctic due to thick perennial <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMGC21A0718P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMGC21A0718P"><span>The Thermal Circulation on Kilimanjaro, Tanzania and its Relevance to Summit <span class="hlt">Ice</span>-Field <span class="hlt">Mass</span> <span class="hlt">Balance</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pepin, N. C.; Duane, W. J.</p> <p>2008-12-01</p> <p>It is well known that mountains create their own climates. On Kilimanjaro, which is the tallest free standing mountain in Africa, the intense tropical sunlight generates a strong diurnal mountain circulation which transports moisture up the mountain during the day and back downslope at night. This process has strong consequences for development of cloud cover, precipitation, and hence <span class="hlt">ice</span>-field <span class="hlt">mass</span> <span class="hlt">balance</span> on the summit crater. We compare surface climate (temperature, moisture and wind) measured at ten elevations on Kilimanjaro, with equivalent observations in the free atmosphere from NCEP/NCAR reanalysis data for September 2004 to July 2008. There are no simple temporal trends over this period in either surface of free- air data. Correlations between daily surface and free air temperatures are greatest below 2500 metres, meaning that synoptic (inter-diurnal) variability is the major control here. In contrast, temperatures and moisture on the higher slopes above treeline (about 3000 m) are strongly decoupled from the free atmosphere, showing intense heating/cooling by day/night (more than 5°C). The sparsely vegetated upper slopes are the focus for the most intense heating and upslope winds develop by mid-morning. The forest on the lower slopes acts as a moisture source, with large vapour pressure excesses reported (5 mb) which move upslope reaching the crater in the afternoon before subsiding downslope at night. The montane thermal circulation is more effective at upslope moisture transport during January as compared with July. Fluctuations in upper air flow strength and direction (at 500 mb) surprisingly have limited influence on the strength of surface heating and upslope moisture advection. This finding suggests that local changes in surface characteristics such as deforestation could have a strong influence on the mountain climate and the summit <span class="hlt">ice</span> fields on Kilimanjaro, and make <span class="hlt">mass-balance</span> somewhat divorced from larger-scale advective changes associated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ERL....12b4016M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ERL....12b4016M"><span><span class="hlt">Mass</span> budget of the glaciers and <span class="hlt">ice</span> caps of the Queen Elizabeth Islands, Canada, from 1991 to 2015</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Millan, Romain; Mouginot, Jeremie; Rignot, Eric</p> <p>2017-02-01</p> <p>Recent studies indicate that the glaciers and <span class="hlt">ice</span> caps in Queen Elizabeth Islands (QEI), Canada have experienced an increase in <span class="hlt">ice</span> <span class="hlt">mass</span> loss during the last two decades, but the contribution of <span class="hlt">ice</span> dynamics to this loss is not well known. We present a comprehensive mapping of <span class="hlt">ice</span> velocity using a suite of satellite data from year 1991 to 2015, combined with <span class="hlt">ice</span> thickness data from NASA Operation <span class="hlt">Ice</span>Bridge, to calculate <span class="hlt">ice</span> discharge. We find that <span class="hlt">ice</span> discharge increased significantly after 2011 in Prince of Wales Icefield, maintained or decreased in other sectors, whereas glacier surges have little impact on long-term trends in <span class="hlt">ice</span> discharge. During 1991-2005, the QEI <span class="hlt">mass</span> loss averaged 6.3 ± 1.1 Gt yr-1, 52% from <span class="hlt">ice</span> discharge and the rest from surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB). During 2005-2014, the <span class="hlt">mass</span> loss from <span class="hlt">ice</span> discharge averaged 3.5 ± 0.2 Gt yr-1 (10%) versus 29.6 ± 3.0 Gt yr-1 (90%) from SMB. SMB processes therefore dominate the QEI <span class="hlt">mass</span> <span class="hlt">balance</span>, with <span class="hlt">ice</span> dynamics playing a significant role only in a few basins.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27..628S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27..628S"><span>Energy and <span class="hlt">Mass</span> <span class="hlt">Balance</span> At Gran Campo Nevado, Patagonia, Chile</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schneider, C.; Kilian, R.; Casassa, G.</p> <p></p> <p>The Gran Campo Nevado (GCN) <span class="hlt">Ice</span> Cap on Peninsula Muñoz Gamero, Chile, is lo- cated in the southernmost part of the Patagonian Andes at 53S. It comprises an <span class="hlt">ice</span> cap and numerous outlet glaciers which mostly end in proglacial lakes at sea level. The total <span class="hlt">ice</span> covered area sums up to approximately 250 km2. GCN forms the only major <span class="hlt">ice</span> body between the Southern Patagonian Icefield and the Street of Magallan. Its almost unique location in the zone of the all-year westerlies makes it a region of key interest in terms of glacier and climate change studies of the westwind zone of the Southern Hemisphere. Mean annual temperature of approximately +5C at sea level and high precipitation of about 8.000 mm per year lead to an extreme turn-over of <span class="hlt">ice</span> <span class="hlt">mass</span> from the accumulation area of the GCN <span class="hlt">Ice</span> Cap to the ablation areas of the outlet glaciers. Since October 1999 an automated weather station (AWS) is run continuously in the area at Bahia Bahamondes for monitoring climate parameters. From February to April 2000 an additional AWS was operated on Glaciar Lengua a small outlet glacier of GCN to the north-west. Ablation has been measured at stakes during the same pe- riod. The aim of this study, was to obtain point energy and <span class="hlt">mass</span> <span class="hlt">balance</span> on Glaciar Lengua. The work was conducted as part of the international and interdisciplinary working group SGran Campo NevadoT and supported by the German Research Foun- & cedil;dation (DFG). Energy <span class="hlt">balance</span> was calculated using the bulk approach formulas and calibrated to the measured ablation. It turns out, that sensible heat transfer is the major contribution to the energy <span class="hlt">balance</span>. Since high cloud cover rates prevail, air tempera- ture is the key factor for the energy <span class="hlt">balance</span> of the glacier. Despite high rain fall rates, energy input from rain fall is of only minor importance to the overall energy <span class="hlt">balance</span>. From the energy <span class="hlt">balance</span> computed, it was possible to derive summer-time degree-day factors for Glaciar Lengua. With data from the nearby</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.1177S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.1177S"><span>Glacier <span class="hlt">mass</span> <span class="hlt">balance</span> in high-arctic areas with anomalous gravity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sharov, A.; Rieser, D.; Nikolskiy, D.</p> <p>2012-04-01</p> <p>All known glaciological models describing the evolution of Arctic land- and sea-<span class="hlt">ice</span> <span class="hlt">masses</span> in changing climate treat the Earth's gravity as horizontally constant, but it isn't. In the High Arctic, the strength of the gravitational field varies considerably across even short distances under the influence of a density gradient, and the magnitude of free air gravity anomalies attains 100 mGal and more. On long-term base, instantaneous deviations of gravity can have a noticeable effect on the regime and <span class="hlt">mass</span> budget of glaciological objects. At best, the gravity-induced component of <span class="hlt">ice</span> <span class="hlt">mass</span> variations can be determined on topographically smooth, open and steady surfaces, like those of arctic planes, regular <span class="hlt">ice</span> caps and landfast sea <span class="hlt">ice</span>. The present research is devoted to studying gravity-driven impacts on glacier <span class="hlt">mass</span> <span class="hlt">balance</span> in the outer periphery of four Eurasian shelf seas with a very cold, dry climate and rather episodic character of winter precipitation. As main study objects we had chosen a dozen Russia's northernmost insular <span class="hlt">ice</span> caps, tens to hundreds of square kilometres in extent, situated in a close vicinity of strong gravity anomalies and surrounded with extensive fields of fast and/or drift <span class="hlt">ice</span> for most of the year. The supposition about gravitational forcing on glacioclimatic settings in the study region is based on the results of quantitative comparison and joint interpretation of existing glacier change maps and available data on the Arctic gravity field and solid precipitation. The overall mapping of medium-term (from decadal to half-centennial) changes in glacier volumes and quantification of <span class="hlt">mass</span> <span class="hlt">balance</span> characteristics in the study region was performed by comparing reference elevation models of study glaciers derived from Russian topographic maps 1:200,000 (CI = 20 or 40 m) representing the glacier state as in the 1950s-1980s with modern elevation data obtained from satellite radar interferometry and lidar altimetry. Free-air gravity anomalies were</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA617621','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA617621"><span>Wave-<span class="hlt">Ice</span> and Air-<span class="hlt">Ice</span>-Ocean Interaction During the Chukchi Sea <span class="hlt">Ice</span> Edge Advance</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2014-09-30</p> <p>During cruise CU-B UAF UW Airborne expendable <span class="hlt">Ice</span> Buoy (AXIB) Ahead, at and inside <span class="hlt">ice</span> edge Surface meteorology T, SLP ~1 year CU-B UW...<span class="hlt">Balance</span> (IMB) buoys Inside <span class="hlt">ice</span> edge w/ >50cm thickness <span class="hlt">Ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> T in snow-<span class="hlt">ice</span>-ocean, T, SLP at surface ~1 year WHOI CRREL (SeaState DRI</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26672555','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26672555"><span>Spatial and temporal distribution of <span class="hlt">mass</span> loss from the Greenland <span class="hlt">Ice</span> Sheet since AD 1900.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kjeldsen, Kristian K; Korsgaard, Niels J; Bjørk, Anders A; Khan, Shfaqat A; Box, Jason E; Funder, Svend; Larsen, Nicolaj K; Bamber, Jonathan L; Colgan, William; van den Broeke, Michiel; Siggaard-Andersen, Marie-Louise; Nuth, Christopher; Schomacker, Anders; Andresen, Camilla S; Willerslev, Eske; Kjær, Kurt H</p> <p>2015-12-17</p> <p>The response of the Greenland <span class="hlt">Ice</span> Sheet (GIS) to changes in temperature during the twentieth century remains contentious, largely owing to difficulties in estimating the spatial and temporal distribution of <span class="hlt">ice</span> <span class="hlt">mass</span> changes before 1992, when Greenland-wide observations first became available. The only previous estimates of change during the twentieth century are based on empirical modelling and energy <span class="hlt">balance</span> modelling. Consequently, no observation-based estimates of the contribution from the GIS to the global-mean sea level budget before 1990 are included in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Here we calculate spatial <span class="hlt">ice</span> <span class="hlt">mass</span> loss around the entire GIS from 1900 to the present using aerial imagery from the 1980s. This allows accurate high-resolution mapping of geomorphic features related to the maximum extent of the GIS during the Little <span class="hlt">Ice</span> Age at the end of the nineteenth century. We estimate the total <span class="hlt">ice</span> <span class="hlt">mass</span> loss and its spatial distribution for three periods: 1900-1983 (75.1 ± 29.4 gigatonnes per year), 1983-2003 (73.8 ± 40.5 gigatonnes per year), and 2003-2010 (186.4 ± 18.9 gigatonnes per year). Furthermore, using two surface <span class="hlt">mass</span> <span class="hlt">balance</span> models we partition the <span class="hlt">mass</span> <span class="hlt">balance</span> into a term for surface <span class="hlt">mass</span> <span class="hlt">balance</span> (that is, total precipitation minus total sublimation minus runoff) and a dynamic term. We find that many areas currently undergoing change are identical to those that experienced considerable thinning throughout the twentieth century. We also reveal that the surface <span class="hlt">mass</span> <span class="hlt">balance</span> term shows a considerable decrease since 2003, whereas the dynamic term is constant over the past 110 years. Overall, our observation-based findings show that during the twentieth century the GIS contributed at least 25.0 ± 9.4 millimetres of global-mean sea level rise. Our result will help to close the twentieth-century sea level budget, which remains crucial for evaluating the reliability of models used to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Natur.528..396K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Natur.528..396K"><span>Spatial and temporal distribution of <span class="hlt">mass</span> loss from the Greenland <span class="hlt">Ice</span> Sheet since AD 1900</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kjeldsen, Kristian K.; Korsgaard, Niels J.; Bjørk, Anders A.; Khan, Shfaqat A.; Box, Jason E.; Funder, Svend; Larsen, Nicolaj K.; Bamber, Jonathan L.; Colgan, William; van den Broeke, Michiel; Siggaard-Andersen, Marie-Louise; Nuth, Christopher; Schomacker, Anders; Andresen, Camilla S.; Willerslev, Eske; Kjær, Kurt H.</p> <p>2015-12-01</p> <p>The response of the Greenland <span class="hlt">Ice</span> Sheet (GIS) to changes in temperature during the twentieth century remains contentious, largely owing to difficulties in estimating the spatial and temporal distribution of <span class="hlt">ice</span> <span class="hlt">mass</span> changes before 1992, when Greenland-wide observations first became available. The only previous estimates of change during the twentieth century are based on empirical modelling and energy <span class="hlt">balance</span> modelling. Consequently, no observation-based estimates of the contribution from the GIS to the global-mean sea level budget before 1990 are included in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Here we calculate spatial <span class="hlt">ice</span> <span class="hlt">mass</span> loss around the entire GIS from 1900 to the present using aerial imagery from the 1980s. This allows accurate high-resolution mapping of geomorphic features related to the maximum extent of the GIS during the Little <span class="hlt">Ice</span> Age at the end of the nineteenth century. We estimate the total <span class="hlt">ice</span> <span class="hlt">mass</span> loss and its spatial distribution for three periods: 1900-1983 (75.1 ± 29.4 gigatonnes per year), 1983-2003 (73.8 ± 40.5 gigatonnes per year), and 2003-2010 (186.4 ± 18.9 gigatonnes per year). Furthermore, using two surface <span class="hlt">mass</span> <span class="hlt">balance</span> models we partition the <span class="hlt">mass</span> <span class="hlt">balance</span> into a term for surface <span class="hlt">mass</span> <span class="hlt">balance</span> (that is, total precipitation minus total sublimation minus runoff) and a dynamic term. We find that many areas currently undergoing change are identical to those that experienced considerable thinning throughout the twentieth century. We also reveal that the surface <span class="hlt">mass</span> <span class="hlt">balance</span> term shows a considerable decrease since 2003, whereas the dynamic term is constant over the past 110 years. Overall, our observation-based findings show that during the twentieth century the GIS contributed at least 25.0 ± 9.4 millimetres of global-mean sea level rise. Our result will help to close the twentieth-century sea level budget, which remains crucial for evaluating the reliability of models used to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C23B0660H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C23B0660H"><span><span class="hlt">Mass</span> and surface energy <span class="hlt">balance</span> of A.P. Olsen <span class="hlt">ice</span> cap, NE Greenland, from observations and modeling (1995-2011)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hillerup Larsen, S.; Citterio, M.; Hock, R. M.; Ahlstrom, A. P.</p> <p>2012-12-01</p> <p>The A.P. Olsen <span class="hlt">Ice</span> Cap (74.6 N, 21.5 W) in NE Greenland covers an area of 295 km2, is composed by two domes, of which the western is the largest, and spans an elevation range between 200 and 1450 m a.s.l. In this study we calculate the 2008-2011 annual glacier <span class="hlt">mass</span> <span class="hlt">balance</span> based on in situ observations, we model the surface energy <span class="hlt">balance</span> over the same period, and we reconstruct annual glacier <span class="hlt">mass</span> <span class="hlt">balance</span> since 1995. We use GlacioBasis Monitoring Programme observations from a network of 15 ablation stakes and three automatic weather stations (AWS) at 600 m (ca. 100 m higher than the terminus) and at 840 m on the main glacier outlet of the western dome, and at 1430 m in the accumulation area. Accumulation is measured every year in springtime by snow radar surveys calibrated with manual probing and density profiles from snow pits. GlacioBasis data start in 2008, but a longer time series starting in 1995 is available from a weather station at 44 m a.s.l. close to Zackenberg Research Station, ca. 30 km further west. Shorter data series from three more AWS on land at 145 m, 410 m and 1283 m a.s.l. are used to estimate monthly average temperature lapse rates outside of the glacier boundary layer, and to detect the occurrence of temperature inversions. The surface energy <span class="hlt">mass</span> <span class="hlt">balance</span> is dominated by the radiative fluxes. We discuss the effect of shadows from the valley sides over parts of the tongue, especially early and late in the melt season when the sun is lower over the horizon, and analyze the modeled <span class="hlt">mass</span> <span class="hlt">balance</span> sensitivity to a 1 °C temperature increase. A temperature index model driven by the 1995-2008 time series and calibrated using post-2008 glacier <span class="hlt">mass</span> <span class="hlt">balance</span> measurements shows large interannual variability, with 5 of the most negative <span class="hlt">mass</span> <span class="hlt">balance</span> years of the entire 1995-2011period occurring between 2003 and 2008. In particular during 2008 the glacier experienced almost no net accumulation over the entire elevation range. This matches 2008 <span class="hlt">mass</span> <span class="hlt">balance</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814608M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814608M"><span>Present and Future Surface <span class="hlt">Mass</span> Budget of Small Arctic <span class="hlt">Ice</span> Caps in a High Resolution Regional Climate Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mottram, Ruth; Langen, Peter; Koldtoft, Iben; Midefelt, Linnea; Hesselbjerg Christensen, Jens</p> <p>2016-04-01</p> <p>Globally, small <span class="hlt">ice</span> caps and glaciers make a substantial contribution to sea level rise; this is also true in the Arctic. Around Greenland small <span class="hlt">ice</span> caps are surprisingly important to the total <span class="hlt">mass</span> <span class="hlt">balance</span> from the island as their marginal coastal position means they receive a large amount of precipitation and also experience high surface melt rates. Since small <span class="hlt">ice</span> caps and glaciers have had a disproportionate number of long-term monitoring and observational schemes in the Arctic, likely due to their relative accessibility, they can also be a valuable source of data. However, in climate models the surface <span class="hlt">mass</span> <span class="hlt">balance</span> contributions are often not distinguished from the main <span class="hlt">ice</span> sheet and the presence of high relief topography is difficult to capture in coarse resolution climate models. At the same time, the diminutive size of marginal <span class="hlt">ice</span> <span class="hlt">masses</span> in comparison to the <span class="hlt">ice</span> sheet makes modelling their <span class="hlt">ice</span> dynamics difficult. Using observational data from the Devon <span class="hlt">Ice</span> Cap in Arctic Canada and the Renland <span class="hlt">Ice</span> Cap in Eastern Greenland, we assess the success of a very high resolution (~5km) regional climate model, HIRHAM5 in capturing the surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) of these small <span class="hlt">ice</span> caps. The model is forced with ERA-Interim and we compare observed mean SMB and the interannual variability to assess model performance. The steep gradient in topography around Renland is challenging for climate models and additional statistical corrections are required to fit the calculated surface <span class="hlt">mass</span> <span class="hlt">balance</span> to the high relief topography. Results from a modelling experiment at Renland <span class="hlt">Ice</span> Cap shows that this technique produces a better fit between modelled and observed surface topography. We apply this statistical relationship to modelled SMB on the Devon <span class="hlt">Ice</span> Cap and use the long time series of observations from this glacier to evaluate the model and the smoothed SMB. Measured SMB values from a number of other small <span class="hlt">ice</span> caps including Mittivakkat and A.P. Olsen <span class="hlt">ice</span> cap are also compared</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120014297','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120014297"><span>An Iterated Global Mascon Solution with Focus on Land <span class="hlt">Ice</span> <span class="hlt">Mass</span> Evolution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Luthcke, S. B.; Sabaka, T.; Rowlands, D. D.; Lemoine, F. G.; Loomis, B. D.; Boy, J. P.</p> <p>2012-01-01</p> <p>Land <span class="hlt">ice</span> <span class="hlt">mass</span> evolution is determined from a new GRACE global mascon solution. The solution is estimated directly from the reduction of the inter-satellite K-band range rate observations taking into account the full noise covariance, and formally iterating the solution. The new solution increases signal recovery while reducing the GRACE KBRR observation residuals. The mascons are estimated with 10-day and 1-arc-degree equal area sampling, applying anisotropic constraints for enhanced temporal and spatial resolution of the recovered land <span class="hlt">ice</span> signal. The details of the solution are presented including error and resolution analysis. An Ensemble Empirical Mode Decomposition (EEMD) adaptive filter is applied to the mascon solution time series to compute timing of <span class="hlt">balance</span> seasons and annual <span class="hlt">mass</span> <span class="hlt">balances</span>. The details and causes of the spatial and temporal variability of the land <span class="hlt">ice</span> regions studied are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70028080','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70028080"><span>Satellite-derived, melt-season surface temperature of the Greenland <span class="hlt">Ice</span> Sheet (2000-2005) and its relationship to <span class="hlt">mass</span> <span class="hlt">balance</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hall, D.K.; Williams, R.S.; Casey, K.A.; DiGirolamo, N.E.; Wan, Z.</p> <p>2006-01-01</p> <p>Mean, clear-sky surface temperature of the Greenland <span class="hlt">Ice</span> Sheet was measured for each melt season from 2000 to 2005 using Moderate-Resolution Imaging Spectroradiometer (MODIS)–derived land-surface temperature (LST) data-product maps. During the period of most-active melt, the mean, clear-sky surface temperature of the <span class="hlt">ice</span> sheet was highest in 2002 (−8.29 ± 5.29°C) and 2005 (−8.29 ± 5.43°C), compared to a 6-year mean of −9.04 ± 5.59°C, in agreement with recent work by other investigators showing unusually extensive melt in 2002 and 2005. Surface-temperature variability shows a correspondence with the dry-snow facies of the <span class="hlt">ice</span> sheet; a reduction in area of the dry-snow facies would indicate a more-negative <span class="hlt">mass</span> <span class="hlt">balance</span>. Surface-temperature variability generally increased during the study period and is most pronounced in the 2005 melt season; this is consistent with surface instability caused by air-temperature fluctuations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12.1479M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12.1479M"><span>Modelling the climate and surface <span class="hlt">mass</span> <span class="hlt">balance</span> of polar <span class="hlt">ice</span> sheets using RACMO2 - Part 2: Antarctica (1979-2016)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Melchior van Wessem, Jan; van de Berg, Willem Jan; Noël, Brice P. Y.; van Meijgaard, Erik; Amory, Charles; Birnbaum, Gerit; Jakobs, Constantijn L.; Krüger, Konstantin; Lenaerts, Jan T. M.; Lhermitte, Stef; Ligtenberg, Stefan R. M.; Medley, Brooke; Reijmer, Carleen H.; van Tricht, Kristof; Trusel, Luke D.; van Ulft, Lambertus H.; Wouters, Bert; Wuite, Jan; van den Broeke, Michiel R.</p> <p>2018-04-01</p> <p>We evaluate modelled Antarctic <span class="hlt">ice</span> sheet (AIS) near-surface climate, surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) and surface energy <span class="hlt">balance</span> (SEB) from the updated polar version of the regional atmospheric climate model, RACMO2 (1979-2016). The updated model, referred to as RACMO2.3p2, incorporates upper-air relaxation, a revised topography, tuned parameters in the cloud scheme to generate more precipitation towards the AIS interior and modified snow properties reducing drifting snow sublimation and increasing surface snowmelt. Comparisons of RACMO2 model output with several independent observational data show that the existing biases in AIS temperature, radiative fluxes and SMB components are further reduced with respect to the previous model version. The model-integrated annual average SMB for the <span class="hlt">ice</span> sheet including <span class="hlt">ice</span> shelves (minus the Antarctic Peninsula, AP) now amounts to 2229 Gt y-1, with an interannual variability of 109 Gt y-1. The largest improvement is found in modelled surface snowmelt, which now compares well with satellite and weather station observations. For the high-resolution ( ˜ 5.5 km) AP simulation, results remain comparable to earlier studies. The updated model provides a new, high-resolution data set of the contemporary near-surface climate and SMB of the AIS; this model version will be used for future climate scenario projections in a forthcoming study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C21B0585S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C21B0585S"><span><span class="hlt">Mass</span> <span class="hlt">Balance</span> of the Northern Antarctic Peninsula and its Ongoing Response to <span class="hlt">Ice</span> Shelf Loss</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scambos, T. A.; Berthier, E.; Haran, T. M.; Shuman, C. A.; Cook, A. J.; Bohlander, J. A.</p> <p>2012-12-01</p> <p>An assessment of the most rapidly changing areas of the Antarctic Peninsula (north of 66°S) shows that <span class="hlt">ice</span> <span class="hlt">mass</span> loss for the region is dominated by areas affected by eastern-Peninsula <span class="hlt">ice</span> shelf losses in the past 20 years. Little if any of the <span class="hlt">mass</span> loss is compensated by increased snowfall in the northwestern or far northern areas. We combined satellite stereo-image DEM differencing and ICESat-derived along-track elevation changes to measure <span class="hlt">ice</span> <span class="hlt">mass</span> loss for the Antarctic Peninsula north of 66°S between 2001-2010, focusing on the ICESat-1 period of operation (2003-2009). This mapping includes all <span class="hlt">ice</span> drainages affected by recent <span class="hlt">ice</span> shelf loss in the northeastern Peninsula (Prince Gustav, Larsen Inlet, Larsen A, and Larsen B) as well as James Ross Island, Vega Island, Anvers Island, Brabant Island and the adjacent west-flowing glaciers. Polaris Glacier (feeding the Larsen Inlet, which collapsed in 1986) is an exception, and may have stabilized. Our method uses ASTER and SPOT-5 stereo-image DEMs to determine dh/dt for elevations below 800 m; at higher elevations ICESat along-track elevation differencing is used. To adjust along-track path offsets between its 2003-2009 campaigns, we use a recent DEM of the Peninsula to establish and correct for cross-track slope (Cook et al., 2012, doi:10.5194/essdd-5-365-2012; http://nsidc.org/data/nsidc-0516.html) . We reduce the effect of possible seasonal variations in elevation by using only integer-year repeats of the ICESat tracks for comparison. <span class="hlt">Mass</span> losses are dominated by the major glaciers that had flowed into the Prince Gustav (Boydell, Sjorgren, Röhss), Larsen A (Edgeworth, Bombardier, Dinsmoor, Drygalski), and Larsen B (Hektoria, Jorum, and Crane) embayments. The pattern of <span class="hlt">mass</span> loss emphasizes the significant and multi-decadal response to <span class="hlt">ice</span> shelf loss. Areas with shelf losses occurring 30 to 100s of years ago seem to be relatively stable or losing <span class="hlt">mass</span> only slowly (western glaciers, northernmost areas). The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PolSc..10..111N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PolSc..10..111N"><span>Net <span class="hlt">mass</span> <span class="hlt">balance</span> calculations for the Shirase Drainage Basin, east Antarctica, using the <span class="hlt">mass</span> budget method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakamura, Kazuki; Yamanokuchi, Tsutomu; Doi, Koichiro; Shibuya, Kazuo</p> <p>2016-06-01</p> <p>We quantify the <span class="hlt">mass</span> budget of the Shirase drainage basin (SHI), Antarctica, by separately estimating snow accumulation (surface <span class="hlt">mass</span> <span class="hlt">balance</span>; SMB) and glacier <span class="hlt">ice</span> <span class="hlt">mass</span> discharge (IMD). We estimated the SMB in the SHI, using a regional atmospheric climate model (RACMO2.1). The SMB of the mainstream A flow region was 12.1 ± 1.5 Gt a-1 for an area of 1.985 × 105 km2. Obvious overestimation of the model round the coast, ∼0.5 Gt a-1, was corrected for. For calculating the IMD, we employed a 15-m resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) with a digital elevation model (DEM) to determine the heights at the grounding line (GL), after comparison with the interpolated Bamber DEM grid heights; the results of this are referred to as the measured heights. <span class="hlt">Ice</span> thickness data at the GL were inferred by using a free-board relationship between the measured height and the <span class="hlt">ice</span> thickness, and considering the measured firn depth correction (4.2 m with the reference <span class="hlt">ice</span> density of 910 kg m-3) for the nearby blue-<span class="hlt">ice</span> area. The total IMD was estimated to be 14.0 ± 1.8 Gt a-1. Semi-empirical firn densification model gives the estimate within 0.1-0.2 Gt a-1 difference. The estimated net <span class="hlt">mass</span> <span class="hlt">balance</span>, -1.9 Gt a-1, has a two-σ uncertainty of ±3.3 Gt a-1, and probable melt water discharge strongly suggests negative NMB, although the associated uncertainty is large.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C13C0833S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C13C0833S"><span>Using ATM laser altimetry to constrain surface <span class="hlt">mass</span> <span class="hlt">balance</span> estimates and supraglacial hydrology of the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Studinger, M.; Medley, B.; Manizade, S.; Linkswiler, M. A.</p> <p>2016-12-01</p> <p>Repeat airborne laser altimetry measurements can provide large-scale field observations to better quantify spatial and temporal variability of surface processes contributing to seasonal elevation change and therefore surface <span class="hlt">mass</span> <span class="hlt">balance</span>. As part of NASA's Operation <span class="hlt">Ice</span>Bridge the Airborne Topographic Mapper (ATM) laser altimeter measured the surface elevation of the Greenland <span class="hlt">Ice</span> Sheet during spring (March - May) and fall (September - October) of 2015. Comparison of the two surveys reveals a general trend of thinning for outlet glaciers and for the <span class="hlt">ice</span> sheet in a manner related to elevation and latitude. In contrast, some thickening is observed on the west (but not on the east) side of the <span class="hlt">ice</span> divide above 2200 m elevation in the southern half, below latitude 69°N.The observed magnitude and spatial patterns of the summer melt signal can be utilized as input into <span class="hlt">ice</span> sheet models and for validating reanalysis of regional climate models such as RACMO and MAR. We use seasonal anomalies in MERRA-2 climate fields (temperature, precipitation) to understand the observed spatial signal in seasonal change. Aside from surface elevation change, runoff from meltwater pooling in supraglacial lakes and meltwater channels accounts for at least half of the total <span class="hlt">mass</span> loss. The ability of the ATM laser altimeters to image glacial hydrological features in 3-D and determine the depth of supraglacial lakes could be used for process studies and for quantifying melt processes over large scales. The 1-meter footprint diameter of ATM laser on the surface, together with a high shot density, allows for the production of large-scale, high-resolution, geodetic quality DEMs (50 x 50 cm) suitable for fine-scale glacial hydrology research and as input to hydrological models quantifying runoff.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C53C0787S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C53C0787S"><span>Development of a multi-sensor elevation time series pole-ward of 86°S in support of altimetry validation and <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Studinger, M.; Brunt, K. M.; Casey, K.; Medley, B.; Neumann, T.; Manizade, S.; Linkswiler, M. A.</p> <p>2015-12-01</p> <p>In order to produce a cross-calibrated long-term record of <span class="hlt">ice</span>-surface elevation change for input into <span class="hlt">ice</span> sheet models and <span class="hlt">mass</span> <span class="hlt">balance</span> studies it is necessary to "link the measurements made by airborne laser altimeters, satellite measurements of ICESat, ICESat-2, and CryoSat-2" [<span class="hlt">Ice</span>Bridge Level 1 Science Requirements, 2012] and determine the biases and the spatial variations between radar altimeters and laser altimeters using different wavelengths. The convergence zones of all ICESat tracks (86°S) and all ICESat-2 and CryoSat-2 tracks (88°S) are in regions of relatively low accumulation, making them ideal for satellite altimetry calibration. In preparation for ICESat-2 validation, the <span class="hlt">Ice</span>Bridge and ICESat-2 science teams have designed <span class="hlt">Ice</span>Bridge data acquisitions around 86°S and 88°S. Several aspects need to be considered when comparing and combining elevation measurements from different radar and laser altimeters, including: a) foot print size and spatial sampling pattern; b) accuracy and precision of each data sets; c) varying signal penetration into the snow; and d) changes in geodetic reference frames over time, such as the International Terrestrial Reference Frame (ITRF). The presentation will focus on the analysis of several <span class="hlt">Ice</span>Bridge flights around 86 and 88°S with the LVIS and ATM airborne laser altimeters and will evaluate the accuracy and precision of these data sets. To properly interpret the observed elevation change (dh/dt) as <span class="hlt">mass</span> change, however, the various processes that control surface elevation fluctuations must be quantified and therefore future work will quantify the spatial variability in snow accumulation rates pole-ward of 86°S and in particular around 88°S. Our goal is to develop a cross-validated multi-sensor time series of surface elevation change pole-ward of 86°S that, in combination with measured accumulation rates, will support ICESat-2 calibration and validation and <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.7964C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.7964C"><span>Reassessment of the <span class="hlt">mass</span> <span class="hlt">balance</span> of the Abbot and Getz sectors of West Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chuter, Stephen; Martín-Español, Alba; Wouters, Bert; Bamber, Jonathan</p> <p>2017-04-01</p> <p>Large discrepancies exist in <span class="hlt">mass</span> <span class="hlt">balance</span> estimates for the Getz and Abbot drainage basins, primarily due to previous poor knowledge of <span class="hlt">ice</span> thickness at the grounding line, poor coverage by previous altimetry missions and signal leakage issues for GRACE. This is particularly the case for the Abbot region, where previously there have been contrasting positive <span class="hlt">ice</span> sheet basin elevation rates from altimetry and negative <span class="hlt">mass</span> budget estimates. Large errors arise when using <span class="hlt">ice</span> thickness measurements derived from ERS-1 and/or ICESat altimetry data due to poor track spacing, 'loss of lock' issues near the grounding line and the complex morphology of these shelves, requiring fine resolution to derive robust and accurate elevations close to the grounding line. This was exemplified with the manual adjustments of up to 100 m required at the grounding line during the creation of Bedmap2. However, the advent of CryoSat-2 with its unique orbit and SARIn mode of operation has overcome these issues and enabled the determination of <span class="hlt">ice</span> shelf thickness at a much higher accuracy than possible from previous satellites, particularly within the grounding zone. We present a reassessment of <span class="hlt">mass</span> <span class="hlt">balance</span> estimates for the 2007-2009 epoch using improved CryoSat-2 <span class="hlt">ice</span> thicknesses. We find that CryoSat-2 <span class="hlt">ice</span> thickness estimates are systematically thinner by 30% and 16.5% for the Abbot and Getz sectors respectively. Our new <span class="hlt">mass</span> <span class="hlt">balance</span> estimate of 8 ± 6 Gt yr-1for the Abbot region resolves the previous discrepancy with altimetry. Over the Getz region, the new <span class="hlt">mass</span> <span class="hlt">balance</span> estimate of 7.56 ± 16.6 Gt yr-1is in better agreement with other geodetic techniques. We also find there has been an increase in grounding line velocity of up to 20% since the 2007-2009 epoch, coupled with mean <span class="hlt">ice</span> sheet thinning rates of -0.67 ± 0.13 m yr-1 derived from CryoSat-2 in fast flow regions. This is in addition to mean snowfall trends of -0.33 m yr-1w.e. since 2006. This suggests the onset of a dynamic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C41E0713C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C41E0713C"><span>Evaluation of a 12-km Satellite-Era Reanalysis of Surface <span class="hlt">Mass</span> <span class="hlt">Balance</span> for the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cullather, R. I.; Nowicki, S.; Zhao, B.; Max, S.</p> <p>2016-12-01</p> <p>The recent contribution to sea level change from the Greenland <span class="hlt">Ice</span> Sheet is thought to be strongly driven by surface processes including melt and runoff. Global reanalyses are potential means of reconstructing the historical time series of <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB), but lack spatial resolution needed to resolve ablation areas along the periphery of the <span class="hlt">ice</span> sheet. In this work, the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) is used to examine the spatial and temporal variability of surface melt over the Greenland <span class="hlt">Ice</span> Sheet. MERRA-2 is produced for the period 1980 to the present at a grid spacing of ½° latitude by ⅝° longitude, and includes snow hydrology processes including compaction, meltwater percolation and refreezing, runoff, and a prognostic surface albedo. The configuration of the MERRA-2 system allows for the background model - the Goddard Earth Observing System model, version 5 (GEOS-5) - to be carried in phase space through analyzed states via the computation of analysis increments, a capability referred to as "replay". Here, a MERRA-2 replay integration is conducted in which atmospheric forcing fields are interpolated and adjusted to sub- atmospheric grid-scale resolution. These adjustments include lapse-rate effects on temperature, humidity, precipitation, and other atmospheric variables that are known to have a strong elevation dependency over <span class="hlt">ice</span> sheets. The surface coupling is performed such that <span class="hlt">mass</span> and energy are conserved. The atmospheric forcing influences the surface representation, which operates on land surface tiles with an approximate 12-km spacing. This produces a high-resolution, downscaled SMB which is interactively coupled to the reanalysis model. We compare the downscaled SMB product with other reanalyses, regional climate model values, and a second MERRA-2 replay in which the background model has been replaced with a 12-km, non-hydrostatic version of GEOS-5. The assessment</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990071136&hterms=balance+sheet&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dbalance%2Bsheet','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990071136&hterms=balance+sheet&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dbalance%2Bsheet"><span>Large <span class="hlt">Ice</span> Discharge From the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rignot, Eric</p> <p>1999-01-01</p> <p>The objectives of this work are to measure the <span class="hlt">ice</span> discharge of the Greenland <span class="hlt">Ice</span> Sheet close to the grounding line and/or calving front, and compare the results with <span class="hlt">mass</span> accumulation and ablation in the interior to estimate the <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C11A0738C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C11A0738C"><span>Re-assessment of the <span class="hlt">mass</span> <span class="hlt">balance</span> of the Abbot and Getz sectors of West Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chuter, S.; Bamber, J. L.</p> <p>2016-12-01</p> <p>Large discrepancies exist in <span class="hlt">mass</span> <span class="hlt">balance</span> estimates for the Getz and Abbot drainage basins, primarily due to previous poor knowledge of <span class="hlt">ice</span> thickness at the grounding line, poor coverage by previous altimetry missions and signal leakage issues for GRACE. Large errors arise when using <span class="hlt">ice</span> thickness measurements derived from ERS-1 and/or ICESat altimetry data due to poor track spacing, `loss of lock' issues near the grounding line and the complex morphology of these shelves, requiring fine resolution to derive robust and accurate elevations close to the grounding line. However, the advent of CryoSat-2 with its unique orbit and SARIn mode of operation has overcome these issues and enabled the determination of <span class="hlt">ice</span> shelf thickness at a much higher accuracy than possible from previous satellites, particularly within the grounding zone. Here we present a contemporary estimate of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> for the both the Getz and Abbot drainage basins. This is achieved through the use of contemporary velocity data derived from Landsat feature tracking and the use of CryoSat-2 derived <span class="hlt">ice</span> thickness measurements. Additionally, we use this new <span class="hlt">ice</span> thickness dataset to reassess <span class="hlt">mass</span> <span class="hlt">balance</span> estimates from 2008/2009, where there were large disparities between results from radar altimetry and Input-Output methodologies over the Abbot region in particular. These contemporary results are compared with other present day estimates from gravimetry and altimetry elevation changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009089','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009089"><span>Overview and Assessment of Antarctic <span class="hlt">Ice</span>-Sheet <span class="hlt">Mass</span> <span class="hlt">Balance</span> Estimates: 1992-2009</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Giovinetto, Mario B.</p> <p>2011-01-01</p> <p><span class="hlt">Mass</span> <span class="hlt">balance</span> estimates for the Antarctic <span class="hlt">Ice</span> Sheet (AIS) in the 2007 report by the Intergovernmental Panel on Climate Change and in more recent reports lie between approximately ?50 to -250 Gt/year for 1992 to 2009. The 300 Gt/year range is approximately 15% of the annual <span class="hlt">mass</span> input and 0.8 mm/year Sea Level Equivalent (SLE). Two estimates from radar altimeter measurements of elevation change by European Remote-sensing Satellites (ERS) (?28 and -31 Gt/year) lie in the upper part, whereas estimates from the Input-minus-Output Method (IOM) and the Gravity Recovery and Climate Experiment (GRACE) lie in the lower part (-40 to -246 Gt/year). We compare the various estimates, discuss the methodology used, and critically assess the results. We also modify the IOM estimate using (1) an alternate extrapolation to estimate the discharge from the non-observed 15% of the periphery, and (2) substitution of input from a field data compilation for input from an atmospheric model in 6% of area. The modified IOM estimate reduces the loss from 136 Gt/year to 13 Gt/year. Two ERS-based estimates, the modified IOM, and a GRACE-based estimate for observations within 1992 2005 lie in a narrowed range of ?27 to -40 Gt/year, which is about 3% of the annual <span class="hlt">mass</span> input and only 0.2 mm/year SLE. Our preferred estimate for 1992 2001 is -47 Gt/year for West Antarctica, ?16 Gt/year for East Antarctica, and -31 Gt/year overall (?0.1 mm/year SLE), not including part of the Antarctic Peninsula (1.07% of the AIS area). Although recent reports of large and increasing rates of <span class="hlt">mass</span> loss with time from GRACE-based studies cite agreement with IOM results, our evaluation does not support that conclusion</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910064170&hterms=balance+sheet&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dbalance%2Bsheet','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910064170&hterms=balance+sheet&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dbalance%2Bsheet"><span>State of <span class="hlt">balance</span> of the cryosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Van Der Veen, C. J.</p> <p>1991-01-01</p> <p>Available observations and <span class="hlt">mass</span> <span class="hlt">balance</span> estimates of the cryosphere are summarized. Problems discussed include mountain glaciers, the Greenland <span class="hlt">ice</span> sheet, the Antarctic <span class="hlt">ice</span> sheet, conventional glacier measurement techniques, and satellite applications in glacier <span class="hlt">mass</span> <span class="hlt">balance</span> studies. It is concluded that the interior part of the Greenland <span class="hlt">ice</span> sheet is thickening or in near equilibrium. Estimates of the <span class="hlt">mass</span> <span class="hlt">balance</span> of the Antarctic <span class="hlt">ice</span> sheet suggest that it is positive, although the error limits allow for a slightly negative <span class="hlt">balance</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C11A0533C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C11A0533C"><span>From Outlet Glacier Changes to <span class="hlt">Ice</span> Sheet <span class="hlt">Mass</span> <span class="hlt">Balance</span> - Evolution of Greenland <span class="hlt">Ice</span> Sheet from Laser Altimetry Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Csatho, B. M.; Schenk, A.; Nagarajan, S.; Babonis, G. S.</p> <p>2010-12-01</p> <p>Investigations of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> and the changing dynamics of outlet glaciers have been hampered by the lack of comprehensive data. In recent years, this situation has been remedied. Satellite laser altimetry data from the <span class="hlt">Ice</span> Cloud and land Elevation Satellite mission (ICESat), combined with airborne laser altimetry, provide accurate measurements of surface elevation changes, and surface velocities derived from various satellite platforms yield crucial information on changing glacier dynamics. Taken together, a rich and diverse data set is emerging that allows for characterizing the spatial and temporal evolution of <span class="hlt">ice</span> sheets and outlet glaciers. In particular, it enables quantitative studies of outlet glaciers undergoing rapid and complex changes. Although airborne and laser altimetry have been providing precise measurements of <span class="hlt">ice</span> sheet topography since the early 1990s, determining detailed and accurate spatial and temporal distribution of surface changes remains a challenging problem. We have developed a new, comprehensive method, called Surface Elevation Reconstruction And Change detection (SERAC), which estimates surface changes by a simultaneous reconstruction of surface topography from fused multisensor data. The mathematical model is based on the assumption that for a small surface area, only the absolute elevation changes over time but not the shape of the surface patch. Therefore, laser points of all time epochs contribute to the shape parameters; points of each time period determine the absolute elevation of the surface patch at that period. This method provides high-resolution surface topography, precise changes and a rigorous error estimate of the quantities. By using SERAC we combined ICESat and ATM laser altimetry data to determine the evolution of surface change rates of the whole Greenland <span class="hlt">Ice</span> Sheet between 2003 and 2009 on a high-resolution grid. Our reconstruction, consistent with GRACE results, shows <span class="hlt">ice</span> sheet thinning propagating</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.G31C0929H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.G31C0929H"><span>Long term <span class="hlt">ice</span> sheet <span class="hlt">mass</span> change rates and inter-annual variability from GRACE gravimetry.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harig, C.</p> <p>2017-12-01</p> <p>The GRACE time series of gravimetry now stretches 15 years since its launch in 2002. Here we use Slepian functions to estimate the long term <span class="hlt">ice</span> <span class="hlt">mass</span> trends of Greenland, Antarctica, and several glaciated regions. The spatial representation shows multi-year to decadal regional shifts in accelerations, in agreement with increases in radar derived <span class="hlt">ice</span> velocity. Interannual variations in <span class="hlt">ice</span> <span class="hlt">mass</span> are of particular interest since they can directly link changes in <span class="hlt">ice</span> sheets to the drivers of change in the polar ocean and atmosphere. The spatial information retained in Slepian functions provides a tool to determine how this link varies in different regions within an <span class="hlt">ice</span> sheet. We present GRACE observations of the 2013-2014 slowdown in <span class="hlt">mass</span> loss of the Greenland <span class="hlt">ice</span> sheet, which was concentrated in specific parts of the <span class="hlt">ice</span> sheet and in certain months of the year. We also discuss estimating the relative importance of climate factors that control <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>, as a function of location of the glacier/<span class="hlt">ice</span> cap as well as the spatial variation within an <span class="hlt">ice</span> sheet by comparing gravimetry with observations of surface air temperature, ocean temperature, etc. as well as model data from climate reanalysis products.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.C41A..02R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.C41A..02R"><span>Leakage of the Greenland <span class="hlt">Ice</span> Sheet through accelerated <span class="hlt">ice</span> flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rignot, E.</p> <p>2005-12-01</p> <p>A map of coastal velocities of the Greenland <span class="hlt">ice</span> sheet was produced from Radarsat-1 acquired during the background mission of 2000 and combined with radio echo sounding data to estimate the <span class="hlt">ice</span> discharge from the <span class="hlt">ice</span> sheet. On individual glaciers, <span class="hlt">ice</span> discharge was compared with snow input from the interior and melt above the flux gate to determine the glacier <span class="hlt">mass</span> <span class="hlt">balance</span>. Time series of velocities on several glaciers at different latitudes reveal seasonal fluctuations of only 7-8 percent so that winter velocities are only 2 percent less than the yearly mean. The results show the northern Greenland glaciers to be close to <span class="hlt">balance</span> yet losing <span class="hlt">mass</span>. No change in <span class="hlt">ice</span> flow is detected on Petermann, 79north and Zachariae Isstrom in 2000-2004. East Greenland glaciers are in <span class="hlt">balance</span> and flowing steadily north of Kangerdlussuaq, but Kangerdlussuaq, Helheim and all the southeastern glaciers are thinning dramatically. All these glaciers accelerated, Kangerdlussuaq in 2000, Helheim prior to 2004, and southeast Greenland glaciers accelerated 10 to 50 percent in 2000-2004. Glacier acceleration is generally brutal, probably once the glacier reached a threshold, and sustained. In the northwest, most glaciers are largely out of <span class="hlt">balance</span>. Jakobshavn accelerated significantly in 2002, and glaciers in its immediate vicinity accelerated more than 50 percent in 2000-2004. Less is known about southwest Greenland glaciers due to a lack of <span class="hlt">ice</span> thickness data but the glaciers have accelerated there as well and are likely to be strongly out of <span class="hlt">balance</span> despite thickening of the interior. Overall, I estimate the <span class="hlt">mass</span> <span class="hlt">balance</span> of the Greenland <span class="hlt">ice</span> sheet to be about -80 +/-10 cubic km of <span class="hlt">ice</span> per year in 2000 and -110 +/-15 cubic km of <span class="hlt">ice</span> per year in 2004, i.e. more negative than based on partial altimetry surveys of the outlet glaciers. As climate continues to warm, more glaciers will accelerate, and the <span class="hlt">mass</span> <span class="hlt">balance</span> will become increasingly negative, regardless of the evolution of the <span class="hlt">ice</span> sheet</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C42A..06E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C42A..06E"><span>Quantifying Uncertainty in the Greenland Surface <span class="hlt">Mass</span> <span class="hlt">Balance</span> Elevation Feedback</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Edwards, T.</p> <p>2015-12-01</p> <p>As the shape of the Greenland <span class="hlt">ice</span> sheet responds to changes in surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) and dynamics, it affects the surface <span class="hlt">mass</span> <span class="hlt">balance</span> through the atmospheric lapse rate and by altering atmospheric circulation patterns. Positive degree day models include simplified representations of this feedback, but it is difficult to simulate with state-of-the-art models because it requires coupling of regional climate models with dynamical <span class="hlt">ice</span> sheet models, which is technically challenging. This difficulty, along with the high computational expense of regional climate models, also drastically limits opportunities for exploring the impact of modelling uncertainties on sea level projections. We present a parameterisation of the SMB-elevation feedback in the MAR regional climate model that provides a far easier and quicker estimate than atmosphere-<span class="hlt">ice</span> sheet model coupling, which can be used with any <span class="hlt">ice</span> sheet model. This allows us to use ensembles of different parameter values and <span class="hlt">ice</span> sheet models to assess the effect of uncertainty in the feedback and <span class="hlt">ice</span> sheet model structure on future sea level projections. We take a Bayesian approach to uncertainty in the feedback parameterisation, scoring the results from multiple possible "SMB lapse rates" according to how well they reproduce a MAR simulation with altered <span class="hlt">ice</span> sheet topography. We test the impact of the resulting parameterisation on sea level projections using five <span class="hlt">ice</span> sheet models forced by MAR (in turned forced by two different global climate models) under the emissions scenario A1B. The estimated additional sea level contribution due to the SMB-elevation feedback is 4.3% at 2100 (95% credibility interval 1.8-6.9%), and 9.6% at 2200 (3.6-16.0%).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C41E0727D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C41E0727D"><span>Continuous measurements of surface <span class="hlt">mass</span> <span class="hlt">balance</span>, firn compaction, and meltwater retention in Greenland for altimetry validation.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de la Peña, S.; Howat, I.; Behar, A.; Price, S. F.; Thanga, J.; Crowell, J. M.; Huseas, S.; Tedesco, M.</p> <p>2016-12-01</p> <p>Observations made in recent years by repeated altimetry from CryoSat-2 and NASA's Operation <span class="hlt">Ice</span>Bridge reveal large fluctuations in the firn volume of the Greenland <span class="hlt">Ice</span> Sheet. Although an order of magnitude smaller than <span class="hlt">ice</span> thinning rates observed in some areas at the margins of the <span class="hlt">ice</span> sheet, short-term departures in surface elevation trends occur over most of the accumulation zone of Greenland. Changes in the thickness of the firn column are influenced by variability in surface <span class="hlt">mass</span> <span class="hlt">balance</span>, firn compaction, and abrupt seasonal densification near the surface caused by refreezing at depth of variable amounts of surface meltwater in the summer. These processes and dynamic thinning cannot be differentiated from each other by altimetry alone. Until recently, nearly all information on density and surface <span class="hlt">mass</span> <span class="hlt">balance</span> changes over the firn layer came from <span class="hlt">ice</span> core and snow pit stratigraphy that provided annual rates with relatively large uncertainties. Here we present direct, continuous measurements of firn density and surface <span class="hlt">mass</span> <span class="hlt">balance</span> along with annual estimates of firn <span class="hlt">ice</span> content used to assess observed elevation change in the percolation zone of western Greenland in relation to firn processes. Since 2012, autonomous in-situ firn compaction sensors have monitored several sites in the catchment area of Jakobshavn Isbrae, and since 2015 surface <span class="hlt">mass</span> <span class="hlt">balance</span> and surface displacement has been measured continuously using a combination of sensors. In addition to identify the different components in the altimetry signal, The temporal resolution of the data acquired provide a means to monitor short-term changes in the near-surface firn, and identifying individual events causing surface elevation displacement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C13F1017M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C13F1017M"><span>Atmospheric river impacts on Greenland <span class="hlt">Ice</span> Sheet surface melt and <span class="hlt">mass</span> <span class="hlt">balance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mattingly, K.; Mote, T. L.</p> <p>2017-12-01</p> <p><span class="hlt">Mass</span> loss from the Greenland <span class="hlt">Ice</span> Sheet (GrIS) has accelerated during the early part of the 21st Century. Several episodes of widespread GrIS melt in recent years have coincided with intense poleward moisture transport by atmospheric rivers (ARs), suggesting that variability in the frequency and intensity of these events may be an important driver of the surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) of the GrIS. ARs may contribute to GrIS surface melt through the greenhouse effect of water vapor, the radiative effects of clouds, condensational latent heating within poleward-advected air <span class="hlt">masses</span>, and the energy provided by liquid precipitation. However, ARs may also provide significant positive contributions to GrIS SMB through enhanced snow accumulation. Prior research on the role of ARs in Arctic climate has consisted of case studies of ARs associated with major GrIS melt events or examined the effects of poleward moisture flux on Arctic sea <span class="hlt">ice</span>. In this study, a long-term (1979-2016) record of intense moisture transport events affecting Greenland is compiled using a conventional AR identification algorithm as well as a self-organizing map (SOM) classification applied to integrated water vapor transport (IVT) data from several atmospheric reanalysis datasets. An analysis of AR effects on GrIS melt and SMB is then performed with GrIS surface melt data from passive microwave satellite observations and the Modèle Atmosphérique Régional (MAR) regional climate model. Results show that meltwater production is above normal during and after AR impact days throughout the GrIS during all seasons, with surface melt enhanced most by strong (> 85th percentile IVT) and extreme (> 95th percentile IVT) ARs. This relationship holds at the seasonal scale, as the total amount of water vapor transported to the GrIS by ARs is significantly greater during above-normal melt seasons. ARs exert a more complex influence on SMB. Normal (< 85th percentile IVT) ARs generally do not have a substantial impact on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/sir/2011/5046/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/sir/2011/5046/"><span>Gulkana Glacier, Alaska-<span class="hlt">Mass</span> <span class="hlt">balance</span>, meteorology, and water measurements, 1997-2001</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>March, Rod S.; O'Neel, Shad</p> <p>2011-01-01</p> <p>The measured winter snow, maximum winter snow, net, and annual <span class="hlt">balances</span> for 1997-2001 in the Gulkana Glacier basin are determined at specific points and over the entire glacier area using the meteorological, hydrological, and glaciological data. We provide descriptions of glacier geometry to aid in estimation of conventional and reference surface <span class="hlt">mass</span> <span class="hlt">balances</span> and descriptions of <span class="hlt">ice</span> motion to aid in the understanding of the glacier's response to its changing geometry. These data provide annual estimates for area altitude distribution, equilibrium line altitude, and accumulation area ratio during the study interval. New determinations of historical area altitude distributions are given for 1900 and annually from 1966 to 2001. As original weather instrumentation is nearing the end of its deployment lifespan, we provide new estimates of overlap comparisons and precipitation catch efficiency. During 1997-2001, Gulkana Glacier showed a continued and accelerated negative <span class="hlt">mass</span> <span class="hlt">balance</span> trend, especially below the equilibrium line altitude where thinning was pronounced. <span class="hlt">Ice</span> motion also slowed, which combined with the negative <span class="hlt">mass</span> <span class="hlt">balance</span>, resulted in glacier retreat under a warming climate. Average annual runoff augmentation by glacier shrinkage for 1997-2001 was 25 percent compared to the previous average of 13 percent, in accordance with the measured glacier volume reductions.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11..191I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11..191I"><span>Diagnosing the decline in climatic <span class="hlt">mass</span> <span class="hlt">balance</span> of glaciers in Svalbard over 1957-2014</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ims Østby, Torbjørn; Vikhamar Schuler, Thomas; Ove Hagen, Jon; Hock, Regine; Kohler, Jack; Reijmer, Carleen H.</p> <p>2017-01-01</p> <p>Estimating the long-term <span class="hlt">mass</span> <span class="hlt">balance</span> of the high-Arctic Svalbard archipelago is difficult due to the incomplete geodetic and direct glaciological measurements, both in space and time. To close these gaps, we use a coupled surface energy <span class="hlt">balance</span> and snow pack model to analyse the <span class="hlt">mass</span> changes of all Svalbard glaciers for the period 1957-2014. The model is forced by ERA-40 and ERA-Interim reanalysis data, downscaled to 1 km resolution. The model is validated using snow/firn temperature and density measurements, <span class="hlt">mass</span> <span class="hlt">balance</span> from stakes and <span class="hlt">ice</span> cores, meteorological measurements, snow depths from radar profiles and remotely sensed surface albedo and skin temperatures. Overall model performance is good, but it varies regionally. Over the entire period the model yields a climatic <span class="hlt">mass</span> <span class="hlt">balance</span> of 8.2 cm w. e. yr-1, which corresponds to a <span class="hlt">mass</span> input of 175 Gt. Climatic <span class="hlt">mass</span> <span class="hlt">balance</span> has a linear trend of -1.4 ± 0.4 cm w. e. yr-2 with a shift from a positive to a negative regime around 1980. Modelled <span class="hlt">mass</span> <span class="hlt">balance</span> exhibits large interannual variability, which is controlled by summer temperatures and further amplified by the albedo feedback. For the recent period 2004-2013 climatic <span class="hlt">mass</span> <span class="hlt">balance</span> was -21 cm w. e. yr-1, and accounting for frontal ablation estimated by Błaszczyk et al.(2009) yields a total Svalbard <span class="hlt">mass</span> <span class="hlt">balance</span> of -39 cm w. e. yr-1 for this 10-year period. In terms of eustatic sea level, this corresponds to a rise of 0.037 mm yr-1. Refreezing of water in snow and firn is substantial at 22 cm w. e. yr-1 or 26 % of total annual accumulation. However, as warming leads to reduced firn area over the period, refreezing decreases both absolutely and relative to the total accumulation. Negative <span class="hlt">mass</span> <span class="hlt">balance</span> and elevated equilibrium line altitudes (ELAs) resulted in massive reduction of the thick (> 2 m) firn extent and an increase in the superimposed <span class="hlt">ice</span>, thin (< 2 m) firn and bare <span class="hlt">ice</span> extents. Atmospheric warming also leads to a marked change in the thermal regime</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C12B..05S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C12B..05S"><span>Surface <span class="hlt">mass</span> <span class="hlt">balance</span> model evaluation from satellite and airborne lidar mapping</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sutterley, T. C.; Velicogna, I.; Fettweis, X.; van den Broeke, M. R.</p> <p>2016-12-01</p> <p>We present estimates of Greenland <span class="hlt">Ice</span> Sheet (GrIS) surface elevation change from a novel combination of satellite and airborne laser altimetry measurements. Our method combines measurements from the Airborne Topographic Mapper (ATM), the Land, Vegetation and <span class="hlt">Ice</span> Sensor (LVIS) and ICESat-1 to generate elevation change rates at high spatial resolution. This method allows to extend the records of each instrument, increases the overall spatial coverage compared to a single instrument, and produces high-quality, coherent maps of surface elevation change. In addition by combining the lidar datasets, we are able to investigate seasonal and interannual surface elevation change for years where Spring and Fall Operation <span class="hlt">Ice</span>Bridge campaigns are available. We validate our method by comparing with the standard NSIDC elevation change product calculated using overlapping Level-1B ATM data. We use the altimetry-derived <span class="hlt">mass</span> changes to evaluate the uncertainty in surface <span class="hlt">mass</span> <span class="hlt">balance</span>, particularly in the runoff component, from two Regional Climate Models (RCM's), the Regional Atmospheric Climate Model (RACMO) and the Modéle Atmosphérique Régional (MAR), and one Global Climate Model (GCM), MERRA2/GEOS-5. We investigate locations with low <span class="hlt">ice</span> sheet surface velocities that are within the estimated ablation zones of each regional climate model. We find that the surface <span class="hlt">mass</span> <span class="hlt">balance</span> outputs from RACMO and MAR show good correspondence with <span class="hlt">mass</span> changes derived from surface elevation changes over long periods. At two sites in Northeast Greenland (NEGIS), the MAR model has better correspondence with the altimetry estimate. We find that the differences at these locations are primarily due to the characterization of meltwater refreeze within the <span class="hlt">ice</span> sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140006604','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140006604"><span>Extent of Low-accumulation 'Wind Glaze' Areas on the East Antarctic Plateau: Implications for Continental <span class="hlt">Ice</span> <span class="hlt">Mass</span> <span class="hlt">Balance</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Scambos, Theodore A.; Frezzotti, Massimo; Haran, T.; Bohlander, J.; Lenaerts, J. T. M.; Van Den Broeke, M. R.; Jezek, K.; Long, D.; Urbini, S.; Farness, K.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20140006604'); toggleEditAbsImage('author_20140006604_show'); toggleEditAbsImage('author_20140006604_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20140006604_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20140006604_hide"></p> <p>2012-01-01</p> <p>Persistent katabatic winds form widely distributed localized areas of near-zero net surface accumulation on the East Antarctic <span class="hlt">ice</span> sheet (EAIS) plateau. These areas have been called 'glaze' surfaces due to their polished appearance. They are typically 2-200 square kilometers in area and are found on leeward slopes of <span class="hlt">ice</span>-sheet undulations and megadunes. Adjacent, leeward high-accumulation regions (isolated dunes) are generally smaller and do not compensate for the local low in surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB). We use a combination of satellite remote sensing and field-gathered datasets to map the extent of wind glaze in the EAIS above 1500m elevation. Mapping criteria are derived from distinctive surface and subsurface characteristics of glaze areas resulting from many years of intense annual temperature cycling without significant burial. Our results show that 11.2 plus or minus 1.7%, or 950 plus or minus 143 x 10(exp 3) square kilometers, of the EAIS above 1500m is wind glaze. Studies of SMB interpolate values across glaze regions, leading to overestimates of net <span class="hlt">mass</span> input. Using our derived wind-glaze extent, we estimate this excess in three recent models of Antarctic SMB at 46-82 Gt. The lowest-input model appears to best match the mean in regions of extensive wind glaze.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950053174&hterms=3G&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3D3G','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950053174&hterms=3G&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3D3G"><span>Present-day Antarctic <span class="hlt">ice</span> <span class="hlt">mass</span> changes and crustal motion</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>James, Thomas S.; Ivins, Erik R.</p> <p>1995-01-01</p> <p>The peak vertical velocities predicted by three realistic, but contrasting, present-day scenarios of Antarctic <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> are found to be of the order of several mm/a. One scenario predicts local uplift rates in excess of 5 mm/a. These rates are small compared to the peak Antarctic vertical velocities of the <span class="hlt">ICE</span>-3G glacial rebound model, which are in excess of 20 mm/a. If the Holocene Antarctic deglaciation history protrayed in <span class="hlt">ICE</span>-3G is realistic, and if regional upper mantle viscosity is not an order of magnitude below 10(exp 21) Pa(dot)s, then a vast geographical region in West Antarctica is uplifting at a rate that could be detected by a future Global Positioning System (GPS) campaign. While present-day scenarios predict small vertical crustal velocities, their overall continent-ocean <span class="hlt">mass</span> exchange is large enough to account for a substantial portion of the observed secular polar motion (omega m(arrow dot)) and time-varying zonal gravity field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990100907&hterms=3G&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3D3G','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990100907&hterms=3G&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3D3G"><span>Present-day Antarctic <span class="hlt">Ice</span> <span class="hlt">Mass</span> Changes and Crustal Motion</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>James, Thomas S.; Ivins, Erik R.</p> <p>1995-01-01</p> <p>The peak vertical velocities predicted by three realistic, but contrasting, present-day scenarios of Antarctic <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> are found to be of the order of several mm/a. One scenario predicts local uplift rates in excess of 5 mm/a. These rates are small compared to the peak Antarctic vertical velocities of the <span class="hlt">ICE</span>-3G glacial rebound model, which are in excess of 20 mm/a. If the Holocene Antarctic deglaciation history portrayed in <span class="hlt">ICE</span>-3G is realistic, and if regional upper mantle viscosity is not an order of magnitude below 10(exp 21) pa s, then a vast geographical region in West Antarctica is uplifting at a rate that could be detected by a future Global Positioning System (GPS) campaign. While present-day scenarios predict small vertical crustal velocities, their overall continent-ocean <span class="hlt">mass</span> exchange is large enough to account for a substantial portion of the observed secular polar motion ((Omega)m(bar)) and time-varying zonal gravity field J(sub 1).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.C53E0718A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.C53E0718A"><span>Remote Sensing Estimates of Glacier <span class="hlt">Mass</span> <span class="hlt">Balance</span> Changes in the Himalayas of Nepal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ambinakudige, S.; Joshi, K.</p> <p>2011-12-01</p> <p> 3N and 3B were used as left and right images respectively in the process of creating the DEM. Minimum elevation in these images was 1500m and maximum elevation was 8550m. Coordinates and elevation values from topographic maps in the non-glaciated region were used as GCPs while creating absolute DEMs. Considering the high terrain of the study area, we used large number of GCPs, tie points, higher windows search area, and high terrain parameters to improve DEM accuracy. Since these images were acquired in September, the accumulation area was clearly visible. The Global land <span class="hlt">ice</span> measurement (GLIMS) database which is maintained at the National Snow and <span class="hlt">Ice</span> Data Center (NSIDC) was used to delineate glacier boundaries. The differences between the elevations in consecutive years in the accumulation area were calculated using raster calculator. The total elevation differences were then multiplied by the area to estimate the change in volume. Density of <span class="hlt">ice</span> used in <span class="hlt">mass</span> <span class="hlt">balance</span> calculation was 900kg per sq. meters. The result indicated that while there was a decrease in <span class="hlt">mass</span> <span class="hlt">balance</span> of some glaciers, some showed an increase in <span class="hlt">mass</span> <span class="hlt">balance</span> during the study period. The study helped to develop a data on <span class="hlt">mass</span> <span class="hlt">balance</span> change in some major glaciers in the Himalayas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.7328C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.7328C"><span><span class="hlt">Mass</span> <span class="hlt">balance</span> reassessment of glaciers draining into the Abbot and Getz <span class="hlt">Ice</span> Shelves of West Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chuter, S. J.; Martín-Español, A.; Wouters, B.; Bamber, J. L.</p> <p>2017-07-01</p> <p>We present a reassessment of input-output method <span class="hlt">ice</span> <span class="hlt">mass</span> budget estimates for the Abbot and Getz regions of West Antarctica using CryoSat-2-derived <span class="hlt">ice</span> thickness estimates. The <span class="hlt">mass</span> budget is 8 ± 6 Gt yr-1 and 5 ± 17 Gt yr-1 for the Abbot and Getz sectors, respectively, for the period 2006-2008. Over the Abbot region, our results resolve a previous discrepancy with elevation rates from altimetry, due to a previous 30% overestimation of <span class="hlt">ice</span> thickness. For the Getz sector, our results are at the more positive bound of estimates from other techniques. Grounding line velocity increases up to 20% between 2007 and 2014 alongside mean elevation rates of -0.67 ± 0.13 m yr-1 between 2010 and 2013 indicate the onset of a dynamic thinning signal. Mean snowfall trends of -0.33 m yr-1 water equivalent since 2006 indicate recent <span class="hlt">mass</span> trends are driven by both <span class="hlt">ice</span> dynamics and surface processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.water.usgs.gov/sir20045089/','USGSPUBS'); return false;" href="http://pubs.water.usgs.gov/sir20045089/"><span>Water, <span class="hlt">ice</span>, and meteorological measurements at South Cascade Glacier, Washington, <span class="hlt">balance</span> year 2002</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bidlake, William R.; Josberger, Edward G.; Savoca, Mark E.</p> <p>2004-01-01</p> <p>Winter snow accumulation and summer snow and <span class="hlt">ice</span> ablation were measured at South Cascade Glacier, Washington, to estimate glacier <span class="hlt">mass</span> <span class="hlt">balance</span> quantities for <span class="hlt">balance</span> year 2002. The 2002 glacier-average maximum winter snow <span class="hlt">balance</span> was 4.02 meters, the second largest since 1959. The 2002 glacier summer, net, and annual (water year) <span class="hlt">balances</span> were -3.47, 0.55, and 0.54 meters, respectively. The area of the glacier near the end of the <span class="hlt">balance</span> year was 1.92 square kilometers, and the equilibrium-line altitude and the accumulation area ratio were 1,820 meters and 0.84, respectively. During September 20, 2001 to September 13, 2002, the terminus retreated 4 meters, and computed average <span class="hlt">ice</span> speeds in the ablation area ranged from 7.8 to 20.7 meters per year. Runoff from the subbasin containing the glacier and from an adjacent non-glacierized basin were measured during part of the 2002 water year. Air temperature, precipitation, atmospheric water-vapor pressure, wind speed and incoming solar radiation were measured at selected locations near the glacier.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/wri/2000/4006/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/wri/2000/4006/report.pdf"><span>Water, <span class="hlt">ice</span>, and meteorological measurements at South Cascade Glacier, Washington, 1986-1991 <span class="hlt">balance</span> years</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Krimmel, Robert M.</p> <p>2000-01-01</p> <p><span class="hlt">Mass</span> <span class="hlt">balance</span> and climate variables are reported for South Cascade Glacier, Washington, for the years 1986-91. These variables include air temperature, precipitation, water runoff, snow accumulation, snow and <span class="hlt">ice</span> melt terminus position, surface level, and <span class="hlt">ice</span> speed. Data are reduced to daily and monthly values where appropriate. The glacier-averaged values of spring snow accumulation and fall net <span class="hlt">balance</span> given in this report differ from previous results because amore complete analysis is made. Snow accumulation values for the1986-91 period ranged from 3.54 (water equivalent) meters in 1991 to2.04 meters in 1987. Net <span class="hlt">balance</span> values ranged from 0.07 meters in1991 to -2.06 meters in 1987. The glacier became much smaller during the 1986-91 period and retreated a cumulative 50 meters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C51A0965H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C51A0965H"><span>Sea <span class="hlt">Ice</span> <span class="hlt">Mass</span> Reconciliation Exercise (SIMRE) for altimetry derived sea <span class="hlt">ice</span> thickness data sets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hendricks, S.; Haas, C.; Tsamados, M.; Kwok, R.; Kurtz, N. T.; Rinne, E. J.; Uotila, P.; Stroeve, J.</p> <p>2017-12-01</p> <p>Satellite altimetry is the primary remote sensing data source for retrieval of Arctic sea-<span class="hlt">ice</span> thickness. Observational data sets are available from current and previous missions, namely ESA's Envisat and CryoSat as well as NASA ICESat. In addition, freeboard results have been published from the earlier ESA ERS missions and candidates for new data products are the Sentinel-3 constellation, the CNES AltiKa mission and NASA laser altimeter successor ICESat-2. With all the different aspects of sensor type and orbit configuration, all missions have unique properties. In addition, thickness retrieval algorithms have evolved over time and data centers have developed different strategies. These strategies may vary in choice of auxiliary data sets, algorithm parts and product resolution and masking. The Sea <span class="hlt">Ice</span> <span class="hlt">Mass</span> Reconciliation Exercise (SIMRE) is a project by the sea-<span class="hlt">ice</span> radar altimetry community to bridge the challenges of comparing data sets across missions and algorithms. The ESA Arctic+ research program facilitates this project with the objective to collect existing data sets and to derive a reconciled estimate of Arctic sea <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>. Starting with CryoSat-2 products, we compare results from different data centers (UCL, AWI, NASA JPL & NASA GSFC) at full resolution along selected orbits with independent <span class="hlt">ice</span> thickness estimates. Three regions representative of first-year <span class="hlt">ice</span>, multiyear <span class="hlt">ice</span> and mixed <span class="hlt">ice</span> conditions are used to compare the difference in thickness and thickness change between products over the seasonal cycle. We present first results and provide an outline for the further development of SIMRE activities. The methodology for comparing data sets is designed to be extendible and the project is open to contributions by interested groups. Model results of sea <span class="hlt">ice</span> thickness will be added in a later phase of the project to extend the scope of SIMRE beyond EO products.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740004942','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740004942"><span>Evaluation of glacier <span class="hlt">mass</span> <span class="hlt">balance</span> by observing variations in transient snowline positions. [Jostedalsbreen <span class="hlt">ice</span> cap, Norway</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oestrem, G. (Principal Investigator)</p> <p>1973-01-01</p> <p>The author has identified the following significant results. The transient snowline on five outlet glaciers from the Jostedalsbreen <span class="hlt">ice</span>-cap in Southwestern Norway could be determined from ERTS-1 image 1336-10260, when bands MSS 5, 6, and 7 were combined in an additive color viewer. The snowline was situated at a very low altitude at the time of imagery (24 June 1973) indicating that glacier melt was behind normal schedule, a fact that has a hydrologic bearing: one could expect less melt water in the streams. The idea to use ERTS-1 imagery in snowline determinations proved realistic and relatively easy to apply in practice. The method will be useful to estimate the glaciers' <span class="hlt">mass</span> <span class="hlt">balance</span> for large areas, provided some ground truth observations are made. Images from the end of the melt season are of course vital in this work.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C21A0719B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C21A0719B"><span>Freshwater fluxes into the subpolar North Atlantic from secular trends in Arctic land <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bamber, J. L.; Enderlin, E. M.; Howat, I. M.; Wouters, B.; van den Broeke, M.</p> <p>2015-12-01</p> <p>Freshwater fluxes (FWF) from river runoff and precipitation minus evaporation for the pan Arctic seas are relatively well documented and prescribed in ocean GCMs. Fluxes from Greenland and Arctic glaciers and <span class="hlt">ice</span> caps on the other hand are generally ignored, despite their potential impacts on ocean circulation and marine biology and growing evidence for changes to the hydrography of parts of the subpolar North Atlantic. In a previous study we determined the FWF from Greenland for the period 1958-2010 using a combination of observations and regional climate modeling. Here, we update the analysis with data from new satellite observations to extend the record both in space and time. The new FWF estimates cover the period 1958-2014 and include the Canadian, Russian and Norwegian Arctic (Svalbard) in addition to the contributions from Greenland. We combine satellite altimetry (including CryoSat 2) with grounding line flux data, regional climate modeling of surface <span class="hlt">mass</span> <span class="hlt">balance</span> and gravimetry to produce consistent estimates of solid <span class="hlt">ice</span> and liquid FWF into the Arctic and North Atlantic Oceans. The total cumulative FWF anomaly from land <span class="hlt">ice</span> <span class="hlt">mass</span> loss started to increase significantly in the mid 1990s and now exceeds 5000 km^3, a value that is about half of the Great Salinity Anomaly of the 1970s. The majority of the anomaly is entering two key areas of deep water overturning in the Labrador and Irminger Seas, at a rate that has been increasing steadily over the last ~20 years. Since the mid 2000s, however, the Canadian Arctic archipelago has been making a significant contribution to the FW anomaly entering Baffin Bay. Tracer experiments with eddy-permitting ocean GCMs suggest that the FW input from southern Greenland and the Canadian Arctic should accumulate in Baffin Bay with the potential to affect geostrophic circulation, stratification in the region and possibly the strength of the Atlantic Meridional Overturning Circulation. We also examine the trajectory of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C51A0962S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C51A0962S"><span>A 25-year Record of Antarctic <span class="hlt">Ice</span> Sheet Elevation and <span class="hlt">Mass</span> Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shepherd, A.; Muir, A. S.; Sundal, A.; McMillan, M.; Briggs, K.; Hogg, A.; Engdahl, M.; Gilbert, L.</p> <p>2017-12-01</p> <p>Since 1992, the European Remote-Sensing (ERS-1 and ERS-2), ENVISAT, and CryoSat-2 satellite radar altimeters have measured the Antarctic <span class="hlt">ice</span> sheet surface elevation, repeatedly, at approximately monthly intervals. These data constitute the longest continuous record of <span class="hlt">ice</span> sheet wide change. In this paper, we use these observations to determine changes in the elevation, volume and <span class="hlt">mass</span> of the East Antarctic and West Antarctic <span class="hlt">ice</span> sheets, and of parts of the Antarctic Peninsula <span class="hlt">ice</span> sheet, over a 25-year period. The root mean square difference between elevation rates computed from our survey and 257,296 estimates determined from airborne laser measurements is 54 cm/yr. The longevity of the satellite altimeter data record allows to identify and chart the evolution of changes associated with meteorology and <span class="hlt">ice</span> flow, and we estimate that 3.6 % of the continental <span class="hlt">ice</span> sheet, and 21.7 % of West Antarctica, is in a state of dynamical imbalance. Based on this partitioning, we estimate the <span class="hlt">mass</span> <span class="hlt">balance</span> of the East and West Antarctic <span class="hlt">ice</span> sheet drainage basins and the root mean square difference between these and independent estimates derived from satellite gravimetry is less than 5 Gt yr-1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.415..134H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.415..134H"><span>Accelerated West Antarctic <span class="hlt">ice</span> <span class="hlt">mass</span> loss continues to outpace East Antarctic gains</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harig, Christopher; Simons, Frederik J.</p> <p>2015-04-01</p> <p>While multiple data sources have confirmed that Antarctica is losing <span class="hlt">ice</span> at an accelerating rate, different measurement techniques estimate the details of its geographically highly variable <span class="hlt">mass</span> <span class="hlt">balance</span> with different levels of accuracy, spatio-temporal resolution, and coverage. Some scope remains for methodological improvements using a single data type. In this study we report our progress in increasing the accuracy and spatial resolution of time-variable gravimetry from the Gravity Recovery and Climate Experiment (GRACE). We determine the geographic pattern of <span class="hlt">ice</span> <span class="hlt">mass</span> change in Antarctica between January 2003 and June 2014, accounting for glacio-isostatic adjustment (GIA) using the IJ05_R2 model. Expressing the unknown signal in a sparse Slepian basis constructed by optimization to prevent leakage out of the regions of interest, we use robust signal processing and statistical estimation methods. Applying those to the latest time series of monthly GRACE solutions we map Antarctica's <span class="hlt">mass</span> loss in space and time as well as can be recovered from satellite gravity alone. Ignoring GIA model uncertainty, over the period 2003-2014, West Antarctica has been losing <span class="hlt">ice</span> <span class="hlt">mass</span> at a rate of - 121 ± 8 Gt /yr and has experienced large acceleration of <span class="hlt">ice</span> <span class="hlt">mass</span> losses along the Amundsen Sea coast of - 18 ± 5 Gt /yr2, doubling the <span class="hlt">mass</span> loss rate in the past six years. The Antarctic Peninsula shows slightly accelerating <span class="hlt">ice</span> <span class="hlt">mass</span> loss, with larger accelerated losses in the southern half of the Peninsula. <span class="hlt">Ice</span> <span class="hlt">mass</span> gains due to snowfall in Dronning Maud Land have continued to add about half the amount of West Antarctica's loss back onto the continent over the last decade. We estimate the overall <span class="hlt">mass</span> losses from Antarctica since January 2003 at - 92 ± 10 Gt /yr.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080046255','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080046255"><span>Greenland <span class="hlt">Ice</span> Sheet Surface Temperature, Melt, and <span class="hlt">Mass</span> Loss: 2000-2006</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hall, Dorothy K.; Williams, Richard S., Jr.; Luthcke, Scott B.; DiGirolamo, Nocolo</p> <p>2007-01-01</p> <p>Extensive melt on the Greenland <span class="hlt">Ice</span> Sheet has been documented by a variety of ground and satellite measurements in recent years. If the well-documented warming continues in the Arctic, melting of the Greenland <span class="hlt">Ice</span> Sheet will likely accelerate, contributing to sea-level rise. Modeling studies indicate that an annual or summer temperature rise of 1 C on the <span class="hlt">ice</span> sheet will increase melt by 20-50% therefore, surface temperature is one of the most important <span class="hlt">ice</span>-sheet parameters to study for analysis of changes in the <span class="hlt">mass</span> <span class="hlt">balance</span> of the <span class="hlt">ice</span>-sheet. The Greenland <span class="hlt">Ice</span> Sheet contains enough water to produce a rise in eustatic sea level of up to 7.0 m if the <span class="hlt">ice</span> were to melt completely. However, even small changes (centimeters) in sea level would cause important economic and societal consequences in the world's major coastal cities thus it is extremely important to monitor changes in the <span class="hlt">ice</span>-sheet surface temperature and to ultimately quantify these changes in terms of amount of sea-level rise. We have compiled a high-resolution, daily time series of surface temperature of the Greenland <span class="hlt">Ice</span> Sheet, using the I-km resolution, clear-sky land-surface temperature (LST) standard product from the Moderate-Resolution Imaging Spectroradiometer (MODIS), from 2000 - 2006. We also use Gravity Recovery and Climate Experiment (GRACE) data, averaged over 10-day periods, to measure change in <span class="hlt">mass</span> of the <span class="hlt">ice</span> sheet as it melt and snow accumulates. Surface temperature can be used to determine frequency of surface melt, timing of the start and the end of the melt season, and duration of melt. In conjunction with GRACE data, it can also be used to analyze timing of <span class="hlt">ice</span>-sheet <span class="hlt">mass</span> loss and gain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28361871','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28361871"><span>A tipping point in refreezing accelerates <span class="hlt">mass</span> loss of Greenland's glaciers and <span class="hlt">ice</span> caps.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Noël, B; van de Berg, W J; Lhermitte, S; Wouters, B; Machguth, H; Howat, I; Citterio, M; Moholdt, G; Lenaerts, J T M; van den Broeke, M R</p> <p>2017-03-31</p> <p>Melting of the Greenland <span class="hlt">ice</span> sheet (GrIS) and its peripheral glaciers and <span class="hlt">ice</span> caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS <span class="hlt">mass</span> loss are well studied, the spatial and temporal evolution of GICs <span class="hlt">mass</span> loss and the acting processes have remained unclear. Here we use a novel, 1 km surface <span class="hlt">mass</span> <span class="hlt">balance</span> product, evaluated against in situ and remote sensing data, to identify 1997 (±5 years) as a tipping point for GICs <span class="hlt">mass</span> <span class="hlt">balance</span>. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 <span class="hlt">mass</span> loss to 36±16 Gt -1 , or ∼14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5380968','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5380968"><span>A tipping point in refreezing accelerates <span class="hlt">mass</span> loss of Greenland's glaciers and <span class="hlt">ice</span> caps</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Noël, B.; van de Berg, W. J; Lhermitte, S.; Wouters, B.; Machguth, H.; Howat, I.; Citterio, M.; Moholdt, G.; Lenaerts, J. T. M.; van den Broeke, M. R.</p> <p>2017-01-01</p> <p>Melting of the Greenland <span class="hlt">ice</span> sheet (GrIS) and its peripheral glaciers and <span class="hlt">ice</span> caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS <span class="hlt">mass</span> loss are well studied, the spatial and temporal evolution of GICs <span class="hlt">mass</span> loss and the acting processes have remained unclear. Here we use a novel, 1 km surface <span class="hlt">mass</span> <span class="hlt">balance</span> product, evaluated against in situ and remote sensing data, to identify 1997 (±5 years) as a tipping point for GICs <span class="hlt">mass</span> <span class="hlt">balance</span>. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 <span class="hlt">mass</span> loss to 36±16 Gt−1, or ∼14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming. PMID:28361871</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCo...814730N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCo...814730N"><span>A tipping point in refreezing accelerates <span class="hlt">mass</span> loss of Greenland's glaciers and <span class="hlt">ice</span> caps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Noël, B.; van de Berg, W. J.; Lhermitte, S.; Wouters, B.; Machguth, H.; Howat, I.; Citterio, M.; Moholdt, G.; Lenaerts, J. T. M.; van den Broeke, M. R.</p> <p>2017-03-01</p> <p>Melting of the Greenland <span class="hlt">ice</span> sheet (GrIS) and its peripheral glaciers and <span class="hlt">ice</span> caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS <span class="hlt">mass</span> loss are well studied, the spatial and temporal evolution of GICs <span class="hlt">mass</span> loss and the acting processes have remained unclear. Here we use a novel, 1 km surface <span class="hlt">mass</span> <span class="hlt">balance</span> product, evaluated against in situ and remote sensing data, to identify 1997 (+/-5 years) as a tipping point for GICs <span class="hlt">mass</span> <span class="hlt">balance</span>. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 <span class="hlt">mass</span> loss to 36+/-16 Gt-1, or ~14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C23B0613H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C23B0613H"><span>Polar <span class="hlt">Ice</span> Caps: a Canary for the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Honsaker, W.; Lowell, T. V.; Sagredo, E.; Kelly, M. A.; Hall, B. L.</p> <p>2010-12-01</p> <p><span class="hlt">Ice</span> caps are glacier <span class="hlt">masses</span> that are highly sensitive to climate change. Because of their hypsometry they can have a binary state. When relatively slight changes in the equilibrium line altitude (ELA) either intersect or rise above the land the <span class="hlt">ice</span> can become established or disappear. Thus these upland <span class="hlt">ice</span> <span class="hlt">masses</span> have a fast response time. Here we consider a way to extract the ELA signal from independent <span class="hlt">ice</span> caps adjacent to the Greenland <span class="hlt">Ice</span> Sheet margin. It may be that these <span class="hlt">ice</span> caps are sensitive trackers of climate change that also impact the <span class="hlt">ice</span> sheet margin. One example is the Istorvet <span class="hlt">Ice</span> Cap located in Liverpool Land, East Greenland (70.881°N, 22.156°W). The <span class="hlt">ice</span> cap topography and the underlying bedrock surface dips to the north, with peak elevation of the current <span class="hlt">ice</span> ranging in elevation from 1050 to 745 m.a.s.l. On the eastern side of the <span class="hlt">ice</span> <span class="hlt">mass</span> the outlet glaciers extending down to sea level. The western margin has several small lobes in topographic depressions, with the margin reaching down to 300 m.a.s.l. Topographic highs separate the <span class="hlt">ice</span> cap into at least 5 main catchments, each having a pair of outlet lobes toward either side of the <span class="hlt">ice</span> cap. Because of the regional bedrock slope each catchment has its own elevation range. Therefore, as the ELA changes it is possible for some catchments of the <span class="hlt">ice</span> cap to experience positive <span class="hlt">mass</span> <span class="hlt">balance</span> while others have a negative <span class="hlt">balance</span>. Based on weather observations we estimate the present day ELA to be ~1000 m.a.s.l, meaning <span class="hlt">mass</span> <span class="hlt">balance</span> is negative for the majority of the <span class="hlt">ice</span> cap. By tracking glacier presence/absence in these different catchments, we can reconstruct small changes in the ELA. Another example is the High <span class="hlt">Ice</span> Cap (informal name) in Milne Land (70.903°N, 25.626°W, 1080 m), East Greenland. Here at least 4 unconformities in <span class="hlt">ice</span> layers found near the southern margin of the <span class="hlt">ice</span> cap record changing intervals of accumulation and ablation. Therefore, this location may also be sensitive to slight</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27386524','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27386524"><span>Monitoring southwest Greenland's <span class="hlt">ice</span> sheet melt with ambient seismic noise.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mordret, Aurélien; Mikesell, T Dylan; Harig, Christopher; Lipovsky, Bradley P; Prieto, Germán A</p> <p>2016-05-01</p> <p>The Greenland <span class="hlt">ice</span> sheet presently accounts for ~70% of global <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss. Because this <span class="hlt">mass</span> loss is associated with sea-level rise at a rate of 0.7 mm/year, the development of improved monitoring techniques to observe ongoing changes in <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> is of paramount concern. Spaceborne <span class="hlt">mass</span> <span class="hlt">balance</span> techniques are commonly used; however, they are inadequate for many purposes because of their low spatial and/or temporal resolution. We demonstrate that small variations in seismic wave speed in Earth's crust, as measured with the correlation of seismic noise, may be used to infer seasonal <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span>. Seasonal loading and unloading of glacial <span class="hlt">mass</span> induces strain in the crust, and these strains then result in seismic velocity changes due to poroelastic processes. Our method provides a new and independent way of monitoring (in near real time) <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span>, yielding new constraints on <span class="hlt">ice</span> sheet evolution and its contribution to global sea-level changes. An increased number of seismic stations in the vicinity of <span class="hlt">ice</span> sheets will enhance our ability to create detailed space-time records of <span class="hlt">ice</span> <span class="hlt">mass</span> variations.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10.2501P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10.2501P"><span><span class="hlt">Ice</span> core evidence for a 20th century increase in surface <span class="hlt">mass</span> <span class="hlt">balance</span> in coastal Dronning Maud Land, East Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Philippe, Morgane; Tison, Jean-Louis; Fjøsne, Karen; Hubbard, Bryn; Kjær, Helle A.; Lenaerts, Jan T. M.; Drews, Reinhard; Sheldon, Simon G.; De Bondt, Kevin; Claeys, Philippe; Pattyn, Frank</p> <p>2016-10-01</p> <p><span class="hlt">Ice</span> cores provide temporal records of surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB). Coastal areas of Antarctica have relatively high and variable SMB, but are under-represented in records spanning more than 100 years. Here we present SMB reconstruction from a 120 m-long <span class="hlt">ice</span> core drilled in 2012 on the Derwael <span class="hlt">Ice</span> Rise, coastal Dronning Maud Land, East Antarctica. Water stable isotope (δ18O and δD) stratigraphy is supplemented by discontinuous major ion profiles and continuous electrical conductivity measurements. The base of the <span class="hlt">ice</span> core is dated to AD 1759 ± 16, providing a climate proxy for the past ˜ 250 years. The core's annual layer thickness history is combined with its gravimetric density profile to reconstruct the site's SMB history, corrected for the influence of <span class="hlt">ice</span> deformation. The mean SMB for the core's entire history is 0.47 ± 0.02 m water equivalent (w.e.) a-1. The time series of reconstructed annual SMB shows high variability, but a general increase beginning in the 20th century. This increase is particularly marked during the last 50 years (1962-2011), which yields mean SMB of 0.61 ± 0.01 m w.e. a-1. This trend is compared with other reported SMB data in Antarctica, generally showing a high spatial variability. Output of the fully coupled Community Earth System Model (CESM) suggests that, although atmospheric circulation is the main factor influencing SMB, variability in sea surface temperatures and sea <span class="hlt">ice</span> cover in the precipitation source region also explain part of the variability in SMB. Local snow redistribution can also influence interannual variability but is unlikely to influence long-term trends significantly. This is the first record from a coastal <span class="hlt">ice</span> core in East Antarctica to show an increase in SMB beginning in the early 20th century and particularly marked during the last 50 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C23C0797N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C23C0797N"><span>A downscaled 1 km dataset of daily Greenland <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> <span class="hlt">balance</span> components (1958-2014)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Noel, B.; Van De Berg, W. J.; Fettweis, X.; Machguth, H.; Howat, I. M.; van den Broeke, M. R.</p> <p>2015-12-01</p> <p>The current spatial resolution in regional climate models (RCMs), typically around 5 to 20 km, remains too coarse to accurately reproduce the spatial variability in surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) components over the narrow ablation zones, marginal outlet glaciers and neighbouring <span class="hlt">ice</span> caps of the Greenland <span class="hlt">ice</span> sheet (GrIS). In these topographically rough terrains, the SMB components are highly dependent on local variations in topography. However, the relatively low-resolution elevation and <span class="hlt">ice</span> mask prescribed in RCMs contribute to significantly underestimate melt and runoff in these regions due to unresolved valley glaciers and fjords. Therefore, near-km resolution topography is essential to better capture SMB variability in these spatially restricted regions. We present a 1 km resolution dataset of daily GrIS SMB covering the period 1958-2014, which is statistically downscaled from data of the polar regional climate model RACMO2.3 at 11 km, using an elevation dependence. The dataset includes all individual SMB components projected on the elevation and <span class="hlt">ice</span> mask from the GIMP DEM, down-sampled to 1 km. Daily runoff and sublimation are interpolated to the 1 km topography using a local regression to elevation valid for each day specifically; daily precipitation is bi-linearly downscaled without elevation corrections. The daily SMB dataset is then reconstructed by summing downscaled precipitation, sublimation and runoff. High-resolution elevation and <span class="hlt">ice</span> mask allow for properly resolving the narrow ablation zones and valley glaciers at the GrIS margins, leading to significant increase in runoff estimate. In these regions, and especially over narrow glaciers tongues, the downscaled products improve on the original RACMO2.3 outputs by better representing local SMB patterns through a gradual ablation increase towards the GrIS margins. We discuss the impact of downscaling on the SMB components in a case study for a spatially restricted region, where large elevation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRD..118.2119R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRD..118.2119R"><span>Antarctic <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss estimates using Modified Antarctic Mapping Mission surface flow observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ren, Diandong; Leslie, Lance M.; Lynch, Mervyn J.</p> <p>2013-03-01</p> <p>The long residence time of <span class="hlt">ice</span> and the relatively gentle slopes of the Antarctica <span class="hlt">Ice</span> Sheet make basal sliding a unique positive feedback mechanism in enhancing <span class="hlt">ice</span> discharge along preferred routes. The highly organized <span class="hlt">ice</span> stream channels extending to the interior from the lower reach of the outlets are a manifestation of the role of basal granular material in enhancing the <span class="hlt">ice</span> flow. In this study, constraining the model-simulated year 2000 <span class="hlt">ice</span> flow fields with surface velocities obtained from InSAR measurements permits retrieval of the basal sliding parameters. Forward integrations of the <span class="hlt">ice</span> model driven by atmospheric and oceanic parameters from coupled general circulation models under different emission scenarios provide a range of estimates of total <span class="hlt">ice</span> <span class="hlt">mass</span> loss during the 21st century. The total <span class="hlt">mass</span> loss rate has a small intermodel and interscenario spread, rising from approximately -160 km3/yr at present to approximately -220 km3/yr by 2100. The accelerated <span class="hlt">mass</span> loss rate of the Antarctica <span class="hlt">Ice</span> Sheet in a warming climate is due primarily to a dynamic response in the form of an increase in <span class="hlt">ice</span> flow speed. <span class="hlt">Ice</span> shelves contribute to this feedback through a reduced buttressing effect due to more frequent systematic, tabular calving events. For example, by 2100 the Ross <span class="hlt">Ice</span> Shelf is projected to shed 40 km3 during each systematic tabular calving. After the frontal section's attrition, the remaining shelf will rebound. Consequently, the submerged cross-sectional area will reduce, as will the buttressing stress. Longitudinal differential warming of ocean temperature contributes to tabular calving. Because of the prevalence of fringe <span class="hlt">ice</span> shelves, oceanic effects likely will play a very important role in the future <span class="hlt">mass</span> <span class="hlt">balance</span> of the Antarctica <span class="hlt">Ice</span> Sheet, under a possible future warming climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.9409F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.9409F"><span>Sensitivity of glacier <span class="hlt">mass</span> <span class="hlt">balance</span> and equilibrium line altitude to climatic change on King George Island, Antarctic Peninsula.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Falk, Ulrike; Lopez, Damian; Silva-Busso, Adrian</p> <p>2017-04-01</p> <p>The South Shetland Islands are located at the northern tip of the Antarctic Peninsula which is among the fastest warming regions on Earth. Surface air temperature increases (ca. 3 K in 50 years) are concurrent with retreating glacier fronts, an increase in melt areas, <span class="hlt">ice</span> surface lowering and rapid break-up and disintegration of <span class="hlt">ice</span> shelves. Observed surface air temperature lapse rates show a high variability during winter months (standard deviations up to ±1.0 K/100 m), and a distinct spatial heterogeneity reflecting the impact of synoptic weather patterns especially during winter glacial <span class="hlt">mass</span> accumulation periods. The increased mesocyclonic activity during the winter time in the study area results in intensified advection of warm, moist air with high temperatures and rain, and leads to melt conditions on the <span class="hlt">ice</span> cap, fixating surface air temperatures to the melting point. The impact on winter accumulation results in even more negative <span class="hlt">mass</span> <span class="hlt">balance</span> estimates. Six years of glaciological measurements on <span class="hlt">mass</span> <span class="hlt">balance</span> stake transects are used with a glacier melt model to assess changes in melt water input to the coastal waters, glacier surface <span class="hlt">mass</span> <span class="hlt">balance</span> and the equilibrium line altitude. The average equilibrium line altitude (ELA) calculated from own glaciological observations for KGI over the time period 2010 - 2015 amounts to ELA=330±100 m. Published studies suggest rather stable condition slightly negative glacier <span class="hlt">mass</span> <span class="hlt">balance</span> until the mid 80's with an ELA of approx. 150 m. The calculated accumulation area ratio suggests rather dramatic changes in extension of the inland <span class="hlt">ice</span> cap for the South Shetland Islands until an equilibrium with concurrent climate conditions is reached.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.5085B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.5085B"><span>Using an SLR inversion to measure the <span class="hlt">mass</span> <span class="hlt">balance</span> of Greenland before and during GRACE</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bonin, Jennifer</p> <p>2016-04-01</p> <p>The GRACE mission has done an admirable job of measuring large-scale <span class="hlt">mass</span> changes over Greenland since its launch in 2002. However before that time, measurements of large-scale <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> were few and far between, leading to a lack of baseline knowledge. High-quality Satellite Laser Ranging (SLR) data existed a decade earlier, but normally has too low a spatial resolution to be used for this purpose. I demonstrate that a least squares inversion technique can reconstitute the SLR data and use it to measure <span class="hlt">ice</span> loss over Greenland. To do so, I first simulate the problem by degrading today's GRACE data to a level comparable with SLR, then demonstrating that the inversion can re-localize Greenland's contribution to the low-resolution signal, giving an accurate time series of <span class="hlt">mass</span> change over all of Greenland which compares well with the full-resolution GRACE estimates. I then utilize that method on the actual SLR data, resulting in an independent 1994-2014 time series of <span class="hlt">mass</span> change over Greenland. I find favorable agreement between the pure-SLR inverted results and the 2012 <span class="hlt">Ice</span>-sheet <span class="hlt">Mass</span> <span class="hlt">Balance</span> Inter-comparison Exercise (IMBIE) results, which are largely based on the "input-output" modeling method before GRACE's launch.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8877C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8877C"><span>Impact of the global SST gradients changes on the Antarctic <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> <span class="hlt">balance</span> through the Plio/Pliocene transition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Colleoni, Florence; Florindo, Fabio; McKay, Robert; Golledge, Nicholas; Sangiorgi, Francesca; Montoli, Enea; Masina, Simona; Cherchi, Annalisa; De Santis, Laura</p> <p>2017-04-01</p> <p>Sea Surface Temperatures (SST) reconstructions have shown that the Pliocene global zonal and meridional temperature gradients were different from today, implying changes of atmospheric and oceanic circulations, and thus of the main teleconnections. The impact of the main atmospheric teleconnections on the surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) of the Antarctic <span class="hlt">ice</span> sheet (AIS) in the past has been seldom investigated. The ANDRILL marine record have shown that at the end of the Pliocene, the <span class="hlt">ice</span> sheet expanded in the Ross Sea concomitantly with the expansion of the sea <span class="hlt">ice</span> cover. This would have enhanced the formation of bottom waters that in turn, would have fostered upwelling along the West African coast and along the coast of Peru. The impact of Antarctica on the tropical climate dynamics has been shown by previous studies. To close the loop, this work investigates the impact of the tropical and high-latitude SST cooling on the main atmospheric teleconnections and then on the Antarctic SMB through the Plio/Pleistocene transition. Idealized Atmospheric General Circulation Model simulations are performed, in which high-latitude and tropical SST cooling are prescribed starting from the Pliocene SST. The atmospheric conditions obtained are then used to force an <span class="hlt">ice</span> sheet model and a stand-alone energy <span class="hlt">balance</span> model to investigate the impact on the SMB of the two main atmospheric teleconnections active in the Southern Hemisphere, namely the Southern Annular Mode (SAM) and the Pacific-South-American oscillation (PSA. In agreement with ANDRILL marine records, results show that the Easterlies strengthen along the Antarctic coasts during the Plio/Pleistocene transition. This, however, occurs only after cooling the tropical SSTs in the AGCM simulations. More importantly, the cooling of the tropical SST, through the strengthening of the PSA, has the largest influence on the spatial distribution of the climatic anomalies over Antarctica. This explains most of the SMB patterns simulated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.G31C0931W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.G31C0931W"><span>Temporal and spatial variabilities of Antarctic <span class="hlt">ice</span> <span class="hlt">mass</span> changes inferred by GRACE in a Bayesian framework</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, L.; Davis, J. L.; Tamisiea, M. E.</p> <p>2017-12-01</p> <p>The Antarctic <span class="hlt">ice</span> sheet (AIS) holds about 60% of all fresh water on the Earth, an amount equivalent to about 58 m of sea-level rise. Observation of AIS <span class="hlt">mass</span> change is thus essential in determining and predicting its contribution to sea level. While the <span class="hlt">ice</span> <span class="hlt">mass</span> loss estimates for West Antarctica (WA) and the Antarctic Peninsula (AP) are in good agreement, what the <span class="hlt">mass</span> <span class="hlt">balance</span> over East Antarctica (EA) is, and whether or not it compensates for the <span class="hlt">mass</span> loss is under debate. Besides the different error sources and sensitivities of different measurement types, complex spatial and temporal variabilities would be another factor complicating the accurate estimation of the AIS <span class="hlt">mass</span> <span class="hlt">balance</span>. Therefore, a model that allows for variabilities in both melting rate and seasonal signals would seem appropriate in the estimation of present-day AIS melting. We present a stochastic filter technique, which enables the Bayesian separation of the systematic stripe noise and <span class="hlt">mass</span> signal in decade-length GRACE monthly gravity series, and allows the estimation of time-variable seasonal and inter-annual components in the signals. One of the primary advantages of this Bayesian method is that it yields statistically rigorous uncertainty estimates reflecting the inherent spatial resolution of the data. By applying the stochastic filter to the decade-long GRACE observations, we present the temporal variabilities of the AIS <span class="hlt">mass</span> <span class="hlt">balance</span> at basin scale, particularly over East Antarctica, and decipher the EA <span class="hlt">mass</span> variations in the past decade, and their role in affecting overall AIS <span class="hlt">mass</span> <span class="hlt">balance</span> and sea level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatGe...8..534U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatGe...8..534U"><span>Laurentide <span class="hlt">ice</span>-sheet instability during the last deglaciation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ullman, David J.; Carlson, Anders E.; Anslow, Faron S.; Legrande, Allegra N.; Licciardi, Joseph M.</p> <p>2015-07-01</p> <p>Changes in the amount of summer incoming solar radiation (insolation) reaching the Northern Hemisphere are the underlying pacemaker of glacial cycles. However, not all rises in boreal summer insolation over the past 800,000 years resulted in deglaciation to present-day <span class="hlt">ice</span> volumes, suggesting that there may be a climatic threshold for the disappearance of land-based <span class="hlt">ice</span>. Here we assess the surface <span class="hlt">mass</span> <span class="hlt">balance</span> stability of the Laurentide <span class="hlt">ice</span> sheet--the largest glacial <span class="hlt">ice</span> <span class="hlt">mass</span> in the Northern Hemisphere--during the last deglaciation (24,000 to 9,000 years ago). We run a surface energy <span class="hlt">balance</span> model with climate data from simulations with a fully coupled atmosphere-ocean general circulation model for key time slices during the last deglaciation. We find that the surface <span class="hlt">mass</span> <span class="hlt">balance</span> of the Laurentide <span class="hlt">ice</span> sheet was positive throughout much of the deglaciation, and suggest that dynamic discharge was mainly responsible for <span class="hlt">mass</span> loss during this time. Total surface <span class="hlt">mass</span> <span class="hlt">balance</span> became negative only in the early Holocene, indicating the transition to a new state where <span class="hlt">ice</span> loss occurred primarily by surface ablation. We conclude that the Laurentide <span class="hlt">ice</span> sheet remained a viable <span class="hlt">ice</span> sheet before the Holocene and began to fully deglaciate only once summer temperatures and radiative forcing over the <span class="hlt">ice</span> sheet increased by 6-7 °C and 16-20 W m-2, respectively, relative to full glacial conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.water.usgs.gov/wri034095/','USGSPUBS'); return false;" href="http://pubs.water.usgs.gov/wri034095/"><span><span class="hlt">Mass</span> <span class="hlt">balance</span>, meteorology, area altitude distribution, glacier-surface altitude, <span class="hlt">ice</span> motion, terminus position, and runoff at Gulkana Glacier, Alaska, 1996 <span class="hlt">balance</span> year</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>March, Rod S.</p> <p>2003-01-01</p> <p>The 1996 measured winter snow, maximum winter snow, net, and annual <span class="hlt">balances</span> in the Gulkana Glacier Basin were evaluated on the basis of meteorological, hydrological, and glaciological data. Averaged over the glacier, the measured winter snow <span class="hlt">balance</span> was 0.87 meter on April 18, 1996, 1.1 standard deviation below the long-term average; the maximum winter snow <span class="hlt">balance</span>, 1.06 meters, was reached on May 28, 1996; and the net <span class="hlt">balance</span> (from August 30, 1995, to August 24, 1996) was -0.53 meter, 0.53 standard deviation below the long-term average. The annual <span class="hlt">balance</span> (October 1, 1995, to September 30, 1996) was -0.37 meter. Area-averaged <span class="hlt">balances</span> were reported using both the 1967 and 1993 area altitude distributions (the numbers previously given in this abstract use the 1993 area altitude distribution). Net <span class="hlt">balance</span> was about 25 percent less negative using the 1993 area altitude distribution than the 1967 distribution. Annual average air temperature was 0.9 degree Celsius warmer than that recorded with the analog sensor used since 1966. Total precipitation catch for the year was 0.78 meter, 0.8 standard deviations below normal. The annual average wind speed was 3.5 meters per second in the first year of measuring wind speed. Annual runoff averaged 1.50 meters over the basin, 1.0 standard deviation below the long-term average. Glacier-surface altitude and <span class="hlt">ice</span>-motion changes measured at three index sites document seasonal <span class="hlt">ice</span>-speed and glacier-thickness changes. Both showed a continuation of a slowing and thinning trend present in the 1990s. The glacier terminus and lower ablation area were defined for 1996 with a handheld Global Positioning System survey of 126 locations spread out over about 4 kilometers on the lower glacier margin. From 1949 to 1996, the terminus retreated about 1,650 meters for an average retreat rate of 35 meters per year.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.U44A..01A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.U44A..01A"><span>Recent Changes in Arctic Glaciers, <span class="hlt">Ice</span> Caps, and the Greenland <span class="hlt">Ice</span> Sheet: Cold Facts About Warm <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abdalati, W.</p> <p>2005-12-01</p> <p>One of the major manifestations of Arctic change can be observed in the state of <span class="hlt">balance</span> of Arctic glaciers and <span class="hlt">ice</span> caps and the Greenland <span class="hlt">ice</span> sheet. These <span class="hlt">ice</span> <span class="hlt">masses</span> are estimated to contain nearly 3 million cubic kilometers of <span class="hlt">ice</span>, which is more than six times greater than all the water stored in the Earth's lakes, rivers, and snow combined and is the equivalent of over 7 meters of sea level. Most of these <span class="hlt">ice</span> <span class="hlt">masses</span> have been shrinking in recent in years, but their <span class="hlt">mass</span> <span class="hlt">balance</span> is highly variable on a wide range of spatial and temporal scales. On the Greenland <span class="hlt">ice</span> sheet most of the coastal regions have thinned substantially as melt has increased and some of its outlet glaciers have accelerated. Near the equilibrium line in West Greenland, we have seen evidence of summer acceleration that is linked to surface meltwater production, suggesting a relatively rapid response mechanism of the <span class="hlt">ice</span> sheet change to a warming climate. At the same time, however, the vast interior regions of the Greenland <span class="hlt">ice</span> sheet have shown little change or slight growth, as accumulation in these areas may have increased. Throughout much of the rest of the Arctic, many glaciers and <span class="hlt">ice</span> caps have been shrinking in the past few decades, and in Canada and Alaska, the rate of <span class="hlt">ice</span> loss seems to have accelerated during the late 1990s. These recent observations offer only a snapshot in time of the long-term behavior, but they are providing crucial information about the current state of <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> and the mechanisms that control it in one of the most climatically sensitive regions on Earth. As we continue to learn more through a combination of remote sensing observations, in situ measurements and improved modeling capabilities, it is important that we coordinate and integrate these approaches effectively in order to predict future changes and their impact on sea level, freshwater discharge, and ocean circulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.430..427R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.430..427R"><span>Modelling the feedbacks between <span class="hlt">mass</span> <span class="hlt">balance</span>, <span class="hlt">ice</span> flow and debris transport to predict the response to climate change of debris-covered glaciers in the Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rowan, Ann V.; Egholm, David L.; Quincey, Duncan J.; Glasser, Neil F.</p> <p>2015-11-01</p> <p>Many Himalayan glaciers are characterised in their lower reaches by a rock debris layer. This debris insulates the glacier surface from atmospheric warming and complicates the response to climate change compared to glaciers with clean-<span class="hlt">ice</span> surfaces. Debris-covered glaciers can persist well below the altitude that would be sustainable for clean-<span class="hlt">ice</span> glaciers, resulting in much longer timescales of <span class="hlt">mass</span> loss and meltwater production. The properties and evolution of supraglacial debris present a considerable challenge to understanding future glacier change. Existing approaches to predicting variations in glacier volume and meltwater production rely on numerical models that represent the processes governing glaciers with clean-<span class="hlt">ice</span> surfaces, and yield conflicting results. We developed a numerical model that couples the flow of <span class="hlt">ice</span> and debris and includes important feedbacks between debris accumulation and glacier <span class="hlt">mass</span> <span class="hlt">balance</span>. To investigate the impact of debris transport on the response of a glacier to recent and future climate change, we applied this model to a large debris-covered Himalayan glacier-Khumbu Glacier in Nepal. Our results demonstrate that supraglacial debris prolongs the response of the glacier to warming and causes lowering of the glacier surface in situ, concealing the magnitude of <span class="hlt">mass</span> loss when compared with estimates based on glacierised area. Since the Little <span class="hlt">Ice</span> Age, Khumbu Glacier has lost 34% of its volume while its area has reduced by only 6%. We predict a decrease in glacier volume of 8-10% by AD2100, accompanied by dynamic and physical detachment of the debris-covered tongue from the active glacier within the next 150 yr. This detachment will accelerate rates of glacier decay, and similar changes are likely for other debris-covered glaciers in the Himalaya.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/sir/2005/5210/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/sir/2005/5210/"><span>Water, <span class="hlt">ice</span>, and meteorological measurements at South Cascade glacier, Washington, <span class="hlt">balance</span> year 2003</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bidlake, William R.; Josberger, Edward G.; Savoca, Mark E.</p> <p>2005-01-01</p> <p>Winter snow accumulation and summer snow and <span class="hlt">ice</span> ablation were measured at South Cascade Glacier, Washington, to estimate glacier <span class="hlt">mass-balance</span> quantities for <span class="hlt">balance</span> year 2003. The 2003 glacier-average maximum winter snow <span class="hlt">balance</span> was 2.66 meters water equivalent, which was about equal to the average of such <span class="hlt">balances</span> for the glacier since <span class="hlt">balance</span> year 1959. The 2003 glacier summer <span class="hlt">balance</span> (-4.76 meters water equivalent) was the most negative reported for the glacier, and the 2003 net <span class="hlt">balance</span> (-2.10 meters water equivalent), was the second-most negative reported. The glacier 2003 annual (water year) <span class="hlt">balance</span> was -1.89 meters water equivalent. The area of the glacier near the end of the <span class="hlt">balance</span> year was 1.89 square kilometers, a decrease of 0.03 square kilometer from the previous year. The equilibrium-line altitude was higher than any part of the glacier; however, because snow remained along part of one side of the upper glacier, the accumulation-area ratio was 0.07. During September 13, 2002-September 13, 2003, the glacier terminus retreated at a rate of about 15 meters per year. Average speed of surface <span class="hlt">ice</span>, computed using a series of vertical aerial photographs dating back to 2001, ranged from 2.2 to 21.8 meters per year. Runoff from the subbasin containing the glacier and from an adjacent non-glacierized basin was gaged during part of water year 2003. Air temperature, precipitation, atmospheric water-vapor pressure, wind speed, and incoming solar radiation were measured at selected locations on and near the glacier. Summer 2003 at the glacier was among the warmest for which data are available.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16782607','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16782607"><span><span class="hlt">Ice</span>-sheet contributions to future sea-level change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gregory, J M; Huybrechts, P</p> <p>2006-07-15</p> <p>Accurate simulation of <span class="hlt">ice</span>-sheet surface <span class="hlt">mass</span> <span class="hlt">balance</span> requires higher spatial resolution than is afforded by typical atmosphere-ocean general circulation models (AOGCMs), owing, in particular, to the need to resolve the narrow and steep margins where the majority of precipitation and ablation occurs. We have developed a method for calculating <span class="hlt">mass-balance</span> changes by combining <span class="hlt">ice</span>-sheet average time-series from AOGCM projections for future centuries, both with information from high-resolution climate models run for short periods and with a 20km <span class="hlt">ice</span>-sheet <span class="hlt">mass-balance</span> model. Antarctica contributes negatively to sea level on account of increased accumulation, while Greenland contributes positively because ablation increases more rapidly. The uncertainty in the results is about 20% for Antarctica and 35% for Greenland. Changes in <span class="hlt">ice</span>-sheet topography and dynamics are not included, but we discuss their possible effects. For an annual- and area-average warming exceeding 4.5+/-0.9K in Greenland and 3.1+/-0.8K in the global average, the net surface <span class="hlt">mass</span> <span class="hlt">balance</span> of the Greenland <span class="hlt">ice</span> sheet becomes negative, in which case it is likely that the <span class="hlt">ice</span> sheet would eventually be eliminated, raising global-average sea level by 7m.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12368852','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12368852"><span>Switch of flow direction in an Antarctic <span class="hlt">ice</span> stream.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Conway, H; Catania, G; Raymond, C F; Gades, A M; Scambos, T A; Engelhardt, H</p> <p>2002-10-03</p> <p>Fast-flowing <span class="hlt">ice</span> streams transport <span class="hlt">ice</span> from the interior of West Antarctica to the ocean, and fluctuations in their activity control the <span class="hlt">mass</span> <span class="hlt">balance</span> of the <span class="hlt">ice</span> sheet. The <span class="hlt">mass</span> <span class="hlt">balance</span> of the Ross Sea sector of the West Antarctic <span class="hlt">ice</span> sheet is now positive--that is, it is growing--mainly because one of the <span class="hlt">ice</span> streams (<span class="hlt">ice</span> stream C) slowed down about 150 years ago. Here we present evidence from both surface measurements and remote sensing that demonstrates the highly dynamic nature of the Ross drainage system. We show that the flow in an area that once discharged into <span class="hlt">ice</span> stream C has changed direction, now draining into the Whillans <span class="hlt">ice</span> stream (formerly <span class="hlt">ice</span> stream B). This switch in flow direction is a result of continuing thinning of the Whillans <span class="hlt">ice</span> stream and recent thickening of <span class="hlt">ice</span> stream C. Further abrupt reorganization of the activity and configuration of the <span class="hlt">ice</span> streams over short timescales is to be expected in the future as the surface topography of the <span class="hlt">ice</span> sheet responds to the combined effects of internal dynamics and long-term climate change. We suggest that caution is needed when using observations of short-term <span class="hlt">mass</span> changes to draw conclusions about the large-scale <span class="hlt">mass</span> <span class="hlt">balance</span> of the <span class="hlt">ice</span> sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016WRR....52.3888B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016WRR....52.3888B"><span>High-resolution modeling of coastal freshwater discharge and glacier <span class="hlt">mass</span> <span class="hlt">balance</span> in the Gulf of Alaska watershed</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beamer, J. P.; Hill, D. F.; Arendt, A.; Liston, G. E.</p> <p>2016-05-01</p> <p>A comprehensive study of the Gulf of Alaska (GOA) drainage basin was carried out to improve understanding of the coastal freshwater discharge (FWD) and glacier volume loss (GVL). Hydrologic processes during the period 1980-2014 were modeled using a suite of physically based, spatially distributed weather, energy-<span class="hlt">balance</span> snow/<span class="hlt">ice</span> melt, soil water <span class="hlt">balance</span>, and runoff routing models at a high-resolution (1 km horizontal grid; daily time step). Meteorological forcing was provided by the North American Regional Reanalysis (NARR), Modern Era Retrospective Analysis for Research and Applications (MERRA), and Climate Forecast System Reanalysis (CFSR) data sets. Streamflow and glacier <span class="hlt">mass</span> <span class="hlt">balance</span> modeled using MERRA and CFSR compared well with observations in four watersheds used for calibration in the study domain. However, only CFSR produced regional seasonal and long-term trends in water <span class="hlt">balance</span> that compared favorably with independent Gravity Recovery and Climate Experiment (GRACE) and airborne altimetry data. Mean annual runoff using CFSR was 760 km3 yr-1, 8% of which was derived from the long-term removal of stored water from glaciers (glacier volume loss). The annual runoff from CFSR was partitioned into 63% snowmelt, 17% glacier <span class="hlt">ice</span> melt, and 20% rainfall. Glacier runoff, taken as the sum of rainfall, snow, and <span class="hlt">ice</span> melt occurring each season on glacier surfaces, was 38% of the total seasonal runoff, with the remaining runoff sourced from nonglacier surfaces. Our simulations suggests that existing GRACE solutions, previously reported to represent glacier <span class="hlt">mass</span> <span class="hlt">balance</span> alone, are actually measuring the full water budget of land and <span class="hlt">ice</span> surfaces.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C54A..03L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C54A..03L"><span>Inferring unknow boundary conditions of the Greenland <span class="hlt">Ice</span> Sheet by assimilating ICESat-1 and <span class="hlt">Ice</span>Bridge altimetry intothe <span class="hlt">Ice</span> Sheet System Model.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Larour, E. Y.; Khazendar, A.; Seroussi, H. L.; Schlegel, N.; Csatho, B. M.; Schenk, A. F.; Rignot, E. J.; Morlighem, M.</p> <p>2014-12-01</p> <p>Altimetry signals from missions such as ICESat-1, CryoSat, EnviSat, as well as altimeters onboard Operation <span class="hlt">Ice</span>Bridge provide vital insights into processes such as surface <span class="hlt">mass</span> <span class="hlt">balance</span>, <span class="hlt">mass</span> transport and <span class="hlt">ice</span>-flow dynamics. Historically however, <span class="hlt">ice</span>-flow models have been focused on assimilating surface velocities from satellite-based radar observations, to infer properties such as basal friction or the position of the bedrock. Here, we leverage a new methodology based on automatic differentation of the <span class="hlt">Ice</span> Sheet System Model to assimilate surface altimetry data into a reconstruction of the past decade of <span class="hlt">ice</span> flow on the North Greenland area. We infer corrections to boundary conditions such as basal friction and surface <span class="hlt">mass</span> <span class="hlt">balance</span>, as well as corrections to the <span class="hlt">ice</span> hardness, to best-match the observed altimetry record. We compare these corrections between glaciers such as Petermann Glacier, 79 North and Zacchariae Isstrom. The altimetry signals exhibit very different patterns between East and West, which translate into very different signatures for the inverted boundary conditions. This study gives us greater insights into what differentiates different basins, both in terms of <span class="hlt">mass</span> transport and <span class="hlt">ice</span>-flow dynamics, and what could bethe controlling mechanisms behind the very different evolutions of these basins.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.C33C1305B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.C33C1305B"><span>Climate during the Last Glacial Maximum in the Wasatch Mountains Inferred from Glacier <span class="hlt">Mass-Balance</span> and <span class="hlt">Ice</span>-Flow Modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bash, E. A.; Laabs, B. J.</p> <p>2006-12-01</p> <p>The Wasatch Mountains of northern Utah contained numerous valley glaciers east and immediately downwind of Lake Bonneville during the Last Glacial Maximum (LGM). While the extent and chronology of glaciation in the Wasatch Mountains and the rise and fall of Lake Bonneville are becoming increasingly well understood, inferences of climatic conditions during the LGM for this area and elsewhere in the Rocky Mountains and northern Great Basin have yielded a wide range of temperature depression estimates. For example, previous estimates of temperature depression based on glacier and lake reconstructions in this region generally range from 7° to 9° C colder than modern. Glacier modeling studies for Little Cottonwood Canyon (northern Wasatch Mountains) suggest that such temperature depressions would have been accompanied by precipitation increases of about 3 to 1x modern, respectively (McCoy and Williams, 1985; Laabs et al., 2006). However, interpretations of other proxies suggest that temperature depression in this area may have been significantly greater, up to 13° C (e.g., Kaufman 2003), which would likely have been accompanied by less precipitation than modern. To address this issue, we reconstructed <span class="hlt">ice</span> extent in the American Fork Canyon of the Wasatch Mountains and applied glacier modeling methods of Plummer and Phillips (2003) to infer climatic conditions during the LGM. Field mapping indicates that glaciers occupied an area of more than 20 km2 in the canyon and reached maximum lengths of about 9 km. To link <span class="hlt">ice</span> extent to climatic changes, a physically based, two- dimensional numerical model of glacier <span class="hlt">mass</span> <span class="hlt">balance</span> and <span class="hlt">ice</span> flow was applied to these valleys. The modeling approach allows the combined effects of temperature, precipitation and solar radiation on net <span class="hlt">mass</span> <span class="hlt">balance</span> of a drainage basin to be explored. Results of model experiments indicate that a temperature depression of less than 9° C in the American Fork Canyon would have been accompanied by greater</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://wa.water.usgs.gov/projects/glacier/data/bidlake_AGU_2010.pdf','USGSPUBS'); return false;" href="http://wa.water.usgs.gov/projects/glacier/data/bidlake_AGU_2010.pdf"><span>Glacier modeling in support of field observations of <span class="hlt">mass</span> <span class="hlt">balance</span> at South Cascade Glacier, Washington, USA</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Josberger, Edward G.; Bidlake, William R.</p> <p>2010-01-01</p> <p>The long-term USGS measurement and reporting of <span class="hlt">mass</span> <span class="hlt">balance</span> at South Cascade Glacier was assisted in <span class="hlt">balance</span> years 2006 and 2007 by a new <span class="hlt">mass</span> <span class="hlt">balance</span> model. The model incorporates a temperature-index melt computation and accumulation is modeled from glacier air temperature and gaged precipitation at a remote site. <span class="hlt">Mass</span> <span class="hlt">balance</span> modeling was used with glaciological measurements to estimate dates and magnitudes of critical <span class="hlt">mass</span> <span class="hlt">balance</span> phenomena. In support of the modeling, a detailed analysis was made of the "glacier cooling effect" that reduces summer air temperature near the <span class="hlt">ice</span> surface as compared to that predicted on the basis of a spatially uniform temperature lapse rate. The analysis was based on several years of data from measurements of near-surface air temperature on the glacier. The 2006 and 2007 winter <span class="hlt">balances</span> of South Cascade Glacier, computed with this new, model-augmented methodology, were 2.61 and 3.41 mWE, respectively. The 2006 and 2007 summer <span class="hlt">balances</span> were -4.20 and -3.63 mWE, respectively, and the 2006 and 2007 net <span class="hlt">balances</span> were -1.59 and -0.22 mWE. PDF version of a presentation on the <span class="hlt">mass</span> <span class="hlt">balance</span> of South Cascade Glacier in Washington state. Presented at the American Geophysical Union Fall Meeting 2010.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060026203&hterms=sauber&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsauber','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060026203&hterms=sauber&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsauber"><span><span class="hlt">Ice</span> <span class="hlt">Mass</span> Fluctuations and Earthquake Hazard</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sauber, J.</p> <p>2006-01-01</p> <p>In south central Alaska, tectonic strain rates are high in a region that includes large glaciers undergoing <span class="hlt">ice</span> wastage over the last 100-150 years [Sauber et al., 2000; Sauber and Molnia, 2004]. In this study we focus on the region referred to as the Yakataga segment of the Pacific-North American plate boundary zone in Alaska. In this region, the Bering and Malaspina glacier ablation zones have average <span class="hlt">ice</span> elevation decreases from 1-3 meters/year (see summary and references in Molnia, 2005). The elastic response of the solid Earth to this <span class="hlt">ice</span> <span class="hlt">mass</span> decrease alone would cause several mm/yr of horizontal motion and uplift rates of up to 10-12 mm/yr. In this same region observed horizontal rates of tectonic deformation range from 10 to 40 mm/yr to the north-northwest and the predicted tectonic uplift rates range from -2 mm/year near the Gulf of Alaska coast to 12mm/year further inland [Savage and Lisowski, 1988; Ma et al, 1990; Sauber et al., 1997, 2000, 2004; Elliot et al., 2005]. The large <span class="hlt">ice</span> <span class="hlt">mass</span> changes associated with glacial wastage and surges perturb the tectonic rate of deformation at a variety of temporal and spatial scales. The associated incremental stress change may enhance or inhibit earthquake occurrence. We report recent (seasonal to decadal) <span class="hlt">ice</span> elevation changes derived from data from NASA's ICESat satellite laser altimeter combined with earlier DEM's as a reference surface to illustrate the characteristics of short-term <span class="hlt">ice</span> elevation changes [Sauber et al., 2005, Muskett et al., 2005]. Since we are interested in evaluating the effect of <span class="hlt">ice</span> changes on faulting potential, we calculated the predicted surface displacement changes and incremental stresses over a specified time interval and calculated the change in the fault stability margin using the approach given by Wu and Hasegawa [1996]. Additionally, we explored the possibility that these <span class="hlt">ice</span> <span class="hlt">mass</span> fluctuations altered the seismic rate of background seismicity. Although we primarily focus on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.7942P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.7942P"><span>Sea level rise from the Greenland <span class="hlt">Ice</span> Sheet during the Eemian interglacial: Review of previous work with focus on the surface <span class="hlt">mass</span> <span class="hlt">balance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Plach, Andreas; Hestnes Nisancioglu, Kerim</p> <p>2016-04-01</p> <p>The contribution from the Greenland <span class="hlt">Ice</span> Sheet (GIS) to the global sea level rise during the Eemian interglacial (about 125,000 year ago) was the focus of many studies in the past. A main reason for the interest in this period is the considerable warmer climate during the Eemian which is often seen as an equivalent for possible future climate conditions. Simulated sea level rise during the Eemian can therefore be used to better understand a possible future sea level rise. The most recent assessment report of the Intergovernmental Panel on Climate Change (IPCC AR5) gives an overview of several studies and discusses the possible implications for a future sea level rise. The report also reveals the big differences between these studies in terms of simulated GIS extent and corresponding sea level rise. The present study gives a more exhaustive review of previous work discussing sea level rise from the GIS during the Eemian interglacial. The smallest extents of the GIS simulated by various authors are shown and summarized. A focus is thereby given to the methods used to calculate the surface <span class="hlt">mass</span> <span class="hlt">balance</span>. A hypothesis of the present work is that the varying results of the previous studies can largely be explained due to the various methods used to calculate the surface <span class="hlt">mass</span> <span class="hlt">balance</span>. In addition, as a first step for future work, the surface <span class="hlt">mass</span> <span class="hlt">balance</span> of the GIS for a proxy-data derived forcing ("index method") and a direct forcing with a General Circulation Model (GCM) are shown and discussed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/sir/2007/5055/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/sir/2007/5055/"><span>Water, <span class="hlt">Ice</span>, and Meteorological Measurements at South Cascade Glacier, Washington, <span class="hlt">Balance</span> Years 2004 and 2005</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bidlake, William R.; Josberger, Edward G.; Savoca, Mark E.</p> <p>2007-01-01</p> <p>Winter snow accumulation and summer snow and <span class="hlt">ice</span> ablation were measured at South Cascade Glacier, Washington, to estimate glacier <span class="hlt">mass-balance</span> quantities for <span class="hlt">balance</span> years 2004 and 2005. The North Cascade Range in the vicinity of South Cascade Glacier accumulated smaller than normal winter snowpacks during water years 2004 and 2005. Correspondingly, the <span class="hlt">balance</span> years 2004 and 2005 maximum winter snow <span class="hlt">balances</span> of South Cascade Glacier, 2.08 and 1.97 meters water equivalent, respectively, were smaller than the average of such <span class="hlt">balances</span> since 1959. The 2004 glacier summer <span class="hlt">balance</span> (-3.73 meters water equivalent) was the eleventh most negative during 1959 to 2005 and the 2005 glacier summer <span class="hlt">balance</span> (-4.42 meters water equivalent) was the third most negative. The relatively small winter snow <span class="hlt">balances</span> and unusually negative summer <span class="hlt">balances</span> of 2004 and 2005 led to an overall loss of glacier <span class="hlt">mass</span>. The 2004 and 2005 glacier net <span class="hlt">balances</span>, -1.65 and -2.45 meters water equivalent, respectively, were the seventh and second most negative during 1953 to 2005. For both <span class="hlt">balance</span> years, the accumulation area ratio was less than 0.05 and the equilibrium line altitude was higher than the glacier. The unusually negative 2004 and 2005 glacier net <span class="hlt">balances</span>, combined with a negative <span class="hlt">balance</span> previously reported for 2003, resulted in a cumulative 3-year net <span class="hlt">balance</span> of -6.20 meters water equivalent. No equal or greater 3-year <span class="hlt">mass</span> loss has occurred previously during the more than 4 decades of U.S. Geological Survey <span class="hlt">mass-balance</span> measurements at South Cascade Glacier. Accompanying the glacier <span class="hlt">mass</span> losses were retreat of the terminus and reduction of total glacier area. The terminus retreated at a rate of about 17 meters per year during <span class="hlt">balance</span> year 2004 and 15 meters per year during <span class="hlt">balance</span> year 2005. Glacier area near the end of <span class="hlt">balance</span> years 2004 and 2005 was 1.82 and 1.75 square kilometers, respectively. Runoff from the basin containing the glacier and from an adjacent nonglacierized basin was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C44A..02B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C44A..02B"><span>connecting the dots between Greenland <span class="hlt">ice</span> sheet surface melting and <span class="hlt">ice</span> flow dynamics (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Box, J. E.; Colgan, W. T.; Fettweis, X.; Phillips, T. P.; Stober, M.</p> <p>2013-12-01</p> <p>This presentation is of a 'unified theory' in glaciology that first identifies surface albedo as a key factor explaining total <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> and then surveys a mechanistic self-reinforcing interaction between melt water and <span class="hlt">ice</span> flow dynamics. The theory is applied in a near-real time total Greenland <span class="hlt">mass</span> <span class="hlt">balance</span> retrieval based on surface albedo, a powerful integrator of the competing effects of accumulation and ablation. New snowfall reduces sunlight absorption and increases meltwater retention. Melting amplifies absorbed sunlight through thermal metamorphism and bare <span class="hlt">ice</span> expansion in space and time. By ';following the melt'; we reveal mechanisms linking existing science into a unified theory. Increasing meltwater softens the <span class="hlt">ice</span> sheet in three ways: 1.) sensible heating given the water temperature exceeds that of the <span class="hlt">ice</span> sheet interior; 2.) Some infiltrating water refreezes, transferring latent heat to the <span class="hlt">ice</span>; 3.) Friction from water turbulence heats the <span class="hlt">ice</span>. It has been shown that for a point on the <span class="hlt">ice</span> sheet, basal lubrication increases <span class="hlt">ice</span> flow speed to a time when an efficient sub-glacial drainage network develops that reduces this effect. Yet, with an increasing melt duration the point where the <span class="hlt">ice</span> sheet glides on a wet bed increases inland to a larger area. This effect draws down the <span class="hlt">ice</span> surface elevation, contributing to the ';elevation feedback'. In a perpetual warming scenario, the elevation feedback ultimately leads to <span class="hlt">ice</span> sheet loss reversible only through much slower <span class="hlt">ice</span> sheet growth in an <span class="hlt">ice</span> age environment. As the inland <span class="hlt">ice</span> sheet accelerates, the horizontal extension pulls cracks and crevasses open, trapping more sunlight, amplifying the effect of melt accelerated <span class="hlt">ice</span>. As the bare <span class="hlt">ice</span> area increases, the direct sun-exposed crevassed and infiltration area increases further allowing the <span class="hlt">ice</span> warming process to occur more broadly. Considering hydrofracture [a.k.a. hydrofracking]; surface meltwater fills cracks, attacking the <span class="hlt">ice</span> integrity</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA572179','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA572179"><span><span class="hlt">Mass</span> <span class="hlt">Balance</span> of Multiyear Sea <span class="hlt">Ice</span> in the Southern Beaufort Sea</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2012-09-30</p> <p>datasets. Table 1 lists the primary data sources to be used. To determine sources and sinks of MY <span class="hlt">ice</span>, we use a simple model of MY <span class="hlt">ice</span> circulation, which is...shown in Figure 1. In this model , we consider the Beaufort Sea to consist of four zones defined by mean drift of sea <span class="hlt">ice</span> in summer and winter, such...Healy/Louis S. St. Laurant cruises 1 Seasonal <span class="hlt">Ice</span> Zone Observing Network 2 Polar Airborne Measurements and Arctic Regional Climate Model</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.4564V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.4564V"><span>GIA models with composite rheology and 3D viscosity: effect on GRACE <span class="hlt">mass</span> <span class="hlt">balance</span> in Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van der Wal, Wouter; Whitehouse, Pippa; Schrama, Ernst</p> <p>2014-05-01</p> <p>Most Glacial Isostatic Adjustment (GIA) models that have been used to correct GRACE data for the influence of GIA assume a radial stratification of viscosity in the Earth's mantle (1D viscosity). Seismic data in Antarctica indicate that there are large viscosity variations in the horizontal direction (3D viscosity). The purpose of this research is to determine the effect of 3D viscosity on GIA model output, and hence <span class="hlt">mass</span> <span class="hlt">balance</span> estimates in Antarctica. We use a GIA model with 3D viscosity and composite rheology in combination with <span class="hlt">ice</span> loading histories <span class="hlt">ICE</span>-5G and W12a. From comparisons with uplift and sea-level data in Fennoscandia and North America three preferred viscosity models are selected. For two of the 3D viscosity models the maximum gravity rate due to <span class="hlt">ICE</span>-5G forcing is located over the Ronne-Filchner <span class="hlt">ice</span> shelf. This is in contrast with the results obtained using a 1D model, in which the maximum gravity rate due to <span class="hlt">ICE</span>-5G forcing is always located over the Ross <span class="hlt">ice</span> shelf. This demonstrates that not all 3D viscosity models can be approximated with a 1D viscosity model. Using CSR release 5 GRACE data from February 2003 to June 2013 <span class="hlt">mass</span> <span class="hlt">balance</span> estimates for the three preferred viscosity models are -131 to -171 Gt/year for the <span class="hlt">ICE</span>-5G model, and -48 to -57 Gt/year for the W12a model. The range due to Earth model uncertainty is larger than the error bar for GRACE (10 Gt/year), but smaller than the range resulting from the difference in <span class="hlt">ice</span> loading histories.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24037377','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24037377"><span>Calving fluxes and basal melt rates of Antarctic <span class="hlt">ice</span> shelves.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Depoorter, M A; Bamber, J L; Griggs, J A; Lenaerts, J T M; Ligtenberg, S R M; van den Broeke, M R; Moholdt, G</p> <p>2013-10-03</p> <p>Iceberg calving has been assumed to be the dominant cause of <span class="hlt">mass</span> loss for the Antarctic <span class="hlt">ice</span> sheet, with previous estimates of the calving flux exceeding 2,000 gigatonnes per year. More recently, the importance of melting by the ocean has been demonstrated close to the grounding line and near the calving front. So far, however, no study has reliably quantified the calving flux and the basal <span class="hlt">mass</span> <span class="hlt">balance</span> (the <span class="hlt">balance</span> between accretion and ablation at the <span class="hlt">ice</span>-shelf base) for the whole of Antarctica. The distribution of fresh water in the Southern Ocean and its partitioning between the liquid and solid phases is therefore poorly constrained. Here we estimate the <span class="hlt">mass</span> <span class="hlt">balance</span> components for all <span class="hlt">ice</span> shelves in Antarctica, using satellite measurements of calving flux and grounding-line flux, modelled <span class="hlt">ice</span>-shelf snow accumulation rates and a regional scaling that accounts for unsurveyed areas. We obtain a total calving flux of 1,321 ± 144 gigatonnes per year and a total basal <span class="hlt">mass</span> <span class="hlt">balance</span> of -1,454 ± 174 gigatonnes per year. This means that about half of the <span class="hlt">ice</span>-sheet surface <span class="hlt">mass</span> gain is lost through oceanic erosion before reaching the <span class="hlt">ice</span> front, and the calving flux is about 34 per cent less than previous estimates derived from iceberg tracking. In addition, the fraction of <span class="hlt">mass</span> loss due to basal processes varies from about 10 to 90 per cent between <span class="hlt">ice</span> shelves. We find a significant positive correlation between basal <span class="hlt">mass</span> loss and surface elevation change for <span class="hlt">ice</span> shelves experiencing surface lowering and enhanced discharge. We suggest that basal <span class="hlt">mass</span> loss is a valuable metric for predicting future <span class="hlt">ice</span>-shelf vulnerability to oceanic forcing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.4086A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.4086A"><span>Variable Basal Melt Rates of Antarctic Peninsula <span class="hlt">Ice</span> Shelves, 1994-2016</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adusumilli, Susheel; Fricker, Helen Amanda; Siegfried, Matthew R.; Padman, Laurie; Paolo, Fernando S.; Ligtenberg, Stefan R. M.</p> <p>2018-05-01</p> <p>We have constructed 23-year (1994-2016) time series of Antarctic Peninsula (AP) <span class="hlt">ice</span>-shelf height change using data from four satellite radar altimeters (ERS-1, ERS-2, Envisat, and CryoSat-2). Combining these time series with output from atmospheric and firn models, we partitioned the total height-change signal into contributions from varying surface <span class="hlt">mass</span> <span class="hlt">balance</span>, firn state, <span class="hlt">ice</span> dynamics, and basal <span class="hlt">mass</span> <span class="hlt">balance</span>. On the Bellingshausen coast of the AP, <span class="hlt">ice</span> shelves lost 84 ± 34 Gt a-1 to basal melting, compared to contributions of 50 ± 7 Gt a-1 from surface <span class="hlt">mass</span> <span class="hlt">balance</span> and <span class="hlt">ice</span> dynamics. Net basal melting on the Weddell coast was 51 ± 71 Gt a-1. Recent changes in <span class="hlt">ice</span>-shelf height include increases over major AP <span class="hlt">ice</span> shelves driven by changes in firn state. Basal melt rates near Bawden <span class="hlt">Ice</span> Rise, a major pinning point of Larsen C <span class="hlt">Ice</span> Shelf, showed large increases, potentially leading to substantial loss of buttressing if sustained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12.1211F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12.1211F"><span>Multi-year analysis of distributed glacier <span class="hlt">mass</span> <span class="hlt">balance</span> modelling and equilibrium line altitude on King George Island, Antarctic Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Falk, Ulrike; López, Damián A.; Silva-Busso, Adrián</p> <p>2018-04-01</p> <p>The South Shetland Islands are located at the northern tip of the Antarctic Peninsula (AP). This region was subject to strong warming trends in the atmospheric surface layer. Surface air temperature increased about 3 K in 50 years, concurrent with retreating glacier fronts, an increase in melt areas, <span class="hlt">ice</span> surface lowering and rapid break-up and disintegration of <span class="hlt">ice</span> shelves. The positive trend in surface air temperature has currently come to a halt. Observed surface air temperature lapse rates show a high variability during winter months (standard deviations up to ±1.0 K (100 m)-1) and a distinct spatial heterogeneity reflecting the impact of synoptic weather patterns. The increased mesocyclonic activity during the wintertime over the past decades in the study area results in intensified advection of warm, moist air with high temperatures and rain and leads to melt conditions on the <span class="hlt">ice</span> cap, fixating surface air temperatures to the melting point. Its impact on winter accumulation results in the observed negative <span class="hlt">mass</span> <span class="hlt">balance</span> estimates. Six years of continuous glaciological measurements on <span class="hlt">mass</span> <span class="hlt">balance</span> stake transects as well as 5 years of climatological data time series are presented and a spatially distributed glacier energy <span class="hlt">balance</span> melt model adapted and run based on these multi-year data sets. The glaciological surface <span class="hlt">mass</span> <span class="hlt">balance</span> model is generally in good agreement with observations, except for atmospheric conditions promoting snow drift by high wind speeds, turbulence-driven snow deposition and snow layer erosion by rain. No drift in the difference between simulated <span class="hlt">mass</span> <span class="hlt">balance</span> and <span class="hlt">mass</span> <span class="hlt">balance</span> measurements can be seen over the course of the 5-year model run period. The winter accumulation does not suffice to compensate for the high variability in summer ablation. The results are analysed to assess changes in meltwater input to the coastal waters, specific glacier <span class="hlt">mass</span> <span class="hlt">balance</span> and the equilibrium line altitude (ELA). The Fourcade Glacier catchment drains</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890018779','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890018779"><span><span class="hlt">Ice</span> sheet radar altimetry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, J.</p> <p>1988-01-01</p> <p>The surface topography of the Greenland and Antarctic <span class="hlt">ice</span> sheets between 72 degrees north and south was mapped using radar altimetry data from the U.S. Navy GEOSAT. The glaciological objectives of this activity were to study the dynamics of the <span class="hlt">ice</span> flow, changes in the position of floating <span class="hlt">ice</span>-shelf fronts, and ultimately to measure temporal changes in <span class="hlt">ice</span> surface elevation indicative of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130009418','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130009418"><span>Airborne Tomographic Swath <span class="hlt">Ice</span> Sounding Processing System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wu, Xiaoqing; Rodriquez, Ernesto; Freeman, Anthony; Jezek, Ken</p> <p>2013-01-01</p> <p>Glaciers and <span class="hlt">ice</span> sheets modulate global sea level by storing water deposited as snow on the surface, and discharging water back into the ocean through melting. Their physical state can be characterized in terms of their <span class="hlt">mass</span> <span class="hlt">balance</span> and dynamics. To estimate the current <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>, and to predict future changes in the motion of the Greenland and Antarctic <span class="hlt">ice</span> sheets, it is necessary to know the <span class="hlt">ice</span> sheet thickness and the physical conditions of the <span class="hlt">ice</span> sheet surface and bed. This information is required at fine resolution and over extensive portions of the <span class="hlt">ice</span> sheets. A tomographic algorithm has been developed to take raw data collected by a multiple-channel synthetic aperture sounding radar system over a polar <span class="hlt">ice</span> sheet and convert those data into two-dimensional (2D) <span class="hlt">ice</span> thickness measurements. Prior to this work, conventional processing techniques only provided one-dimensional <span class="hlt">ice</span> thickness measurements along profiles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010066068','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010066068"><span>Determining Greenland <span class="hlt">Ice</span> Sheet Accumulation Rates from Radar Remote Sensing</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jezek, Kenneth C.</p> <p>2001-01-01</p> <p>An important component of NASA's Program for Arctic Regional Climate Assessment (PARCA) is a <span class="hlt">mass</span> <span class="hlt">balance</span> investigation of the Greenland <span class="hlt">Ice</span> Sheet. The <span class="hlt">mass</span> <span class="hlt">balance</span> is calculated by taking the difference between the snow accumulation and the <span class="hlt">ice</span> discharge of the <span class="hlt">ice</span> sheet. Uncertainties in this calculation include the snow accumulation rate, which has traditionally been determined by interpolating data from <span class="hlt">ice</span> core samples taken throughout the <span class="hlt">ice</span> sheet. The sparse data associated with <span class="hlt">ice</span> cores, coupled with the high spatial and temporal resolution provided by remote sensing, have motivated scientists to investigate relationships between accumulation rate and microwave observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GGG....18.2099C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GGG....18.2099C"><span>Short-term variations of Icelandic <span class="hlt">ice</span> cap <span class="hlt">mass</span> inferred from cGPS coordinate time series</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Compton, Kathleen; Bennett, Richard A.; Hreinsdóttir, Sigrún; van Dam, Tonie; Bordoni, Andrea; Barletta, Valentina; Spada, Giorgio</p> <p>2017-06-01</p> <p>As the global climate changes, understanding short-term variations in water storage is increasingly important. Continuously operating Global Positioning System (cGPS) stations in Iceland record annual periodic motion—the elastic response to winter accumulation and spring melt seasons—with peak-to-peak vertical amplitudes over 20 mm for those sites in the Central Highlands. Here for the first time for Iceland, we demonstrate the utility of these cGPS-measured displacements for estimating seasonal and shorter-term <span class="hlt">ice</span> cap <span class="hlt">mass</span> changes. We calculate unit responses to each of the five largest <span class="hlt">ice</span> caps in central Iceland at each of the 62 cGPS locations using an elastic half-space model and estimate <span class="hlt">ice</span> <span class="hlt">mass</span> variations from the cGPS time series using a simple least squares inversion scheme. We utilize all three components of motion, taking advantage of the seasonal motion recorded in the horizontal. We remove secular velocities and accelerations and explore the impact that seasonal motions due to atmospheric, hydrologic, and nontidal ocean loading have on our inversion results. Our results match available summer and winter <span class="hlt">mass</span> <span class="hlt">balance</span> measurements well, and we reproduce the seasonal stake-based observations of loading and melting within the 1σ confidence bounds of the inversion. We identify nonperiodic <span class="hlt">ice</span> <span class="hlt">mass</span> changes associated with interannual variability in precipitation and other processes such as increased melting due to reduced <span class="hlt">ice</span> surface albedo or decreased melting due to <span class="hlt">ice</span> cap insulation in response to tephra deposition following volcanic eruptions, processes that are not resolved with once or twice-yearly stake measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016RvGeo..54..119C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016RvGeo..54..119C"><span>Glacier crevasses: Observations, models, and <span class="hlt">mass</span> <span class="hlt">balance</span> implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Colgan, William; Rajaram, Harihar; Abdalati, Waleed; McCutchan, Cheryl; Mottram, Ruth; Moussavi, Mahsa S.; Grigsby, Shane</p> <p>2016-03-01</p> <p>We review the findings of approximately 60 years of in situ and remote sensing studies of glacier crevasses, as well as the three broad classes of numerical models now employed to simulate crevasse fracture. The relatively new insight that mixed-mode fracture in local stress equilibrium, rather than downstream advection alone, can introduce nontrivial curvature to crevasse geometry may merit the reinterpretation of some key historical observation studies. In the past three decades, there have been tremendous advances in the spatial resolution of satellite imagery, as well as fully automated algorithms capable of tracking crevasse displacements between repeat images. Despite considerable advances in developing fully transient three-dimensional <span class="hlt">ice</span> flow models over the past two decades, both the zero stress and linear elastic fracture mechanics crevasse models have remained fundamentally unchanged over this time. In the past decade, however, multidimensional and transient formulations of the continuum damage mechanics approach to simulating <span class="hlt">ice</span> fracture have emerged. The combination of employing damage mechanics to represent slow upstream deterioration of <span class="hlt">ice</span> strength and fracture mechanics to represent rapid failure at downstream termini holds promise for implementation in large-scale <span class="hlt">ice</span> sheet models. Finally, given the broad interest in the sea level rise implications of recent and future cryospheric change, we provide a synthesis of 10 mechanisms by which crevasses can influence glacier <span class="hlt">mass</span> <span class="hlt">balance</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....5559S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....5559S"><span>Glacial changes and glacier <span class="hlt">mass</span> <span class="hlt">balance</span> at Gran Campo Nevado, Chile during recent decades</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schneider, C.; Schnirch, M.; Kilian, R.; Acuña, C.; Casassa, G.</p> <p>2003-04-01</p> <p>Within the framework of the program Global Land <span class="hlt">Ice</span> Measurements from Space (GLIMS) a glacier inventory of the Peninsula Muñoz Gamero in the southernmost Andes of Chile (53°S) has been generated using aerial photopgrahy and Landsat Thematic Mapper imagery. The Peninsula is partly covered by the <span class="hlt">ice</span> cap of the Gran Campo Nevado (GCN), including several outlet glaciers plus some minor glaciers and firn fields. All together the <span class="hlt">ice</span> covered areas sum up to 260 km2. GCN forms the only major <span class="hlt">ice</span> body between the Southern Patagonia Icefield and the Strait of Magallan. Its almost unique location in a zone affected year-round by the westerlies makes it a region of key interest in terms of glacier and climate change studies of the west-wind zone of the Southern Hemisphere. A digital elevation model (DEM) was created for the area, using aerial imagery from 1942, 1984, and 1998 and a Chilean topographic map (1: 100 000). All information was incorporated into a GIS together with satellite imagery from 1986 and 2001. Delineation of glacier inflow from the central plateau of Gran Campo Nevado was accomplished using an automatic module for watershed delineation within the GIS. The GIS served to outline the extent of the present glaciation of the peninsula, as well as to evaluate the derived historic information. The comparison of historic and recent imagery reveals a dramatic glacier retreat during the last 60 years. Some of the outlet glaciers lost more than 20% of their total area during this period. In February and March 2000 a automatic weather station (AWS) was run on a nameless outlet glacier, inofficially Glaciar Lengua, of the Gran Campo Nevado <span class="hlt">Ice</span> Cap. From the computed energy <span class="hlt">balance</span>, it was possible to derive degree-day factors for the Glaciar Lengua. With data from the nearby AWS at fjord coast (Bahia Bahamondes) we computed ablation for the summer seasons of 1999/2000, 2000/2001 and 2001/2002. Ablation at 450 m a.s.l. sums up to about 7 m in 1999/2000, 5.5 m in 2000</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140012682','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140012682"><span>Influence of Persistent Wind Scour on the Surface <span class="hlt">Mass</span> <span class="hlt">Balance</span> of Antarctica</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Das, Indrani; Bell, Robin E.; Scambos, Ted A.; Wolovick, Michael; Creyts, Timothy T.; Studinger, Michael; Fearson, Nicholas; Nicolas, Julien P.; Lenaerts, Jan T. M.; vandenBroeke, Michiel R.</p> <p>2013-01-01</p> <p>Accurate quantification of surface snow accumulation over Antarctica is a key constraint for estimates of the Antarctic <span class="hlt">mass</span> <span class="hlt">balance</span>, as well as climatic interpretations of <span class="hlt">ice</span>-core records. Over Antarctica, near-surface winds accelerate down relatively steep surface slopes, eroding and sublimating the snow. This wind scour results in numerous localized regions (< or = 200 sq km) with reduced surface accumulation. Estimates of Antarctic surface <span class="hlt">mass</span> <span class="hlt">balance</span> rely on sparse point measurements or coarse atmospheric models that do not capture these local processes, and overestimate the net <span class="hlt">mass</span> input in wind-scour zones. Here we combine airborne radar observations of unconformable stratigraphic layers with lidar-derived surface roughness measurements to identify extensive wind-scour zones over Dome A, in the interior of East Antarctica. The scour zones are persistent because they are controlled by bedrock topography. On the basis of our Dome A observations, we develop an empirical model to predict wind-scour zones across the Antarctic continent and find that these zones are predominantly located in East Antarctica. We estimate that approx. 2.7-6.6% of the surface area of Antarctica has persistent negative net accumulation due to wind scour, which suggests that, across the continent, the snow <span class="hlt">mass</span> input is overestimated by 11-36.5 Gt /yr in present surface-<span class="hlt">mass-balance</span> calculations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28973875','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28973875"><span>Katabatic winds diminish precipitation contribution to the Antarctic <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Grazioli, Jacopo; Madeleine, Jean-Baptiste; Gallée, Hubert; Forbes, Richard M; Genthon, Christophe; Krinner, Gerhard; Berne, Alexis</p> <p>2017-10-10</p> <p>Snowfall in Antarctica is a key term of the <span class="hlt">ice</span> sheet <span class="hlt">mass</span> budget that influences the sea level at global scale. Over the continental margins, persistent katabatic winds blow all year long and supply the lower troposphere with unsaturated air. We show that this dry air leads to significant low-level sublimation of snowfall. We found using unprecedented data collected over 1 year on the coast of Adélie Land and simulations from different atmospheric models that low-level sublimation accounts for a 17% reduction of total snowfall over the continent and up to 35% on the margins of East Antarctica, significantly affecting satellite-based estimations close to the ground. Our findings suggest that, as climate warming progresses, this process will be enhanced and will limit expected precipitation increases at the ground level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA601787','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA601787"><span><span class="hlt">Mass</span> <span class="hlt">Balance</span> of Multiyear Sea <span class="hlt">Ice</span> in the Southern Beaufort Sea</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2013-09-30</p> <p>model of MY <span class="hlt">ice</span> circulation, which is shown in Figure 1. In this model , we consider the Beaufort Sea to consist of four zones defined by mean drift...Arctic Regional Climate Model Simulation Project 3 International Arctic Buoy Program 4 Sea <span class="hlt">ice</span> Experiment - Dynamic Nature of the Arctic 5Cold...2 Table 2: Datasets compiled to date Geophysical data type Source Time period acquired Buoy tracks IABP 12 hrly position data 1978-2012 <span class="hlt">Ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1013710','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1013710"><span><span class="hlt">Mass</span> <span class="hlt">Balance</span> of Multiyear Sea <span class="hlt">Ice</span> in the Southern Beaufort Sea</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2015-09-30</p> <p>1) Determination of the net growth and melt of multiyear (MY) sea <span class="hlt">ice</span> during its transit through the southern Beaufort Sea 2) Identification of...which we refer to as the FGIV dataset. Analysis of melt processes from <span class="hlt">ice</span> core and IMB data (Eicken) Through stratigraphic analysis of sea <span class="hlt">ice</span>...samples that are brought back to shore were melted and used to determine profiles of salinity and stable isotope ratios. These data allow us to identify</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://link.springer.com/article/10.1007%2Fs10498-013-9199-2','USGSPUBS'); return false;" href="http://link.springer.com/article/10.1007%2Fs10498-013-9199-2"><span>Climate, not atmospheric deposition, drives the biogeochemical <span class="hlt">mass-balance</span> of a mountain watershed</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Baron, Jill S.; Heath, Jared</p> <p>2014-01-01</p> <p>Watershed <span class="hlt">mass-balance</span> methods are valuable tools for demonstrating impacts to water quality from atmospheric deposition and chemical weathering. Owen Bricker, a pioneer of the <span class="hlt">mass-balance</span> method, began applying <span class="hlt">mass-balance</span> modeling to small watersheds in the late 1960s and dedicated his career to expanding the literature and knowledge of complex watershed processes. We evaluated long-term trends in surface-water chemistry in the Loch Vale watershed, a 660-ha. alpine/subalpine catchment located in Rocky Mountain National Park, CO, USA. Many changes in surface-water chemistry correlated with multiple drivers, including summer or monthly temperature, snow water equivalent, and the runoff-to-precipitation ratio. Atmospheric deposition was not a significant causal agent for surface-water chemistry trends. We observed statistically significant increases in both concentrations and fluxes of weathering products including cations, SiO2, SO4 2−, and ANC, and in inorganic N, with inorganic N being primarily of atmospheric origin. These changes are evident in the individual months June, July, and August, and also in the combined June, July, and August summer season. Increasingly warm summer temperatures are melting what was once permanent <span class="hlt">ice</span> and this may release elements entrained in the <span class="hlt">ice</span>, stimulate chemical weathering with enhanced moisture availability, and stimulate microbial nitrification. Weathering rates may also be enhanced by sustained water availability in high snowpack years. Rapid change in the flux of weathering products and inorganic N is the direct and indirect result of a changing climate from warming temperatures and thawing cryosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.7705P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.7705P"><span>Climate dependent contrast in surface <span class="hlt">mass</span> <span class="hlt">balance</span> in East Antarctica over the past 216 kyr</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parrenin, Frédéric; Fujita, Shuji; Abe-Ouchi, Ayako; Kawamura, Kenji; Masson-Delmotte, Valérie; Motoyama, Hideaki; Saito, Fuyuki; Severi, Mirko; Stenni, Barbara; Uemura, Ryu; Wolff, Eric</p> <p>2016-04-01</p> <p>Documenting past changes in the East Antarctic surface <span class="hlt">mass</span> <span class="hlt">balance</span> is important to improve <span class="hlt">ice</span> core chronologies and to constrain the <span class="hlt">ice</span> sheet contribution to global mean sea level change. Here we reconstruct the past changes in the ratio of surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB ratio) between the EPICA Dome C (EDC) and Dome Fuji (DF) East Antarctica <span class="hlt">ice</span> core sites, based on a precise volcanic synchronisation of the two <span class="hlt">ice</span> cores and on corrections for the vertical thinning of layers. During the past 216,000 years, this SMB ratio, denoted SMB_EDC/SMB_DF, varied between 0.7 and 1.1, being small during cold periods and large during warm periods. While past climatic changes have been depicted as homogeneous along the East Antarctic Plateau, our results reveal larger amplitudes of changes in SMB at EDC compared to DF, consistent with previous results showing larger amplitudes of changes in water stable isotopes and estimated surface temperature at EDC compared to DF. Within the last glacial inception (Marine Isotope Stages, MIS-5c and MIS-5d), the SMB ratio deviates by up to 20% from what is expected based on differences in water stable isotope records. Moreover, the SMB ratio is constant throughout the late parts of the current and last interglacial periods, despite contrasting isotopic trends. These SMB ratio changes not reflected in the isotope profiles are one of the possible causes of the observed differences between the <span class="hlt">ice</span> core chronologies at DF and EDC. Such changes in SMB ratio may have been caused by (i) climatic processes related to changes in air <span class="hlt">mass</span> trajectories and local climate, (ii) glaciological processes associated with relative elevation changes, or (iii) a combination of climatic and glaciological processes, such as the interaction between changes in accumulation and in the position of the domes. Our inferred SMB ratio history has important implications for <span class="hlt">ice</span> sheet modeling (for which SMB is a boundary condition) or atmospheric modeling (our inferred SMB</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CliPD..11..377P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CliPD..11..377P"><span>Climate dependent contrast in surface <span class="hlt">mass</span> <span class="hlt">balance</span> in East Antarctica over the past 216 kyr</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parrenin, F.; Fujita, S.; Abe-Ouchi, A.; Kawamura, K.; Masson-Delmotte, V.; Motoyama, H.; Saito, F.; Severi, M.; Stenni, B.; Uemura, R.; Wolff, E.</p> <p>2015-02-01</p> <p>Documenting past changes in the East Antarctic surface <span class="hlt">mass</span> <span class="hlt">balance</span> is important to improve <span class="hlt">ice</span> core chronologies and to constrain the <span class="hlt">ice</span> sheet contribution to global mean sea level. Here we reconstruct the past changes in the ratio of surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB ratio) between the EPICA Dome C (EDC) and Dome Fuji (DF) East Antarctica <span class="hlt">ice</span> core sites, based on a precise volcanic synchronisation of the two <span class="hlt">ice</span> cores and on corrections for the vertical thinning of layers. During the past 216 000 years, this SMB ratio, denoted SMBEDC/SMBDF, varied between 0.7 and 1.1, decreasing during cold periods and increasing during warm periods. While past climatic changes have been depicted as homogeneous along the East Antarctic Plateau, our results reveal larger amplitudes of changes in SMB at EDC compared to DF, consistent with previous results showing larger amplitudes of changes in water stable isotopes and estimated surface temperature at EDC compared to DF. Within interglacial periods and during the last glacial inception (Marine Isotope Stages, MIS-5c and MIS-5d), the SMB ratio deviates by up to 30% from what is expected based on differences in water stable isotope records. Moreover, the SMB ratio is constant throughout the late parts of the current and last interglacial periods, despite contrasting isotopic trends. These SMB ratio changes not closely related to isotopic changes are one of the possible causes of the observed gaps between the <span class="hlt">ice</span> core chronologies at DF and EDC. Such changes in SMB ratio may have been caused by (i) climatic processes related to changes in air <span class="hlt">mass</span> trajectories and local climate, (ii) glaciological processes associated with relative elevation changes, or (iii) a combination of climatic and glaciological processes, such as the interaction between changes in accumulation and in the position of the domes. Our inferred SMB ratio history has important implications for <span class="hlt">ice</span> sheet modeling (for which SMB is a boundary condition) or atmospheric</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C21E..02I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C21E..02I"><span>Measurements of sea <span class="hlt">ice</span> <span class="hlt">mass</span> redistribution during <span class="hlt">ice</span> deformation event in Arctic winter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Itkin, P.; Spreen, G.; King, J.; Rösel, A.; Skourup, H.; Munk Hvidegaard, S.; Wilkinson, J.; Oikkonen, A.; Granskog, M. A.; Gerland, S.</p> <p>2016-12-01</p> <p>Sea-<span class="hlt">ice</span> growth during high winter is governed by <span class="hlt">ice</span> dynamics. The highest growth rates are found in leads that open under divergent conditions, where exposure to the cold atmosphere promotes thermodynamic growth. Additionally <span class="hlt">ice</span> thickens dynamically, where convergence causes rafting and ridging. We present a local study of sea-<span class="hlt">ice</span> growth and <span class="hlt">mass</span> redistribution between two consecutive airborne measurements, on 19 and 24 April 2015, during the N-<span class="hlt">ICE</span>2015 expedition in the area north of Svalbard. Between the two overflights an <span class="hlt">ice</span> deformation event was observed. Airborne laser scanner (ALS) measurements revisited the same sea-<span class="hlt">ice</span> area of approximately 3x3 km. By identifying the sea surface within the ALS measurements as a reference the sea <span class="hlt">ice</span> plus snow freeboard was obtained with a spatial resolution of 5 m. By assuming isostatic equilibrium of level floes, the freeboard heights can be converted to <span class="hlt">ice</span> thickness. The snow depth is estimated from in-situ measurements. Sea <span class="hlt">ice</span> thickness measurements were made in the same area as the ALS measurements by electromagnetic sounding from a helicopter (HEM), and with a ground-based device (EM31), which allows for cross-validation of the sea-<span class="hlt">ice</span> thickness estimated from all 3 procedures. Comparison of the ALS snow freeboard distributions between the first and second overflight shows a decrease in the thin <span class="hlt">ice</span> classes and an increase of the thick <span class="hlt">ice</span> classes. While there was no observable snowfall and a very low sea-<span class="hlt">ice</span> growth of older level <span class="hlt">ice</span> during this period, an autonomous buoy array deployed in the surroundings of the area measured by the ALS shows first divergence followed by convergence associated with shear. To quantify and link the sea <span class="hlt">ice</span> deformation with the associated sea-<span class="hlt">ice</span> thickness change and <span class="hlt">mass</span> redistribution we identify over 100 virtual buoys in the ALS data from both overflights. We triangulate the area between the buoys and calculate the strain rates and freeboard change for each individual triangle</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007GPC....59...17S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007GPC....59...17S"><span>Recent evolution and <span class="hlt">mass</span> <span class="hlt">balance</span> of Cordón Martial glaciers, Cordillera Fueguina Oriental</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Strelin, Jorge; Iturraspe, Rodolfo</p> <p>2007-10-01</p> <p>Past and present glacier changes have been studied at Cordón Martial, Cordillera Fueguina Oriental, Tierra del Fuego, providing novel data for the Holocene deglaciation history of southern South America and extrapolating as well its future behavior based on predicted climatic changes. Regional geomorphologic and stratigraphic correlations indicate that the last glacier advance deposited the <span class="hlt">ice</span>-proximal ("internal") moraines of Cordón Martial, around 330 14C yr BP, during the Late Little <span class="hlt">Ice</span> Age (LLIA). Since then glaciers have receded slowly, until 60 years ago, when major glacier retreat started. There is a good correspondence for the past 100 years between the surface area variation of four small cirque glaciers at Cordón Martial and the annual temperature and precipitation data of Ushuaia. Between 1984 and 1998, Martial Este Glacier lost 0.64 ± 0.02 × 10 6 m 3 of <span class="hlt">ice</span> <span class="hlt">mass</span> (0.59 ± 0.02 × 10 6 m 3 w.e.), corresponding to an average <span class="hlt">ice</span> thinning of 7.0 ± 0.2 m (6.4 ± 0.2 m w.e), according to repeated topographic mapping. More detailed climatic data have been obtained since 1998 at the Martial Este Glacier, including air temperature, humidity and solar radiation. These records, together with the monthly <span class="hlt">mass</span> <span class="hlt">balance</span> measured since March 2000, document the annual response of the Martial Este Glacier to the climate variation. <span class="hlt">Mass</span> <span class="hlt">balances</span> during hydrological years were positive in 2000, negative in 2001 and near equilibrium in 2002. Finally, using these data and the regional temperature trend projections, modeled for different future scenarios by the Atmosphere-Ocean Model (GISS-NASA/GSFC), potential climatic-change effects on this mountain glacier were extrapolated. The analysis shows that only the Martial Este Glacier may survive this century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5642703','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5642703"><span>Katabatic winds diminish precipitation contribution to the Antarctic <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Grazioli, Jacopo; Madeleine, Jean-Baptiste; Gallée, Hubert; Forbes, Richard M.; Genthon, Christophe; Krinner, Gerhard; Berne, Alexis</p> <p>2017-01-01</p> <p>Snowfall in Antarctica is a key term of the <span class="hlt">ice</span> sheet <span class="hlt">mass</span> budget that influences the sea level at global scale. Over the continental margins, persistent katabatic winds blow all year long and supply the lower troposphere with unsaturated air. We show that this dry air leads to significant low-level sublimation of snowfall. We found using unprecedented data collected over 1 year on the coast of Adélie Land and simulations from different atmospheric models that low-level sublimation accounts for a 17% reduction of total snowfall over the continent and up to 35% on the margins of East Antarctica, significantly affecting satellite-based estimations close to the ground. Our findings suggest that, as climate warming progresses, this process will be enhanced and will limit expected precipitation increases at the ground level. PMID:28973875</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011MsT.........18M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011MsT.........18M"><span>Quantification of Changes for the Milne <span class="hlt">Ice</span> Shelf, Nunavut, Canada, 1950 -- 2009</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mortimer, Colleen Adel</p> <p></p> <p>This study presents a comprehensive overview of the current state of the Milne <span class="hlt">Ice</span> Shelf and how it has changed over the last 59 years. The 205 +/-1 km2 <span class="hlt">ice</span> shelf experienced a 28% (82 +/-0.8 km 2) reduction in area between 1950 -- 2009, and a 20% (2.5 +/-0.9km 3 water equivalent (w.e.)) reduction in volume between 1981 -- 2008/2009, suggesting a long-term state of negative <span class="hlt">mass</span> <span class="hlt">balance</span>. Comparison of mean annual specific <span class="hlt">mass</span> <span class="hlt">balances</span> (up to -0.34 m w.e. yr-1) with surface <span class="hlt">mass</span> <span class="hlt">balance</span> measurements for the nearby Ward Hunt <span class="hlt">Ice</span> Shelf suggest that basal melt is a key contributor to total <span class="hlt">ice</span> shelf thinning. The development and expansion of new and existing surface cracks, as well as <span class="hlt">ice</span>-marginal and epishelf lake development, indicate significant <span class="hlt">ice</span> shelf weakening. Over the next few decades it is likely that the Milne <span class="hlt">Ice</span> Shelf will continue to deteriorate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C51D..08S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C51D..08S"><span>High-resolution DEMs for High-mountain Asia: A systematic, region-wide assessment of geodetic glacier <span class="hlt">mass</span> <span class="hlt">balance</span> and dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shean, D. E.; Arendt, A. A.; Osmanoglu, B.; Montesano, P.</p> <p>2017-12-01</p> <p>High Mountain Asia (HMA) constitutes the largest glacierized region outside of the Earth's polar regions. Although available observations are limited, long-term records indicate sustained regional glacier <span class="hlt">mass</span> loss since 1850, with increased loss in recent decades. Recent satellite data (e.g., GRACE, ICESat-1) show spatially variable glacier <span class="hlt">mass</span> <span class="hlt">balance</span>, with significant <span class="hlt">mass</span> loss in the Himalaya and Hindu Kush and slight <span class="hlt">mass</span> gain in the Karakoram. We generated 4000 high-resolution digital elevation models (DEMs) from sub-meter commercial stereo imagery (DigitalGlobe WorldView/GeoEye) acquired over glaciers in High-mountain Asia from 2002-present (mostly 2013-present). We produced a regional 8-m DEM mosaic for 2015 and estimated 15-year geodetic <span class="hlt">mass</span> <span class="hlt">balance</span> for 40000 glaciers larger than 0.1 km2. We are combining with other regional DEM sources to systematically document the spatiotemporal evolution of glacier <span class="hlt">mass</span> <span class="hlt">balance</span> for the entire HMA region. We also generated monthly to interannual DEM and velocity time series for high-priority sites distributed across the region, with >15-20 DEMs available for some locations from 2010-present. These records document glacier dynamics, seasonal snow accumulation/redistribution, and processes that affect glacier <span class="hlt">mass</span> <span class="hlt">balance</span> (e.g., <span class="hlt">ice</span>-cliff retreat, debris cover evolution). These efforts will provide basin-scale assessments of snow/<span class="hlt">ice</span> melt runoff contributions for model cal/val and downstream water resources applications. We will continue processing all archived and newly available commercial stereo imagery for HMA, and will release all DEMs through the HiMAT DAAC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.water.usgs.gov/wri004265','USGSPUBS'); return false;" href="http://pubs.water.usgs.gov/wri004265"><span>Water, <span class="hlt">ice</span>, meteorological, and speed measurements at South Cascade Glacier, Washington, 1999 <span class="hlt">balance</span> year</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Krimmel, Robert M.</p> <p>2001-01-01</p> <p>Winter snow accumulation and summer snow, firn, and <span class="hlt">ice</span> melt were measured at South Cascade Glacier, Washington, to determine the winter and net <span class="hlt">balances</span> for the 1999 <span class="hlt">balance</span> year. The 1999 winter snow <span class="hlt">balance</span>, averaged over the glacier, was 3.59 meters, and the net <span class="hlt">balance</span> was 1.02 meters. Since the winter <span class="hlt">balance</span> record began in 1959, only three winters have had a higher winter <span class="hlt">balance</span>. Since the net <span class="hlt">balance</span> record began in 1953, only 2 years have had a greater positive net <span class="hlt">balance</span> than 1999. Runoff was measured from the glacier and an adjacent non-glacierized basin. Air temperature, precipitation, and humidity were measured nearby, and <span class="hlt">ice</span> speed was measured. This report makes these data available to the glaciological and climatological community.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12.1511H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12.1511H"><span>Simulating <span class="hlt">ice</span> thickness and velocity evolution of Upernavik Isstrøm 1849-2012 by forcing prescribed terminus positions in ISSM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haubner, Konstanze; Box, Jason E.; Schlegel, Nicole J.; Larour, Eric Y.; Morlighem, Mathieu; Solgaard, Anne M.; Kjeldsen, Kristian K.; Larsen, Signe H.; Rignot, Eric; Dupont, Todd K.; Kjær, Kurt H.</p> <p>2018-04-01</p> <p>Tidewater glacier velocity and <span class="hlt">mass</span> <span class="hlt">balance</span> are known to be highly responsive to terminus position change. Yet it remains challenging for <span class="hlt">ice</span> flow models to reproduce observed <span class="hlt">ice</span> margin changes. Here, using the <span class="hlt">Ice</span> Sheet System Model (ISSM; Larour et al. 2012), we simulate the <span class="hlt">ice</span> velocity and thickness changes of Upernavik Isstrøm (north-western Greenland) by prescribing a collection of 27 observed terminus positions spanning 164 years (1849-2012). The simulation shows increased <span class="hlt">ice</span> velocity during the 1930s, the late 1970s and between 1995 and 2012 when terminus retreat was observed along with negative surface <span class="hlt">mass</span> <span class="hlt">balance</span> anomalies. Three distinct <span class="hlt">mass</span> <span class="hlt">balance</span> states are evident in the reconstruction: (1849-1932) with near zero <span class="hlt">mass</span> <span class="hlt">balance</span>, (1932-1992) with <span class="hlt">ice</span> <span class="hlt">mass</span> loss dominated by <span class="hlt">ice</span> dynamical flow, and (1998-2012), when increased retreat and negative surface <span class="hlt">mass</span> <span class="hlt">balance</span> anomalies led to <span class="hlt">mass</span> loss that was twice that of any earlier period. Over the multi-decadal simulation, <span class="hlt">mass</span> loss was dominated by thinning and acceleration responsible for 70 % of the total <span class="hlt">mass</span> loss induced by prescribed change in terminus position. The remaining 30 % of the total <span class="hlt">ice</span> <span class="hlt">mass</span> loss resulted directly from prescribed terminus retreat and decreasing surface <span class="hlt">mass</span> <span class="hlt">balance</span>. Although the method can not explain the cause of glacier retreat, it enables the reconstruction of <span class="hlt">ice</span> flow and geometry during 1849-2012. Given annual or seasonal observed terminus front positions, this method could be a useful tool for evaluating simulations investigating the effect of calving laws.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1255085-reactivation-kamb-ice-stream-tributaries-triggers-century-scale-reorganization-siple-coast-ice-flow-west-antarctica','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1255085-reactivation-kamb-ice-stream-tributaries-triggers-century-scale-reorganization-siple-coast-ice-flow-west-antarctica"><span>Reactivation of Kamb <span class="hlt">Ice</span> Stream tributaries triggers century-scale reorganization of Siple Coast <span class="hlt">ice</span> flow in West Antarctica</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Bougamont, M.; Christoffersen, P.; Price, S. F.; ...</p> <p>2015-10-21</p> <p>Ongoing, centennial-scale flow variability within the Ross <span class="hlt">ice</span> streams of West Antarctica suggests that the present-day positive <span class="hlt">mass</span> <span class="hlt">balance</span> in this region may reverse in the future. Here we use a three-dimensional <span class="hlt">ice</span> sheet model to simulate <span class="hlt">ice</span> flow in this region over 250 years. The flow responds to changing basal properties, as a subglacial till layer interacts with water transported in an active subglacial hydrological system. We show that a persistent weak bed beneath the tributaries of the dormant Kamb <span class="hlt">Ice</span> Stream is a source of internal <span class="hlt">ice</span> flow instability, which reorganizes all <span class="hlt">ice</span> streams in this region, leadingmore » to a reduced (positive) <span class="hlt">mass</span> <span class="hlt">balance</span> within decades and a net loss of <span class="hlt">ice</span> within two centuries. This hitherto unaccounted for flow variability could raise sea level by 5 mm this century. Furthermore, better constraints on future sea level change from this region will require improved estimates of geothermal heat flux and subglacial water transport.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C34A..04C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C34A..04C"><span>Representativeness of regional and global <span class="hlt">mass-balance</span> measurement networks (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cogley, J. G.; Moholdt, G.; Gardner, A. S.</p> <p>2013-12-01</p> <p>We showed in a recent publication that regional estimates of glacier <span class="hlt">mass</span> budgets, obtained by interpolation from in-situ measurements, were markedly more negative than corresponding estimates by satellite gravimetry (GRACE) and satellite altimetry (ICESat) during 2003-2009. Examining the ICESat data in more detail, we found that in-situ records tend to be located in areas where glaciers are thinning more rapidly than as observed in their regional surroundings. Because neither GRACE nor ICESat can provide information for times before 2002-2003, and may not operate without interruption in the future, we explore possible explanations of and remedies for the identified bias in the in-situ network. Sparse spatial sampling, coupled with previously undetected spatial variability of <span class="hlt">mass</span> <span class="hlt">balance</span> at scales between the 10-km in-situ scale and the 350-km gravimetric scale, appears to be the leading explanation. Satisfactory remedies are not obvious. Selecting glaciers for in-situ measurement that are more representative will yield only incremental improvements. There appears to be no alternative to <span class="hlt">mass-balance</span> modelling as a versatile tool for estimation of regional <span class="hlt">mass</span> <span class="hlt">balance</span>. However the meteorological data for forcing the surface components of glacier models have coarser resolution than is desirable and are themselves uncertain, especially in the remote regions where much of the glacier <span class="hlt">ice</span> is found. Measurements of frontal (dynamic) <span class="hlt">mass</span> changes are still difficult, and modelling of these changes remains underdeveloped in spite of recent advances. Thus research on a broad scale is called for in order to meet the challenge of producing more accurate hindcasts and projections of glacier <span class="hlt">mass</span> budgets with fine spatial and temporal resolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.5867S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.5867S"><span>Changes in <span class="hlt">ice</span> dynamics along the northern Antarctic Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seehaus, Thorsten; Marinsek, Sebastian; Cook, Alison; Van Wessem, Jan-Melchior; Braun, Matthias</p> <p>2017-04-01</p> <p>The climatic conditions along the Antarctic Peninsula have undergone considerable changes during the last 50 years. A period of pronounced air temperature rise, increasing ocean temperatures as well as changes in the precipitation pattern have been reported by various authors. Consequently, the glacial systems showed changes including widespread retreat, surface lowering as well as variations in flow speeds. During the last decades numerous <span class="hlt">ice</span> shelves along the Antarctic Peninsula retreated, started to break-up or disintegrated completely. The loss of the buttressing effect caused tributary glaciers to accelerate with increasing <span class="hlt">ice</span> discharge along the Antarctic Peninsula. Quantification of the <span class="hlt">mass</span> changes is still subject to considerable errors although numbers derived from the different methods are converging. The aim is to study the reaction of glaciers at the northern Antarctic Peninsula to the changing climatic conditions and the readjustments of tributary glaciers to <span class="hlt">ice</span> shelf disintegration, as well as to better quantify the <span class="hlt">ice</span> <span class="hlt">mass</span> loss and its temporal changes. We analysed time series of various satellite sensors (ERS-1/2 SAR, ENVISAT ASAR, RADARSAT-1, ALOS PALSAR, TerraSAR-X/TanDEM-X, ASTER, Landsat) to detect changes in <span class="hlt">ice</span> dynamics of 74 glacier basins along the northern Antarctic Peninsula (<65°). Intensity feature tracking techniques were applied on data stacks from different SAR satellites over the last 20 years to infer temporal trends in glacier surface velocities. In combination with <span class="hlt">ice</span> thickness reconstructions and modeled climatic <span class="hlt">mass</span> <span class="hlt">balance</span> fields regional imbalances were calculated. Variations in <span class="hlt">ice</span> front position were mapped based on optical and SAR satellite data sets. Along the west coast of the northern Antarctic Peninsula an increase in flow speeds by 40% between 1992 and 2014 was observed, whereas glaciers on the east side (north of former Prince-Gustav <span class="hlt">Ice</span> Shelf) showed a strong deceleration. Nearly all former <span class="hlt">ice</span> shelf</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014TCry....8..743G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014TCry....8..743G"><span>Empirical estimation of present-day Antarctic glacial isostatic adjustment and <span class="hlt">ice</span> <span class="hlt">mass</span> change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gunter, B. C.; Didova, O.; Riva, R. E. M.; Ligtenberg, S. R. M.; Lenaerts, J. T. M.; King, M. A.; van den Broeke, M. R.; Urban, T.</p> <p>2014-04-01</p> <p>This study explores an approach that simultaneously estimates Antarctic <span class="hlt">mass</span> <span class="hlt">balance</span> and glacial isostatic adjustment (GIA) through the combination of satellite gravity and altimetry data sets. The results improve upon previous efforts by incorporating a firn densification model to account for firn compaction and surface processes as well as reprocessed data sets over a slightly longer period of time. A range of different Gravity Recovery and Climate Experiment (GRACE) gravity models were evaluated and a new <span class="hlt">Ice</span>, Cloud, and Land Elevation Satellite (ICESat) surface height trend map computed using an overlapping footprint approach. When the GIA models created from the combination approach were compared to in situ GPS ground station displacements, the vertical rates estimated showed consistently better agreement than recent conventional GIA models. The new empirically derived GIA rates suggest the presence of strong uplift in the Amundsen Sea sector in West Antarctica (WA) and the Philippi/Denman sectors, as well as subsidence in large parts of East Antarctica (EA). The total GIA-related <span class="hlt">mass</span> change estimates for the entire Antarctic <span class="hlt">ice</span> sheet ranged from 53 to 103 Gt yr-1, depending on the GRACE solution used, with an estimated uncertainty of ±40 Gt yr-1. Over the time frame February 2003-October 2009, the corresponding <span class="hlt">ice</span> <span class="hlt">mass</span> change showed an average value of -100 ± 44 Gt yr-1 (EA: 5 ± 38, WA: -105 ± 22), consistent with other recent estimates in the literature, with regional <span class="hlt">mass</span> loss mostly concentrated in WA. The refined approach presented in this study shows the contribution that such data combinations can make towards improving estimates of present-day GIA and <span class="hlt">ice</span> <span class="hlt">mass</span> change, particularly with respect to determining more reliable uncertainties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990071137&hterms=ice+mechanics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dice%2Bmechanics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990071137&hterms=ice+mechanics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dice%2Bmechanics"><span><span class="hlt">Ice</span> Flow in the North East Greenland <span class="hlt">Ice</span> Stream</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Joughin, Ian; Kwok, Ron; Fahnestock, M.; MacAyeal, Doug</p> <p>1999-01-01</p> <p>Early observations with ERS-1 SAR image data revealed a large <span class="hlt">ice</span> stream in North East Greenland (Fahnestock 1993). The <span class="hlt">ice</span> stream has a number of the characteristics of the more closely studied <span class="hlt">ice</span> streams in Antarctica, including its large size and gross geometry. The onset of rapid flow close to the <span class="hlt">ice</span> divide and the evolution of its flow pattern, however, make this <span class="hlt">ice</span> stream unique. These features can be seen in the <span class="hlt">balance</span> velocities for the <span class="hlt">ice</span> stream (Joughin 1997) and its outlets. The <span class="hlt">ice</span> stream is identifiable for more than 700 km, making it much longer than any other flow feature in Greenland. Our research goals are to gain a greater understanding of the <span class="hlt">ice</span> flow in the northeast Greenland <span class="hlt">ice</span> stream and its outlet glaciers in order to assess their impact on the past, present, and future <span class="hlt">mass</span> <span class="hlt">balance</span> of the <span class="hlt">ice</span> sheet. We will accomplish these goals using a combination of remotely sensed data and <span class="hlt">ice</span> sheet models. We are using satellite radar interferometry data to produce a complete maps of velocity and topography over the entire <span class="hlt">ice</span> stream. We are in the process of developing methods to use these data in conjunction with existing <span class="hlt">ice</span> sheet models similar to those that have been used to improve understanding of the mechanics of flow in Antarctic <span class="hlt">ice</span> streams.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100033560','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100033560"><span>Miniature Piezoelectric Macro-<span class="hlt">Mass</span> <span class="hlt">Balance</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sherrit, Stewart; Trebi-Ollennu, Ashitey; Bonitz, Robert G.; Bar-Cohen, Yoseph</p> <p>2010-01-01</p> <p><span class="hlt">Mass</span> <span class="hlt">balances</span> usually use a strain gauge that requires an impedance measurement and is susceptible to noise and thermal drift. A piezoelectric <span class="hlt">balance</span> can be used to measure <span class="hlt">mass</span> directly by monitoring the voltage developed across the piezoelectric <span class="hlt">balance</span>, which is linear with weight or it can be used in resonance to produce a frequency change proportional to the <span class="hlt">mass</span> change (see figure). The piezoelectric actuator/<span class="hlt">balance</span> is swept in frequency through its fundamental resonance. If a small <span class="hlt">mass</span> is added to the <span class="hlt">balance</span>, the resonance frequency shifts down in proportion to the <span class="hlt">mass</span>. By monitoring the frequency shift, the <span class="hlt">mass</span> can be determined. This design allows for two independent measurements of <span class="hlt">mass</span>. Additionally, more than one sample can be verified because this invention allows for each sample to be transported away from the measuring device upon completion of the measurement, if required. A piezoelectric actuator, or many piezoelectric actuators, was placed between the collection plate of the sampling system and the support structure. As the sample <span class="hlt">mass</span> is added to the plate, the piezoelectrics are stressed, causing them to produce a voltage that is proportional to the <span class="hlt">mass</span> and acceleration. In addition, a change in <span class="hlt">mass</span> delta m produces a change in the resonance frequency with delta f proportional to delta m. In a microgravity environment, the spacecraft could be accelerated to produce a force on the piezoelectric actuator that would produce a voltage proportional to the <span class="hlt">mass</span> and acceleration. Alternatively, the acceleration could be used to force the <span class="hlt">mass</span> on the plate, and the inertial effects of the <span class="hlt">mass</span> on the plate would produce a shift in the resonance frequency with the change in frequency related to the <span class="hlt">mass</span> change. Three prototypes of the <span class="hlt">mass</span> <span class="hlt">balance</span> mechanism were developed. These macro-<span class="hlt">mass</span> <span class="hlt">balances</span> each consist of a solid base and an APA 60 Cedrat flextensional piezoelectric actuator supporting a measuring plate. A similar structure with 3 APA</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1579W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1579W"><span>Early 21st-Century <span class="hlt">Mass</span> loss of the North-Atlantic Glaciers and <span class="hlt">Ice</span> Caps (Arne Richter Award for Outstanding Young Scientists Lecture)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wouters, Bert; Ligtenberg, Stefan; Moholdt, Geir; Gardner, Alex S.; Noel, Brice; Kuipers Munneke, Peter; van den Broeke, Michiel; Bamber, Jonathan L.</p> <p>2016-04-01</p> <p>Historically, <span class="hlt">ice</span> loss from mountain glaciers and <span class="hlt">ice</span> caps has been one of the largest contributors to sea level rise over the last century. Of particular interest are the glaciers and <span class="hlt">ice</span> caps in the North-Atlantic region of the Arctic. Despite the cold climate in this area, considerable melting and runoff occurs in summer. A small increase in temperature will have an immediate effect on these processes, so that a large change in the Arctic <span class="hlt">ice</span> volume can be expected in response to the anticipated climate change in the coming century. Unfortunately, direct observations of glaciers are sparse and are biased toward glaciers systems in accessible, mostly maritime, climate conditions. Remote sensing is therefore essential to monitor the state of the the North-Atlantic glaciers and <span class="hlt">ice</span> caps. In this presentation, we will discuss the progress that has been made in estimating the <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> of these regions, with a particular focus on measurements made by ESA's Cryosat-2 radar altimeter mission (2010-present). Compared to earlier altimeter mission, Cryosat-2 provides unprecedented coverage of the cryosphere, with a resolution down to 1 km or better and sampling at monthly intervals. Combining the Cryosat-2 measurements with the laser altimetry data from ICESat (2003-2009) gives us a 12 yr time series of glacial <span class="hlt">mass</span> loss in the North Atlantic. We find excellent agreement between the altimetry measurements and independent observations by the GRACE mission, which directly 'weighs' the <span class="hlt">ice</span> caps, albeit at a much lower resolution. <span class="hlt">Mass</span> loss in the region has increased from 120 Gigatonnes per year in 2003-2009 to roughly 140 Gt/yr in 2010-2014, with an important contribution from Greenland's peripheral glaciers and <span class="hlt">ice</span> caps. Importantly, the <span class="hlt">mass</span> loss is not stationary, but shows large regional interannual variability, with <span class="hlt">mass</span> loss shifting between eastern and western regions from year to year. Comparison with regional climate models shows that these shifts can be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2011-title14-vol1/pdf/CFR-2011-title14-vol1-sec23-659.pdf','CFR2011'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2011-title14-vol1/pdf/CFR-2011-title14-vol1-sec23-659.pdf"><span>14 CFR 23.659 - <span class="hlt">Mass</span> <span class="hlt">balance</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2011&page.go=Go">Code of Federal Regulations, 2011 CFR</a></p> <p></p> <p>2011-01-01</p> <p>... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false <span class="hlt">Mass</span> <span class="hlt">balance</span>. 23.659 Section 23.659 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... Surfaces § 23.659 <span class="hlt">Mass</span> <span class="hlt">balance</span>. The supporting structure and the attachment of concentrated <span class="hlt">mass</span> <span class="hlt">balance</span>...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2010-title14-vol1/pdf/CFR-2010-title14-vol1-sec23-659.pdf','CFR'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2010-title14-vol1/pdf/CFR-2010-title14-vol1-sec23-659.pdf"><span>14 CFR 23.659 - <span class="hlt">Mass</span> <span class="hlt">balance</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2010&page.go=Go">Code of Federal Regulations, 2010 CFR</a></p> <p></p> <p>2010-01-01</p> <p>... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false <span class="hlt">Mass</span> <span class="hlt">balance</span>. 23.659 Section 23.659 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... Surfaces § 23.659 <span class="hlt">Mass</span> <span class="hlt">balance</span>. The supporting structure and the attachment of concentrated <span class="hlt">mass</span> <span class="hlt">balance</span>...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33A1163R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33A1163R"><span>Modeling and Understanding the <span class="hlt">Mass</span> <span class="hlt">Balance</span> of Himalayan Glaciers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rengaraju, S.; Achutarao, K. M.</p> <p>2017-12-01</p> <p>Changes in glaciers are among the most visible manifestations of a changing climate. Retreating glaciers have significant impacts on global sea-level rise and stream flow of rivers. Modeling the response of glaciers to climate change is important for many reasons including predicting changes in global sea level and water resources. The <span class="hlt">mass</span> <span class="hlt">balance</span> of a glacier provides a robust way of ascertaining whether there has been a net loss or gain of <span class="hlt">ice</span> from the glacier. The <span class="hlt">mass</span> <span class="hlt">balance</span> reflects all of the meteorological forcing of the glacier - from the accumulation of snow and the combined losses from ablation and sublimation. The glaciers in the Himalayan region are considered sensitive to climate change and their fate under climate change is critical to the billions of humans that rely on rivers originating from these glaciers. Owing to complex terrain and harsh climate, Himalayan glaciers have historically been poorly monitored and this makes it harder to understand and predict their fate.In this study we model the observed <span class="hlt">mass</span> <span class="hlt">balance</span> of Himalayan glaciers using the methods of Radic and Hock (2011) and analyze the response to future changes in climate based on the model projections from the Coupled Model Intercomparison Project Phase-5 (CMIP5; Taylor et al., 2012). We make use of available observations of <span class="hlt">mass</span> <span class="hlt">balance</span> from various sources for 14 glaciers across the Himalayas. These glaciers are located across distinct climatic conditions - from the Karakoram and Hindu Kush in the West that are fed by winter precipitation caused by westerly disturbances to the Eastern Himalayas where the summer monsoon provides the bulk of the precipitation. For the historical observed period, we use the ECMWF Re-Analysis (ERA-40) for temperature and VASClimO (GPCC) data at 2.5°x2.5° resolution to calibrate the <span class="hlt">mass</span> <span class="hlt">balance</span> model. We evaluate the CMIP5 model simulations for their fidelity in capturing the distinct climatic conditions across the Himalayas in order to select</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11.1015F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11.1015F"><span>Reconstructions of the 1900-2015 Greenland <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> <span class="hlt">balance</span> using the regional climate MAR model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fettweis, Xavier; Box, Jason E.; Agosta, Cécile; Amory, Charles; Kittel, Christoph; Lang, Charlotte; van As, Dirk; Machguth, Horst; Gallée, Hubert</p> <p>2017-04-01</p> <p>With the aim of studying the recent Greenland <span class="hlt">ice</span> sheet (GrIS) surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) decrease relative to the last century, we have forced the regional climate MAR (Modèle Atmosphérique Régional; version 3.5.2) model with the ERA-Interim (ECMWF Interim Re-Analysis; 1979-2015), ERA-40 (1958-2001), NCEP-NCARv1 (National Centers for Environmental Prediction-National Center for Atmospheric Research Reanalysis version 1; 1948-2015), NCEP-NCARv2 (1979-2015), JRA-55 (Japanese 55-year Reanalysis; 1958-2014), 20CRv2(c) (Twentieth Century Reanalysis version 2; 1900-2014) and ERA-20C (1900-2010) reanalyses. While all these forcing products are reanalyses that are assumed to represent the same climate, they produce significant differences in the MAR-simulated SMB over their common period. A temperature adjustment of +1 °C (respectively -1 °C) was, for example, needed at the MAR boundaries with ERA-20C (20CRv2) reanalysis, given that ERA-20C (20CRv2) is ˜ 1 °C colder (warmer) than ERA-Interim over Greenland during the period 1980-2010. Comparisons with daily PROMICE (Programme for Monitoring of the Greenland <span class="hlt">Ice</span> Sheet) near-surface observations support these adjustments. Comparisons with SMB measurements, <span class="hlt">ice</span> cores and satellite-derived melt extent reveal the most accurate forcing datasets for the simulation of the GrIS SMB to be ERA-Interim and NCEP-NCARv1. However, some biases remain in MAR, suggesting that some improvements are still needed in its cloudiness and radiative schemes as well as in the representation of the bare <span class="hlt">ice</span> albedo. Results from all MAR simulations indicate that (i) the period 1961-1990, commonly chosen as a stable reference period for Greenland SMB and <span class="hlt">ice</span> dynamics, is actually a period of anomalously positive SMB (˜ +40 Gt yr-1) compared to 1900-2010; (ii) SMB has decreased significantly after this reference period due to increasing and unprecedented melt reaching the highest rates in the 120-year common period; (iii) before 1960, both ERA</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRF..122.2324S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRF..122.2324S"><span>Assimilating the <span class="hlt">ICE</span>-6G_C Reconstruction of the Latest Quaternary <span class="hlt">Ice</span> Age Cycle Into Numerical Simulations of the Laurentide and Fennoscandian <span class="hlt">Ice</span> Sheets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stuhne, G. R.; Peltier, W. R.</p> <p>2017-12-01</p> <p>We analyze the effects of nudging 100 kyr numerical simulations of the Laurentide and Fennoscandian <span class="hlt">ice</span> sheets toward the glacial isostatic adjustment-based (GIA-based) <span class="hlt">ICE</span>-6G_C reconstruction of the most recent <span class="hlt">ice</span> age cycle. Starting with the <span class="hlt">ice</span> physics approximations of the PISM <span class="hlt">ice</span> sheet model and the SeaRISE simulation protocols, we incorporate nudging at characteristic time scales, τf, through anomalous <span class="hlt">mass</span> <span class="hlt">balance</span> terms in the <span class="hlt">ice</span> <span class="hlt">mass</span> conservation equation. As should be expected, these <span class="hlt">mass</span> <span class="hlt">balances</span> exhibit physically unrealistic details arising from pure GIA-based reconstruction geometry when nudging is very strong (τf=20 years for North America), while weakly nudged (τf=1,000 years) solutions deviate from <span class="hlt">ICE</span>-6G_C sufficiently to degrade its observational fit quality. For reasonable intermediate time scales (τf=100 years and 200 years), we perturbatively analyze nudged <span class="hlt">ice</span> dynamics as a superposition of "leading-order smoothing" that diffuses <span class="hlt">ICE</span>-6G_C in a physically and observationally consistent manner and "higher-order" deviations arising, for instance, from biases in the time dependence of surface climate boundary conditions. Based upon the relative deviations between respective nudged simulations in which these biases follow surface temperature from <span class="hlt">ice</span> cores and eustatic sea level from marine sediment cores, we compute "<span class="hlt">ice</span> core climate adjustments" that suggest how local paleoclimate observations may be applied to the systematic refinement of <span class="hlt">ICE</span>-6G_C. Our results are consistent with a growing body of evidence suggesting that the geographical origins of Meltwater Pulse 1B (MWP1b) may lie primarily in North America as opposed to Antarctica (as reconstructed in <span class="hlt">ICE</span>-6G_C).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/60028-mass-balance-computation-saguaro','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/60028-mass-balance-computation-saguaro"><span><span class="hlt">Mass</span> <span class="hlt">balance</span> computation in SAGUARO</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Baker, B.L.; Eaton, R.R.</p> <p>1986-12-01</p> <p>This report describes the development of the <span class="hlt">mass</span> <span class="hlt">balance</span> subroutines used with the finite-element code, SAGUARO, which models fluid flow in partially saturated porous media. Derivation of the basic <span class="hlt">mass</span> storage and <span class="hlt">mass</span> flux equations is included. The results of the SAGUARO <span class="hlt">mass-balance</span> subroutine, <span class="hlt">MASS</span>, are shown to compare favorably with the linked results of FEMTRAN. Implementation of the <span class="hlt">MASS</span> option in SAGUARO is described. Instructions for use of the <span class="hlt">MASS</span> option are demonstrated with the three sample cases.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C13G..01F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C13G..01F"><span>Investigating <span class="hlt">ice</span> shelf <span class="hlt">mass</span> loss processes from continuous satellite altimetry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fricker, H. A.</p> <p>2017-12-01</p> <p>The Antarctic <span class="hlt">Ice</span> Sheet continually gains <span class="hlt">mass</span> through snowfall over its large area and, to remain approximately in equilibrium, it sheds most of this excess <span class="hlt">mass</span> through two processes, basal melting and iceberg calving, that both occur in the floating <span class="hlt">ice</span> shelves surrounding the continent. Small amounts of <span class="hlt">mass</span> are also lost by surface melting, which occurs on many <span class="hlt">ice</span> shelves every summer to varying degrees, and has been linked to <span class="hlt">ice</span>-shelf collapse via hydrofracture on <span class="hlt">ice</span> shelves that have been pre-weakened. <span class="hlt">Ice</span> shelves provide mechanical support to `buttress' seaward flow of grounded <span class="hlt">ice</span>, so that <span class="hlt">ice</span>-shelf thinning and retreat result in enhanced <span class="hlt">ice</span> discharge to the ocean. <span class="hlt">Ice</span> shelves are susceptible to changes in forcing from both the atmosphere and the ocean, which both change on a broad range of timescales to modify <span class="hlt">mass</span> gains and losses at the surface and base, and from internal instabilities of the <span class="hlt">ice</span> sheet itself. <span class="hlt">Mass</span> loss from iceberg calving is episodic, with typical intervals between calving events on the order of decades. Since <span class="hlt">ice</span> shelves are so vast, the only viable way to monitor them is with satellites. Here, we discuss results from satellite radar and laser altimeter data from one NASA satellite (ICESat), and four ESA satellites (ERS-1, ERS-2, Envisat, CryoSat-2) to obtain estimates of <span class="hlt">ice</span>-shelf surface height since the early 1990s. The continuous time series show accelerated losses in total Antarctic <span class="hlt">ice</span>-shelf volume from 1994 to 2017, and allow us to investigate the processes causing <span class="hlt">ice</span>-shelf <span class="hlt">mass</span> change. For Larsen C, much of the variability comes from changing atmospheric conditions affecting firn state. In the Amundsen Sea, the rapid thinning is a combination of accelerated ocean-driven thinning and <span class="hlt">ice</span> dynamics. This long-term thinning signal is, however, is strongly modulated by ENSO-driven interannual variability. However, observations of ocean variability around Antarctica are sparse, since these regions are often covered in sea <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860007141','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860007141"><span><span class="hlt">Mass</span> <span class="hlt">balancing</span> of hollow fan blades</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kielb, R. E.</p> <p>1986-01-01</p> <p>A typical section model is used to analytically investigate the effect of <span class="hlt">mass</span> <span class="hlt">balancing</span> as applied to hollow, supersonic fan blades. A procedure to determine the best configuration of an internal <span class="hlt">balancing</span> <span class="hlt">mass</span> to provide flutter alleviation is developed. This procedure is applied to a typical supersonic shroudless fan blade which is unstable in both the solid configuration and when it is hollow with no <span class="hlt">balancing</span> <span class="hlt">mass</span>. The addition of an optimized <span class="hlt">balancing</span> <span class="hlt">mass</span> is shown to stabilize the blade at the design condition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C41F..07P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C41F..07P"><span>Opportunities and Challenges in Enhancing Value of Annual Glacier <span class="hlt">Mass</span> <span class="hlt">Balance</span> Monitoring Examples from Western North America</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pelto, M. S.</p> <p>2017-12-01</p> <p>Alpine glacier <span class="hlt">mass</span> <span class="hlt">balance</span> is the most accurate indicator of glacier response to climate and with retreat of alpine glaciers is one of the clearest signals of global climate change. Completion of long term, representative and homogenous <span class="hlt">mass</span> <span class="hlt">balance</span> field measurement of <span class="hlt">mass</span> <span class="hlt">balance</span>, compiled by WGMS, is a key climate data record. To ensure a monitoring program remains vital and funded local collaboration and connecting the research to local societal impacts is crucial. Working with local partners in collecting and providing the right data is critical whether their interest is in hydropower, irrigation, municipal supply, hazard reduction and/or aquatic ecosystems. The expansion of remote sensing and modeling capability provides both a challenge to continued relevance and an opportunity for field <span class="hlt">mass</span> <span class="hlt">balance</span> programs to expand relevance. In modelling studies of both glacier <span class="hlt">mass</span> <span class="hlt">balance</span> and glacier runoff transient <span class="hlt">balance</span> data has equivalent value with annual <span class="hlt">balance</span> data, for both calibration runs and as an input variable. This increases the utility of mid-season field observations. Remote sensing provides repeat imagery that often identifies the AAR and transient snowline of a glacier. For runoff assessment understanding the specific percent of glacier surface area that is glacier <span class="hlt">ice</span>, older firn, and retained snowpack from the previous winter at frequent intervals during the melt season is vital since each region has a different melt factor. A denser field observation network combined with this imagery can provide additional point <span class="hlt">balance</span> values of ablation that complement the <span class="hlt">mass</span> <span class="hlt">balance</span> record. Periodic measurement of <span class="hlt">mass</span> <span class="hlt">balance</span> at a denser network using GPR, LIDAR, TLS or probing is required to better understand long term point <span class="hlt">balance</span> locations and is important at end of the melt season not just beginning, and has value mid-season for modelling. Applications of each of utility of field <span class="hlt">mass</span> <span class="hlt">balance</span> observations will be illustrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.4898V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.4898V"><span>Reconstruction of past equilibrium line altitude using <span class="hlt">ice</span> extent data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Visnjevic, Vjeran; Herman, Frederic; Podladchikov, Yuri</p> <p>2017-04-01</p> <p>With the end of the Last Glacial Maximum (LGM), about 20 000 years ago, ended the most recent long-lasting cold phase in Earth's history. This last glacial advance left a strong observable imprint on the landscape, such as abandoned moraines, trimlines and other glacial geomorphic features. These features provide a valuable record of past continental climate. In particular, terminal moraines reflect the extent of glaciers and <span class="hlt">ice</span>-caps, which itself reflects past temperature and precipitation conditions. Here we present an inverse approach, based on a Tikhonov regularization, we have recently developed to reconstruct the LGM <span class="hlt">mass</span> <span class="hlt">balance</span> from observed <span class="hlt">ice</span> extent data. The <span class="hlt">ice</span> flow model is developed using the shallow <span class="hlt">ice</span> approximation and solved explicitly using Graphical Processing Units (GPU). The <span class="hlt">mass</span> <span class="hlt">balance</span> field, b, is the constrained variable defined by the <span class="hlt">ice</span> surface S, <span class="hlt">balance</span> rate β and the spatially variable equilibrium line altitude field (ELA): b = min (β ṡ(S(x,y)- ELA (x,y)),c). (1) where c is a maximum accumulation rate. We show that such a <span class="hlt">mass</span> <span class="hlt">balance</span>, and thus the spatially variable ELA field, can be inferred from the observed past <span class="hlt">ice</span> extent and <span class="hlt">ice</span> thickness at high resolution and very efficiently. The GPU implementation allows us solve one 1024x1024 grid points forward model run under 0.5s, which significantly reduces the time needed for our inverse method to converge. We start with synthetic test to demonstrate the method. We then apply the method to LGM <span class="hlt">ice</span> extents of South Island of New Zealand, the Patagonian Andes, where we can see a clear influence of Westerlies on the ELA, and the European Alps. These examples show that the method is capable of constraining spatial variations in <span class="hlt">mass</span> <span class="hlt">balance</span> at the scale of a mountain range, and provide us with information on past continental climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2014-title14-vol1/pdf/CFR-2014-title14-vol1-sec29-659.pdf','CFR2014'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2014-title14-vol1/pdf/CFR-2014-title14-vol1-sec29-659.pdf"><span>14 CFR 29.659 - <span class="hlt">Mass</span> <span class="hlt">balance</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2014&page.go=Go">Code of Federal Regulations, 2014 CFR</a></p> <p></p> <p>2014-01-01</p> <p>... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 <span class="hlt">Mass</span> <span class="hlt">balance</span>. (a) The rotor and blades must be <span class="hlt">mass</span> <span class="hlt">balanced</span> as necessary to— (1) Prevent excessive vibration; and (2) Prevent... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false <span class="hlt">Mass</span> <span class="hlt">balance</span>. 29.659 Section 29.659...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2014-title14-vol1/pdf/CFR-2014-title14-vol1-sec27-659.pdf','CFR2014'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2014-title14-vol1/pdf/CFR-2014-title14-vol1-sec27-659.pdf"><span>14 CFR 27.659 - <span class="hlt">Mass</span> <span class="hlt">balance</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2014&page.go=Go">Code of Federal Regulations, 2014 CFR</a></p> <p></p> <p>2014-01-01</p> <p>... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 <span class="hlt">Mass</span> <span class="hlt">balance</span>. (a) The rotors and blades must be <span class="hlt">mass</span> <span class="hlt">balanced</span> as necessary to— (1) Prevent excessive vibration; and (2) Prevent... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false <span class="hlt">Mass</span> <span class="hlt">balance</span>. 27.659 Section 27.659...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2012-title14-vol1/pdf/CFR-2012-title14-vol1-sec29-659.pdf','CFR2012'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2012-title14-vol1/pdf/CFR-2012-title14-vol1-sec29-659.pdf"><span>14 CFR 29.659 - <span class="hlt">Mass</span> <span class="hlt">balance</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2012&page.go=Go">Code of Federal Regulations, 2012 CFR</a></p> <p></p> <p>2012-01-01</p> <p>... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 <span class="hlt">Mass</span> <span class="hlt">balance</span>. (a) The rotor and blades must be <span class="hlt">mass</span> <span class="hlt">balanced</span> as necessary to— (1) Prevent excessive vibration; and (2) Prevent... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false <span class="hlt">Mass</span> <span class="hlt">balance</span>. 29.659 Section 29.659...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2013-title14-vol1/pdf/CFR-2013-title14-vol1-sec27-659.pdf','CFR2013'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2013-title14-vol1/pdf/CFR-2013-title14-vol1-sec27-659.pdf"><span>14 CFR 27.659 - <span class="hlt">Mass</span> <span class="hlt">balance</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2013&page.go=Go">Code of Federal Regulations, 2013 CFR</a></p> <p></p> <p>2013-01-01</p> <p>... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 <span class="hlt">Mass</span> <span class="hlt">balance</span>. (a) The rotors and blades must be <span class="hlt">mass</span> <span class="hlt">balanced</span> as necessary to— (1) Prevent excessive vibration; and (2) Prevent... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false <span class="hlt">Mass</span> <span class="hlt">balance</span>. 27.659 Section 27.659...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2012-title14-vol1/pdf/CFR-2012-title14-vol1-sec27-659.pdf','CFR2012'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2012-title14-vol1/pdf/CFR-2012-title14-vol1-sec27-659.pdf"><span>14 CFR 27.659 - <span class="hlt">Mass</span> <span class="hlt">balance</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2012&page.go=Go">Code of Federal Regulations, 2012 CFR</a></p> <p></p> <p>2012-01-01</p> <p>... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 <span class="hlt">Mass</span> <span class="hlt">balance</span>. (a) The rotors and blades must be <span class="hlt">mass</span> <span class="hlt">balanced</span> as necessary to— (1) Prevent excessive vibration; and (2) Prevent... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false <span class="hlt">Mass</span> <span class="hlt">balance</span>. 27.659 Section 27.659...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2013-title14-vol1/pdf/CFR-2013-title14-vol1-sec29-659.pdf','CFR2013'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2013-title14-vol1/pdf/CFR-2013-title14-vol1-sec29-659.pdf"><span>14 CFR 29.659 - <span class="hlt">Mass</span> <span class="hlt">balance</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2013&page.go=Go">Code of Federal Regulations, 2013 CFR</a></p> <p></p> <p>2013-01-01</p> <p>... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 <span class="hlt">Mass</span> <span class="hlt">balance</span>. (a) The rotor and blades must be <span class="hlt">mass</span> <span class="hlt">balanced</span> as necessary to— (1) Prevent excessive vibration; and (2) Prevent... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false <span class="hlt">Mass</span> <span class="hlt">balance</span>. 29.659 Section 29.659...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007GPC....59...10L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007GPC....59...10L"><span>20 years of <span class="hlt">mass</span> <span class="hlt">balances</span> on the Piloto glacier, Las Cuevas river basin, Mendoza, Argentina</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leiva, J. C.; Cabrera, G. A.; Lenzano, L. E.</p> <p>2007-10-01</p> <p>Climatic changes of the 20th century have altered the water cycle in the Andean basins of central Argentina. The most visible change is seen in the mountain glaciers, with loss of part of their <span class="hlt">mass</span> due to decreasing thickness and a substantial recession in the last 100 years. This paper briefly describes the results of glacier <span class="hlt">mass</span> <span class="hlt">balance</span> research since 1979 in the Piloto Glacier at the Cajón del Rubio, in the headwaters of Las Cuevas River, presenting new results for the period 1997-2003. Very large interannual variability of net annual specific <span class="hlt">balance</span> is evident, due largely to variations in winter snow accumulation, with a maximum net annual value of + 151 cm w.e. and a minimum value of - 230 cm w.e. Wet El Niño years are normally associated with positive net annual <span class="hlt">balances</span>, while dry La Niña years generally result in negative <span class="hlt">balances</span>. Within the 24-year period, 67% of the years show negative net annual specific <span class="hlt">balances</span>, with a cumulative <span class="hlt">mass</span> <span class="hlt">balance</span> loss of - 10.50 m water equivalent (w.e.). Except for exceptions normally related to El Niño events, a general decreasing trend of winter snow accumulation is evident in the record, particularly after 1992, which has a strong effect in the overall negative <span class="hlt">mass</span> <span class="hlt">balance</span> values. The glacier contribution to Las Cuevas River runoff is analysed based on the Punta de Vacas River gauge station for a hypothetical year without snow precipitation (YWSP), when the snowmelt component is zero. Extremely dry years similar to a YWSP have occurred in 1968-1969, 1969-1970 and 1996-1997. The Punta de Vacas gauge station is located 62 km downstream from Piloto Glacier, and the basin contains 3.0% of uncovered glacier <span class="hlt">ice</span> and 3.7% of debris-covered <span class="hlt">ice</span>. The total glacier contribution to Las Cuevas River discharge is calculated as 82 ± 8% during extremely dry years. If glacier wastage continues at the present trend as observed during the last 2 decades, it will severely affect the water resources in the arid central Andes of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2011-title14-vol1/pdf/CFR-2011-title14-vol1-sec29-659.pdf','CFR2011'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2011-title14-vol1/pdf/CFR-2011-title14-vol1-sec29-659.pdf"><span>14 CFR 29.659 - <span class="hlt">Mass</span> <span class="hlt">balance</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2011&page.go=Go">Code of Federal Regulations, 2011 CFR</a></p> <p></p> <p>2011-01-01</p> <p>... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false <span class="hlt">Mass</span> <span class="hlt">balance</span>. 29.659 Section 29.659... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 <span class="hlt">Mass</span> <span class="hlt">balance</span>. (a) The rotor... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the <span class="hlt">mass</span> <span class="hlt">balance</span>...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2010-title14-vol1/pdf/CFR-2010-title14-vol1-sec27-659.pdf','CFR'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2010-title14-vol1/pdf/CFR-2010-title14-vol1-sec27-659.pdf"><span>14 CFR 27.659 - <span class="hlt">Mass</span> <span class="hlt">balance</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2010&page.go=Go">Code of Federal Regulations, 2010 CFR</a></p> <p></p> <p>2010-01-01</p> <p>... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false <span class="hlt">Mass</span> <span class="hlt">balance</span>. 27.659 Section 27.659... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 <span class="hlt">Mass</span> <span class="hlt">balance</span>. (a) The rotors... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the <span class="hlt">mass</span> <span class="hlt">balance</span>...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2011-title14-vol1/pdf/CFR-2011-title14-vol1-sec27-659.pdf','CFR2011'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2011-title14-vol1/pdf/CFR-2011-title14-vol1-sec27-659.pdf"><span>14 CFR 27.659 - <span class="hlt">Mass</span> <span class="hlt">balance</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2011&page.go=Go">Code of Federal Regulations, 2011 CFR</a></p> <p></p> <p>2011-01-01</p> <p>... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false <span class="hlt">Mass</span> <span class="hlt">balance</span>. 27.659 Section 27.659... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 <span class="hlt">Mass</span> <span class="hlt">balance</span>. (a) The rotors... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the <span class="hlt">mass</span> <span class="hlt">balance</span>...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2010-title14-vol1/pdf/CFR-2010-title14-vol1-sec29-659.pdf','CFR'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2010-title14-vol1/pdf/CFR-2010-title14-vol1-sec29-659.pdf"><span>14 CFR 29.659 - <span class="hlt">Mass</span> <span class="hlt">balance</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2010&page.go=Go">Code of Federal Regulations, 2010 CFR</a></p> <p></p> <p>2010-01-01</p> <p>... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false <span class="hlt">Mass</span> <span class="hlt">balance</span>. 29.659 Section 29.659... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 <span class="hlt">Mass</span> <span class="hlt">balance</span>. (a) The rotor... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the <span class="hlt">mass</span> <span class="hlt">balance</span>...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AGUFM.C11B0806H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFM.C11B0806H"><span>California's Snow Gun and its implications for <span class="hlt">mass</span> <span class="hlt">balance</span> predictions under greenhouse warming</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Howat, I.; Snyder, M.; Tulaczyk, S.; Sloan, L.</p> <p>2003-12-01</p> <p>Precipitation has received limited treatment in glacier and snowpack <span class="hlt">mass</span> <span class="hlt">balance</span> models, largely due to the poor resolution and confidence of precipitation predictions relative to temperature predictions derived from atmospheric models. Most snow and glacier <span class="hlt">mass</span> <span class="hlt">balance</span> models rely on statistical or lapse rate-based downscaling of general or regional circulation models (GCM's and RCM's), essentially decoupling sub-grid scale, orographically-driven evolution of atmospheric heat and moisture. Such models invariably predict large losses in the snow and <span class="hlt">ice</span> volume under greenhouse warming. However, positive trends in the <span class="hlt">mass</span> <span class="hlt">balance</span> of glaciers in some warming maritime climates, as well as at high elevations of the Greenland <span class="hlt">Ice</span> Sheet, suggest that increased precipitation may play an important role in snow- and glacier-climate interactions. Here, we present a half century of April snowpack data from the Sierra Nevada and Cascade mountains of California, USA. This high-density network of snow-course data indicates that a gain in winter snow accumulation at higher elevations has compensated loss in snow volume at lower elevations by over 50% and has led to glacier expansion on Mt. Shasta. These trends are concurrent with a region-wide increase in winter temperatures up to 2° C. They result from the orographic lifting and saturation of warmer, more humid air leading to increased precipitation at higher elevations. Previous studies have invoked such a "Snow Gun" effect to explain contemporaneous records of Tertiary ocean warming and rapid glacial expansion. A climatological context of the California's "snow gun" effect is elucidated by correlation between the elevation distribution of April SWE observations and the phase of the Pacific Decadal Oscillation and the El Nino Southern Oscillation, both controlling the heat and moisture delivered to the U.S. Pacific coast. The existence of a significant "Snow Gun" effect presents two challenges to snow and glacier <span class="hlt">mass</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1913667S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1913667S"><span>The importance of accurate glacier albedo for estimates of surface <span class="hlt">mass</span> <span class="hlt">balance</span> on Vatnajökull: Evaluating the surface energy budget in a Regional Climate Model with automatic weather station observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steffensen Schmidt, Louise; Aðalgeirsdóttir, Guðfinna; Guðmundsson, Sverrir; Langen, Peter L.; Pálsson, Finnur; Mottram, Ruth; Gascoin, Simon; Björnsson, Helgi</p> <p>2017-04-01</p> <p>The evolution of the surface <span class="hlt">mass</span> <span class="hlt">balance</span> of Vatnajökull <span class="hlt">ice</span> cap, Iceland, from 1981 to the present day is estimated by using the Regional Climate Model HIRHAM5 to simulate the surface climate. A new albedo parametrization is used for the simulation, which describes the albedo with an exponential decay with time. In addition, it utilizes a new background map of the <span class="hlt">ice</span> albedo created from MODIS data. The simulation is validated against observed daily values of weather parameters from five Automatic Weather Stations (AWSs) from 2001-2014, as well as <span class="hlt">mass</span> <span class="hlt">balance</span> measurements from 1995-2014. The modelled albedo is overestimated at the AWS sites in the ablation zone, which we attribute to an overestimation of the thickness of the snow layer and the model not accounting for dust and ash deposition during dust storms and volcanic eruptions. A comparison with the specific summer, winter, and annual <span class="hlt">mass</span> <span class="hlt">balance</span> for all Vatnajökull from 1995-2014 shows a good overall fit during the summer, with the model underestimating the <span class="hlt">balance</span> by only 0.04 m w. eq. on average. The winter <span class="hlt">balance</span>, on the other hand, is overestimated by 0.5 m w. eq. on average, mostly due to an overestimation of the precipitation at the highest areas of the <span class="hlt">ice</span> cap. A simple correction of the accumulation at these points reduced the error to 0.15 m w. eq. The model captures the evolution of the specific <span class="hlt">mass</span> <span class="hlt">balance</span> well, for example it captures an observed shift in the <span class="hlt">balance</span> in the mid-1990s, which gives us confidence in the results for the entire model run. Our results show the importance of bare <span class="hlt">ice</span> albedo for modelled <span class="hlt">mass</span> <span class="hlt">balance</span> and that processes not currently accounted for in RCMs, such as dust storms, are an important source of uncertainty in estimates of the snow melt rate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170002775&hterms=inversion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dinversion','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170002775&hterms=inversion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dinversion"><span>Spatial and Temporal Antarctic <span class="hlt">Ice</span> Sheet <span class="hlt">Mass</span> Trends, Glacio-Isostatic Adjustment, and Surface Processes from a Joint Inversion of Satellite Altimeter, Gravity, and GPS Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Martin-Espanol, Alba; Zammit-Mangion, Andrew; Clarke, Peter J.; Flament, Thomas; Helm, Veit; King, Matt A.; Luthcke, Scott B.; Petrie, Elizabeth; Remy, Frederique; Schon, Nana; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20170002775'); toggleEditAbsImage('author_20170002775_show'); toggleEditAbsImage('author_20170002775_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20170002775_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20170002775_hide"></p> <p>2016-01-01</p> <p>We present spatiotemporal <span class="hlt">mass</span> <span class="hlt">balance</span> trends for the Antarctic <span class="hlt">Ice</span> Sheet from a statistical inversion of satellite altimetry, gravimetry, and elastic-corrected GPS data for the period 2003-2013. Our method simultaneously determines annual trends in <span class="hlt">ice</span> dynamics, surface <span class="hlt">mass</span> <span class="hlt">balance</span> anomalies, and a time-invariant solution for glacio-isostatic adjustment while remaining largely independent of forward models. We establish that over the period 2003-2013, Antarctica has been losing <span class="hlt">mass</span> at a rateof -84 +/- 22 Gt per yr, with a sustained negative mean trend of dynamic imbalance of -111 +/- 13 Gt per yr. West Antarctica is the largest contributor with -112 +/- 10 Gt per yr, mainly triggered by high thinning rates of glaciers draining into the Amundsen Sea Embayment. The Antarctic Peninsula has experienced a dramatic increase in <span class="hlt">mass</span> loss in the last decade, with a mean rate of -28 +/- 7 Gt per yr and significantly higher values for the most recent years following the destabilization of the Southern Antarctic Peninsula around 2010. The total <span class="hlt">mass</span> loss is partly compensated by a significant <span class="hlt">mass</span> gain of 56 +/- 18 Gt per yr in East Antarctica due to a positive trend of surface <span class="hlt">mass</span> <span class="hlt">balance</span> anomalies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.water.usgs.gov/ofr2004-1069/','USGSPUBS'); return false;" href="http://pubs.water.usgs.gov/ofr2004-1069/"><span>A 30-year record of surface <span class="hlt">mass</span> <span class="hlt">balance</span> (1966-95) and motion and surface altitude (1975-95) at Wolverine Glacier, Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Mayo, Lawrence R.; Trabant, Dennis C.; March, Rod S.</p> <p>2004-01-01</p> <p>Scientific measurements at Wolverine Glacier, on the Kenai Peninsula in south-central Alaska, began in April 1966. At three long-term sites in the research basin, the measurements included snow depth, snow density, heights of the glacier surface and stratigraphic summer surfaces on stakes, and identification of the surface materials. Calculations of the <span class="hlt">mass</span> <span class="hlt">balance</span> of the surface strata-snow, new firn, superimposed <span class="hlt">ice</span>, and old firn and <span class="hlt">ice</span> <span class="hlt">mass</span> at each site were based on these measurements. Calculations of fixed-date annual <span class="hlt">mass</span> <span class="hlt">balances</span> for each hydrologic year (October 1 to September 30), as well as net <span class="hlt">balances</span> and the dates of minimum net <span class="hlt">balance</span> measured between time-transgressive summer surfaces on the glacier, were made on the basis of the strata <span class="hlt">balances</span> augmented by air temperature and precipitation recorded in the basin. From 1966 through 1995, the average annual <span class="hlt">balance</span> at site A (590 meters altitude) was -4.06 meters water equivalent; at site B (1,070 meters altitude), was -0.90 meters water equivalent; and at site C (1,290 meters altitude), was +1.45 meters water equivalent. Geodetic determination of displacements of the <span class="hlt">mass</span> <span class="hlt">balance</span> stake, and glacier surface altitudes was added to the data set in 1975 to detect the glacier motion responses to variable climate and <span class="hlt">mass</span> <span class="hlt">balance</span> conditions. The average surface speed from 1975 to 1996 was 50.0 meters per year at site A, 83.7 meters per year at site B, and 37.2 meters per year at site C. The average surface altitudes were 594 meters at site A, 1,069 meters at site B, and 1,293 meters at site C; the glacier surface altitudes rose and fell over a range of 19.4 meters at site A, 14.1 meters at site B, and 13.2 meters at site C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/971306','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/971306"><span>Greenland <span class="hlt">ice</span> sheet surface <span class="hlt">mass-balance</span> modeling in a 131-year perspective, 1950-2080</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Mernild, Sebastian Haugard; Liston, Glen; Hiemstra, Christopher</p> <p>2009-01-01</p> <p>Fluctuations in the Greenland <span class="hlt">Ice</span> Sheet (GrIS) surface <span class="hlt">mass-balance</span> (SMB) and freshwater influx to the surrounding oceans closely follow climate fluctuations and are of considerable importance to the global eustatic sea level rise. SnowModel, a state-of-the-art snow-evolution modeling system, was used to simulate variations in the GrIS melt extent, surface water <span class="hlt">balance</span> components, changes in SMB, and freshwater influx to the ocean. The simulations are based on the IPCC scenario AlB modeled by the HIRHAM4 RCM (using boundary conditions from ECHAM5 AOGCM) from 1950 through 2080. In-situ meteorological station (GC-Net and WMO DMI) observations from inside and outside the GrISmore » were used to validate and correct RCM output data before it was used as input for SnowModel. Satellite observations and independent SMB studies were used to validate the SnowModel output and confirm the model's robustness. We simulated a {approx}90% increase in end-of-summer surface melt extent (0.483 x 10{sup 6} km{sup 2}) from 1950 to 2080, and a melt index (above 2,000-m elevation) increase of 138% (1.96 x 10{sup 6} km{sup 2} x days). The greatest difference in melt extent occured in the southern part of the GrIS, and the greatest changes in the number of melt days was seen in the eastern part of the GrIS ({approx}50-70%) and was lowest in the west ({approx}20-30%). The rate of SMB loss, largely tied to changes in ablation processes, lead to an enhanced average loss of 331 km{sup 3} from 1950 to 2080, an average 5MB level of -99 km{sup 3} for the period 2070-2080. GrIS surface freshwater runoff yielded an eustatic rise in sea level from 0.8 {+-} 0.1 (1950-1959) to 1.9 {+-} 0.1 mm (2070-2080) sea level equivalent (SLE) y{sup -1}. The accumulated GrIS freshwater runoff contribution from surface melting equaled 160 mm SLE from 1950 through 2080.« less</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1915674M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1915674M"><span>The future of the Devon <span class="hlt">Ice</span> cap: results from climate and <span class="hlt">ice</span> dynamics modelling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mottram, Ruth; Rodehacke, Christian; Boberg, Fredrik</p> <p>2017-04-01</p> <p>The Devon <span class="hlt">Ice</span> Cap is an example of a relatively well monitored small <span class="hlt">ice</span> cap in the Canadian Arctic. Close to Greenland, it shows a similar surface <span class="hlt">mass</span> <span class="hlt">balance</span> signal to glaciers in western Greenland. Here we use high resolution (5km) simulations from HIRHAM5 to drive the PISM glacier model in order to model the present day and future prospects of this small Arctic <span class="hlt">ice</span> cap. Observational data from the Devon <span class="hlt">Ice</span> Cap in Arctic Canada is used to evaluate the surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) data output from the HIRHAM5 model for simulations forced with the ERA-Interim climate reanalysis data and the historical emissions scenario run by the EC-Earth global climate model. The RCP8.5 scenario simulated by EC-Earth is also downscaled by HIRHAM5 and this output is used to force the PISM model to simulate the likely future evolution of the Devon <span class="hlt">Ice</span> Cap under a warming climate. We find that the Devon <span class="hlt">Ice</span> Cap is likely to continue its present day retreat, though in the future increased precipitation partly offsets the enhanced melt rates caused by climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.water.usgs.gov/wri024165','USGSPUBS'); return false;" href="http://pubs.water.usgs.gov/wri024165"><span>Water, <span class="hlt">ice</span>, and meteorological measurements at South Cascade Glacier, Washington, 2000-01 <span class="hlt">balance</span> years</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Krimmel, Robert M.</p> <p>2002-01-01</p> <p>Winter snow accumulation and summer snow, firn, and <span class="hlt">ice</span> melt were measured at South Cascade Glacier, Washington, to determine the winter and net <span class="hlt">balances</span> for the 2000 and 2001 <span class="hlt">balance</span> years. In 2000, the winter <span class="hlt">balance</span>, averaged over the glacier, was 3.32 meters, and the net <span class="hlt">balance</span> was 0.38 meters. The winter <span class="hlt">balance</span> was the ninth highest since the record began in 1959. The net <span class="hlt">balance</span> was greater than 33 of the 41 years since 1959. In 2001, the winter <span class="hlt">balance</span> was 1.90 meters, and net <span class="hlt">balance</span> was -1.57 meters. The winter <span class="hlt">balance</span> was lower than all but 4 years since 1959, and the net <span class="hlt">balance</span> was more negative than all but 5 other years. Runoff was measured from the glacier basin and an adjacent non-glacierized basin. Air temperature, precipitation, humidity, wind speed and solar radiation were measured nearby. <span class="hlt">Ice</span> displacements were measured for the 1998-2001 period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..4411463S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..4411463S"><span>Algae Drive Enhanced Darkening of Bare <span class="hlt">Ice</span> on the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stibal, Marek; Box, Jason E.; Cameron, Karen A.; Langen, Peter L.; Yallop, Marian L.; Mottram, Ruth H.; Khan, Alia L.; Molotch, Noah P.; Chrismas, Nathan A. M.; Calı Quaglia, Filippo; Remias, Daniel; Smeets, C. J. P. Paul; van den Broeke, Michiel R.; Ryan, Jonathan C.; Hubbard, Alun; Tranter, Martyn; van As, Dirk; Ahlstrøm, Andreas P.</p> <p>2017-11-01</p> <p>Surface ablation of the Greenland <span class="hlt">ice</span> sheet is amplified by surface darkening caused by light-absorbing impurities such as mineral dust, black carbon, and pigmented microbial cells. We present the first quantitative assessment of the microbial contribution to the <span class="hlt">ice</span> sheet surface darkening, based on field measurements of surface reflectance and concentrations of light-absorbing impurities, including pigmented algae, during the 2014 melt season in the southwestern part of the <span class="hlt">ice</span> sheet. The impact of algae on bare <span class="hlt">ice</span> darkening in the study area was greater than that of nonalgal impurities and yielded a net albedo reduction of 0.038 ± 0.0035 for each algal population doubling. We argue that algal growth is a crucial control of bare <span class="hlt">ice</span> darkening, and incorporating the algal darkening effect will improve <span class="hlt">mass</span> <span class="hlt">balance</span> and sea level projections of the Greenland <span class="hlt">ice</span> sheet and <span class="hlt">ice</span> <span class="hlt">masses</span> elsewhere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMGC21A0945G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMGC21A0945G"><span>Barrow real-time sea <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> data: ingestion, processing, dissemination and archival of multi-sensor data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grimes, J.; Mahoney, A. R.; Heinrichs, T. A.; Eicken, H.</p> <p>2012-12-01</p> <p>Sensor data can be highly variable in nature and also varied depending on the physical quantity being observed, sensor hardware and sampling parameters. The sea <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> site (MBS) operated in Barrow by the University of Alaska Fairbanks (http://seaice.alaska.edu/gi/observatories/barrow_sealevel) is a multisensor platform consisting of a thermistor string, air and water temperature sensors, acoustic altimeters above and below the <span class="hlt">ice</span> and a humidity sensor. Each sensor has a unique specification and configuration. The data from multiple sensors are combined to generate sea <span class="hlt">ice</span> data products. For example, <span class="hlt">ice</span> thickness is calculated from the positions of the upper and lower <span class="hlt">ice</span> surfaces, which are determined using data from downward-looking and upward-looking acoustic altimeters above and below the <span class="hlt">ice</span>, respectively. As a data clearinghouse, the Geographic Information Network of Alaska (GINA) processes real time data from many sources, including the Barrow MBS. Doing so requires a system that is easy to use, yet also offers the flexibility to handle data from multisensor observing platforms. In the case of the Barrow MBS, the metadata system needs to accommodate the addition of new and retirement of old sensors from year to year as well as instrument configuration changes caused by, for example, spring melt or inquisitive polar bears. We also require ease of use for both administrators and end users. Here we present the data and processing steps of using sensor data system powered by the NoSQL storage engine, MongoDB. The system has been developed to ingest, process, disseminate and archive data from the Barrow MBS. Storing sensor data in a generalized format, from many different sources, is a challenging task, especially for traditional SQL databases with a set schema. MongoDB is a NoSQL (not only SQL) database that does not require a fixed schema. There are several advantages using this model over the traditional relational database management system (RDBMS</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.3773S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.3773S"><span>A better GRACE solution for improving the regional Greenland <span class="hlt">mass</span> <span class="hlt">balance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schrama, E.; Xu, Z.</p> <p>2012-04-01</p> <p>In most GRACE based researches, a variety of smoothing methods is employed to remove alternating bands of positive and negative stripes stretching in the north-south direction. Many studies have suggested to smooth the GRACE maps, on which <span class="hlt">mass</span> variations are represented as equivalent water height (EWH). Such maps are capable of exposing the redistribution of earth surface <span class="hlt">mass</span> over time. In Greenland the shrinking of the <span class="hlt">ice</span> cap becomes significant in the last decade. Our present study confirms that the dominating melting trends are in the east and southeast coastal zones, however, the smoothed signals along the coastline in these areas do not represent the original but averaged measurements from GRACE satellites which means the signal strength indicating that negative <span class="hlt">mass</span> variations are mixed with some positive signals that are very close to this area. An exact identification of the topographic edge is not possible and visually the EWH maps appear to be blurred. To improve this, we firstly used spherical harmonic coefficients of GRACE level-2 data from CSR-RL04 and produced a smoothed EWH map. Empirical Orthogonal Functions(EOF)/Principal Component Analysis(PCA) have been introduced as well, in order to extract the melting information associated with the recent warming climate. Next, the Greenland area is redefined by 16 basins and the corresponding melting zones are quantified respectively. Least Squares methods are invoked to interpolate the <span class="hlt">mass</span> distribution function on each basin. In this way we are able to estimate more accurately regional <span class="hlt">ice</span> melting rate and we sharpen the EWH map. After comparing our results with a hydrological model the combination SMB - D is established which contains the surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) and <span class="hlt">ice</span>-discharge (D). A general agreement can be reached and it turns out this method is capable to enhance our understanding of the shrinking global cryosphere</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.amap.no/documents/doc/snow-water-ice-and-permafrost-in-the-arctic-swipa-climate-change-and-the-cryosphere/743','USGSPUBS'); return false;" href="http://www.amap.no/documents/doc/snow-water-ice-and-permafrost-in-the-arctic-swipa-climate-change-and-the-cryosphere/743"><span>Mountain Glaciers and <span class="hlt">Ice</span> Caps</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ananichheva, Maria; Arendt, Anthony; Hagen, Jon-Ove; Hock, Regine; Josberger, Edward G.; Moore, R. Dan; Pfeffer, William Tad; Wolken, Gabriel J.</p> <p>2011-01-01</p> <p>Projections of future rates of <span class="hlt">mass</span> loss from mountain glaciers and <span class="hlt">ice</span> caps in the Arctic focus primarily on projections of changes in the surface <span class="hlt">mass</span> <span class="hlt">balance</span>. Current models are not yet capable of making realistic forecasts of changes in losses by calving. Surface <span class="hlt">mass</span> <span class="hlt">balance</span> models are forced with downscaled output from climate models driven by forcing scenarios that make assumptions about the future rate of growth of atmospheric greenhouse gas concentrations. Thus, <span class="hlt">mass</span> loss projections vary considerably, depending on the forcing scenario used and the climate model from which climate projections are derived. A new study in which a surface <span class="hlt">mass</span> <span class="hlt">balance</span> model is driven by output from ten general circulation models (GCMs) forced by the IPCC (Intergovernmental Panel on Climate Change) A1B emissions scenario yields estimates of total <span class="hlt">mass</span> loss of between 51 and 136 mm sea-level equivalent (SLE) (or 13% to 36% of current glacier volume) by 2100. This implies that there will still be substantial glacier <span class="hlt">mass</span> in the Arctic in 2100 and that Arctic mountain glaciers and <span class="hlt">ice</span> caps will continue to influence global sea-level change well into the 22nd century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10.1279F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10.1279F"><span>Application and validation of long-range terrestrial laser scanning to monitor the <span class="hlt">mass</span> <span class="hlt">balance</span> of very small glaciers in the Swiss Alps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fischer, Mauro; Huss, Matthias; Kummert, Mario; Hoelzle, Martin</p> <p>2016-06-01</p> <p>Due to the relative lack of empirical field data, the response of very small glaciers (here defined as being smaller than 0.5 km2) to current atmospheric warming is not fully understood yet. Investigating their <span class="hlt">mass</span> <span class="hlt">balance</span>, e.g. using the direct glaciological method, is a prerequisite to fill this knowledge gap. Terrestrial laser scanning (TLS) techniques operating in the near infrared range can be applied for the creation of repeated high-resolution digital elevation models and consecutive derivation of annual geodetic <span class="hlt">mass</span> <span class="hlt">balances</span> of very small glaciers. This method is promising, as laborious and potentially dangerous field measurements as well as the inter- and extrapolation of point measurements can be circumvented. However, it still needs to be validated. Here, we present TLS-derived annual surface elevation and geodetic <span class="hlt">mass</span> changes for five very small glaciers in Switzerland (Glacier de Prapio, Glacier du Sex Rouge, St. Annafirn, Schwarzbachfirn, and Pizolgletscher) and two consecutive years (2013/14-2014/15). The scans were acquired with a long-range Riegl -6000 especially designed for surveying snow- and <span class="hlt">ice</span>-covered terrain. Zonally variable conversion factors for firn and bare <span class="hlt">ice</span> surfaces were applied to convert geodetic volume to <span class="hlt">mass</span> changes. We compare the geodetic results to direct glaciological <span class="hlt">mass</span> <span class="hlt">balance</span> measurements coinciding with the TLS surveys and assess the uncertainties and errors included in both methods. Average glacier-wide <span class="hlt">mass</span> <span class="hlt">balances</span> were negative in both years, showing stronger <span class="hlt">mass</span> losses in 2014/15 (-1.65 m w.e.) compared to 2013/14 (-0.59 m w.e.). Geodetic <span class="hlt">mass</span> <span class="hlt">balances</span> were slightly less negative but in close agreement with the direct glaciological ones (R2 = 0.91). Due to the dense in situ measurements, the uncertainties in the direct glaciological <span class="hlt">mass</span> <span class="hlt">balances</span> were small compared to the majority of measured glaciers worldwide (±0.09 m w.e. yr-1 on average), and similar to uncertainties in the TLS-derived geodetic <span class="hlt">mass</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.C41D..02R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.C41D..02R"><span><span class="hlt">Ice</span>-shelf melting around Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rignot, E.; Jacobs, S.</p> <p>2008-12-01</p> <p>The traditional view on the <span class="hlt">mass</span> <span class="hlt">balance</span> of Antarctic <span class="hlt">ice</span> shelves is that they loose <span class="hlt">mass</span> principally from iceberg calving with bottom melting a much lower contributing factor. Because <span class="hlt">ice</span> shelves are now known to play a fundamental role in <span class="hlt">ice</span> sheet evolution, it is important to re-evaluate their wastage processes from a circumpolar perspective using a combination of remote sensing techniques. We present area average rates deduced from grounding line discharge, snow accumulation, firn depth correction and <span class="hlt">ice</span> shelf topography. We find that <span class="hlt">ice</span> shelf melting accounts for roughly half of <span class="hlt">ice</span>-shelf ablation, with a total melt water production of 1027 Gt/yr. The attrition fraction due to in-situ melting varies from 9 to 90 percent around Antarctica. High melt producers include the Ronne, Ross, Getz, Totten, Amery, George VI, Pine Island, Abbot, Dotson/Crosson, Shackleton, Thwaites and Moscow University <span class="hlt">Ice</span> Shelves. Low producers include the Larsen C, Princess Astrid and Ragnhild coast, Fimbul, Brunt and Filchner. Correlation between melt water production and grounding line discharge is low (R2 = 0.65). Correlation with thermal ocean forcing from the ocean are highest in the northern parts of West Antarctica where regressions yield R2 of 0.93-0.97. Melt rates in the Amundsen Sea exhibit a quadratic sensitivity to thermal ocean forcing. We conclude that <span class="hlt">ice</span> shelf melting plays a dominant role in <span class="hlt">ice</span> shelf <span class="hlt">mass</span> <span class="hlt">balance</span>, with a potential to change rapidly in response to altered ocean heat transport onto the Antarctic continental shelf.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C53C0799H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C53C0799H"><span>Validation of Modelled <span class="hlt">Ice</span> Dynamics of the Greenland <span class="hlt">Ice</span> Sheet using Historical Forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoffman, M. J.; Price, S. F.; Howat, I. M.; Bonin, J. A.; Chambers, D. P.; Tezaur, I.; Kennedy, J. H.; Lenaerts, J.; Lipscomb, W. H.; Neumann, T.; Nowicki, S.; Perego, M.; Saba, J. L.; Salinger, A.; Guerber, J. R.</p> <p>2015-12-01</p> <p>Although <span class="hlt">ice</span> sheet models are used for sea level rise projections, the degree to which these models have been validated by observations is fairly limited, due in part to the limited duration of the satellite observation era and the long adjustment time scales of <span class="hlt">ice</span> sheets. Here we describe a validation framework for the Greenland <span class="hlt">Ice</span> Sheet applied to the Community <span class="hlt">Ice</span> Sheet Model by forcing the model annually with flux anomalies at the major outlet glaciers (Enderlin et al., 2014, observed from Landsat/ASTER/Operation <span class="hlt">Ice</span>Bridge) and surface <span class="hlt">mass</span> <span class="hlt">balance</span> (van Angelen et al., 2013, calculated from RACMO2) for the period 1991-2012. The <span class="hlt">ice</span> sheet model output is compared to <span class="hlt">ice</span> surface elevation observations from ICESat and <span class="hlt">ice</span> sheet <span class="hlt">mass</span> change observations from GRACE. Early results show promise for assessing the performance of different model configurations. Additionally, we explore the effect of <span class="hlt">ice</span> sheet model resolution on validation skill.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997JGR...10221061S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997JGR...10221061S"><span>The force <span class="hlt">balance</span> of sea <span class="hlt">ice</span> in a numerical model of the Arctic Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steele, Michael; Zhang, Jinlun; Rothrock, Drew; Stern, Harry</p> <p>1997-09-01</p> <p>The <span class="hlt">balance</span> of forces in the sea <span class="hlt">ice</span> model of Hibler [1979] is examined. The model predicts that internal stress gradients are an important force in much of the Arctic Ocean except in summer, when they are significant only off the northern coasts of Greenland and the Canadian Archipelago. A partition of the internal stress gradient between the pressure gradient and the viscous terms reveals that both are significant, although they operate on very different timescales. The acceleration term is generally negligible, while the sum of Coriolis plus sea surface tilt is small. Thus the seasonal average force <span class="hlt">balance</span> in fall, winter, and spring is mostly between three terms of roughly equal magnitudes: air drag, water drag, and internal stress gradients. This is also true for the monthly average force <span class="hlt">balance</span>. However, we find that there is a transition around the weekly timescale and that on a daily basis the force <span class="hlt">balance</span> at a particular location and time is often between only two terms: either between air drag and water drag or between air drag and internal stress gradients. The model is in agreement with the observations of Thorndike and Colony [1982] in that the correlation between geostrophic wind forcing and the model's <span class="hlt">ice</span> velocity field is high. This result is discussed in the context of the force <span class="hlt">balance</span>; we show that the presence of significant internal stress gradients does not preclude high wind-<span class="hlt">ice</span> correlation. A breakdown of the internal stress gradient into component parts reveals that the shear viscous force is far from negligible, which casts strong doubt on the theoretical validity of the cavitating fluid approximation (in which this component is neglected). Finally, the role of <span class="hlt">ice</span> pressure is examined by varying the parameter P*. We find a strong sensitivity in terms of the force <span class="hlt">balance</span>, as well as <span class="hlt">ice</span> thickness and velocity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/ds/676/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/ds/676/"><span>Surface <span class="hlt">Mass</span> <span class="hlt">Balance</span> of the Columbia Glacier, Alaska, 1978 and 2010 <span class="hlt">Balance</span> Years</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>O'Neel, Shad</p> <p>2012-01-01</p> <p>Although Columbia Glacier is one of the largest sources of glacier <span class="hlt">mass</span> loss in Alaska, surface <span class="hlt">mass</span> <span class="hlt">balance</span> measurements are sparse, with only a single data set available from 1978. The dearth of surface <span class="hlt">mass-balance</span> data prohibits partitioning of the total <span class="hlt">mass</span> losses between dynamics and surface forcing; however, the accurate inclusion of calving glaciers into predictive models requires both dynamic and climatic forcing of total <span class="hlt">mass</span> <span class="hlt">balance</span>. During 2010, the U.S. Geological Survey collected surface <span class="hlt">balance</span> data at several locations distributed over the surface of Columbia Glacier to estimate the glacier-wide annual <span class="hlt">balance</span> for <span class="hlt">balance</span> year 2010 using the 2007 area-altitude distribution. This report also summarizes data collected in 1978, calculates the 1978 annual surface <span class="hlt">balance</span>, and uses these observations to constrain the 2010 values, particularly the shape of the <span class="hlt">balance</span> profile. Both years exhibit <span class="hlt">balances</span> indicative of near-equilibrium surface <span class="hlt">mass-balance</span> conditions, and demonstrate the importance of dynamic processes during the rapid retreat.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013TCry....7..569V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013TCry....7..569V"><span><span class="hlt">Balanced</span> conditions or slight <span class="hlt">mass</span> gain of glaciers in the Lahaul and Spiti region (northern India, Himalaya) during the nineties preceded recent <span class="hlt">mass</span> loss</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vincent, C.; Ramanathan, Al.; Wagnon, P.; Dobhal, D. P.; Linda, A.; Berthier, E.; Sharma, P.; Arnaud, Y.; Azam, M. F.; Jose, P. G.; Gardelle, J.</p> <p>2013-04-01</p> <p>The volume change of the Chhota Shigri Glacier (India, 32° 20 N, 77° 30' E) between 1988 and 2010 has been determined using in situ geodetic measurements. This glacier has experienced only a slight <span class="hlt">mass</span> loss between 1988 and 2010 (-3.8 ± 2.0 m w.e. (water equivalent) corresponding to -0.17 ± 0.09 m w.e. yr-1). Using satellite digital elevation models (DEM) differencing and field measurements, we measure a negative <span class="hlt">mass</span> <span class="hlt">balance</span> (MB) between 1999 and 2010 (-4.8 ± 1.8 m w.e. corresponding to -0.44 ± 0.16 m w.e. yr-1). Thus, we deduce a slightly positive or near-zero MB between 1988 and 1999 (+1.0 ± 2.7 m w.e. corresponding to +0.09 ± 0.24 m w.e. yr-1). Furthermore, satellite DEM differencing reveals that the MB of the Chhota Shigri Glacier (-0.39 ± 0.15 m w.e. yr-1) has been only slightly less negative than the MB of a 2110 km2 glaciarized area in the Lahaul and Spiti region (-0.44 ± 0.09 m w.e. yr-1) during 1999-2011. Hence, we conclude that the <span class="hlt">ice</span> wastage is probably moderate in this region over the last 22 yr, with near equilibrium conditions during the nineties, and an <span class="hlt">ice</span> <span class="hlt">mass</span> loss after. The turning point from <span class="hlt">balanced</span> to negative <span class="hlt">mass</span> budget is not known but lies probably in the late nineties and at the latest in 1999. This positive or near-zero MB for Chhota Shigri Glacier (and probably for the surrounding glaciers of the Lahaul and Spiti region) during at least part of the 1990s contrasts with a recent compilation of MB data in the Himalayan range that indicated <span class="hlt">ice</span> wastage since 1975. However, in agreement with this compilation, we confirm more negative <span class="hlt">balances</span> since the beginning of the 21st century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10.2203M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10.2203M"><span>Quantifying <span class="hlt">ice</span> loss in the eastern Himalayas since 1974 using declassified spy satellite imagery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maurer, Joshua M.; Rupper, Summer B.; Schaefer, Joerg M.</p> <p>2016-09-01</p> <p>Himalayan glaciers are important natural resources and climate indicators for densely populated regions in Asia. Remote sensing methods are vital for evaluating glacier response to changing climate over the vast and rugged Himalayan region, yet many platforms capable of glacier <span class="hlt">mass</span> <span class="hlt">balance</span> quantification are somewhat temporally limited due to typical glacier response times. We here rely on declassified spy satellite imagery and ASTER data to quantify surface lowering, <span class="hlt">ice</span> volume change, and geodetic <span class="hlt">mass</span> <span class="hlt">balance</span> during 1974-2006 for glaciers in the eastern Himalayas, centered on the Bhutan-China border. The wide range of glacier types allows for the first <span class="hlt">mass</span> <span class="hlt">balance</span> comparison between clean, debris, and lake-terminating (calving) glaciers in the region. Measured glaciers show significant <span class="hlt">ice</span> loss, with an estimated mean annual geodetic <span class="hlt">mass</span> <span class="hlt">balance</span> of -0.13 ± 0.06 m w.e. yr-1 (meters of water equivalent per year) for 10 clean-<span class="hlt">ice</span> glaciers, -0.19 ± 0.11 m w.e. yr-1 for 5 debris-covered glaciers, -0.28 ± 0.10 m w.e. yr-1 for 6 calving glaciers, and -0.17 ± 0.05 m w.e. yr-1 for all glaciers combined. Contrasting hypsometries along with melt pond, <span class="hlt">ice</span> cliff, and englacial conduit mechanisms result in statistically similar <span class="hlt">mass</span> <span class="hlt">balance</span> values for both clean-<span class="hlt">ice</span> and debris-covered glacier groups. Calving glaciers comprise 18 % (66 km2) of the glacierized area yet have contributed 30 % (-0.7 km3) to the total <span class="hlt">ice</span> volume loss, highlighting the growing relevance of proglacial lake formation and associated calving for the future <span class="hlt">ice</span> <span class="hlt">mass</span> budget of the Himalayas as the number and size of glacial lakes increase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70021003','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70021003"><span>Analysis of difference between direct and geodetic <span class="hlt">mass</span> <span class="hlt">balance</span> measurements at South Cascade Glacier, Washington</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Krimmel, R.M.</p> <p>1999-01-01</p> <p>Net <span class="hlt">mass</span> <span class="hlt">balance</span> has been measured since 1958 at South Cascade Glacier using the 'direct method,' e.g. area averages of snow gain and firn and <span class="hlt">ice</span> loss at stakes. Analysis of cartographic vertical photography has allowed measurement of <span class="hlt">mass</span> <span class="hlt">balance</span> using the 'geodetic method' in 1970, 1975, 1977, 1979-80, and 1985-97. Water equivalent change as measured by these nearly independent methods should give similar results. During 1970-97, the direct method shows a cumulative <span class="hlt">balance</span> of about -15 m, and the geodetic method shows a cumulative <span class="hlt">balance</span> of about -22 m. The deviation between the two methods is fairly consistent, suggesting no gross errors in either, but rather a cumulative systematic error. It is suspected that the cumulative error is in the direct method because the geodetic method is based on a non-changing reference, the bedrock control, whereas the direct method is measured with reference to only the previous year's summer surface. Possible sources of <span class="hlt">mass</span> loss that are missing from the direct method are basal melt, internal melt, and ablation on crevasse walls. Possible systematic measurement errors include under-estimation of the density of lost material, sinking stakes, or poorly represented areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=331262','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=331262"><span>Sensible heat <span class="hlt">balance</span> estimates of transient soil <span class="hlt">ice</span> contents for freezing and thawing conditions</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>Soil <span class="hlt">ice</span> content is an important component for winter soil hydrology. The sensible heat <span class="hlt">balance</span> (SHB) method using measurements from heat pulse probes (HPP) is a possible way to determine transient soil <span class="hlt">ice</span> content. In a previous study, in situ soil <span class="hlt">ice</span> contents estimates with the SHB method were in...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.7457N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.7457N"><span>Quantifying the <span class="hlt">mass</span> loss of peripheral Greenland glaciers and <span class="hlt">ice</span> caps (1958-2014).</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Noël, Brice; van de Berg, Willem Jan; Machguth, Horst; van den Broeke, Michiel</p> <p>2016-04-01</p> <p>Since the 2000s, <span class="hlt">mass</span> loss from Greenland peripheral glaciers and <span class="hlt">ice</span> caps (GICs) has accelerated, becoming an important contributor to sea level rise. Under continued warming throughout the 21st century, GICs might yield up to 7.5 to 11 mm sea level rise, with increasing dominance of surface runoff at the expense of <span class="hlt">ice</span> discharge. However, despite multiple observation campaigns, little remains known about the contribution of GICs to total Greenland <span class="hlt">mass</span> loss. Furthermore, the relatively coarse resolutions in regional climate models, i.e. 5 km to 20 km, fail to represent the small scale patterns of surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) components over these topographically complex regions including also narrow valley glaciers. Here, we present a novel approach to quantify the contribution of GICs to surface melt and runoff, based on an elevation dependent downscaling method. GICs daily SMB components at 1 km resolution are obtained by statistically downscaling the outputs of RACMO2.3 at 11 km resolution to a down-sampled version of the GIMP DEM for the period 1958-2014. This method has recently been successfully validated over the Greenland <span class="hlt">ice</span> sheet and is now applied to GICs. In this study, we first evaluate the 1 km daily downscaled GICs SMB against a newly available and comprehensive dataset of ablation stake measurements. Then, we investigate present-day trends of meltwater production and SMB for different regions and estimate GICs contribution to total Greenland <span class="hlt">mass</span> loss. These data are considered valuable for model evaluation and prediction of future sea level rise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.G44A..04H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.G44A..04H"><span>Earth Structure, <span class="hlt">Ice</span> <span class="hlt">Mass</span> Changes, and the Local Dynamic Geoid</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harig, C.; Simons, F. J.</p> <p>2014-12-01</p> <p> be used for corrections for glacio-isostatic adjustment, as necessary for the interpretation of time-variable gravity observations in terms of <span class="hlt">ice</span> sheet <span class="hlt">mass-balance</span> studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27134805','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27134805"><span>Spatial and temporal Antarctic <span class="hlt">Ice</span> Sheet <span class="hlt">mass</span> trends, glacio-isostatic adjustment, and surface processes from a joint inversion of satellite altimeter, gravity, and GPS data.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Martín-Español, Alba; Zammit-Mangion, Andrew; Clarke, Peter J; Flament, Thomas; Helm, Veit; King, Matt A; Luthcke, Scott B; Petrie, Elizabeth; Rémy, Frederique; Schön, Nana; Wouters, Bert; Bamber, Jonathan L</p> <p>2016-02-01</p> <p>We present spatiotemporal <span class="hlt">mass</span> <span class="hlt">balance</span> trends for the Antarctic <span class="hlt">Ice</span> Sheet from a statistical inversion of satellite altimetry, gravimetry, and elastic-corrected GPS data for the period 2003-2013. Our method simultaneously determines annual trends in <span class="hlt">ice</span> dynamics, surface <span class="hlt">mass</span> <span class="hlt">balance</span> anomalies, and a time-invariant solution for glacio-isostatic adjustment while remaining largely independent of forward models. We establish that over the period 2003-2013, Antarctica has been losing <span class="hlt">mass</span> at a rate of -84 ± 22 Gt yr -1 , with a sustained negative mean trend of dynamic imbalance of -111 ± 13 Gt yr -1 . West Antarctica is the largest contributor with -112 ± 10 Gt yr -1 , mainly triggered by high thinning rates of glaciers draining into the Amundsen Sea Embayment. The Antarctic Peninsula has experienced a dramatic increase in <span class="hlt">mass</span> loss in the last decade, with a mean rate of -28 ± 7 Gt yr -1 and significantly higher values for the most recent years following the destabilization of the Southern Antarctic Peninsula around 2010. The total <span class="hlt">mass</span> loss is partly compensated by a significant <span class="hlt">mass</span> gain of 56 ± 18 Gt yr -1 in East Antarctica due to a positive trend of surface <span class="hlt">mass</span> <span class="hlt">balance</span> anomalies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.G31E..01Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.G31E..01Z"><span>Transient <span class="hlt">ice</span> <span class="hlt">mass</span> variations over Greenland detected by the combination of GPS and GRACE data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, B.; Liu, L.; Khan, S. A.; van Dam, T. M.; Zhang, E.</p> <p>2017-12-01</p> <p>Over the past decade, the Greenland <span class="hlt">Ice</span> Sheet (GrIS) has been undergoing significant warming and <span class="hlt">ice</span> <span class="hlt">mass</span> loss. Such <span class="hlt">mass</span> loss was not always a steady process but had substantial temporal and spatial variabilities. Here we apply multi-channel singular spectral analysis to crustal deformation time series measured at about 50 Global Positioning System (GPS) stations mounted on bedrock around the Greenland coast and <span class="hlt">mass</span> changes inferred from Gravity Recovery and Climate Experiment (GRACE) to detect transient changes in <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> over the GrIS. We detect two transient anomalies: one is a negative melting anomaly (Anomaly 1) that peaked around 2010; the other is a positive melting anomaly (Anomaly 2) that peaked between 2012 and 2013. The GRACE data show that both anomalies caused significant <span class="hlt">mass</span> changes south of 74°N but negligible changes north of 74°N. Both anomalies caused the maximum <span class="hlt">mass</span> change in southeast GrIS, followed by in west GrIS near Jakobshavn. Our results also show that the <span class="hlt">mass</span> change caused by Anomaly 1 first reached the maximum in late 2009 in the southeast GrIS and then migrated to west GrIS. However, in Anomaly 2, the southeast GrIS was the last place that reached the maximum <span class="hlt">mass</span> change in early 2013 and the west GrIS near Jakobshavn was the second latest place that reached the maximum <span class="hlt">mass</span> change. Most of the GPS data show similar spatiotemporal patterns as those obtained from the GRACE data. However, some GPS time series show discrepancies in either space or time, because of data gaps and different sensitivities of <span class="hlt">mass</span> loading change. Namely, loading deformation measured by GPS can be significantly affected by local dynamical <span class="hlt">mass</span> changes, which, yet, has little impact on GRACE observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010002431&hterms=BALANCE+SHEET&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DBALANCE%2BSHEET','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010002431&hterms=BALANCE+SHEET&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DBALANCE%2BSHEET"><span>Troughs on Martian <span class="hlt">Ice</span> Sheets: Analysis of Their Closure and <span class="hlt">Mass</span> <span class="hlt">Balance</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fountain, A.; Kargel, J.; Lewis, K.; MacAyeal, D.; Pfeffer, T.; Zwally, J.</p> <p>2000-01-01</p> <p>At the Copenhagen workshop on Martian polar processes, Ralf Greve commented that the flow regime surrounding scarps and troughs of the Martian polar <span class="hlt">ice</span> sheets cannot be modeled using traditional "plan view" <span class="hlt">ice</span>-sheet models. Such models are inadequate because they typically use reduced equations that embody certain simplifications applicable only to terrestrial <span class="hlt">ice</span> sheets where the upper <span class="hlt">ice</span> sheet surface is smooth. In response to this suggestion, we have constructed a 2-dimensional, time dependent "side view" (two spatial dimensions: one horizontal, one vertical) model of scarp closure that is designed to overcome the difficulties described by Greve. The purpose of the model is to evaluate the scales of stress variation and styles of flow closure so as to estimate errors that may be encountered by "plan view" models. We show that there may be avenues whereby the complications associated with scarp closure can be overcome in "plan view" models through appropriate parameterizations of 3-dimensional effects. Following this, we apply the flow model to simulate the evolution of a typical scarp on the North Polar Cap of Mars. Our simulations investigate: (a) the role of "radiation trapping" (see our companion abstract) in creating and maintaining "spiral-like" scarps on the <span class="hlt">ice</span> sheet, (b) the consequences of different flowlaws and <span class="hlt">ice</span> compositions on scarp evolution and, in particular, scarp age, and (c) the role of dust and debris in scarp evolution.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26887494','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26887494"><span><span class="hlt">Ice</span> stream activity scaled to <span class="hlt">ice</span> sheet volume during Laurentide <span class="hlt">Ice</span> Sheet deglaciation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stokes, C R; Margold, M; Clark, C D; Tarasov, L</p> <p>2016-02-18</p> <p>The contribution of the Greenland and West Antarctic <span class="hlt">ice</span> sheets to sea level has increased in recent decades, largely owing to the thinning and retreat of outlet glaciers and <span class="hlt">ice</span> streams. This dynamic loss is a serious concern, with some modelling studies suggesting that the collapse of a major <span class="hlt">ice</span> sheet could be imminent or potentially underway in West Antarctica, but others predicting a more limited response. A major problem is that observations used to initialize and calibrate models typically span only a few decades, and, at the <span class="hlt">ice</span>-sheet scale, it is unclear how the entire drainage network of <span class="hlt">ice</span> streams evolves over longer timescales. This represents one of the largest sources of uncertainty when predicting the contributions of <span class="hlt">ice</span> sheets to sea-level rise. A key question is whether <span class="hlt">ice</span> streams might increase and sustain rates of <span class="hlt">mass</span> loss over centuries or millennia, beyond those expected for a given ocean-climate forcing. Here we reconstruct the activity of 117 <span class="hlt">ice</span> streams that operated at various times during deglaciation of the Laurentide <span class="hlt">Ice</span> Sheet (from about 22,000 to 7,000 years ago) and show that as they activated and deactivated in different locations, their overall number decreased, they occupied a progressively smaller percentage of the <span class="hlt">ice</span> sheet perimeter and their total discharge decreased. The underlying geology and topography clearly influenced <span class="hlt">ice</span> stream activity, but--at the <span class="hlt">ice</span>-sheet scale--their drainage network adjusted and was linked to changes in <span class="hlt">ice</span> sheet volume. It is unclear whether these findings can be directly translated to modern <span class="hlt">ice</span> sheets. However, contrary to the view that sees <span class="hlt">ice</span> streams as unstable entities that can accelerate <span class="hlt">ice</span>-sheet deglaciation, we conclude that <span class="hlt">ice</span> streams exerted progressively less influence on <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> during the retreat of the Laurentide <span class="hlt">Ice</span> Sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A41C0063M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A41C0063M"><span>Convergence on the Prediction of <span class="hlt">Ice</span> Particle <span class="hlt">Mass</span> and Projected Area in <span class="hlt">Ice</span> Clouds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mitchell, D. L.</p> <p>2013-12-01</p> <p><span class="hlt">Ice</span> particle <span class="hlt">mass</span>- and area-dimensional power law (henceforth m-D and A-D) relationships are building-blocks for formulating microphysical processes and optical properties in cloud and climate models, and they are critical for <span class="hlt">ice</span> cloud remote sensing algorithms, affecting the retrieval accuracy. They can be estimated by (1) directly measuring the sizes, <span class="hlt">masses</span> and areas of individual <span class="hlt">ice</span> particles at ground-level and (2) using aircraft probes to simultaneously measure the <span class="hlt">ice</span> water content (IWC) and <span class="hlt">ice</span> particle size distribution. A third indirect method is to use observations from method 1 to develop an m-A relationship representing mean conditions in <span class="hlt">ice</span> clouds. Owing to a tighter correlation (relative to m-D data), this m-A relationship can be used to estimate m from aircraft probe measurements of A. This has the advantage of estimating m at small sizes, down to 10 μm using the 2D-Sterio probe. In this way, 2D-S measurements of maximum dimension D can be related to corresponding estimates of m to develop <span class="hlt">ice</span> cloud type and temperature dependent m-D expressions. However, these expressions are no longer linear in log-log space, but are slowly varying curves covering most of the size range of natural <span class="hlt">ice</span> particles. This work compares all three of the above methods and demonstrates close agreement between them. Regarding (1), 4869 <span class="hlt">ice</span> particles and corresponding melted hemispheres were measured during a field campaign to obtain D and m. Selecting only those unrimed habits that formed between -20°C and -40°C, the mean <span class="hlt">mass</span> values for selected size intervals are within 35% of the corresponding <span class="hlt">masses</span> predicted by the Method 3 curve based on a similar temperature range. Moreover, the most recent m-D expression based on Method 2 differs by no more than 50% with the m-D curve from Method 3. Method 3 appears to be the most accurate over the observed <span class="hlt">ice</span> particle size range (10-4000 μm). An m-D/A-D scheme was developed by which self-consistent m-D and A-D power laws</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C12B..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C12B..07S"><span>In-situ GPS records of surface <span class="hlt">mass</span> <span class="hlt">balance</span>, firn compaction rates, and <span class="hlt">ice</span>-shelf basal melt rates for Pine Island Glacier, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shean, D. E.; Christianson, K.; Larson, K. M.; Ligtenberg, S.; Joughin, I. R.; Smith, B.; Stevens, C.</p> <p>2016-12-01</p> <p>In recent decades, Pine Island Glacier (PIG) has experienced marked retreat, speedup and thinning due to <span class="hlt">ice</span>-shelf basal melt, internal <span class="hlt">ice</span>-stream instability and feedbacks between these processes. In an effort to constrain recent <span class="hlt">ice</span>-stream dynamics and evaluate potential causes of retreat, we analyzed 2008-2010 and 2012-2014 GPS records for PIG. We computed time series of horizontal velocity, strain rate, multipath-based antenna height, surface elevation, and Lagrangian elevation change (Dh/Dt). These data provide validation for complementary high-resolution WorldView stereo digital elevation model (DEM) records, with sampled DEM vertical error of 0.7 m. The GPS antenna height time series document a relative surface elevation increase of 0.7-1.0 m/yr, which is consistent with estimated surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) of 0.7-0.9 m.w.e./yr from RACMO2.3 and firn compaction rates from the IMAU-FDM dynamic firn model. An abrupt 0.2-0.3 m surface elevation decrease due to surface melt and/or greater near-surface firn compaction is observed during a period of warm atmospheric temperatures from December 2012 to January 2013. Observed surface Dh/Dt for all PIG shelf sites is highly linear with trends of -1 to -4 m/yr and <0.4 m residuals. Similar Dh/Dt estimates with reduced variability are obtained after removing expected downward GPS pole base velocity from observed GPS antenna Dh/Dt. Estimated Dh/Dt basal melt rates are 10 to 40 m/yr for the outer PIG shelf and 4 m/yr for the South shelf. These melt rates are similar to those derived from <span class="hlt">ice</span>-bottom acoustic ranging, phase-sensitive <span class="hlt">ice</span>-penetrating radar, and high-resolution stereo DEM records. The GPS/DEM records document higher melt rates within and near transverse surface depressions and rifts associated with longitudinal extension. Basal melt rates for the 2012-2014 period show limited temporal variability, despite significant change in ocean heat content. This suggests that sub-shelf melt rates are less sensitive to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140006602','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140006602"><span>Dynamic Inland Propagation of Thinning Due to <span class="hlt">Ice</span> Loss at the Margins of the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wang, Wei Li; Li, Jun J.; Zwally, H. Jay</p> <p>2012-01-01</p> <p><span class="hlt">Mass-balance</span> analysis of the Greenland <span class="hlt">ice</span> sheet based on surface elevation changes observed by the European Remote-sensing Satellite (ERS) (1992-2002) and <span class="hlt">Ice</span>, Cloud and land Elevation Satellite (ICESat) (2003-07) indicates that the strongly increased <span class="hlt">mass</span> loss at lower elevations (<2000 m) of the <span class="hlt">ice</span> sheet, as observed during 2003-07, appears to induce interior <span class="hlt">ice</span> thinning at higher elevations. In this paper, we perform a perturbation experiment with a three-dimensional anisotropic <span class="hlt">ice</span>-flow model (AIF model) to investigate this upstream propagation. Observed thinning rates in the regions below 2000m elevation are used as perturbation inputs. The model runs with perturbation for 10 years show that the extensive <span class="hlt">mass</span> loss at the <span class="hlt">ice</span>-sheet margins does in fact cause interior thinning on short timescales (i.e. decadal). The modeled pattern of thinning over the <span class="hlt">ice</span> sheet agrees with the observations, which implies that the strong <span class="hlt">mass</span> loss since the early 2000s at low elevations has had a dynamic impact on the entire <span class="hlt">ice</span> sheet. The modeling results also suggest that even if the large <span class="hlt">mass</span> loss at the margins stopped, the interior <span class="hlt">ice</span> sheet would continue thinning for 300 years and would take thousands of years for full dynamic recovery.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP52A..04A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP52A..04A"><span>How and when to terminate the Pleistocene <span class="hlt">ice</span> ages?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abe-Ouchi, A.; Saito, F.; Kawamura, K.; Takahashi, K.; Raymo, M. E.; Okuno, J.; Blatter, H.</p> <p>2015-12-01</p> <p>Climate change with wax and wane of large Northern Hemisphere <span class="hlt">ice</span> sheet occurred in the past 800 thousand years characterized by 100 thousand year cycle with a large amplitude of sawtooth pattern, following a transition from a period of 40 thousand years cycle with small amplitude of <span class="hlt">ice</span> sheet change at about 1 million years ago. Although the importance of insolation as the ultimate driver is now appreciated, the mechanism what determines timing and strength of terminations are far from clearly understood. Here we show, using comprehensive climate and <span class="hlt">ice</span>-sheet models, that insolation and internal feedbacks between the climate, the <span class="hlt">ice</span> sheets and the lithosphere-asthenosphere system explain the 100,000-year periodicity. The responses of equilibrium states of <span class="hlt">ice</span> sheets to summer insolation show hysteresis, with the shape and position of the hysteresis loop playing a key part in determining the periodicities of glacial cycles. The hysteresis loop of the North American <span class="hlt">ice</span> sheet is such that after inception of the <span class="hlt">ice</span> sheet, its <span class="hlt">mass</span> <span class="hlt">balance</span> remains mostly positive through several precession cycles, whose amplitudes decrease towards an eccentricity minimum. The larger the <span class="hlt">ice</span> sheet grows and extends towards lower latitudes, the smaller is the insolation required to make the <span class="hlt">mass</span> <span class="hlt">balance</span> negative. Therefore, once a large <span class="hlt">ice</span> sheet is established, a moderate increase in insolation is sufficient to trigger a negative <span class="hlt">mass</span> <span class="hlt">balance</span>, leading to an almost complete retreat of the <span class="hlt">ice</span> sheet within several thousand years. We discuss further the mechanism which determine the timing of <span class="hlt">ice</span> age terminations by examining the role of astronomical forcing and change of atmospheric carbon dioxide contents through sensitivity experiments and comparison of several <span class="hlt">ice</span> age cycles with different settings of astronomical forcings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1917568D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1917568D"><span>Insights into the effects of patchy <span class="hlt">ice</span> layers on water <span class="hlt">balance</span> heterogeneity in peatlands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dixon, Simon; Kettridge, Nicholas; Devito, Kevin; Petrone, Rich; Mendoza, Carl; Waddington, Mike</p> <p>2017-04-01</p> <p>Peatlands in boreal and sub-arctic settings are characterised by a high degree of seasonality. During winter soils are frozen and snow covers the surface preventing peat moss growth. Conversely, in summer, soils unfreeze and rain and evapotranspiration drive moss productivity. Although advances have been made in understanding growing season water <span class="hlt">balance</span> and moss dynamics in northern peatlands, there remains a gap in knowledge of inter-seasonal water <span class="hlt">balance</span> as layers of <span class="hlt">ice</span> break up during the spring thaw. Understanding the effects of <span class="hlt">ice</span> layers on spring water <span class="hlt">balance</span> is important as this coincides with periods of high wildfire risk, such as the devastating Fort McMurrary wildfire of May, 2016. We hypothesise that shallow layers of <span class="hlt">ice</span> disconnect the growing surface of moss from a falling water table, and prevent water from being supplied from depth. A disconnect between the evaporating surface and deeper water storage will lead to the drying out of the surface layer of moss and a greater risk of severe spring wildfires. We utilise the unsaturated flow model Hydrus 2D to explore water <span class="hlt">balance</span> in peat layers with an impermeable layer representing <span class="hlt">ice</span>. Additionally we create models to represent the heterogeneous break up of <span class="hlt">ice</span> layers observed in Canadian boreal peatlands; these models explore the ability of breaks in an <span class="hlt">ice</span> layer to connect the evaporating surface to a deeper water table. Results show that peatlands with slower rates of moss growth respond to dry periods by limiting evapotranspiration and thus maintain moist conditions in the sub-surface and a water table above the <span class="hlt">ice</span> layer. Peatlands which are more productive continue to grow moss and evaporate during dry periods; this results in the near surface mosses drying out and the water table dropping below the level of the <span class="hlt">ice</span>. Where there are breaks in the <span class="hlt">ice</span> layer the evaporating surface is able to maintain contact with a falling water table, but connectivity is limited to above the breaks, with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C43A0737F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C43A0737F"><span>Force <span class="hlt">balance</span> and deformation characteristics of anisotropic Arctic sea <span class="hlt">ice</span> (a high resolution study)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Feltham, D. L.; Heorton, H. D.; Tsamados, M.</p> <p>2016-12-01</p> <p>The spatial distribution of Arctic sea <span class="hlt">ice</span> arises from its deformation, driven by external momentum forcing, thermodynamic growth and melt. The deformation of Arctic sea <span class="hlt">ice</span> is observed to have structural alignment on a broad range of length scales. By considering the alignment of diamond-shaped sea <span class="hlt">ice</span> floes, an anisotropic rheology (known as the Elastic Anisotropic Plastic, EAP, rheology) has been developed for use in a climate sea <span class="hlt">ice</span> model. Here we present investigations into the role of anisotropy in determining the internal <span class="hlt">ice</span> stress gradient and the complete force <span class="hlt">balance</span> of Arctic sea <span class="hlt">ice</span> using a state-of-the-art climate sea <span class="hlt">ice</span> model. Our investigations are focused on the link between external imposed dynamical forcing, predominantly the wind stress, and the emergent properties of sea <span class="hlt">ice</span>, including its drift speed and thickness distribution. We analyse the characteristics of deformation events for different sea <span class="hlt">ice</span> states and anisotropic alignment over different regions of the Arctic Ocean. We present the full seasonal stress <span class="hlt">balance</span> and sea <span class="hlt">ice</span> state over the Arctic ocean. We have performed 10 km basin-scale simulations over a 30-year time scale, and 2 km and 500 m resolution simulations in an idealised configuration. The anisotropic EAP sea <span class="hlt">ice</span> rheology gives higher shear stresses than the more customary isotropic EVP rheology, and these reduce <span class="hlt">ice</span> drift speed and mechanical thickening, particularly important in the Archipelago. In the central Arctic the circulation of sea <span class="hlt">ice</span> is reduced allowing it to grow thicker thermodynamically. The emergent stress-strain rate correlations from the EAP model suggest that it is possible to characterise the internal <span class="hlt">ice</span> stresses of Arctic sea <span class="hlt">ice</span> from observable basin-wide deformation and drift patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A51E2104K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A51E2104K"><span>Sensitivity of the Antarctic surface <span class="hlt">mass</span> <span class="hlt">balance</span> to oceanic perturbations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kittel, C.; Amory, C.; Agosta, C.; Fettweis, X.</p> <p>2017-12-01</p> <p>Regional climate models (RCMs) are suitable numerical tools to study the surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) of the wide polar <span class="hlt">ice</span> sheets due to their high spatial resolution and polar-adapted physics. Nonetheless, RCMs are driven at their boundaries and over the ocean by reanalysis or global climate model (GCM) products and are thus influenced by potential biases in these large-scale fields. These biases can be significant for both the atmosphere and the sea surface conditions (i.e. sea <span class="hlt">ice</span> concentration and sea surface temperature). With the RCM MAR, a set of sensitivity experiments has been realized to assess the direct response of the SMB of the Antarctic <span class="hlt">ice</span> sheet to oceanic perturbations. MAR is forced by ERA-Interim and anomalies based on mean GCM biases are introduced in sea surface conditions. Results show significant increases (decreases) of liquid and solid precipitation due to biases related to warm (cold) oceans. As precipitation is mainly caused by low-pressure systems that intrude into the continent and do not penetrate far inland, coastal areas are more sensitive than inland regions. Furthermore, warm ocean representative biases lead to anomalies as large as anomalies simulated by other RCMs or GCMs for the end of the 21st century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70012549','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70012549"><span><span class="hlt">Ice</span> sheet topography by satellite altimetry</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Brooks, R.L.; Campbell, W.J.; Ramseier, R.O.; Stanley, H.R.; Zwally, H.J.</p> <p>1978-01-01</p> <p>The surface elevation of the southern Greenland <span class="hlt">ice</span> sheet and surface features of the <span class="hlt">ice</span> flow are obtained from the radar altimeter on the GEOS 3 satellite. The achieved accuracy in surface elevation is ???2 m. As changes in surface elevation are indicative of changes in <span class="hlt">ice</span> volume, the <span class="hlt">mass</span> <span class="hlt">balance</span> of the present <span class="hlt">ice</span> sheets could be determined by repetitive mapping of the surface elevation and the surface could be monitored to detect surging or significant changes in <span class="hlt">ice</span> flow. ?? 1978 Nature Publishing Group.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.C31B0313S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.C31B0313S"><span>Sub-glacier ocean properties and <span class="hlt">mass</span> <span class="hlt">balance</span> estimates of Petermann Gletscher's floating tongue in Northwestern Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steffen, K.; Huff, R. D.; Cullen, N.; Rignot, E.; Bauder, A.</p> <p>2004-12-01</p> <p>Petermann Gletscher is the largest and most influential outlet glacier in central northern Greenland. Located at 81 N, 60 W, it drains an area of 71,580 km2, with a discharge of 12 cubic km of <span class="hlt">ice</span> per year into the Arctic Ocean. We finished a third field season in spring 2004 collecting in situ data on local climate, <span class="hlt">ice</span> velocity, <span class="hlt">ice</span> thickness profiles and bottom melt rates of the floating <span class="hlt">ice</span> tongue. In addition, water properties (salinity and temperature profiles) in large, channel-like bottom cavities beneath the floating <span class="hlt">ice</span> tongue were measured. The melt rates in these "channels" are in excess of 10 m/y and probably responsible for most of the <span class="hlt">mass</span> loss of the Petermann Gletscher. The ocean measurements will be discussed in comparison with other ocean-profile soundings in the region. The bottom topography of the floating <span class="hlt">ice</span> tongue has been mapped for some regions using surface-based ground penetrating radar at 25 MHz frequency and NASA aircraft radar profiles. A new map showing these under-<span class="hlt">ice</span> features will be presented. GPS tidal motion has been measured over one lunar cycle at the flex zone and on the free floating <span class="hlt">ice</span> tongue. These results will be compared to historic measurements made at the beginning of last century. A "worm-like" sheer feature of 80 m in height and several km in length has been studied using differential GPS readings. The mean velocity of the floating tongue <span class="hlt">ice</span> is 1.08 km/y in that region, whereas the <span class="hlt">ice</span> along the margin has a 30%-reduced flow speed, resulting in this strange looking sheer feature. Finally, the <span class="hlt">mass</span> <span class="hlt">balance</span> of the floating <span class="hlt">ice</span> tongue will be discussed based on in situ measurements, aircraft profiles, satellite data, and model approximations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29066736','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29066736"><span>Enhanced <span class="hlt">ice</span> sheet melting driven by volcanic eruptions during the last deglaciation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Muschitiello, Francesco; Pausata, Francesco S R; Lea, James M; Mair, Douglas W F; Wohlfarth, Barbara</p> <p>2017-10-24</p> <p>Volcanic eruptions can impact the <span class="hlt">mass</span> <span class="hlt">balance</span> of <span class="hlt">ice</span> sheets through changes in climate and the radiative properties of the <span class="hlt">ice</span>. Yet, empirical evidence highlighting the sensitivity of ancient <span class="hlt">ice</span> sheets to volcanism is scarce. Here we present an exceptionally well-dated annual glacial varve chronology recording the melting history of the Fennoscandian <span class="hlt">Ice</span> Sheet at the end of the last deglaciation (∼13,200-12,000 years ago). Our data indicate that abrupt <span class="hlt">ice</span> melting events coincide with volcanogenic aerosol emissions recorded in Greenland <span class="hlt">ice</span> cores. We suggest that enhanced <span class="hlt">ice</span> sheet runoff is primarily associated with albedo effects due to deposition of ash sourced from high-latitude volcanic eruptions. Climate and snowpack <span class="hlt">mass-balance</span> simulations show evidence for enhanced <span class="hlt">ice</span> sheet runoff under volcanically forced conditions despite atmospheric cooling. The sensitivity of past <span class="hlt">ice</span> sheets to volcanic ashfall highlights the need for an accurate coupling between atmosphere and <span class="hlt">ice</span> sheet components in climate models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009085','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009085"><span>Modeling of Firn Compaction for Estimating <span class="hlt">Ice</span>-Sheet <span class="hlt">Mass</span> Change from Observed <span class="hlt">Ice</span>-Sheet Elevation Change</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Li, Jun; Zwally, H. Jay</p> <p>2011-01-01</p> <p>Changes in <span class="hlt">ice</span>-sheet surface elevation are caused by a combination of <span class="hlt">ice</span>-dynamic imbalance, ablation, temporal variations in accumulation rate, firn compaction and underlying bedrock motion. Thus, deriving the rate of <span class="hlt">ice</span>-sheet <span class="hlt">mass</span> change from measured surface elevation change requires information on the rate of firn compaction and bedrock motion, which do not involve changes in <span class="hlt">mass</span>, and requires an appropriate firn density to associate with elevation changes induced by recent accumulation rate variability. We use a 25 year record of surface temperature and a parameterization for accumulation change as a function of temperature to drive a firn compaction model. We apply this formulation to ICESat measurements of surface elevation change at three locations on the Greenland <span class="hlt">ice</span> sheet in order to separate the accumulation-driven changes from the <span class="hlt">ice</span>-dynamic/ablation-driven changes, and thus to derive the corresponding <span class="hlt">mass</span> change. Our calculated densities for the accumulation-driven changes range from 410 to 610 kg/cu m, which along with 900 kg/cu m for the dynamic/ablation-driven changes gives average densities ranging from 680 to 790 kg/cu m. We show that using an average (or "effective") density to convert elevation change to <span class="hlt">mass</span> change is not valid where the accumulation and the dynamic elevation changes are of opposite sign.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5489271','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5489271"><span>Decreasing cloud cover drives the recent <span class="hlt">mass</span> loss on the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hofer, Stefan; Tedstone, Andrew J.; Fettweis, Xavier; Bamber, Jonathan L.</p> <p>2017-01-01</p> <p>The Greenland <span class="hlt">Ice</span> Sheet (GrIS) has been losing <span class="hlt">mass</span> at an accelerating rate since the mid-1990s. This has been due to both increased <span class="hlt">ice</span> discharge into the ocean and melting at the surface, with the latter being the dominant contribution. This change in state has been attributed to rising temperatures and a decrease in surface albedo. We show, using satellite data and climate model output, that the abrupt reduction in surface <span class="hlt">mass</span> <span class="hlt">balance</span> since about 1995 can be attributed largely to a coincident trend of decreasing summer cloud cover enhancing the melt-albedo feedback. Satellite observations show that, from 1995 to 2009, summer cloud cover decreased by 0.9 ± 0.3% per year. Model output indicates that the GrIS summer melt increases by 27 ± 13 gigatons (Gt) per percent reduction in summer cloud cover, principally because of the impact of increased shortwave radiation over the low albedo ablation zone. The observed reduction in cloud cover is strongly correlated with a state shift in the North Atlantic Oscillation promoting anticyclonic conditions in summer and suggests that the enhanced surface <span class="hlt">mass</span> loss from the GrIS is driven by synoptic-scale changes in Arctic-wide atmospheric circulation. PMID:28782014</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28782014','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28782014"><span>Decreasing cloud cover drives the recent <span class="hlt">mass</span> loss on the Greenland <span class="hlt">Ice</span> Sheet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hofer, Stefan; Tedstone, Andrew J; Fettweis, Xavier; Bamber, Jonathan L</p> <p>2017-06-01</p> <p>The Greenland <span class="hlt">Ice</span> Sheet (GrIS) has been losing <span class="hlt">mass</span> at an accelerating rate since the mid-1990s. This has been due to both increased <span class="hlt">ice</span> discharge into the ocean and melting at the surface, with the latter being the dominant contribution. This change in state has been attributed to rising temperatures and a decrease in surface albedo. We show, using satellite data and climate model output, that the abrupt reduction in surface <span class="hlt">mass</span> <span class="hlt">balance</span> since about 1995 can be attributed largely to a coincident trend of decreasing summer cloud cover enhancing the melt-albedo feedback. Satellite observations show that, from 1995 to 2009, summer cloud cover decreased by 0.9 ± 0.3% per year. Model output indicates that the GrIS summer melt increases by 27 ± 13 gigatons (Gt) per percent reduction in summer cloud cover, principally because of the impact of increased shortwave radiation over the low albedo ablation zone. The observed reduction in cloud cover is strongly correlated with a state shift in the North Atlantic Oscillation promoting anticyclonic conditions in summer and suggests that the enhanced surface <span class="hlt">mass</span> loss from the GrIS is driven by synoptic-scale changes in Arctic-wide atmospheric circulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.4160R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.4160R"><span><span class="hlt">Mass</span> <span class="hlt">balance</span> of Djankuat Glacier, Central Caucasus: observations, modeling and prediction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rybak, Oleg; Mariia, Kaminskaia; Stanislav, Kutuzov; Ivan, Lavrentiev; Polina, Morozova; Victor, Popovnin; Elena, Rybak</p> <p>2017-04-01</p> <p>Djankuat is a typical valley glacier on the northern slope of the main Caucasus chain. Its present day area is approximately 2.5 square km with the characteristic <span class="hlt">ice</span> thickness of several tens of meters. As well as other glaciers in the region, Djankuat has been shrinking during the last several decades, its cumulative <span class="hlt">mass</span> <span class="hlt">balance</span> in 1968-2016 was equal to -13.6 m w.e. In general, Caucasus' glaciers lost approximately one-third of their area and half of the volume. Prediction of further deradation of glaciers in changing environment is a challenging task because rivers fed by glacier melt water provide from 40 to 70% of the total river run-off in the adjacent piedmont territories. Growing demand in fresh water is rather critical for the local economy development and for growing population, motivating elaboration of an effitient instrument for evaluation and forecasting of the glaciation in the Greater Caucasus. Unfortunately, systematic observations are sparse limiting possibilities for proper model development for the most of the glaciers. Under these circumstances, we have to rely on the models developed for the few well-studied ones, like Djankuat, which is probably one of the most explored glaciers in the world. Accumulation and ablation rates have been observed here systematically and uninterruptedly since mid 60-ies using dense stake network. Together with the <span class="hlt">mass</span> <span class="hlt">balance</span> components, changes in flow velocity, <span class="hlt">ice</span> thickness and geometry were regularly evaluated. During the last several ablation seasons, direct meteorological observations were carried out using an AMS. Long series of meteorological observations at the nearest weather station allow making assessment of the glacier response to climate change in the second half of the 20th century. Abundant observation data gave us the opportunity to elaborate, calibrate and validate an efficient mathematical model of surface <span class="hlt">mass</span> <span class="hlt">balance</span> of a typical glacier in the region. Since many glaciers in the Caucasus</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.7865I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.7865I"><span>On Land <span class="hlt">Ice</span> <span class="hlt">Mass</span> Change in Southernmost South America, Antarctic Peninsula and Coastal Antarctica consistent with GRACE, GPS and Reconstructed <span class="hlt">Ice</span> History for Past 1000 years.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ivins, Erik; Wiese, David; Watkins, Michael; Yuan, Dah-Ning; Landerer, Felix; Simms, Alex; Boening, Carmen</p> <p>2014-05-01</p> <p>The improved spatial coverage provided by high-quality Global Positioning System observing systems on exposed bedrock has allowed these space geodetic experiments to play an increasingly important role in constraining both glacial isostatic adjustment (GIA) processes and viscoelastic responses to present-day glacial <span class="hlt">mass</span> changes (PGMC). Improved constraints on models of <span class="hlt">ice</span> <span class="hlt">mass</span> change in the Southern Hemisphere at present-day, during the Little <span class="hlt">Ice</span> Age, and during the Late Holocene are invaluable for reconciling climate and sea-level variability on a global scale during the present solar radiation forcing and Milankovic orbital configuration. Studies by Jacobs et al. (1992), Whitehouse et al. (2012), King et al. (2012), Boening et al (2012), and others, support the contention that GRACE observations of both GIA and PGMC in the Southern Hemisphere are dominated by the geography and climate of coastal environments. This makes the proper masking of those environments for GRACE-determinations of secular <span class="hlt">mass</span> <span class="hlt">balance</span> especially sensitive, and downscaling, rescaling, and use of correlation mascon methods a non-trivial part of the analysis. Here we employ two analysis methods to determine the <span class="hlt">mass</span> <span class="hlt">balances</span> of the Antarctic Peninsula and Patagonia and incorporate GPS observations of ongoing uplift for GIA correction into both. Using data that roughly span 2002-2013, we determine -25 ± 5 Gt/yr for the uncorrected Antarctic Peninsula (AP) and -12 Gt/yr for southern Patagonia and the Cordillera Darwin (PCD). With corrections for GIA these are increased to -34 ± 8 Gt/yr for AP and -22 ± 6 Gt/yr for PCD.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000074257&hterms=Antarctic+icebergs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DAntarctic%2Bicebergs','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000074257&hterms=Antarctic+icebergs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DAntarctic%2Bicebergs"><span>Glacier and <span class="hlt">Ice</span> Shelves Studies Using Satellite SAR Interferometry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rignot, Eric</p> <p>1999-01-01</p> <p>Satellite radar interferometry is a powerful technique to measure the surface velocity and topography of glacier <span class="hlt">ice</span>. On <span class="hlt">ice</span> shelves, a quadruple difference technique separates tidal motion from the steady creep flow deformation of <span class="hlt">ice</span>. The results provide a wealth of information about glacier grounding lines , <span class="hlt">mass</span> fluxes, stability, elastic properties of <span class="hlt">ice</span>, and tidal regime. The grounding line, which is where the glacier detaches from its bed and becomes afloat, is detected with a precision of a few tens of meters. Combining this information with satellite radar altimetry makes it possible to measure glacier discharge into the ocean and state of <span class="hlt">mass</span> <span class="hlt">balance</span> with greater precision than ever before, and in turn provide a significant revision of past estimates of <span class="hlt">mass</span> <span class="hlt">balance</span> of the Greenland and Antarctic <span class="hlt">Ice</span> Sheets. Analysis of creep rates on floating <span class="hlt">ice</span> permits an estimation of basal melting at the <span class="hlt">ice</span> shelf underside. The results reveal that the action of ocean water in sub-<span class="hlt">ice</span>-shelf cavities has been largely underestimated by oceanographic models and is the dominant mode of <span class="hlt">mass</span> release to the ocean from an <span class="hlt">ice</span> shelf. Precise mapping of grounding line positions also permits the detection of grounding line migration, which is a fine indicator of glacier change, independent of our knowledge of snow accumulation and <span class="hlt">ice</span> melting. This technique has been successfully used to detect the rapid retreat of Pine Island Glacier, the largest <span class="hlt">ice</span> stream in West Antarctica. Finally, tidal motion of <span class="hlt">ice</span> shelves measured interferometrically provides a modern, synoptic view of the physical processes which govern the formation of tabular icebergs in the Antarctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.G31B0907M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.G31B0907M"><span>Regionally Optimized GRACE Processing and Inter-comparison on the Antarctic <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mohajerani, Y.; Velicogna, I.; Sutterley, T. C.; Rignot, E. J.</p> <p>2017-12-01</p> <p>The Antarctic <span class="hlt">ice</span> sheet is losing <span class="hlt">mass</span> at an accelerating rate, with a sea level contribution that changed from 0.08mm/yr from 1992 to 2001 to 0.4mm/yr from 2002 to 2011. While most of this contribution comes from West Antarctica, Totten Glacier has the largest discharge of <span class="hlt">ice</span> in East Antarctica, with a sea level rise potential of 3.9 m. Furthermore, the drainage basin of Totten Glacier, along the neighboring Moscow University Glacier are below sea level, extending hundreds of kilometers inland. Therefore, obtaining regional estimates of both western and eastern Antarctic basins are of critical importance. The GRACE (Gravity Recovery and Climate Experiment) satellite has been providing <span class="hlt">mass</span> <span class="hlt">balance</span> time-series from geoid changes since 2002. Several mascon and harmonic GRACE solutions are available from different processing centers. Here, we evaluate the various solutions across the <span class="hlt">ice</span> sheet and a new set of regionally optimized mascons to study the <span class="hlt">mass</span> <span class="hlt">balance</span> of Totten and Moscow University glaciers. We obtain a trend of -16.5±4.1Gt/yr with an acceleration of -2.0±1.8Gt/yr2 for the two glaciers for the period April 2002 to December 2016 using the Ivins et al (2013) GIA model (errors include leakage, GIA, and regression errors). We compare the results with the <span class="hlt">Mass</span> Budget Method that combines <span class="hlt">ice</span> discharge (D) and surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) from two models: 1) RACMO2.3, and 2) MAR3.6.4. MBM/RACMO2.3 shows the best agreement with the GRACE estimates. Within the common period from April 2002 to December 2015, the MBM/RACMO2.3 and MAR3.6.4 results are -15.6±1.8Gt/yr and -6.7±1.5Gt/yr respectively, while the GRACE time-series has a trend of -14.8±2.7 Gt/yr. We extend the study to the Getz <span class="hlt">Ice</span> Shelf, the third largest <span class="hlt">ice</span> shelf in West Antarctica after Ronne and Ross West <span class="hlt">ice</span> shelves. We compare our gravity-derived <span class="hlt">mass</span> estimates, the <span class="hlt">mass</span> budget estimates, and the volume changes from altimetry data to compare the estimates and obtain a multi-sensor assessment</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C22A..06R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C22A..06R"><span>Spatiotemporal Variability of Meltwater Refreezing in Southwest Greenland <span class="hlt">Ice</span> Sheet Firn</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rennermalm, A. K.; Hock, R.; Tedesco, M.; Corti, G.; Covi, F.; Miège, C.; Kingslake, J.; Leidman, S. Z.; Munsell, S.</p> <p>2017-12-01</p> <p>A substantial fraction of the summer meltwater formed on the surface of the Greenland <span class="hlt">ice</span> sheet is retained in firn, while the remaining portion runs to the ocean through surface and subsurface channels. Refreezing of meltwater in firn can create impenetrable <span class="hlt">ice</span> lenses, hence being a crucial process in the redistribution of surface runoff. To quantify the impact of refreezing on runoff and current and future Greenland surface <span class="hlt">mass</span> <span class="hlt">balance</span>, a three year National Science Foundation funded project titled "Refreezing in the firn of the Greenland <span class="hlt">ice</span> sheet: Spatiotemporal variability and implications for <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span>" started this past year. Here we present an overview of the project and some initial results from the first field season in May 2017 conducted in proximity of the DYE-2 site in the percolation zone of the Southwest Greenland <span class="hlt">ice</span> sheet at elevations between 1963 and 2355 m a.s.l.. During this fieldwork two automatic weather stations were deployed, outfitted with surface energy <span class="hlt">balance</span> sensors and 16 m long thermistor strings, over 300 km of ground penetrating radar data were collected, and five 20-26 m deep firn cores were extracted and analyzed for density and stratigraphy. Winter snow accumulation was measured along the radar tracks. Preliminary work on the firn-core data reveals increasing frequency and thickness of <span class="hlt">ice</span> lenses at lower <span class="hlt">ice</span>-sheet elevations, in agreement with other recent work in the area. Data collected within this project will facilitate advances in our understanding of the spatiotemporal variability of firn refreezing and its role in the hydrology and surface <span class="hlt">mass</span> <span class="hlt">balance</span> of the Greenland <span class="hlt">Ice</span> Sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRF..119.1995M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRF..119.1995M"><span>Field-calibrated model of melt, refreezing, and runoff for polar <span class="hlt">ice</span> caps: Application to Devon <span class="hlt">Ice</span> Cap</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morris, Richard M.; Mair, Douglas W. F.; Nienow, Peter W.; Bell, Christina; Burgess, David O.; Wright, Andrew P.</p> <p>2014-09-01</p> <p>Understanding the controls on the amount of surface meltwater that refreezes, rather than becoming runoff, over polar <span class="hlt">ice</span> <span class="hlt">masses</span> is necessary for modeling their surface <span class="hlt">mass</span> <span class="hlt">balance</span> and ultimately for predicting their future contributions to global sea level change. We present a modified version of a physically based model that includes an energy <span class="hlt">balance</span> routine and explicit calculation of near-surface meltwater refreezing capacity, to simulate the evolution of near-surface density and temperature profiles across Devon <span class="hlt">Ice</span> Cap in Arctic Canada. Uniquely, our model is initiated and calibrated using high spatial resolution measurements of snow and firn densities across almost the entire elevation range of the <span class="hlt">ice</span> cap for the summer of 2004 and subsequently validated with the same type of measurements obtained during the very different meteorological conditions of summer 2006. The model captures the spatial variability across the transect in bulk snowpack properties although it slightly underestimates the flow of meltwater into the firn of previous years. The percentage of meltwater that becomes runoff is similar in both years; however, the spatial pattern of this melt-runoff relationship is different in the 2 years. The model is found to be insensitive to variation in the depth of impermeable layers within the firn but is very sensitive to variation in air temperature, since the refreezing capacity of firn decreases with increasing temperature. We highlight that the sensitivity of the <span class="hlt">ice</span> cap's surface <span class="hlt">mass</span> <span class="hlt">balance</span> to air temperature is itself dependent on air temperature.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020021952','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020021952"><span>Measurements of <span class="hlt">Ice</span> Particles in Tropical Cirrus Anvils: Importance in Radiation <span class="hlt">Balance</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Foster, Theodore; Arnott, William P.; Hallett, John; Pueschel, Rudi; Strawn, Anthony W. (Technical Monitor)</p> <p>1994-01-01</p> <p>Cirrus is important in the radiation <span class="hlt">balance</span> of the global atmosphere, both at solar and thermal infrared (IR) wavelengths. In particular cirrus produced by deep convection over the oceans in the tropics may be critical in controlling processes whereby energy from warm tropical oceans is injected to different levels in the tropical atmosphere to subsequently influence not only tropical but mid latitude climate. Details of the cloud composition may differentiate between a net cooling or warming at these levels. The cloud composition may change depending on the input of nuclei from volcanic or other sources. Observations of cirrus during the FIRE-2 Project over Coffeyville, Kansas and by satellite demonstrate that cirrus, on occasion, is composed not only of larger particles with significant fall velocity (few hundred micrometers, 0.5 m/s) but much more numerous small particles, size 10-20 micrometers, with small fall velocity (cm/s), which may sometimes dominate the radiation field. This is consistent with emissivity measurements. In the thermal IR, <span class="hlt">ice</span> absorption is strong, so that <span class="hlt">ice</span> particles only 10 micrometers thick are opaque, at some wavelengths; on the other hand at other wavelengths and in the visible, <span class="hlt">ice</span> is only moderately to weakly absorbing. It follows that for strongly absorbing wavelengths the average projected area of the <span class="hlt">ice</span> particles is the important parameter, in weakly absorbing regions it is the volume (<span class="hlt">mass</span>) of <span class="hlt">ice</span> which is important. The shape of particles and also their internal structure may also have significant effect on their radiative properties. In order to access the role of cirrus in the radiation budget it is necessary to measure the distribution of <span class="hlt">ice</span> particles sizes, shapes and concentrations in the regions of interest. A casual observation of any cirrus cloud shows that there is variability down to a scale of at least a few 100 m; this is confirmed by radar and lidar remote sensing. Thus aircraft measurements designed to give</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.9352K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.9352K"><span>Very high resolution surface <span class="hlt">mass</span> <span class="hlt">balance</span> over Greenland modeled by the regional climate model MAR with a downscaling technique</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kittel, Christoph; Lang, Charlotte; Agosta, Cécile; Prignon, Maxime; Fettweis, Xavier; Erpicum, Michel</p> <p>2016-04-01</p> <p>This study presents surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) results at 5 km resolution with the regional climate MAR model over the Greenland <span class="hlt">ice</span> sheet. Here, we use the last MAR version (v3.6) where the land-<span class="hlt">ice</span> module (SISVAT) using a high resolution grid (5km) for surface variables is fully coupled while the MAR atmospheric module running at a lower resolution of 10km. This online downscaling technique enables to correct near-surface temperature and humidity from MAR by a gradient based on elevation before forcing SISVAT. The 10 km precipitation is not corrected. Corrections are stronger over the ablation zone where topography presents more variations. The model has been force by ERA-Interim between 1979 and 2014. We will show the advantages of using an online SMB downscaling technique in respect to an offline downscaling extrapolation based on local SMB vertical gradients. Results at 5 km show a better agreement with the PROMICE surface <span class="hlt">mass</span> <span class="hlt">balance</span> data base than the extrapolated 10 km MAR SMB results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4371949','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4371949"><span>Ocean-driven thinning enhances iceberg calving and retreat of Antarctic <span class="hlt">ice</span> shelves</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Liu, Yan; Moore, John C.; Cheng, Xiao; Gladstone, Rupert M.; Bassis, Jeremy N.; Liu, Hongxing; Wen, Jiahong; Hui, Fengming</p> <p>2015-01-01</p> <p>Iceberg calving from all Antarctic <span class="hlt">ice</span> shelves has never been directly measured, despite playing a crucial role in <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span>. Rapid changes to iceberg calving naturally arise from the sporadic detachment of large tabular bergs but can also be triggered by climate forcing. Here we provide a direct empirical estimate of <span class="hlt">mass</span> loss due to iceberg calving and melting from Antarctic <span class="hlt">ice</span> shelves. We find that between 2005 and 2011, the total <span class="hlt">mass</span> loss due to iceberg calving of 755 ± 24 gigatonnes per year (Gt/y) is only half the total loss due to basal melt of 1516 ± 106 Gt/y. However, we observe widespread retreat of <span class="hlt">ice</span> shelves that are currently thinning. Net <span class="hlt">mass</span> loss due to iceberg calving for these <span class="hlt">ice</span> shelves (302 ± 27 Gt/y) is comparable in magnitude to net <span class="hlt">mass</span> loss due to basal melt (312 ± 14 Gt/y). Moreover, we find that iceberg calving from these decaying <span class="hlt">ice</span> shelves is dominated by frequent calving events, which are distinct from the less frequent detachment of isolated tabular icebergs associated with <span class="hlt">ice</span> shelves in neutral or positive <span class="hlt">mass</span> <span class="hlt">balance</span> regimes. Our results suggest that thinning associated with ocean-driven increased basal melt can trigger increased iceberg calving, implying that iceberg calving may play an overlooked role in the demise of shrinking <span class="hlt">ice</span> shelves, and is more sensitive to ocean forcing than expected from steady state calving estimates. PMID:25733856</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70027302','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70027302"><span>DEM, tide and velocity over sulzberger <span class="hlt">ice</span> shelf, West Antarctica</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Baek, S.; Shum, C.K.; Lee, H.; Yi, Y.; Kwoun, Oh-Ig; Lu, Z.; Braun, Andreas</p> <p>2005-01-01</p> <p>Arctic and Antarctic <span class="hlt">ice</span> sheets preserve more than 77% of the global fresh water and could raise global sea level by several meters if completely melted. Ocean tides near and under <span class="hlt">ice</span> shelves shifts the grounding line position significantly and are one of current limitations to study glacier dynamics and <span class="hlt">mass</span> <span class="hlt">balance</span>. The Sulzberger <span class="hlt">ice</span> shelf is an area of <span class="hlt">ice</span> <span class="hlt">mass</span> flux change in West Antarctica and has not yet been well studied. In this study, we use repeat-pass synthetic aperture radar (SAR) interferometry data from the ERS-1 and ERS-2 tandem missions for generation of a high-resolution (60-m) Digital Elevation Model (DEM) including tidal deformation detection and <span class="hlt">ice</span> stream velocity of the Sulzberger <span class="hlt">Ice</span> Shelf. Other satellite data such as laser altimeter measurements with fine foot-prints (70-m) from NASA's ICESat are used for validation and analyses. The resulting DEM has an accuracy of-0.57??5.88 m and is demonstrated to be useful for grounding line detection and <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> studies. The deformation observed by InSAR is found to be primarily due to ocean tides and atmospheric pressure. The 2-D <span class="hlt">ice</span> stream velocities computed agree qualitatively with previous methods on part of the <span class="hlt">Ice</span> Shelf from passive microwave remote-sensing data (i.e., LANDSAT). ?? 2005 IEEE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17733504','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17733504"><span>Devon island <span class="hlt">ice</span> cap: core stratigraphy and paleoclimate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Koerner, R M</p> <p>1977-04-01</p> <p>Valuable paleoclimatic information can be gained by studying the distribution of melt layers in deep <span class="hlt">ice</span> cores. A profile representing the percentage of <span class="hlt">ice</span> in melt layers in a core drilled from the Devon Island <span class="hlt">ice</span> cap plotted against both time and depth shows that the <span class="hlt">ice</span> cap has experienced a period of very warm summers since 1925, following a period of colder summers between about 1600 and 1925. The earlier period was coldest between 1680 and 1730. There is a high correlation between the melt-layer <span class="hlt">ice</span> percentage and the <span class="hlt">mass</span> <span class="hlt">balance</span> of the <span class="hlt">ice</span> cap. The relation between them suggests that the <span class="hlt">ice</span> cap <span class="hlt">mass</span> <span class="hlt">balance</span> was zero (accumulation equaled ablation) during the colder period but is negative in the present warmer one. There is no firm evidence of a present cooling trend in the summer conditions on the <span class="hlt">ice</span> cap. A comparison with the melt-layer <span class="hlt">ice</span> percentage in cores from the other major Canadian Arctic <span class="hlt">ice</span> caps shows that the variation of summer conditions found for the Devon Island <span class="hlt">ice</span> cap is representative for all the large <span class="hlt">ice</span> caps for about 90 percent of the time. There is also a good correlation between melt-layer percentage and summer sea-<span class="hlt">ice</span> conditions in the archipelago. This suggests that the search for the northwest passage was influenced by changing climate, with the 19th-century peak of the often tragic exploration coinciding with a period of very cold summers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C11C0797A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C11C0797A"><span>In-Situ <span class="hlt">Mass</span> <span class="hlt">Balance</span> Measurements and Morphology Study of Patsio Glacier, Himachal Pradesh, Western Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Angchuk, T.; AL, R.; Mandal, A.; Soheb, M.; Bahuguna, I. M.; Singh, V.; Linda, A.</p> <p>2016-12-01</p> <p>The present ongoing study is oriented to do the detailed study of the Patsio glacier which is in the Bhaga Basin, Lahaul, Himachal Pradesh. Patsio glacier is a compound valley glacier survived by two prominent tributaries namely Eastern and Western. The two tributaries are facing opposite to each other. The Western tributary facing almost eastward shows higher melting as compared to Eastern tributary facing northwest. This is probably due to solar radiation and sunshine hour, as Western tributary receives high solar radiation and for longer duration. A series of supraglacial lakes which were connected to each other through supra channels were observed on the upper part of the ablation zone at an altitude range of 5100 m and 5300 m amsl. A dead <span class="hlt">ice</span> covered with thick debris was observed below the current terminus. Despite the large variability of the <span class="hlt">mass</span> <span class="hlt">balance</span> in the different seasons Patsio glacier annual <span class="hlt">balance</span> for the year 2012-2013 was found to be 0.04 ± 0.40 m w.e. the low values signifies that glacier has lost significant amount of <span class="hlt">mass</span> in recent past and now it is near to the equilibrium state. Seasonal <span class="hlt">mass</span> <span class="hlt">balance</span> of Patsio glacier has shown wide range of variability in the <span class="hlt">mass</span> <span class="hlt">balances</span>. Patsio glacier receives most of the accumulation during the winter months and duration is long whereas, ablation season is short but quite significant. Monthly and daily variation has depicted that peak ablation months are July and August. The daily ablation in the month of August 2013 was found to be around 5 cm per day, probably due to air temperature. To have a clear picture of the meteorological parameters and its relation with glacier an AWS has set up on the Patsio glacier at an altitude of 5050 m amsl in June 2014. Seasonal <span class="hlt">mass</span> <span class="hlt">balance</span> gradients show that gradient was high during the early and late ablation seasons as compared to peak ablation season. The <span class="hlt">mass</span> <span class="hlt">balance</span> for the year 2010-2011 was slightly positive.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70033343','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70033343"><span>Greenland <span class="hlt">ice</span> sheet surface temperature, melt and <span class="hlt">mass</span> loss: 2000-06</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hall, D.K.; Williams, R.S.; Luthcke, S.B.; DiGirolamo, N.E.</p> <p>2008-01-01</p> <p>A daily time series of 'clear-sky' surface temperature has been compiled of the Greenland <span class="hlt">ice</span> sheet (GIS) using 1 km resolution moderate-resolution imaging spectroradiometer (MODIS) land-surface temperature (LST) maps from 2000 to 2006. We also used <span class="hlt">mass</span>-concentration data from the Gravity Recovery and Climate Experiment (GRACE) to study <span class="hlt">mass</span> change in relationship to surface melt from 2003 to 2006. The mean LST of the GIS increased during the study period by ???0.27??Ca-1. The increase was especially notable in the northern half of the <span class="hlt">ice</span> sheet during the winter months. Melt-season length and timing were also studied in each of the six major drainage basins. Rapid (<15 days) and sustained <span class="hlt">mass</span> loss below 2000 m elevation was triggered in 2004 and 2005 as recorded by GRACE when surface melt begins. Initiation of large-scale surface melt was followed rapidly by <span class="hlt">mass</span> loss. This indicates that surface meltwater is flowing rapidly to the base of the <span class="hlt">ice</span> sheet, causing acceleration of outlet glaciers, thus highlighting the metastability of parts of the GIS and the vulnerability of the <span class="hlt">ice</span> sheet to air-temperature increases. If air temperatures continue to rise over Greenland, increased surface melt will play a large role in <span class="hlt">ice</span>-sheet <span class="hlt">mass</span> loss.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7677A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7677A"><span>Melting beneath Greenland outlet glaciers and <span class="hlt">ice</span> streams</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexander, David; Perrette, Mahé; Beckmann, Johanna</p> <p>2015-04-01</p> <p>Basal melting of fast-flowing Greenland outlet glaciers and <span class="hlt">ice</span> streams due to frictional heating at the <span class="hlt">ice</span>-bed interface contributes significantly to total glacier <span class="hlt">mass</span> <span class="hlt">balance</span> and subglacial meltwater flux, yet modelling this basal melt process in Greenland has received minimal research attention. A one-dimensional dynamic <span class="hlt">ice</span>-flow model is calibrated to the present day longitudinal profiles of 10 major Greenland outlet glaciers and <span class="hlt">ice</span> streams (including the Jakobshavn Isbrae, Petermann Glacier and Helheim Glacier) and is validated against published <span class="hlt">ice</span> flow and surface elevation measurements. Along each longitudinal profile, basal melt is calculated as a function of <span class="hlt">ice</span> flow velocity and basal shear stress. The basal shear stress is dependent on the effective pressure (difference between <span class="hlt">ice</span> overburden pressure and water pressure), basal roughness and a sliding parametrization. Model output indicates that where outlet glaciers and <span class="hlt">ice</span> streams terminate into the ocean with either a small floating <span class="hlt">ice</span> tongue or no floating tongue whatsoever, the proportion of basal melt to total melt (surface, basal and submarine melt) is 5-10% (e.g. Jakobshavn Isbrae; Daugaard-Jensen Glacier). This proportion is, however, negligible where larger <span class="hlt">ice</span> tongues lose <span class="hlt">mass</span> mostly by submarine melt (~1%; e.g. Nioghalvfjerdsfjorden Glacier). Modelled basal melt is highest immediately upvalley of the grounding line, with contributions typically up to 20-40% of the total melt for slippery beds and up to 30-70% for resistant beds. Additionally, modelled grounding line and calving front migration inland for all outlet glaciers and <span class="hlt">ice</span> streams of hundreds of metres to several kilometres occurs. Including basal melt due to frictional heating in outlet glacier and <span class="hlt">ice</span> stream models is important for more accurately modelling <span class="hlt">mass</span> <span class="hlt">balance</span> and subglacial meltwater flux, and therefore, more accurately modelling outlet glacier and <span class="hlt">ice</span> stream dynamics and responses to future climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.4115C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.4115C"><span>Antarctic <span class="hlt">ice</span> shelf thickness from CryoSat-2 radar altimetry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chuter, Stephen; Bamber, Jonathan</p> <p>2016-04-01</p> <p>The Antarctic <span class="hlt">ice</span> shelves provide buttressing to the inland grounded <span class="hlt">ice</span> sheet, and therefore play a controlling role in regulating <span class="hlt">ice</span> dynamics and <span class="hlt">mass</span> imbalance. Accurate knowledge of <span class="hlt">ice</span> shelf thickness is essential for input-output method <span class="hlt">mass</span> <span class="hlt">balance</span> calculations, sub-<span class="hlt">ice</span> shelf ocean models and buttressing parameterisations in <span class="hlt">ice</span> sheet models. <span class="hlt">Ice</span> shelf thickness has previously been inferred from satellite altimetry elevation measurements using the assumption of hydrostatic equilibrium, as direct measurements of <span class="hlt">ice</span> thickness do not provide the spatial coverage necessary for these applications. The sensor limitations of previous radar altimeters have led to poor data coverage and a lack of accuracy, particularly the grounding zone where a break in slope exists. We present a new <span class="hlt">ice</span> shelf thickness dataset using four years (2011-2014) of CryoSat-2 elevation measurements, with its SARIn dual antennae mode of operation alleviating the issues affecting previous sensors. These improvements and the dense across track spacing of the satellite has resulted in ˜92% coverage of the <span class="hlt">ice</span> shelves, with substantial improvements, for example, of over 50% across the Venable and Totten <span class="hlt">Ice</span> Shelves in comparison to the previous dataset. Significant improvements in coverage and accuracy are also seen south of 81.5° for the Ross and Filchner-Ronne <span class="hlt">Ice</span> Shelves. Validation of the surface elevation measurements, used to derive <span class="hlt">ice</span> thickness, against NASA ICESat laser altimetry data shows a mean bias of less than 1 m (equivalent to less than 9 m in <span class="hlt">ice</span> thickness) and a fourfold decrease in standard deviation in comparison to the previous continental dataset. Importantly, the most substantial improvements are found in the grounding zone. Validation of the derived thickness data has been carried out using multiple Radio Echo Sounding (RES) campaigns across the continent. Over the Amery <span class="hlt">ice</span> shelf, where extensive RES measurements exist, the mean difference between the datasets is 3</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990JGR....9515959H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990JGR....9515959H"><span>One hundred years of Arctic <span class="hlt">ice</span> cover variations as simulated by a one-dimensional, <span class="hlt">ice</span>-ocean model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hakkinen, S.; Mellor, G. L.</p> <p>1990-09-01</p> <p>A one-dimensional <span class="hlt">ice</span>-ocean model consisting of a second moment, turbulent closure, mixed layer model and a three-layer snow-<span class="hlt">ice</span> model has been applied to the simulation of Arctic <span class="hlt">ice</span> <span class="hlt">mass</span> and mixed layer properties. The results for the climatological seasonal cycle are discussed first and include the salt and heat <span class="hlt">balance</span> in the upper ocean. The coupled model is then applied to the period 1880-1985, using the surface air temperature fluctuations from Hansen et al. (1983) and from Wigley et al. (1981). The analysis of the simulated large variations of the Arctic <span class="hlt">ice</span> <span class="hlt">mass</span> during this period (with similar changes in the mixed layer salinity) shows that the variability in the summer melt determines to a high degree the variability in the average <span class="hlt">ice</span> thickness. The annual oceanic heat flux from the deep ocean and the maximum freezing rate and associated nearly constant minimum surface salinity flux did not vary significantly interannually. This also implies that the oceanic influence on the Arctic <span class="hlt">ice</span> <span class="hlt">mass</span> is minimal for the range of atmospheric variability tested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=59923&keyword=balance+AND+general&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=59923&keyword=balance+AND+general&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>DEVELOPMENT OF A CONTAMINANT TRANSPORT AND FATE <span class="hlt">MASS</span> <span class="hlt">BALANCE</span> CALIBRATION MODEL FOR LAKE MICHIGAN <span class="hlt">MASS</span> <span class="hlt">BALANCE</span> PROJECT (LMMBP)</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Lake Michigan <span class="hlt">Mass</span> <span class="hlt">Balance</span> Project (LMMBP) was initiated to directly support the development of a lakewide management plan (LaMP) for Lake Michigan. A <span class="hlt">mass</span> <span class="hlt">balance</span> modeling approach is proposed for the project to addrss the realtionship between sources of toxic chemicals and thei...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.9445A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.9445A"><span>Mountain glaciers vs <span class="hlt">Ice</span> sheet in Greenland - learning from a new monitoring site in West Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abermann, Jakob; van As, Dirk; Wacker, Stefan; Langley, Kirsty</p> <p>2017-04-01</p> <p>Only 5 out of the 20.000 peripheral glaciers and <span class="hlt">ice</span> caps surrounding Greenland are currently monitored due to logistical challenges and despite their significance for sea level rise. Large spatial coast-to-icesheet <span class="hlt">mass</span> and energy <span class="hlt">balance</span> gradients limit simple upscaling methods from <span class="hlt">ice</span>-sheet observations, which builds the motivation for this study. We present results from a new <span class="hlt">mass</span> and energy <span class="hlt">balance</span> time series at Qasigiannguit glacier (64°09'N; 51°21'W) in Southwest Greenland. Inter-annual variability is discussed and the surface energy <span class="hlt">balance</span> over two summers is quantified and a ranking of the main drivers performed. We find that short-wave net radiation is by far the most dominant energy source during summer, followed by similar amounts of net longwave radiation and sensible heat, respectively. We then relate these observations to synchronous measurements at similar latitude on an outlet glacier of the <span class="hlt">ice</span> sheet a mere 100 km away. We find very pronounced horizontal surface <span class="hlt">mass</span> <span class="hlt">balance</span> gradients, with generally more positive values closer to the coast. We conclude that despite minor differences of atmospheric parameters (i.e. humidity, radiation, and temperature) the main reason for the strongly different signal is a pronounced winter precipitation gradient that translates in a different duration of <span class="hlt">ice</span> exposure and through that an albedo gradient. Modelled energy <span class="hlt">balance</span> gradients converted into <span class="hlt">mass</span> changes show good agreement to measured surface <span class="hlt">mass</span> <span class="hlt">balance</span> gradients and we explore a latitudinal signal of these findings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.3963K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.3963K"><span>Detailed comparison of the geodetic and direct glaciological <span class="hlt">mass</span> <span class="hlt">balances</span> on an annual time scale at Hintereisferner, Austria</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klug, Christoph; Bollmann, Erik; Galos, Stephan; Kaser, Georg; Prinz, Rainer; Rieg, Lorenzo; Sailer, Rudolf</p> <p>2016-04-01</p> <p> eventually built up before the ALS acquisition, is corrected. As snow cover biases are particular uncertain, a statistical approach has been applied to assess combined DTM errors by using the population of DTM differences over stable terrain. This method incorporates all known and unknown error sources from the surface difference in stable areas and uses its median thickness for correction in all altitudinal belts. In addition, intensity data of the ALS surveys are used to classify the optical surface properties into <span class="hlt">ice</span> and firn zones. The resulting grids with according conversion factors (900 and 700 kg/m³ for <span class="hlt">ice</span> and firn, respectively) are combined to calculate <span class="hlt">mass</span> changes. In a last step, the survey dates are adjusted, using numerous field observations. On an annual time scale, the geodetic <span class="hlt">mass</span> <span class="hlt">balances</span> of HEF corrected using this approach, correlate well with the results from the homogenized direct glaciological method. Significant deviations occur in years with few measurements in the uppermost areas applying the direct glaciological method, due to strong melt in areas not equipped with ablation stakes (cf. Figure 2 for 2002/03) or inaccessibility due to weather conditions. On the basis of these results, the conventional error risk (e.g. confidence levels), was adopted in order to test the null hypothesis and to check if unexplained discrepancies suggest reanalyses of glaciological <span class="hlt">mass</span> <span class="hlt">balances</span>. Regarding the cumulative <span class="hlt">mass</span> <span class="hlt">balance</span>, the deviations between the two methods tend to become smaller the longer the period of comparison extends. Averaged between 2001 and 2011 the largest sources of differences are snow cover and density assumptions having high uncertainties in their estimates and/or leading to higher error ranges in the geodetic <span class="hlt">mass</span> <span class="hlt">balances</span>. Some errors were found to have a minor impact and are not treated explicitly, such as uncertainties in different glacier outlines used in both methods or the influence of snow covered and snow free crevasses in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....11390S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....11390S"><span>Do we need long term terrestrial glacier <span class="hlt">mass</span> <span class="hlt">balance</span> monitoring for the future?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Slupetzky, H.</p> <p>2003-04-01</p> <p>Beginning with the International Geophysical Year 1958 and followed by other initiatives for world wide glacier observations such as the International Hydrological Decade, a distinctive increase of glacier research such as <span class="hlt">mass</span> <span class="hlt">balance</span> measurements was initiated. Some of the long term observations are not interrupted since then. However, because of various problems more and more of the long term series had to be given up. Is it possible to fully switch to air- and spaceborne techniques for glacier monitoring? For the <span class="hlt">mass</span> <span class="hlt">balance</span> series (and others glaciological series) we have by far not reached the length of meteorological records. There is an increasing need of longlasting observations for modelling and validation of remote-sensing of snow and <span class="hlt">ice</span>. On Stubacher Sonnblick Kees, a small slope glacier (1,5 km2), in the Eastern Alps, Hohe Tauern, Province of Salzburg, a <span class="hlt">mass</span> <span class="hlt">balance</span> program is carried out. The <span class="hlt">mass</span> <span class="hlt">balance</span> has been measured for 39 years, with some extrapolations back to 1959, providing a record of 44 years. The glacier lost 12 Mio.m3 from 1964 to 2002, but had a period of <span class="hlt">mass</span> gain between 1965 and 1981 of 9,8 Mio m3; since 1982 20,5 Mio m3 were lost. On another small glacier in the same area, the Oedenwinkel Kees, the <span class="hlt">mass</span> gain period and the reaction of the glacier has been surveyed annualy showing a "kinematic wave". Some comperative measurements have been done on the Cathedral Massif Glacier, B.C., Canada 1977 to 1979 and 1998 and by using data from Storglaciaeren, Sweden, to evaluate the AAR ratio to estimate the net mas <span class="hlt">balances</span>. There are some substantial reasons to carry on with direct <span class="hlt">mass</span> <span class="hlt">balance</span> measurements and not to interrupt or even abandon long series. There has been a great effort to sustain long term series. There is a great demand for new international initiatives to ensure the continuation of the world wide terrestrial glacier monitoring net. On Stubacher Sonnblickkees, it can be expected that the glacier will disappear within</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C51A0954S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C51A0954S"><span>Surface melt effects on Cryosat-2 elevation retrievals in the ablation zone of the Greenland <span class="hlt">ice</span> sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Slater, T.; McMillan, M.; Shepherd, A.; Leeson, A.; Cornford, S. L.; Hogg, A.; Gilbert, L.; Muir, A. S.; Briggs, K.</p> <p>2017-12-01</p> <p>Over the past two decades, there has been an acceleration in the rate of <span class="hlt">mass</span> losses from the Greenland <span class="hlt">ice</span> sheet. This acceleration is, in part, attributed to an increasingly negative surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB), linked to increasing melt water runoff rates due to enhanced surface melting. Understanding the past, present and future evolution in surface melting is central to ongoing monitoring of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> and, in turn, to building realistic future projections. Currently, regional climate models are commonly used for this purpose, because direct in-situ observations are spatially and temporally sparse due to the logistics and resources required to collect such data. In particular, modelled SMB is used to estimate the extent and magnitude of surface melting, which influences (1) many geodetic <span class="hlt">mass</span> <span class="hlt">balance</span> estimates, and (2) snowpack microwave scattering properties. The latter is poorly understood and introduces uncertainty into radar altimeter estimates of <span class="hlt">ice</span> sheet evolution. Here, we investigate the changes in CryoSat-2 waveforms and elevation measurements caused by the onset of surface melt in the summer months over the ablation zone of the Greenland <span class="hlt">ice</span> sheet. Specifically, we use CryoSat-2 SARIn mode data acquired between 2011 and 2016, to characterise the effect of high variability in surface melt during this period, and to assess the associated impact on estimates of <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=307925','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=307925"><span>Field test and sensitivity analysis of a sensible heat <span class="hlt">balance</span> method to determine <span class="hlt">ice</span> contents</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>Soil <span class="hlt">ice</span> content impacts winter vadose zone hydrology. It may be possible to estimate changes in soil <span class="hlt">ice</span> content with a sensible heat <span class="hlt">balance</span> (SHB) method, using measurements from heat pulse (HP) sensors. Feasibility of the SHB method is unknown because of difficulties in measuring soil thermal pro...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C21A0703P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C21A0703P"><span>Interannual Variability in Amundsen Sea <span class="hlt">Ice</span>-Shelf Height Change Linked to ENSO</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Paolo, F. S.; Fricker, H. A.; Padman, L.</p> <p>2015-12-01</p> <p>Atmospheric and sea-<span class="hlt">ice</span> conditions around Antarctica, particularly in the Amundsen and Bellingshausen seas, respond to climate dynamics in the tropical Pacific Ocean on interannual time scales including the El Nino-Southern Oscillation (ENSO). It has been hypothesized that the <span class="hlt">mass</span> <span class="hlt">balance</span> of the Antarctic <span class="hlt">Ice</span> Sheet, including its floating <span class="hlt">ice</span> shelves, also responds to this climate signal; however, this has not yet been unambiguously demonstrated. We apply multivariate singular spectrum analysis (MSSA) to our 18-year (1994-2012) time series of <span class="hlt">ice</span>-shelf height in the Amundsen Sea (AS) region. This advanced spectral method distinguishes between regular deterministic behavior ("cycles") at sub-decadal time scale and irregular behavior ("noise") at shorter time scales. Although the long-term trends of AS <span class="hlt">ice</span>-shelf height changes are much larger than the range of interannual variability, the short-term rate of change dh/dt can vary about the trend by more than 50%. The mode of interannual variability in the AS <span class="hlt">ice</span>-shelf height is strongly correlated with the low-frequency mode of ENSO (periodicity of ~4.5 years) as represented by the Southern Oscillation Index. The <span class="hlt">ice</span>-shelf height in the AS is expected to respond to changes in precipitation and inflows of warm subsurface Circumpolar Deep Water (CDW) into the ocean cavities under the <span class="hlt">ice</span> shelves, altering basal melt rates. Since both of these processes affecting <span class="hlt">ice</span>-shelf <span class="hlt">mass</span> <span class="hlt">balance</span> respond to changes in wind fields for different ENSO states, we expect some correlation between them. We will describe the spatial structure of AS <span class="hlt">ice</span>-shelf height response to ENSO, and attempt to distinguish the precipitation signal from basal <span class="hlt">mass</span> <span class="hlt">balance</span> due to changing CDW inflows.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1911992K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1911992K"><span><span class="hlt">Mass</span> <span class="hlt">balance</span> of a highly active rock glacier during the period 1954 and 2016</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kellerer-Pirklbauer, Andreas; Kaufmann, Viktor; Rieckh, Matthias</p> <p>2017-04-01</p> <p>Active rock glaciers are creep phenomena of permafrost in high-relief terrain moving slowly downwards and are often characterised by distinct flow structures with ridges and furrows. Active rock glaciers consist of <span class="hlt">ice</span> and rock material. The <span class="hlt">ice</span> component might be either congelation (refreezing of liquid water) or sedimentary ('glacier') <span class="hlt">ice</span> whereas the rock material might be either of periglacial or glacial origin. The formation period of rock glaciers lasts for centuries to millennia as judged from relative or absolute dating approaches. The input of <span class="hlt">ice</span> and debris onto the rock glacier <span class="hlt">mass</span> transport system over such long periods might change substantially over time. Long-term monitoring of <span class="hlt">mass</span> transport, <span class="hlt">mass</span> changes and nourishment processes of rock glaciers are rare. In this study we analysed on a decadal-scale <span class="hlt">mass</span> transport (based on photogrammetric and geodetic data; series 1969-2016), <span class="hlt">mass</span> changes (geodetically-based <span class="hlt">mass</span> <span class="hlt">balance</span> quantification; series 1954-2012), and <span class="hlt">mass</span> input (based on optical data from an automatic digital camera; series 2006-2016) onto the Hinteres Langtal Rock Glacier. This rock glacier is 900 m long, up to 300 m wide, covers an area of 0.17 km2 and is one of the most active ones in the Eastern European Alps. <span class="hlt">Mass</span> transport rates at the surface indicate relatively low mean annual surface velocities until the beginning of this millennium. A first peak in the horizontal surface velocity was reached in 2003/04 followed by a period of deceleration until 2007/08. Afterwards the rates increased again substantially from year to year with maximum values in 2014/15 (exceeding 6 m/a). This increase in surface velocities during the last decades was accompanied by crevasse formation and landslide activities at its front. <span class="hlt">Mass</span> changes show for all six analysed periods between 1954 and 2012 a clear negative surface elevation change with mean annual values ranging from -0.016 to -0.058 m/a. This implies a total volume decrease of -435,895 m3</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.429...69R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.429...69R"><span>Surface exposure chronology of the Waimakariri glacial sequence in the Southern Alps of New Zealand: Implications for MIS-2 <span class="hlt">ice</span> extent and LGM glacial <span class="hlt">mass</span> <span class="hlt">balance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rother, Henrik; Shulmeister, James; Fink, David; Alexander, David; Bell, David</p> <p>2015-11-01</p> <p>During the late Quaternary, the Southern Alps of New Zealand experienced multiple episodes of glaciation with large piedmont glaciers reaching the coastal plains in the west and expanding into the eastern alpine forelands. Here, we present a new 10Be exposure age chronology for a moraine sequence in the Waimakariri Valley (N-Canterbury), which has long been used as a reference record for correlating glacial events across New Zealand and the wider Southern Hemisphere. Our data indicate that the Waimakariri glacier reached its maximum last glaciation extent prior to ∼26 ka well before the global last glaciation maximum (LGM). This was followed by a gradual reduction in <span class="hlt">ice</span> volume and the abandonment of the innermost LGM moraines at about 17.5 ka. Significantly, we find that during its maximum extent, the Waimakariri glacier overflowed the Avoca Plateau, previously believed to represent a mid-Pleistocene glacial surface (i.e. MIS 8). At the same time, the glacier extended to a position downstream of the Waimakariri Gorge, some 15 km beyond the previously mapped LGM <span class="hlt">ice</span> limit. We use a simple steady-state <span class="hlt">mass</span> <span class="hlt">balance</span> model to test the sensitivity of past glacial accumulation to various climatic parameters, and to evaluate possible climate scenarios capable of generating the <span class="hlt">ice</span> volume required to reach the full local-LGM extent. Model outcomes indicate that under New Zealand's oceanic setting, a cooling of 5 °C, assuming modern precipitation levels, or a cooling of 6.5 °C, assuming a one third reduction in precipitation, would suffice to drive the Waimakariri glacier to the eastern alpine forelands (Canterbury Plains). Our findings demonstrate that the scale of LGM glaciation in the Waimakariri Valley and adjacent major catchments, both in terms of <span class="hlt">ice</span> volume and downvalley <span class="hlt">ice</span> extent, has been significantly underestimated. Our observation that high-lying glacial surfaces, so far believed to represent much older glacial episodes, were glaciated during the LGM</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120013495','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120013495"><span><span class="hlt">Mass</span> Gains of the Antarctic <span class="hlt">Ice</span> Sheet Exceed Losses</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Li, Jun; Robbins, John; Saba, Jack L.; Yi, Donghui; Brenner, Anita; Bromwich, David</p> <p>2012-01-01</p> <p>During 2003 to 2008, the <span class="hlt">mass</span> gain of the Antarctic <span class="hlt">ice</span> sheet from snow accumulation exceeded the <span class="hlt">mass</span> loss from <span class="hlt">ice</span> discharge by 49 Gt/yr (2.5% of input), as derived from ICESat laser measurements of elevation change. The net gain (86 Gt/yr) over the West Antarctic (WA) and East Antarctic <span class="hlt">ice</span> sheets (WA and EA) is essentially unchanged from revised results for 1992 to 2001 from ERS radar altimetry. Imbalances in individual drainage systems (DS) are large (-68% to +103% of input), as are temporal changes (-39% to +44%). The recent 90 Gt/yr loss from three DS (Pine Island, Thwaites-Smith, and Marie-Bryd Coast) of WA exceeds the earlier 61 Gt/yr loss, consistent with reports of accelerating <span class="hlt">ice</span> flow and dynamic thinning. Similarly, the recent 24 Gt/yr loss from three DS in the Antarctic Peninsula (AP) is consistent with glacier accelerations following breakup of the Larsen B and other <span class="hlt">ice</span> shelves. In contrast, net increases in the five other DS of WA and AP and three of the 16 DS in East Antarctica (EA) exceed the increased losses. Alternate interpretations of the <span class="hlt">mass</span> changes driven by accumulation variations are given using results from atmospheric-model re-analysis and a parameterization based on 5% change in accumulation per degree of observed surface temperature change. A slow increase in snowfall with climate waRMing, consistent with model predictions, may be offsetting increased dynamic losses.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www2.ametsoc.org/ams/index.cfm/publications/bulletin-of-the-american-meteorological-society-bams/state-of-the-climate/','USGSPUBS'); return false;" href="https://www2.ametsoc.org/ams/index.cfm/publications/bulletin-of-the-american-meteorological-society-bams/state-of-the-climate/"><span>Glaciers and <span class="hlt">ice</span> caps outside Greenland</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Sharp, Marin; Wolken, G.; Burgess, D.; Cogley, J.G.; Copland, L.; Thomson, L.; Arendt, A.; Wouters, B.; Kohler, J.; Andreassen, L.M.; O'Neel, Shad; Pelto, M.</p> <p>2015-01-01</p> <p>Mountain glaciers and <span class="hlt">ice</span> caps cover an area of over 400 000 km2 in the Arctic, and are a major influence on global sea level (Gardner et al. 2011, 2013; Jacob et al. 2012). They gain <span class="hlt">mass</span> by snow accumulation and lose <span class="hlt">mass</span> by meltwater runoff. Where they terminate in water (ocean or lake), they also lose <span class="hlt">mass</span> by iceberg calving. The climatic <span class="hlt">mass</span> <span class="hlt">balance</span> (Bclim, the difference between annual snow accumulation and annual meltwater runoff) is a widely used index of how glaciers respond to climate variability and change. The total <span class="hlt">mass</span> <span class="hlt">balance</span> (ΔM) is defined as the difference between annual snow accumulation and annual <span class="hlt">mass</span> losses (by iceberg calving plus runoff).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Icar..251..211B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Icar..251..211B"><span>Transient bright "halos" on the South Polar Residual Cap of Mars: Implications for <span class="hlt">mass-balance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Becerra, Patricio; Byrne, Shane; Brown, Adrian J.</p> <p>2015-05-01</p> <p>Spacecraft imaging of Mars' south polar region during mid-southern summer of Mars year 28 (2007) observed bright halo-like features surrounding many of the pits, scarps and slopes of the heavily eroded carbon dioxide <span class="hlt">ice</span> of the South Polar Residual Cap (SPRC). These features had not been observed before, and have not been observed since. We report on the results of an observational study of these halos, and spectral modeling of the SPRC surface at the time of their appearance. Image analysis was performed using data from MRO's Context Camera (CTX), and High Resolution Imaging Science Experiment (HiRISE), as well as images from Mars Global Surveyor's (MGS) Mars Orbiter Camera (MOC). Data from MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) were used for the spectral analysis of the SPRC <span class="hlt">ice</span> at the time of the halos. These data were compared with a Hapke reflectance model of the surface to constrain their formation mechanism. We find that the unique appearance of the halos is intimately linked to a near-perihelion global dust storm that occurred shortly before they were observed. The combination of vigorous summertime sublimation of carbon dioxide <span class="hlt">ice</span> from sloped surfaces on the SPRC and simultaneous settling of dust from the global storm, resulted in a sublimation wind that deflected settling dust particles away from the edges of these slopes, keeping these areas relatively free of dust compared to the rest of the cap. The fact that the halos were not exhumed in subsequent years indicates a positive <span class="hlt">mass-balance</span> for flat portions of the SPRC in those years. A net accumulation <span class="hlt">mass-balance</span> on flat surfaces of the SPRC is required to preserve the cap, as it is constantly being eroded by the expansion of the pits and scarps that populate its surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C53A0822T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C53A0822T"><span>Modeling North American <span class="hlt">Ice</span> Sheet Response to Changes in Precession and Obliquity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tabor, C.; Poulsen, C. J.; Pollard, D.</p> <p>2012-12-01</p> <p>Milankovitch theory proposes that changes in insolation due to orbital perturbations dictate the waxing and waning of the <span class="hlt">ice</span> sheets (Hays et al., 1976). However, variations in solar forcing alone are insufficient to produce the glacial oscillations observed in the climate record. Non-linear feedbacks in the Earth system likely work in concert with the orbital cycles to produce a modified signal (e.g. Berger and Loutre, 1996), but the nature of these feedbacks remain poorly understood. To gain a better understand of the <span class="hlt">ice</span> dynamics and climate feedbacks associated with changes in orbital configuration, we use a complex Earth system model consisting of the GENESIS GCM and land surface model (Pollard and Thompson, 1997), the Pennsylvania State University <span class="hlt">ice</span> sheet model (Pollard and DeConto, 2009), and the BIOME vegetation model (Kaplan et al., 2001). We began this study by investigating <span class="hlt">ice</span> sheet sensitivity to a range of commonly used <span class="hlt">ice</span> sheet model parameters, including <span class="hlt">mass</span> <span class="hlt">balance</span> and albedo, to optimize simulations for Pleistocene orbital cycles. Our tests indicate that choice of <span class="hlt">mass</span> <span class="hlt">balance</span> and albedo parameterizations can lead to significant differences in <span class="hlt">ice</span> sheet behavior and volume. For instance, use of an insolation-temperature <span class="hlt">mass</span> <span class="hlt">balance</span> scheme (van den Berg, 2008) allows for a larger <span class="hlt">ice</span> sheet response to orbital changes than the commonly employed positive degree-day method. Inclusion of a large temperature dependent <span class="hlt">ice</span> albedo, representing phenomena such as melt ponds and dirty <span class="hlt">ice</span>, also enhances <span class="hlt">ice</span> sheet sensitivity. Careful tuning of <span class="hlt">mass</span> <span class="hlt">balance</span> and albedo parameterizations can help alleviate the problem of insufficient <span class="hlt">ice</span> sheet retreat during periods of high summer insolation (Horton and Poulsen, 2007) while still accurately replicating the modern climate. Using our optimized configuration, we conducted a series of experiments with idealized transient orbits in an asynchronous coupling scheme to investigate the influence of obliquity and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995JGR...10014269P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995JGR...10014269P"><span>Coupled energy-<span class="hlt">balance/ice</span>-sheet model simulations of the glacial cycle: A possible connection between terminations and terrigenous dust</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Peltier, W. Richard; Marshall, Shawn</p> <p>1995-07-01</p> <p>We apply a coupled energy-<span class="hlt">balance/ice</span>-sheet climate model in an investigation of northern hemisphere <span class="hlt">ice</span>-sheet advance and retreat over the last glacial cycle. When driven only by orbital insolation variations, the model predicts <span class="hlt">ice</span>-sheet advances over the continents of North America and Eurasia that are in good agreement with geological reconstructions in terms of the timescale of advance and the spatial positioning of the main <span class="hlt">ice</span> <span class="hlt">masses</span>. The orbital forcing alone, however, is unable to induce the observed rapid <span class="hlt">ice</span>-sheet retreat, and we conclude that additional climatic feedbacks not explicitly included in the basic model must be acting. In the analyses presented here we have parameterized a number of potentially important effects in order to test their relative influence on the process of glacial termination. These include marine instability, thermohaline circulation effects, carbon dioxide variations, and snow albedo changes caused by dust loading during periods of high atmospheric aerosol concentration. For the purpose of these analyses the temporal changes in the latter two variables were inferred from <span class="hlt">ice</span> core records. Of these various influences, our analyses suggest that the albedo variations in the <span class="hlt">ice</span>-sheet ablation zone caused by dust loading may represent an extremely important ablation mechanism. Using our parameterization of "dirty" snow in the ablation zone we find glacial retreat to be strongly accelerated, such that complete collapse of the otherwise stable Laurentide <span class="hlt">ice</span> sheet ensues. The last glacial maximum configurations of the Laurentide and Fennoscandian complexes are also brought into much closer accord with the <span class="hlt">ICE</span>-3G reconstruction of Tushingham and Peltier (1991,1992) and the <span class="hlt">ICE</span>-4G reconstruction of Peltier (1994) when this effect is reasonably introduced.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040030573','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040030573"><span>Glacier <span class="hlt">Ice</span> <span class="hlt">Mass</span> Fluctuations and Fault Instability in Tectonically Active Southern Alaska</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>SauberRosenberg, Jeanne M.; Molnia, Bruce F.</p> <p>2003-01-01</p> <p>Across southern Alaska the northwest directed subduction of the Pacific plate is accompanied by accretion of the Yakutat terrane to continental Alaska. This has led to high tectonic strain rates and dramatic topographic relief of more than 5000 meters within 15 km of the Gulf of Alaska coast. The glaciers of this area are extensive and include large glaciers undergoing wastage (glacier retreat and thinning) and surges. The large glacier <span class="hlt">ice</span> <span class="hlt">mass</span> changes perturb the tectonic rate of deformation at a variety of temporal and spatial scales. We estimated surface displacements and stresses associated with <span class="hlt">ice</span> <span class="hlt">mass</span> fluctuations and tectonic loading by examining GPS geodetic observations and numerical model predictions. Although the glacial fluctuations perturb the tectonic stress field, especially at shallow depths, the largest contribution to ongoing crustal deformation is horizontal tectonic strain due to plate convergence. Tectonic forces are thus the primary force responsible for major earthquakes. However, for geodetic sites located < 10-20 km from major <span class="hlt">ice</span> <span class="hlt">mass</span> fluctuations, the changes of the solid Earth due to <span class="hlt">ice</span> loading and unloading are an important aspect of interpreting geodetic results. The <span class="hlt">ice</span> changes associated with Bering Glacier s most recent surge cycle are large enough to cause discernible surface displacements. Additionally, <span class="hlt">ice</span> <span class="hlt">mass</span> fluctuations associated with the surge cycle can modify the short-term seismicity rates in a local region. For the thrust faulting environment of the study region a large decrease in <span class="hlt">ice</span> load may cause an increase in seismic rate in a region close to failure whereas <span class="hlt">ice</span> loading may inhibit thrust faulting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C13D0869M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C13D0869M"><span>Geodetic <span class="hlt">mass</span> <span class="hlt">balance</span> of key glaciers across High Mountain Asia: a multi-decadal survey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maurer, J. M.; Schaefer, J. M.; Rupper, S.; Corley, A. D.</p> <p>2016-12-01</p> <p>Glaciers in High Mountain Asia (HMA) supply seasonal meltwater for large populations, yet field observations are scarce and glacier sensitivities are poorly understood. In order to link complex atmospheric driving factors with heterogeneous glacier responses, detailed remote sensing observations of past changes in <span class="hlt">ice</span> volume are needed. Here we compile a spatially and temporally extensive satellite-based remote sensing record to quantify multi-decadal geodetic <span class="hlt">mass</span> <span class="hlt">balance</span> of large mountain glaciers across key regions in HMA, including the Pamir, Himachal Pradesh, Uttarakhand, Nepal, Sikkim, and Bhutan regions. By utilizing declassified spy satellite imagery from the 1970's, ASTER scenes spanning 2000-present, and the ALOS global digital surface model, a methodologically homogenous assessment of regional and individual glacier responses to climate change over several decades is obtained. Although gaps due to low radiometric contrast result in significant uncertainties, the consistent approach across the HMA provides a useful comparison of relative geodetic changes between climatically diverse regions. Various patterns of <span class="hlt">ice</span> loss are observed, including dynamic retreat of clean-<span class="hlt">ice</span> glaciers and downwasting of debris-covered glaciers. In particular, we highlight the pronounced thinning and retreat of glaciers undergoing calving into proglacial lakes, which has important implications regarding ongoing and future <span class="hlt">ice</span> loss of HMA glaciers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/wri/1998/4090/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/wri/1998/4090/report.pdf"><span>Water, <span class="hlt">ice</span>, and meteorological measurements at South Cascade Glacier, Washington, 1997 <span class="hlt">balance</span> year</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Krimmel, Robert M.</p> <p>1998-01-01</p> <p>Winter snow accumulation and summer snow, firn, and <span class="hlt">ice</span> melt were measured at South Cascade Glacier, Washington to determine the winter and net <span class="hlt">balances</span> for the 1997 <span class="hlt">balance</span> year. The 1997 winter <span class="hlt">balance</span>, averaged over the glacier, was 3.71 meters, and the net <span class="hlt">balance</span> was 0.63 meter. The winter <span class="hlt">balance</span> was the greatest since 1972 (4.27 meters), and the second largest since the record began in 1959. The net <span class="hlt">balance</span>, which was positive for the second year in a row, was 1.57 meters greater than the 1977-96 average (-0.94 meter). Runoff was measured from the glacier and an adjacent non-glacierized basin. Air temperature and precipitation were measured nearby. This report makes these data available to the glaciological and climatological community.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MS%26E..260a2023A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MS%26E..260a2023A"><span>Prediction of dry <span class="hlt">ice</span> <span class="hlt">mass</span> for firefighting robot actuation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ajala, M. T.; Khan, Md R.; Shafie, A. A.; Salami, MJE; Mohamad Nor, M. I.</p> <p>2017-11-01</p> <p>The limitation in the performance of electric actuated firefighting robots in high-temperature fire environment has led to research on the alternative propulsion system for the mobility of firefighting robots in such environment. Capitalizing on the limitations of these electric actuators we suggested a gas-actuated propulsion system in our earlier study. The propulsion system is made up of a pneumatic motor as the actuator (for the robot) and carbon dioxide gas (self-generated from dry <span class="hlt">ice</span>) as the power source. To satisfy the consumption requirement (9cfm) of the motor for efficient actuation of the robot in the fire environment, the volume of carbon dioxide gas, as well as the corresponding <span class="hlt">mass</span> of the dry <span class="hlt">ice</span> that will produce the required volume for powering and actuation of the robot, must be determined. This article, therefore, presents the computational analysis to predict the volumetric requirement and the dry <span class="hlt">ice</span> <span class="hlt">mass</span> sufficient to power a carbon dioxide gas propelled autonomous firefighting robot in a high-temperature environment. The governing equation of the sublimation of dry <span class="hlt">ice</span> to carbon dioxide is established. An operating time of 2105.53s and operating pressure ranges from 137.9kPa to 482.65kPa were achieved following the consumption rate of the motor. Thus, 8.85m3 is computed as the volume requirement of the CAFFR while the corresponding dry <span class="hlt">ice</span> <span class="hlt">mass</span> for the CAFFR actuation ranges from 21.67kg to 75.83kg depending on the operating pressure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Sci...341..266R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Sci...341..266R"><span><span class="hlt">Ice</span>-Shelf Melting Around Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rignot, E.; Jacobs, S.; Mouginot, J.; Scheuchl, B.</p> <p>2013-07-01</p> <p>We compare the volume flux divergence of Antarctic <span class="hlt">ice</span> shelves in 2007 and 2008 with 1979 to 2010 surface accumulation and 2003 to 2008 thinning to determine their rates of melting and <span class="hlt">mass</span> <span class="hlt">balance</span>. Basal melt of 1325 ± 235 gigatons per year (Gt/year) exceeds a calving flux of 1089 ± 139 Gt/year, making <span class="hlt">ice</span>-shelf melting the largest ablation process in Antarctica. The giant cold-cavity Ross, Filchner, and Ronne <span class="hlt">ice</span> shelves covering two-thirds of the total <span class="hlt">ice</span>-shelf area account for only 15% of net melting. Half of the meltwater comes from 10 small, warm-cavity Southeast Pacific <span class="hlt">ice</span> shelves occupying 8% of the area. A similar high melt/area ratio is found for six East Antarctic <span class="hlt">ice</span> shelves, implying undocumented strong ocean thermal forcing on their deep grounding lines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C53B1039V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C53B1039V"><span>Properties of the surface snow in Princess Elizabeth Land, East Antarctica - climate and non-climate dependent variability of the surface <span class="hlt">mass</span> <span class="hlt">balance</span> and stable water isotopic composition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vladimirova, D.; Ekaykin, A.; Lipenkov, V.; Popov, S. V.; Petit, J. R.; Masson-Delmotte, V.</p> <p>2017-12-01</p> <p>Glaciological and meteorological observations conducted during the past four decades in Princess Elizabeth Land, East Antarctica, are compiled. The database is used to investigate spatial patterns of surface snow isotopic composition and surface <span class="hlt">mass</span> <span class="hlt">balance</span>, including detailed information near subglacial lake Vostok. We show diverse relationships between snow isotopic composition and surface temperature. In the most inland part (elevation 3200-3400 m a.s.l.), surface snow isotopic composition varies independently from surface temperature, and is closely related to the distance to the open water source (with a slope of 0.98±0.17 ‰ per 100 km). Surface <span class="hlt">mass</span> <span class="hlt">balance</span> values are higher along the <span class="hlt">ice</span> sheet slope, and relatively evenly distributed inland. The minimum values of snow isotopic composition and surface <span class="hlt">mass</span> <span class="hlt">balance</span> are identified in an area XX km southwestward from Vostok station. The spatial distribution of deuterium excess delineates regions influenced by the Indian Ocean and Pacific Ocean air <span class="hlt">masses</span>, with Vostok area being situated close to their boundary. Anomalously high deuterium excess values are observed near Dome A, suggesting high kinetic fractionation for its moisture source, or specifically high post-deposition artifacts. The dataset is available for further studies such as the assessment of skills of general circulation or regional atmospheric models, and the search for the oldest <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70011332','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70011332"><span>Snow and <span class="hlt">ice</span> in a changing hydrological world.</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Meier, M.F.</p> <p>1983-01-01</p> <p>Snow cover on land (especially in the Northern Hemisphere) and sea <span class="hlt">ice</span> (especially in the Southern Hemisphere) vary seasonally, and this seasonal change has an important affect on the world climate because snow and sea <span class="hlt">ice</span> reflect solar radiation efficiently and affect other heat flow processes between atmosphere and land or ocean. Glaciers, including <span class="hlt">ice</span> sheets, store most of the fresh water on Earth, but change dimensions relatively slowly. There is no clear evidence that the glacier <span class="hlt">ice</span> volume currently is declining, but more needs to be known about mountain glacier and <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balances</span>. -from Author</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA617624','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA617624"><span><span class="hlt">Mass</span> <span class="hlt">Balance</span> of Multiyear Sea <span class="hlt">Ice</span> in the Southern Beaufort Sea</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2014-09-30</p> <p>Petty et al. We will extend these results by combining them with satelite -derived <span class="hlt">ice</span> age data (Maslanik et al., 2007) to focus on the areal...from buoys and satelites with thickness data from AEM surveys, while for the repeat- Figure 1: “Pseudo-plumes” of icepass analysis we are also using</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33A1178B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33A1178B"><span>Dynamical adjustment of Scandinavian glacier <span class="hlt">mass-balance</span> time series</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bonan, D.; Christian, J. E.; Christianson, K. A.</p> <p>2017-12-01</p> <p>Glacier <span class="hlt">mass</span> wastage is often cited as one of the most visible manifestations of anthropogenic climate change. Annual glacier <span class="hlt">mass-balance</span> is related to local climate and atmospheric circulation, as it is defined as the yearly sum of accumulation and ablation—processes that are strongly influenced by year-to-year fluctuations in precipitation and temperature. Glacier response to a climatic trend can, however, be masked by internal variability in atmospheric circulation, and by non-climatic factors (such as topographic control, wind deposition, and incident solar radiation). Thus, unambiguous attribution of a negative glacier <span class="hlt">mass-balance</span> trend to anthropogenic forcing remains challenging. Maritime glacier <span class="hlt">mass-balance</span> records may be especially difficult to interpret due to the high winter <span class="hlt">balances</span> from decadal-scale climate oscillations and the relatively short time series. Here we examine the influence of climate and atmospheric circulation variability on 14 Norwegian glaciers that span 20° of latitude, from southern Norway to Svalbard. We use dynamical adjustment—a statistical method based on partial least squares regression—to identify the components of variability within the <span class="hlt">mass-balance</span> records that are associated with the time-varying sea level pressure (SLP) and sea surface temperature (SST) fields. We find that 30-50% of the variance in the winter <span class="hlt">mass-balance</span> records of the glaciers in southern Norway is explained by using sea level pressure as a predictor. The leading SLP predictor pattern mimics the spatial signature of the North Atlantic Oscillation (NAO), indicating that winter <span class="hlt">balance</span> is strongly influenced by the NAO. Moreover, the adjusted <span class="hlt">mass-balance</span> records indicate a geographic trend: the southern Norwegian glaciers have significant negative trends in the summer <span class="hlt">balance</span> that remain negative after adjustment, while the more northern glaciers have negative winter <span class="hlt">balance</span> trends that only become significant after adjustment. We look into</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.2810G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.2810G"><span>The projected demise of Barnes <span class="hlt">Ice</span> Cap: Evidence of an unusually warm 21st century Arctic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gilbert, A.; Flowers, G. E.; Miller, G. H.; Refsnider, K. A.; Young, N. E.; Radić, V.</p> <p>2017-03-01</p> <p>As a remnant of the Laurentide <span class="hlt">Ice</span> Sheet, Barnes <span class="hlt">Ice</span> Cap owes its existence and present form in part to the climate of the last glacial period. The <span class="hlt">ice</span> cap has been sustained in the present interglacial climate by its own topography through the <span class="hlt">mass</span> <span class="hlt">balance</span>-elevation feedback. A coupled <span class="hlt">mass</span> <span class="hlt">balance</span> and <span class="hlt">ice</span>-flow model, forced by Coupled Model Intercomparison Project Phase 5 climate model output, projects that the current <span class="hlt">ice</span> cap will likely disappear in the next 300 years. For greenhouse gas Representative Concentration Pathways of +2.6 to +8.5 Wm-2, the projected <span class="hlt">ice</span>-cap survival times range from 150 to 530 years. Measured concentrations of cosmogenic radionuclides 10Be, 26Al, and 14C at sites exposed near the <span class="hlt">ice</span>-cap margin suggest the pending disappearance of Barnes <span class="hlt">Ice</span> Cap is very unusual in the last million years. The data and models together point to an exceptionally warm 21st century Arctic climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.2878B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.2878B"><span>Modelling large-scale <span class="hlt">ice</span>-sheet-climate interactions at the last glacial inception</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Browne, O. J. H.; Gregory, J. M.; Payne, A. J.; Ridley, J. K.; Rutt, I. C.</p> <p>2010-05-01</p> <p>In order to investigate the interactions between coevolving climate and <span class="hlt">ice</span>-sheets on multimillenial timescales, a low-resolution atmosphere-ocean general circulation model (AOGCM) has been coupled to a three-dimensional thermomechanical <span class="hlt">ice</span>-sheet model. We use the FAMOUS AOGCM, which is almost identical in formulation to the widely used HadCM3 AOGCM, but on account of its lower resolution (7.5° longitude × 5° latitude in the atmosphere, 3.75°× 2.5° in the ocean) it runs about ten times faster. We use the community <span class="hlt">ice</span>-sheet model Glimmer at 20 km resolution, with the shallow <span class="hlt">ice</span> approximation and an annual degree-day scheme for surface <span class="hlt">mass</span> <span class="hlt">balance</span>. With the FAMOUS-Glimmer coupled model, we have simulated the growth of the Laurentide and Fennoscandian <span class="hlt">ice</span> sheets at the last glacial inception, under constant orbital forcing and atmospheric composition for 116 ka BP. <span class="hlt">Ice</span> grows in both regions, totalling 5.8 m of sea-level equivalent in 10 ka, slower than proxy records suggest. Positive climate feedbacks reinforce this growth at local scales (order hundreds of kilometres), where changes are an order of magnitude larger than on the global average. The albedo feedback (higher local albedo means a cooler climate) is important in the initial expansion of the <span class="hlt">ice</span>-sheet area. The topography feedback (higher surface means a cooler climate) affects <span class="hlt">ice</span>-sheet thickness and is not noticeable for the first 1 ka. These two feedbacks reinforce each other. Without them, the <span class="hlt">ice</span> volume is ~90% less after 10 ka. In Laurentia, <span class="hlt">ice</span> expands initially on the Canadian Arctic islands. The glaciation of the islands eventually cools the nearby mainland climate sufficiently to produce a positive <span class="hlt">mass</span> <span class="hlt">balance</span> there. Adjacent to the <span class="hlt">ice</span>-sheets, cloud feedbacks tend to reduce the surface <span class="hlt">mass</span> <span class="hlt">balance</span> and restrain <span class="hlt">ice</span> growth; this is an example of a local feedback whose simulation requires a model that includes detailed atmospheric physics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.8194C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.8194C"><span>Energy and <span class="hlt">mass</span> <span class="hlt">balance</span> observations on La Mare Glacier (Ortles-Cevedale, European Alps)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carturan, L.; Cazorzi, F.; Dalla Fontana, G.</p> <p>2009-04-01</p> <p>An experimental site was setup in 2005 on the ablation area of La Mare Glacier, at 2990 m a.s.l., to study the energy and <span class="hlt">mass</span> <span class="hlt">balance</span> exchanges between the glacier surface and the atmosphere and to investigate the climatic sensitivity of this particular glacier. An Automatic Weather Station was operated, in the framework of a monitoring network which has been implemented in the Upper Val de La Mare experimental watershed (Trentino, Italy). This basin was selected for a study of climate change effects on cryosphere and hydrology at high-altitude catchments. The 36.2 km2 wide basin has an average altitude of 2906 m a.s.l. and at present the 25% of its surface is glacierized; the annual runoff regime is dominated by snow and <span class="hlt">ice</span> melt. Direct <span class="hlt">mass</span> <span class="hlt">balance</span> measurements have been performed since 1967 on Careser glacier (2.83 km2) and since 2003 on La Mare glacier (3.97 km2). The AWS is mounted on a tripod which stands freely on the glacier surface and is solar-powered. The variables measured are: air temperature and relative humidity, wind speed and direction, shortwave and longwave incoming and outgoing radiation, precipitation and surface height. All the data are sampled at five-minute intervals as average values, with the exception of surface height which is sampled at hourly intervals, as instantaneous values. The collected data were used to calculate the point energy and <span class="hlt">mass</span> <span class="hlt">balance</span> and to compare the results with similar investigations carried out on glaciers and available in literature. In particular, our attention has been focussed on some processes which regulate the response to climate changes. The relative importance of the energy <span class="hlt">balance</span> components was examined and a clear predominance of shortwave radiation inputs was found to exist during melt conditions. Given the relevance of the shortwave net <span class="hlt">balance</span>, the <span class="hlt">ice</span> albedo temporal variability (values ranging from 0.1 to 0.5) has been investigated and correlated with meteorological variables. Furthermore, a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C23B0790W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C23B0790W"><span>Constraining Aggregate-Scale Solar Energy Partitioning in Arctic Sea <span class="hlt">Ice</span> Through Synthesis of Remote Sensing and Autonomous In-Situ Observations.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wright, N.; Polashenski, C. M.; Deeb, E. J.; Morriss, B. F.; Song, A.; Chen, J.</p> <p>2015-12-01</p> <p>One of the key processes controlling sea <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> in the Arctic is the partitioning of solar energy between reflection back to the atmosphere and absorption into the <span class="hlt">ice</span> and upper ocean. We investigate the solar energy <span class="hlt">balance</span> in the <span class="hlt">ice</span>-ocean system using in-situ data collected from Arctic Observing Network (AON) sea <span class="hlt">ice</span> sites and imagery from high resolution optical satellites. AON assets, including <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> buoys and <span class="hlt">ice</span> tethered profilers, monitor the storage and fluxes of heat in the <span class="hlt">ice</span>-ocean system. High resolution satellite imagery, processed using object-based image classification techniques, allows us to quantify the evolution of surrounding <span class="hlt">ice</span> conditions, including melt pond coverage and floe size distribution, at aggregate scale. We present results from regionally representative sites that constrain the partitioning of absorbed solar energy between <span class="hlt">ice</span> melt and ocean storage, and quantify the strength of the <span class="hlt">ice</span>-albedo feedback. We further demonstrate how the results can be used to validate model representations of the physical processes controlling <span class="hlt">ice</span>-albedo feedbacks. The techniques can be extended to understand solar partitioning across the Arctic basin using additional sites and model based data integration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.5738V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.5738V"><span>The Tweeting <span class="hlt">Ice</span> Shelf: geophysics and outreach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Van Liefferinge, Brice; Berger, Sophie; Drews, Reinhard; Pattyn, Frank</p> <p>2015-04-01</p> <p>Over the last decade the Antarctic and Greenland <span class="hlt">ice</span> sheets have contributed about one third of the annual sea level rise (Hanna et al., 2013). However, it remains difficult to reconcile global <span class="hlt">mass</span> <span class="hlt">balance</span> estimates obtained from different satellite-based methods. A typical approach is to <span class="hlt">balance</span> the <span class="hlt">mass</span> input from atmospheric modelling with the outgoing <span class="hlt">mass</span> flux at the <span class="hlt">ice</span>-sheet boundary (Shepherd et al., 2012). The flux calculations at the boundary rely on satellite-derived surface velocities, which are currently only available as snapshots in time, and which need ground truth for validation. Here, we report on continuous, year-round measurements that aim at improving the input-output method in several aspects and carefully map the flow speed allowing for detecting seasonal variability. For this purpose, we set up in December 2014 three stand-alone single-frequency GPSes on the Roi Baudouin <span class="hlt">ice</span> shelf (East Antarctica). The GPSes are installed across a surface depression (typical for large <span class="hlt">ice</span>-shelf channels), where subglacial melting is expected. This setup allows us to investigate how these channels behave, i.e., if they become wider, whether or not they enhance the <span class="hlt">ice</span> flow, and, in combination with an installed phase-sensitive radar, what amount of melting occurs below the channels in contact with the ocean. The GPS data are transmitted on a daily basis. <span class="hlt">Ice</span>-shelf velocity is derived from the raw hourly location following the methods described in den Ouden et al. (2010), Dunse et al. (2012), and Ahlstrøm et al. (2013). However, a reference station has not been used for the correction. Basic processing involves outliers removal, smoothing, time-series analysis and comparison with tidal models. The project comes alongside an outreach event: on a weekly basis, the <span class="hlt">ice</span> shelf 'tweets' its position, motion and relays other information with respect to the project. The GPS systems can be followed on Twitter via @Tweetin<span class="hlt">Ice</span>Shelf as well as the Tweeting <span class="hlt">Ice</span> Shelf</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040035786&hterms=ships+location&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dships%2Blocation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040035786&hterms=ships+location&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dships%2Blocation"><span>Studies of the Antarctic Sea <span class="hlt">Ice</span> Edges and <span class="hlt">Ice</span> Extents from Satellite and Ship Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Worby, Anthony P.; Comiso, Josefino C.</p> <p>2003-01-01</p> <p>Passive-microwave derived <span class="hlt">ice</span> edge locations in Antarctica are assessed against other satellite data as well as in situ observations of <span class="hlt">ice</span> edge location made between 1989 and 2000. The passive microwave data generally agree with satellite and ship data but the <span class="hlt">ice</span> concentration at the observed <span class="hlt">ice</span> edge varies greatly with averages of 14% for the TEAM algorithm and 19% for the Bootstrap algorithm. The comparisons of passive microwave with the field data show that in the <span class="hlt">ice</span> growth season (March - October) the agreement is extremely good, with r(sup 2) values of 0.9967 and 0.9797 for the Bootstrap and TEAM algorithms respectively. In the melt season however (November - February) the passive microwave <span class="hlt">ice</span> edge is typically 1-2 degrees south of the observations due to the low concentration and saturated nature of the <span class="hlt">ice</span>. Sensitivity studies show that these results can have significant impact on trend and <span class="hlt">mass</span> <span class="hlt">balance</span> studies of the sea <span class="hlt">ice</span> cover in the Southern Ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017E%26PSL.473..247C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017E%26PSL.473..247C"><span>Non-basal dislocations should be accounted for in simulating <span class="hlt">ice</span> <span class="hlt">mass</span> flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chauve, T.; Montagnat, M.; Piazolo, S.; Journaux, B.; Wheeler, J.; Barou, F.; Mainprice, D.; Tommasi, A.</p> <p>2017-09-01</p> <p>Prediction of <span class="hlt">ice</span> <span class="hlt">mass</span> flow and associated dynamics is pivotal at a time of climate change. <span class="hlt">Ice</span> flow is dominantly accommodated by the motion of crystal defects - the dislocations. In the specific case of <span class="hlt">ice</span>, their observation is not always accessible by means of the classical tools such as X-ray diffraction or transmission electron microscopy (TEM). Part of the dislocation population, the geometrically necessary dislocations (GNDs) can nevertheless be constrained using crystal orientation measurements via electron backscattering diffraction (EBSD) associated with appropriate analyses based on the Nye (1950) approach. The present study uses the Weighted Burgers Vectors, a reduced formulation of the Nye theory that enables the characterization of GNDs. Applied to <span class="hlt">ice</span>, this method documents, for the first time, the presence of dislocations with non-basal [ c ] or < c + a > Burgers vectors. These [ c ] or < c + a > dislocations represent up to 35% of the GNDs observed in laboratory-deformed <span class="hlt">ice</span> samples. Our findings offer a more complex and comprehensive picture of the key plasticity processes responsible for polycrystalline <span class="hlt">ice</span> creep and provide better constraints on the constitutive mechanical laws implemented in <span class="hlt">ice</span> sheet flow models used to predict the response of Earth <span class="hlt">ice</span> <span class="hlt">masses</span> to climate change.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C44A..07D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C44A..07D"><span>Bayesian prediction of future <span class="hlt">ice</span> sheet volume using local approximation Markov chain Monte Carlo methods</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Davis, A. D.; Heimbach, P.; Marzouk, Y.</p> <p>2017-12-01</p> <p>We develop a Bayesian inverse modeling framework for predicting future <span class="hlt">ice</span> sheet volume with associated formal uncertainty estimates. Marine <span class="hlt">ice</span> sheets are drained by fast-flowing <span class="hlt">ice</span> streams, which we simulate using a flowline model. Flowline models depend on geometric parameters (e.g., basal topography), parameterized physical processes (e.g., calving laws and basal sliding), and climate parameters (e.g., surface <span class="hlt">mass</span> <span class="hlt">balance</span>), most of which are unknown or uncertain. Given observations of <span class="hlt">ice</span> surface velocity and thickness, we define a Bayesian posterior distribution over static parameters, such as basal topography. We also define a parameterized distribution over variable parameters, such as future surface <span class="hlt">mass</span> <span class="hlt">balance</span>, which we assume are not informed by the data. Hyperparameters are used to represent climate change scenarios, and sampling their distributions mimics internal variation. For example, a warming climate corresponds to increasing mean surface <span class="hlt">mass</span> <span class="hlt">balance</span> but an individual sample may have periods of increasing or decreasing surface <span class="hlt">mass</span> <span class="hlt">balance</span>. We characterize the predictive distribution of <span class="hlt">ice</span> volume by evaluating the flowline model given samples from the posterior distribution and the distribution over variable parameters. Finally, we determine the effect of climate change on future <span class="hlt">ice</span> sheet volume by investigating how changing the hyperparameters affects the predictive distribution. We use state-of-the-art Bayesian computation to address computational feasibility. Characterizing the posterior distribution (using Markov chain Monte Carlo), sampling the full range of variable parameters and evaluating the predictive model is prohibitively expensive. Furthermore, the required resolution of the inferred basal topography may be very high, which is often challenging for sampling methods. Instead, we leverage regularity in the predictive distribution to build a computationally cheaper surrogate over the low dimensional quantity of interest (future <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11..773L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11..773L"><span>Regional Greenland accumulation variability from Operation <span class="hlt">Ice</span>Bridge airborne accumulation radar</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lewis, Gabriel; Osterberg, Erich; Hawley, Robert; Whitmore, Brian; Marshall, Hans Peter; Box, Jason</p> <p>2017-03-01</p> <p>The <span class="hlt">mass</span> <span class="hlt">balance</span> of the Greenland <span class="hlt">Ice</span> Sheet (GrIS) in a warming climate is of critical interest to scientists and the general public in the context of future sea-level rise. An improved understanding of temporal and spatial variability of snow accumulation will reduce uncertainties in GrIS <span class="hlt">mass</span> <span class="hlt">balance</span> models and improve projections of Greenland's contribution to sea-level rise, currently estimated at 0.089 ± 0.03 m by 2100. Here we analyze 25 NASA Operation <span class="hlt">Ice</span>Bridge accumulation radar flights totaling > 17 700 km from 2013 to 2014 to determine snow accumulation in the GrIS dry snow and percolation zones over the past 100-300 years. <span class="hlt">Ice</span>Bridge accumulation rates are calculated and used to validate accumulation rates from three regional climate models. Averaged over all 25 flights, the RMS difference between the models and <span class="hlt">Ice</span>Bridge accumulation is between 0.023 ± 0.019 and 0.043 ± 0.029 m w.e. a-1, although each model shows significantly larger differences from <span class="hlt">Ice</span>Bridge accumulation on a regional basis. In the southeast region, for example, the Modèle Atmosphérique Régional (MARv3.5.2) overestimates by an average of 20.89 ± 6.75 % across the drainage basin. Our results indicate that these regional differences between model and <span class="hlt">Ice</span>Bridge accumulation are large enough to significantly alter GrIS surface <span class="hlt">mass</span> <span class="hlt">balance</span> estimates. Empirical orthogonal function analysis suggests that the first two principal components account for 33 and 19 % of the variance, and correlate with the Atlantic Multidecadal Oscillation (AMO) and wintertime North Atlantic Oscillation (NAO), respectively. Regions that disagree strongest with climate models are those in which we have the fewest <span class="hlt">Ice</span>Bridge data points, requiring additional in situ measurements to verify model uncertainties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.2635A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.2635A"><span>Modelled non-linear response to climate of Hardangerjøkulen <span class="hlt">ice</span> cap, southern Norway, since the mid-Holocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Åkesson, Henning; Nisancioglu, Kerim H.; Giesen, Rianne H.; Morlighem, Mathieu</p> <p>2016-04-01</p> <p>Glacier and <span class="hlt">ice</span> cap volume changes currently amount to half of the total cryospheric contribution to sea-level rise and are projected to remain substantial throughout the 21st century. To simulate glacier behavior on centennial and longer time scales, models rely on simplified dynamics and tunable parameters for processes not well understood. Model calibration is often done using present-day observations, even though the relationship between parameters and parametrized processes may be altered for significantly different glacier states. In this study, we simulate the Hardangerjøkulen <span class="hlt">ice</span> cap in southern Norway since the mid-Holocene, through the Little <span class="hlt">Ice</span> Age (LIA) and into the future. We run an ensemble for both calibration and transient experiments, using a two-dimensional <span class="hlt">ice</span> flow model with mesh refinement. For the Holocene, we apply a simple <span class="hlt">mass</span> <span class="hlt">balance</span> forcing based on climate reconstructions. For the LIA until 1962, we use geomorphological evidence and measured outlet glacier positions to find a <span class="hlt">mass</span> <span class="hlt">balance</span> history, while we use direct <span class="hlt">mass</span> <span class="hlt">balance</span> measurements from 1963 until today. Given a linear climate forcing, we show that Hardangerøkulen grew from <span class="hlt">ice</span>-free conditions in the mid-Holocene, to its maximum LIA extent in a highly non-linear fashion. We relate this to local bed topography and demonstrate that volume and area of some but not all outlet glaciers, as well as the entire <span class="hlt">ice</span> cap, become decoupled for several centuries during our simulation of the late Holocene, before co-varying approaching the LIA. Our model is able to simulate most recorded <span class="hlt">ice</span> cap and outlet glacier changes from the LIA until today. We show that present-day Hardangerøkulen is highly sensitive to <span class="hlt">mass</span> <span class="hlt">balance</span> changes, and estimate that the <span class="hlt">ice</span> cap will melt completely by the year 2100.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3409788','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3409788"><span>Bedrock displacements in Greenland manifest <span class="hlt">ice</span> <span class="hlt">mass</span> variations, climate cycles and climate change</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bevis, Michael; Wahr, John; Khan, Shfaqat A.; Madsen, Finn Bo; Brown, Abel; Willis, Michael; Kendrick, Eric; Knudsen, Per; Box, Jason E.; van Dam, Tonie; Caccamise, Dana J.; Johns, Bjorn; Nylen, Thomas; Abbott, Robin; White, Seth; Miner, Jeremy; Forsberg, Rene; Zhou, Hao; Wang, Jian; Wilson, Terry; Bromwich, David; Francis, Olivier</p> <p>2012-01-01</p> <p>The Greenland GPS Network (GNET) uses the Global Positioning System (GPS) to measure the displacement of bedrock exposed near the margins of the Greenland <span class="hlt">ice</span> sheet. The entire network is uplifting in response to past and present-day changes in <span class="hlt">ice</span> <span class="hlt">mass</span>. Crustal displacement is largely accounted for by an annual oscillation superimposed on a sustained trend. The oscillation is driven by earth’s elastic response to seasonal variations in <span class="hlt">ice</span> <span class="hlt">mass</span> and air <span class="hlt">mass</span> (i.e., atmospheric pressure). Observed vertical velocities are higher and often much higher than predicted rates of postglacial rebound (PGR), implying that uplift is usually dominated by the solid earth’s instantaneous elastic response to contemporary losses in <span class="hlt">ice</span> <span class="hlt">mass</span> rather than PGR. Superimposed on longer-term trends, an anomalous ‘pulse’ of uplift accumulated at many GNET stations during an approximate six-month period in 2010. This anomalous uplift is spatially correlated with the 2010 melting day anomaly. PMID:22786931</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000072579','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000072579"><span>Infrared Observations of Hot Gas and Cold <span class="hlt">Ice</span> Toward the Low <span class="hlt">Mass</span> Protostar Elias 29</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Boogert, A. C. A.; Tielens, A. G. G. M.; Ceccarelli, C.; Boonman, A. M. S.; vanDishoeck, E. F.; Keane, J. V.; Whittet, D. C. B.; deGraauw, T.</p> <p>2000-01-01</p> <p>We have obtained the full 1-200 micrometer spectrum of the low luminosity (36 solar luminosity Class I protostar Elias 29 in the rho Ophiuchi molecular cloud. It provides a unique opportunity to study the origin and evolution of interstellar <span class="hlt">ice</span> and the interrelationship of interstellar <span class="hlt">ice</span> and hot core gases around low <span class="hlt">mass</span> protostars. We see abundant hot CO and H2O gas, as well as the absorption bands of CO, CO2, H2O and "6.85 micrometer" <span class="hlt">ices</span>. We compare the abundances and physical conditions of the gas and <span class="hlt">ices</span> toward Elias 29 with the conditions around several well studied luminous, high <span class="hlt">mass</span> protostars. The high gas temperature and gas/solid ratios resemble those of relatively evolved high <span class="hlt">mass</span> objects (e.g. GL 2591). However, none of the <span class="hlt">ice</span> band profiles shows evidence for significant thermal processing, and in this respect Elias 29 resembles the least evolved luminous protostars, such as NGC 7538 : IRS9. Thus we conclude that the heating of the envelope of the low <span class="hlt">mass</span> object Elias 29 is qualitatively different from that of high <span class="hlt">mass</span> protostars. This is possibly related to a different density gradient of the envelope or shielding of the <span class="hlt">ices</span> in a circumstellar disk. This result is important for our understanding of the evolution of interstellar <span class="hlt">ices</span>, and their relation to cometary <span class="hlt">ices</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004GPC....42..279S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004GPC....42..279S"><span>Glacier <span class="hlt">ice</span> <span class="hlt">mass</span> fluctuations and fault instability in tectonically active Southern Alaska</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sauber, Jeanne M.; Molnia, Bruce F.</p> <p>2004-07-01</p> <p>Across the plate boundary zone in south central Alaska, tectonic strain rates are high in a region that includes large glaciers undergoing wastage (glacier retreat and thinning) and surges. For the coastal region between the Bering and Malaspina Glaciers, the average <span class="hlt">ice</span> <span class="hlt">mass</span> thickness changes between 1995 and 2000 range from 1 to 5 m/year. These <span class="hlt">ice</span> changes caused solid Earth displacements in our study region with predicted values of -10 to 50 mm in the vertical and predicted horizontal displacements of 0-10 mm at variable orientations. Relative to stable North America, observed horizontal rates of tectonic deformation range from 10 to 40 mm/year to the north-northwest and the predicted tectonic uplift rates range from approximately 0 mm/year near the Gulf of Alaska coast to 12 mm/year further inland. The <span class="hlt">ice</span> <span class="hlt">mass</span> changes between 1995 and 2000 resulted in discernible changes in the Global Positioning System (GPS) measured station positions of one site (ISLE) located adjacent to the Bagley <span class="hlt">Ice</span> Valley and at one site, DON, located south of the Bering Glacier terminus. In addition to modifying the surface displacements rates, we evaluated the influence <span class="hlt">ice</span> changes during the Bering glacier surge cycle had on the background seismic rate. We found an increase in the number of earthquakes ( ML≥2.5) and seismic rate associated with <span class="hlt">ice</span> thinning and a decrease in the number of earthquakes and seismic rate associated with <span class="hlt">ice</span> thickening. These results support the hypothesis that <span class="hlt">ice</span> <span class="hlt">mass</span> changes can modulate the background seismic rate. During the last century, wastage of the coastal glaciers in the Icy Bay and Malaspina region indicates thinning of hundreds of meters and in areas of major retreat, maximum losses of <span class="hlt">ice</span> thickness approaching 1 km. Between the 1899 Yakataga and Yakutat earthquakes ( Mw=8.1, 8.1) and prior to the 1979 St. Elias earthquake ( Ms=7.2), the plate interface below Icy Bay was locked and tectonic strain accumulated. We used estimated <span class="hlt">ice</span> <span class="hlt">mass</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70026696','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70026696"><span>Glacier <span class="hlt">ice</span> <span class="hlt">mass</span> fluctuations and fault instability in tectonically active Southern Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Sauber, J.M.; Molnia, B.F.</p> <p>2004-01-01</p> <p>Across the plate boundary zone in south central Alaska, tectonic strain rates are high in a region that includes large glaciers undergoing wastage (glacier retreat and thinning) and surges. For the coastal region between the Bering and Malaspina Glaciers, the average <span class="hlt">ice</span> <span class="hlt">mass</span> thickness changes between 1995 and 2000 range from 1 to 5 m/year. These <span class="hlt">ice</span> changes caused solid Earth displacements in our study region with predicted values of -10 to 50 mm in the vertical and predicted horizontal displacements of 0-10 mm at variable orientations. Relative to stable North America, observed horizontal rates of tectonic deformation range from 10 to 40 mm/year to the north-northwest and the predicted tectonic uplift rates range from approximately 0 mm/year near the Gulf of Alaska coast to 12 mm/year further inland. The <span class="hlt">ice</span> <span class="hlt">mass</span> changes between 1995 and 2000 resulted in discernible changes in the Global Positioning System (GPS) measured station positions of one site (ISLE) located adjacent to the Bagley <span class="hlt">Ice</span> Valley and at one site, DON, located south of the Bering Glacier terminus. In addition to modifying the surface displacements rates, we evaluated the influence <span class="hlt">ice</span> changes during the Bering glacier surge cycle had on the background seismic rate. We found an increase in the number of earthquakes (ML???2.5) and seismic rate associated with <span class="hlt">ice</span> thinning and a decrease in the number of earthquakes and seismic rate associated with <span class="hlt">ice</span> thickening. These results support the hypothesis that <span class="hlt">ice</span> <span class="hlt">mass</span> changes can modulate the background seismic rate. During the last century, wastage of the coastal glaciers in the Icy Bay and Malaspina region indicates thinning of hundreds of meters and in areas of major retreat, maximum losses of <span class="hlt">ice</span> thickness approaching 1 km. Between the 1899 Yakataga and Yakutat earthquakes (Mw=8.1, 8.1) and prior to the 1979 St. Elias earthquake (M s=7.2), the plate interface below Icy Bay was locked and tectonic strain accumulated. We used estimated <span class="hlt">ice</span> <span class="hlt">mass</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70045523','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70045523"><span>Shifting <span class="hlt">balance</span> of thermokarst lake <span class="hlt">ice</span> regimes across the Arctic Coastal Plain of northern Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Arp, Christopher D.; Jones, Benjamin M.; Lu, Zong; Whitman, Matthew S.</p> <p>2012-01-01</p> <p>The <span class="hlt">balance</span> of thermokarst lakes with bedfast- and floating-<span class="hlt">ice</span> regimes across Arctic lowlands regulates heat storage, permafrost thaw, winter-water supply, and over-wintering aquatic habitat. Using a time-series of late-winter synthetic aperture radar (SAR) imagery to distinguish lake <span class="hlt">ice</span> regimes in two regions of the Arctic Coastal Plain of northern Alaska from 2003–2011, we found that 18% of the lakes had intermittent <span class="hlt">ice</span> regimes, varying between bedfast-<span class="hlt">ice</span> and floating-<span class="hlt">ice</span> conditions. Comparing this dataset with a radar-based lake classification from 1980 showed that 16% of the bedfast-<span class="hlt">ice</span> lakes had shifted to floating-<span class="hlt">ice</span> regimes. A simulated lake <span class="hlt">ice</span> thinning trend of 1.5 cm/yr since 1978 is believed to be the primary factor driving this form of lake change. The most profound impacts of this regime shift in Arctic lakes may be an increase in the landscape-scale thermal offset created by additional lake heat storage and its role in talik development in otherwise continuous permafrost as well as increases in over-winter aquatic habitat and winter-water supply.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980020838','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980020838"><span>Micromechanical Oscillating <span class="hlt">Mass</span> <span class="hlt">Balance</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Altemir, David A. (Inventor)</p> <p>1997-01-01</p> <p>A micromechanical oscillating <span class="hlt">mass</span> <span class="hlt">balance</span> and method adapted for measuring minute quantities of material deposited at a selected location, such as during a vapor deposition process. The invention comprises a vibratory composite beam which includes a dielectric layer sandwiched between two conductive layers. The beam is positioned in a magnetic field. An alternating current passes through one conductive layers, the beam oscillates, inducing an output current in the second conductive layer, which is analyzed to determine the resonant frequency of the beam. As material is deposited on the beam, the <span class="hlt">mass</span> of the beam increases and the resonant frequency of the beam shifts, and the <span class="hlt">mass</span> added is determined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016CSR...118..154S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016CSR...118..154S"><span>Surface water <span class="hlt">mass</span> composition changes captured by cores of Arctic land-fast sea <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, I. J.; Eicken, H.; Mahoney, A. R.; Van Hale, R.; Gough, A. J.; Fukamachi, Y.; Jones, J.</p> <p>2016-04-01</p> <p>In the Arctic, land-fast sea <span class="hlt">ice</span> growth can be influenced by fresher water from rivers and residual summer melt. This paper examines a method to reconstruct changes in water <span class="hlt">masses</span> using oxygen isotope measurements of sea <span class="hlt">ice</span> cores. To determine changes in sea water isotope composition over the course of the <span class="hlt">ice</span> growth period, the output of a sea <span class="hlt">ice</span> thermodynamic model (driven with reanalysis data, observations of snow depth, and freeze-up dates) is used along with sea <span class="hlt">ice</span> oxygen isotope measurements and an isotopic fractionation model. Direct measurements of sea <span class="hlt">ice</span> growth rates are used to validate the output of the sea <span class="hlt">ice</span> growth model. It is shown that for sea <span class="hlt">ice</span> formed during the 2011/2012 <span class="hlt">ice</span> growth season at Barrow, Alaska, large changes in isotopic composition of the ocean waters were captured by the sea <span class="hlt">ice</span> isotopic composition. Salinity anomalies in the ocean were also tracked by moored instruments. These data indicate episodic advection of meteoric water, having both lower salinity and lower oxygen isotopic composition, during the winter sea <span class="hlt">ice</span> growth season. Such advection of meteoric water during winter is surprising, as no surface meltwater and no local river discharge should be occurring at this time of year in that area. How accurately changes in water <span class="hlt">masses</span> as indicated by oxygen isotope composition can be reconstructed using oxygen isotope analysis of sea <span class="hlt">ice</span> cores is addressed, along with methods/strategies that could be used to further optimize the results. The method described will be useful for winter detection of meteoric water presence in Arctic fast <span class="hlt">ice</span> regions, which is important for climate studies in a rapidly changing Arctic. Land-fast sea <span class="hlt">ice</span> effective fractionation coefficients were derived, with a range of +1.82‰ to +2.52‰. Those derived effective fractionation coefficients will be useful for future water <span class="hlt">mass</span> component proportion calculations. In particular, the equations given can be used to inform choices made when</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080030107&hterms=BALANCE+SHEET&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DBALANCE%2BSHEET','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080030107&hterms=BALANCE+SHEET&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DBALANCE%2BSHEET"><span>Recent <span class="hlt">Ice</span> Sheet and Glacier Elevation Changes in Greenland from Aircraft Laser Altimetry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Krabill, William B.; Thomas, R.; Sonntag, J.; Manizade, S.; Yungel, J.</p> <p>2008-01-01</p> <p>The Arctic <span class="hlt">Ice</span> Mapping group (Project AIM) at the NASA Goddard Space Flight Center Wallops Flight Facility has been conducting systematic topographic surveys of the Greenland <span class="hlt">Ice</span> Sheet (GIS) since 1993, using scanning airborne laser altimeters combined with Global Positioning System (UPS) technology. Earlier surveys showed the <span class="hlt">ice</span> sheet above 2000-rn elevation to be in <span class="hlt">balance</span>, but with localized regions of thickening or thinning. Thinning predominates at lower elevations and thinning rates have recently increased, resulting in a negative <span class="hlt">mass</span> <span class="hlt">balance</span> for the entire <span class="hlt">ice</span> sheet. Recently, critical segments of near-coastal flight lines in Greenland were resurveyed. Results from the new data will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140009622','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140009622"><span>Insights into Spatial Sensitivities of <span class="hlt">Ice</span> <span class="hlt">Mass</span> Response to Environmental Change from the SeaRISE <span class="hlt">Ice</span> Sheet Modeling Project I: Antarctica</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nowicki, Sophie; Bindschadler, Robert A.; Abe-Ouchi, Ayako; Aschwanden, Andy; Bueler, Ed; Choi, Hyengu; Fastook, Jim; Granzow, Glen; Greve, Ralf; Gutowski, Gail; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20140009622'); toggleEditAbsImage('author_20140009622_show'); toggleEditAbsImage('author_20140009622_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20140009622_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20140009622_hide"></p> <p>2013-01-01</p> <p>Atmospheric, oceanic, and subglacial forcing scenarios from the Sea-level Response to <span class="hlt">Ice</span> Sheet Evolution (SeaRISE) project are applied to six three-dimensional thermomechanical <span class="hlt">ice</span>-sheet models to assess Antarctic <span class="hlt">ice</span> sheet sensitivity over a 500 year timescale and to inform future modeling and field studies. Results indicate (i) growth with warming, except within low-latitude basins (where inland thickening is outpaced by marginal thinning); (ii) <span class="hlt">mass</span> loss with enhanced sliding (with basins dominated by high driving stresses affected more than basins with low-surface-slope streaming <span class="hlt">ice</span>); and (iii) <span class="hlt">mass</span> loss with enhanced <span class="hlt">ice</span> shelf melting (with changes in West Antarctica dominating the signal due to its marine setting and extensive <span class="hlt">ice</span> shelves; cf. minimal impact in the Terre Adelie, George V, Oates, and Victoria Land region of East Antarctica). <span class="hlt">Ice</span> loss due to dynamic changes associated with enhanced sliding and/or sub-shelf melting exceeds the gain due to increased precipitation. Furthermore, differences in results between and within basins as well as the controlling impact of sub-shelf melting on <span class="hlt">ice</span> dynamics highlight the need for improved understanding of basal conditions, grounding-zone processes, ocean-<span class="hlt">ice</span> interactions, and the numerical representation of all three.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.4454P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.4454P"><span>Breaking Off of Large <span class="hlt">Ice</span> <span class="hlt">Masses</span> From Hanging Glaciers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pralong, A.; Funk, M.</p> <p></p> <p>In order to reduce damage to settlements or other installations (roads, railway, etc) and avoid loss of life, a forecast of the final failure time of <span class="hlt">ice</span> <span class="hlt">masses</span> is required. At present, the most promising approach for such a prediction is based on the regularity by which certain large <span class="hlt">ice</span> <span class="hlt">masses</span> accelerate prior to the instant of collapse. The lim- itation of this forecast lies in short-term irregularities and in the difficulties to obtain sufficiently accurate data. A better physical understanding of the breaking off process is required, in order to improve the forecasting method. Previous analyze has shown that a stepwise crack extension coupling with a viscous flow leads to the observed acceleration function. We propose another approach by considering a local damage evolution law (gener- alized Kachanow's law) coupled with Glen's flow law to simulate the spatial evolu- tion of damage in polycristalline <span class="hlt">ice</span>, using a finite element computational model. The present study focuses on the transition from a diffuse to a localised damage reparti- tion occurring during the damage evolution. The influence of inhomogeneous initial conditions (inhomogeneity of the mechanical properties of <span class="hlt">ice</span>, damage inhomogene- ity) and inhomogeneous boundary conditions on the damage repartition are especially investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1815224A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1815224A"><span>Numerical modeling of Drangajökull <span class="hlt">Ice</span> Cap, NW Iceland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anderson, Leif S.; Jarosch, Alexander H.; Flowers, Gwenn E.; Aðalgeirsdóttir, Guðfinna; Magnússon, Eyjólfur; Pálsson, Finnur; Muñoz-Cobo Belart, Joaquín; Þorsteinsson, Þorsteinn; Jóhannesson, Tómas; Sigurðsson, Oddur; Harning, David; Miller, Gifford H.; Geirsdóttir, Áslaug</p> <p>2016-04-01</p> <p>Over the past century the Arctic has warmed twice as fast as the global average. This discrepancy is likely due to feedbacks inherent to the Arctic climate system. These Arctic climate feedbacks are currently poorly quantified, but are essential to future climate predictions based on global circulation modeling. Constraining the magnitude and timing of past Arctic climate changes allows us to test climate feedback parameterizations at different times with different boundary conditions. Because Holocene Arctic summer temperature changes have been largest in the North Atlantic (Kaufman et al., 2004) we focus on constraining the paleoclimate of Iceland. Glaciers are highly sensitive to changes in temperature and precipitation amount. This sensitivity allows for the estimation of paleoclimate using glacier models, modern glacier <span class="hlt">mass</span> <span class="hlt">balance</span> data, and past glacier extents. We apply our model to the Drangajökull <span class="hlt">ice</span> cap (~150 sq. km) in NW Iceland. Our numerical model is resolved in two-dimensions, conserves <span class="hlt">mass</span>, and applies the shallow-<span class="hlt">ice</span>-approximation. The bed DEM used in the model runs was constructed from radio echo data surveyed in spring 2014. We constrain the modern surface <span class="hlt">mass</span> <span class="hlt">balance</span> of Drangajökull using: 1) ablation and accumulation stakes; 2) <span class="hlt">ice</span> surface digital elevation models (DEMs) from satellite, airborne LiDAR, and aerial photographs; and 3) full-stokes model-derived vertical <span class="hlt">ice</span> velocities. The modeled vertical <span class="hlt">ice</span> velocities and <span class="hlt">ice</span> surface DEMs are combined to estimate past surface <span class="hlt">mass</span> <span class="hlt">balance</span>. We constrain Holocene glacier geometries using moraines and trimlines (e.g., Brynjolfsson, etal, 2014), proglacial-lake cores, and radiocarbon-dated dead vegetation emerging from under the modern glacier. We present a sensitivity analysis of the model to changes in parameters and show the effect of step changes of temperature and precipitation on glacier extent. Our results are placed in context with local lacustrine and marine climate proxies as well</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28116688','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28116688"><span>Spatiotemporal variability in surface energy <span class="hlt">balance</span> across tundra, snow and <span class="hlt">ice</span> in Greenland.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lund, Magnus; Stiegler, Christian; Abermann, Jakob; Citterio, Michele; Hansen, Birger U; van As, Dirk</p> <p>2017-02-01</p> <p>The surface energy <span class="hlt">balance</span> (SEB) is essential for understanding the coupled cryosphere-atmosphere system in the Arctic. In this study, we investigate the spatiotemporal variability in SEB across tundra, snow and <span class="hlt">ice</span>. During the snow-free period, the main energy sink for <span class="hlt">ice</span> sites is surface melt. For tundra, energy is used for sensible and latent heat flux and soil heat flux leading to permafrost thaw. Longer snow-free period increases melting of the Greenland <span class="hlt">Ice</span> Sheet and glaciers and may promote tundra permafrost thaw. During winter, clouds have a warming effect across surface types whereas during summer clouds have a cooling effect over tundra and a warming effect over <span class="hlt">ice</span>, reflecting the spatial variation in albedo. The complex interactions between factors affecting SEB across surface types remain a challenge for understanding current and future conditions. Extended monitoring activities coupled with modelling efforts are essential for assessing the impact of warming in the Arctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C23C0798L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C23C0798L"><span>How much can Greenland melt? An upper bound on <span class="hlt">mass</span> loss from the Greenland <span class="hlt">Ice</span> Sheet through surface melting</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, X.; Bassis, J. N.</p> <p>2015-12-01</p> <p>With observations showing accelerated <span class="hlt">mass</span> loss from the Greenland <span class="hlt">Ice</span> Sheet due to surface melt, the Greenland <span class="hlt">Ice</span> Sheet is becoming one of the most significant contributors to sea level rise. The contribution of the Greenland <span class="hlt">Ice</span> Sheet o sea level rise is likely to accelerate in the coming decade and centuries as atmospheric temperatures continue to rise, potentially triggering ever larger surface melt rates. However, at present considerable uncertainty remains in projecting the contribution to sea level of the Greenland <span class="hlt">Ice</span> Sheet both due to uncertainty in atmospheric forcing and the <span class="hlt">ice</span> sheet response to climate forcing. Here we seek an upper bound on the contribution of surface melt from the Greenland to sea level rise in the coming century using a surface energy <span class="hlt">balance</span> model coupled to an englacial model. We use IPCC Representative Concentration Pathways (RCP8.5, RCP6, RCP4.5, RCP2.6) climate scenarios from an ensemble of global climate models in our simulations to project the maximum rate of <span class="hlt">ice</span> volume loss and related sea-level rise associated with surface melting. To estimate the upper bound, we assume the Greenland <span class="hlt">Ice</span> Sheet is perpetually covered in thick clouds, which maximize longwave radiation to the <span class="hlt">ice</span> sheet. We further assume that deposition of black carbon darkens the <span class="hlt">ice</span> substantially turning it nearly black, substantially reducing its albedo. Although assuming that all melt water not stored in the snow/firn is instantaneously transported off the <span class="hlt">ice</span> sheet increases <span class="hlt">mass</span> loss in the short term, refreezing of retained water warms the <span class="hlt">ice</span> and may lead to more melt in the long term. Hence we examine both assumptions and use the scenario that leads to the most surface melt by 2100. Preliminary models results suggest that under the most aggressive climate forcing, surface melt from the Greenland <span class="hlt">Ice</span> Sheet contributes ~1 m to sea level by the year 2100. This is a significant contribution and ignores dynamic effects. We also examined a lower bound</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.4979G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.4979G"><span>Modelling The Energy And <span class="hlt">Mass</span> <span class="hlt">Balance</span> Of A Black Glacier</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grossi, G.; Taschner, S.; Ranzi, R.</p> <p></p> <p>A distributed energy <span class="hlt">balance</span> hydrologic model has been implemented to simulate the melting season of the Belvedere glacier, situated in the Anza river basin (North- Western Italy) for a few years. The Belvedere Glacier is an example of SblackS glacier, ´ since the ablation zone is covered by a significant debris layer. The glacierSs termi- nus has an altitude of 1785 m asl which is very unusual for the Southern side of the European Alps. The model accounts for the energy exchange processes at the inter- face between the atmospheric boundary layer and the snow/<span class="hlt">ice</span>/debris layer. To run the model hydrometeorological and physiographic data were collected, including the depth of the debris cover and the tritium (3H) concentration in the glacial river. Mea- surements of the soil thermal conductivity were carried out during a field campaign organised within the glaciers monitoring GLIMS project, at the time of the passage of the Landsat and the Terra satellites last 15 August 2001. A comparison of the different energy terms simulated by the model assigns a dominant role to the shortwave radia- tion, which provides the highest positive contribution to the energy available for snow- and <span class="hlt">ice</span>-melt, while the sensible heat turns out to be the second major source of heat. Longwave radiation <span class="hlt">balance</span> and latent heat seem to be less relevant and often nega- tive. The role of the debris cover is not negligible, since its thermal insulation causes, on average, a decrease in the <span class="hlt">ice</span> melt volume. One of the model variables is the tem- perature of the debris cover, which can be a useful information when a black glacier is to be monitored through remote sensing techniques. The visible and near infrared radi- ation data do not always provide sufficient information to detect the glaciers' margins beneath the debris layer. For this reason the information of the different thermal sur- face characteristics (pure <span class="hlt">ice</span>, debris covered <span class="hlt">ice</span>, rock), proved by the energy <span class="hlt">balance</span> model results was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1914046W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1914046W"><span>Bayesian inference of <span class="hlt">ice</span> thickness from remote-sensing data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Werder, Mauro A.; Huss, Matthias</p> <p>2017-04-01</p> <p>Knowledge about <span class="hlt">ice</span> thickness and volume is indispensable for studying <span class="hlt">ice</span> dynamics, future sea-level rise due to glacier melt or their contribution to regional hydrology. Accurate measurements of glacier thickness require on-site work, usually employing radar techniques. However, these field measurements are time consuming, expensive and sometime downright impossible. Conversely, measurements of the <span class="hlt">ice</span> surface, namely elevation and flow velocity, are becoming available world-wide through remote sensing. The model of Farinotti et al. (2009) calculates <span class="hlt">ice</span> thicknesses based on a <span class="hlt">mass</span> conservation approach paired with shallow <span class="hlt">ice</span> physics using estimates of the surface <span class="hlt">mass</span> <span class="hlt">balance</span>. The presented work applies a Bayesian inference approach to estimate the parameters of a modified version of this forward model by fitting it to both measurements of surface flow speed and of <span class="hlt">ice</span> thickness. The inverse model outputs <span class="hlt">ice</span> thickness as well the distribution of the error. We fit the model to ten test glaciers and <span class="hlt">ice</span> caps and quantify the improvements of thickness estimates through the usage of surface <span class="hlt">ice</span> flow measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11.1913F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11.1913F"><span>From cyclic <span class="hlt">ice</span> streaming to Heinrich-like events: the grow-and-surge instability in the Parallel <span class="hlt">Ice</span> Sheet Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Feldmann, Johannes; Levermann, Anders</p> <p>2017-08-01</p> <p>Here we report on a cyclic, physical <span class="hlt">ice</span>-discharge instability in the Parallel <span class="hlt">Ice</span> Sheet Model, simulating the flow of a three-dimensional, inherently buttressed <span class="hlt">ice</span>-sheet-shelf system which periodically surges on a millennial timescale. The thermomechanically coupled model on 1 km horizontal resolution includes an enthalpy-based formulation of the thermodynamics, a nonlinear stress-<span class="hlt">balance</span>-based sliding law and a very simple subglacial hydrology. The simulated unforced surging is characterized by rapid <span class="hlt">ice</span> streaming through a bed trough, resulting in abrupt discharge of <span class="hlt">ice</span> across the grounding line which is eventually calved into the ocean. We visualize the central feedbacks that dominate the subsequent phases of <span class="hlt">ice</span> buildup, surge and stabilization which emerge from the interaction between <span class="hlt">ice</span> dynamics, thermodynamics and the subglacial till layer. Results from the variation of surface <span class="hlt">mass</span> <span class="hlt">balance</span> and basal roughness suggest that <span class="hlt">ice</span> sheets of medium thickness may be more susceptible to surging than relatively thin or thick ones for which the surge feedback loop is damped. We also investigate the influence of different basal sliding laws (ranging from purely plastic to nonlinear to linear) on possible surging. The presented mechanisms underlying our simulations of self-maintained, periodic <span class="hlt">ice</span> growth and destabilization may play a role in large-scale <span class="hlt">ice</span>-sheet surging, such as the surging of the Laurentide <span class="hlt">Ice</span> Sheet, which is associated with Heinrich events, and <span class="hlt">ice</span>-stream shutdown and reactivation, such as observed in the Siple Coast region of West Antarctica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1358439','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1358439"><span>High resolution (1 km) positive degree-day modelling of Greenland <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> <span class="hlt">balance</span>, 1870–2012 using reanalysis data</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Wilton, David J.; Jowett, Amy; Hanna, Edward</p> <p></p> <p>Here, we show results from a positive degree-day (PDD) model of Greenland <span class="hlt">ice</span> sheet (GrIS) surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB), 1870–2012, forced with reanalysis data. The model includes an improved daily temperature parameterization as compared with a previous version and is run at 1 km rather than 5 km resolution. The improvements lead overall to higher SMB with the same forcing data. We also compare our model with results from two regional climate models (RCMs). While there is good qualitative agreement between our PDD model and the RCMs, it usually results in lower precipitation and lower runoff but approximately equivalent SMB:more » mean 1979–2012 SMB (± standard deviation), in Gt a –1, is 382 ± 78 in the PDD model, compared with 379 ± 101 and 425 ± 90 for the RCMs. Comparison with in situ SMB observations suggests that the RCMs may be more accurate than PDD at local level, in some areas, although the latter generally compares well. Dividing the GrIS into seven drainage basins we show that SMB has decreased sharply in all regions since 2000. Finally we show correlation between runoff close to two calving glaciers and either calving front retreat or calving flux, this being most noticeable from the mid-1990s.« less</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1358439-high-resolution-km-positive-degree-day-modelling-greenland-ice-sheet-surface-mass-balance-using-reanalysis-data','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1358439-high-resolution-km-positive-degree-day-modelling-greenland-ice-sheet-surface-mass-balance-using-reanalysis-data"><span>High resolution (1 km) positive degree-day modelling of Greenland <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> <span class="hlt">balance</span>, 1870–2012 using reanalysis data</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Wilton, David J.; Jowett, Amy; Hanna, Edward; ...</p> <p>2016-12-15</p> <p>Here, we show results from a positive degree-day (PDD) model of Greenland <span class="hlt">ice</span> sheet (GrIS) surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB), 1870–2012, forced with reanalysis data. The model includes an improved daily temperature parameterization as compared with a previous version and is run at 1 km rather than 5 km resolution. The improvements lead overall to higher SMB with the same forcing data. We also compare our model with results from two regional climate models (RCMs). While there is good qualitative agreement between our PDD model and the RCMs, it usually results in lower precipitation and lower runoff but approximately equivalent SMB:more » mean 1979–2012 SMB (± standard deviation), in Gt a –1, is 382 ± 78 in the PDD model, compared with 379 ± 101 and 425 ± 90 for the RCMs. Comparison with in situ SMB observations suggests that the RCMs may be more accurate than PDD at local level, in some areas, although the latter generally compares well. Dividing the GrIS into seven drainage basins we show that SMB has decreased sharply in all regions since 2000. Finally we show correlation between runoff close to two calving glaciers and either calving front retreat or calving flux, this being most noticeable from the mid-1990s.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C41A0693Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C41A0693Z"><span>Time Series of Greenland <span class="hlt">Ice</span>-Sheet Elevations and <span class="hlt">Mass</span> Changes from ICESat 2003-2009</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zwally, H. J.; Li, J.; Medley, B.; Robbins, J. W.; Yi, D.</p> <p>2015-12-01</p> <p>We follow the repeat-track analysis (RTA) of ICESat surface-elevation data by a second stage that adjusts the measured elevations on repeat passes to the reference track taking into account the cross-track slope (αc), in order to construct elevation time series. αc are obtained from RTA simultaneous solutions for αc, dh/dt, and h0. The height measurements on repeat tracks are initially interpolated to uniform along-track reference points (every 172 m) and times (ti) giving the h(xi,ti) used in the RTA solutions. The xi are the cross-track spacings from the reference track and i is the laser campaign index. The adjusted elevation measurements at the along-track reference points are hr(ti) = h(xi,ti) - xi tan(αc) - h0. The hr(ti) time series are averaged over 50 km cells creating H(ti) series and further averaged (weighted by cell area) to H(t) time series over drainage systems (DS), elevation bands, regions, and the entire <span class="hlt">ice</span> sheet. Temperature-driven changes in the rate of firn compaction, CT(t), are calculated for 50 km cells with our firn-compaction model giving I(t) = H(t) - CT(t) - B(t) where B(t) is the vertical motion of the bedrock. During 2003 to 2009, the average dCT(t)/dt in the accumulation zone is -5 cm/yr, which amounts to a -75 km3/yr correction to <span class="hlt">ice</span> volume change estimates. The I(t) are especially useful for studying the seasonal cycle of <span class="hlt">mass</span> gains and losses and interannual variations. The H(t) for the ablation zone are fitted with a multi-variate function with a linear component describing the upward component of <span class="hlt">ice</span> flow plus winter accumulation (fall through spring) and a portion of a sine function describing the superimposed summer melting. During fall to spring the H(t) indicate that the upward motion of the <span class="hlt">ice</span> flow is at a rate of 1 m/yr, giving an annual <span class="hlt">mass</span> gain of 180 Gt/yr in the ablation zone. The summer loss from surface melting in the high-melt summer of 2005 is 350 Gt/yr, giving a net surface loss of 170 Gt/yr from the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870027099&hterms=microwaves+water+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmicrowaves%2Bwater%2Bstructure','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870027099&hterms=microwaves+water+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmicrowaves%2Bwater%2Bstructure"><span>Satellite microwave and in situ observations of the Weddell Sea <span class="hlt">ice</span> cover and its marginal <span class="hlt">ice</span> zone</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, J. C.; Sullivan, C. W.</p> <p>1986-01-01</p> <p>The radiative and physical characteristics of the Weddell Sea <span class="hlt">ice</span> cover and its marginal <span class="hlt">ice</span> zone are analyzed using multichannel satellite passive microwave data and ship and helicopter observations obtained during the 1983 Antarctic Marine Ecosystem Research. Winter and spring brightness temperatures are examined; spatial variability in the brightness temperatures of consolidated <span class="hlt">ice</span> in winter and spring cyclic increases and decrease in brightness temperatures of consolidated <span class="hlt">ice</span> with an amplitude of 50 K at 37 GHz and 20 K at 18 GHz are observed. The roles of variations in air temperature and surface characteristics in the variability of spring brightness temperatures are investigated. <span class="hlt">Ice</span> concentrations are derived using the frequency and polarization techniques, and the data are compared with the helicopter and ship observations. Temporal changes in the <span class="hlt">ice</span> margin structure and the <span class="hlt">mass</span> <span class="hlt">balance</span> of fresh water and of biological features of the marginal <span class="hlt">ice</span> zone are studied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.G42A..02J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.G42A..02J"><span>Towards Estimate of Present Day <span class="hlt">Ice</span> Melting in Polar Regions From Altimetry, Gravity, Ocean Bottom Pressure and GPS Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiang, Y.; Wu, X.; van den Broeke, M. R.; Munneke, P. K.; Simonsen, S. B.; van der Wal, W.; Vermeersen, B. L.</p> <p>2013-12-01</p> <p>The <span class="hlt">ice</span> sheet in Polar Regions stores the largest freshwater bodies on Earth, sufficient to elevate global sea level by more than 65 meters if melted. The earth may have entered an intensive <span class="hlt">ice</span>-melting episode, possibly due to anthropogenic global warming rather than natural orbit variations. Determining present-day <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>, however, is complicated by the fact that most observations contain both present day <span class="hlt">ice</span> melting signal and residual signals from past glacier melting. Despite decades of progress in geodynamic modeling and new observations, significant uncertainties remain in both. The key to separate present-day <span class="hlt">ice</span> <span class="hlt">mass</span> change and signals from past melting is to include data of different physical characteristics. We conducted a new global kinematic inversion scheme to estimate both present-day <span class="hlt">ice</span> melting and past glacier signatures simultaneously and assess their contribution to current and future global mean sea level change. Our approach is designed to invert and separate present-day melting signal in the spherical harmonic domain using a globally distributed interdisciplinary data with distinct physical information. Interesting results with unprecedented precisions have been achieved so far. We will present our results of the estimated present-day <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> trend in both Greenland and Antarctica <span class="hlt">ice</span> sheet as well as other regions where significant <span class="hlt">mass</span> change occurs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C51B0713H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C51B0713H"><span>Probability based hydrologic catchments of the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hudson, B. D.</p> <p>2015-12-01</p> <p>Greenland <span class="hlt">Ice</span> Sheet melt water impacts <span class="hlt">ice</span> sheet flow dynamics, fjord and coastal circulation, and sediment and biogeochemical fluxes. Melt water exiting the <span class="hlt">ice</span> sheet also is a key term in its <span class="hlt">mass</span> <span class="hlt">balance</span>. Because of this, knowledge of the area of the <span class="hlt">ice</span> sheet that contributes melt water to a given outlet (its hydrologic catchment) is important to many <span class="hlt">ice</span> sheet studies and is especially critical to methods using river runoff to assess <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span>. Yet uncertainty in delineating <span class="hlt">ice</span> sheet hydrologic catchments is a problem that is rarely acknowledged. <span class="hlt">Ice</span> sheet catchments are delineated as a function of both basal and surface topography. While surface topography is well known, basal topography is less certain because it is dependent on radar surveys. Here, I a present a Monte Carlo based approach to delineating <span class="hlt">ice</span> sheet catchments that quantifies the impact of uncertain basal topography. In this scheme, over many iterations I randomly vary the <span class="hlt">ice</span> sheet bed elevation within published error bounds (using Morlighem et al., 2014 bed and bed error datasets). For each iteration of <span class="hlt">ice</span> sheet bed elevation, I calculate the hydraulic potentiometric surface and route water over its path of 'steepest' descent to delineate the catchment. I then use all realizations of the catchment to arrive at a probability map of all major melt water outlets in Greenland. I often find that catchment size is uncertain, with small, random perturbations in basal topography leading to large variations in catchments size. While some catchments are well defined, others can double or halve in size within published basal topography error bars. While some uncertainty will likely always remain, this work points to locations where studies of <span class="hlt">ice</span> sheet hydrology would be the most successful, allows reinterpretation of past results, and points to where future radar surveys would be most advantageous.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.G53A..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.G53A..01S"><span>Asia High Mountain Glacier <span class="hlt">Mass</span> <span class="hlt">Balance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shum, C. K.; Su, X.; Shang, K.; Cogley, J. G.; Zhang, G.; Howat, I. M.; Braun, A.; Kuo, C. Y.</p> <p>2015-12-01</p> <p>The Asian High Mountain encompassing the Qinghai-Tibetan Plateau has the largest glaciated regions in the world outside of Greenland and Antarctica. The Tibetan Plateau is the source or headwater of many major river systems, which provide water resources to more than a billion people downstream. The impact of climate change on the Tibetan Plateau physical processes, including mountain glacier wastage, permafrost active layer thickening, the timing and the quantity of the perennial snowpack melt affecting upstream catchments, river runoffs, land-use, have significant effects on downstream water resources. Exact quantification of the Asian High Mountain glacier wastage or its <span class="hlt">mass</span> <span class="hlt">balance</span> on how much of the melt water contributes to early 21st century global sea-level rise, remain illusive or the published results are arguably controversial. The recent observed significant increase of freshwater storage within the Tibetan Plateaus remains a limitation to exactly quantify mountain glacier wastage. Here, we provide an updated estimate of Asia high mountain glacier <span class="hlt">mass</span> <span class="hlt">balance</span> using satellite geodetic observations during the last decade, accounting for the hydrologic and other processes, and validated against available in situ <span class="hlt">mass</span> <span class="hlt">balance</span> data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26912699','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26912699"><span>Holocene deceleration of the Greenland <span class="hlt">Ice</span> Sheet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>MacGregor, Joseph A; Colgan, William T; Fahnestock, Mark A; Morlighem, Mathieu; Catania, Ginny A; Paden, John D; Gogineni, S Prasad</p> <p>2016-02-05</p> <p>Recent peripheral thinning of the Greenland <span class="hlt">Ice</span> Sheet is partly offset by interior thickening and is overprinted on its poorly constrained Holocene evolution. On the basis of the <span class="hlt">ice</span> sheet's radiostratigraphy, <span class="hlt">ice</span> flow in its interior is slower now than the average speed over the past nine millennia. Generally higher Holocene accumulation rates relative to modern estimates can only partially explain this millennial-scale deceleration. The <span class="hlt">ice</span> sheet's dynamic response to the decreasing proportion of softer <span class="hlt">ice</span> from the last glacial period and the deglacial collapse of the <span class="hlt">ice</span> bridge across Nares Strait also contributed to this pattern. Thus, recent interior thickening of the Greenland <span class="hlt">Ice</span> Sheet is partly an ongoing dynamic response to the last deglaciation that is large enough to affect interpretation of its <span class="hlt">mass</span> <span class="hlt">balance</span> from altimetry. Copyright © 2016, American Association for the Advancement of Science.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C23C..03S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C23C..03S"><span>Surface water hydrology and the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, L. C.; Yang, K.; Pitcher, L. H.; Overstreet, B. T.; Chu, V. W.; Rennermalm, A. K.; Cooper, M. G.; Gleason, C. J.; Ryan, J.; Hubbard, A.; Tedesco, M.; Behar, A.</p> <p>2016-12-01</p> <p><span class="hlt">Mass</span> loss from the Greenland <span class="hlt">Ice</span> Sheet now exceeds 260 Gt/year, raising global sea level by >0.7 mm annually. Approximately two-thirds of this total <span class="hlt">mass</span> loss is now driven by negative <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB), attributed mainly to production and runoff of meltwater from the <span class="hlt">ice</span> sheet surface. This new dominance of runoff as a driver of GrIS total <span class="hlt">mass</span> loss will likely persist owing to anticipated further increases in surface melting, reduced meltwater storage in firn, and the waning importance of dynamical <span class="hlt">mass</span> losses (<span class="hlt">ice</span> calving) as the <span class="hlt">ice</span> sheets retreat from their marine-terminating margins. It also creates the need and opportunity for integrative research pairing traditional surface water hydrology approaches with glaciology. As one example, we present a way to measure supraglacial "runoff" (i.e. specific discharge) at the supraglacial catchment scale ( 101-102 km2), using in situ measurements of supraglacial river discharge and high-resolution satellite/drone mapping of upstream catchment area. This approach, which is standard in terrestrial hydrology but novel for <span class="hlt">ice</span> sheet science, enables independent verification and improvement of modeled SMB runoff estimates used to project sea level rise. Furthermore, because current SMB models do not consider the role of fluvial watershed processes operating on the <span class="hlt">ice</span> surface, inclusion of even a simple surface routing model materially improves simulations of runoff delivered to moulins, the critical pathways for meltwater entry into the <span class="hlt">ice</span> sheet. Incorporating principles of surface water hydrology and fluvial geomorphology and into glaciological models will thus aid estimates of Greenland meltwater runoff to the global ocean as well as connections to subglacial hydrology and <span class="hlt">ice</span> sheet dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C23B0779C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C23B0779C"><span>Snow Climatology of Arctic Sea <span class="hlt">Ice</span>: Comparison of Reanalysis and Climate Model Data with In Situ Measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chevooruvalappil Chandran, B.; Pittana, M.; Haas, C.</p> <p>2015-12-01</p> <p>Snow on sea <span class="hlt">ice</span> is a critical and complex factor influencing sea <span class="hlt">ice</span> processes. Deep snow with a high albedo and low thermal conductivity inhibits <span class="hlt">ice</span> growth in winter and minimizes <span class="hlt">ice</span> loss in summer. Very shallow or absent snow promotes <span class="hlt">ice</span> growth in winter and <span class="hlt">ice</span> loss in summer. The timing of snow ablation critically impacts summer sea <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>. Here we assess the accuracy of various snow on sea <span class="hlt">ice</span> data products from reanalysis and modeling comparing them with in situ measurements. The latter are based on the Warren et al. (1999) monthly climatology derived from snow ruler measurements between 1954-1991, and on daily snow depth retrievals from few drifting <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> buoys (IMB) with sufficiently long observations spanning the summer season. These were compared with snow depth data from the National Center for Environmental Prediction Department of Energy Reanalysis 2 (NCEP), the Community Climate System Model 4 (CCSM4), and the Canadian Earth System Model 2 (CanESM2). Results are quite variable in different years and regions. However, there is often good agreement between CanESM2 and IMB snow depth during the winter accumulation and spring melt periods. Regional analyses show that over the western Arctic covered primarily with multiyear <span class="hlt">ice</span> NCEP snow depths are in good agreement with the Warren climatology while CCSM4 overestimates snow depth. However, in the Eastern Arctic which is dominated by first-year <span class="hlt">ice</span> the opposite behavior is observed. Compared to the Warren climatology CanESM2 underestimates snow depth in all regions. Differences between different snow depth products are as large as 10 to 20 cm, with large consequences for the sea <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>. However, it is also very difficult to evaluate the accuracy of reanalysis and model snow depths due to a lack of extensive, continuous in situ measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23925242','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23925242"><span>Insolation-driven 100,000-year glacial cycles and hysteresis of <span class="hlt">ice</span>-sheet volume.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Abe-Ouchi, Ayako; Saito, Fuyuki; Kawamura, Kenji; Raymo, Maureen E; Okuno, Jun'ichi; Takahashi, Kunio; Blatter, Heinz</p> <p>2013-08-08</p> <p>The growth and reduction of Northern Hemisphere <span class="hlt">ice</span> sheets over the past million years is dominated by an approximately 100,000-year periodicity and a sawtooth pattern (gradual growth and fast termination). Milankovitch theory proposes that summer insolation at high northern latitudes drives the glacial cycles, and statistical tests have demonstrated that the glacial cycles are indeed linked to eccentricity, obliquity and precession cycles. Yet insolation alone cannot explain the strong 100,000-year cycle, suggesting that internal climatic feedbacks may also be at work. Earlier conceptual models, for example, showed that glacial terminations are associated with the build-up of Northern Hemisphere 'excess <span class="hlt">ice</span>', but the physical mechanisms underpinning the 100,000-year cycle remain unclear. Here we show, using comprehensive climate and <span class="hlt">ice</span>-sheet models, that insolation and internal feedbacks between the climate, the <span class="hlt">ice</span> sheets and the lithosphere-asthenosphere system explain the 100,000-year periodicity. The responses of equilibrium states of <span class="hlt">ice</span> sheets to summer insolation show hysteresis, with the shape and position of the hysteresis loop playing a key part in determining the periodicities of glacial cycles. The hysteresis loop of the North American <span class="hlt">ice</span> sheet is such that after inception of the <span class="hlt">ice</span> sheet, its <span class="hlt">mass</span> <span class="hlt">balance</span> remains mostly positive through several precession cycles, whose amplitudes decrease towards an eccentricity minimum. The larger the <span class="hlt">ice</span> sheet grows and extends towards lower latitudes, the smaller is the insolation required to make the <span class="hlt">mass</span> <span class="hlt">balance</span> negative. Therefore, once a large <span class="hlt">ice</span> sheet is established, a moderate increase in insolation is sufficient to trigger a negative <span class="hlt">mass</span> <span class="hlt">balance</span>, leading to an almost complete retreat of the <span class="hlt">ice</span> sheet within several thousand years. This fast retreat is governed mainly by rapid ablation due to the lowered surface elevation resulting from delayed isostatic rebound, which is the lithosphere</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018RvGeo..56..142P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018RvGeo..56..142P"><span>Ocean Tide Influences on the Antarctic and Greenland <span class="hlt">Ice</span> Sheets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Padman, Laurie; Siegfried, Matthew R.; Fricker, Helen A.</p> <p>2018-03-01</p> <p>Ocean tides are the main source of high-frequency variability in the vertical and horizontal motion of <span class="hlt">ice</span> sheets near their marine margins. Floating <span class="hlt">ice</span> shelves, which occupy about three quarters of the perimeter of Antarctica and the termini of four outlet glaciers in northern Greenland, rise and fall in synchrony with the ocean tide. Lateral motion of floating and grounded portions of <span class="hlt">ice</span> sheets near their marine margins can also include a tidal component. These tide-induced signals provide insight into the processes by which the oceans can affect <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> and dynamics. In this review, we summarize in situ and satellite-based measurements of the tidal response of <span class="hlt">ice</span> shelves and grounded <span class="hlt">ice</span>, and spatial variability of ocean tide heights and currents around the <span class="hlt">ice</span> sheets. We review sensitivity of tide heights and currents as ocean geometry responds to variations in sea level, <span class="hlt">ice</span> shelf thickness, and <span class="hlt">ice</span> sheet <span class="hlt">mass</span> and extent. We then describe coupled <span class="hlt">ice</span>-ocean models and analytical glacier models that quantify the effect of ocean tides on lower-frequency <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss and motion. We suggest new observations and model developments to improve the representation of tides in coupled models that are used to predict future <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss and the associated contribution to sea level change. The most critical need is for new data to improve maps of bathymetry, <span class="hlt">ice</span> shelf draft, spatial variability of the drag coefficient at the <span class="hlt">ice</span>-ocean interface, and higher-resolution models with improved representation of tidal energy sinks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1918710V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1918710V"><span>A Transient Initialization Routine of the Community <span class="hlt">Ice</span> Sheet Model for the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van der Laan, Larissa; van den Broeke, Michiel; Noël, Brice; van de Wal, Roderik</p> <p>2017-04-01</p> <p>The Community <span class="hlt">Ice</span> Sheet Model (CISM) is to be applied in future simulations of the Greenland <span class="hlt">Ice</span> Sheet under a range of climate change scenarios, determining the sensitivity of the <span class="hlt">ice</span> sheet to individual climatic forcings. In order to achieve reliable results regarding <span class="hlt">ice</span> sheet stability and assess the probability of future occurrence of tipping points, a realistic initial <span class="hlt">ice</span> sheet geometry is essential. The current work describes and evaluates the development of a transient initialization routine, using NGRIP 18O isotope data to create a temperature anomaly field. Based on the latter, surface <span class="hlt">mass</span> <span class="hlt">balance</span> components runoff and precipitation are perturbed for the past 125k years. The precipitation and runoff fields originate from a downscaled 1 km resolution version of the regional climate model RACMO2.3 for the period 1961-1990. The result of the initialization routine is a present-day <span class="hlt">ice</span> sheet with a transient memory of the last glacial-interglacial cycle, which will serve as the future runs' initial condition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C11B0911H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C11B0911H"><span>Simulating <span class="hlt">ice</span> thickness and velocity evolution of Upernavik Isstrøm 1849-2017 with ISSM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haubner, K.; Box, J.; Schlegel, N.; Larour, E. Y.; Morlighem, M.; Solgaard, A.; Kjeldsen, K. K.; Larsen, S. H.; Rignot, E. J.; Dupont, T. K.; Kjaer, K. H.</p> <p>2017-12-01</p> <p>Tidewater terminus changes have a significant influence on glacier velocity and <span class="hlt">mass</span> <span class="hlt">balance</span> and impact therefore Greenland's <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>. Improving glacier front changes in <span class="hlt">ice</span> sheet models helps understanding the processes that are driving glacier <span class="hlt">mass</span> changes and improves predictions on Greenland's <span class="hlt">mass</span> loss. We use the level set based moving boundary capability (Bondzio et al., 2016) included in the <span class="hlt">Ice</span> Sheet System Model ISSM to reconstruct velocity and thickness changes on Upernavik Isstrøm, Greenland from 1849 to 2017. During the simulation, we use various data sets. For the model initialization, trim line data and an observed calving front position determine the shape of the <span class="hlt">ice</span> surface elevation. The terminus changes are prescribed by observations. Data sets like the GIMP DEM, ArcticDEM, <span class="hlt">Ice</span>Bridge surface elevation and <span class="hlt">ice</span> surface velocities from the ESA project CCI and NASA project MEaSUREs help evaluating the simulation performance. The simulation is sensitive to the prescribed terminus changes, showing an average acceleration along the three flow lines between 50% and 190% from 1849 to 2017. Simulated <span class="hlt">ice</span> surface velocity and elevation between 1990 and 2012 are within +/-20% of observations (GIMP, ArcticDEM, <span class="hlt">Ice</span>Bridge, CCI and MEaSUREs). Simulated <span class="hlt">mass</span> changes indicate increased dynamical <span class="hlt">ice</span> loss from 1932 onward, amplified by increased negative SMB anomalies after 1998. More detailed information about methods and findings can be found in Haubner et al., 2017 (in TC discussion, describing simulation results between 1849-2012). Future goals are the comparison of <span class="hlt">ice</span> surface velocity changes simulated with prescribed terminus retreat against other retreat schemes (Morlighem et al., 2016; Levermann et al., 2012; Bondzio et al., 2017) and applying the method onto other tidewater glaciers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14749827','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14749827"><span>Enhanced <span class="hlt">ice</span> sheet growth in Eurasia owing to adjacent <span class="hlt">ice</span>-dammed lakes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Krinner, G; Mangerud, J; Jakobsson, M; Crucifix, M; Ritz, C; Svendsen, J I</p> <p>2004-01-29</p> <p>Large proglacial lakes cool regional summer climate because of their large heat capacity, and have been shown to modify precipitation through mesoscale atmospheric feedbacks, as in the case of Lake Agassiz. Several large <span class="hlt">ice</span>-dammed lakes, with a combined area twice that of the Caspian Sea, were formed in northern Eurasia about 90,000 years ago, during the last glacial period when an <span class="hlt">ice</span> sheet centred over the Barents and Kara seas blocked the large northbound Russian rivers. Here we present high-resolution simulations with an atmospheric general circulation model that explicitly simulates the surface <span class="hlt">mass</span> <span class="hlt">balance</span> of the <span class="hlt">ice</span> sheet. We show that the main influence of the Eurasian proglacial lakes was a significant reduction of <span class="hlt">ice</span> sheet melting at the southern margin of the Barents-Kara <span class="hlt">ice</span> sheet through strong regional summer cooling over large parts of Russia. In our simulations, the summer melt reduction clearly outweighs lake-induced decreases in moisture and hence snowfall, such as has been reported earlier for Lake Agassiz. We conclude that the summer cooling mechanism from proglacial lakes accelerated <span class="hlt">ice</span> sheet growth and delayed <span class="hlt">ice</span> sheet decay in Eurasia and probably also in North America.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.3173N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.3173N"><span>New <span class="hlt">Mass</span>-Conserving Bedrock Topography for Pine Island Glacier Impacts Simulated Decadal Rates of <span class="hlt">Mass</span> Loss</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nias, I. J.; Cornford, S. L.; Payne, A. J.</p> <p>2018-04-01</p> <p>High-resolution <span class="hlt">ice</span> flow modeling requires bedrock elevation and <span class="hlt">ice</span> thickness data, consistent with one another and with modeled physics. Previous studies have shown that gridded <span class="hlt">ice</span> thickness products that rely on standard interpolation techniques (such as Bedmap2) can be inconsistent with the conservation of <span class="hlt">mass</span>, given observed velocity, surface elevation change, and surface <span class="hlt">mass</span> <span class="hlt">balance</span>, for example, near the grounding line of Pine Island Glacier, West Antarctica. Using the BISICLES <span class="hlt">ice</span> flow model, we compare results of simulations using both Bedmap2 bedrock and thickness data, and a new interpolation method that respects <span class="hlt">mass</span> conservation. We find that simulations using the new geometry result in higher sea level contribution than Bedmap2 and reveal decadal-scale trends in the <span class="hlt">ice</span> stream dynamics. We test the impact of several sliding laws and find that it is at least as important to accurately represent the bedrock and initial <span class="hlt">ice</span> thickness as the choice of sliding law.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12.1987S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12.1987S"><span>How does the <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> <span class="hlt">balance</span> relate to snowfall? Insights from a ground-based precipitation radar in East Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Souverijns, Niels; Gossart, Alexandra; Gorodetskaya, Irina V.; Lhermitte, Stef; Mangold, Alexander; Laffineur, Quentin; Delcloo, Andy; van Lipzig, Nicole P. M.</p> <p>2018-06-01</p> <p>Local surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) measurements are crucial for understanding changes in the total <span class="hlt">mass</span> of the Antarctic <span class="hlt">Ice</span> Sheet, including its contribution to sea level rise. Despite continuous attempts to decipher mechanisms controlling the local and regional SMB, a clear understanding of the separate components is still lacking, while snowfall measurements are almost absent. In this study, the different terms of the SMB are quantified at the Princess Elisabeth (PE) station in Dronning Maud Land, East Antarctica. Furthermore, the relationship between snowfall and accumulation at the surface is investigated. To achieve this, a unique collocated set of ground-based and in situ remote sensing instrumentation (Micro Rain Radar, ceilometer, automatic weather station, among others) was set up and operated for a time period of 37 months. Snowfall originates mainly from moist and warm air advected from lower latitudes associated with cyclone activity. However, snowfall events are not always associated with accumulation. During 38 % of the observed snowfall cases, the freshly fallen snow is ablated by the wind during the course of the event. Generally, snow storms of longer duration and larger spatial extent have a higher chance of resulting in accumulation on a local scale, while shorter events usually result in ablation (on average 17 and 12 h respectively). A large part of the accumulation at the station takes place when preceding snowfall events were occurring in synoptic upstream areas. This fresh snow is easily picked up and transported in shallow drifting snow layers over tens of kilometres, even when wind speeds are relatively low ( < 7 ms-1). Ablation events are mainly related to katabatic winds originating from the Antarctic plateau and the mountain ranges in the south. These dry winds are able to remove snow and lead to a decrease in the local SMB. This work highlights that the local SMB is strongly influenced by synoptic upstream conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C23D..02K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C23D..02K"><span>Disentangling the Roles of Atmospheric and Oceanic Forcing on the Last Deglaciation of the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Keisling, B. A.; Deconto, R. M.</p> <p>2017-12-01</p> <p>Today the Greenland <span class="hlt">Ice</span> Sheet loses <span class="hlt">mass</span> via both oceanic and atmospheric processes. However, the relative importance of these <span class="hlt">mass</span> <span class="hlt">balance</span> components is debated, especially their potential impact on ongoing and future <span class="hlt">mass</span> imbalance. Discerning the impact of oceanic versus atmospheric forcing during past periods of <span class="hlt">mass</span> loss provides potential insight into the future behavior of the <span class="hlt">ice</span> sheet. Here we present an ensemble of Greenland <span class="hlt">Ice</span> Sheet simulations of the last deglaciation, designed to assess separately the roles of the ocean and the atmosphere in driving <span class="hlt">mass</span> loss over the last twenty thousand years. We use twenty-eight different ocean forcing scenarios along with a cutting-edge reconstruction of time-evolving atmospheric conditions based on climate model output and δ15N-based temperature reconstructions to generate a range of <span class="hlt">ice</span>-sheet responses during the deglaciation. We then compare the simulated timing of <span class="hlt">ice</span>-retreat in individual catchments with estimates based on both 10Be (exposure) and 14C (minimum-limiting) dates. These experiments allow us to identify the ocean forcing scenario that best match the data on a local-to-regional (i.e., 100-1000 km) scales, providing an assessment of the relative importance of ocean and atmospheric forcing components around the periphery of Greenland. We use these simulations to quantify the importance of the three major <span class="hlt">mass</span> <span class="hlt">balance</span> terms (calving, oceanic melting, and surface melting) and assess the uncertainty of the relative influence of these factors during the most recent periods of major <span class="hlt">ice</span> loss. Our results show that <span class="hlt">mass</span> <span class="hlt">balance</span> components around different sectors of the <span class="hlt">ice</span> sheet respond differently to forcing, with oceanic components driving the majority of retreat in south and east Greenland and atmospheric forcing dominating in west and north Greenland In addition, we target three areas at high spatial resolution ( 1 km) around Greenland currently undergoing substantial change (Jakobshavn, Petermann</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011TCry....5..791K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011TCry....5..791K"><span>Deriving <span class="hlt">mass</span> <span class="hlt">balance</span> and calving variations from reanalysis data and sparse observations, Glaciar San Rafael, northern Patagonia, 1950-2005</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koppes, M.; Conway, H.; Rasmussen, L. A.; Chernos, M.</p> <p>2011-09-01</p> <p><span class="hlt">Mass</span> <span class="hlt">balance</span> variations of Glaciar San Rafael, the northernmost tidewater glacier in the Southern Hemisphere, are reconstructed over the period 1950-2005 using NCEP-NCAR reanalysis climate data together with sparse, local historical observations of air temperature, precipitation, accumulation, ablation, thinning, calving, and glacier retreat. The combined observations over the past 50 yr indicate that Glaciar San Rafael has thinned and retreated since 1959, with a total <span class="hlt">mass</span> loss of ~22 km3 of <span class="hlt">ice</span> eq. Over that period, except for a short period of cooling from 1998-2003, the climate has become progressively warmer and drier, which has resulted primarily in pervasive thinning of the glacier surface and a decrease in calving rates, with only minor acceleration in retreat of the terminus. A comparison of calving fluxes derived from the <span class="hlt">mass</span> <span class="hlt">balance</span> variations and from theoretical calving and sliding laws suggests that calving rates are inversely correlated with retreat rates, and that terminus geometry is more important than <span class="hlt">balance</span> fluxes to the terminus in driving calving dynamics. For Glaciar San Rafael, regional climate warming has not yet resulted in the significant changes in glacier length seen in other calving glaciers in the region, emphasizing the complex dynamics between climate inputs, topographic constraints and glacier response in calving glacier systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011TCD.....5.1123K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011TCD.....5.1123K"><span>Deriving <span class="hlt">mass</span> <span class="hlt">balance</span> and calving variations from reanalysis data and sparse observations, Glaciar San Rafael, northern Patagonia, 1950-2005</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koppes, M.; Conway, H.; Rasmussen, L. A.; Chernos, M.</p> <p>2011-04-01</p> <p><span class="hlt">Mass</span> <span class="hlt">balance</span> variations of Glaciar San Rafael, the most equatorial tidewater glacier in the North Patagonian Icefield, are reconstructed over the period 1950-2005 using NCEP-NCAR reanalysis climate data together with sparse, local historical observations of air temperature, precipitation, accumulation, ablation, thinning, calving, and glacier retreat. The combined observations over the past 50 yr indicate that Glaciar San Rafael has thinned and retreated since 1959, with a total <span class="hlt">mass</span> loss of ~22 km3 of <span class="hlt">ice</span> equivalent. Over that period, except for a short period of cooling from 1998-2003, the climate has become progressively warmer and drier, which has resulted primarily in pervasive thinning of the glacier surface and a decrease in calving rates, with only minor acceleration in retreat of the terminus. A comparison of calving fluxes derived from the <span class="hlt">mass</span> <span class="hlt">balance</span> variations and from theoretical calving and sliding laws suggest that calving rates are inversely correlated with retreat rates, and that terminus geometry is more important than changes in <span class="hlt">balance</span> fluxes to the terminus in driving calving dynamics. For Glaciar San Rafael, regional climate warming has not yet resulted in the significant changes in glacier length seen in other calving glaciers in the region, emphasizing the complex dynamics between climate inputs, topographic constraints and glacier response in calving glacier systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://link.springer.com/article/10.1007/s10584-013-1042-7/fulltext.html','USGSPUBS'); return false;" href="http://link.springer.com/article/10.1007/s10584-013-1042-7/fulltext.html"><span>Assessing streamflow sensitivity to variations in glacier <span class="hlt">mass</span> <span class="hlt">balance</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>O'Neel, Shad; Hood, Eran; Arendt, Anthony; Sass, Louis</p> <p>2014-01-01</p> <p>The purpose of this paper is to evaluate relationships among seasonal and annual glacier <span class="hlt">mass</span> <span class="hlt">balances</span>, glacier runoff and streamflow in two glacierized basins in different climate settings. We use long-term glacier <span class="hlt">mass</span> <span class="hlt">balance</span> and streamflow datasets from the United States Geological Survey (USGS) Alaska Benchmark Glacier Program to compare and contrast glacier-streamflow interactions in a maritime climate (Wolverine Glacier) with those in a continental climate (Gulkana Glacier). Our overall goal is to improve our understanding of how glacier <span class="hlt">mass</span> <span class="hlt">balance</span> processes impact streamflow, ultimately improving our conceptual understanding of the future evolution of glacier runoff in continental and maritime climates.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10.1259A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10.1259A"><span>Greenland <span class="hlt">Ice</span> Sheet seasonal and spatial <span class="hlt">mass</span> variability from model simulations and GRACE (2003-2012)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexander, Patrick M.; Tedesco, Marco; Schlegel, Nicole-Jeanne; Luthcke, Scott B.; Fettweis, Xavier; Larour, Eric</p> <p>2016-06-01</p> <p>Improving the ability of regional climate models (RCMs) and <span class="hlt">ice</span> sheet models (ISMs) to simulate spatiotemporal variations in the <span class="hlt">mass</span> of the Greenland <span class="hlt">Ice</span> Sheet (GrIS) is crucial for prediction of future sea level rise. While several studies have examined recent trends in GrIS <span class="hlt">mass</span> loss, studies focusing on <span class="hlt">mass</span> variations at sub-annual and sub-basin-wide scales are still lacking. At these scales, processes responsible for <span class="hlt">mass</span> change are less well understood and modeled, and could potentially play an important role in future GrIS <span class="hlt">mass</span> change. Here, we examine spatiotemporal variations in <span class="hlt">mass</span> over the GrIS derived from the Gravity Recovery and Climate Experiment (GRACE) satellites for the January 2003-December 2012 period using a "mascon" approach, with a nominal spatial resolution of 100 km, and a temporal resolution of 10 days. We compare GRACE-estimated <span class="hlt">mass</span> variations against those simulated by the Modèle Atmosphérique Régionale (MAR) RCM and the <span class="hlt">Ice</span> Sheet System Model (ISSM). In order to properly compare spatial and temporal variations in GrIS <span class="hlt">mass</span> from GRACE with model outputs, we find it necessary to spatially and temporally filter model results to reproduce leakage of <span class="hlt">mass</span> inherent in the GRACE solution. Both modeled and satellite-derived results point to a decline (of -178.9 ± 4.4 and -239.4 ± 7.7 Gt yr-1 respectively) in GrIS <span class="hlt">mass</span> over the period examined, but the models appear to underestimate the rate of <span class="hlt">mass</span> loss, especially in areas below 2000 m in elevation, where the majority of recent GrIS <span class="hlt">mass</span> loss is occurring. On an <span class="hlt">ice</span>-sheet-wide scale, the timing of the modeled seasonal cycle of cumulative <span class="hlt">mass</span> (driven by summer <span class="hlt">mass</span> loss) agrees with the GRACE-derived seasonal cycle, within limits of uncertainty from the GRACE solution. However, on sub-<span class="hlt">ice</span>-sheet-wide scales, some areas exhibit significant differences in the timing of peaks in the annual cycle of <span class="hlt">mass</span> change. At these scales, model biases, or processes not accounted for by models related</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C21D0668Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C21D0668Q"><span>Evaluation of <span class="hlt">Ice</span> sheet evolution and coastline changes from 1960s in Amery <span class="hlt">Ice</span> Shelf using multi-source remote sensing images</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Qiao, G.; Ye, W.; Scaioni, M.; Liu, S.; Feng, T.; Liu, Y.; Tong, X.; Li, R.</p> <p>2013-12-01</p> <p>Global change is one of the major challenges that all the nations are commonly facing, and the Antarctica <span class="hlt">ice</span> sheet changes have been playing a critical role in the global change research field during the past years. Long time-series of <span class="hlt">ice</span> sheet observations in Antarctica would contribute to the quantitative evaluation and precise prediction of the effects on global change induced by the <span class="hlt">ice</span> sheet, of which the remote sensing technology would make critical contributions. As the biggest <span class="hlt">ice</span> shelf and one of the dominant drainage systems in East Antarctic, the Amery <span class="hlt">Ice</span> Shelf has been making significant contributions to the <span class="hlt">mass</span> <span class="hlt">balance</span> of the Antarctic. Study of Amery <span class="hlt">Ice</span> shelf changes would advance the understanding of Antarctic <span class="hlt">ice</span> shelf evolution as well as the overall <span class="hlt">mass</span> <span class="hlt">balance</span>. At the same time, as one of the important indicators of Antarctica <span class="hlt">ice</span> sheet characteristics, coastlines that can be detected from remote sensing imagery can help reveal the nature of the changes of <span class="hlt">ice</span> sheet evolution. Most of the scientific research on Antarctica with satellite remote sensing dated from 1970s after LANDSAT satellite was brought into operation. It was the declassification of the cold war satellite reconnaissance photographs in 1995, known as Declassified Intelligence Satellite Photograph (DISP) that provided a direct overall view of the Antarctica <span class="hlt">ice</span>-sheet's configuration in 1960s, greatly extending the time span of Antarctica surface observations. This paper will present the evaluation of <span class="hlt">ice</span>-sheet evolution and coastline changes in Amery <span class="hlt">Ice</span> Shelf from 1960s, by using multi-source remote sensing images including the DISP images and the modern optical satellite images. The DISP images scanned from negatives were first interior-oriented with the associated parameters, and then bundle block adjustment technology was employed based on the tie points and control points, to derive the mosaic image of the research region. Experimental results of coastlines generated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=321804','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=321804"><span>Evapotranspiration: <span class="hlt">Mass</span> <span class="hlt">balance</span> measurements compared with flux estimation methods</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>Evapotranspiration (ET) may be measured by <span class="hlt">mass</span> <span class="hlt">balance</span> methods and estimated by flux sensing methods. The <span class="hlt">mass</span> <span class="hlt">balance</span> methods are typically restricted in terms of the area that can be represented (e.g., surface area of weighing lysimeter (LYS) or equivalent representative area of neutron probe (NP...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005JGRA..110.8103X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005JGRA..110.8103X"><span>An <span class="hlt">ice</span>-cream cone model for coronal <span class="hlt">mass</span> ejections</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xue, X. H.; Wang, C. B.; Dou, X. K.</p> <p>2005-08-01</p> <p>In this study, we use an <span class="hlt">ice</span>-cream cone model to analyze the geometrical and kinematical properties of the coronal <span class="hlt">mass</span> ejections (CMEs). Assuming that in the early phase CMEs propagate with near-constant speed and angular width, some useful properties of CMEs, namely the radial speed (v), the angular width (α), and the location at the heliosphere, can be obtained considering the geometrical shapes of a CME as an <span class="hlt">ice</span>-cream cone. This model is improved by (1) using an <span class="hlt">ice</span>-cream cone to show the near real configuration of a CME, (2) determining the radial speed via fitting the projected speeds calculated from the height-time relation in different azimuthal angles, (3) not only applying to halo CMEs but also applying to nonhalo CMEs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.9630R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.9630R"><span>Sea-<span class="hlt">Ice</span> Thickness Monitoring from Sensor Equipped Inuit Sleds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rodwell, Shane; Jones, Bryn; Wilkinson, Jeremy</p> <p>2013-04-01</p> <p>A novel instrumentation package capable of measuring sea-<span class="hlt">ice</span> thickness autonomously has been designed for long-term deployment upon the dog drawn sleds of the indigenous peoples of the Arctic. The device features a range of sensors that have been integrated with an electromagnetic induction device. These include a global positioning system, temperature sensor, tilt meter and accelerometer. Taken together, this system is able to provide accurate (+/-5cm) measurements of <span class="hlt">ice</span> thickness with spatio-temporal resolution ranging from 1m to 5m every second. Autonomous data transmission capability is provided via GSM, inspired by the fact that many of the coastal communities in Greenland possess modern cell-phone infrastructure, enabling an inexpensive means of data-retrieval. Such data is essential in quantifying the sea-<span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>; given that existing satellite based systems are unable to measure <span class="hlt">ice</span>-thickness directly. Field-campaign results from a prototype device, deployed in the North West of Greenland during three consecutive seasons, have demonstrated successful proof-of-concept when compared to data provided by <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> (IMB) stations provided at fixed positions along the route of the sled. This project highlights not only the use of novel polar technology, but how opportunistic deployment using an existing roving platform (Inuit sledges) can provide economical, yet highly valuable, data for instrumentation development.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=GL-2002-001602&hterms=BALANCE+SHEET&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DBALANCE%2BSHEET','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=GL-2002-001602&hterms=BALANCE+SHEET&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DBALANCE%2BSHEET"><span><span class="hlt">Balance</span> of the West Antarctic <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p>For several decades, measurements of the West Antarctic <span class="hlt">Ice</span> Sheet showed it to be retreating rapidly. But new data derived from satellite-borne radar sensors show the <span class="hlt">ice</span> sheet to be growing. Changing Antarctic <span class="hlt">ice</span> sheets remains an area of high scientific interest, particularly in light of recent global warming concerns. These new findings are significant because scientists estimate that sea level would rise 5-6 meters (16-20 feet) if the <span class="hlt">ice</span> sheet collapsed into the sea. Do these new measurements signal the end of the <span class="hlt">ice</span> sheet's 10,000-year retreat? Or, are these new satellite data simply much more accurate than the sparse <span class="hlt">ice</span> core and surface measurements that produced the previous estimates? Another possibility is that the <span class="hlt">ice</span> accumulation may simply indicate that the <span class="hlt">ice</span> sheet naturally expands and retreats in regular cycles. Cryologists will grapple with these questions, and many others, as they examine the new data. The image above depicts the region of West Antarctica where scientists measured <span class="hlt">ice</span> speed. The fast-moving central <span class="hlt">ice</span> streams are shown in red. Slower tributaries feeding the <span class="hlt">ice</span> streams are shown in blue. Green areas depict slow-moving, stable areas. Thick black lines depict the areas that collect snowfall to feed their respective <span class="hlt">ice</span> streams. Reference: Ian Joughin and Slawek Tulaczyk Science Jan 18 2002: 476-480. Image courtesy RADARSAT Antarctic Mapping Project</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP51A1044S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP51A1044S"><span>Exploring the <span class="hlt">Mass</span> <span class="hlt">Balance</span> and Sea Level Contribution of Global Glaciers During the Last Interglaciation and Mid-Holocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, S.; Ullman, D. J.; He, F.; Carlson, A. E.; Marzeion, B.; Maussion, F.</p> <p>2017-12-01</p> <p>Understanding the behavior of the world's glaciers during previous interglaciations is key to interpreting the sensitivity and behavior of the cryosphere under scenarios of future anthropogenic warming. Previous studies of the Last Interglaciation (LIG, 130 ka to 116 ka) indicate elevated global temperatures and higher sea levels than the Holocene, but most assessments of the impact on the cryosphere have focused on the <span class="hlt">mass</span> <span class="hlt">balance</span> and volume change of polar <span class="hlt">ice</span> sheets. In assessing sea-level sources, most studies assume complete deglacation of global glaciers, but this has yet to be tested. In addition, the significant changes in orbital forcing during the LIG and the associated impacts on climate seasonality and variability may have led to unique glacier evolution.Here, we explore the effect of LIG climate on the global glacier budget. We employ the Open Global Glacier Model (OGGM), forced by simulated LIG equilibrium climate anomalies (127 ka) from the Community Climate System Model Version 3 (CCSM3). OGGM is a glacier <span class="hlt">mass</span> <span class="hlt">balance</span> and dynamics model, specifically designed to reconstruct global glacier volume change. Our simulations have been conducted in an equilibrium state to determine the effect of the prolonged climate forcing of the LIG. Due to unknown flow characteristics of glaciers during the LIG, we explore the parametric uncertainty in the <span class="hlt">mass</span> <span class="hlt">balance</span> and flow sensitivity parameters. As a point of comparison, we also conduct a series of simulations using forcing anomalies from the CCSM3 mid-Holocene (6 ka) experiment. Results from both experiments show that glacier <span class="hlt">mass</span> <span class="hlt">balance</span> is highly sensitive to these sensitivity parameters, pointing at the need for glacier margin calibration for OGGM in paleoclimate applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4308701','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4308701"><span>Temporal constraints on future accumulation-area loss of a major Arctic <span class="hlt">ice</span> cap due to climate change (Vestfonna, Svalbard)</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Möller, Marco; Schneider, Christoph</p> <p>2015-01-01</p> <p>Arctic glaciers and <span class="hlt">ice</span> caps are major contributors to past, present and future sea-level fluctuations. Continued global warming may eventually lead to the equilibrium line altitudes of these <span class="hlt">ice</span> <span class="hlt">masses</span> rising above their highest points, triggering unstoppable downwasting. This may feed future sea-level rise considerably. We here present projections for the timing of equilibrium-line loss at the major Arctic <span class="hlt">ice</span> cap Vestfonna, Svalbard. The projections are based on spatially distributed climatic <span class="hlt">mass</span> <span class="hlt">balance</span> modelling driven by the outputs of multiple climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) forced by the Representative Concentration Pathways (RCPs) 2.6, 4.5, 6.0 and 8.5. Results indicate strongly decreasing climatic <span class="hlt">mass</span> <span class="hlt">balances</span> over the 21st century for all RCPs considered. Glacier-wide <span class="hlt">mass-balance</span> rates will drop down to −4 m a−1 w.e. (water equivalent) at a maximum. The date at which the equilibrium line rises above the summit of Vestfonna (630 m above sea level) is calculated to range between 2040 and 2150, depending on scenario. PMID:25628045</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C41E..05D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C41E..05D"><span>Multi-Decadal Averages of Basal Melt for Ross <span class="hlt">Ice</span> Shelf, Antarctica Using Airborne Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Das, I.; Bell, R. E.; Tinto, K. J.; Frearson, N.; Kingslake, J.; Padman, L.; Siddoway, C. S.; Fricker, H. A.</p> <p>2017-12-01</p> <p>Changes in <span class="hlt">ice</span> shelf <span class="hlt">mass</span> <span class="hlt">balance</span> are key to the long term stability of the Antarctic <span class="hlt">Ice</span> Sheet. Although the most extensive <span class="hlt">ice</span> shelf <span class="hlt">mass</span> loss currently is occurring in the Amundsen Sea sector of West Antarctica, many other <span class="hlt">ice</span> shelves experience changes in thickness on time scales from annual to <span class="hlt">ice</span> age cycles. Here, we focus on the Ross <span class="hlt">Ice</span> Shelf. An 18-year record (1994-2012) of satellite radar altimetry shows substantial variability in Ross <span class="hlt">Ice</span> Shelf height on interannual time scales, complicating detection of potential long-term climate-change signals in the <span class="hlt">mass</span> budget of this <span class="hlt">ice</span> shelf. Variability of radar signal penetration into the <span class="hlt">ice</span>-shelf surface snow and firn layers further complicates assessment of <span class="hlt">mass</span> changes. We investigate Ross <span class="hlt">Ice</span> Shelf <span class="hlt">mass</span> <span class="hlt">balance</span> using aerogeophysical data from the ROSETTA-<span class="hlt">Ice</span> surveys using <span class="hlt">Ice</span>Pod. We use two <span class="hlt">ice</span>-penetrating radars; a 2 GHz unit that images fine-structure in the upper 400 m of the <span class="hlt">ice</span> surface and a 360 MHz radar to identify the <span class="hlt">ice</span> shelf base. We have identified internal layers that are continuous along flow from the grounding line to the <span class="hlt">ice</span> shelf front. Based on layer continuity, we conclude that these layers must be the horizons between the continental <span class="hlt">ice</span> of the outlet glaciers and snow accumulation once the <span class="hlt">ice</span> is afloat. We use the Lagrangian change in thickness of these layers, after correcting for strain rates derived using modern day InSAR velocities, to estimate multidecadal averaged basal melt rates. This method provides a novel way to quantify basal melt, avoiding the confounding impacts of spatial and short-timescale variability in surface accumulation and firn densification processes. Our estimates show elevated basal melt rates (> -1m/yr) around Byrd and Mullock glaciers within 100 km from the <span class="hlt">ice</span> shelf front. We also compare modern InSAR velocity derived strain rates with estimates from the comprehensive ground-based RIGGS observations during 1973-1978 to estimate the potential magnitude of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C21F..08F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C21F..08F"><span>Use of a new ultra-long-range terrestrial LiDAR system to monitor the <span class="hlt">mass</span> <span class="hlt">balance</span> of very small glaciers in the Swiss Alps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fischer, M.; Huss, M.; Hoelzle, M.</p> <p>2015-12-01</p> <p>Measuring glacier <span class="hlt">mass</span> <span class="hlt">balance</span> is important as it directly reflects the climatic forcing on the glacier surface. Today, repeated comparison of digital elevation models (DEMs) is a popular and widely used approach to derive surface elevation, volume and <span class="hlt">mass</span> changes for a large number of glaciers. In high-mountain environments, airborne laser scanning (ALS) techniques currently provide the most accurate and highest resolution DEMs on the catchment scale, allowing the computation of glacier changes on an annual or even semi-annual basis. For monitoring individual glaciers though, terrestrial laser scanning (TLS) is easier and more cost-efficiently applied on the seasonal timescale compared to ALS. Since most recently, the application of the latest generation of ultra-long-range near infrared TLS systems allows the acquisition of surface elevation information over snow and <span class="hlt">ice</span> of unprecedented quality and over larger zones than with previous near infrared TLS devices. Although very small glaciers represent the majority in number in most mountain ranges on Earth, their response to climatic changes is still not fully understood and field measurements are sparse. Therefore, a programme was set up in 2012 to monitor both the seasonal and annual surface <span class="hlt">mass</span> <span class="hlt">balance</span> of six very small glaciers across the Swiss Alps using the direct glaciological method. As often nearly the entire surface is visible from one single location, TLS is a highly promising technique to generate repeated high-resolution DEMs as well as to derive seasonal geodetic <span class="hlt">mass</span> <span class="hlt">balances</span> of very small <span class="hlt">ice</span> <span class="hlt">masses</span>. In this study, we present seasonal surface elevation, volume and geodetic <span class="hlt">mass</span> changes for five very small glaciers in Switzerland (Glacier de Prapio, Glacier du Sex Rouge, St. Annafirn, Schwarzbachfirn and Pizolgletscher) derived from the comparison of seasonally repeated high-resolution DEMs acquired since autumn 2013 with the new ultra-long-range TLS device Riegl VZ-6000. We show the different</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930081400','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930081400"><span>Considerations affecting the additional weight required in <span class="hlt">mass</span> <span class="hlt">balance</span> of ailerons</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Diehl, W S</p> <p>1937-01-01</p> <p>This paper is essentially a consideration of <span class="hlt">mass</span> <span class="hlt">balance</span> of ailerons from a preliminary design standpoint, in which the extra weight of the <span class="hlt">mass</span> counterbalance is the most important phase of the problem. Equations are developed for the required <span class="hlt">balance</span> weight for a simple aileron and this weight is correlated with the <span class="hlt">mass-balance</span> coefficient. It is concluded the location of the c.g. of the basic aileron is of paramount importance and that complete <span class="hlt">mass</span> <span class="hlt">balance</span> imposes no great weight penalty if the aileron is designed to have its c.g. inherently near to the hinge axis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMOS22A..07H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMOS22A..07H"><span>Improved regional sea-level estimates from <span class="hlt">Ice</span> Sheets, Glaciers and land water storage using GRACE time series and other data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>He, Z.; Velicogna, I.; Hsu, C. W.; Rignot, E. J.; Mouginot, J.; Scheuchl, B.; Fettweis, X.; van den Broeke, M. R.</p> <p>2017-12-01</p> <p>Changes in <span class="hlt">ice</span> sheets, glaciers and <span class="hlt">ice</span> caps (GIC) and land water <span class="hlt">mass</span> cause regional sea level variations that differ significantly from a uniform re-distribution of <span class="hlt">mass</span> over the ocean, with a decrease in sea level compared to the global mean sea level contribution (GMSL) near the sources of <span class="hlt">mass</span> added to the ocean and an increase up to 30% larger than the GMSL in the far field. The corresponding sea level fingerprints (SLF) are difficult to separate from ocean dynamics on short time and spatial scales but as <span class="hlt">ice</span> melt continues, the SLF signal will become increasingly dominant in the pattern of regional sea level rise. It has been anticipated that it will be another few decades before the land <span class="hlt">ice</span> SLF could be identified in the pattern of regional sea level rise. Here, we combine 40 years of observations of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> for Antarctica (1975-present) and Greenland (1978-present), along with surface <span class="hlt">mass</span> <span class="hlt">balance</span> reconstructions of glacier and <span class="hlt">ice</span> caps <span class="hlt">mass</span> <span class="hlt">balance</span> (GIC) from 1970s to present to determine the contribution to the SLF from melting land <span class="hlt">ice</span> (MAR and RACMO). We compare the results with observations from GRACE for the time period 2002 to present for evaluation of our approach. Land hydrology is constrained by GRACE data for the period 2002-present and by the GLDAS-NOAH land hydrology model for the longer time period. Over the long time period, we find that the contribution from land <span class="hlt">ice</span> dominates. We quantify the contribution to the total SLF from Greenland and Antarctica in various parts of the world over the past 40 years. More important, we compare the cumulative signal from SLF with tide gauge records around the world, corrected for earth dynamics, to determine whether the land <span class="hlt">ice</span> SLF can be detected in that record. Early results will be reported at the meeting. This work was performed at UC Irvine and at Caltech's Jet Propulsion Laboratory under a contract with NASA's Cryospheric Science Program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016FrEaS...4..102V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016FrEaS...4..102V"><span>The changing impact of snow conditions and refreezing on the <span class="hlt">mass</span> <span class="hlt">balance</span> of an idealized Svalbard glacier</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Van Pelt, Ward; Pohjola, Veijo; Reijmer, Carleen</p> <p>2016-11-01</p> <p>Glacier surface melt and runoff depend strongly on seasonal and perennial snow (firn) conditions. Not only does the presence of snow and firn directly affect melt rates by reflecting solar radiation, it may also act as a buffer against <span class="hlt">mass</span> loss by storing melt water in refrozen or liquid form. In Svalbard, ongoing and projected amplified climate change with respect to the global mean change has severe implications for the state of snow and firn and its impact on glacier <span class="hlt">mass</span> loss. Model experiments with a coupled surface energy <span class="hlt">balance</span> - firn model were done to investigate the surface <span class="hlt">mass</span> <span class="hlt">balance</span> and the changing role of snow and firn conditions for an idealized Svalbard glacier. A climate forcing for the past, present and future (1984-2104) is constructed, based on observational data from Svalbard Airport and a seasonally dependent projection scenario. Results illustrate ongoing and future firn degradation in response to an elevational retreat of the equilibrium line altitude (ELA) of 31 m decade-1. The temperate firn zone is found to retreat and expand, while cold <span class="hlt">ice</span> in the ablation zone warms considerably. In response to pronounced winter warming and an associated increase in winter rainfall, the current prevalence of refreezing during the melt season gradually shifts to the winter season in a future climate. Sensitivity tests reveal that in a present and future climate the density and thermodynamic structure of Svalbard glaciers are heavily influenced by refreezing. Refreezing acts as a net buffer against <span class="hlt">mass</span> loss. However, the net <span class="hlt">mass</span> <span class="hlt">balance</span> change after refreezing is substantially smaller than the amount of refreezing itself, which can be ascribed to melt-enhancing effects after refreezing, which partly offset the primary <span class="hlt">mass</span>-retaining effect of refreezing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C41A0692S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C41A0692S"><span>A Newly Updated Database of Elevation-changes of the Greenand <span class="hlt">Ice</span> Sheet to Study Surface Processes and <span class="hlt">Ice</span> Dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schenk, A. F.; Csatho, B. M.; van den Broeke, M.; Kuipers Munneke, P.</p> <p>2015-12-01</p> <p>This paper reports about important upgrades of the Greenland <span class="hlt">Ice</span> Sheet (GrIS) surface elevation and elevation-change database obtained with our Surface Elevation And Change detection (SERAC) software suite. We have developed SERAC to derive information from laser altimetry data, particularly time series of elevation changes and their partitioning into changes caused by <span class="hlt">ice</span> dynamics. This allows direct investigation of <span class="hlt">ice</span> dynamic processes that is much needed for improving the predictive power of <span class="hlt">ice</span> sheet models. SERAC is different from most other change detection methods. It is based on detecting changes of surface patches, about 1 km by 1 km in size, rather than deriving elevation changes from individual laser points. The current database consists of ~100,000 time series with satellite laser altimetry data from ICESat, airborne laser observations obtained by NASA's Airborne Topographic Mapper (ATM) and the Land, Vegetation and <span class="hlt">Ice</span> Sensor (LVIS). The upgrade is significant, because not only new observations from 2013 and 2014 have been added but also a number of improvements lead to a more comprehensive and consistent record of elevation-changes. First, we used the model that gives in addition to <span class="hlt">ice</span> sheet also information about <span class="hlt">ice</span> caps and glaciers (Rastner et al., 2012) for deciding if a laser point is on the <span class="hlt">ice</span> sheet or <span class="hlt">ice</span> cap. Then we added small gaps that exist in the ICESat GLA12 data set because the <span class="hlt">ice</span> sheet mask is not wide enough. The new database is now more complete and will facilitate more accurate comparisons of <span class="hlt">mass</span> <span class="hlt">balance</span> studies obtained from the Gravity Recovery and Climate Experiment system (GRACE). For determining the part of a time series caused by <span class="hlt">ice</span> dynamics we used the new firn compaction model and Surface <span class="hlt">Mass</span> <span class="hlt">Balance</span> (SMB) estimates from RACMO2.3. The new database spans the time period from 1993 to 2014. Adding new observations amounts to a spatial densification of the old record and at the same time extends the time domain by two</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890018778','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890018778"><span>Analysis of sea <span class="hlt">ice</span> dynamics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, J.</p> <p>1988-01-01</p> <p>The ongoing work has established the basis for using multiyear sea <span class="hlt">ice</span> concentrations from SMMR passive microwave for studies of largescale advection and convergence/divergence of the Arctic sea <span class="hlt">ice</span> pack. Comparisons were made with numerical model simulations and buoy data showing qualitative agreement on daily to interannual time scales. Analysis of the 7-year SMMR data set shows significant interannual variations in the total area of multiyear <span class="hlt">ice</span>. The scientific objective is to investigate the dynamics, <span class="hlt">mass</span> <span class="hlt">balance</span>, and interannual variability of the Arctic sea <span class="hlt">ice</span> pack. The research emphasizes the direct application of sea <span class="hlt">ice</span> parameters derived from passive microwave data (SMMR and SSMI) and collaborative studies using a sea <span class="hlt">ice</span> dynamics model. The possible causes of observed interannual variations in the multiyear <span class="hlt">ice</span> area are being examined. The relative effects of variations in the large scale advection and convergence/divergence within the <span class="hlt">ice</span> pack on a regional and seasonal basis are investigated. The effects of anomolous atmospheric forcings are being examined, including the long-lived effects of synoptic events and monthly variations in the mean geostrophic winds. Estimates to be made will include the amount of new <span class="hlt">ice</span> production within the <span class="hlt">ice</span> pack during winter and the amount of <span class="hlt">ice</span> exported from the pack.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C21E1165W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C21E1165W"><span>A Detailed Geophysical Investigation of the Grounding of Henry <span class="hlt">Ice</span> Rise, with Implications for Holocene <span class="hlt">Ice</span>-Sheet Extent.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wearing, M.; Kingslake, J.</p> <p>2017-12-01</p> <p>It is generally assumed that since the Last Glacial Maximum the West Antarctic <span class="hlt">Ice</span> Sheet (WAIS) has experienced monotonic retreat of the grounding line (GL). However, recent studies have cast doubt on this assumption, suggesting that the retreat of the WAIS grounding line may have been followed by a significant advance during the Holocene in the Weddell and Ross Sea sectors. Constraining this evolution is important as reconstructions of past <span class="hlt">ice</span>-sheet extent are used to spin-up predictive <span class="hlt">ice</span>-sheet models and correct <span class="hlt">mass-balance</span> observations for glacial isostatic adjustment. Here we examine in detail the formation of the Henry <span class="hlt">Ice</span> Rise (HIR), which <span class="hlt">ice</span>-sheet model simulations suggest played a key role in Holocene <span class="hlt">ice-mass</span> changes in the Weddell Sea sector. Observations from a high-resolution ground-based, <span class="hlt">ice</span>-penetrating radar survey are best explained if the <span class="hlt">ice</span> rise formed when the Ronne <span class="hlt">Ice</span> Shelf grounded on a submarine high, underwent a period of <span class="hlt">ice</span>-rumple flow, before the GL migrated outwards to form the present-day <span class="hlt">ice</span> rise. We constrain the relative chronology of this evolution by comparing the alignment and intersection of isochronal internal layers, relic crevasses, surface features and investigating the dynamic processes leading to their complex structure. We also draw analogies between HIR and the neighbouring Doake <span class="hlt">Ice</span> Rumples. The date of formation is estimated using vertical velocities derived with a phase-sensitive radio-echo sounder (pRES). <span class="hlt">Ice</span>-sheet models suggest that the formation of the HIR and other <span class="hlt">ice</span> rises may have halted and reversed large-scale GL retreat. Hence the small-scale dynamics of these crucial regions could have wide-reaching consequences for future <span class="hlt">ice</span>-sheet <span class="hlt">mass</span> changes and constraining their formation and evolution further would be beneficial. One stringent test of our geophysics-based conclusions would be to drill to the bed of HIR to sample the <span class="hlt">ice</span> for isotopic analysis and the bed for radiocarbon analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29540750','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29540750"><span>Recent high-resolution Antarctic <span class="hlt">ice</span> velocity maps reveal increased <span class="hlt">mass</span> loss in Wilkes Land, East Antarctica.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shen, Qiang; Wang, Hansheng; Shum, C K; Jiang, Liming; Hsu, Hou Tse; Dong, Jinglong</p> <p>2018-03-14</p> <p>We constructed Antarctic <span class="hlt">ice</span> velocity maps from Landsat 8 images for the years 2014 and 2015 at a high spatial resolution (100 m). These maps were assembled from 10,690 scenes of displacement vectors inferred from more than 10,000 optical images acquired from December 2013 through March 2016. We estimated the <span class="hlt">mass</span> discharge of the Antarctic <span class="hlt">ice</span> sheet in 2008, 2014, and 2015 using the Landsat <span class="hlt">ice</span> velocity maps, interferometric synthetic aperture radar (InSAR)-derived <span class="hlt">ice</span> velocity maps (~2008) available from prior studies, and <span class="hlt">ice</span> thickness data. An increased <span class="hlt">mass</span> discharge (53 ± 14 Gt yr -1 ) was found in the East Indian Ocean sector since 2008 due to unexpected widespread glacial acceleration in Wilkes Land, East Antarctica, while the other five oceanic sectors did not exhibit significant changes. However, present-day increased <span class="hlt">mass</span> loss was found by previous studies predominantly in west Antarctica and the Antarctic Peninsula. The newly discovered increased <span class="hlt">mass</span> loss in Wilkes Land suggests that the ocean heat flux may already be influencing <span class="hlt">ice</span> dynamics in the marine-based sector of the East Antarctic <span class="hlt">ice</span> sheet (EAIS). The marine-based sector could be adversely impacted by ongoing warming in the Southern Ocean, and this process may be conducive to destabilization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70021642','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70021642"><span><span class="hlt">Mass-balance</span> measurements in Alaska and suggestions for simplified observation programs</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Trabant, D.C.; March, R.S.</p> <p>1999-01-01</p> <p>US Geological Survey glacier fieldwork in Alaska includes repetitious measurements, corrections for leaning or bending stakes, an ability to reliably measure seasonal snow as deep as 10 m, absolute identification of summer surfaces in the accumulation area, and annual evaluation of internal accumulation, internal ablation, and glacier-thickness changes. Prescribed field measurement and note-taking techniques help eliminate field errors and expedite the interpretative process. In the office, field notes are transferred to computerized spread-sheets for analysis, release on the World Wide Web, and archival storage. The spreadsheets have error traps to help eliminate note-taking and transcription errors. Rigorous error analysis ends when <span class="hlt">mass-balance</span> measurements are extrapolated and integrated with area to determine glacier and basin <span class="hlt">mass</span> <span class="hlt">balances</span>. Unassessable errors in the glacier and basin <span class="hlt">mass-balance</span> data reduce the value of the data set for correlations with climate change indices. The minimum glacier <span class="hlt">mass-balance</span> program has at least three measurement sites on a glacier and the measurements must include the seasonal components of <span class="hlt">mass</span> <span class="hlt">balance</span> as well as the annual <span class="hlt">balance</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810633W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810633W"><span><span class="hlt">Ice</span> <span class="hlt">Mass</span> Changes in the Russian High Arctic from Repeat High Resolution Topography.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Willis, Michael; Zheng, Whyjay; Pritchard, Matthew; Melkonian, Andrew; Morin, Paul; Porter, Claire; Howat, Ian; Noh, Myoung-Jong; Jeong, Seongsu</p> <p>2016-04-01</p> <p>We use a combination of ASTER and cartographically derived Digital Elevation Models (DEMs) supplemented with WorldView DEMs, the ArcticDEM and ICESat lidar returns to produce a time-series of <span class="hlt">ice</span> changes occurring in the Russian High Arctic between the mid-20th century and the present. Glaciers on the western, Barents Sea coast of Novaya Zemlya are in a state of general retreat and thinning, while those on the eastern, Kara Sea coast are retreating at a slower rate. Franz Josef Land has a complicated pattern of thinning and thickening, although almost all the thinning is associated with rapid outlet glaciers feeding <span class="hlt">ice</span> shelves. Severnaya Zemlya is also thinning in a complicated manner. A very rapid surging glacier is transferring <span class="hlt">mass</span> into the ocean from the western periphery of the Vavilov <span class="hlt">Ice</span> Cap on October Revolution Island, while glaciers feeding the former Matusevich <span class="hlt">Ice</span> Shelf continue to thin at rates that are faster than those observed during the operational period of ICESat, between 2003 and 2009. Passive microwave studies indicate the total number of melt days is increasing in the Russian Arctic, although much of the melt may refreeze within the firn. It is likely that <span class="hlt">ice</span> dynamic changes will drive <span class="hlt">mass</span> loss for the immediate future. The sub-marine basins beneath several of the <span class="hlt">ice</span> caps in the region suggest the possibility that <span class="hlt">mass</span> loss rates may accelerate in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/imap/2600/D/i2600d-pamphlet.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/imap/2600/D/i2600d-pamphlet.pdf"><span>Coastal-change and glaciological map of the Ronne <span class="hlt">Ice</span> Shelf area, Antarctica, 1974-2002</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ferrigno, Jane G.; Foley, K.M.; Swithinbank, C.; Williams, R.S.; Dalide, L.M.</p> <p>2005-01-01</p> <p>Changes in the area and volume of polar <span class="hlt">ice</span> sheets are intricately linked to changes in global climate, and the resulting changes in sea level may severely impact the densely populated coastal regions on Earth. Melting of the West Antarctic part alone of the Antarctic <span class="hlt">ice</span> sheet could cause a sea-level rise of approximately 6 meters (m). The potential sea-level rise after melting of the entire Antarctic <span class="hlt">ice</span> sheet is estimated to be 65 m (Lythe and others, 2001) to 73 m (Williams and Hall, 1993). In spite of its importance, the <span class="hlt">mass</span> <span class="hlt">balance</span> (the net volumetric gain or loss) of the Antarctic <span class="hlt">ice</span> sheet is poorly known; it is not known for certain whether the <span class="hlt">ice</span> sheet is growing or shrinking. In a review paper, Rignot and Thomas (2002) concluded that the West Antarctic part of the Antarctic <span class="hlt">ice</span> sheet is probably becoming thinner overall; although it is thickening in the west, it is thinning in the north. Joughin and Tulaczyk (2002), on the basis of analysis of <span class="hlt">ice</span>-flow velocities derived from synthetic aperture radar, concluded that most of the Ross <span class="hlt">ice</span> streams (<span class="hlt">ice</span> streams on the east side of the Ross <span class="hlt">Ice</span> Shelf) have a positive <span class="hlt">mass</span> <span class="hlt">balance</span>, whereas Rignot and others (in press) infer even larger negative <span class="hlt">mass</span> <span class="hlt">balance</span> for glaciers flowing northward into the Amundsen Sea, a trend suggested by Swithinbank and others (2003a,b, 2004). The <span class="hlt">mass</span> <span class="hlt">balance</span> of the East Antarctic part of the Antarctic <span class="hlt">ice</span> sheet is unknown, but thought to be in near equilibrium. Measurement of changes in area and <span class="hlt">mass</span> <span class="hlt">balance</span> of the Antarctic <span class="hlt">ice</span> sheet was given a very high priority in recommendations by the Polar Research Board of the National Research Council (1986), in subsequent recommendations by the Scientific Committee on Antarctic Research (SCAR) (1989, 1993), and by the National Science Foundation's (1990) Division of Polar Pro-grams. On the basis of these recommendations, the U.S. Geo-logical Survey (USGS) decided that the archive of early 1970s Landsat 1, 2, and 3 Multispectral Scanner</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030002360','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030002360"><span>Determining Greenland <span class="hlt">Ice</span> Sheet Accumulation Rates from Radar Remote Sensing</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jezek, Kenneth C.</p> <p>2002-01-01</p> <p>An important component of NASA's Program for Arctic Regional Climate Assessment (PARCA) is a <span class="hlt">mass</span> <span class="hlt">balance</span> investigation of the Greenland <span class="hlt">Ice</span> Sheet. The <span class="hlt">mass</span> <span class="hlt">balance</span> is calculated by taking the difference between the areally Integrated snow accumulation and the net <span class="hlt">ice</span> discharge of the <span class="hlt">ice</span> sheet. Uncertainties in this calculation Include the snow accumulation rate, which has traditionally been determined by interpolating data from <span class="hlt">ice</span> core samples taken from isolated spots across the <span class="hlt">ice</span> sheet. The sparse data associated with <span class="hlt">ice</span> cores juxtaposed against the high spatial and temporal resolution provided by remote sensing , has motivated scientists to investigate relationships between accumulation rate and microwave observations as an option for obtaining spatially contiguous estimates. The objective of this PARCA continuation proposal was to complete an estimate of surface accumulation rate on the Greenland <span class="hlt">Ice</span> Sheet derived from C-band radar backscatter data compiled in the ERS-1 SAR mosaic of data acquired during, September-November, 1992. An empirical equation, based on elevation and latitude, is used to determine the mean annual temperature. We examine the influence of accumulation rate, and mean annual temperature on C-band radar backscatter using a forward model, which incorporates snow metamorphosis and radar backscatter components. Our model is run over a range of accumulation and temperature conditions. Based on the model results, we generate a look-up table, which uniquely maps the measured radar backscatter, and mean annual temperature to accumulation rate. Our results compare favorably with in situ accumulation rate measurements falling within our study area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22538614','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22538614"><span>Antarctic <span class="hlt">ice</span>-sheet loss driven by basal melting of <span class="hlt">ice</span> shelves.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pritchard, H D; Ligtenberg, S R M; Fricker, H A; Vaughan, D G; van den Broeke, M R; Padman, L</p> <p>2012-04-25</p> <p>Accurate prediction of global sea-level rise requires that we understand the cause of recent, widespread and intensifying glacier acceleration along Antarctic <span class="hlt">ice</span>-sheet coastal margins. Atmospheric and oceanic forcing have the potential to reduce the thickness and extent of floating <span class="hlt">ice</span> shelves, potentially limiting their ability to buttress the flow of grounded tributary glaciers. Indeed, recent <span class="hlt">ice</span>-shelf collapse led to retreat and acceleration of several glaciers on the Antarctic Peninsula. But the extent and magnitude of <span class="hlt">ice</span>-shelf thickness change, the underlying causes of such change, and its link to glacier flow rate are so poorly understood that its future impact on the <span class="hlt">ice</span> sheets cannot yet be predicted. Here we use satellite laser altimetry and modelling of the surface firn layer to reveal the circum-Antarctic pattern of <span class="hlt">ice</span>-shelf thinning through increased basal melt. We deduce that this increased melt is the primary control of Antarctic <span class="hlt">ice</span>-sheet loss, through a reduction in buttressing of the adjacent <span class="hlt">ice</span> sheet leading to accelerated glacier flow. The highest thinning rates occur where warm water at depth can access thick <span class="hlt">ice</span> shelves via submarine troughs crossing the continental shelf. Wind forcing could explain the dominant patterns of both basal melting and the surface melting and collapse of Antarctic <span class="hlt">ice</span> shelves, through ocean upwelling in the Amundsen and Bellingshausen seas, and atmospheric warming on the Antarctic Peninsula. This implies that climate forcing through changing winds influences Antarctic <span class="hlt">ice</span>-sheet <span class="hlt">mass</span> <span class="hlt">balance</span>, and hence global sea level, on annual to decadal timescales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10..811D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10..811D"><span>Constraining variable density of <span class="hlt">ice</span> shelves using wide-angle radar measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drews, Reinhard; Brown, Joel; Matsuoka, Kenichi; Witrant, Emmanuel; Philippe, Morgane; Hubbard, Bryn; Pattyn, Frank</p> <p>2016-04-01</p> <p>The thickness of <span class="hlt">ice</span> shelves, a basic parameter for <span class="hlt">mass</span> <span class="hlt">balance</span> estimates, is typically inferred using hydrostatic equilibrium, for which knowledge of the depth-averaged density is essential. The densification from snow to <span class="hlt">ice</span> depends on a number of local factors (e.g., temperature and surface <span class="hlt">mass</span> <span class="hlt">balance</span>) causing spatial and temporal variations in density-depth profiles. However, direct measurements of firn density are sparse, requiring substantial logistical effort. Here, we infer density from radio-wave propagation speed using ground-based wide-angle radar data sets (10 MHz) collected at five sites on Roi Baudouin <span class="hlt">Ice</span> Shelf (RBIS), Dronning Maud Land, Antarctica. We reconstruct depth to internal reflectors, local <span class="hlt">ice</span> thickness, and firn-air content using a novel algorithm that includes traveltime inversion and ray tracing with a prescribed shape of the depth-density relationship. For the particular case of an <span class="hlt">ice</span>-shelf channel, where <span class="hlt">ice</span> thickness and surface slope change substantially over a few kilometers, the radar data suggest that firn inside the channel is about 5 % denser than outside the channel. Although this density difference is at the detection limit of the radar, it is consistent with a similar density anomaly reconstructed from optical televiewing, which reveals that the firn inside the channel is 4.7 % denser than that outside the channel. Hydrostatic <span class="hlt">ice</span> thickness calculations used for determining basal melt rates should account for the denser firn in <span class="hlt">ice</span>-shelf channels. The radar method presented here is robust and can easily be adapted to different radar frequencies and data-acquisition geometries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://dx.doi.org/10.1126/science.1209299','USGSPUBS'); return false;" href="http://dx.doi.org/10.1126/science.1209299"><span>Interhemispheric <span class="hlt">ice</span>-sheet synchronicity during the last glacial maximum</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Weber, Michael E.; Clark, Peter U.; Ricken, Werner; Mitrovica, Jerry X.; Hostetler, Steven W.; Kuhn, Gerhard</p> <p>2011-01-01</p> <p>The timing of the last maximum extent of the Antarctic <span class="hlt">ice</span> sheets relative to those in the Northern Hemisphere remains poorly understood. We develop a chronology for the Weddell Sea sector of the East Antarctic <span class="hlt">Ice</span> Sheet that, combined with ages from other Antarctic <span class="hlt">ice</span>-sheet sectors, indicates that the advance to and retreat from their maximum extent was within dating uncertainties synchronous with most sectors of Northern Hemisphere <span class="hlt">ice</span> sheets. Surface climate forcing of Antarctic <span class="hlt">mass</span> <span class="hlt">balance</span> would probably cause an opposite response, whereby a warming climate would increase accumulation but not surface melting. Our new data support teleconnections involving sea-level forcing from Northern Hemisphere <span class="hlt">ice</span> sheets and changes in North Atlantic deep-water formation and attendant heat flux to Antarctic grounding lines to synchronize the hemispheric <span class="hlt">ice</span> sheets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22144623','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22144623"><span>Interhemispheric <span class="hlt">ice</span>-sheet synchronicity during the Last Glacial Maximum.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Weber, Michael E; Clark, Peter U; Ricken, Werner; Mitrovica, Jerry X; Hostetler, Steven W; Kuhn, Gerhard</p> <p>2011-12-02</p> <p>The timing of the last maximum extent of the Antarctic <span class="hlt">ice</span> sheets relative to those in the Northern Hemisphere remains poorly understood. We develop a chronology for the Weddell Sea sector of the East Antarctic <span class="hlt">Ice</span> Sheet that, combined with ages from other Antarctic <span class="hlt">ice</span>-sheet sectors, indicates that the advance to and retreat from their maximum extent was within dating uncertainties synchronous with most sectors of Northern Hemisphere <span class="hlt">ice</span> sheets. Surface climate forcing of Antarctic <span class="hlt">mass</span> <span class="hlt">balance</span> would probably cause an opposite response, whereby a warming climate would increase accumulation but not surface melting. Our new data support teleconnections involving sea-level forcing from Northern Hemisphere <span class="hlt">ice</span> sheets and changes in North Atlantic deep-water formation and attendant heat flux to Antarctic grounding lines to synchronize the hemispheric <span class="hlt">ice</span> sheets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.5475A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.5475A"><span><span class="hlt">Ice</span> thickness measurements and volume estimates for glaciers in Norway</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andreassen, Liss M.; Huss, Matthias; Melvold, Kjetil; Elvehøy, Hallgeir; Winsvold, Solveig H.</p> <p>2014-05-01</p> <p>Whereas glacier areas in many mountain regions around the world now are well surveyed using optical satellite sensors and available in digital inventories, measurements of <span class="hlt">ice</span> thickness are sparse in comparison and a global dataset does not exist. Since the 1980s <span class="hlt">ice</span> thickness measurements have been carried out by ground penetrating radar on many glaciers in Norway, often as part of contract work for hydropower companies with the aim to calculate hydrological divides of <span class="hlt">ice</span> caps. Measurements have been conducted on numerous glaciers, covering the largest <span class="hlt">ice</span> caps as well as a few smaller mountain glaciers. However, so far no <span class="hlt">ice</span> volume estimate for Norway has been derived from these measurements. Here, we give an overview of <span class="hlt">ice</span> thickness measurements in Norway, and use a distributed model to interpolate and extrapolate the data to provide an <span class="hlt">ice</span> volume estimate of all glaciers in Norway. We also compare the results to various volume-area/thickness-scaling approaches using values from the literature as well as scaling constants we obtained from <span class="hlt">ice</span> thickness measurements in Norway. Glacier outlines from a Landsat-derived inventory from 1999-2006 together with a national digital elevation model were used as input data for the <span class="hlt">ice</span> volume calculations. The inventory covers all glaciers in mainland Norway and consists of 2534 glaciers (3143 glacier units) covering an area of 2692 km2 ± 81 km2. To calculate the <span class="hlt">ice</span> thickness distribution of glaciers in Norway we used a distributed model which estimates surface <span class="hlt">mass</span> <span class="hlt">balance</span> distribution, calculates the volumetric <span class="hlt">balance</span> flux and converts it into thickness using the flow law for <span class="hlt">ice</span>. We calibrated this model with <span class="hlt">ice</span> thickness data for Norway, mainly by adjusting the <span class="hlt">mass</span> <span class="hlt">balance</span> gradient. Model results generally agree well with the measured values, however, larger deviations were found for some glaciers. The total <span class="hlt">ice</span> volume of Norway was estimated to be 275 km3 ± 30 km3. From the <span class="hlt">ice</span> thickness data set we selected</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.8422K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.8422K"><span>Surface terrain characteristics and monsoon season <span class="hlt">mass</span> <span class="hlt">balance</span> of debris-covered glaciers in the Khumbu Himal, Nepal, obtained from high resolution Pléiades imagery.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klug, Christoph; Nicholson, Lindsey; Rieg, Lorenzo; Sailer, Rudolf; Wirbel, Anna</p> <p>2016-04-01</p> <p>Debris-covered glaciers in the eastern Himalaya have pronounced surface relief consisting of hummocks and hollows, <span class="hlt">ice</span> cliffs, lakes and former lake beds. This relief and spatially variable surface properties are expected to influence the spatially distributed surface energy <span class="hlt">balance</span> and related <span class="hlt">ice</span> <span class="hlt">mass</span> loss and atmospheric interactions, but only a few studies have so far explicitly examined the nature of the surface terrain and its textures . In this work we present a new high-resolution digital terrain model (DTM) of a portion of the Khumbu Himal in the eastern Nepalese Himalaya, derived from Pléiades satellite imagery sampled in spring 2015. We use this DTM to study the terrain characteristics of five sample glaciers and analyse the inter- and intra- glacier variability of terrain characteristics in the context of glacier flow velocities and surface changes presented in previous studies in the area. In parallel to this analysis we also present the seasonal geodetic <span class="hlt">mass</span> <span class="hlt">balance</span> between spring and fall 2015, and relate it to the terrain properties, surface velocity and limited knowledge of the local lapse rates in meteorological conditions during this monsoon season.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1911309W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1911309W"><span>Submarine melt rates under Greenland's <span class="hlt">ice</span> tongues</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilson, Nat; Straneo, Fiametta; Heimbach, Patrick; Cenedese, Claudia</p> <p>2017-04-01</p> <p>The few remaining <span class="hlt">ice</span> tongues (<span class="hlt">ice</span>-shelf like extensions) of Greenland's glaciers are undergoing rapid changes with potential implications for the stability of the <span class="hlt">ice</span> sheet. Submarine melting is recognized as a major contributor to <span class="hlt">mass</span> loss, yet the magnitude and spatial distribution of melt are poorly known or understood. Here, we use high resolution satellite imagery to infer the magnitude and spatial variability of melt rates under Greenland's largest remaining <span class="hlt">ice</span> tongues: Ryder Glacier, Petermann Glacier and Nioghalvfjerdsbræ (79 North Glacier). We find that submarine plus aerial melt approximately <span class="hlt">balance</span> the <span class="hlt">ice</span> flux from the grounded <span class="hlt">ice</span> sheet for the first two while at Nioghalvfjerdsbræ the total melt flux exceeds the inflow of <span class="hlt">ice</span> indicating thinning of the <span class="hlt">ice</span> tongue. We also show that melt rates under the <span class="hlt">ice</span> tongues vary considerably, exceeding 60 m yr-1 near the grounding zone and decaying rapidly downstream. Channels, likely originating from upstream subglacial channels, give rise to large melt variations across the <span class="hlt">ice</span> tongues. Using derived melt rates, we test simplified melt parameterizations appropriate for <span class="hlt">ice</span> sheet models and find the best agreement with those that incorporate <span class="hlt">ice</span> tongue geometry in the form of depth and slope.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015TCry....9.1761B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015TCry....9.1761B"><span>Quantifying the resolution level where the GRACE satellites can separate Greenland's glacial <span class="hlt">mass</span> <span class="hlt">balance</span> from surface <span class="hlt">mass</span> <span class="hlt">balance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bonin, J. A.; Chambers, D. P.</p> <p>2015-09-01</p> <p><span class="hlt">Mass</span> change over Greenland can be caused by either changes in the glacial dynamic <span class="hlt">mass</span> <span class="hlt">balance</span> (DMB) or the surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB). The GRACE satellite gravity mission cannot directly separate the two physical causes because it measures the sum of the entire <span class="hlt">mass</span> column with limited spatial resolution. We demonstrate one theoretical way to indirectly separate cumulative SMB from DMB with GRACE, using a least squares inversion technique with knowledge of the location of the glaciers. However, we find that the limited 60 × 60 spherical harmonic representation of current GRACE data does not provide sufficient resolution to adequately accomplish the task. We determine that at a maximum degree/order of 90 × 90 or above, a noise-free gravity measurement could theoretically separate the SMB from DMB signals. However, current GRACE satellite errors are too large at present to separate the signals. A noise reduction of a factor of 10 at a resolution of 90 × 90 would provide the accuracy needed for the interannual cumulative SMB and DMB to be accurately separated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015TCD.....9.1315B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015TCD.....9.1315B"><span>Quantifying the resolution level where the GRACE satellites can separate Greenland's glacial <span class="hlt">mass</span> <span class="hlt">balance</span> from surface <span class="hlt">mass</span> <span class="hlt">balance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bonin, J. A.; Chambers, D. P.</p> <p>2015-02-01</p> <p><span class="hlt">Mass</span> change over Greenland can be caused by either changes in the glacial <span class="hlt">mass</span> <span class="hlt">balance</span> (GMB) or the precipitation-based surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB). The GRACE satellite gravity mission cannot directly separate the two physical causes because it measures the sum of the entire <span class="hlt">mass</span> column with limited spatial resolution. We demonstrate one theoretical way to indirectly separate SMB from GMB with GRACE, using a least squares inversion technique with knowledge of the location of the glacier. However, we find that the limited 60 × 60 spherical harmonic representation of current GRACE data does not provide sufficient resolution to adequately accomplish the task. We determine that at a maximum degree/order of 90 × 90 or above, a noise-free gravity measurement could theoretically separate the SMB from GMB signals. However, current GRACE satellite errors are too large at present to separate the signals. A noise reduction of a factor of 9 at a resolution of 90 × 90 would provide the accuracy needed for the interannual SMB and GMB to be accurately separated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28756626','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28756626"><span>Myths and methodologies: Making sense of exercise <span class="hlt">mass</span> and water <span class="hlt">balance</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cheuvront, Samuel N; Montain, Scott J</p> <p>2017-09-01</p> <p>What is the topic of this review? There is a need to revisit the basic principles of exercise <span class="hlt">mass</span> and water <span class="hlt">balance</span>, the use of common equations and the practice of interpreting outcomes. What advances does it highlight? We propose use of the following equation as a way of simplifying exercise <span class="hlt">mass</span> and water <span class="hlt">balance</span> calculations in conditions where food is not consumed and waste is not excreted: ∆body <span class="hlt">mass</span> - 0.20 g/kcal -1 = ∆body water. The relative efficacy of exercise drinking behaviours can be judged using the following equation: percentage dehydration = [(∆body <span class="hlt">mass</span> - 0.20 g kcal -1 )/starting body <span class="hlt">mass</span>] × 100. Changes in body <span class="hlt">mass</span> occur because of flux in liquids, solids and gases. This knowledge is crucial for understanding metabolism, health and human water needs. In exercise science, corrections to observed changes in body <span class="hlt">mass</span> to estimate water <span class="hlt">balance</span> are inconsistently applied and often misinterpreted, particularly after prolonged exercise. Although acute body <span class="hlt">mass</span> losses in response to exercise can represent a close surrogate for body water losses, the discordance between <span class="hlt">mass</span> and water <span class="hlt">balance</span> equivalence becomes increasingly inaccurate as more and more energy is expended. The purpose of this paper is briefly to clarify the roles that respiratory water loss, gas exchange and metabolic water production play in the correction of body <span class="hlt">mass</span> changes for fluid <span class="hlt">balance</span> determinations during prolonged exercise. Computations do not include waters of association with glycogen because any movement of water among body water compartments contributes nothing to water or <span class="hlt">mass</span> flux from the body. Estimates of sweat loss from changes in body <span class="hlt">mass</span> should adjust for non-sweat losses when possible. We propose use of the following equation as a way of simplifying the study of exercise <span class="hlt">mass</span> and water <span class="hlt">balance</span>: ∆body <span class="hlt">mass</span> - 0.20 g kcal -1 = ∆body water. This equation directly controls for the influence of energy expenditure on body <span class="hlt">mass</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JGRC..117.9031G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JGRC..117.9031G"><span>Modeling the basal melting and marine <span class="hlt">ice</span> accretion of the Amery <span class="hlt">Ice</span> Shelf</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Galton-Fenzi, B. K.; Hunter, J. R.; Coleman, R.; Marsland, S. J.; Warner, R. C.</p> <p>2012-09-01</p> <p>The basal <span class="hlt">mass</span> <span class="hlt">balance</span> of the Amery <span class="hlt">Ice</span> Shelf (AIS) in East Antarctica is investigated using a numerical ocean model. The main improvements of this model over previous studies are the inclusion of frazil formation and dynamics, tides and the use of the latest estimate of the sub-<span class="hlt">ice</span>-shelf cavity geometry. The model produces a net basal melt rate of 45.6 Gt year-1 (0.74 m <span class="hlt">ice</span> year-1) which is in good agreement with reviewed observations. The melting at the base of the <span class="hlt">ice</span> shelf is primarily due to interaction with High Salinity Shelf Water created from the surface sea-<span class="hlt">ice</span> formation in winter. The temperature difference between the coldest waters created in the open ocean and the in situ freezing point of ocean water in contact with the deepest part of the AIS drives a melt rate that can exceed 30 m of <span class="hlt">ice</span> year-1. The inclusion of frazil dynamics is shown to be important for both melting and marine <span class="hlt">ice</span> accretion (refreezing). Frazil initially forms in the supercooled water layer adjacent to the base of the <span class="hlt">ice</span> shelf. The net accretion of marine <span class="hlt">ice</span> is 5.3 Gt year-1, comprised of 3.7 Gt year-1 of frazil accretion and 1.6 Gt year-1 of direct basal refreezing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JGRC..11211013D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JGRC..11211013D"><span>Influence of sea <span class="hlt">ice</span> cover and icebergs on circulation and water <span class="hlt">mass</span> formation in a numerical circulation model of the Ross Sea, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dinniman, Michael S.; Klinck, John M.; Smith, Walker O.</p> <p>2007-11-01</p> <p>Satellite imagery shows that there was substantial variability in the sea <span class="hlt">ice</span> extent in the Ross Sea during 2001-2003. Much of this variability is thought to be due to several large icebergs that moved through the area during that period. The effects of these changes in sea <span class="hlt">ice</span> on circulation and water <span class="hlt">mass</span> distributions are investigated with a numerical general circulation model. It would be difficult to simulate the highly variable sea <span class="hlt">ice</span> from 2001 to 2003 with a dynamic sea <span class="hlt">ice</span> model since much of the variability was due to the floating icebergs. Here, sea <span class="hlt">ice</span> concentration is specified from satellite observations. To examine the effects of changes in sea <span class="hlt">ice</span> due to iceberg C-19, simulations were performed using either climatological <span class="hlt">ice</span> concentrations or the observed <span class="hlt">ice</span> for that period. The heat <span class="hlt">balance</span> around the Ross Sea Polynya (RSP) shows that the dominant term in the surface heat budget is the net exchange with the atmosphere, but advection of oceanic warm water is also important. The area average annual basal melt rate beneath the Ross <span class="hlt">Ice</span> Shelf is reduced by 12% in the observed sea <span class="hlt">ice</span> simulation. The observed sea <span class="hlt">ice</span> simulation also creates more High-Salinity Shelf Water. Another simulation was performed with observed sea <span class="hlt">ice</span> and a fixed iceberg representing B-15A. There is reduced advection of warm surface water during summer from the RSP into McMurdo Sound due to B-15A, but a much stronger reduction is due to the late opening of the RSP in early 2003 because of C-19.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23404697','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23404697"><span>Probabilistic framework for assessing the <span class="hlt">ice</span> sheet contribution to sea level change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Little, Christopher M; Urban, Nathan M; Oppenheimer, Michael</p> <p>2013-02-26</p> <p>Previous sea level rise (SLR) assessments have excluded the potential for dynamic <span class="hlt">ice</span> loss over much of Greenland and Antarctica, and recently proposed "upper bounds" on Antarctica's 21st-century SLR contribution are derived principally from regions where present-day <span class="hlt">mass</span> loss is concentrated (basin 15, or B15, drained largely by Pine Island, Thwaites, and Smith glaciers). Here, we present a probabilistic framework for assessing the <span class="hlt">ice</span> sheet contribution to sea level change that explicitly accounts for <span class="hlt">mass</span> <span class="hlt">balance</span> uncertainty over an entire <span class="hlt">ice</span> sheet. Applying this framework to Antarctica, we find that ongoing <span class="hlt">mass</span> imbalances in non-B15 basins give an SLR contribution by 2100 that: (i) is comparable to projected changes in B15 discharge and Antarctica's surface <span class="hlt">mass</span> <span class="hlt">balance</span>, and (ii) varies widely depending on the subset of basins and observational dataset used in projections. Increases in discharge uncertainty, or decreases in the exceedance probability used to define an upper bound, increase the fractional contribution of non-B15 basins; even weak spatial correlations in future discharge growth rates markedly enhance this sensitivity. Although these projections rely on poorly constrained statistical parameters, they may be updated with observations and/or models at many spatial scales, facilitating a more comprehensive account of uncertainty that, if implemented, will improve future assessments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C11A0640M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C11A0640M"><span>Estimating Regional <span class="hlt">Mass</span> <span class="hlt">Balance</span> of Himalayan Glaciers Using Hexagon Imagery: An Automated Approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maurer, J. M.; Rupper, S.</p> <p>2013-12-01</p> <p>Currently there is much uncertainty regarding the present and future state of Himalayan glaciers, which supply meltwater for river systems vital to more than 1.4 billion people living throughout Asia. Previous assessments of regional glacier <span class="hlt">mass</span> <span class="hlt">balance</span> in the Himalayas using various remote sensing and field-based methods give inconsistent results, and most assessments are over relatively short (e.g., single decade) timescales. This study aims to quantify multi-decadal changes in volume and extent of Himalayan glaciers through efficient use of the large database of declassified 1970-80s era Hexagon stereo imagery. Automation of the DEM extraction process provides an effective workflow for many images to be processed and glacier elevation changes quantified with minimal user input. The tedious procedure of manual ground control point selection necessary for block-bundle adjustment (as ephemeral data is not available for the declassified images) is automated using the Maximally Stable Extremal Regions algorithm, which matches image elements between raw Hexagon images and georeferenced Landsat 15 meter panchromatic images. Additional automated Hexagon DEM processing, co-registration, and bias correction allow for direct comparison with modern ASTER and SRTM elevation data, thus quantifying glacier elevation and area changes over several decades across largely inaccessible mountainous regions. As consistent methodology is used for all glaciers, results will likely reveal significant spatial and temporal patterns in regional <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>. Ultimately, these findings could have important implications for future water resource management in light of environmental change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11..805Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11..805Z"><span>Sensitivity, stability and future evolution of the world's northernmost <span class="hlt">ice</span> cap, Hans Tausen Iskappe (Greenland)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zekollari, Harry; Huybrechts, Philippe; Noël, Brice; van de Berg, Willem Jan; van den Broeke, Michiel R.</p> <p>2017-03-01</p> <p>In this study the dynamics and sensitivity of Hans Tausen Iskappe (western Peary Land, Greenland) to climatic forcing is investigated with a coupled <span class="hlt">ice</span> flow-<span class="hlt">mass</span> <span class="hlt">balance</span> model. The surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) is calculated from a precipitation field obtained from the Regional Atmospheric Climate Model (RACMO2.3), while runoff is calculated from a positive-degree-day runoff-retention model. For the <span class="hlt">ice</span> flow a 3-D higher-order thermomechanical model is used, which is run at a 250 m resolution. A higher-order solution is needed to accurately represent the <span class="hlt">ice</span> flow in the outlet glaciers. Under 1961-1990 climatic conditions a steady-state <span class="hlt">ice</span> cap is obtained that is overall similar in geometry to the present-day <span class="hlt">ice</span> cap. <span class="hlt">Ice</span> thickness, temperature and flow velocity in the interior agree well with observations. For the outlet glaciers a reasonable agreement with temperature and <span class="hlt">ice</span> thickness measurements can be obtained with an additional heat source related to infiltrating meltwater. The simulations indicate that the SMB-elevation feedback has a major effect on the <span class="hlt">ice</span> cap response time and stability. This causes the southern part of the <span class="hlt">ice</span> cap to be extremely sensitive to a change in climatic conditions and leads to thresholds in the <span class="hlt">ice</span> cap evolution. Under constant 2005-2014 climatic conditions the entire southern part of the <span class="hlt">ice</span> cap cannot be sustained, and the <span class="hlt">ice</span> cap loses about 80 % of its present-day volume. The projected loss of surrounding permanent sea <span class="hlt">ice</span> and resultant precipitation increase may attenuate the future <span class="hlt">mass</span> loss but will be insufficient to preserve the present-day <span class="hlt">ice</span> cap for most scenarios. In a warmer and wetter climate the <span class="hlt">ice</span> margin will retreat, while the interior is projected to thicken, leading to a steeper <span class="hlt">ice</span> cap, in line with the present-day observed trends. For intermediate- (+4 °C) and high- warming scenarios (+8 °C) the <span class="hlt">ice</span> cap is projected to disappear around AD 2400 and 2200 respectively, almost independent of the projected</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017RCD....22..677C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017RCD....22..677C"><span>Are nonsymmetric <span class="hlt">balanced</span> configurations of four equal <span class="hlt">masses</span> virtual or real?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chenciner, Alain</p> <p>2017-11-01</p> <p><span class="hlt">Balanced</span> configurations of N point <span class="hlt">masses</span> are the configurations which, in a Euclidean space of high enough dimension, i. e., up to 2( N - 1), admit a relative equilibrium motion under the Newtonian (or similar) attraction. Central configurations are <span class="hlt">balanced</span> and it has been proved by Alain Albouy that central configurations of four equal <span class="hlt">masses</span> necessarily possess a symmetry axis, from which followed a proof that the number of such configurations up to similarity is finite and explicitly describable. It is known that <span class="hlt">balanced</span> configurations of three equal <span class="hlt">masses</span> are exactly the isosceles triangles, but it is not known whether <span class="hlt">balanced</span> configurations of four equal <span class="hlt">masses</span> must have some symmetry. As <span class="hlt">balanced</span> configurations come in families, it makes sense to look for possible branches of nonsymmetric <span class="hlt">balanced</span> configurations bifurcating from the subset of symmetric ones. In the simpler case of a logarithmic potential, the subset of symmetric <span class="hlt">balanced</span> configurations of four equal <span class="hlt">masses</span> is easy to describe as well as the bifurcation locus, but there is a grain of salt: expressed in terms of the squared mutual distances, this locus lies almost completely outside the set of true configurations (i. e., generalizations of triangular inequalities are not satisfied) and hence could lead most of the time only to the bifurcation of a branch of virtual nonsymmetric <span class="hlt">balanced</span> configurations. Nevertheless, a tiny piece of the bifurcation locus lies within the subset of real <span class="hlt">balanced</span> configurations symmetric with respect to a line and hence has a chance to lead to the bifurcation of real nonsymmetric <span class="hlt">balanced</span> configurations. This raises the question of the title, a question which, thanks to the explicit description given here, should be solvable by computer experts even in the Newtonian case. Another interesting question is about the possibility for a bifurcating branch of virtual nonsymmetric <span class="hlt">balanced</span> configurations to come back to the domain of true configurations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C32B..02W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C32B..02W"><span>Snow accumulation on Arctic sea <span class="hlt">ice</span>: is it a matter of how much or when?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Webster, M.; Petty, A.; Boisvert, L.; Markus, T.</p> <p>2017-12-01</p> <p>Snow on sea <span class="hlt">ice</span> plays an important, yet sometimes opposing role in sea <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> depending on the season. In autumn and winter, snow reduces the heat exchange from the ocean to the atmosphere, reducing sea <span class="hlt">ice</span> growth. In spring and summer, snow shields sea <span class="hlt">ice</span> from solar radiation, delaying sea <span class="hlt">ice</span> surface melt. Changes in snow depth and distribution in any season therefore directly affect the <span class="hlt">mass</span> <span class="hlt">balance</span> of Arctic sea <span class="hlt">ice</span>. In the western Arctic, a decreasing trend in spring snow depth distribution has been observed and attributed to the combined effect of peak snowfall rates in autumn and the coincident delay in sea <span class="hlt">ice</span> freeze-up. Here, we build on this work and present an in-depth analysis on the relationship between snow accumulation and the timing of sea <span class="hlt">ice</span> freeze-up across all Arctic regions. A newly developed two-layer snow model is forced with eight reanalysis precipitation products to: (1) identify the seasonal distribution of snowfall accumulation for different regions, (2) highlight which regions are most sensitive to the timing of sea <span class="hlt">ice</span> freeze-up with regard to snow accumulation, and (3) show, if precipitation were to increase, which regions would be most susceptible to thicker snow covers. We also utilize a comprehensive sensitivity study to better understand the factors most important in controlling winter/spring snow depths, and to explore what could happen to snow depth on sea <span class="hlt">ice</span> in a warming Arctic climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010TCD.....4.1307M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010TCD.....4.1307M"><span>The Potsdam Parallel <span class="hlt">Ice</span> Sheet Model (PISM-PIK) - Part 2: Dynamic equilibrium simulation of the Antarctic <span class="hlt">ice</span> sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martin, M. A.; Winkelmann, R.; Haseloff, M.; Albrecht, T.; Bueler, E.; Khroulev, C.; Levermann, A.</p> <p>2010-08-01</p> <p>We present a dynamic equilibrium simulation of the <span class="hlt">ice</span> sheet-shelf system on Antarctica with the Potsdam Parallel <span class="hlt">Ice</span> Sheet Model (PISM-PIK). The simulation is initialized with present-day conditions for topography and <span class="hlt">ice</span> thickness and then run to steady state with constant present-day surface <span class="hlt">mass</span> <span class="hlt">balance</span>. Surface temperature and basal melt distribution are parameterized. Grounding lines and calving fronts are free to evolve, and their modeled equilibrium state is compared to observational data. A physically-motivated dynamic calving law based on horizontal spreading rates allows for realistic calving fronts for various types of shelves. Steady-state dynamics including surface velocity and <span class="hlt">ice</span> flux are analyzed for whole Antarctica and the Ronne-Filchner and Ross <span class="hlt">ice</span> shelf areas in particular. The results show that the different flow regimes in sheet and shelves, and the transition zone between them, are captured reasonably well, supporting the approach of superposition of SIA and SSA for the representation of fast motion of grounded <span class="hlt">ice</span>. This approach also leads to a natural emergence of streams in this new 3-D marine <span class="hlt">ice</span> sheet model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.6421B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.6421B"><span>Summary of the SeaRISE Project's Experiments on Modeled <span class="hlt">Ice</span>-Sheet Contributions to Future Sea Level: Linearities and Non-linearities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bindschadler, Robert</p> <p>2013-04-01</p> <p>The SeaRISE (Sea-level Response to <span class="hlt">Ice</span> Sheet Evolution) project achieved <span class="hlt">ice</span>-sheet model ensemble responses to a variety of prescribed changes to surface <span class="hlt">mass</span> <span class="hlt">balance</span>, basal sliding and ocean boundary melting. Greenland <span class="hlt">ice</span> sheet models are more sensitive than Antarctic <span class="hlt">ice</span> sheet models to likely atmospheric changes in surface <span class="hlt">mass</span> <span class="hlt">balance</span>, while Antarctic models are most sensitive to basal melting of its <span class="hlt">ice</span> shelves. An experiment approximating the IPCC's RCP8.5 scenario produces first century contributions to sea level of 22.3 and 7.3 cm from Greenland and Antarctica, respectively, with a range among models of 62 and 17 cm, respectively. By 200 years, these projections increase to 53.2 and 23.4 cm, respectively, with ranges of 79 and 57 cm. The considerable range among models was not only in the magnitude of <span class="hlt">ice</span> lost, but also in the spatial pattern of response to identical forcing. Despite this variation, the response of any single model to a large range in the forcing intensity was remarkably linear in most cases. Additionally, the results of sensitivity experiments to single types of forcing (i.e., only one of the surface <span class="hlt">mass</span> <span class="hlt">balance</span>, or basal sliding, or ocean boundary melting) could be summed to accurately predict any model's result for an experiment when multiple forcings were applied simultaneously. This suggests a limited amount of feedback through the <span class="hlt">ice</span> sheet's internal dynamics between these types of forcing over the time scale of a few centuries (SeaRISE experiments lasted 500 years).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/imap/i-2600-h/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/imap/i-2600-h/"><span>Coastal-Change and Glaciological Map of the Northern Ross <span class="hlt">Ice</span> Shelf Area, Antarctica: 1962-2004</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ferrigno, Jane G.; Foley, Kevin M.; Swithinbank, Charles; Williams, Richard S.</p> <p>2007-01-01</p> <p>Changes in the area and volume of polar <span class="hlt">ice</span> sheets are intricately linked to changes in global climate, and the resulting changes in sea level could severely impact the densely populated coastal regions on Earth. Melting of the West Antarctic part alone of the Antarctic <span class="hlt">ice</span> sheet would cause a sea-level rise of approximately 6 meters (m). The potential sea-level rise after melting of the entire Antarctic <span class="hlt">ice</span> sheet is estimated to be 65 m (Lythe and others, 2001) to 73 m (Williams and Hall, 1993). The <span class="hlt">mass</span> <span class="hlt">balance</span> (the net volumetric gain or loss) of the Antarctic <span class="hlt">ice</span> sheet is highly complex, responding differently to different conditions in each region (Vaughan, 2005). In a review paper, Rignot and Thomas (2002) concluded that the West Antarctic <span class="hlt">ice</span> sheet is probably becoming thinner overall; although it is thickening in the west, it is thinning in the north. Thomas and others (2004), on the basis of aircraft and satellite laser altimetry surveys, believe the thinning may be accelerating. Joughin and Tulaczyk (2002), on the basis of analysis of <span class="hlt">ice</span>-flow velocities derived from synthetic aperture radar, concluded that most of the Ross <span class="hlt">ice</span> streams (<span class="hlt">ice</span> streams on the east side of the Ross <span class="hlt">Ice</span> Shelf) have a positive <span class="hlt">mass</span> <span class="hlt">balance</span>, whereas Rignot and others (2004) infer even larger negative <span class="hlt">mass</span> <span class="hlt">balance</span> for glaciers flowing northward into the Amundsen Sea, a trend suggested by Swithinbank and others (2003a,b; 2004). The <span class="hlt">mass</span> <span class="hlt">balance</span> of the East Antarctic <span class="hlt">ice</span> sheet is thought by Davis and others (2005) to be strongly positive on the basis of the change in satellite altimetry measurements made between 1992 and 2003. Measurement of changes in area and <span class="hlt">mass</span> <span class="hlt">balance</span> of the Antarctic <span class="hlt">ice</span> sheet was given a very high priority in recommendations by the Polar Research Board of the National Research Council (1986), in subsequent recommendations by the Scientific Committee on Antarctic Research (SCAR) (1989, 1993), and by the National Science Foundation?s (1990) Division of Polar</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AHEEM..64..115S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AHEEM..64..115S"><span>SPH Modelling of Sea-<span class="hlt">ice</span> Pack Dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Staroszczyk, Ryszard</p> <p>2017-12-01</p> <p>The paper is concerned with the problem of sea-<span class="hlt">ice</span> pack motion and deformation under the action of wind and water currents. Differential equations describing the dynamics of <span class="hlt">ice</span>, with its very distinct mateFfigrial responses in converging and diverging flows, express the <span class="hlt">mass</span> and linear momentum <span class="hlt">balances</span> on the horizontal plane (the free surface of the ocean). These equations are solved by the fully Lagrangian method of smoothed particle hydrodynamics (SPH). Assuming that the <span class="hlt">ice</span> behaviour can be approximated by a non-linearly viscous rheology, the proposed SPH model has been used to simulate the evolution of a sea-<span class="hlt">ice</span> pack driven by wind drag stresses. The results of numerical simulations illustrate the evolution of an <span class="hlt">ice</span> pack, including variations in <span class="hlt">ice</span> thickness and <span class="hlt">ice</span> area fraction in space and time. The effects of different initial <span class="hlt">ice</span> pack configurations and of different conditions assumed at the coast-<span class="hlt">ice</span> interface are examined. In particular, the SPH model is applied to a pack flow driven by a vortex wind to demonstrate how well the Lagrangian formulation can capture large deformations and displacements of sea <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C11C0785G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C11C0785G"><span>Modelled and observed <span class="hlt">mass</span> <span class="hlt">balance</span> of Rikha Samba Glacier, Nepal, Central Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gurung, T. R.; Kayastha, R. B.; Fujita, K.; Sinisalo, A. K.; Stumm, D.; Joshi, S.; Litt, M.</p> <p>2016-12-01</p> <p>Glacier <span class="hlt">mass</span> <span class="hlt">balance</span> variability has an implication for the regional water resources and it helps to understand the response of glacier to climate change in the Himalayan region. Several <span class="hlt">mass</span> <span class="hlt">balance</span> studies have been started in the Himalayan region since 1970s, but they are characterized by frequent temporal gaps and a poor spatial representatively. This study aims at bridging the temporal gaps in a long term <span class="hlt">mass</span> <span class="hlt">balance</span> series of the Rikha Samba glacier (5383 - 6475 m a.s.l.), a benchmark glacier located in the Hidden Valley, Mustang, Nepal. The ERA Interim reanalysis data for the period 2011-2015 is calibrated with the observed meteorological variables from an AWS installed near the glacier terminus. We apply an energy <span class="hlt">mass</span> <span class="hlt">balance</span> model, validated with the available in-situ measurements for the years 1998 and 2011-2015. The results show that the glacier is shrinking at a moderate negative <span class="hlt">mass</span> <span class="hlt">balance</span> rate for the period 1995 to 2015 and the high altitude location of Rikha Samba also prevents a bigger <span class="hlt">mass</span> loss compared to other small Himalayan glaciers. Precipitation from July to January and the mean air temperature from June to October are the most influential climatic parameters of the annual <span class="hlt">mass</span> <span class="hlt">balance</span> variability of Rikha Samba glacier.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70197897','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70197897"><span>Local topography increasingly influences the <span class="hlt">mass</span> <span class="hlt">balance</span> of a retreating cirque glacier</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Florentine, Caitlyn; Harper, Joel T.; Fagre, Daniel B.; Moore, Johnnie; Peitzsch, Erich H.</p> <p>2018-01-01</p> <p>Local topographically driven processes – such as wind drifting, avalanching, and shading – are known to alter the relationship between the <span class="hlt">mass</span> <span class="hlt">balance</span> of small cirque glaciers and regional climate. Yet partitioning such local effects from regional climate influence has proven difficult, creating uncertainty in the climate representativeness of some glaciers. We address this problem for Sperry Glacier in Glacier National Park, USA, using field-measured surface <span class="hlt">mass</span> <span class="hlt">balance</span>, geodetic constraints on <span class="hlt">mass</span> <span class="hlt">balance</span>, and regional climate data recorded at a network of meteorological and snow stations. Geodetically derived <span class="hlt">mass</span> changes during 1950–1960, 1960–2005, and 2005–2014 document average <span class="hlt">mass</span> change rates during each period at −0.22 ± 0.12, −0.18 ± 0.05, and −0.10 ± 0.03 m w.e. yr−1, respectively. A correlation of field-measured <span class="hlt">mass</span> <span class="hlt">balance</span> and regional climate variables closely (i.e., within 0.08 m w.e. yr−1) predicts the geodetically measured <span class="hlt">mass</span> loss from 2005 to 2014. However, this correlation overestimates glacier <span class="hlt">mass</span> <span class="hlt">balance</span> for 1950–1960 by +1.20 ± 0.95 m w.e. yr−1. Our analysis suggests that local effects, not represented in regional climate variables, have become a more dominant driver of the net <span class="hlt">mass</span> <span class="hlt">balance</span> as the glacier lost 0.50 km2 and retreated further into its cirque.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC43J..06R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC43J..06R"><span>The direct mechanical influence of sea <span class="hlt">ice</span> state on <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss via iceberg mélange</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Robel, A.</p> <p>2017-12-01</p> <p>The interaction between sea <span class="hlt">ice</span> and land <span class="hlt">ice</span> has typically been considered as a large-scale exchange of moisture, heat and salinity through the ocean and atmosphere. However, recent observations from marine-terminating glaciers in Greenland indicate that the long-term decline of local sea <span class="hlt">ice</span> cover has been accompanied by an increase in nearby iceberg calving and associated <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss. Near glacier calving fronts, sea <span class="hlt">ice</span> binds icebergs together into an aggregate granular material known as iceberg mélange. Studies have hypothesized that mélange may suppress calving by exerting a mechanical buttressing force directly on the glacier terminus. Here, we show explicitly how sea <span class="hlt">ice</span> thickness and concentration play a critical role in setting the material strength of mélange. To do so, we adapt a discrete element model to simulate mélange as a cohesive granular material. In these simulations, mélange laden with thick, dense, landfast sea <span class="hlt">ice</span> can produce enough resistance to shut down calving at the terminus. When sea <span class="hlt">ice</span> thins, mélange weakens, reducing the mechanical force of mélange on the glacier terminus, and increasing the likelihood of calving. We discuss whether longer periods of sea-<span class="hlt">ice</span>-free conditions in winter may lead to a transition from currently slow calving, predominantly occurring in the summer, to rapid calving, occurring throughout the year. We also discuss the potential role of freshwater discharge in promoting sea <span class="hlt">ice</span> formation in fjords, potentially strengthening mélange.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=science+AND+fats&pg=3&id=EJ829450','ERIC'); return false;" href="https://eric.ed.gov/?q=science+AND+fats&pg=3&id=EJ829450"><span>Teaching Process Engineering Principles Using an <span class="hlt">Ice</span> Cream Maker</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Kaletunc, Gonul; Duemmel, Kevin; Gecik, Christopher</p> <p>2007-01-01</p> <p>The <span class="hlt">ice</span> cream laboratory experiment is designed to illustrate and promote discussion of several engineering and science topics including material and energy <span class="hlt">balances</span>, heat transfer, freezing, <span class="hlt">mass</span> transfer, mixing, viscosity, and freezing point depression in a sophomore level engineering class. A pre-lab assignment requires the students to develop…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007E%26PSL.264..391S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007E%26PSL.264..391S"><span>Regional <span class="hlt">ice-mass</span> changes and glacial-isostatic adjustment in Antarctica from GRACE</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sasgen, Ingo; Martinec, Zdeněk; Fleming, Kevin</p> <p>2007-12-01</p> <p>We infer regional <span class="hlt">mass</span> changes in Antarctica using ca. 4 years of Gravity Recovery and Climate Experiment (GRACE) level 2 data. We decompose the time series of the Stokes coefficients into their linear as well as annual and semi-annual components by a least-squares adjustment and apply a statistical reliability test to the Stokes potential-coefficients' linear temporal trends. <span class="hlt">Mass</span> changes in three regions of Antarctica that display prominent geoid-height change are determined by adjusting predictions of glacier melting at the tip of the Antarctic Peninsula and in the Amundsen Sea Sector, and of the glacial-isostatic adjustment (GIA) over the Ronne <span class="hlt">Ice</span> Shelf. We use the GFZ RL04, CNES RL01C, JPL RL04 and CSR RL04 potential-coefficient releases, and show that, although all data sets consistently reflect the prominent <span class="hlt">mass</span> changes, differences in the <span class="hlt">mass</span>-change estimates are considerably larger than the uncertainties estimated by the propagation of the GRACE errors. We then use the bootstrapping method based on the four releases and six time intervals, each with 3.5 years of data, to quantify the variability of the mean <span class="hlt">mass</span>-change estimates. We find 95% of our estimates to lie within 0.08 and 0.09 mm/a equivalent sea-level (ESL) change for the Antarctic Peninsula and within 0.18 and 0.20 mm/a ESL for the Amundsen Sea Sector. Forward modelling of the GIA over the Ronne <span class="hlt">Ice</span> Shelf region suggests that the Antarctic continent was covered by 8.4 to 9.4 m ESL of additional <span class="hlt">ice</span> during the Last-Glacial Maximum (ca. 22 to 15 ka BP). With regards to the mantle-viscosity values and the glacial history used, this value is considered as a minimum estimate. The <span class="hlt">mass</span>-change estimates derived from all GRACE releases and time intervals lie within ca. 20% (Amundsen Sea Sector), 30% (Antarctic Peninsula) and 50% (Ronne <span class="hlt">Ice</span> Shelf region) of the bootstrap-estimated mean, demonstrating the reliability of results obtained using GRACE observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12...39B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12...39B"><span>Influence of temperature fluctuations on equilibrium <br class="break"/><span class="hlt">ice</span> sheet volume</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bøgeholm Mikkelsen, Troels; Grinsted, Aslak; Ditlevsen, Peter</p> <p>2018-01-01</p> <p>Forecasting the future sea level relies on accurate modeling of the response of the Greenland and Antarctic <span class="hlt">ice</span> sheets to changing temperatures. The surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) of the Greenland <span class="hlt">Ice</span> Sheet (GrIS) has a nonlinear response to warming. Cold and warm anomalies of equal size do not cancel out and it is therefore important to consider the effect of interannual fluctuations in temperature. We find that the steady-state volume of an <span class="hlt">ice</span> sheet is biased toward larger size if interannual temperature fluctuations are not taken into account in numerical modeling of the <span class="hlt">ice</span> sheet. We illustrate this in a simple <span class="hlt">ice</span> sheet model and find that the equilibrium <span class="hlt">ice</span> volume is approximately 1 m SLE (meters sea level equivalent) smaller when the simple model is forced with fluctuating temperatures as opposed to a stable climate. It is therefore important to consider the effect of interannual temperature fluctuations when designing long experiments such as paleo-spin-ups. We show how the magnitude of the potential bias can be quantified statistically. For recent simulations of the Greenland <span class="hlt">Ice</span> Sheet, we estimate the bias to be 30 Gt yr-1 (24-59 Gt yr-1, 95 % credibility) for a warming of 3 °C above preindustrial values, or 13 % (10-25, 95 % credibility) of the present-day rate of <span class="hlt">ice</span> loss. Models of the Greenland <span class="hlt">Ice</span> Sheet show a collapse threshold beyond which the <span class="hlt">ice</span> sheet becomes unsustainable. The proximity of the threshold will be underestimated if temperature fluctuations are not taken into account. We estimate the bias to be 0.12 °C (0.10-0.18 °C, 95 % credibility) for a recent estimate of the threshold. In light of our findings it is important to gauge the extent to which this increased variability will influence the <span class="hlt">mass</span> <span class="hlt">balance</span> of the <span class="hlt">ice</span> sheets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C51A0254Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C51A0254Y"><span>Modelling the Climate - Greenland <span class="hlt">Ice</span> Sheet Interaction in the Coupled <span class="hlt">Ice</span>-sheet/Climate Model EC-EARTH - PISM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, S.; Madsen, M. S.; Rodehacke, C. B.; Svendsen, S. H.; Adalgeirsdottir, G.</p> <p>2014-12-01</p> <p>Recent observations show that the Greenland <span class="hlt">ice</span> sheet (GrIS) has been losing <span class="hlt">mass</span> with an increasing speed during the past decades. Predicting the GrIS changes and their climate consequences relies on the understanding of the interaction of the GrIS with the climate system on both global and local scales, and requires climate model systems with an explicit and physically consistent <span class="hlt">ice</span> sheet module. A fully coupled global climate model with a dynamical <span class="hlt">ice</span> sheet model for the GrIS has recently been developed. The model system, EC-EARTH - PISM, consists of the EC-EARTH, an atmosphere, ocean and sea <span class="hlt">ice</span> model system, and the Parallel <span class="hlt">Ice</span> Sheet Model (PISM). The coupling of PISM includes a modified surface physical parameterization in EC-EARTH adapted to the land <span class="hlt">ice</span> surface over glaciated regions in Greenland. The PISM <span class="hlt">ice</span> sheet model is forced with the surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) directly computed inside the EC-EARTH atmospheric module and accounting for the precipitation, the surface evaporation, and the melting of snow and <span class="hlt">ice</span> over land <span class="hlt">ice</span>. PISM returns the simulated basal melt, <span class="hlt">ice</span> discharge and <span class="hlt">ice</span> cover (extent and thickness) as boundary conditions to EC-EARTH. This coupled system is <span class="hlt">mass</span> and energy conserving without being constrained by any anomaly correction or flux adjustment, and hence is suitable for investigation of <span class="hlt">ice</span> sheet - climate feedbacks. Three multi-century experiments for warm climate scenarios under (1) the RCP85 climate forcing, (2) an abrupt 4xCO2 and (3) an idealized 1% per year CO2 increase are performed using the coupled model system. The experiments are compared with their counterparts of the standard CMIP5 simulations (without the interactive <span class="hlt">ice</span> sheet) to evaluate the performance of the coupled system and to quantify the GrIS feedbacks. In particular, the evolution of the Greenland <span class="hlt">ice</span> sheet under the warm climate and its impacts on the climate system are investigated. Freshwater fluxes from the Greenland <span class="hlt">ice</span> sheet melt to the Arctic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28362423','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28362423"><span><span class="hlt">Ice</span> Generation and the Heat and <span class="hlt">Mass</span> Transfer Phenomena of Introducing Water to a Cold Bath of Brine.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yun, Xiao; Quarini, Giuseppe L</p> <p>2017-03-13</p> <p>We demonstrate a method for the study of the heat and <span class="hlt">mass</span> transfer and of the freezing phenomena in a subcooled brine environment. Our experiment showed that, under the proper conditions, <span class="hlt">ice</span> can be produced when water is introduced to a bath of cold brine. To make <span class="hlt">ice</span> form, in addition to having the brine and water mix, the rate of heat transfer must bypass that of <span class="hlt">mass</span> transfer. When water is introduced in the form of tiny droplets to the brine surface, the mode of heat and <span class="hlt">mass</span> transfer is by diffusion. The buoyancy stops water from mixing with the brine underneath, but as the <span class="hlt">ice</span> grows thicker, it slows down the rate of heat transfer, making <span class="hlt">ice</span> more difficult to grow as a result. When water is introduced inside the brine in the form of a flow, a number of factors are found to influence how much <span class="hlt">ice</span> can form. Brine temperature and concentration, which are the driving forces of heat and <span class="hlt">mass</span> transfer, respectively, can affect the water-to-<span class="hlt">ice</span> conversion ratio; lower bath temperatures and brine concentrations encourage more <span class="hlt">ice</span> to form. The flow rheology, which can directly affect both the heat and <span class="hlt">mass</span> transfer coefficients, is also a key factor. In addition, the flow rheology changes the area of contact of the flow with the bulk fluid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060022603','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060022603"><span>Oceanic Low Blows Hitting <span class="hlt">Ice</span> Sheets Where It Hurts</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bindschadler, Robert</p> <p>2006-01-01</p> <p>The recent acceleration, thinning and retreat of large outlet glaciers in both Antarctica and Greenland is altering the <span class="hlt">mass</span> <span class="hlt">balance</span> of these two large <span class="hlt">ice</span> sheets and increasing their contribution to rising sea level. In this short Perspective solicited by Science for a special March 24th issue on sea level change, I argue that the cause of these bihemispheric changes is that warmer water has gained access to the undersides of these glaciers where they come afloat from the continent. This process is particularly effective at accelerating glaciers because the beds of the large outlet glaciers are well below sea level (1000 meters or more) but "guarded" downstream by a shallow moraine formed when the glacier was more advanced. Once warmer water can breach this moraine, it sinks in the colder, fresh water behind the moraine and reaches the submarine front of the glacier. The pressure melting effect lowers the melting point of this deep <span class="hlt">ice</span> allowing the warmer water to melt <span class="hlt">ice</span> at rates of many tens of meters per year. This melting reduces . the frictional hold of the bed on the <span class="hlt">ice</span>, allowing the <span class="hlt">ice</span> to accelerate in agreement with the observations, Hansen has discussed the likelihood that approximately half of the Earth's radiation imbalance is manifesting in warmer ocean waters and Levitus et al. have seen warming in ocean temperature measurements at mid and low latitudes. The behavior of these outlet glaciers indicates this ocean warmth is reaching polar waters. The prognosis is for a continuation of this process, more negative <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balances</span> and increased rates of sea level rise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1910327R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1910327R"><span><span class="hlt">Mass-balance</span> modelling of Ak-Shyirak massif Glaciers, Inner Tian Shan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rets, Ekaterina; Barandun, Martina; Belozerov, Egor; Petrakov, Dmitry; Shpuntova, Alena</p> <p>2017-04-01</p> <p>Tian Shan is a water tower of Central Asia. Rapid and accelerating glacier downwasting is typical for this region. Study sites - Sary-Tor glacier and Glacier No.354 are located in Ak-Shyirak massif, Naryn headwaters. Sary-Tor was chosen as representative for Ak-Shyirak (Ushnurtsev, 1991; Oledeneniye TianShanya, 1995) for direct <span class="hlt">mass-balance</span> measurements in 1985-1991. Glacier No.354 was an object of direct <span class="hlt">mass-balance</span> measurements for 2011-2016. An energy-<span class="hlt">balance</span> distributed A-Melt model (Rets et al, 2010) was used to reconstruct <span class="hlt">mass-balance</span> for the glaciers for 2003-2015. Verification of modelingresults showed a good reproduction of direct melting measurements data on ablation stakes and <span class="hlt">mass</span> loss according to geodetic method. Modeling results for Glacier No. 354 were compared to different modeling approach: distributed accumulation and temperature-index melt (Kronenberg et al, 2016)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5426515','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5426515"><span>Sea-level feedback lowers projections of future Antarctic <span class="hlt">Ice</span>-Sheet <span class="hlt">mass</span> loss</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Gomez, Natalya; Pollard, David; Holland, David</p> <p>2015-01-01</p> <p>The stability of marine sectors of the Antarctic <span class="hlt">Ice</span> Sheet (AIS) in a warming climate has been identified as the largest source of uncertainty in projections of future sea-level rise. Sea-level fall near the grounding line of a retreating marine <span class="hlt">ice</span> sheet has a stabilizing influence on the <span class="hlt">ice</span> sheets, and previous studies have established the importance of this feedback on <span class="hlt">ice</span> age AIS evolution. Here we use a coupled <span class="hlt">ice</span> sheet–sea-level model to investigate the impact of the feedback mechanism on future AIS retreat over centennial and millennial timescales for a range of emission scenarios. We show that the combination of bedrock uplift and sea-surface drop associated with <span class="hlt">ice</span>-sheet retreat significantly reduces AIS <span class="hlt">mass</span> loss relative to a simulation without these effects included. Sensitivity analyses show that the stabilization tends to be greatest for lower emission scenarios and Earth models characterized by a thin elastic lithosphere and low-viscosity upper mantle, as is the case for West Antarctica. PMID:26554381</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1913594F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1913594F"><span>Surface elevation change over the Patagonia <span class="hlt">Ice</span> Fields using CryoSat-2 swath altimetry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Foresta, Luca; Gourmelen, Noel; José Escorihuela, MarÍa; Garcia Mondejar, Albert; Wuite, Jan; Shepherd, Andrew; Roca, Mònica; Nagler, Thomas; Brockley, David; Baker, Steven; Nienow, Pete</p> <p>2017-04-01</p> <p>Satellite altimetry has been traditionally used in the past few decades to infer elevation of land <span class="hlt">ice</span>, quantify changes in <span class="hlt">ice</span> topography and infer <span class="hlt">mass</span> <span class="hlt">balance</span> estimates over large and remote areas such as the Greenland and Antarctic <span class="hlt">ice</span> sheets. Radar Altimetry (RA) is particularly well suited to this task due to its all-weather year-round capability of observing the <span class="hlt">ice</span> surface. However, monitoring of <span class="hlt">ice</span> caps (area < 104 km^2) as well as mountain glaciers has proven more challenging. The large footprint of a conventional radar altimeter and relatively coarse ground track coverage are less suited to monitoring comparatively small regions with complex topography, so that <span class="hlt">mass</span> <span class="hlt">balance</span> estimates from RA rely on extrapolation methods to regionalize elevation change. Since 2010, the European Space Agency's CryoSat-2 (CS-2) satellite has collected <span class="hlt">ice</span> elevation measurements over <span class="hlt">ice</span> caps with its novel radar altimeter. CS-2 provides higher density of observations w.r.t. previous satellite altimeters, reduces the along-track footprint using Synthetic Aperture Radar (SAR) processing and locates the across-track origin of a surface reflector in the presence of a slope with SAR Interferometry (SARIn). Here, we exploit CS-2 as a swath altimeter [Hawley et al., 2009; Gray et al., 2013; Christie et al., 2016; Ignéczi et al., 2016, Foresta et al., 2016] over the Southern and Northern Patagonian <span class="hlt">Ice</span> Fields (SPI and NPI, respectively). The SPI and NPI are the two largest <span class="hlt">ice</span> <span class="hlt">masses</span> in the southern hemisphere outside of Antarctica and are thinning very rapidly in recent decades [e.g Rignot et al., 2003; Willis et al, 2012]. However, studies of surface, volume and <span class="hlt">mass</span> change in the literature, covering the entire SPI and NPI, are limited in number due to their remoteness, extremely complex topography and wide range of slopes. In this work, we present rates of surface elevation change for five glaciological years between 2011-2016 using swath-processed CS-2 SARIn heights and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C53A0693M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C53A0693M"><span>Multi-channel <span class="hlt">Ice</span> Penetrating Radar Traverse for Estimates of Firn Density in the Percolation Zone, Western Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meehan, T.; Osterberg, E. C.; Lewis, G.; Overly, T. B.; Hawley, R. L.; Bradford, J.; Marshall, H. P.</p> <p>2016-12-01</p> <p>To better predict the response of the Greenland <span class="hlt">Ice</span> Sheet (GrIS) to future warming, leading edge Regional Climate Models (RCM) must be calibrated with in situ measurements of recent accumulation and melt. <span class="hlt">Mass</span> <span class="hlt">balance</span> estimates averaged across the entire Greenland <span class="hlt">Ice</span> Sheet (GrIS) vary between models by more than 30 percent, and regional comparisons of <span class="hlt">mass</span> <span class="hlt">balance</span> reconstructions in Greenland vary by 100 percent or more. Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) is a multi-year and multi-disciplinary 1700 km science traverse from Raven/Dye2 in SW Greenland, to Summit Station. Multi-offset radar measurements can provide high accuracy electromagnetic (EM) velocity estimates of the firn to within (+-) 0.002 to 0.003 m/ns. EM velocity, in turn, can be used to estimate bulk firn density. Using a mixing equation such as the CRIM Equation we use the measured EM velocity, along with the known EM velocity in air and <span class="hlt">ice</span>, to estimate bulk density. During spring 2016, we used multi-channel 500MHz radar in a multi-offset configuration to survey more than 800 km from Raven towards summit. Preliminary radar-derived snow density estimates agree with density estimates from a firn core measurement ( 50 kg/m3), despite the lateral heterogeneity of the firn across the length of the antenna array (12 m).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25512537','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25512537"><span>Laser altimetry reveals complex pattern of Greenland <span class="hlt">Ice</span> Sheet dynamics.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Csatho, Beata M; Schenk, Anton F; van der Veen, Cornelis J; Babonis, Gregory; Duncan, Kyle; Rezvanbehbahani, Soroush; van den Broeke, Michiel R; Simonsen, Sebastian B; Nagarajan, Sudhagar; van Angelen, Jan H</p> <p>2014-12-30</p> <p>We present a new record of <span class="hlt">ice</span> thickness change, reconstructed at nearly 100,000 sites on the Greenland <span class="hlt">Ice</span> Sheet (GrIS) from laser altimetry measurements spanning the period 1993-2012, partitioned into changes due to surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) and <span class="hlt">ice</span> dynamics. We estimate a mean annual GrIS <span class="hlt">mass</span> loss of 243 ± 18 Gt ⋅ y(-1), equivalent to 0.68 mm ⋅ y(-1) sea level rise (SLR) for 2003-2009. Dynamic thinning contributed 48%, with the largest rates occurring in 2004-2006, followed by a gradual decrease <span class="hlt">balanced</span> by accelerating SMB loss. The spatial pattern of dynamic <span class="hlt">mass</span> loss changed over this time as dynamic thinning rapidly decreased in southeast Greenland but slowly increased in the southwest, north, and northeast regions. Most outlet glaciers have been thinning during the last two decades, interrupted by episodes of decreasing thinning or even thickening. Dynamics of the major outlet glaciers dominated the <span class="hlt">mass</span> loss from larger drainage basins, and simultaneous changes over distances up to 500 km are detected, indicating climate control. However, the intricate spatiotemporal pattern of dynamic thickness change suggests that, regardless of the forcing responsible for initial glacier acceleration and thinning, the response of individual glaciers is modulated by local conditions. Recent projections of dynamic contributions from the entire GrIS to SLR have been based on the extrapolation of four major outlet glaciers. Considering the observed complexity, we question how well these four glaciers represent all of Greenland's outlet glaciers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70021550','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70021550"><span>How many stakes are required to measure the <span class="hlt">mass</span> <span class="hlt">balance</span> of a glacier?</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Fountain, A.G.; Vecchia, A.</p> <p>1999-01-01</p> <p>Glacier <span class="hlt">mass</span> <span class="hlt">balance</span> is estimated for South Cascade Glacier and Maclure Glacier using a one-dimensional regression of <span class="hlt">mass</span> <span class="hlt">balance</span> with altitude as an alternative to the traditional approach of contouring <span class="hlt">mass</span> <span class="hlt">balance</span> values. One attractive feature of regression is that it can be applied to sparse data sets where contouring is not possible and can provide an objective error of the resulting estimate. Regression methods yielded <span class="hlt">mass</span> <span class="hlt">balance</span> values equivalent to contouring methods. The effect of the number of <span class="hlt">mass</span> <span class="hlt">balance</span> measurements on the final value for the glacier showed that sample sizes as small as five stakes provided reasonable estimates, although the error estimates were greater than for larger sample sizes. Different spatial patterns of measurement locations showed no appreciable influence on the final value as long as different surface altitudes were intermittently sampled over the altitude range of the glacier. Two different regression equations were examined, a quadratic, and a piecewise linear spline, and comparison of results showed little sensitivity to the type of equation. These results point to the dominant effect of the gradient of <span class="hlt">mass</span> <span class="hlt">balance</span> with altitude of alpine glaciers compared to transverse variations. The number of <span class="hlt">mass</span> <span class="hlt">balance</span> measurements required to determine the glacier <span class="hlt">balance</span> appears to be scale invariant for small glaciers and five to ten stakes are sufficient.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70030545','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70030545"><span>Glacier <span class="hlt">mass-balance</span> fluctuations in the Pacific Northwest and Alaska, USA</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Josberger, E.G.; Bidlake, W.R.; March, R.S.; Kennedy, B.W.</p> <p>2007-01-01</p> <p>The more than 40 year record of net and seasonal <span class="hlt">mass-balance</span> records from measurements made by the United States Geological Survey on South Cascade Glacier, Washington, and Wolverine and Gulkana Glaciers, Alaska, shows annual and interannual fluctuations that reflect changes in the controlling climatic conditions at regional and global scales. As the <span class="hlt">mass-balance</span> record grows in length, it is revealing significant changes in previously described glacier <span class="hlt">mass-balance</span> behavior, and both inter-glacier and glacier-climate relationships. South Cascade and Wolverine Glaciers are strongly affected by the warm and wet maritime climate of the northeast Pacific Ocean. Their net <span class="hlt">balances</span> have generally been controlled by winter accumulation, with fluctuations that are strongly related to the Pacific Decadal Oscillation (PDO). Recently, warm dry summers have begun to dominate the net <span class="hlt">balance</span> of the two maritime glaciers, with a weakening of the correlation between the winter <span class="hlt">balance</span> fluctuations and the PDO. Non-synchronous periods of positive and negative net <span class="hlt">balance</span> for each glacier prior to 1989 were followed by a 1989-2004 period of synchronous and almost exclusively negative net <span class="hlt">balances</span> that averaged -0.8 m for the three glaciers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C54A..02H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C54A..02H"><span><span class="hlt">Ice</span> shelf thickness change from 2010 to 2017</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hogg, A.; Shepherd, A.; Gilbert, L.; Muir, A. S.</p> <p>2017-12-01</p> <p>Floating <span class="hlt">ice</span> shelves fringe 74 % of Antarctica's coastline, providing a direct link between the <span class="hlt">ice</span> sheet and the surrounding oceans. Over the last 25 years, <span class="hlt">ice</span> shelves have retreated, thinned, and collapsed catastrophically. While change in the <span class="hlt">mass</span> of floating <span class="hlt">ice</span> shelves has only a modest steric impact on the rate of sea-level rise, their loss can affect the <span class="hlt">mass</span> <span class="hlt">balance</span> of the grounded <span class="hlt">ice</span>-sheet by influencing the rate of <span class="hlt">ice</span> flow inland, due to the buttressing effect. Here we use CryoSat-2 altimetry data to map the detailed pattern of <span class="hlt">ice</span> shelf thickness change in Antarctica. We exploit the dense spatial sampling and repeat coverage provided by the CryoSat-2 synthetic aperture radar interferometric mode (SARIn) to investigate data acquired between 2010 to the present day. We find that <span class="hlt">ice</span> shelf thinning rates can exhibit large fluctuations over short time periods, and that the improved spatial resolution of CryoSat-2 enables us to resolve the spatial pattern of thinning with ever greater detail in Antarctica. In the Amundsen Sea, <span class="hlt">ice</span> shelves at the terminus of the Pine Island and Thwaites glaciers have thinned at rates in excess of 5 meters per year for more than two decades. We observe the highest rates of basal melting near to the <span class="hlt">ice</span> sheet grounding line, reinforcing the importance of high resolution datasets. On the Antarctic Peninsula, in contrast to the 3.8 m per decade of thinning observed since 1992, we measure an increase in the surface elevation of the Larsen-C <span class="hlt">Ice</span>-Shelf during the CryoSat-2 period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12.1433G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12.1433G"><span>Design and results of the <span class="hlt">ice</span> sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goelzer, Heiko; Nowicki, Sophie; Edwards, Tamsin; Beckley, Matthew; Abe-Ouchi, Ayako; Aschwanden, Andy; Calov, Reinhard; Gagliardini, Olivier; Gillet-Chaulet, Fabien; Golledge, Nicholas R.; Gregory, Jonathan; Greve, Ralf; Humbert, Angelika; Huybrechts, Philippe; Kennedy, Joseph H.; Larour, Eric; Lipscomb, William H.; Le clec'h, Sébastien; Lee, Victoria; Morlighem, Mathieu; Pattyn, Frank; Payne, Antony J.; Rodehacke, Christian; Rückamp, Martin; Saito, Fuyuki; Schlegel, Nicole; Seroussi, Helene; Shepherd, Andrew; Sun, Sainan; van de Wal, Roderik; Ziemen, Florian A.</p> <p>2018-04-01</p> <p>Earlier large-scale Greenland <span class="hlt">ice</span> sheet sea-level projections (e.g. those run during the <span class="hlt">ice</span>2sea and SeaRISE initiatives) have shown that <span class="hlt">ice</span> sheet initial conditions have a large effect on the projections and give rise to important uncertainties. The goal of this initMIP-Greenland intercomparison exercise is to compare, evaluate, and improve the initialisation techniques used in the <span class="hlt">ice</span> sheet modelling community and to estimate the associated uncertainties in modelled <span class="hlt">mass</span> changes. initMIP-Greenland is the first in a series of <span class="hlt">ice</span> sheet model intercomparison activities within ISMIP6 (the <span class="hlt">Ice</span> Sheet Model Intercomparison Project for CMIP6), which is the primary activity within the Coupled Model Intercomparison Project Phase 6 (CMIP6) focusing on the <span class="hlt">ice</span> sheets. Two experiments for the large-scale Greenland <span class="hlt">ice</span> sheet have been designed to allow intercomparison between participating models of (1) the initial present-day state of the <span class="hlt">ice</span> sheet and (2) the response in two idealised forward experiments. The forward experiments serve to evaluate the initialisation in terms of model drift (forward run without additional forcing) and in response to a large perturbation (prescribed surface <span class="hlt">mass</span> <span class="hlt">balance</span> anomaly); they should not be interpreted as sea-level projections. We present and discuss results that highlight the diversity of data sets, boundary conditions, and initialisation techniques used in the community to generate initial states of the Greenland <span class="hlt">ice</span> sheet. We find good agreement across the ensemble for the dynamic response to surface <span class="hlt">mass</span> <span class="hlt">balance</span> changes in areas where the simulated <span class="hlt">ice</span> sheets overlap but differences arising from the initial size of the <span class="hlt">ice</span> sheet. The model drift in the control experiment is reduced for models that participated in earlier intercomparison exercises.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1436954-design-results-ice-sheet-model-initialisation-experiments-initmip-greenland-ismip6-intercomparison','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1436954-design-results-ice-sheet-model-initialisation-experiments-initmip-greenland-ismip6-intercomparison"><span>Design and results of the <span class="hlt">ice</span> sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Goelzer, Heiko; Nowicki, Sophie; Edwards, Tamsin; ...</p> <p>2018-04-19</p> <p>Earlier large-scale Greenland <span class="hlt">ice</span> sheet sea-level projections (e.g. those run during the <span class="hlt">ice</span>2sea and SeaRISE initiatives) have shown that <span class="hlt">ice</span> sheet initial conditions have a large effect on the projections and give rise to important uncertainties. Here, the goal of this initMIP-Greenland intercomparison exercise is to compare, evaluate, and improve the initialisation techniques used in the <span class="hlt">ice</span> sheet modelling community and to estimate the associated uncertainties in modelled <span class="hlt">mass</span> changes. initMIP-Greenland is the first in a series of <span class="hlt">ice</span> sheet model intercomparison activities within ISMIP6 (the <span class="hlt">Ice</span> Sheet Model Intercomparison Project for CMIP6), which is the primary activity within themore » Coupled Model Intercomparison Project Phase 6 (CMIP6) focusing on the <span class="hlt">ice</span> sheets. Two experiments for the large-scale Greenland <span class="hlt">ice</span> sheet have been designed to allow intercomparison between participating models of (1) the initial present-day state of the <span class="hlt">ice</span> sheet and (2) the response in two idealised forward experiments. The forward experiments serve to evaluate the initialisation in terms of model drift (forward run without additional forcing) and in response to a large perturbation (prescribed surface <span class="hlt">mass</span> <span class="hlt">balance</span> anomaly); they should not be interpreted as sea-level projections. We present and discuss results that highlight the diversity of data sets, boundary conditions, and initialisation techniques used in the community to generate initial states of the Greenland <span class="hlt">ice</span> sheet. We find good agreement across the ensemble for the dynamic response to surface <span class="hlt">mass</span> <span class="hlt">balance</span> changes in areas where the simulated <span class="hlt">ice</span> sheets overlap but differences arising from the initial size of the <span class="hlt">ice</span> sheet. The model drift in the control experiment is reduced for models that participated in earlier intercomparison exercises.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1436954','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1436954"><span>Design and results of the <span class="hlt">ice</span> sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Goelzer, Heiko; Nowicki, Sophie; Edwards, Tamsin</p> <p></p> <p>Earlier large-scale Greenland <span class="hlt">ice</span> sheet sea-level projections (e.g. those run during the <span class="hlt">ice</span>2sea and SeaRISE initiatives) have shown that <span class="hlt">ice</span> sheet initial conditions have a large effect on the projections and give rise to important uncertainties. Here, the goal of this initMIP-Greenland intercomparison exercise is to compare, evaluate, and improve the initialisation techniques used in the <span class="hlt">ice</span> sheet modelling community and to estimate the associated uncertainties in modelled <span class="hlt">mass</span> changes. initMIP-Greenland is the first in a series of <span class="hlt">ice</span> sheet model intercomparison activities within ISMIP6 (the <span class="hlt">Ice</span> Sheet Model Intercomparison Project for CMIP6), which is the primary activity within themore » Coupled Model Intercomparison Project Phase 6 (CMIP6) focusing on the <span class="hlt">ice</span> sheets. Two experiments for the large-scale Greenland <span class="hlt">ice</span> sheet have been designed to allow intercomparison between participating models of (1) the initial present-day state of the <span class="hlt">ice</span> sheet and (2) the response in two idealised forward experiments. The forward experiments serve to evaluate the initialisation in terms of model drift (forward run without additional forcing) and in response to a large perturbation (prescribed surface <span class="hlt">mass</span> <span class="hlt">balance</span> anomaly); they should not be interpreted as sea-level projections. We present and discuss results that highlight the diversity of data sets, boundary conditions, and initialisation techniques used in the community to generate initial states of the Greenland <span class="hlt">ice</span> sheet. We find good agreement across the ensemble for the dynamic response to surface <span class="hlt">mass</span> <span class="hlt">balance</span> changes in areas where the simulated <span class="hlt">ice</span> sheets overlap but differences arising from the initial size of the <span class="hlt">ice</span> sheet. The model drift in the control experiment is reduced for models that participated in earlier intercomparison exercises.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015TCD.....9..115L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015TCD.....9..115L"><span>Future projections of the climate and surface <span class="hlt">mass</span> <span class="hlt">balance</span> of Svalbard with the regional climate model MAR</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lang, C.; Fettweis, X.; Erpicum, M.</p> <p>2015-01-01</p> <p>We have performed future projections of the climate and surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) of Svalbard with the MAR regional climate model forced by the MIROC5 global model, following the RCP8.5 scenario at a spatial resolution of 10 km. MAR predicts a similar evolution of increasing surface melt everywhere in Svalbard followed by a sudden acceleration of the melt around 2050, with a larger melt increase in the south compared to the north of the archipelago and the <span class="hlt">ice</span> caps. This melt acceleration around 2050 is mainly driven by the albedo-melt feedback associated with the expansion of the ablation/bare <span class="hlt">ice</span> zone. This effect is dampened in part as the solar radiation itself is projected to decrease due to cloudiness increase. The near-surface temperature is projected to increase more in winter than in summer as the temperature is already close to 0 °C in summer. The model also projects a strong winter west-to-east temperature gradient, related to the large decrease of sea <span class="hlt">ice</span> cover around Svalbard. At the end of the century (2070-2099 mean), SMB is projected to be negative over the entire Svalbard and, by 2085, all glaciated regions of Svalbard are predicted to undergo net ablation, meaning that, under the RCP8.5 scenario, all the glaciers and <span class="hlt">ice</span> caps are predicted to start their irreversible retreat before the end of the 21st century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015TCD.....9.5647D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015TCD.....9.5647D"><span>Anomalously-dense firn in an <span class="hlt">ice</span>-shelf channel revealed by wide-angle radar</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drews, R.; Brown, J.; Matsuoka, K.; Witrant, E.; Philippe, M.; Hubbard, B.; Pattyn, F.</p> <p>2015-10-01</p> <p>The thickness of <span class="hlt">ice</span> shelves, a basic parameter for <span class="hlt">mass</span> <span class="hlt">balance</span> estimates, is typically inferred using hydrostatic equilibrium for which knowledge of the depth-averaged density is essential. The densification from snow to <span class="hlt">ice</span> depends on a number of local factors (e.g. temperature and surface <span class="hlt">mass</span> <span class="hlt">balance</span>) causing spatial and temporal variations in density-depth profiles. However, direct measurements of firn density are sparse, requiring substantial logistical effort. Here, we infer density from radio-wave propagation speed using ground-based wide-angle radar datasets (10 MHz) collected at five sites on Roi Baudouin <span class="hlt">Ice</span> Shelf (RBIS), Dronning Maud Land, Antarctica. Using a novel algorithm including traveltime inversion and raytracing with a prescribed shape of the depth-density relationship, we show that the depth to internal reflectors, the local <span class="hlt">ice</span> thickness and depth-averaged densities can reliably be reconstructed. For the particular case of an <span class="hlt">ice</span>-shelf channel, where <span class="hlt">ice</span> thickness and surface slope change substantially over a few kilometers, the radar data suggests that firn inside the channel is about 5 % denser than outside the channel. Although this density difference is at the detection limit of the radar, it is consistent with a similar density anomaly reconstructed from optical televiewing, which reveals 10 % denser firn inside compared to outside the channel. The denser firn in the <span class="hlt">ice</span>-shelf channel should be accounted for when using the hydrostatic <span class="hlt">ice</span> thickness for determining basal melt rates. The radar method presented here is robust and can easily be adapted to different radar frequencies and data-acquisition geometries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000070393&hterms=3G&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3D3G','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000070393&hterms=3G&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3D3G"><span>Measuring Greenland <span class="hlt">Ice</span> <span class="hlt">Mass</span> Variation With Gravity Recovery and the Climate Experiment Gravity and GPS</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wu, Xiao-Ping</p> <p>1999-01-01</p> <p>The response of the Greenland <span class="hlt">ice</span> sheet to climate change could significantly alter sea level. The <span class="hlt">ice</span> sheet was much thicker at the last glacial maximum. To gain insight into the global change process and the future trend, it is important to evaluate the <span class="hlt">ice</span> <span class="hlt">mass</span> variation as a function of time and space. The Gravity Recovery and Climate Experiment (GRACE) mission to fly in 2001 for 5 years will measure gravity changes associated with the current <span class="hlt">ice</span> variation and the solid earth's response to past variations. Our objective is to assess the separability of different change sources, accuracy and resolution in the <span class="hlt">mass</span> variation determination by the new gravity data and possible Global Positioning System (GPS) bedrock uplift measurements. We use a reference parameter state that follows a dynamic <span class="hlt">ice</span> model for current <span class="hlt">mass</span> variation and a variant of the Tushingham and Peltier <span class="hlt">ICE</span>-3G deglaciation model for historical deglaciation. The current linear trend is also assumed to have started 5 kyr ago. The Earth model is fixed as preliminary reference Earth model (PREM) with four viscoelastic layers. A discrete Bayesian inverse algorithm is developed employing an isotropic Gaussian a priori covariance function over the <span class="hlt">ice</span> sheet and time. We use data noise predicted by the University of Texas and JPL for major GRACE error sources. A 2 mm/yr uplift uncertainty is assumed for GPS occupation time of 5 years. We then carry out covariance analysis and inverse simulation using GRACE geoid coefficients up to degree 180 in conjunction with a number of GPS uplift rates. Present-day <span class="hlt">ice</span> <span class="hlt">mass</span> variation and historical deglaciation are solved simultaneously over 146 grids of roughly 110 km x 110 km and with 6 time increments of 3 kyr each, along with a common starting epoch of the current trend. For present-day <span class="hlt">ice</span> thickness change, the covariance analysis using GRACE geoid data alone results in a root mean square (RMS) posterior root variance of 2.6 cm/yr, with fairly large a priori</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=198404&Lab=NHEERL&keyword=herbicide&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=198404&Lab=NHEERL&keyword=herbicide&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>Results of the Lake Michigan <span class="hlt">Mass</span> <span class="hlt">Balance</span> Project: Atrazine Modeling Report</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>This report covers an overview of chemical properties, measurements in air and water, model construct and assumptions, and results of mathematical <span class="hlt">mass</span> <span class="hlt">balance</span> modeling of the herbicide atrazine in the Lake Michigan basin. Within the context of the <span class="hlt">mass</span> <span class="hlt">balance</span>, an overview of a...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1208660-changes-firn-structure-western-greenland-ice-sheet-caused-recent-warming','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1208660-changes-firn-structure-western-greenland-ice-sheet-caused-recent-warming"><span>Changes in the firn structure of the western Greenland <span class="hlt">Ice</span> Sheet caused by recent warming</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>de la Peña, S.; Howat, I. M.; Nienow, P. W.; ...</p> <p>2015-06-11</p> <p>Atmospheric warming over the Greenland <span class="hlt">Ice</span> Sheet during the last 2 decades has increased the amount of surface meltwater production, resulting in the migration of melt and percolation regimes to higher altitudes and an increase in the amount of <span class="hlt">ice</span> content from refrozen meltwater found in the firn above the superimposed <span class="hlt">ice</span> zone. Here we present field and airborne radar observations of buried <span class="hlt">ice</span> layers within the near-surface (0–20 m) firn in western Greenland, obtained from campaigns between 1998 and 2014. We find a sharp increase in firn-<span class="hlt">ice</span> content in the form of thick widespread layers in the percolation zone,more » which decreases the capacity of the firn to store meltwater. The estimated total annual <span class="hlt">ice</span> content retained in the near-surface firn in areas with positive surface <span class="hlt">mass</span> <span class="hlt">balance</span> west of the <span class="hlt">ice</span> divide in Greenland reached a maximum of 74 ± 25 Gt in 2012, when compared to the 1958–1999 average of 13 ± 2 Gt, while the percolation zone area more than doubled between 2003 and 2012. Increased melt and column densification resulted in surface lowering averaging -0.80 ± 0.39 m yr -1 between 1800 and 2800 m in the accumulation zone of western Greenland. Since 2007, modeled annual melt and refreezing rates in the percolation zone at elevations below 2100 m surpass the annual snowfall from the previous year, implying that <span class="hlt">mass</span> gain in the region is retained after melt in the form of refrozen meltwater. Furthermore, if current melt trends over high elevation regions continue, subsequent changes in firn structure will have implications for the hydrology of the <span class="hlt">ice</span> sheet and related abrupt seasonal densification could become increasingly significant for altimetry-derived <span class="hlt">ice</span> sheet <span class="hlt">mass</span> <span class="hlt">balance</span> estimates.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.1023C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.1023C"><span>A New Attempt of 2-D Numerical <span class="hlt">Ice</span> Flow Model to Reconstruct Paleoclimate from Mountain Glaciers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Candaş, Adem; Akif Sarıkaya, Mehmet</p> <p>2017-04-01</p> <p>A new two dimensional (2D) numerical <span class="hlt">ice</span> flow model is generated to simulate the steady-state glacier extent for a wide range of climate conditions. The simulation includes the flow of <span class="hlt">ice</span> enforced by the annual <span class="hlt">mass</span> <span class="hlt">balance</span> gradient of a valley glacier. The annual <span class="hlt">mass</span> <span class="hlt">balance</span> is calculated by the difference of the net accumulation and ablation of snow and (or) <span class="hlt">ice</span>. The generated model lets users to compare the simulated and field observed <span class="hlt">ice</span> extent of paleoglaciers. As a result, model results provide the conditions about the past climates since simulated <span class="hlt">ice</span> extent is a function of predefined climatic conditions. To predict the glacier shape and distribution in two dimension, time dependent partial differential equation (PDE) is solved. Thus, a 2D glacier flow model code is constructed in MATLAB and a finite difference method is used to solve this equation. On the other hand, Parallel <span class="hlt">Ice</span> Sheet Model (PISM) is used to regenerate paleoglaciers in the same area where the MATLAB code is applied. We chose the Mount Dedegöl, an extensively glaciated mountain in SW Turkey, to apply both models. Model results will be presented and discussed in this presentation. This study was supported by TÜBİTAK 114Y548 project.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.G21B0875K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.G21B0875K"><span>Exploring the effect of East Antarctic <span class="hlt">ice</span> <span class="hlt">mass</span> loss on GIA-induced horizontal bedrock motions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Konfal, S. A.; Whitehouse, P. L.; Hermans, T.; van der Wal, W.; Wilson, T. J.; Bevis, M. G.; Kendrick, E. C.; Dalziel, I.; Smalley, R., Jr.</p> <p>2017-12-01</p> <p><span class="hlt">Ice</span> history inputs used in Antarctic models of GIA include major centers of <span class="hlt">ice</span> <span class="hlt">mass</span> loss in West Antarctica. In the Transantarctic Mountains (TAM) region spanning the boundary between East and West Antarctica, horizontal crustal motions derived from GPS observations from the Antarctic Network (ANET) component of the Polar Earth Observing Network (POLENET) are towards these West Antarctic <span class="hlt">ice</span> <span class="hlt">mass</span> centers, opposite to the pattern of radial crustal motion expected in an unloading scenario. We investigate alternative <span class="hlt">ice</span> history and earth structure inputs to GIA models in an attempt to reproduce observed crustal motions in the region. The W12 <span class="hlt">ice</span> history model is altered to create scenarios including <span class="hlt">ice</span> unloading in the Wilkes Subglacial Basin based on available glaciological records. These altered <span class="hlt">ice</span> history models, along with the unmodified W12 <span class="hlt">ice</span> history model, are coupled with 60 radially varying (1D) earth model combinations, including approximations of optimal earth profiles identified in published GIA models. The resulting model-predicted motions utilizing both the modified and unmodified <span class="hlt">ice</span> history models fit ANET GPS-derived crustal motions in the northern TAM region for a suite of earth model combinations. Further south, where the influence of simulated Wilkes unloading is weakest and West Antarctic unloading is strongest, observed and predicted motions do not agree. The influence of simulated Wilkes <span class="hlt">ice</span> unloading coupled with laterally heterogeneous earth models is also investigated. The resulting model-predicted motions do not differ significantly between the original W12 and W12 with simulated Wilkes unloading <span class="hlt">ice</span> histories.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C51G..07M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C51G..07M"><span>Forecasting Glacier Evolution and Hindcasting Paleoclimates In Light of <span class="hlt">Mass</span> <span class="hlt">Balance</span> Nonlinearities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Malone, A.; Doughty, A. M.; MacAyeal, D. R.</p> <p>2016-12-01</p> <p>Glaciers are commonly used barometers of present and past climate change, with their variations often being linked to shifts in the mean climate. Climate variability within a unchanging mean state, however, can produce short term <span class="hlt">mass</span> <span class="hlt">balance</span> and glacier length anomalies, complicating this linkage. Also, the <span class="hlt">mass</span> <span class="hlt">balance</span> response to this variability can be nonlinear, possibly impacting the longer term state of the glacier. We propose a conceptual model to understand these nonlinearities and quantify their impacts on the longer term <span class="hlt">mass</span> <span class="hlt">balance</span> and glacier length. The relationship between <span class="hlt">mass</span> <span class="hlt">balance</span> and elevation, i.e. the vertical <span class="hlt">balance</span> profile (VBP), illuminates these nonlinearities (Figure A). The VBP, given here for a wet tropical glacier, is piecewise, which can lead to different <span class="hlt">mass</span> <span class="hlt">balance</span> responses to climate anomalies of similar magnitude but opposite sign. We simulate the <span class="hlt">mass</span> <span class="hlt">balance</span> response to climate variability by vertically (temperature anomalies) and horizontally (precipitation anomalies) transposing the VBP for the mean climate (Figure A). The resulting anomalous VBP is the superposition of the two translations. We drive a 1-D flowline model with 10,000 years of anomalous VBPs. The aggregate VBP for the mean climate including variability differs from the VBP for the mean climate excluding variability, having a higher equilibrium line altitude (ELA) and a negative <span class="hlt">mass</span> <span class="hlt">balance</span> (Figure B). Accordingly, the glacier retreats, and the equilibrium glacier length for the aggregate VBP is the same as the mean length from the 10,000 year flowline simulation (Figure C). The magnitude of the VBP shift and glacier retreat increases with greater temperature variability and larger discontinuities in the VBP slope. These results highlight the importance of both the climate mean and variability in determining the longer term state of the glacier. Thus, forecasting glacier evolution or hindcasting past climates should also include representation of climate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27679819','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27679819"><span>Geodetic measurements reveal similarities between post-Last Glacial Maximum and present-day <span class="hlt">mass</span> loss from the Greenland <span class="hlt">ice</span> sheet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Khan, Shfaqat A; Sasgen, Ingo; Bevis, Michael; van Dam, Tonie; Bamber, Jonathan L; Wahr, John; Willis, Michael; Kjær, Kurt H; Wouters, Bert; Helm, Veit; Csatho, Beata; Fleming, Kevin; Bjørk, Anders A; Aschwanden, Andy; Knudsen, Per; Munneke, Peter Kuipers</p> <p>2016-09-01</p> <p>Accurate quantification of the millennial-scale <span class="hlt">mass</span> <span class="hlt">balance</span> of the Greenland <span class="hlt">ice</span> sheet (GrIS) and its contribution to global sea-level rise remain challenging because of sparse in situ observations in key regions. Glacial isostatic adjustment (GIA) is the ongoing response of the solid Earth to <span class="hlt">ice</span> and ocean load changes occurring since the Last Glacial Maximum (LGM; ~21 thousand years ago) and may be used to constrain the GrIS deglaciation history. We use data from the Greenland Global Positioning System network to directly measure GIA and estimate basin-wide <span class="hlt">mass</span> changes since the LGM. Unpredicted, large GIA uplift rates of +12 mm/year are found in southeast Greenland. These rates are due to low upper mantle viscosity in the region, from when Greenland passed over the Iceland hot spot about 40 million years ago. This region of concentrated soft rheology has a profound influence on reconstructing the deglaciation history of Greenland. We reevaluate the evolution of the GrIS since LGM and obtain a loss of 1.5-m sea-level equivalent from the northwest and southeast. These same sectors are dominating modern <span class="hlt">mass</span> loss. We suggest that the present destabilization of these marine-based sectors may increase sea level for centuries to come. Our new deglaciation history and GIA uplift estimates suggest that studies that use the Gravity Recovery and Climate Experiment satellite mission to infer present-day changes in the GrIS may have erroneously corrected for GIA and underestimated the <span class="hlt">mass</span> loss by about 20 gigatons/year.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5031466','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5031466"><span>Geodetic measurements reveal similarities between post–Last Glacial Maximum and present-day <span class="hlt">mass</span> loss from the Greenland <span class="hlt">ice</span> sheet</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Khan, Shfaqat A.; Sasgen, Ingo; Bevis, Michael; van Dam, Tonie; Bamber, Jonathan L.; Wahr, John; Willis, Michael; Kjær, Kurt H.; Wouters, Bert; Helm, Veit; Csatho, Beata; Fleming, Kevin; Bjørk, Anders A.; Aschwanden, Andy; Knudsen, Per; Munneke, Peter Kuipers</p> <p>2016-01-01</p> <p>Accurate quantification of the millennial-scale <span class="hlt">mass</span> <span class="hlt">balance</span> of the Greenland <span class="hlt">ice</span> sheet (GrIS) and its contribution to global sea-level rise remain challenging because of sparse in situ observations in key regions. Glacial isostatic adjustment (GIA) is the ongoing response of the solid Earth to <span class="hlt">ice</span> and ocean load changes occurring since the Last Glacial Maximum (LGM; ~21 thousand years ago) and may be used to constrain the GrIS deglaciation history. We use data from the Greenland Global Positioning System network to directly measure GIA and estimate basin-wide <span class="hlt">mass</span> changes since the LGM. Unpredicted, large GIA uplift rates of +12 mm/year are found in southeast Greenland. These rates are due to low upper mantle viscosity in the region, from when Greenland passed over the Iceland hot spot about 40 million years ago. This region of concentrated soft rheology has a profound influence on reconstructing the deglaciation history of Greenland. We reevaluate the evolution of the GrIS since LGM and obtain a loss of 1.5-m sea-level equivalent from the northwest and southeast. These same sectors are dominating modern <span class="hlt">mass</span> loss. We suggest that the present destabilization of these marine-based sectors may increase sea level for centuries to come. Our new deglaciation history and GIA uplift estimates suggest that studies that use the Gravity Recovery and Climate Experiment satellite mission to infer present-day changes in the GrIS may have erroneously corrected for GIA and underestimated the <span class="hlt">mass</span> loss by about 20 gigatons/year. PMID:27679819</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70074767','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70074767"><span>Climatic impact of glacial cycle polar motion: Coupled oscillations of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> and rotation pole position</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bills, Bruce G.; James, Thomas S.; Mengel, John G.</p> <p>1999-01-01</p> <p>Precessional motion of Earth's rotation axis relative to its orbit is a well-known source of long-period climatic variation. It is less well appreciated that growth and decay of polar <span class="hlt">ice</span> sheets perturb the symmetry of the global <span class="hlt">mass</span> distribution enough that the geographic location of the rotation axis will change by at least 15 km and possibly as much as 100 km during a single glacial cycle. This motion of the pole will change the seasonal and latitudinal pattern of temperatures. We present calculations, based on a diurnal average energy <span class="hlt">balance</span>, which compare the summer and winter temperature anomalies due to a 1° decrease in obliquity with those due to a 1° motion of the rotation pole toward Hudson Bay. Both effects result in peak temperature perturbations of about 1° Celsius. The obliquity change primarily influences the amplitude of the seasonal cycle, while the polar motion primarily changes the annual mean temperatures. The polar motion induced temperature anomaly is such that it will act as a powerful negative feedback on <span class="hlt">ice</span> sheet growth. We also explore the evolution of the coupled system composed of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> and pole position. Oscillatory solutions result from the conflicting constraints of rotational and thermal stability. A positive <span class="hlt">mass</span> anomaly on an otherwise featureless Earth is in rotational equilibrium only at the poles or the equator. The two polar equilibria are rotationally unstable, and the equatorial equilibrium, though rotationally stable, is thermally unstable. We find that with a plausible choice for the strength of coupling between the thermal and rotational systems, relatively modest external forcing can produce significant response at periods of 104–106 years, but it strongly attenuates polar motion at longer periods. We suggest that these coupled oscillations may contribute to the observed dominance of 100 kyr glacial cycles since the mid-Pleistocene and will tend to stabilize geographic patterns that are suitable to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014TCD.....8.5227I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014TCD.....8.5227I"><span>The melt pond fraction and spectral sea <span class="hlt">ice</span> albedo retrieval from MERIS data: validation and trends of sea <span class="hlt">ice</span> albedo and melt pond fraction in the Arctic for years 2002-2011</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Istomina, L.; Heygster, G.; Huntemann, M.; Schwarz, P.; Birnbaum, G.; Scharien, R.; Polashenski, C.; Perovich, D.; Zege, E.; Malinka, A.; Prikhach, A.; Katsev, I.</p> <p>2014-10-01</p> <p>The presence of melt ponds on the Arctic sea <span class="hlt">ice</span> strongly affects the energy <span class="hlt">balance</span> of the Arctic Ocean in summer. It affects albedo as well as transmittance through the sea <span class="hlt">ice</span>, which has consequences on the heat <span class="hlt">balance</span> and <span class="hlt">mass</span> <span class="hlt">balance</span> of sea <span class="hlt">ice</span>. An algorithm to retrieve melt pond fraction and sea <span class="hlt">ice</span> albedo (Zege et al., 2014) from the MEdium Resolution Imaging Spectrometer (MERIS) data is validated against aerial, ship borne and in situ campaign data. The result show the best correlation for landfast and multiyear <span class="hlt">ice</span> of high <span class="hlt">ice</span> concentrations (albedo: R = 0.92, RMS = 0.068, melt pond fraction: R = 0.6, RMS = 0.065). The correlation for lower <span class="hlt">ice</span> concentrations, subpixel <span class="hlt">ice</span> floes, blue <span class="hlt">ice</span> and wet <span class="hlt">ice</span> is lower due to complicated surface conditions and <span class="hlt">ice</span> drift. Combining all aerial observations gives a mean albedo RMS equal to 0.089 and a mean melt pond fraction RMS equal to 0.22. The in situ melt pond fraction correlation is R = 0.72 with an RMS = 0.14. Ship cruise data might be affected by documentation of varying accuracy within the ASPeCT protocol, which is the reason for discrepancy between the satellite value and observed value: mean R = 0.21, mean RMS = 0.16. An additional dynamic spatial cloud filter for MERIS over snow and <span class="hlt">ice</span> has been developed to assist with the validation on swath data. The case studies and trend analysis for the whole MERIS period (2002-2011) show pronounced and reasonable spatial features of melt pond fractions and sea <span class="hlt">ice</span> albedo. The most prominent feature is the melt onset shifting towards spring (starting already in weeks 3 and 4 of June) within the multiyear <span class="hlt">ice</span> area, north to the Queen Elizabeth Islands and North Greenland.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011TCry....5..727M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011TCry....5..727M"><span>The Potsdam Parallel <span class="hlt">Ice</span> Sheet Model (PISM-PIK) - Part 2: Dynamic equilibrium simulation of the Antarctic <span class="hlt">ice</span> sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martin, M. A.; Winkelmann, R.; Haseloff, M.; Albrecht, T.; Bueler, E.; Khroulev, C.; Levermann, A.</p> <p>2011-09-01</p> <p>We present a dynamic equilibrium simulation of the <span class="hlt">ice</span> sheet-shelf system on Antarctica with the Potsdam Parallel <span class="hlt">Ice</span> Sheet Model (PISM-PIK). The simulation is initialized with present-day conditions for bed topography and <span class="hlt">ice</span> thickness and then run to steady state with constant present-day surface <span class="hlt">mass</span> <span class="hlt">balance</span>. Surface temperature and sub-shelf basal melt distribution are parameterized. Grounding lines and calving fronts are free to evolve, and their modeled equilibrium state is compared to observational data. A physically-motivated calving law based on horizontal spreading rates allows for realistic calving fronts for various types of shelves. Steady-state dynamics including surface velocity and <span class="hlt">ice</span> flux are analyzed for whole Antarctica and the Ronne-Filchner and Ross <span class="hlt">ice</span> shelf areas in particular. The results show that the different flow regimes in sheet and shelves, and the transition zone between them, are captured reasonably well, supporting the approach of superposition of SIA and SSA for the representation of fast motion of grounded <span class="hlt">ice</span>. This approach also leads to a natural emergence of sliding-dominated flow in stream-like features in this new 3-D marine <span class="hlt">ice</span> sheet model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1912149V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1912149V"><span>Long-term evolution of a small <span class="hlt">ice</span> cap in Greenland: a dynamic perspective from numerical flow modelling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vieli, Andreas; Lane, Timothy; Adamson, Kathryn</p> <p>2017-04-01</p> <p>Small <span class="hlt">ice</span> caps at the periphery of the Greenland <span class="hlt">ice</span> sheet are often close to the limit of existence and are therefore expected to respond more sensitively to climate change than the land-margin of the neighboring <span class="hlt">ice</span> sheet. However, their past evolution and dynamic behavior is poorly understood and their use as climate indicators therefore remains so far limited. We here aim to provide a long-term dynamic reconstruction of Lyngmarksbraeen, a small (32km2) <span class="hlt">ice</span> cap on Disko Island in West Greenland, with a particular focus on the little <span class="hlt">ice</span> age (LIA, since 1200AD). We use a 2-dim. time-dependent numerical flow model (SIA) and a PDD-<span class="hlt">mass</span> <span class="hlt">balance</span> model in combination with historical observations, geomorphological mapping and exposure dating to simulate its long-term evolution and dynamic behaviour. We specifically focus on retreat since the LIA, which is well constrained by geomorphological evidence and historical maps and length records of several small outlet glaciers and data from local and regional climate stations (Qeqertarssuaq and Ilulisat). We also explore aspects related to flow dynamics and find that the dynamic state of this <span class="hlt">ice</span> cap is, at any time, far from being <span class="hlt">balanced</span> and is highly sensitive to the surface elevation <span class="hlt">mass</span> <span class="hlt">balance</span> feedback and results in an asynchronous response of the different outlets and hysteresis-type behaviour. The modelling is able to reproduce the observed LIA-extent and the almost continuous retreat over the last hundred years well. It further indicates that the <span class="hlt">ice</span> cap was already dynamically inert since the 1960s. Today, the <span class="hlt">ice</span> cap has lost almost its entire accumulation area and even without any further warming in the future, the <span class="hlt">ice</span> cap is expected to vanish within a couple of decades.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11.1665S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11.1665S"><span>The importance of accurate glacier albedo for estimates of surface <span class="hlt">mass</span> <span class="hlt">balance</span> on Vatnajökull: evaluating the surface energy budget in a regional climate model with automatic weather station observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steffensen Schmidt, Louise; Aðalgeirsdóttir, Guðfinna; Guðmundsson, Sverrir; Langen, Peter L.; Pálsson, Finnur; Mottram, Ruth; Gascoin, Simon; Björnsson, Helgi</p> <p>2017-07-01</p> <p>A simulation of the surface climate of Vatnajökull <span class="hlt">ice</span> cap, Iceland, carried out with the regional climate model HIRHAM5 for the period 1980-2014, is used to estimate the evolution of the glacier surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB). This simulation uses a new snow albedo parameterization that allows albedo to exponentially decay with time and is surface temperature dependent. The albedo scheme utilizes a new background map of the <span class="hlt">ice</span> albedo created from observed MODIS data. The simulation is evaluated against observed daily values of weather parameters from five automatic weather stations (AWSs) from the period 2001-2014, as well as in situ SMB measurements from the period 1995-2014. The model agrees well with observations at the AWS sites, albeit with a general underestimation of the net radiation. This is due to an underestimation of the incoming radiation and a general overestimation of the albedo. The average modelled albedo is overestimated in the ablation zone, which we attribute to an overestimation of the thickness of the snow layer and not taking the surface darkening from dirt and volcanic ash deposition during dust storms and volcanic eruptions into account. A comparison with the specific summer, winter, and net <span class="hlt">mass</span> <span class="hlt">balance</span> for the whole of Vatnajökull (1995-2014) shows a good overall fit during the summer, with a small <span class="hlt">mass</span> <span class="hlt">balance</span> underestimation of 0.04 m w.e. on average, whereas the winter <span class="hlt">mass</span> <span class="hlt">balance</span> is overestimated by on average 0.5 m w.e. due to too large precipitation at the highest areas of the <span class="hlt">ice</span> cap. A simple correction of the accumulation at the highest points of the glacier reduces this to 0.15 m w.e. Here, we use HIRHAM5 to simulate the evolution of the SMB of Vatnajökull for the period 1981-2014 and show that the model provides a reasonable representation of the SMB for this period. However, a major source of uncertainty in the representation of the SMB is the representation of the albedo, and processes currently not accounted for in RCMs</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC53E0941S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC53E0941S"><span>Advancing land-terminating <span class="hlt">ice</span> margin in North Greenland - characteristics, evolution, and first field measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steiner, J. F.; Prinz, R.; Abermann, J.</p> <p>2017-12-01</p> <p>More than 40% of the <span class="hlt">ice</span> sheet in North Greenland terminate on land, however the characteristics of this <span class="hlt">ice</span> margin and response to a changing climate have so far received little attention. While land-terminating <span class="hlt">ice</span> cliffs are a feature commonly found and studied in other regions, detailed investigations in Greenland were only carried out more than six decades ago in the Thule area (Red Rock, Northwest Greenland). These studies showed a continuous advance at one location over multiple years, while the local <span class="hlt">mass</span> <span class="hlt">balance</span> was reported negative. The purpose of our study is to revisit the location previously studied and extend the analysis to the complete Northern <span class="hlt">ice</span> margin employing newly available high-resolution digital terrain models (Arctic DEM). First results show that the advance at Red Rock is indeed long-term, continuing unabated today at rates of up to several meter per year. Similar magnitudes were found for large other stretches along the <span class="hlt">ice</span> margin. With our study we aim to show (a) the main characteristics of the land-terminating <span class="hlt">ice</span> margin in Northern Greenland, namely its slope and aspect distribution and comparison to spatial datasets of flow velocity and <span class="hlt">mass</span> <span class="hlt">balance</span> and (b) to provide further explanations of physical processes driving the advance. We have therefore mapped the complete <span class="hlt">ice</span> margin and present the first results of this analysis. First field work provides new data on energy fluxes and <span class="hlt">ice</span> temperatures at the Red Rock site as well as high resolution DEMs obtained with the use of UAVs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930037350&hterms=rate+sensitivity+ice&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Drate%2Bsensitivity%2Bice','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930037350&hterms=rate+sensitivity+ice&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Drate%2Bsensitivity%2Bice"><span>Ocean interactions with the base of Amery <span class="hlt">Ice</span> Shelf, Antarctica</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hellmer, Hartmut H.; Jacobs, Stanley S.</p> <p>1992-01-01</p> <p>Using a two-dimensional ocean themohaline circulation model, we varied the cavity shape beneath Amery <span class="hlt">Ice</span> Shelf in an attempt to reproduce the 150-m-thick marine <span class="hlt">ice</span> layer observed at the 'G1' <span class="hlt">ice</span> core site. Most simulations caused melting rates which decrease the <span class="hlt">ice</span> thickness by as much as 400 m between grounding line and G1, but produce only minor accumulation at the <span class="hlt">ice</span> core site and closer to the <span class="hlt">ice</span> front. Changes in the sea floor and <span class="hlt">ice</span> topographies revealed a high sensitivity of the basal <span class="hlt">mass</span> <span class="hlt">balance</span> to water column thickness near the grounding line, to submarine sills, and to discontinuities in <span class="hlt">ice</span> thickness. Model results showed temperature/salinity gradients similar to observations from beneath other <span class="hlt">ice</span> shelves where <span class="hlt">ice</span> is melting into seawater. Modeled outflow characteristics at the <span class="hlt">ice</span> front are in general agreement with oceanographic data from Prydz Bay. We concur with Morgan's inference that the G1 core may have been taken in a basal crevasse filled with marine <span class="hlt">ice</span>. This <span class="hlt">ice</span> is formed from water cooled by ocean/<span class="hlt">ice</span> shelf interactions along the interior <span class="hlt">ice</span> shelf base.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP21D..04F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP21D..04F"><span><span class="hlt">Mass</span> <span class="hlt">balance</span> approaches to understanding evolution of dripwater chemistry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fairchild, I. J.; Baker, A.; Andersen, M. S.; Treble, P. C.</p> <p>2015-12-01</p> <p>Forward and inverse modelling of dripwater chemistry is a fast-developing area in speleothem science. Such approaches can incorporate theoretical, parameterized or observed relationships between forcing factors and water composition, but at the heart is <span class="hlt">mass</span> <span class="hlt">balance</span>: a fundamental principle that provides important constraints. <span class="hlt">Mass</span> <span class="hlt">balance</span> has been used in speleothem studies to trace the evolution of dissolved inorganic carbon and carbon isotopes from soil to cave, and to characterize the existence and quantification of prior calcite precipitation (PCP) based on ratios of Mg and Sr to Ca. PCP effects can dominate slow drips, whereas fast drips are more likely to show a residual variability linked to soil-biomass processes. A possible configuration of a more complete <span class="hlt">mass</span> <span class="hlt">balance</span> model is illustrated in the figure. Even in humid temperate climates, evapotranspiration can be 50% of total atmospheric precipitation leading to substantially raised salt contents and there can be significant exchange with biomass. In more arid settings, at least seasonal soil storage of salts is likely. Golgotha Cave in SW Australia is in a Mediterranean climate with a strong summer soil moisture deficit. The land surface is forested leading to large ion fluxes related to vegetation. There are also periodic disturbances related to fire. <span class="hlt">Mass</span> <span class="hlt">balance</span> approaches have been applied to an 8-year monitoring record. Inter-annual trends of elements coprecipitated in speleothems from fast drips are predicted to be dominated by biomass effects.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.5339F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.5339F"><span>Assessing the accuracy of Greenland <span class="hlt">ice</span> sheet <span class="hlt">ice</span> ablation measurements by pressure transducer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fausto, R. S.; van As, D.; Ahlstrøm, A. P.</p> <p>2012-04-01</p> <p>In the glaciological community there is a need for reliable <span class="hlt">mass</span> <span class="hlt">balance</span> measurements of glaciers and <span class="hlt">ice</span> sheets, ranging from daily to yearly time scales. Here we present a method to measure <span class="hlt">ice</span> ablation using a pressure transducer. The pressure transducer is drilled into the <span class="hlt">ice</span>, en-closed in a hose filled with a liquid that is non-freezable at common Greenlandic temperatures. The pressure signal registered by the transducer is that of the vertical column of liquid over the sensor, which can be translated in depth knowing the density of the liquid. As the free-standing AWS moves down with the ablating surface and the hose melts out of the <span class="hlt">ice</span>, an increasingly large part of the hose will lay flat on the <span class="hlt">ice</span> surface, and the hydrostatic pressure from the vertical column of liquid in the hose will get smaller. This reduction in pressure provides us with the ablation rate. By measuring at (sub-) daily timescales this assembly is well-suited to monitor <span class="hlt">ice</span> ablation in remote regions, with clear advantages over other well-established methods of measuring <span class="hlt">ice</span> ablation in the field. The pressure transducer system has the potential to monitor <span class="hlt">ice</span> ablation for several years without re-drilling and the system is suitable for high ablation areas. A routine to transform raw measurements into ablation values will also be presented, including a physically based method to remove air pressure variability from the signal. The pressure transducer time-series is compared to that recorded by a sonic ranger for the climatically hostile setting on the Greenland <span class="hlt">ice</span> sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EPSC...11.1010K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EPSC...11.1010K"><span>Reproducing impact ionization <span class="hlt">mass</span> spectra of E and F ring <span class="hlt">ice</span> grains at different impact speeds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klenner, F.; Reviol, R.; Postberg, F.</p> <p>2017-09-01</p> <p>As impact speeds of E and F ring <span class="hlt">ice</span> grains impinging onto the target of impact ionization <span class="hlt">mass</span> spectrometers in space can vary greatly, the resulting cationic or anionic <span class="hlt">mass</span> spectra can have very different appearances. The <span class="hlt">mass</span> spectra can be accurately reproduced with an analog experimental setup IR-FL-MALDI-ToF-MS (Infrared Free Liquid Matrix Assisted Laser Desorption and Ionization Time of Flight <span class="hlt">Mass</span> Spectrometry). We compare <span class="hlt">mass</span> spectra of E and F ring <span class="hlt">ice</span> grains taken by the Cosmic Dust Analyzer (CDA) onboard Cassini recorded at different impact speeds with our analog spectra and prove the capability of the analog experiment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT.........6T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT.........6T"><span>A multi-decadal remote sensing study on glacial change in the North Patagonia <span class="hlt">Ice</span> Field Chile</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tetteh, Lucy Korlekwor</p> <p></p> <p>Glaciers in the North Patagonian <span class="hlt">Ice</span> Fields are temperate glaciers and can be studied to understand the dynamics of climate change. However, the <span class="hlt">ice</span> field has been neglected in <span class="hlt">mass</span> <span class="hlt">balance</span> studies. In this study, multi decadal study of glacial <span class="hlt">mass</span> <span class="hlt">balance</span>, glacier retreat and glacial lake expansion in the North Patagonia were studied. Landsat (TM, ETM+ and 8) and ASTER images were used. San Quintin glacier experienced the highest retreat. Demarcation of glacier lakes boundaries indicated an increase in glacial lake area an addition of 4 new glacial lakes. Nef glacier recorded the highest <span class="hlt">mass</span> gain of 9.91 plus or minus 1.96 m.w.e.a.-1 and HPN-4 glacier recorded the highest <span class="hlt">mass</span> loss of -8.9 plus or minus 1.96 m.w.e.a. -1. However, there is a high uncertainty in the elevation values in the DEM due to the rugged nature of the terrain and presence of the heavy snow cover.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12..833K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12..833K"><span>Geodetic reanalysis of annual glaciological <span class="hlt">mass</span> <span class="hlt">balances</span> (2001-2011) of Hintereisferner, Austria</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klug, Christoph; Bollmann, Erik; Galos, Stephan Peter; Nicholson, Lindsey; Prinz, Rainer; Rieg, Lorenzo; Sailer, Rudolf; Stötter, Johann; Kaser, Georg</p> <p>2018-03-01</p> <p>This study presents a reanalysis of the glaciologically obtained annual glacier <span class="hlt">mass</span> <span class="hlt">balances</span> at Hintereisferner, Ötztal Alps, Austria, for the period 2001-2011. The reanalysis is accomplished through a comparison with geodetically derived <span class="hlt">mass</span> changes, using annual high-resolution airborne laser scanning (ALS). The grid-based adjustments for the method-inherent differences are discussed along with associated uncertainties and discrepancies of the two methods of <span class="hlt">mass</span> <span class="hlt">balance</span> measurements. A statistical comparison of the two datasets shows no significant difference for seven annual, as well as the cumulative, <span class="hlt">mass</span> changes over the 10-year record. Yet, the statistical view hides significant differences in the <span class="hlt">mass</span> <span class="hlt">balance</span> years 2002/03 (glaciological minus geodetic records = +0.92 m w.e.), 2005/06 (+0.60 m w.e.), and 2006/07 (-0.45 m w.e.). We conclude that exceptional meteorological conditions can render the usual glaciological observational network inadequate. Furthermore, we consider that ALS data reliably reproduce the annual <span class="hlt">mass</span> <span class="hlt">balance</span> and can be seen as validation or calibration tools for the glaciological method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910017261','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910017261"><span>Sea-level response to <span class="hlt">ice</span> sheet evolution: An ocean perspective</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jacobs, Stanley S.</p> <p>1991-01-01</p> <p>The ocean's influence upon and response to Antarctic <span class="hlt">ice</span> sheet changes is considered in relation to sea level rise over recent and future decades. Assuming present day <span class="hlt">ice</span> fronts are in approximate equilibrium, a preliminary budget for the <span class="hlt">ice</span> sheet is estimated from accumulation vs. iceberg calving and the basal melting that occurs beneath floating <span class="hlt">ice</span> shelves. Iceberg calving is derived from the volume of large bergs identified and tracked by the Navy/NOAA Joint <span class="hlt">Ice</span> Center and from shipboard observations. Basal melting exceeds 600 cu km/yr and is concentrated near the <span class="hlt">ice</span> fronts and <span class="hlt">ice</span> shelf grounding lines. An apparent negative <span class="hlt">mass</span> <span class="hlt">balance</span> for the Antarctic <span class="hlt">ice</span> sheet may result from an anomalous calving rate during the past decade, but there are large uncertainties associated with all components of the <span class="hlt">ice</span> budget. The results from general circulation models are noted in the context of projected precipitation increases and ocean temperature changes on and near the continent. An ocean research program that could help refine budget estimates is consistent with goals of the West Antarctic <span class="hlt">Ice</span> Sheet Initiative.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C51E..03M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C51E..03M"><span><span class="hlt">Ice</span> shelf snow accumulation rates from the Amundsen-Bellingshausen Sea sector of West Antarctica derived from airborne radar</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Medley, B.; Kurtz, N. T.; Brunt, K. M.</p> <p>2015-12-01</p> <p>The large <span class="hlt">ice</span> shelves surrounding the Antarctic continent buttress inland <span class="hlt">ice</span>, limiting the grounded <span class="hlt">ice</span>-sheet flow. Many, but not all, of the thick <span class="hlt">ice</span> shelves located along the Amundsen-Bellingshausen Seas are experiencing rapid thinning due to enhanced basal melting driven by the intrusion of warm circumpolar deep water. Determination of their <span class="hlt">mass</span> <span class="hlt">balance</span> provides an indicator as to the future of the shelves buttressing capability; however, measurements of surface accumulation are few, limiting the precision of the <span class="hlt">mass</span> <span class="hlt">balance</span> estimates. Here, we present new radar-derived measurements of snow accumulation primarily over the Getz and Abbott <span class="hlt">Ice</span> Shelves, as well as the Dotson and Crosson, which have been the focus of several of NASA's Operation <span class="hlt">Ice</span>Bridge airborne surveys between 2009 and 2014. Specifically, we use the Center for Remote Sensing of <span class="hlt">Ice</span> Sheets (CReSIS) snow radar to map the near-surface (< 30 m) internal stratigraphy to measure snow accumulation. Due to the complexities of the local topography (e.g., <span class="hlt">ice</span> rises and rumples) and their relative proximity to the ocean, the spatial pattern of accumulation can be equally varied. Therefore, atmospheric models might not be able to reproduce these small-scale features because of their limited spatial resolution. To evaluate whether this is the case over these narrow shelves, we will compare the radar-derived accumulation rates with those from atmospheric models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.6301L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.6301L"><span>Comparative glacio-climatological analysis of <span class="hlt">mass</span> <span class="hlt">balance</span> variability along the geographical margin of Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lehoczky, Annamária; Kern, Zoltán; Pongrácz, Rita</p> <p>2014-05-01</p> <p>Glacio-climatological studies recognise glacier <span class="hlt">mass</span> <span class="hlt">balance</span> changes as high-confident climate indicators. The climatic sensitivity of a glacier does not simply depend on regional climate variability but also influenced via large- and mesoscale atmospheric circulation patterns. This study focuses on recent changes in the <span class="hlt">mass</span> <span class="hlt">balance</span> using records from three border regions of Europe, and investigates the relationships between the seasonal <span class="hlt">mass</span> <span class="hlt">balance</span> components, regional climatic conditions, and distant atmospheric forcing. Since glaciers in different macro-climatological conditions (i.e., mid-latitudes or high-latitudes, dry-continental or maritime regions) may present strongly diverse <span class="hlt">mass</span> <span class="hlt">balance</span> characteristics, the three analysed regions were selected from different glacierised macroregions (using the database of the World Glacier Monitoring Service). These regions belong to the Caucasus Mountains (Central Europe macroregion), the Polar Ural (Northern Asia macroregion), and Svalbard (Arctic Islands macroregion). The analysis focuses on winter, summer, and annual <span class="hlt">mass</span> <span class="hlt">balance</span> series of eight glaciers. The climatic variables (atmospheric pressure, air temperature, precipitation) and indices of teleconnection patterns (e.g., North Atlantic Oscillation, Pacific Decadal Oscillation) are used from the gridded databases of the University of East Anglia, Climatic Research Unit and the National Oceanic and Atmospheric Administration, National Center for Environmental Prediction. However, the period and length of available <span class="hlt">mass</span> <span class="hlt">balance</span> data in the selected regions vary greatly (the first full record is in 1958, Polar Ural; the last is in 2010, Caucasus Mountains), a comparative analysis can be carried out for the period of 1968-1981. Since glaciers from different regions respond to large- and mesoscale climatic forcings differently, and because the <span class="hlt">mass</span> <span class="hlt">balance</span> of glaciers within a region often co-vary, our specific objectives are (i) to examine the variability and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.C31B0314L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.C31B0314L"><span>West Antarctic <span class="hlt">Balance</span> Fluxes: Impact of Smoothing, Algorithm and Topography.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Le Brocq, A.; Payne, A. J.; Siegert, M. J.; Bamber, J. L.</p> <p>2004-12-01</p> <p>Grid-based calculations of <span class="hlt">balance</span> flux and velocity have been widely used to understand the large-scale dynamics of <span class="hlt">ice</span> <span class="hlt">masses</span> and as indicators of their state of <span class="hlt">balance</span>. This research investigates a number of issues relating to their calculation for the West Antarctic <span class="hlt">Ice</span> Sheet (see below for further details): 1) different topography smoothing techniques; 2) different grid based flow-apportioning algorithms; 3) the source of the flow direction, whether from smoothed topography, or smoothed gravitational driving stress; 4) different flux routing techniques and 5) the impact of different topographic datasets. The different algorithms described below lead to significant differences in both <span class="hlt">ice</span> stream margins and values of fluxes within them. This encourages caution in the use of grid-based <span class="hlt">balance</span> flux/velocity distributions and values, especially when considering the state of <span class="hlt">balance</span> of individual <span class="hlt">ice</span> streams. 1) Most previous calculations have used the same numerical scheme (Budd and Warner, 1996) applied to a smoothed topography in order to incorporate the longitudinal stresses that smooth <span class="hlt">ice</span> flow. There are two options to consider when smoothing the topography, the size of the averaging filter and the shape of the averaging function. However, this is not a physically-based approach to incorporating smoothed <span class="hlt">ice</span> flow and also introduces significant flow artefacts when using a variable weighting function. 2) Different algorithms to apportion flow are investigated; using 4 or 8 neighbours, and apportioning flow to all down-slope cells or only 2 (based on derived flow direction). 3) A theoretically more acceptable approach of incorporating smoothed <span class="hlt">ice</span> flow is to use the smoothed gravitational driving stress in x and y components to derive a flow direction. The flux can then be apportioned using the flow direction approach used above. 4) The original scheme (Budd and Warner, 1996) uses an elevation sort technique to calculate the <span class="hlt">balance</span> flux contribution from all</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4284527','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4284527"><span>Laser altimetry reveals complex pattern of Greenland <span class="hlt">Ice</span> Sheet dynamics</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Csatho, Beata M.; Schenk, Anton F.; van der Veen, Cornelis J.; Babonis, Gregory; Duncan, Kyle; Rezvanbehbahani, Soroush; van den Broeke, Michiel R.; Simonsen, Sebastian B.; Nagarajan, Sudhagar; van Angelen, Jan H.</p> <p>2014-01-01</p> <p>We present a new record of <span class="hlt">ice</span> thickness change, reconstructed at nearly 100,000 sites on the Greenland <span class="hlt">Ice</span> Sheet (GrIS) from laser altimetry measurements spanning the period 1993–2012, partitioned into changes due to surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) and <span class="hlt">ice</span> dynamics. We estimate a mean annual GrIS <span class="hlt">mass</span> loss of 243 ± 18 Gt⋅y−1, equivalent to 0.68 mm⋅y−1 sea level rise (SLR) for 2003–2009. Dynamic thinning contributed 48%, with the largest rates occurring in 2004–2006, followed by a gradual decrease <span class="hlt">balanced</span> by accelerating SMB loss. The spatial pattern of dynamic <span class="hlt">mass</span> loss changed over this time as dynamic thinning rapidly decreased in southeast Greenland but slowly increased in the southwest, north, and northeast regions. Most outlet glaciers have been thinning during the last two decades, interrupted by episodes of decreasing thinning or even thickening. Dynamics of the major outlet glaciers dominated the <span class="hlt">mass</span> loss from larger drainage basins, and simultaneous changes over distances up to 500 km are detected, indicating climate control. However, the intricate spatiotemporal pattern of dynamic thickness change suggests that, regardless of the forcing responsible for initial glacier acceleration and thinning, the response of individual glaciers is modulated by local conditions. Recent projections of dynamic contributions from the entire GrIS to SLR have been based on the extrapolation of four major outlet glaciers. Considering the observed complexity, we question how well these four glaciers represent all of Greenland’s outlet glaciers. PMID:25512537</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C53A0767E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C53A0767E"><span>The North Water Polynya and Velocity, Calving Front and <span class="hlt">Mass</span> Change in Surrounding Glaciers in Greenland and Canada Over the Last 30 Years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Edwards, L.</p> <p>2015-12-01</p> <p>Major uncertainties surround future estimates of sea level rise attributable to <span class="hlt">mass</span> loss from Greenland and the surrounding <span class="hlt">ice</span> caps in Canada. Understanding changes across these regions is vital as their glaciers have experienced dramatic changes in recent times. Attention has focused on the periphery of these regions where land <span class="hlt">ice</span> meets the ocean and where <span class="hlt">ice</span> acceleration, thinning and increased calving have been observed. Polynyas are areas of open water within sea <span class="hlt">ice</span> which remain unfrozen for much of the year. They vary significantly in size (~3 km2 to > ~85,000 km2 in the Arctic), recurrence rates and duration. Despite their relatively small size, polynyas strongly impact regional oceanography and play a vital role in heat and moisture exchange between the polar oceans and atmosphere. Where polynyas are present adjacent to tidewater glaciers their influence on ocean circulation and water temperatures has the potential to play a major part in controlling subsurface <span class="hlt">ice</span> melt rates by impacting on the water <span class="hlt">masses</span> reaching the calving front. They also have the potential to influence air <span class="hlt">masses</span> reaching nearby glaciers and <span class="hlt">ice</span> caps by creating a maritime climate which may impact on the glaciers' accumulation and surface melt and hence their thickness and <span class="hlt">mass</span> <span class="hlt">balance</span>. Polynya presence and size also have implications for sea <span class="hlt">ice</span> extent and therefore may influence the buttressing effect on neighbouring tidewater glaciers. The work presented uses remote sensing and <span class="hlt">mass</span> <span class="hlt">balance</span> model data to study changes in the North Water polynya (extent, <span class="hlt">ice</span> concentration, duration) and neighbouring glaciers and <span class="hlt">ice</span> caps (velocities, calving front positions and <span class="hlt">mass</span> <span class="hlt">balance</span>) in Canada and Greenland over a period of approximately 30 years from the mid-1980s through to 2015.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11.1553S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11.1553S"><span>Sea-<span class="hlt">ice</span> deformation in a coupled ocean-sea-<span class="hlt">ice</span> model and in satellite remote sensing data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Spreen, Gunnar; Kwok, Ron; Menemenlis, Dimitris; Nguyen, An T.</p> <p>2017-07-01</p> <p>A realistic representation of sea-<span class="hlt">ice</span> deformation in models is important for accurate simulation of the sea-<span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>. Simulated sea-<span class="hlt">ice</span> deformation from numerical simulations with 4.5, 9, and 18 km horizontal grid spacing and a viscous-plastic (VP) sea-<span class="hlt">ice</span> rheology are compared with synthetic aperture radar (SAR) satellite observations (RGPS, RADARSAT Geophysical Processor System) for the time period 1996-2008. All three simulations can reproduce the large-scale <span class="hlt">ice</span> deformation patterns, but small-scale sea-<span class="hlt">ice</span> deformations and linear kinematic features (LKFs) are not adequately reproduced. The mean sea-<span class="hlt">ice</span> total deformation rate is about 40 % lower in all model solutions than in the satellite observations, especially in the seasonal sea-<span class="hlt">ice</span> zone. A decrease in model grid spacing, however, produces a higher density and more localized <span class="hlt">ice</span> deformation features. The 4.5 km simulation produces some linear kinematic features, but not with the right frequency. The dependence on length scale and probability density functions (PDFs) of absolute divergence and shear for all three model solutions show a power-law scaling behavior similar to RGPS observations, contrary to what was found in some previous studies. Overall, the 4.5 km simulation produces the most realistic divergence, vorticity, and shear when compared with RGPS data. This study provides an evaluation of high and coarse-resolution viscous-plastic sea-<span class="hlt">ice</span> simulations based on spatial distribution, time series, and power-law scaling metrics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=D+AND+alemberts+AND+principle&id=EJ723641','ERIC'); return false;" href="https://eric.ed.gov/?q=D+AND+alemberts+AND+principle&id=EJ723641"><span>When Equal <span class="hlt">Masses</span> Don't <span class="hlt">Balance</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Newburgh, Ronald; Peidle, Joseph; Rueckner, Wolfgang</p> <p>2004-01-01</p> <p>We treat a modified Atwood's machine in which equal <span class="hlt">masses</span> do not <span class="hlt">balance</span> because of being in an accelerated frame of reference. Analysis of the problem illuminates the meaning of inertial forces, d'Alembert's principle, the use of free-body diagrams and the selection of appropriate systems for the diagrams. In spite of the range of these…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P53H..07W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P53H..07W"><span><span class="hlt">Mass</span> Fluxes of <span class="hlt">Ice</span> and Oxygen Across the Entire Lid of Lake Vostok from Observations of Englacial Radiowave Attenuation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Winebrenner, D. P.; Kintner, P. M. S.; MacGregor, J. A.</p> <p>2017-12-01</p> <p>Over deep Antarctic subglacial lakes, spatially varying <span class="hlt">ice</span> thickness and the pressure-dependent melting point of <span class="hlt">ice</span> result in areas of melting and accretion at the <span class="hlt">ice</span>-water interface, i.e., the lake lid. These <span class="hlt">ice</span> <span class="hlt">mass</span> fluxes drive lake circulation and, because basal Antarctic <span class="hlt">ice</span> contains air-clathrate, affect the input of oxygen to the lake, with implications for subglacial life. Inferences of melting and accretion from radar-layer tracking and geodesy are limited in spatial coverage and resolution. Here we develop a new method to estimate rates of accretion, melting, and the resulting oxygen input at a lake lid, using airborne radar data over Lake Vostok together with <span class="hlt">ice</span>-temperature and chemistry data from the Vostok <span class="hlt">ice</span> core. Because the lake lid is a coherent reflector of known reflectivity (at our radar frequency), we can infer depth-averaged radiowave attenuation in the <span class="hlt">ice</span>, with spatial resolution 1 km along flight lines. Spatial variation in attenuation depends mostly on variation in <span class="hlt">ice</span> temperature near the lid, which in turn varies strongly with <span class="hlt">ice</span> <span class="hlt">mass</span> flux at the lid. We model <span class="hlt">ice</span> temperature versus depth with <span class="hlt">ice</span> <span class="hlt">mass</span> flux as a parameter, thus linking that flux to (observed) depth-averaged attenuation. The resulting map of melt- and accretion-rates independently reproduces features known from earlier studies, but now covers the entire lid. We find that accretion is dominant when integrated over the lid, with an <span class="hlt">ice</span> imbalance of 0.05 to 0.07 km3 a-1, which is robust against uncertainties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C54A..02P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C54A..02P"><span>A Historical Forcing <span class="hlt">Ice</span> Sheet Model Validation Framework for Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Price, S. F.; Hoffman, M. J.; Howat, I. M.; Bonin, J. A.; Chambers, D. P.; Kalashnikova, I.; Neumann, T.; Nowicki, S.; Perego, M.; Salinger, A.</p> <p>2014-12-01</p> <p>We propose an <span class="hlt">ice</span> sheet model testing and validation framework for Greenland for the years 2000 to the present. Following Perego et al. (2014), we start with a realistic <span class="hlt">ice</span> sheet initial condition that is in quasi-equilibrium with climate forcing from the late 1990's. This initial condition is integrated forward in time while simultaneously applying (1) surface <span class="hlt">mass</span> <span class="hlt">balance</span> forcing (van Angelen et al., 2013) and (2) outlet glacier flux anomalies, defined using a new dataset of Greenland outlet glacier flux for the past decade (Enderlin et al., 2014). Modeled rates of <span class="hlt">mass</span> and elevation change are compared directly to remote sensing observations obtained from GRACE and ICESat. Here, we present a detailed description of the proposed validation framework including the <span class="hlt">ice</span> sheet model and model forcing approach, the model-to-observation comparison process, and initial results comparing model output and observations for the time period 2000-2013.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Geomo.261....1C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Geomo.261....1C"><span>Response of <span class="hlt">ice</span> caves to weather extremes in the southeastern Alps, Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Colucci, R. R.; Fontana, D.; Forte, E.; Potleca, M.; Guglielmin, M.</p> <p>2016-05-01</p> <p>High altitude karstic environments often preserve permanent <span class="hlt">ice</span> deposits within caves, representing the lesser-known portion of the cryosphere. Despite being not so widespread and easily reachable as mountain glaciers and <span class="hlt">ice</span> caps, <span class="hlt">ice</span> caves preserve much information about past environmental changes and climatic evolution. We selected 1111 <span class="hlt">ice</span> caves from the existing cave inventory, predominantly but not exclusively located in the periglacial domain where permafrost is not dominant (i.e., with mean annual air temperature < 3 °C but not in a permafrost environment). The influence of climate and topography on <span class="hlt">ice</span> cave distribution is also investigated. In order to assess the thickness and the inner structure of the deposits, we selected two exemplary <span class="hlt">ice</span> caves in the Canin massif (Julian Alps) performing several multifrequency GPR surveys. A strong influence of global and local climate change in the evolution of the <span class="hlt">ice</span> deposits has been particularly highlighted in the dynamic <span class="hlt">ice</span> cave type, especially in regard to the role of weather extremes. The natural response of <span class="hlt">ice</span> caves to a warming climate could lead to a fast reduction of such <span class="hlt">ice</span> <span class="hlt">masses</span>. The increased occurrence of weather extremes, especially warmer and more intense precipitation caused by higher mean 0 °C-isotherms, could in fact be crucial in the future <span class="hlt">mass</span> <span class="hlt">balance</span> evolution of such permanent <span class="hlt">ice</span> deposits.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.G21A0871Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.G21A0871Z"><span>Rapid <span class="hlt">Ice</span> Loss at Vatnajokull,Iceland Since Late 1990s Constrained by Synthetic Aperture Radar Interferometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, W.; Amelung, F.; Dixon, T. H.; Wdowinski, S.</p> <p>2012-12-01</p> <p>Synthetic aperture radar interferometry time series is applied over Vatnajokull, Iceland by using 15 years ERS data. <span class="hlt">Ice</span> loss at Vatnajokull accelerates since late 1990s especially after 21th century. Clear uplift signal due to <span class="hlt">ice</span> <span class="hlt">mass</span> loss is detected. The rebound signal is generally linear and increases a little bit after 2000. The relative annual velocity (GPS station 7485 as reference) is about 12 mm/yr at the <span class="hlt">ice</span> cap edge, which matches the previous studies using GPS. The standard deviation compared to 11 GPS stations in this area is about 2 mm/yr. A relative-value modeling method ignoring the effect of viscous flow is chosen assuming elastic half space earth. The final <span class="hlt">ice</span> loss estimation - 83 cm/yr - matches the climatology model with ground observations. Small Baseline Subsets is applied for time series analysis. Orbit error coupling with long wavelength phase trend due to horizontal plate motion is removed based on a second polynomial model. For simplicity, we do not consider atmospheric delay in this area because of no complex topography and small-scale turbulence is eliminated well after long-term average when calculating the annual mean velocity. Some unwrapping error still exits because of low coherence. Other uncertainties can be the basic assumption of <span class="hlt">ice</span> loss pattern and spatial variation of the elastic parameters. It is the first time we apply InSAR time series for <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> study and provide detailed error and uncertainty analysis. The successful of this application proves InSAR as an option for <span class="hlt">mass</span> <span class="hlt">balance</span> study and it is also important for validation of different <span class="hlt">ice</span> loss estimation techniques.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.C21C0458P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.C21C0458P"><span>Outlet Glacier-<span class="hlt">Ice</span> Shelf-Ocean Interactions: Is the Tail Wagging the Dog?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parizek, B. R.; Walker, R. T.; Rinehart, S. K.</p> <p>2009-12-01</p> <p>While the massive interior regions of the Antarctic and Greenland <span class="hlt">Ice</span> Sheets are presently ``resting quietly", the lower elevations of many outlet glaciers are experiencing dramatic adjustments due to changes in <span class="hlt">ice</span> dynamics and/or surface <span class="hlt">mass</span> <span class="hlt">balance</span>. Oceanic and/or atmospheric forcing in these marginal regions often leads to <span class="hlt">mass</span> deficits for entire outlet basins. Therefore, coupling the wagging tail of <span class="hlt">ice</span>-ocean interactions with the vast <span class="hlt">ice</span>-sheet reservoirs is imperative for accurate assessments of future sea-level rise. To study <span class="hlt">ice</span>-ocean dynamic processes, we couple an ocean-plume model that simulates <span class="hlt">ice</span>-shelf basal melting rates based on temperature and salinity profiles combined with plume dynamics associated with the geometry of the <span class="hlt">ice</span>-shelf cavity (following Jenkins, 1991 and Holland and Jenkins, 1999) with a two-dimensional, isothermal model of outlet glacier-<span class="hlt">ice</span> shelf flow (as used in Alley et al., 2007; Walker et al., 2008; Parizek et al., in review). Depending on the assigned temperature and salinity profiles, the ocean model can simulate both water-<span class="hlt">mass</span> end-members: either cold High Salinity Shelf Water (HSSW) or relatively warm Circumpolar Deep Water (CDW), as well as between-member conditions. Notably, the coupled system exhibits sensitivity to the initial conditions. In particular, melting concentrated near the grounding line has the greatest effect in forcing grounding-line retreat. Retreat is further enhanced by a positive feedback between the ocean and <span class="hlt">ice</span>, as the focused melt near the grounding line leads to an increase in the local slope of the basal <span class="hlt">ice</span>, thereby enhancing buoyancy-driven plume flow and subsequent melt rates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRC..123..864J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRC..123..864J"><span>Ocean-Forced <span class="hlt">Ice</span>-Shelf Thinning in a Synchronously Coupled <span class="hlt">Ice</span>-Ocean Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jordan, James R.; Holland, Paul R.; Goldberg, Dan; Snow, Kate; Arthern, Robert; Campin, Jean-Michel; Heimbach, Patrick; Jenkins, Adrian</p> <p>2018-02-01</p> <p>The first fully synchronous, coupled <span class="hlt">ice</span> shelf-ocean model with a fixed grounding line and imposed upstream <span class="hlt">ice</span> velocity has been developed using the MITgcm (Massachusetts Institute of Technology general circulation model). Unlike previous, asynchronous, approaches to coupled modeling our approach is fully conservative of heat, salt, and <span class="hlt">mass</span>. Synchronous coupling is achieved by continuously updating the <span class="hlt">ice</span>-shelf thickness on the ocean time step. By simulating an idealized, warm-water <span class="hlt">ice</span> shelf we show how raising the pycnocline leads to a reduction in both <span class="hlt">ice</span>-shelf <span class="hlt">mass</span> and back stress, and hence buttressing. Coupled runs show the formation of a western boundary channel in the <span class="hlt">ice</span>-shelf base due to increased melting on the western boundary due to Coriolis enhanced flow. Eastern boundary <span class="hlt">ice</span> thickening is also observed. This is not the case when using a simple depth-dependent parameterized melt, as the <span class="hlt">ice</span> shelf has relatively thinner sides and a thicker central "bulge" for a given <span class="hlt">ice</span>-shelf <span class="hlt">mass</span>. <span class="hlt">Ice</span>-shelf geometry arising from the parameterized melt rate tends to underestimate backstress (and therefore buttressing) for a given <span class="hlt">ice</span>-shelf <span class="hlt">mass</span> due to a thinner <span class="hlt">ice</span> shelf at the boundaries when compared to coupled model simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.G31C0924M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.G31C0924M"><span>Temporal variability of the Antarctic <span class="hlt">Ice</span> sheet observed from space-based geodesy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Memin, A.; King, M. A.; Boy, J. P.; Remy, F.</p> <p>2017-12-01</p> <p>Quantifying the Antarctic <span class="hlt">Ice</span> Sheet (AIS) <span class="hlt">mass</span> <span class="hlt">balance</span> still remains challenging as several processes compete to differing degrees at the basin scale with regional variations, leading to multiple <span class="hlt">mass</span> redistribution patterns. For instance, analysis of linear trends in surface-height variations from 1992-2003 and 2002-2006 shows that the AIS is subject to decimetric scale variability over periods of a few years. Every year, snowfalls in Antarctica represent the equivalent of 6 mm of the mean sea level. Therefore, any fluctuation in precipitation can lead to changes in sea level. Besides, over the last decade, several major glaciers have been thinning at an accelerating rate. Understanding the processes that interact on the <span class="hlt">ice</span> sheet is therefore important to precisely determine the response of the <span class="hlt">ice</span> sheet to a rapid changing climate and estimate its contribution to sea level changes. We estimate seasonal and interannual changes of the AIS between January 2003 and October 2010 and to the end of 2016 from a combined analysis of surface-elevation and surface-<span class="hlt">mass</span> changes derived from Envisat data and GRACE solutions, and from GRACE solutions only, respectively. While we obtain a good correlation for the interannual signal between the two techniques, important differences (in amplitude, phase, and spatial pattern) are obtained for the seasonal signal. We investigate these discrepancies by comparing the crustal motion observed by GPS and those predicted using monthly surface <span class="hlt">mass</span> <span class="hlt">balance</span> derived from the regional atmospheric climate model RACMO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008GeoRL..3522503K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008GeoRL..3522503K"><span><span class="hlt">Mass</span> loss on Himalayan glacier endangers water resources</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kehrwald, Natalie M.; Thompson, Lonnie G.; Tandong, Yao; Mosley-Thompson, Ellen; Schotterer, Ulrich; Alfimov, Vasily; Beer, Jürg; Eikenberg, Jost; Davis, Mary E.</p> <p>2008-11-01</p> <p><span class="hlt">Ice</span> cores drilled from glaciers around the world generally contain horizons with elevated levels of beta radioactivity including 36Cl and 3H associated with atmospheric thermonuclear bomb testing in the 1950s and 1960s. <span class="hlt">Ice</span> cores collected in 2006 from Naimona'nyi Glacier in the Himalaya (Tibet) lack these distinctive marker horizons suggesting no net accumulation of <span class="hlt">mass</span> (<span class="hlt">ice</span>) since at least 1950. Naimona'nyi is the highest glacier (6050 masl) documented to be losing <span class="hlt">mass</span> annually suggesting the possibility of similar <span class="hlt">mass</span> loss on other high-elevation glaciers in low and mid-latitudes under a warmer Earth scenario. If climatic conditions dominating the <span class="hlt">mass</span> <span class="hlt">balance</span> of Naimona'nyi extend to other glaciers in the region, the implications for water resources could be serious as these glaciers feed the headwaters of the Indus, Ganges, and Brahmaputra Rivers that sustain one of the world's most populous regions.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C42A..01A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C42A..01A"><span>Continent-Wide Estimates of Antarctic Strain Rates from Landsat 8-Derived Velocity Grids and Their Application to <span class="hlt">Ice</span> Shelf Studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alley, K. E.; Scambos, T.; Anderson, R. S.; Rajaram, H.; Pope, A.; Haran, T.</p> <p>2017-12-01</p> <p>Strain rates are fundamental measures of <span class="hlt">ice</span> flow used in a wide variety of glaciological applications including investigations of bed properties, calculations of basal <span class="hlt">mass</span> <span class="hlt">balance</span> on <span class="hlt">ice</span> shelves, application to Glen's flow law, and many other studies. However, despite their extensive application, strain rates are calculated using widely varying methods and length scales, and the calculation details are often not specified. In this study, we compare the results of nominal and logarithmic strain-rate calculations based on a satellite-derived velocity field of the Antarctic <span class="hlt">ice</span> sheet generated from Landsat 8 satellite data. Our comparison highlights the differences between the two commonly used approaches in the glaciological literature. We evaluate the errors introduced by each code and their impacts on the results. We also demonstrate the importance of choosing and specifying a length scale over which strain-rate calculations are made, which can have large local impacts on other derived quantities such as basal <span class="hlt">mass</span> <span class="hlt">balance</span> on <span class="hlt">ice</span> shelves. We present strain-rate data products calculated using an approximate viscous length-scale with satellite observations of <span class="hlt">ice</span> velocity for the Antarctic continent. Finally, we explore the applications of comprehensive strain-rate maps to future <span class="hlt">ice</span> shelf studies, including investigations of <span class="hlt">ice</span> fracture, calving patterns, and stability analyses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1714078M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1714078M"><span>Annual and seasonal <span class="hlt">mass</span> <span class="hlt">balances</span> of Chhota Shigri Glacier (benchmark glacier, Western Himalaya), India</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mandal, Arindan; Ramanathan, Alagappan; Farooq Azam, Mohd; Wagnon, Patrick; Vincent, Christian; Linda, Anurag; Sharma, Parmanand; Angchuk, Thupstan; Bahadur Singh, Virendra; Pottakkal, Jose George; Kumar, Naveen; Soheb, Mohd</p> <p>2015-04-01</p> <p>Several studies on Himalayan glaciers have been recently initiated as they are of particular interest in terms of future water supply, regional climate change and sea-level rise. In 2002, a long-term monitoring program was initiated on Chhota Shigri Glacier (15.7 square km, 9 km long, 6263-4050 m a.s.l.) located in Lahaul and Spiti Valley, Himachal Pradesh, India. This glacier lies in the monsoon-arid transition zone (western Himalaya) and is a representative glacier in Lahaul and Spiti Valley. While annual <span class="hlt">mass</span> <span class="hlt">balances</span> have been measured continuously since 2002 using the glaciological method, seasonal scale observations began in 2009. The annual and seasonal <span class="hlt">mass</span> <span class="hlt">balances</span> were then analyzed along with meteorological conditions in order to understand the role of winter and summer <span class="hlt">balances</span> on annual glacier-wide <span class="hlt">mass</span> <span class="hlt">balance</span> of Chhota Shigri glacier. During the period 2002-2013, the glacier experienced a negative glacier-wide <span class="hlt">mass</span> <span class="hlt">balance</span> of -0.59±0.40 m w.e. a-1 with a cumulative glaciological <span class="hlt">mass</span> <span class="hlt">balance</span> of -6.45 m w.e. Annual glacier-wide <span class="hlt">mass</span> <span class="hlt">balances</span> were negative except for four years (2004/05, 2008/09, 2009/10 and 2010/11) where it was generally close to <span class="hlt">balanced</span> conditions. Equilibrium line altitude (ELA) for steady state condition is calculated as 4950 m a.s.l. corresponding to an accumulation area ratio (AAR) of 62% using annual glacier-wide <span class="hlt">mass</span> <span class="hlt">balance</span>, ELA and AAR data between 2002 and 2013. The winter glacier-wide <span class="hlt">mass</span> <span class="hlt">balance</span> between 2009 and 2013 ranges from a maximum value of 1.38 m w.e. in 2009/10 to a minimum value of 0.89 in 2012/13 year whereas the summer glacier-wide <span class="hlt">mass</span> <span class="hlt">balance</span> varies from the highest value of -0.95 m w.e. in 2010/11 to the lowest value of -1.72 m w.e. in 2011/12 year. The mean vertical <span class="hlt">mass</span> <span class="hlt">balance</span> gradient between 2002 and 2013 was 0.66 m w.e. (100 m)-1 quite similar to Alps, Nepalese Himalayas etc. Over debris covered area, the gradients are highly variable with a negative mean value of -2.15 m w.e. (100 m)-1 over 2002</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010002430&hterms=carbon+balance&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dcarbon%2Bbalance','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010002430&hterms=carbon+balance&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dcarbon%2Bbalance"><span>Troughs in <span class="hlt">Ice</span> Sheets and Other Icy Deposits on Mars: Analysis of Their Radiative <span class="hlt">Balance</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fountain, A.; Kargel, J.; Lewis, K.; MacAyeal, D.; Pfeffer, T.; Zwally, H. J.</p> <p>2000-01-01</p> <p>It has long been known that groove-like structures in glaciers and <span class="hlt">ice</span> sheets can trap more incoming solar radiation than is the case for a 'normal' flat, smooth surface. In this presentation, we shall describe the radiative regimes of typical scarps and troughs on icy surfaces of Mars, and suggest how these features originate and evolve through time. The basis of our analysis is the radiation <span class="hlt">balance</span> model presented by Pfeffer and Bretherton. Their model considers the visible band radiation regime of a V-shaped groove on a terrestrial <span class="hlt">ice</span> surface, and shows that absorbed energy can be enhanced by up to 50 percent for grooves with small opening angles and with typical polar values of the solar zenith angle. Our work extends this model by considering: (a) departures from V-shaped geometry, (b) both englacial and surficial dust and debris, and (c) the infrared spectrum. We apply the extended model to various features on the Martian surface, including the spiral-like scarps on the Northern and Southern <span class="hlt">ice</span> sheets, the large-scale chasms (e.g., Chasm Borealis), and groove-like lineations on valley floors thought to be filled with mixtures of dust and icy substances. In conjunction with study of valley-closure experiments, we suggest that spiral-like scarps and chasms are stable features of the Martian climate regime. We also suggest that further study of scarps and chasms may shed light on the composition (i.e., relative proportions of water <span class="hlt">ice</span>, carbon-dioxide <span class="hlt">ice</span> and dust) of the Martian <span class="hlt">ice</span> sheets and valley fills.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.4621R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.4621R"><span>State of Arctic Sea <span class="hlt">Ice</span> North of Svalbard during N-<span class="hlt">ICE</span>2015</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rösel, Anja; King, Jennifer; Gerland, Sebastian</p> <p>2016-04-01</p> <p>The N-<span class="hlt">ICE</span>2015 cruise, led by the Norwegian Polar Institute, was a drift experiment with the research vessel R/V Lance from January to June 2015, where the ship started the drift North of Svalbard at 83°14.45' N, 21°31.41' E. The drift was repeated as soon as the vessel drifted free. Altogether, 4 <span class="hlt">ice</span> stations where installed and the complex ocean-sea <span class="hlt">ice</span>-atmosphere system was studied with an interdisciplinary Approach. During the N-<span class="hlt">ICE</span>2015 cruise, extensive <span class="hlt">ice</span> thickness and snow depth measurements were performed during both, winter and summer conditions. Total <span class="hlt">ice</span> and snow thickness was measured with ground-based and airborne electromagnetic instruments; snow depth was measured with a GPS snow depth probe. Additionally, <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> and snow buoys were deployed. Snow and <span class="hlt">ice</span> thickness measurements were performed on repeated transects to quantify the <span class="hlt">ice</span> growth or loss as well as the snow accumulation and melt rate. Additionally, we collected independent values on surveys to determine the general <span class="hlt">ice</span> thickness distribution. Average snow depths of 32 cm on first year <span class="hlt">ice</span>, and 52 cm on multi-year <span class="hlt">ice</span> were measured in January, the mean snow depth on all <span class="hlt">ice</span> types even increased until end of March to 49 cm. The average total <span class="hlt">ice</span> and snow thickness in winter conditions was 1.92 m. During winter we found a small growth rate on multi-year <span class="hlt">ice</span> of about 15 cm in 2 months, due to above-average snow depths and some extraordinary storm events that came along with mild temperatures. In contrast thereto, we also were able to study new <span class="hlt">ice</span> formation and thin <span class="hlt">ice</span> on newly formed leads. In summer conditions an enormous melt rate, mainly driven by a warm Atlantic water inflow in the marginal <span class="hlt">ice</span> zone, was observed during two <span class="hlt">ice</span> stations with melt rates of up to 20 cm per 24 hours. To reinforce the local measurements around the ship and to confirm their significance on a larger scale, we compare them to airborne thickness measurements and classified SAR-satellite scenes. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C51E..07C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C51E..07C"><span>Investigation of Controls on <span class="hlt">Ice</span> Dynamics in Northeast Greenland from <span class="hlt">Ice</span>-Thickness Change Record Using <span class="hlt">Ice</span> Sheet System Model (ISSM)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Csatho, B. M.; Larour, E. Y.; Schenk, A. F.; Schlegel, N.; Duncan, K.</p> <p>2015-12-01</p> <p>We present a new, complete <span class="hlt">ice</span> thickness change reconstruction of the NE sector of the Greenland <span class="hlt">Ice</span> Sheet for 1978-2014, partitioned into changes due to surface processes and <span class="hlt">ice</span> dynamics. Elevation changes are computed from all available stereoscopic DEMs, and laser altimetry data (ICESat, ATM, LVIS). Surface <span class="hlt">Mass</span> <span class="hlt">Balance</span> and firn-compaction estimates are from RACMO2.3. Originating nearly at the divide of the Greenland <span class="hlt">Ice</span> Sheet (GrIS), the dynamically active North East <span class="hlt">Ice</span> Stream (NEGIS) is capable of rapidly transmitting <span class="hlt">ice</span>-marginal forcing far inland. Thus, NEGIS provides a possible mechanism for a rapid drawdown of <span class="hlt">ice</span> from the <span class="hlt">ice</span> sheet interior as marginal warming, thinning and retreat continues. Our altimetry record shows accelerating dynamic thinning of Zachariæ Isstrom, initially limited to the deepest part of the fjord near the calving front (1978-2000) and then extending at least 75 km inland. At the same time, changes over the Nioghalvfjerdsfjorden (N79) Glacier are negligible. We also detect localized large dynamic changes at higher elevations on the <span class="hlt">ice</span> sheet. These thickness changes, often occurring at the onset of fast flow, could indicate rapid variations of basal lubrication due to rerouting of subglacial drainage. We investigate the possible causes of the observed spatiotemporal pattern of <span class="hlt">ice</span> sheet elevation changes using the <span class="hlt">Ice</span> Sheet System Model (ISSM). This work build on our previous studies examining the sensitivity of <span class="hlt">ice</span> flow within the Northeast Greenland <span class="hlt">Ice</span> Stream (NEGIS) to key fields, including <span class="hlt">ice</span> viscosity, basal drag. We assimilate the new altimetry record into ISSM to improve the reconstruction of basal friction and <span class="hlt">ice</span> viscosity. Finally, airborne geophysical (gravity, magnetic) and <span class="hlt">ice</span>-penetrating radar data is examined to identify the potential geologic controls on the <span class="hlt">ice</span> thickness change pattern. Our study provides the first comprehensive reconstruction of <span class="hlt">ice</span> thickness changes for the entire NEGIS drainage basin during</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C44A..03Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C44A..03Y"><span>Greenland <span class="hlt">ice</span> sheet beyond 2100: Simulating its evolution and influence using the coupled climate-<span class="hlt">ice</span> sheet model EC-Earth - PISM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, S.; Christensen, J. H.; Madsen, M. S.; Ringgaard, I. M.; Petersen, R. A.; Langen, P. P.</p> <p>2017-12-01</p> <p>Greenland <span class="hlt">ice</span> sheet (GrIS) is observed undergoing a rapid change in the recent decades, with an increasing area of surface melting and ablation and a speeding <span class="hlt">mass</span> loss. Predicting the GrIS changes and their climate consequences relies on the understanding of the interaction of the GrIS with the climate system on both global and local scales, and requires climate model systems incorporating with an explicit and physically consistent <span class="hlt">ice</span> sheet module. In this work we study the GrIS evolution and its interaction with the climate system using a fully coupled global climate model with a dynamical <span class="hlt">ice</span> sheet model for the GrIS. The coupled model system, EC-EARTH - PISM, consisting of the atmosphere-ocean-sea <span class="hlt">ice</span> model system EC-EARTH, and the Parallel <span class="hlt">Ice</span> Sheet Model (PISM), has been employed for a 1400-year simulation forced by CMIP5 historical forcing from 1850 to 2005 and continued along an extended RCP8.5 scenario with the forcing peaking at 2200 and stabilized hereafter. The simulation reveals that, following the anthropogenic forcing increase, the global mean surface temperature rapidly rises about 10 °C in the 21st and 22nd century. After the forcing stops increasing after 2200, the temperature change slows down and eventually stabilizes at about 12.5 °C above the preindustrial level. In response to the climate warming, the GrIS starts losing <span class="hlt">mass</span> slowly in the 21st century, but the <span class="hlt">ice</span> retreat accelerates substantially after 2100 and <span class="hlt">ice</span> <span class="hlt">mass</span> loss continues hereafter at a constant rate of approximately 0.5 m sea level rise equivalence per 100 years, even as the warming rate gradually levels off. Ultimately the volume and extent of GrIS reduce to less than half of its preindustrial value. To understand the interaction of GrIS with the climate system, the characteristics of atmospheric and oceanic circulation in the warm climate are analyzed. The circulation patterns associated with the negative surface <span class="hlt">mass</span> <span class="hlt">balance</span> that leads to GrIS retreat are investigated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060024016','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060024016"><span><span class="hlt">Mass</span> Changes of the Greenland and Antarctic <span class="hlt">Ice</span> Sheets and Shelves and Contributions to Sea-level Rise: 1992-2002</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Giovinetto, Mario B.; Li, Jun; Cornejo, Helen G.; Beckley, Matthew A.; Brenner, Anita C.; Saba, Jack L.; Yi, Donghui</p> <p>2005-01-01</p> <p>Changes in <span class="hlt">ice</span> <span class="hlt">mass</span> are estimated from elevation changes derived from 10.5 years (Greenland) and 9 years (Antarctica) of satellite radar altimetry data from the European Remote-sensing Satellites ERS-1 and -2. For the first time, the dH/dt values are adjusted for changes in surface elevation resulting from temperature-driven variations in the rate of fun compaction. The Greenland <span class="hlt">ice</span> sheet is thinning at the margins (-42 plus or minus 2 Gta(sup -1) below the equilibrium line altitude (ELA)) and growing inland (+53 plus or minus 2 Gt a(sup -1)above the ELA) with a small overall <span class="hlt">mass</span> gain (+11 plus or minus 3 Gt a(sup -1); -0.03 mm a(sup -1) SLE (sea level equivalent)). The <span class="hlt">ice</span> sheet in West Antarctica (WA) is losing <span class="hlt">mass</span> (-47 (dot) 4 GT a(sup -1) and the <span class="hlt">ice</span> sheet in East Antarctica (EA) shows a small <span class="hlt">mass</span> gain (+16 plus or minus 11 Gt a(sup -1) for a combined net change of -31 plus or minus 12 Gt a(sup -1) (+0.08 mm a(sup -1) SLE)). The contribution of the three <span class="hlt">ice</span> sheets to sea level is +0.05 plus or minus 0.03 mm a(sup -1). The Antarctic <span class="hlt">ice</span> shelves show corresponding <span class="hlt">mass</span> changes of -95 (dot) 11 Gt a(sup -1) in WA and +142 plus or minus 10 Gt a(sup -1) in EA. Thinning at the margins of the Greenland <span class="hlt">ice</span> sheet and growth at higher elevations is an expected response to increasing temperatures and precipitation in a warming climate. The marked thinnings in the Pine Island and Thwaites Glacier basins of WA and the Totten Glacier basin in EA are probably <span class="hlt">ice</span>-dynamic responses to long-term climate change and perhaps past removal of their adjacent <span class="hlt">ice</span> shelves. The <span class="hlt">ice</span> growth in the southern Antarctic Peninsula and parts of EA may be due to increasing precipitation during the last century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C31A..03A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C31A..03A"><span>Interactions Between <span class="hlt">Ice</span> Thickness, Bottom <span class="hlt">Ice</span> Algae, and Transmitted Spectral Irradiance in the Chukchi Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arntsen, A. E.; Perovich, D. K.; Polashenski, C.; Stwertka, C.</p> <p>2015-12-01</p> <p>The amount of light that penetrates the Arctic sea <span class="hlt">ice</span> cover impacts sea-<span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> as well as ecological processes in the upper ocean. The seasonally evolving macro and micro spatial variability of transmitted spectral irradiance observed in the Chukchi Sea from May 18 to June 17, 2014 can be primarily attributed to variations in snow depth, <span class="hlt">ice</span> thickness, and bottom <span class="hlt">ice</span> algae concentrations. This study characterizes the interactions among these dominant variables using observed optical properties at each sampling site. We employ a normalized difference index to compute estimates of Chlorophyll a concentrations and analyze the increased attenuation of incident irradiance due to absorption by biomass. On a kilometer spatial scale, the presence of bottom <span class="hlt">ice</span> algae reduced the maximum transmitted irradiance by about 1.5 orders of magnitude when comparing floes of similar snow and <span class="hlt">ice</span> thicknesses. On a meter spatial scale, the combined effects of disparities in the depth and distribution of the overlying snow cover along with algae concentrations caused maximum transmittances to vary between 0.0577 and 0.282 at a single site. Temporal variability was also observed as the average integrated transmitted photosynthetically active radiation increased by one order of magnitude to 3.4% for the last eight measurement days compared to the first nine. Results provide insight on how interrelated physical and ecological parameters of sea <span class="hlt">ice</span> in varying time and space may impact new trends in Arctic sea <span class="hlt">ice</span> extent and the progression of melt.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1013699','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1013699"><span>Applying High Resolution Imagery to Understand the Role of Dynamics in the Diminishing Arctic Sea <span class="hlt">Ice</span> Cover</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2015-09-30</p> <p>observations collected by the NASA Operation <span class="hlt">Ice</span>Bridge (OIB) project, including high-resolution visible-band imagery (Onana et al., 2013), snow depth ( Newman et...2014; Farrell et al., 2015; Hutchings et al., 2015; Richter-Menge and Farrell, 2014), snow depth ( Newman et al., 2014; Webster et al., 2014), sea <span class="hlt">ice</span>...with A. Mahoney , H. Eicken and C. Haas on an ONR-funded project "<span class="hlt">Mass</span> <span class="hlt">balance</span> of multi-year sea <span class="hlt">ice</span> in the southern Beaufort Sea". This effort</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.G13B1099B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.G13B1099B"><span>Measuring Two Decades of <span class="hlt">Ice</span> <span class="hlt">Mass</span> Loss using GRACE and SLR</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bonin, J. A.; Chambers, D. P.</p> <p>2016-12-01</p> <p>We use Satellite Laser Ranging (SLR) to extend the time series of <span class="hlt">ice</span> <span class="hlt">mass</span> change back in time to 1994. The SLR series is of far lesser spatial resolution than GRACE, so we apply a constrained inversion technique to better localize the signal. We approximate the likely errors due to SLR's measurement errors combined with the inversion errors from using a low-resolution series, then estimate the interannual <span class="hlt">mass</span> change over Greenland and Antarctica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C34A..02P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C34A..02P"><span>The impact of short-term heat storage on the <span class="hlt">ice</span>-albedo feedback loop</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Polashenski, C.; Wright, N.; Perovich, D. K.; Song, A.; Deeb, E. J.</p> <p>2016-12-01</p> <p>The partitioning of solar energy in the <span class="hlt">ice</span>-ocean-atmosphere environment is a powerful control over Arctic sea <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span>. Ongoing transitions of the sea <span class="hlt">ice</span> toward a younger, thinner state are enhancing absorption of solar energy and contributing to further declines in sea <span class="hlt">ice</span> in a classic <span class="hlt">ice</span>-albedo feedback. Here we investigate the solar energy <span class="hlt">balance</span> over shorter timescales. In particular, we are concerned with short term delays in the transfer of absorbed solar energy to the <span class="hlt">ice</span> caused by heat storage in the upper ocean. By delaying the realization of <span class="hlt">ice</span> melt, and hence albedo decline, heat storage processes effectively retard the intra-season <span class="hlt">ice</span>-albedo feedback. We seek to quantify the impact and variability of such intra-season storage delays on full season energy absorption. We use in-situ data collected from Arctic Observing Network (AON) sea <span class="hlt">ice</span> sites, synthesized with the results of imagery processed from high resolution optical satellites, and basin-scale remote sensing products to approach the topic. AON buoys are used to monitor the storage and flux of heat, while satellite imagery allows us to quantify the evolution of surrounding <span class="hlt">ice</span> conditions and predict the aggregate scale solar absorption. We use several test sites as illustrative cases and demonstrate that temporary heat storage can have substantial impacts on seasonal energy absorption and <span class="hlt">ice</span> loss. A companion to this work is presented by N. Wright at this meeting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMGC43C0737Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMGC43C0737Y"><span><span class="hlt">Mass</span> <span class="hlt">Balance</span> of a Maritime Glacier on the Southeast Tibetan Plateau and Its Climatic Sensitivity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, W.</p> <p>2014-12-01</p> <p>Based on glacio-meteorological measurements and <span class="hlt">mass-balance</span> stake records during the five-year period of 2005-2010 on the southeast Tibetan Plateau, an energy-<span class="hlt">mass</span> <span class="hlt">balance</span> model was applied to study the surface <span class="hlt">mass</span> <span class="hlt">balance</span> of the Parlung No. 94 Glacier, as well as its response to regional climate conditions. The primary physical parameters involved in the model were locally calibrated by using relevant glacio-meteorological datasets. The good agreement between the snowpack height/<span class="hlt">mass</span> <span class="hlt">balance</span> simulations and the in-situ measurements available from a total of 12 monitoring stakes over this glacier confirmed the satisfactory performance of the energy-<span class="hlt">mass</span> <span class="hlt">balance</span> model. Results suggested that the recent state of the Parlung No. 94 Glacier was far removed from the 'ideal' climatic regime leading to zero <span class="hlt">mass</span> <span class="hlt">balance</span>, with its annual <span class="hlt">mass</span> <span class="hlt">balance</span> of approximately -0.9 m w.e. during 2005-2010. Climatic sensitivity experiments were also carried out to interpret the observed <span class="hlt">mass-balance</span> changes, and the experiments demonstrated that the maritime glaciers concerned herein were theoretically more vulnerable to ongoing climate warming on the Tibetan Plateau than potential changes in the amount of precipitation. A plausible causal explanation for the recent glacier shrinkage in this region was concerned with the increasing air temperature. Moreover, both the <span class="hlt">mass</span> <span class="hlt">balance</span> simulations and the field measurements indicated that the <span class="hlt">mass</span> accumulation over this maritime glacier occurred primarily in the boreal spring. Such "spring-accumulation type" glaciers are presumed to be distributed mainly within a narrow wedge-shaped region along the Brahmaputra River. Climatic sensitivities of the glacier <span class="hlt">mass</span> balanceare also found to be closely linked to the regional precipitation seasonality that is simultaneously modulated by various atmospheric circulation patterns, such as the southern westerlies, the Bay of Bengal vortex in the spring season and the Indian monsoon in the summer</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25950136','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25950136"><span>Measuring air-water interfacial area for soils using the <span class="hlt">mass</span> <span class="hlt">balance</span> surfactant-tracer method.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Araujo, Juliana B; Mainhagu, Jon; Brusseau, Mark L</p> <p>2015-09-01</p> <p>There are several methods for conducting interfacial partitioning tracer tests to measure air-water interfacial area in porous media. One such approach is the <span class="hlt">mass</span> <span class="hlt">balance</span> surfactant tracer method. An advantage of the <span class="hlt">mass-balance</span> method compared to other tracer-based methods is that a single test can produce multiple interfacial area measurements over a wide range of water saturations. The <span class="hlt">mass-balance</span> method has been used to date only for glass beads or treated quartz sand. The purpose of this research is to investigate the effectiveness and implementability of the <span class="hlt">mass-balance</span> method for application to more complex porous media. The results indicate that interfacial areas measured with the <span class="hlt">mass-balance</span> method are consistent with values obtained with the miscible-displacement method. This includes results for a soil, for which solid-phase adsorption was a significant component of total tracer retention. Copyright © 2015 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C21H..01L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C21H..01L"><span><span class="hlt">Ice</span> sheet climate modeling: past achievements, ongoing challenges, and future endeavors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lenaerts, J.</p> <p>2017-12-01</p> <p>Fluctuations in surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) mask out a substantial portion of contemporary Greenland and Antarctic <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss. That implies that we need accurate, consistent, and long-term SMB time series to isolate the <span class="hlt">mass</span> loss signal. This in turn requires understanding of the processes driving SMB, and how they interplay. The primary controls on present-day <span class="hlt">ice</span> sheet SMB are snowfall, which is regulated by large-scale atmospheric variability, and surface meltwater production at the <span class="hlt">ice</span> sheet's edges, which is a complex result of atmosphere-surface interactions. Additionally, wind-driven snow redistribution and sublimation are large SMB contributors on the downslope areas of the <span class="hlt">ice</span> sheets. Climate models provide an integrated framework to simulate all these individual <span class="hlt">ice</span> sheet components. Recent developments in RACMO2, a regional climate model bound by atmospheric reanalyses, have focused on enhancing horizontal resolution, including blowing snow, snow albedo, and meltwater processes. Including these physics not only enhanced our understanding of the <span class="hlt">ice</span> sheet climate system, but also enabled to obtain increasingly accurate estimates of <span class="hlt">ice</span> sheet SMB. However, regional models are not suitable to capture the mutual interactions between <span class="hlt">ice</span> sheet and the remainder of the global climate system in transient climates. To take that next step, global climate models are essential. In this talk, I will highlight our present work on improving <span class="hlt">ice</span> sheet climate in the Community Earth System Model (CESM). In particular, we focus on an improved representation of polar firn, <span class="hlt">ice</span> sheet clouds, and precipitation. For this exercise, we extensively use field observations, remote sensing data, as well as RACMO2. Next, I will highlight how CESM is used to enhance our understanding of <span class="hlt">ice</span> sheet SMB, its drivers, and past and present changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.7488S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.7488S"><span>Integrated firn elevation change model for glaciers and <span class="hlt">ice</span> caps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saß, Björn; Sauter, Tobias; Braun, Matthias</p> <p>2016-04-01</p> <p>We present the development of a firn compaction model in order to improve the volume to <span class="hlt">mass</span> conversion of geodetic glacier <span class="hlt">mass</span> <span class="hlt">balance</span> measurements. The model is applied on the Arctic <span class="hlt">ice</span> cap Vestfonna. Vestfonna is located on the island Nordaustlandet in the north east of Svalbard. Vestfonna covers about 2400 km² and has a dome like shape with well-defined outlet glaciers. Elevation and volume changes measured by e.g. satellite techniques are becoming more and more popular. They are carried out over observation periods of variable length and often covering different meteorological and snow hydrological regimes. The elevation change measurements compose of various components including dynamic adjustments, firn compaction and <span class="hlt">mass</span> loss by downwasting. Currently, geodetic glacier <span class="hlt">mass</span> <span class="hlt">balances</span> are frequently converted from elevation change measurements using a constant conversion factor of 850 kg m-³ or the density of <span class="hlt">ice</span> (917 kg m-³) for entire glacier basins. However, the natural conditions are rarely that static. Other studies used constant densities for the ablation (900 kg m-³) and accumulation (600 kg m-³) areas, whereby density variations with varying meteorological and climate conditions are not considered. Hence, each approach bears additional uncertainties from the volume to <span class="hlt">mass</span> conversion that are strongly affected by the type and timing of the repeat measurements. We link and adapt existing models of surface energy <span class="hlt">balance</span>, accumulation and snow and firn processes in order to improve the volume to <span class="hlt">mass</span> conversion by considering the firn compaction component. Energy exchange at the surface is computed by a surface energy <span class="hlt">balance</span> approach and driven by meteorological variables like incoming short-wave radiation, air temperature, relative humidity, air pressure, wind speed, all-phase precipitation, and cloud cover fraction. Snow and firn processes are addressed by a coupled subsurface model, implemented with a non-equidistant layer discretisation. On</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDR13007H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDR13007H"><span><span class="hlt">Ice</span> sheets on plastically-yielding beds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hewitt, Ian</p> <p>2016-11-01</p> <p>Many fast flowing regions of <span class="hlt">ice</span> sheets are underlain by a layer of water-saturated sediments, or till. The rheology of the till has been the subject of some controversy, with laboratory tests suggesting almost perfectly plastic behaviour (stress independent of strain rate), but many models adopting a pseudo-viscous description. In this work, we consider the behaviour of glaciers underlain by a plastic bed. The <span class="hlt">ice</span> is treated as a viscous gravity current, on a bed that allows unconstrained slip above a critical yield stress. This simplified description allows rapid sliding, and aims to investigate 'worst-case' scenarios of possible <span class="hlt">ice</span>-sheet disintegration. The plastic bed results in an approximate <span class="hlt">ice</span>-sheet geometry that is primarily controlled by force <span class="hlt">balance</span>, whilst <span class="hlt">ice</span> velocity is determined from <span class="hlt">mass</span> conservation (rather than the other way around, as standard models would hold). The stability of various states is considered, and particular attention is given to the pace at which transitions between unstable states can occur. Finally, we observe that the strength of basal tills depends strongly on pore pressure, and combine the model with a description of subglacial hydrology. Implications for the present-day <span class="hlt">ice</span> sheets in Greenland and Antarctica will be discussed. Funding: ERC Marie Curie FP7 Career Integration Grant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C33E0863M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C33E0863M"><span>Hypsometric control on glacier <span class="hlt">mass</span> <span class="hlt">balance</span> sensitivity in Alaska</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McGrath, D.; Sass, L.; Arendt, A. A.; O'Neel, S.; Kienholz, C.; Larsen, C.; Burgess, E. W.</p> <p>2015-12-01</p> <p><span class="hlt">Mass</span> loss from glaciers in Alaska is dominated by strongly negative surface <span class="hlt">balances</span>, particularly on small, continental glaciers but can be highly variable from glacier to glacier. Glacier hypsometry can exert significant control on <span class="hlt">mass</span> <span class="hlt">balance</span> sensitivity, particularly if the equilibrium line altitude (ELA) is in a broad area of low surface slope. In this study, we explore the spatial variability in glacier response to future climate forcings on the basis of hypsometry. We first derive <span class="hlt">mass</span> <span class="hlt">balance</span> sensitivities (30-70 m ELA / 1° C and 40-90 m ELA / 50% decrease in snow accumulation) from the ~50-year USGS Benchmark glaciers <span class="hlt">mass</span> <span class="hlt">balance</span> record. We subsequently assess mean climate fields in 2090-2100 derived from the IPCC AR5/CMIP5 RCP 6.0 5-model mean. Over glaciers in Alaska, we find 2-4° C warming and 10-20% increase in precipitation relative to 2006-2015, but a corresponding 0-50% decrease in snow accumulation due to rising temperatures. We assess changes in accumulation area ratios (AAR) to a rising ELA using binned individual glacier hypsometries. For an ELA increase of 150 m, the mean statewide AAR drops by 0.45, representing a 70% reduction in accumulation area on an individual glacier basis. Small, interior glaciers are the primary drivers of this reduction and for nearly 25% of all glaciers, the new ELA exceeds the glacier's maximum elevation, portending eventual loss. The loss of small glaciers, particularly in the drier interior of Alaska will significantly modify streamflow properties (flashy hydrographs, earlier and reduced peak flows, increased interannual variability, warmer temperatures) with poorly understood downstream ecosystem and oceanographic impacts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.2621C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.2621C"><span>Retrieval of <span class="hlt">ice</span> crystals' <span class="hlt">mass</span> from <span class="hlt">ice</span> water content and particle distribution measurements: a numerical optimization approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coutris, Pierre; Leroy, Delphine; Fontaine, Emmanuel; Schwarzenboeck, Alfons; Strapp, J. Walter</p> <p>2016-04-01</p> <p>A new method to retrieve cloud water content from in-situ measured 2D particle images from optical array probes (OAP) is presented. With the overall objective to build a statistical model of crystals' <span class="hlt">mass</span> as a function of their size, environmental temperature and crystal microphysical history, this study presents the methodology to retrieve the <span class="hlt">mass</span> of crystals sorted by size from 2D images using a numerical optimization approach. The methodology is validated using two datasets of in-situ measurements gathered during two airborne field campaigns held in Darwin, Australia (2014), and Cayenne, France (2015), in the frame of the High Altitude <span class="hlt">Ice</span> Crystals (HAIC) / High <span class="hlt">Ice</span> Water Content (HIWC) projects. During these campaigns, a Falcon F-20 research aircraft equipped with state-of-the art microphysical instrumentation sampled numerous mesoscale convective systems (MCS) in order to study dynamical and microphysical properties and processes of high <span class="hlt">ice</span> water content areas. Experimentally, an isokinetic evaporator probe, referred to as IKP-2, provides a reference measurement of the total water content (TWC) which equals <span class="hlt">ice</span> water content, (IWC) when (supercooled) liquid water is absent. Two optical array probes, namely 2D-S and PIP, produce 2D images of individual crystals ranging from 50 μm to 12840 μm from which particle size distributions (PSD) are derived. Mathematically, the problem is formulated as an inverse problem in which the crystals' <span class="hlt">mass</span> is assumed constant over a size class and is computed for each size class from IWC and PSD data: PSD.m = IW C This problem is solved using numerical optimization technique in which an objective function is minimized. The objective function is defined as follows: 2 J(m)=∥P SD.m - IW C ∥ + λ.R (m) where the regularization parameter λ and the regularization function R(m) are tuned based on data characteristics. The method is implemented in two steps. First, the method is developed on synthetic crystal populations in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12.1367R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12.1367R"><span>Relative performance of empirical and physical models in assessing the seasonal and annual glacier surface <span class="hlt">mass</span> <span class="hlt">balance</span> of Saint-Sorlin Glacier (French Alps)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Réveillet, Marion; Six, Delphine; Vincent, Christian; Rabatel, Antoine; Dumont, Marie; Lafaysse, Matthieu; Morin, Samuel; Vionnet, Vincent; Litt, Maxime</p> <p>2018-04-01</p> <p>This study focuses on simulations of the seasonal and annual surface <span class="hlt">mass</span> <span class="hlt">balance</span> (SMB) of Saint-Sorlin Glacier (French Alps) for the period 1996-2015 using the detailed SURFEX/ISBA-Crocus snowpack model. The model is forced by SAFRAN meteorological reanalysis data, adjusted with automatic weather station (AWS) measurements to ensure that simulations of all the energy <span class="hlt">balance</span> components, in particular turbulent fluxes, are accurately represented with respect to the measured energy <span class="hlt">balance</span>. Results indicate good model performance for the simulation of summer SMB when using meteorological forcing adjusted with in situ measurements. Model performance however strongly decreases without in situ meteorological measurements. The sensitivity of the model to meteorological forcing indicates a strong sensitivity to wind speed, higher than the sensitivity to <span class="hlt">ice</span> albedo. Compared to an empirical approach, the model exhibited better performance for simulations of snow and firn melting in the accumulation area and similar performance in the ablation area when forced with meteorological data adjusted with nearby AWS measurements. When such measurements were not available close to the glacier, the empirical model performed better. Our results suggest that simulations of the evolution of future <span class="hlt">mass</span> <span class="hlt">balance</span> using an energy <span class="hlt">balance</span> model require very accurate meteorological data. Given the uncertainties in the temporal evolution of the relevant meteorological variables and glacier surface properties in the future, empirical approaches based on temperature and precipitation could be more appropriate for simulations of glaciers in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C23D..04M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C23D..04M"><span>Role of <span class="hlt">ice</span> sheet dynamics in the collapse of the early-Holocene Laurentide <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matero, I. S. O.; Gregoire, L. J.; Cornford, S. L.; Ivanovic, R. F.</p> <p>2017-12-01</p> <p>The last stage of the deglaciation of the Laurentide <span class="hlt">Ice</span> Sheet (LIS) during the early Holocene Thermal Maximum ( 9000 to 7000 years ago) provides an analogy and insight to the possible responses of contemporary <span class="hlt">ice</span> sheets in a warming climate. What makes LIS particularly interesting is that meltwater from the collapse of an <span class="hlt">ice</span> saddle over Hudson Bay was recently shown to be the primary forcing for the period of abrupt northern hemisphere cooling known as the 8.2 ka event. The evolution of the LIS during this period was likely influenced by its interaction with marginal lakes and the ocean, and its major <span class="hlt">ice</span> stream, which exported <span class="hlt">ice</span> towards Hudson Strait. Accurately simulating the early Holocene LIS evolution thus requires a model such as BISICLES, capable of accurately and efficiently resolving <span class="hlt">ice</span> stream dynamics and grounding line migration thanks to the combined use of higher order physics and adaptive mesh refinement. We drive the BISICLES model using a positive degree day <span class="hlt">mass</span> <span class="hlt">balance</span> scheme with monthly precipitation and temperature from the HadCM3 climate model under climatic conditions from 10,000 to 8,000 years ago. We test the effect of varying the initial topographies and <span class="hlt">ice</span> thicknesses from different timeslices in the <span class="hlt">ICE</span>-6Gc reconstruction. We also test different parameterisations for the basal friction based on the thicknesses of the underlying sediments. These simulations evaluate the role of the Hudson Strait <span class="hlt">ice</span> stream, <span class="hlt">ice</span> sheet dynamics and interactions with the adjacent proglacial Lake Agassiz and North Atlantic Ocean in the collapse of the LIS. Our results highlight that the choice of parameterisation for basal friction has major effects on <span class="hlt">ice</span> sheet dynamics and evolution.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ESASP.724...96F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ESASP.724...96F"><span>Improving the XAJ Model on the Basis of <span class="hlt">Mass</span>-Energy <span class="hlt">Balance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fang, Yuanhao; Corbari, Chiara; Zhang, Xingnan; Mancini, Marco</p> <p>2014-11-01</p> <p>Introduction: The Xin'anjiang(XAJ) model is a conceptual model developed by the group led by Prof. Ren-Jun Zhao, which takes the pan evaporation as one of its input and then computes the effective evapotranspiration (ET) of the catchment by <span class="hlt">mass</span> <span class="hlt">balance</span>. Such scheme can ensure a good performance of discharge simulation but has obvious defects, one of which is that the effective ET is spatially-constant over the computation unit, neglecting the spatial variation of variables that influence the effective ET and therefore the simulation of ET and SM by the XAJ model, comparing with discharge, is less reliable. In this study, The XAJ model was improved to employ both energy and <span class="hlt">mass</span> <span class="hlt">balance</span> to compute the ET following the energy-<span class="hlt">mass</span> <span class="hlt">balance</span> scheme of FEST-EWB. model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ESASP.724E..96F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ESASP.724E..96F"><span>Improving the XAJ Model on the Basis of <span class="hlt">Mass</span>-Energy <span class="hlt">Balance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fang, Yuanghao; Corbari, Chiara; Zhang, Xingnan; Mancini, Marco</p> <p>2014-11-01</p> <p>The Xin’anjiang(XAJ) model is a conceptual model developed by the group led by Prof. Ren-Jun Zhao, which takes the pan evaporation as one of its input and then computes the effective evapotranspiration (ET) of the catchment by <span class="hlt">mass</span> <span class="hlt">balance</span>. Such scheme can ensure a good performance of discharge simulation but has obvious defects, one of which is that the effective ET is spatially-constant over the computation unit, neglecting the spatial variation of variables that influence the effective ET and therefore the simulation of ET and SM by the XAJ model, comparing with discharge, is less reliable. In this study, The XAJ model was improved to employ both energy and <span class="hlt">mass</span> <span class="hlt">balance</span> to compute the ET following the energy-<span class="hlt">mass</span> <span class="hlt">balance</span> scheme of FEST-EWB. model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28681134','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28681134"><span>Effect of body <span class="hlt">mass</span> index and fat <span class="hlt">mass</span> on <span class="hlt">balance</span> force platform measurements during a one-legged stance in older adults.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pereira, Camila; Silva, Rubens A da; de Oliveira, Marcio R; Souza, Rejane D N; Borges, Renata J; Vieira, Edgar R</p> <p>2018-05-01</p> <p>The purpose of this study was to evaluate the impact of body <span class="hlt">mass</span> index (BMI) and fat <span class="hlt">mass</span> on <span class="hlt">balance</span> force platform measurements in older adults. The sample consisted of 257 participants who were stratified into four groups by BMI: low weight, normal weight, pre-obesity and obesity. For fat <span class="hlt">mass</span> variables, older individuals were classified into low and high-fat <span class="hlt">mass</span>. All groups investigated performed three trials of one-legged stance <span class="hlt">balance</span> on a force platform. Center of pressure (COP) domain parameters were computed from the mean across trials. Analysis of variance results revealed no significant interactions for groups and sexes for all COP parameters. Comparable <span class="hlt">balance</span> results were found for BMI and fat groups for all COP parameters. A statistical effect (P < 0.05) was only reported for sex differences for COP parameters, regardless of BMI and fat <span class="hlt">mass</span> variables. Overall, women presented better <span class="hlt">balance</span> than men. In conclusion, BMI and fat <span class="hlt">mass</span> do not seem to influence the <span class="hlt">balance</span> of older adults during a one-leg stance task.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/971305','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/971305"><span>The influence of air temperature inversions on snowmelt and glacier <span class="hlt">mass-balance</span> simulations, Ammassalik island, SE Greenland</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Mernild, Sebastian Haugard; Liston, Glen</p> <p>2009-01-01</p> <p>In many applications, a realistic description of air temperature inversions is essential for accurate snow and glacier <span class="hlt">ice</span> melt, and glacier <span class="hlt">mass-balance</span> simulations. A physically based snow-evolution modeling system (SnowModel) was used to simulate eight years (1998/99 to 2005/06) of snow accumulation and snow and glacier <span class="hlt">ice</span> ablation from numerous small coastal marginal glaciers on the SW-part of Ammassalik Island in SE Greenland. These glaciers are regularly influenced by inversions and sea breezes associated with the adjacent relatively low temperature and frequently <span class="hlt">ice</span>-choked fjords and ocean. To account for the influence of these inversions on the spatiotemporal variation of airmore » temperature and snow and glacier melt rates, temperature inversion routines were added to MircoMet, the meteorological distribution sub-model used in SnowModel. The inversions were observed and modeled to occur during 84% of the simulation period. Modeled inversions were defined not to occur during days with strong winds and high precipitation rates due to the potential of inversion break-up. Field observations showed inversions to extend from sea level to approximately 300 m a.s.l., and this inversion level was prescribed in the model simulations. Simulations with and without the inversion routines were compared. The inversion model produced air temperature distributions with warmer lower elevation areas and cooler higher elevation areas than without inversion routines due to the use of cold sea-breeze base temperature data from underneath the inversion. This yielded an up to 2 weeks earlier snowmelt in the lower areas and up to 1 to 3 weeks later snowmelt in the higher elevation areas of the simulation domain. Averaged mean annual modeled surface <span class="hlt">mass-balance</span> for all glaciers (mainly located above the inversion layer) was -720 {+-} 620 mm w.eq. y{sup -1} for inversion simulations, and -880 {+-} 620 mm w.eq. y{sup -1} without the inversion routines, a difference of 160 mm w</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1211533N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1211533N"><span>Role of <span class="hlt">ice</span>-ocean interaction on glacier instability: Results from numerical modelling applied to Petermann Glacier</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nick, Faezeh M.; Hubbard, Alun; van der Veen, Kees; Vieli, Andreas</p> <p>2010-05-01</p> <p>Calving of icebergs and bottom melting from <span class="hlt">ice</span> shelves accounts for roughly half the <span class="hlt">ice</span> transferred from the Greenland <span class="hlt">Ice</span> Sheet into the surrounding ocean, and virtually all of the <span class="hlt">ice</span> loss from the Antarctic <span class="hlt">Ice</span> Sheet. Petermann Glacier (north Greenland) with its 16 km wide and 80 km long floating tongue, experiences massive bottom melting. We apply a numerical <span class="hlt">ice</span> flow model using a physically-based calving criterion based on crevasse depth to investigate the contribution of processes such as bottom melting, sea <span class="hlt">ice</span> or sikkusak disintegration, surface run off and iceberg calving to the <span class="hlt">mass</span> <span class="hlt">balance</span> and instability of Petermann Glacier and its <span class="hlt">ice</span> shelf. Our modelling study provides insights into the role of <span class="hlt">ice</span>-ocean interaction, and on how to incorporate calving in <span class="hlt">ice</span> sheet models, improving our ability to predict future <span class="hlt">ice</span> sheet change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12..955C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12..955C"><span>Meltwater storage in low-density near-surface bare <span class="hlt">ice</span> in the Greenland <span class="hlt">ice</span> sheet ablation zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cooper, Matthew G.; Smith, Laurence C.; Rennermalm, Asa K.; Miège, Clément; Pitcher, Lincoln H.; Ryan, Jonathan C.; Yang, Kang; Cooley, Sarah W.</p> <p>2018-03-01</p> <p>We document the density and hydrologic properties of bare, ablating <span class="hlt">ice</span> in a mid-elevation (1215 m a.s.l.) supraglacial internally drained catchment in the Kangerlussuaq sector of the western Greenland <span class="hlt">ice</span> sheet. We find low-density (0.43-0.91 g cm-3, μ = 0.69 g cm-3) <span class="hlt">ice</span> to at least 1.1 m depth below the <span class="hlt">ice</span> sheet surface. This near-surface, low-density <span class="hlt">ice</span> consists of alternating layers of water-saturated, porous <span class="hlt">ice</span> and clear solid <span class="hlt">ice</span> lenses, overlain by a thin (< 0.5 m), even lower density (0.33-0.56 g cm-3, μ = 0.45 g cm-3) unsaturated weathering crust. <span class="hlt">Ice</span> density data from 10 shallow (0.9-1.1 m) <span class="hlt">ice</span> cores along an 800 m transect suggest an average 14-18 cm of specific meltwater storage within this low-density <span class="hlt">ice</span>. Water saturation of this <span class="hlt">ice</span> is confirmed through measurable water levels (1-29 cm above hole bottoms, μ = 10 cm) in 84 % of cryoconite holes and rapid refilling of 83 % of 1 m drilled holes sampled along the transect. These findings are consistent with descriptions of shallow, depth-limited aquifers on the weathered surface of glaciers worldwide and confirm the potential for substantial transient meltwater storage within porous low-density <span class="hlt">ice</span> on the Greenland <span class="hlt">ice</span> sheet ablation zone surface. A conservative estimate for the ˜ 63 km2 supraglacial catchment yields 0.009-0.012 km3 of liquid meltwater storage in near-surface, porous <span class="hlt">ice</span>. Further work is required to determine if these findings are representative of broader areas of the Greenland <span class="hlt">ice</span> sheet ablation zone, and to assess the implications for sub-seasonal <span class="hlt">mass</span> <span class="hlt">balance</span> processes, surface lowering observations from airborne and satellite altimetry, and supraglacial runoff processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940017861','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940017861"><span>Normalized vertical <span class="hlt">ice</span> <span class="hlt">mass</span> flux profiles from vertically pointing 8-mm-wavelength Doppler radar</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Orr, Brad W.; Kropfli, Robert A.</p> <p>1993-01-01</p> <p>During the FIRE 2 (First International Satellite Cloud Climatology Project Regional Experiment) project, NOAA's Wave Propagation Laboratory (WPL) operated its 8-mm wavelength Doppler radar extensively in the vertically pointing mode. This allowed for the calculation of a number of important cirrus cloud parameters, including cloud boundary statistics, cloud particle characteristic sizes and concentrations, and <span class="hlt">ice</span> <span class="hlt">mass</span> content (imc). The flux of imc, or, alternatively, <span class="hlt">ice</span> <span class="hlt">mass</span> flux (imf), is also an important parameter of a cirrus cloud system. <span class="hlt">Ice</span> <span class="hlt">mass</span> flux is important in the vertical redistribution of water substance and thus, in part, determines the cloud evolution. It is important for the development of cloud parameterizations to be able to define the essential physical characteristics of large populations of clouds in the simplest possible way. One method would be to normalize profiles of observed cloud properties, such as those mentioned above, in ways similar to those used in the convective boundary layer. The height then scales from 0.0 at cloud base to 1.0 at cloud top, and the measured cloud parameter scales by its maximum value so that all normalized profiles have 1.0 as their maximum value. The goal is that there will be a 'universal' shape to profiles of the normalized data. This idea was applied to estimates of imf calculated from data obtained by the WPL cloud radar during FIRE II. Other quantities such as median particle diameter, concentration, and <span class="hlt">ice</span> <span class="hlt">mass</span> content can also be estimated with this radar, and we expect to also examine normalized profiles of these quantities in time for the 1993 FIRE II meeting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.7246Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.7246Z"><span>Present-day dynamics and future evolution of the world's northernmost <span class="hlt">ice</span> cap, Hans Tausen Iskappe (Greenland)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zekollari, Harry; Huybrechts, Philippe; Noël, Brice; van de Berg, Willem Jan; van den Broeke, Michiel R.</p> <p>2017-04-01</p> <p>In this study the dynamics of Hans Tausen Iskappe (western Peary Land, Greenland) are investigated with a coupled <span class="hlt">ice</span> flow - <span class="hlt">mass</span> <span class="hlt">balance</span> model. Precipitation is obtained from the Regional Climate Model RACMO 2.3 and the surface <span class="hlt">mass</span> <span class="hlt">balance</span> is calculated from a Positive Degree-Day runoff/retention model, for which the input parameters are derived from field observations. For the <span class="hlt">ice</span> flow a 3-D higher-order thermo-mechanical model is used, which is run at a 250 m resolution. Under 1961-1990 climatic conditions a steady state <span class="hlt">ice</span> cap is obtained that is overall similar in geometry to the present-day <span class="hlt">ice</span> cap. <span class="hlt">Ice</span> thickness, temperature and flow velocity in the interior agree well with observations. For the outlet glaciers a reasonable agreement with temperature and <span class="hlt">ice</span> thickness measurements can only be obtained with an additional heat source related to infiltrating meltwater. The simulations indicate that the SMB-elevation feedback has a major effect on the <span class="hlt">ice</span> cap response time and stability. This causes the southern part of the <span class="hlt">ice</span> cap to be extremely sensitive to a change in climatic conditions and leads to thresholds in the <span class="hlt">ice</span> cap evolution. Under constant 2005-2014 climatic conditions the entire southern part of the <span class="hlt">ice</span> cap cannot be sustained and the <span class="hlt">ice</span> cap loses about 80% of its present-day volume. The future projected loss of surrounding permanent sea-<span class="hlt">ice</span> and corresponding potential sharp precipitation increase may however lead to an attenuation of the retreat and even potential stabilization of the <span class="hlt">ice</span> cap for a warming of up to 2-3°C. In a warmer and wetter climate the <span class="hlt">ice</span> margin will retreat while the interior is projected to grow, leading to a steeper <span class="hlt">ice</span> cap, in line with the present-day observed trends. For intermediate (+4°C) and high warming scenarios (+8°C) the <span class="hlt">ice</span> cap is projected to disappear respectively around 2400 and 2200 A.D., almost irrespective of the projected precipitation regime and the simulated present-day geometry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.9829W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.9829W"><span><span class="hlt">Mass</span> loss of the Greenland peripheral glaciers and <span class="hlt">ice</span> caps from satellite altimetry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wouters, Bert; Noël, Brice; Moholdt, Geir; Ligtenberg, Stefan; van den Broeke, Michiel</p> <p>2017-04-01</p> <p>At its rapidly warming margins, the Greenland <span class="hlt">Ice</span> Sheet is surrounded by (semi-)detached glaciers and <span class="hlt">ice</span> caps (GIC). Although they cover only roughly 5% of the total glaciated area in the region, they are estimated to account for 15-20% of the total sea level rise contribution of Greenland. The spatial and temporal evolution of the <span class="hlt">mass</span> changes of the peripheral GICs, however, remains poorly constrained. In this presentation, we use satellite altimetry from ICESat and Cryosat-2 combined with a high-resolution regional climate model to derive a 14 year time series (2003-2016) of regional elevation and <span class="hlt">mass</span> changes. The total <span class="hlt">mass</span> loss has been relatively constant during this period, but regionally, the GICs show marked temporal variations. Whereas thinning was concentrated along the eastern margin during 2003-2009, western GICs became the prime sea level rise contributors in recent years. <span class="hlt">Mass</span> loss in the northern region has been steadily increasing throughout the record, due to a strong atmospheric warning and a deterioration of the capacity of the firn layer to buffer the resulting melt water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.7015P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.7015P"><span>Application of terrestrial photogrammetry for the <span class="hlt">mass</span> <span class="hlt">balance</span> calculation on Montasio Occidentale Glacier (Julian Alps, Italy)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Piermattei, Livia; Carturan, Luca; Calligaro, Simone; Blasone, Giacomo; Guarnieri, Alberto; Tarolli, Paolo; Dalla Fontana, Giancarlo; Vettore, Antonio</p> <p>2014-05-01</p> <p>Digital elevation models (DEMs) of glaciated terrain are commonly used to measure changes in geometry and hence infer the <span class="hlt">mass</span> <span class="hlt">balance</span> of glaciers. Different tools and methods exist to obtain information about the 3D geometry of terrain. Recent improvements on the quality and performance of digital cameras for close-range photogrammetry, and the development of automatic digital photogrammetric processing makes the 'structure from motion' photogrammetric technique (SfM) competitive for high quality 3D models production, compared to efficient but also expensive and logistically-demanding survey technologies such as airborn and terrestrial laser scanner (TLS). The purpose of this work is to test the SfM approach, using a consumer-grade SLR camera and the low-cost computer vision-based software package Agisoft Photoscan (Agisoft LLC), to monitor the <span class="hlt">mass</span> <span class="hlt">balance</span> of Montasio Occidentale glacier, a 0.07km2, low-altitude, debris-covered glacier located in the Eastern Italian Alps. The quality of the 3D models produced by the SfM process has been assessed by comparison with digital terrain models obtained through TLS surveys carried out at the same dates. TLS technique has indeed proved to be very effective in determining the volume change of this glacier in the last years. Our results shows that the photogrammetric approach can produce point cloud densities comparable to those derived from TLS measurements. Furthermore, the horizontal and vertical accuracies are also of the same order of magnitude as for TLS (centimetric to decimetric). The effect of different landscape characteristics (e.g. distance from the camera or terrain gradient) and of different substrata (rock, debris, <span class="hlt">ice</span>, snow and firn) was also evaluated in terms of SfM reconstruction's accuracy vs. TLS. Given the good results obtained on the Montasio Occidentale glacier, it can be concluded that the terrestrial photogrammetry, with the advantageous features of portability, ease of use and above all low costs</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3180931','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3180931"><span><span class="hlt">Mass</span> <span class="hlt">Balance</span> Analysis of Contaminated Heparin Product</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Liu, Zhenling; Xiao, Zhongping; Masuko, Sayaka; Zhao, Wenjing; Sterner, Eric; Bansal, Vinod; Fareed, Jawed; Dordick, Jonathan; Zhang, Fuming; Linhardt, Robert J.</p> <p>2011-01-01</p> <p>A quantitative analysis of a recalled contaminated lot of heparin (HP) sodium injection United States Pharmacopeial (USP) was undertaken in response to the controversy regarding the exact nature of the contaminant involved in the HP crisis. A <span class="hlt">mass</span> <span class="hlt">balance</span> analysis of the formulated drug product was performed. After freeze-drying, a 1 ml vial for injection afforded 54.8 ± 0.3 mg of dry solids. The excipients, sodium chloride and residual benzyl alcohol, accounted for 11.4 ± 0.5 mg and 0.9 ± 0.5 mg, respectively. Active pharmaceutical ingredient (API) represented 41.5 ± 1.0 mg, corresponding to 75.7 wt% of dry <span class="hlt">mass</span>. Exhaustive treatment of API with specific enzymes, heparin lyases and/or chondroitin lyases was used to close <span class="hlt">mass</span> <span class="hlt">balance</span>. HP represented 30.5 ± 0.5 mg, corresponding to 73.5 wt% of the API. Dermatan sulfate (DS) impurity represented 1.7 ± 0.3 mg, corresponding to 4.1 wt% of the API. Contaminant, 9.3 ± 0.1 mg corresponding to 22.4 wt% of API, was found in the contaminated formulated drug product. The recovery of contaminant was close to quantitative (95.6-100 wt%). A single contaminant was unambiguously identified as oversulfated chondroitin sulfate (OSCS). PMID:20850409</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018QSRv..189....1M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018QSRv..189....1M"><span>Reconciling records of <span class="hlt">ice</span> streaming and <span class="hlt">ice</span> margin retreat to produce a palaeogeographic reconstruction of the deglaciation of the Laurentide <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Margold, Martin; Stokes, Chris R.; Clark, Chris D.</p> <p>2018-06-01</p> <p>This paper reconstructs the deglaciation of the Laurentide <span class="hlt">Ice</span> Sheet (LIS; including the Innuitian <span class="hlt">Ice</span> Sheet) from the Last Glacial Maximum (LGM), with a particular focus on the spatial and temporal variations in <span class="hlt">ice</span> streaming and the associated changes in flow patterns and <span class="hlt">ice</span> divides. We build on a recent inventory of Laurentide <span class="hlt">ice</span> streams and use an existing <span class="hlt">ice</span> margin chronology to produce the first detailed transient reconstruction of the <span class="hlt">ice</span> stream drainage network in the LIS, which we depict in a series of palaeogeographic maps. Results show that the drainage network at the LGM was similar to modern-day Antarctica. The majority of the <span class="hlt">ice</span> streams were marine terminating and topographically-controlled and many of these continued to function late into the deglaciation, until the <span class="hlt">ice</span> sheet lost its marine margin. <span class="hlt">Ice</span> streams with a terrestrial <span class="hlt">ice</span> margin in the west and south were more transient and <span class="hlt">ice</span> flow directions changed with the build-up, peak-phase and collapse of the Cordilleran-Laurentide <span class="hlt">ice</span> saddle. The south-eastern marine margin in Atlantic Canada started to retreat relatively early and some of the <span class="hlt">ice</span> streams in this region switched off at or shortly after the LGM. In contrast, the <span class="hlt">ice</span> streams draining towards the north-western and north-eastern marine margins in the Beaufort Sea and in Baffin Bay appear to have remained stable throughout most of the Late Glacial, and some of them continued to function until after the Younger Dryas (YD). The YD influenced the dynamics of the deglaciation, but there remains uncertainty about the response of the <span class="hlt">ice</span> sheet in several sectors. We tentatively ascribe the switching-on of some major <span class="hlt">ice</span> streams during this period (e.g. M'Clintock Channel <span class="hlt">Ice</span> Stream at the north-west margin), but for other large <span class="hlt">ice</span> streams whose timing partially overlaps with the YD, the drivers are less clear and <span class="hlt">ice</span>-dynamical processes, rather than effects of climate and surface <span class="hlt">mass</span> <span class="hlt">balance</span> are viewed as more likely drivers. Retreat</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C41B0664M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C41B0664M"><span>Oceanographic Influences on <span class="hlt">Ice</span> Shelves and Drainage in the Amundsen Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Minzoni, R. T.; Anderson, J. B.; Majewski, W.; Yokoyama, Y.; Fernandez, R.; Jakobsson, M.</p> <p>2016-12-01</p> <p> that contribute to the <span class="hlt">mass</span> <span class="hlt">balance</span> of the West Antarctic <span class="hlt">Ice</span> Sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.B21F..01H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.B21F..01H"><span>Pedogenesis on <span class="hlt">ice</span> (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hodson, A. J.</p> <p>2010-12-01</p> <p>It is well known from <span class="hlt">ice</span> cores that organic and mineral debris accumulates within glacier <span class="hlt">ice</span> following atmospheric deposition. However, the concentrations of such debris are usually greatest upon the <span class="hlt">ice</span> surface, especially at the margins of continental glaciers and <span class="hlt">ice</span> sheets, where it forms mm-scale aggregate particles called “cryoconite”. According to the literature, cryoconite covers about 2 % of the ablation areas of glaciers outside Greenland and Antarctica, equivalent to a <span class="hlt">mass</span> loading of ca. 25 g/m2. Of the great <span class="hlt">ice</span> sheets not included in this figure, Greenland is the easiest to estimate, and new observations from the NE and SW sectors indicate <span class="hlt">mass</span> loadings in the range 17 - 440 g/m2. Studies of cryoconite often report the presence of a significant biomass (usually 10^4 - 10^7 cells/g) that is capable of a wide range of biogeochemical functions. The first part of this presentation will therefore explore the contention that the formation of cryoconite represents the first stages of pedogenesis, resulting in the production of soil-type aggregates that inoculate glacial forefields following glacier retreat. Emphasis will be given to the relevant processes that result in aggregate formation, including rapid cell-mineral attachment within melting snowpacks and the slower, biological processes of cementation within thermodynamically stable habitats such as cryoconite holes. The second part of the presentation will use examples from Svalbard, Greenland and Antarctica to consider the carbon <span class="hlt">balance</span> of the cryoconite during the longest phase of its life cycle: upon the <span class="hlt">ice</span>. It will be demonstrated how the efficacy of photosynthesis is strongly influenced by thermodynamic conditions at or near this surface. Data from the Greenland and Antarctic <span class="hlt">ice</span> sheets will show how thermal equilibration decouples variations in photosynthesis from variations in incident radiation over timescales > 1 d, resulting in an equitable, low-carbon economy for aggregates within</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110007903','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110007903"><span>Mixed Phase Modeling in Glenn<span class="hlt">ICE</span> with Application to Engine <span class="hlt">Icing</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wright, William B.; Jorgenson, Philip C. E.; Veres, Joseph P.</p> <p>2011-01-01</p> <p>A capability for modeling <span class="hlt">ice</span> crystals and mixed phase <span class="hlt">icing</span> has been added to Glenn<span class="hlt">ICE</span>. Modifications have been made to the particle trajectory algorithm and energy <span class="hlt">balance</span> to model this behavior. This capability has been added as part of a larger effort to model <span class="hlt">ice</span> crystal ingestion in aircraft engines. Comparisons have been made to four mixed phase <span class="hlt">ice</span> accretions performed in the Cox <span class="hlt">icing</span> tunnel in order to calibrate an <span class="hlt">ice</span> erosion model. A sample <span class="hlt">ice</span> ingestion case was performed using the Energy Efficient Engine (E3) model in order to illustrate current capabilities. Engine performance characteristics were supplied using the Numerical Propulsion System Simulation (NPSS) model for this test case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3761614','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3761614"><span>Enhanced basal lubrication and the contribution of the Greenland <span class="hlt">ice</span> sheet to future sea-level rise</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Shannon, Sarah R.; Payne, Antony J.; Bartholomew, Ian D.; van den Broeke, Michiel R.; Edwards, Tamsin L.; Fettweis, Xavier; Gagliardini, Olivier; Gillet-Chaulet, Fabien; Goelzer, Heiko; Hoffman, Matthew J.; Huybrechts, Philippe; Mair, Douglas W. F.; Nienow, Peter W.; Perego, Mauro; Price, Stephen F.; Smeets, C. J. P. Paul; Sole, Andrew J.; van de Wal, Roderik S. W.; Zwinger, Thomas</p> <p>2013-01-01</p> <p>We assess the effect of enhanced basal sliding on the flow and <span class="hlt">mass</span> budget of the Greenland <span class="hlt">ice</span> sheet, using a newly developed parameterization of the relation between meltwater runoff and <span class="hlt">ice</span> flow. A wide range of observations suggest that water generated by melt at the surface of the <span class="hlt">ice</span> sheet reaches its bed by both fracture and drainage through moulins. Once at the bed, this water is likely to affect lubrication, although current observations are insufficient to determine whether changes in subglacial hydraulics will limit the potential for the speedup of flow. An uncertainty analysis based on our best-fit parameterization admits both possibilities: continuously increasing or bounded lubrication. We apply the parameterization to four higher-order <span class="hlt">ice</span>-sheet models in a series of experiments forced by changes in both lubrication and surface <span class="hlt">mass</span> budget and determine the additional <span class="hlt">mass</span> loss brought about by lubrication in comparison with experiments forced only by changes in surface <span class="hlt">mass</span> <span class="hlt">balance</span>. We use forcing from a regional climate model, itself forced by output from the European Centre Hamburg Model (ECHAM5) global climate model run under scenario A1B. Although changes in lubrication generate widespread effects on the flow and form of the <span class="hlt">ice</span> sheet, they do not affect substantial net <span class="hlt">mass</span> loss; increase in the <span class="hlt">ice</span> sheet’s contribution to sea-level rise from basal lubrication is projected by all models to be no more than 5% of the contribution from surface <span class="hlt">mass</span> budget forcing alone. PMID:23940337</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23940337','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23940337"><span>Enhanced basal lubrication and the contribution of the Greenland <span class="hlt">ice</span> sheet to future sea-level rise.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shannon, Sarah R; Payne, Antony J; Bartholomew, Ian D; van den Broeke, Michiel R; Edwards, Tamsin L; Fettweis, Xavier; Gagliardini, Olivier; Gillet-Chaulet, Fabien; Goelzer, Heiko; Hoffman, Matthew J; Huybrechts, Philippe; Mair, Douglas W F; Nienow, Peter W; Perego, Mauro; Price, Stephen F; Smeets, C J P Paul; Sole, Andrew J; van de Wal, Roderik S W; Zwinger, Thomas</p> <p>2013-08-27</p> <p>We assess the effect of enhanced basal sliding on the flow and <span class="hlt">mass</span> budget of the Greenland <span class="hlt">ice</span> sheet, using a newly developed parameterization of the relation between meltwater runoff and <span class="hlt">ice</span> flow. A wide range of observations suggest that water generated by melt at the surface of the <span class="hlt">ice</span> sheet reaches its bed by both fracture and drainage through moulins. Once at the bed, this water is likely to affect lubrication, although current observations are insufficient to determine whether changes in subglacial hydraulics will limit the potential for the speedup of flow. An uncertainty analysis based on our best-fit parameterization admits both possibilities: continuously increasing or bounded lubrication. We apply the parameterization to four higher-order <span class="hlt">ice</span>-sheet models in a series of experiments forced by changes in both lubrication and surface <span class="hlt">mass</span> budget and determine the additional <span class="hlt">mass</span> loss brought about by lubrication in comparison with experiments forced only by changes in surface <span class="hlt">mass</span> <span class="hlt">balance</span>. We use forcing from a regional climate model, itself forced by output from the European Centre Hamburg Model (ECHAM5) global climate model run under scenario A1B. Although changes in lubrication generate widespread effects on the flow and form of the <span class="hlt">ice</span> sheet, they do not affect substantial net <span class="hlt">mass</span> loss; increase in the <span class="hlt">ice</span> sheet's contribution to sea-level rise from basal lubrication is projected by all models to be no more than 5% of the contribution from surface <span class="hlt">mass</span> budget forcing alone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22525155-distinguishing-neutrino-mass-hierarchies-using-dark-matter-annihilation-signals-icecube','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22525155-distinguishing-neutrino-mass-hierarchies-using-dark-matter-annihilation-signals-icecube"><span>Distinguishing neutrino <span class="hlt">mass</span> hierarchies using dark matter annihilation signals at <span class="hlt">Ice</span>Cube</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Allahverdi, Rouzbeh; Knockel, Bradley; Dutta, Bhaskar</p> <p>2015-12-01</p> <p>We explore the possibility of distinguishing neutrino <span class="hlt">mass</span> hierarchies through the neutrino signal from dark matter annihilation at neutrino telescopes. We consider a simple extension of the standard model where the neutrino <span class="hlt">masses</span> and mixing angles are obtained via the type-II seesaw mechanism as an explicit example. We show that future extensions of <span class="hlt">Ice</span>Cube neutrino telescope may detect the neutrino signal from DM annihilation at the Galactic Center and inside the Sun, and differentiate between the normal and inverted <span class="hlt">mass</span> hierarchies, in this model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813272G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813272G"><span>ISMIP6 - initMIP: Greenland <span class="hlt">ice</span> sheet model initialisation experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goelzer, Heiko; Nowicki, Sophie; Payne, Tony; Larour, Eric; Abe Ouchi, Ayako; Gregory, Jonathan; Lipscomb, William; Seroussi, Helene; Shepherd, Andrew; Edwards, Tamsin</p> <p>2016-04-01</p> <p>Earlier large-scale Greenland <span class="hlt">ice</span> sheet sea-level projections e.g. those run during <span class="hlt">ice</span>2sea and SeaRISE initiatives have shown that <span class="hlt">ice</span> sheet initialisation can have a large effect on the projections and gives rise to important uncertainties. This intercomparison exercise (initMIP) aims at comparing, evaluating and improving the initialization techniques used in the <span class="hlt">ice</span> sheet modeling community and to estimate the associated uncertainties. It is the first in a series of <span class="hlt">ice</span> sheet model intercomparison activities within ISMIP6 (<span class="hlt">Ice</span> Sheet Model Intercomparison Project for CMIP6). The experiments are conceived for the large-scale Greenland <span class="hlt">ice</span> sheet and are designed to allow intercomparison between participating models of 1) the initial present-day state of the <span class="hlt">ice</span> sheet and 2) the response in two schematic forward experiments. The latter experiments serve to evaluate the initialisation in terms of model drift (forward run without any forcing) and response to a large perturbation (prescribed surface <span class="hlt">mass</span> <span class="hlt">balance</span> anomaly). We present and discuss first results of the intercomparison and highlight important uncertainties with respect to projections of the Greenland <span class="hlt">ice</span> sheet sea-level contribution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ISPAr42.3.2625L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ISPAr42.3.2625L"><span>Compiling Techniques for East Antarctic <span class="hlt">Ice</span> Velocity Mapping Based on Historical Optical Imagery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, X.; Li, R.; Qiao, G.; Cheng, Y.; Ye, W.; Gao, T.; Huang, Y.; Tian, Y.; Tong, X.</p> <p>2018-05-01</p> <p><span class="hlt">Ice</span> flow velocity over long time series in East Antarctica plays a vital role in estimating and predicting the <span class="hlt">mass</span> <span class="hlt">balance</span> of Antarctic <span class="hlt">Ice</span> Sheet and its contribution to global sea level rise. However, there is no Antarctic <span class="hlt">ice</span> velocity product with large space scale available showing the East Antarctic <span class="hlt">ice</span> flow velocity pattern before the 1990s. We proposed three methods including parallax decomposition, grid-based NCC image matching, feature and gird-based image matching with constraints for estimation of surface velocity in East Antarctica based on ARGON KH-5 and LANDSAT imagery, showing the feasibility of using historical optical imagery to obtain Antarctic <span class="hlt">ice</span> motion. Based on these previous studies, we presented a set of systematic method for developing <span class="hlt">ice</span> surface velocity product for the entire East Antarctica from the 1960s to the 1980s in this paper.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009GeoJI.176...95S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009GeoJI.176...95S"><span>Estimating the rates of <span class="hlt">mass</span> change, <span class="hlt">ice</span> volume change and snow volume change in Greenland from ICESat and GRACE data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Slobbe, D. C.; Ditmar, P.; Lindenbergh, R. C.</p> <p>2009-01-01</p> <p>The focus of this paper is on the quantification of ongoing <span class="hlt">mass</span> and volume changes over the Greenland <span class="hlt">ice</span> sheet. For that purpose, we used elevation changes derived from the <span class="hlt">Ice</span>, Cloud, and land Elevation Satellite (ICESat) laser altimetry mission and monthly variations of the Earth's gravity field as observed by the Gravity Recovery and Climate Experiment (GRACE) mission. Based on a stand alone processing scheme of ICESat data, the most probable estimate of the <span class="hlt">mass</span> change rate from 2003 February to 2007 April equals -139 +/- 68 Gtonyr-1. Here, we used a density of 600+/-300 kgm-3 to convert the estimated elevation change rate in the region above 2000m into a <span class="hlt">mass</span> change rate. For the region below 2000m, we used a density of 900+/-300 kgm-3. Based on GRACE gravity models from half 2002 to half 2007 as processed by CNES, CSR, DEOS and GFZ, the estimated <span class="hlt">mass</span> change rate for the whole of Greenland ranges between -128 and -218Gtonyr-1. Most GRACE solutions show much stronger <span class="hlt">mass</span> losses as obtained with ICESat, which might be related to a local undersampling of the <span class="hlt">mass</span> loss by ICESat and uncertainties in the used snow/<span class="hlt">ice</span> densities. To solve the problem of uncertainties in the snow and <span class="hlt">ice</span> densities, two independent joint inversion concepts are proposed to profit from both GRACE and ICESat observations simultaneously. The first concept, developed to reduce the uncertainty of the <span class="hlt">mass</span> change rate, estimates this rate in combination with an effective snow/<span class="hlt">ice</span> density. However, it turns out that the uncertainties are not reduced, which is probably caused by the unrealistic assumption that the effective density is constant in space and time. The second concept is designed to convert GRACE and ICESat data into two totally new products: variations of <span class="hlt">ice</span> volume and variations of snow volume separately. Such an approach is expected to lead to new insights in ongoing <span class="hlt">mass</span> change processes over the Greenland <span class="hlt">ice</span> sheet. Our results show for different GRACE solutions a snow</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015TCD.....9.5097V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015TCD.....9.5097V"><span>The modelled surface <span class="hlt">mass</span> <span class="hlt">balance</span> of the Antarctic Peninsula at 5.5 km horizontal resolution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van Wessem, J. M.; Ligtenberg, S. R. M.; Reijmer, C. H.; van de Berg, W. J.; van den Broeke, M. R.; Barrand, N. E.; Thomas, E. R.; Turner, J.; Wuite, J.; Scambos, T. A.; van Meijgaard, E.</p> <p>2015-09-01</p> <p>This study presents a high-resolution (~ 5.5 km) estimate of Surface <span class="hlt">Mass</span> <span class="hlt">Balance</span> (SMB) over the period 1979-2014 for the Antarctic Peninsula (AP), generated by the regional atmospheric climate model RACMO2.3 and a Firn Densification Model (FDM). RACMO2.3 is used to force the FDM, which calculates processes in the snowpack, such as meltwater percolation, refreezing and runoff. We evaluate model output with 132 in-situ SMB observations and discharge rates from 6 glacier drainage basins, and find that the model realistically simulates the strong spatial variability in precipitation, but that significant biases remain as a result of the highly complex topography of the AP. It is also clear that the observations significantly underrepresent the high-accumulation regimes. The SMB map reveals large accumulation gradients, with precipitation values above 3000 mm we yr-1 over the western AP (WAP) and below 500 mm we yr-1 on the eastern AP (EAP), not resolved by coarser data-sets such as ERA-Interim. The other SMB components are one order of magnitude smaller, with drifting snow sublimation the largest ablation term removing up to 100 mm we yr-1 of <span class="hlt">mass</span>. Snowmelt is widespread over the AP, reaching 500 mm we yr-1 towards the northern <span class="hlt">ice</span> shelves, but the meltwater mostly refreezes. As a result runoff fluxes are low, but still considerable (200 mm we yr-1) over the Larsen (B/C), Wilkins and George VI <span class="hlt">ice</span> shelves. The average AP <span class="hlt">ice</span> sheet integrated SMB, including <span class="hlt">ice</span> shelves (an area of 4.1 × 105 km2), is estimated at 351 Gt yr-1 with an interannual variability of 58 Gt yr-1, which is dominated by precipitation (PR) (365 ± 57 Gt yr-1). The WAP (2.4 × 105 km2) SMB (276 ± 47 Gt yr-1), where PR is large (276 ± 47 Gt yr-1), dominates over the EAP (1.7 × 105 km2) SMB (75 ± 11 Gt yr-1) and PR (84 ± 11 Gt yr-1). Total sublimation is 11 ± 2 Gt yr-1 and meltwater runoff into the ocean is 4 ± 4 Gt yr-1. There are no significant trends in any of the AP SMB components, except</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.1481D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.1481D"><span>Limited Impact of Subglacial Supercooling Freeze-on for Greenland <span class="hlt">Ice</span> Sheet Stratigraphy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dow, Christine F.; Karlsson, Nanna B.; Werder, Mauro A.</p> <p>2018-02-01</p> <p>Large units of disrupted radiostratigraphy (UDR) are visible in many radio-echo sounding data sets from the Greenland <span class="hlt">Ice</span> Sheet. This study investigates whether supercooling freeze-on rates at the bed can cause the observed UDR. We use a subglacial hydrology model to calculate both freezing and melting rates at the base of the <span class="hlt">ice</span> sheet in a distributed sheet and within basal channels. We find that while supercooling freeze-on is a phenomenon that occurs in many areas of the <span class="hlt">ice</span> sheet, there is no discernible correlation with the occurrence of UDR. The supercooling freeze-on rates are so low that it would require tens of thousands of years with minimal downstream <span class="hlt">ice</span> motion to form the hundreds of meters of disrupted radiostratigraphy. Overall, the melt rates at the base of the <span class="hlt">ice</span> sheet greatly overwhelm the freeze-on rates, which has implications for <span class="hlt">mass</span> <span class="hlt">balance</span> calculations of Greenland <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRC..123.1156R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRC..123.1156R"><span>Thin Sea <span class="hlt">Ice</span>, Thick Snow, and Widespread Negative Freeboard Observed During N-<span class="hlt">ICE</span>2015 North of Svalbard</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rösel, Anja; Itkin, Polona; King, Jennifer; Divine, Dmitry; Wang, Caixin; Granskog, Mats A.; Krumpen, Thomas; Gerland, Sebastian</p> <p>2018-02-01</p> <p>In recent years, sea-<span class="hlt">ice</span> conditions in the Arctic Ocean changed substantially toward a younger and thinner sea-<span class="hlt">ice</span> cover. To capture the scope of these changes and identify the differences between individual regions, in situ observations from expeditions are a valuable data source. We present a continuous time series of in situ measurements from the N-<span class="hlt">ICE</span>2015 expedition from January to June 2015 in the Arctic Basin north of Svalbard, comprising snow buoy and <span class="hlt">ice</span> <span class="hlt">mass</span> <span class="hlt">balance</span> buoy data and local and regional data gained from electromagnetic induction (EM) surveys and snow probe measurements from four distinct drifts. The observed mean snow depth of 0.53 m for April to early June is 73% above the average value of 0.30 m from historical and recent observations in this region, covering the years 1955-2017. The modal total <span class="hlt">ice</span> and snow thicknesses, of 1.6 and 1.7 m measured with ground-based EM and airborne EM measurements in April, May, and June 2015, respectively, lie below the values ranging from 1.8 to 2.7 m, reported in historical observations from the same region and time of year. The thick snow cover slows thermodynamic growth of the underlying sea <span class="hlt">ice</span>. In combination with a thin sea-<span class="hlt">ice</span> cover this leads to an imbalance between snow and <span class="hlt">ice</span> thickness, which causes widespread negative freeboard with subsequent flooding and a potential for snow-<span class="hlt">ice</span> formation. With certainty, 29% of randomly located drill holes on level <span class="hlt">ice</span> had negative freeboard.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.C31F..07N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.C31F..07N"><span>Role of <span class="hlt">ice</span>-ocean interaction on glacier instability: Results from numerical modeling applied to Petermann Glacier (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nick, F.; Hubbard, A.; Vieli, A.; van der Veen, C. J.; Box, J. E.; Bates, R.; Luckman, A. J.</p> <p>2009-12-01</p> <p>Calving of icebergs and bottom melting from <span class="hlt">ice</span> shelves accounts for roughly half the <span class="hlt">ice</span> transferred from the Greenland <span class="hlt">Ice</span> Sheet into the surrounding ocean, and virtually all of the <span class="hlt">ice</span> loss from the Antarctic <span class="hlt">Ice</span> Sheet. Petermann Glacier (north Greenland) with its 16 km wide and 80 km long floating tongue, experiences massive bottom melting. We apply a numerical <span class="hlt">ice</span> flow model using a physically-based calving criterion based on crevasse depth to investigate the contribution of processes such as bottom melting, sea <span class="hlt">ice</span> or sikkusak disintegration, surface run off and iceberg calving to the <span class="hlt">mass</span> <span class="hlt">balance</span> and instability of Petermann Glacier and its <span class="hlt">ice</span> shelf. Our modeling study provides insights into the role of <span class="hlt">ice</span>-ocean interaction, and on how to incorporate calving in <span class="hlt">ice</span> sheet models, improving our ability to predict future <span class="hlt">ice</span> sheet change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813180M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813180M"><span>Constraining East Antarctic <span class="hlt">mass</span> trends using a Bayesian inference approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martin-Español, Alba; Bamber, Jonathan L.</p> <p>2016-04-01</p> <p>East Antarctica is an order of magnitude larger than its western neighbour and the Greenland <span class="hlt">ice</span> sheet. It has the greatest potential to contribute to sea level rise of any source, including non-glacial contributors. It is, however, the most challenging <span class="hlt">ice</span> <span class="hlt">mass</span> to constrain because of a range of factors including the relative paucity of in-situ observations and the poor signal to noise ratio of Earth Observation data such as satellite altimetry and gravimetry. A recent study using satellite radar and laser altimetry (Zwally et al. 2015) concluded that the East Antarctic <span class="hlt">Ice</span> Sheet (EAIS) had been accumulating <span class="hlt">mass</span> at a rate of 136±28 Gt/yr for the period 2003-08. Here, we use a Bayesian hierarchical model, which has been tested on, and applied to, the whole of Antarctica, to investigate the impact of different assumptions regarding the origin of elevation changes of the EAIS. We combined GRACE, satellite laser and radar altimeter data and GPS measurements to solve simultaneously for surface processes (primarily surface <span class="hlt">mass</span> <span class="hlt">balance</span>, SMB), <span class="hlt">ice</span> dynamics and glacio-isostatic adjustment over the period 2003-13. The hierarchical model partitions <span class="hlt">mass</span> trends between SMB and <span class="hlt">ice</span> dynamics based on physical principles and measures of statistical likelihood. Without imposing the division between these processes, the model apportions about a third of the <span class="hlt">mass</span> trend to <span class="hlt">ice</span> dynamics, +18 Gt/yr, and two thirds, +39 Gt/yr, to SMB. The total <span class="hlt">mass</span> trend for that period for the EAIS was 57±20 Gt/yr. Over the period 2003-08, we obtain an <span class="hlt">ice</span> dynamic trend of 12 Gt/yr and a SMB trend of 15 Gt/yr, with a total <span class="hlt">mass</span> trend of 27 Gt/yr. We then imposed the condition that the surface <span class="hlt">mass</span> <span class="hlt">balance</span> is tightly constrained by the regional climate model RACMO2.3 and allowed height changes due to <span class="hlt">ice</span> dynamics to occur in areas of low surface velocities (<10 m/yr) , such as those in the interior of East Antarctica (a similar condition as used in Zwally 2015). The model must find a solution that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PhyEd..39..289N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PhyEd..39..289N"><span>When equal <span class="hlt">masses</span> don't <span class="hlt">balance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Newburgh, Ronald; Peidle, Joseph; Rueckner, Wolfgang</p> <p>2004-05-01</p> <p>We treat a modified Atwood's machine in which equal <span class="hlt">masses</span> do not <span class="hlt">balance</span> because of being in an accelerated frame of reference. Analysis of the problem illuminates the meaning of inertial forces, d'Alembert's principle, the use of free-body diagrams and the selection of appropriate systems for the diagrams. In spite of the range of these applications the analysis does not require calculus, so the ideas are accessible even to first-year students.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1911454C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1911454C"><span>Remote Sensing based modelling of Annual Surface <span class="hlt">Mass</span> <span class="hlt">Balances</span> of Chhota Shigiri Glacier, Western Himalayas, India</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chandrasekharan, Anita; Ramsankaran, Raaj</p> <p>2017-04-01</p> <p>The current study aims at modelling glacier <span class="hlt">mass</span> <span class="hlt">balances</span> over Chhota Shigiri glacier (32.28o N; 77.58° E) in Himachal Pradesh, India using the Equilibrium Line Altitude (ELA) gradient approach proposed by Rabatel et al. (2005). The model requires yearly ELA, average <span class="hlt">mass</span> <span class="hlt">balance</span> and <span class="hlt">mass</span> <span class="hlt">balance</span> gradient to estimate annual <span class="hlt">mass</span> <span class="hlt">balance</span> of a glacier which can be obtained either through field measurements or remote sensing observations. However, in view of the general scenario of lack of field data for Himalayan glaciers, in this study the model has been applied only using the inputs derived through multi-temporal satellite remote sensing observations thus eliminating the need for any field measurements. Preliminary analysis show that the obtained results are comparable with the observed field <span class="hlt">mass</span> <span class="hlt">balance</span>. The results also demonstrate that this approach with remote sensing inputs has potential to be used for glacier <span class="hlt">mass</span> <span class="hlt">balance</span> estimations provided good quality multi-temporal remote sensing dataset are available.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=80175&Lab=NHEERL&keyword=enviromental&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=80175&Lab=NHEERL&keyword=enviromental&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>A <span class="hlt">MASS</span> <span class="hlt">BALANCE</span> OF SURFACE WATER GENOTOXICITY IN PROVIDENCE RIVER (RHODE ISLAND USA)</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>White and Rasmussen (Mutation Res. 410:223-236) used a <span class="hlt">mass</span> <span class="hlt">balance</span> approach to demonstrate that over 85% of the total genotoxic loading to the St. Lawrence River at Montreal is non-industrial. To validate the <span class="hlt">mass</span> <span class="hlt">balance</span> approach and investigate the sources of genotoxins in sur...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150001270','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150001270"><span>Antarctica, Greenland and Gulf of Alaska Land-<span class="hlt">ice</span> Evolution from an Iterated GRACE Global Mascon Solution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Luthcke, Scott B.; Sabaka, T. J.; Loomis, B. D.; Arendt, A. A.; McCarthy, J. J.; Camp, J.</p> <p>2013-01-01</p> <p>We have determined the <span class="hlt">ice</span> <span class="hlt">mass</span> evolution of the Antarctica and Greenland <span class="hlt">ice</span> sheets (AIS and GIS) and Gulf of Alaska (GOA) glaciers from a new GRACE global solution of equal-area surface <span class="hlt">mass</span> concentration parcels (mascons) in equivalent height of water. The mascons were estimated directly from the reduction of the inter-satellite K-band range-rate (KBRR) observations, taking into account the full noise covariance, and formally iterating the solution. The new solution increases signal recovery while reducing the GRACE KBRR observation residuals. The mascons were estimated with 10 day and 1 arc degree equal-area sampling, applying anisotropic constraints. An ensemble empirical mode decomposition adaptive filter was applied to the mascon time series to compute annual <span class="hlt">mass</span> <span class="hlt">balances</span>. The details and causes of the spatial and temporal variability of the land-<span class="hlt">ice</span> regions studied are discussed. The estimated <span class="hlt">mass</span> trend over the total GIS, AIS and GOA glaciers for the time period 1 December 2003 to 1 December 2010 is -380 plus or minus 31 Gt a(exp -1), equivalent to -1.05 plus or minus 0.09 mma(exp -1) sea-level rise. Over the same time period we estimate the <span class="hlt">mass</span> acceleration to be -41 plus or minus 27 Gt a(exp -2), equivalent to a 0.11 plus or minus 0.08 mm a(exp -2) rate of change in sea level. The trends and accelerations are dependent on significant seasonal and annual <span class="hlt">balance</span> anomalies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160003526','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160003526"><span>Antarctica, Greenland and Gulf of Alaska Land-<span class="hlt">Ice</span> Evolution from an Iterated GRACE Global Mascon Solution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Luthcke, Scott B.; Sabaka, T. J.; Loomis, B. D.; Arendt, A. A.; McCarthy, J. J.; Camp, J.</p> <p>2013-01-01</p> <p>We have determined the <span class="hlt">ice</span> <span class="hlt">mass</span> evolution of the Antarctica and Greenland <span class="hlt">ice</span> sheets (AIS and GIS) and Gulf of Alaska (GOA) glaciers from a new GRACE global solution of equal-area surface <span class="hlt">mass</span> concentration parcels (mascons) in equivalent height of water. The mascons were estimated directly from the reduction of the inter-satellite K-band range-rate (KBRR) observations, taking into account the full noise covariance, and formally iterating the solution. The new solution increases signal recovery while reducing the GRACE KBRR observation residuals. The mascons were estimated with 10 day and 1 arc degree equal-area sampling, applying anisotropic constraints. An ensemble empirical mode decomposition adaptive filter was applied to the mascon time series to compute annual <span class="hlt">mass</span> <span class="hlt">balances</span>. The details and causes of the spatial and temporal variability of the land-<span class="hlt">ice</span> regions studied are discussed. The estimated <span class="hlt">mass</span> trend over the total GIS, AIS and GOA glaciers for the time period 1 December 2003 to 1 December 2010 is -380 plus or minus 31 Gt a(exp -1), equivalent to -1.05 plus or minus 0.09 mma(exp -1) sea-level rise. Over the same time period we estimate the <span class="hlt">mass</span> acceleration to be -41 plus or minus 27 Gt a(exp -2), equivalent to a 0.11 plus or minus 0.08 mm a(exp -2) rate of change in sea level. The trends and accelerations are dependent on significant seasonal and annual <span class="hlt">balance</span> anomalies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ESSD....9...47C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ESSD....9...47C"><span>Glaciological measurements and <span class="hlt">mass</span> <span class="hlt">balances</span> from Sperry Glacier, Montana, USA, years 2005-2015</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clark, Adam M.; Fagre, Daniel B.; Peitzsch, Erich H.; Reardon, Blase A.; Harper, Joel T.</p> <p>2017-01-01</p> <p>Glacier <span class="hlt">mass</span> <span class="hlt">balance</span> measurements help to provide an understanding of the behavior of glaciers and their response to local and regional climate. In 2005 the United States Geological Survey established a surface <span class="hlt">mass</span> <span class="hlt">balance</span> monitoring program on Sperry Glacier, Montana, USA. This project is the first quantitative study of <span class="hlt">mass</span> changes of a glacier in the US northern Rocky Mountains and continues to the present. The following paper describes the methods used during the first 11 years of measurements and reports the associated results. From 2005 to 2015, Sperry Glacier had a cumulative mean <span class="hlt">mass</span> <span class="hlt">balance</span> loss of 4.37 m w.e. (water equivalent). The mean winter, summer, and annual glacier-wide <span class="hlt">mass</span> <span class="hlt">balances</span> were 2.92, -3.41, and -0.40 m w.e. yr-1 respectively. We derive these cumulative and mean results from an expansive data set of snow depth, snow density, and ablation measurements taken at selected points on the glacier. These data allow for the determination of <span class="hlt">mass</span> <span class="hlt">balance</span> point values and a time series of seasonal and annual glacier-wide <span class="hlt">mass</span> <span class="hlt">balances</span> for all 11 measurement years. We also provide measurements of glacier extent and accumulation areas for select years. All data have been submitted to the World Glacier Monitoring Service and are available at <a href="http://dx.doi.org/10.5904/wgms-fog-2016-08" target="_blank">doi:10.5904/wgms-fog-2016-08</a>. This foundational work provides valuable insight about Sperry Glacier and supplies additional data to the worldwide record of glaciers measured using the glaciological method. Future research will focus on the processes that control accumulation and ablation patterns across the glacier. Also we plan to examine the uncertainties related to our methods and eventually quantify a more robust estimate of error associated with our results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Sci...358..781M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Sci...358..781M"><span>Cordilleran <span class="hlt">Ice</span> Sheet <span class="hlt">mass</span> loss preceded climate reversals near the Pleistocene Termination</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Menounos, B.; Goehring, B. M.; Osborn, G.; Margold, M.; Ward, B.; Bond, J.; Clarke, G. K. C.; Clague, J. J.; Lakeman, T.; Koch, J.; Caffee, M. W.; Gosse, J.; Stroeven, A. P.; Seguinot, J.; Heyman, J.</p> <p>2017-11-01</p> <p>The Cordilleran <span class="hlt">Ice</span> Sheet (CIS) once covered an area comparable to that of Greenland. Previous geologic evidence and numerical models indicate that the <span class="hlt">ice</span> sheet covered much of westernmost Canada as late as 12.5 thousand years ago (ka). New data indicate that substantial areas throughout westernmost Canada were <span class="hlt">ice</span> free prior to 12.5 ka and some as early as 14.0 ka, with implications for climate dynamics and the timing of meltwater discharge to the Pacific and Arctic oceans. Early Bølling-Allerød warmth halved the <span class="hlt">mass</span> of the CIS in as little as 500 years, causing 2.5 to 3.0 meters of sea-level rise. Dozens of cirque and valley glaciers, along with the southern margin of the CIS, advanced into recently deglaciated regions during the Bølling-Allerød and Younger Dryas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4928901','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4928901"><span>Pan–<span class="hlt">ice</span>-sheet glacier terminus change in East Antarctica reveals sensitivity of Wilkes Land to sea-<span class="hlt">ice</span> changes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Miles, Bertie W. J.; Stokes, Chris R.; Jamieson, Stewart S. R.</p> <p>2016-01-01</p> <p>The dynamics of ocean-terminating outlet glaciers are an important component of <span class="hlt">ice</span>-sheet <span class="hlt">mass</span> <span class="hlt">balance</span>. Using satellite imagery for the past 40 years, we compile an approximately decadal record of outlet-glacier terminus position change around the entire East Antarctic <span class="hlt">Ice</span> Sheet (EAIS) marine margin. We find that most outlet glaciers retreated during the period 1974–1990, before switching to advance in every drainage basin during the two most recent periods, 1990–2000 and 2000–2012. The only exception to this trend was in Wilkes Land, where the majority of glaciers (74%) retreated between 2000 and 2012. We hypothesize that this anomalous retreat is linked to a reduction in sea <span class="hlt">ice</span> and associated impacts on ocean stratification, which increases the incursion of warm deep water toward glacier termini. Because Wilkes Land overlies a large marine basin, it raises the possibility of a future sea level contribution from this sector of East Antarctica. PMID:27386519</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27386519','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27386519"><span>Pan-<span class="hlt">ice</span>-sheet glacier terminus change in East Antarctica reveals sensitivity of Wilkes Land to sea-<span class="hlt">ice</span> changes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Miles, Bertie W J; Stokes, Chris R; Jamieson, Stewart S R</p> <p>2016-05-01</p> <p>The dynamics of ocean-terminating outlet glaciers are an important component of <span class="hlt">ice</span>-sheet <span class="hlt">mass</span> <span class="hlt">balance</span>. Using satellite imagery for the past 40 years, we compile an approximately decadal record of outlet-glacier terminus position change around the entire East Antarctic <span class="hlt">Ice</span> Sheet (EAIS) marine margin. We find that most outlet glaciers retreated during the period 1974-1990, before switching to advance in every drainage basin during the two most recent periods, 1990-2000 and 2000-2012. The only exception to this trend was in Wilkes Land, where the majority of glaciers (74%) retreated between 2000 and 2012. We hypothesize that this anomalous retreat is linked to a reduction in sea <span class="hlt">ice</span> and associated impacts on ocean stratification, which increases the incursion of warm deep water toward glacier termini. Because Wilkes Land overlies a large marine basin, it raises the possibility of a future sea level contribution from this sector of East Antarctica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/sir/2010/5247/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/sir/2010/5247/"><span>Re-analysis of Alaskan benchmark glacier <span class="hlt">mass-balance</span> data using the index method</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Van Beusekom, Ashely E.; O'Nell, Shad R.; March, Rod S.; Sass, Louis C.; Cox, Leif H.</p> <p>2010-01-01</p> <p>At Gulkana and Wolverine Glaciers, designated the Alaskan benchmark glaciers, we re-analyzed and re-computed the <span class="hlt">mass</span> <span class="hlt">balance</span> time series from 1966 to 2009 to accomplish our goal of making more robust time series. Each glacier's data record was analyzed with the same methods. For surface processes, we estimated missing information with an improved degree-day model. Degree-day models predict ablation from the sum of daily mean temperatures and an empirical degree-day factor. We modernized the traditional degree-day model and derived new degree-day factors in an effort to match the <span class="hlt">balance</span> time series more closely. We estimated missing yearly-site data with a new <span class="hlt">balance</span> gradient method. These efforts showed that an additional step needed to be taken at Wolverine Glacier to adjust for non-representative index sites. As with the previously calculated <span class="hlt">mass</span> <span class="hlt">balances</span>, the re-analyzed <span class="hlt">balances</span> showed a continuing trend of <span class="hlt">mass</span> loss. We noted that the time series, and thus our estimate of the cumulative <span class="hlt">mass</span> loss over the period of record, was very sensitive to the data input, and suggest the need to add data-collection sites and modernize our weather stations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1918765S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1918765S"><span>Under-<span class="hlt">ice</span> melt ponds in the Arctic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, Naomi; Flocco, Daniela; Feltham, Daniel</p> <p>2017-04-01</p> <p>In the summer months, melt water from the surface of the Arctic sea <span class="hlt">ice</span> can percolate down through the <span class="hlt">ice</span> and flow out of its base. This water is relatively warm and fresh compared to the ocean water beneath it, and so it floats between the <span class="hlt">ice</span> and the oceanic mixed layer, forming pools of melt water called under-<span class="hlt">ice</span> melt ponds. Double diffusion can lead to the formation of a sheet of <span class="hlt">ice</span>, which is called a false bottom, at the interface between the fresh water and the ocean. These false bottoms isolate under-<span class="hlt">ice</span> melt ponds from the ocean below, trapping the fresh water against the sea <span class="hlt">ice</span>. These ponds and false bottoms have been estimated to cover between 5 and 40% of the base of the sea <span class="hlt">ice</span>. [Notz et al. Journal of Geophysical Research 2003] We have developed a one-dimensional thermodynamic model of sea <span class="hlt">ice</span> underlain by an under-<span class="hlt">ice</span> melt pond and false bottom. Not only has this allowed us to simulate the evolution of under-<span class="hlt">ice</span> melt ponds over time, identifying an alternative outcome than previously observed in the field, but sensitivity studies have helped us to estimate the impact that these pools of fresh water have on the <span class="hlt">mass-balance</span> sea <span class="hlt">ice</span>. We have also found evidence of a possible positive feedback cycle whereby increasingly less <span class="hlt">ice</span> growth is seen due to the presence of under-<span class="hlt">ice</span> melt ponds as the Arctic warms. Since the rate of basal ablation is affected by these phenomena, their presence alters the salt and freshwater fluxes from the sea <span class="hlt">ice</span> into the ocean. We have coupled our under-<span class="hlt">ice</span> melt pond model to a simple model of the oceanic mixed layer to determine how this affects mixed layer properties such as temperature, salinity, and depth. In turn, this changes the oceanic forcing reaching the sea <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C23B0783H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C23B0783H"><span>A glimpse beneath Antarctic sea <span class="hlt">ice</span>: observation of platelet-layer thickness and <span class="hlt">ice</span>-volume fraction with multi-frequency EM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hendricks, S.; Hoppmann, M.; Hunkeler, P. A.; Kalscheuer, T.; Gerdes, R.</p> <p>2015-12-01</p> <p>In Antarctica, <span class="hlt">ice</span> crystals (platelets) form and grow in supercooled waters below <span class="hlt">ice</span> shelves. These platelets rise and accumulate beneath nearby sea <span class="hlt">ice</span> to form a several meter thick sub-<span class="hlt">ice</span> platelet layer. This special <span class="hlt">ice</span> type is a unique habitat, influences sea-<span class="hlt">ice</span> <span class="hlt">mass</span> and energy <span class="hlt">balance</span>, and its volume can be interpreted as an indicator for <span class="hlt">ice</span> - ocean interactions. Although progress has been made in determining and understanding its spatio-temporal variability based on point measurements, an investigation of this phenomenon on a larger scale remains a challenge due to logistical constraints and a lack of suitable methodology. In the present study, we applied a lateral constrained Marquardt-Levenberg inversion to a unique multi-frequency electromagnetic (EM) induction sounding dataset obtained on the <span class="hlt">ice</span>-shelf influenced fast-<span class="hlt">ice</span> regime of Atka Bay, eastern Weddell Sea. We adapted the inversion algorithm to incorporate a sensor specific signal bias, and confirmed the reliability of the algorithm by performing a sensitivity study using synthetic data. We inverted the field data for sea-<span class="hlt">ice</span> and sub-<span class="hlt">ice</span> platelet-layer thickness and electrical conductivity, and calculated <span class="hlt">ice</span>-volume fractions from platelet-layer conductivities using Archie's Law. The thickness results agreed well with drill-hole validation datasets within the uncertainty range, and the <span class="hlt">ice</span>-volume fraction also yielded plausible results. Our findings imply that multi-frequency EM induction sounding is a suitable approach to efficiently map sea-<span class="hlt">ice</span> and platelet-layer properties. However, we emphasize that the successful application of this technique requires a break with traditional EM sensor calibration strategies due to the need of absolute calibration with respect to a physical forward model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950034738&hterms=TYPES+RADAR&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DTYPES%2BOF%2BRADAR','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950034738&hterms=TYPES+RADAR&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DTYPES%2BOF%2BRADAR"><span>Sea <span class="hlt">ice</span> type maps from Alaska synthetic aperture radar facility imagery: An assessment</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fetterer, Florence M.; Gineris, Denise; Kwok, Ronald</p> <p>1994-01-01</p> <p>Synthetic aperture radar (SAR) imagery received at the Alaskan SAR Facility is routinely and automatically classified on the Geophysical Processor System (GPS) to create <span class="hlt">ice</span> type maps. We evaluated the wintertime performance of the GPS classification algorithm by comparing <span class="hlt">ice</span> type percentages from supervised classification with percentages from the algorithm. The root mean square (RMS) difference for multiyear <span class="hlt">ice</span> is about 6%, while the inconsistency in supervised classification is about 3%. The algorithm separates first-year from multiyear <span class="hlt">ice</span> well, although it sometimes fails to correctly classify new <span class="hlt">ice</span> and open water owing to the wide distribution of backscatter for these classes. Our results imply a high degree of accuracy and consistency in the growing archive of multiyear and first-year <span class="hlt">ice</span> distribution maps. These results have implications for heat and <span class="hlt">mass</span> <span class="hlt">balance</span> studies which are furthered by the ability to accurately characterize <span class="hlt">ice</span> type distributions over a large part of the Arctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=66594&keyword=water+AND+virtual&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=66594&keyword=water+AND+virtual&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>LAKE MICHIGAN <span class="hlt">MASS</span> <span class="hlt">BALANCE</span> STUDY: PROGNOSIS FOR PCBS</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>The Lake Michigan <span class="hlt">Mass</span> <span class="hlt">Balance</span> Study was conducted to measure and model nutrients, atrazine, PCBs, trans-nonachlor, and mercury to gain a better understanding of the transport and fate of these substances within the system and to aid managers in the environmental decision-making ...</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. 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