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Sample records for mass balance ice

  1. 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.

  2. Greenland ice sheet mass balance: a review.

    PubMed

    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. PMID:25811969

  3. 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.

  4. Mass balance of the Antarctic ice sheet.

    PubMed

    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. PMID:16782603

  5. 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

  6. 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; 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; Sorensen, Louise Sandberg; Scambos, Ted A.; Yi, Dohngui; Zwally, H. Jay

    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.

  7. A reconciled estimate of ice-sheet mass balance.

    PubMed

    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. PMID:23197528

  8. A Novel and Low Cost Sea Ice Mass Balance Buoy.

    NASA Astrophysics Data System (ADS)

    Jackson, Keith; Meldrum, David; Wilkinson, Jeremy; Maksym, Ted; Beckers, Justin; Haas, Christian

    2013-04-01

    Understanding of sea ice mass balance processes requires continuous monitoring of the seasonal evolution of ice thickness. While autonomous ice mass balance buoys (IMBs) deployed over the past two decades have contributed to our understanding of ice growth and decay processes, deployment has been limited, in part, by the cost of such systems. Routine, basin-wide monitoring of the ice cover is realistically achievable through a network of reliable and affordable autonomous instrumentation. We describe the development of a novel autonomous platform and sensor that replaces the traditional thermistors string for monitoring temperature profiles in the ice and snow using a chain of inexpensive digital temperature chip sensors linked by a single-wire data bus. By incorporating a heating element on each sensor, the instrument is capable of resolving material interfaces (e.g. air-snow and ice-ocean boundaries) even under isothermal conditions. The instrument is small, low-cost and easy to deploy. Field and laboratory tests of the sensor chain demonstrate that the technology can reliably resolve material boundaries to within a few centimetres and over 50 scientific deployments have been made with encouraging results. The discrimination between different media based on sensor thermal response is weak in some deployments and efforts to optimise the measurement continue.

  9. A surface mass balance model for the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Bougamont, Marion; Bamber, Jonathan L.; Greuell, Wouter

    2005-12-01

    A surface mass balance model aimed at being coupled to a Global Circulation Model (GCM) for future climate prediction is described and tested for the Greenland Ice Sheet. The model builds on previous modeling designed to be forced by automatic weather station data, and includes surface energy balance as well as processes occurring near the surface such as water percolation and refreezing. Surface albedo is calculated with a new scheme that differentiates the timescale for aging of wet and dry snow and incorporates the effect of a thin layer of water and/or fresh snow at the surface. The model was driven with automatic weather station data from two sites located in the ablation zone in the Kangerlussuaq area (West Greenland), and calculated reasonable annual mass balance values (within 10% in seven out of eight cases) for four individual and consecutive years (1998-2001), using both measured and calculated albedo. This implies that the albedo parameterization is adequate and climate feedbacks affecting the mass balance are well captured. The model was then applied to a distributed 20-km-resolution grid covering the whole ice sheet, and forced with 10 years of the European Centre for Medium-range Weather Forecast (ECMWF) reanalysis (ERA-40) data. With the aim of coupling the model to a GCM, this study focuses on the ability to model the interannual variability in mass balance rather than to assess the present state of balance of the ice sheet. Modeled spatial and temporal wet zone extent compares well with information derived from passive microwave satellite data.

  10. Changes in ice dynamics and mass balance of the Antarctic ice sheet.

    PubMed

    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. PMID:16782604

  11. 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.

  12. Ice stream reorganization and ice sheet mass balance following the reactivation of Kamb Ice Stream, West Antarctica

    NASA Astrophysics Data System (ADS)

    Bougamont, Marion; Christoffersen, Poul; Price, Stephen; Carter, Sasha

    2015-04-01

    Ice streams in Antarctica account for most of the ice volume discharged to the ocean, and their flow variability greatly influences the mass balance of the ice sheet. Today, the Siple Coast region of West Antarctica is the only one to experience a positive mass balance (~36Gt/yr), as a consequence of the stagnation of Kamb Ice Stream about 170 years ago and the ongoing slowdown of Whillans Ice Stream. However, this positive trend could be temporary; past studies have shown that both ice streams experienced significant flow variability over the past millennia, with stagnation typically followed by reactivation on centennial timescales, occurring in response to internal processes. The impact this variability may have on the future mass balance of the WAIS remains unknown. Here, we explore the future flow variability of the Siple Coast ice streams by using a three-dimensional higher-order ice sheet model (CISM), coupled to a physically-based basal processes model and a model of regional hydrology. To obtain realistic initial flow conditions, we assimilate available velocity data for this region from 1997. We perform forward simulations over a 200 year period, during which the basal properties evolve according to the distribution of meltwater beneath the ice and its drainage/flow through a subglacial till layer. First, we assume that the bed evolves according to ice-till interactions with only local exchange of water between the ice and till. Next, we include a model of the regional basal water system capable of transporting water over long distances, so that meltwater is routed laterally along the bed before interacting with the till layer. We also explore the effect of geothermal heat flux uncertainties. We find that ice discharge to the grounding line is larger and more sustained in time when the regional water system is included in the simulations. Still, in all experiments, the main future perturbation to the current state of flow follows from the reactivation of

  13. Mass Balance of Arctic Sea Ice North of Svalbard during N-ICE2015

    NASA Astrophysics Data System (ADS)

    Rösel, A.; Gerland, S.; King, J.; Itkin, P.

    2015-12-01

    The N-ICE2015 cruise, led by the Norwegian Polar Institute, was a drift experiment with the research vessel R/V Lancefrom 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 during the 6 month, 4 ice stations where installed and the complex ocean-sea ice-atmosphere system was studied with an interdisciplinary approach. During the N-ICE2015 cruise, extensive ice thickness and snow depth measurements were performed during both, winter and summer conditions. Total ice and snow thickness was measured with ground-based and airborne electromagnetic instruments like EM31, GEM, and EM-bird; snow depth was measured with a GPS snow depth probe. Additionally, ice mass balance and snow buoys were deployed. Snow and ice thickness measurements were performed on repeated transects to quantify the ice growth or loss as well as the snow accumulation and melt rate. Additionally, we collected independent values on surveys to determine the general ice thickness distribution. In terms of mass balance, average snow depths of 32 cm on first year ice, and 52 cm on multiyear ice were measured in January, the mean snow depth on all ice types even increased until end of March to 49 cm. The average total ice and snow thickness in winter conditions was 1.92 cm. During winter, we found an unusual small growth rate on multiyear ice of about 15 cm in 2 months, due to above-average snow depths and some extraordanary storm events that came along with mild temperatures. In contrast thereto, we were also able to study new ice formation and thin ice on refrozen leads. In summer conditions an enormous melt rate, mainly driven by a warm Atlantic water inflow in the marginal ice zone, was observed during two ice stations with melt rates of up to 20 cm per 24 hours. The here presented dataset is a mandatory parameter for understanding the ocean-ice-atmosphere interactions, for

  14. Understanding Recent Mass Balance Changes of the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    vanderVeen, Cornelius

    2003-01-01

    The ultimate goal of this project is to better understand the current transfer of mass between the Greenland Ice 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 mass input to the ice sheet and analysis of climate records derived from ice cores, and modeling meltwater production and runoff from the margins of the ice sheet.

  15. Changes in Ice Flow Dynamics of Totten Glacier, East Antarctica and Impacts on Ice Mass Balance

    NASA Astrophysics Data System (ADS)

    Li, X.; Rignot, E. J.; Mouginot, J.; Scheuchl, B.; An, L.

    2014-12-01

    Totten Glacier, East Antarctica is one of the largest glaciers in Antarctica, draining an area of 5.3*105 km2 and containing ice at an equivalent 9 m sea level rise. Lidar/radar altimetry data from 2003-2009 suggests that the glacier is thinning. Thinning is concentrated in areas of fast flow and therefore indicative of changes in ice dynamics. Here, we employ time series of ice velocity from ERS-1/2, RADARSAT-1, LANDSAT-7, ALOS PALSAR, TanDEM/TerraSAR-X and COSMO-Skymed to measure the glacier velocity from 1996 till present. We find significant temporal changes in ice velocity, especially in 1996-2007, followed by a period of slow decrease in 2010-2013. Comparing the results with RACMO2 surface mass balance in the interior suggests that the glacier mass balance was already negative in 1996 and became more negative into the 2000s. The resulting mass loss and stretching of the ice is compatible with the 1.5 m/yr thinning detected by the radar altimeters near the grounding zone. The grounding zone of the glacier includes a vast 15 km long ice plain where the glacier is only grounded a few 10m above hydrostatic equilibrium. We detect a retreat of the region of partial floatation with time, but not solid migration of the grounding line of the glacier. Inverted bathymetry results from gravity data collected offshore suggest the presence of a paleo subglacial channel conducive to the transfer of surface ocean heat, likely diluted circumpolar deep water, whose transfer to the ice shelf cavity may have affected the glacier stability. We suggest that further transfer of ocean heat to the ice shelf could trigger a rapid glacier retreat in this region.

  16. Testing the Mass Balance of the Laurentide Ice Sheet During the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Ullman, D. J.; Carlson, A. E.; Legrande, A. N.; Anslow, F. S.; Licciardi, J. M.; Caffee, M. W.

    2010-12-01

    Recent findings have suggested that the global Last Glacial Maximum occurred 26.5-20 ka. During this time, ice sheets were at their maximum extent and eustatic sea level was nearly 130 m lower than present. Such stability of Northern Hemisphere ice sheets suggests a nearly neutral net mass balance. Here we test the mass balance of the Laurentide Ice Sheet at the Last Glacial Maximum using an energy-mass balance model and two different ice sheet configurations. The energy-mass balance model is forced by simulated climate from the NASA Goddard Institute for Space Studies Model E-R, consistent with Last Glacial Maximum conditions. This coupled atmosphere-ocean global climate model contains water isotope tracers throughout the hydrologic cycle, which are used to constrain model skill against water isotopic records. Two model experiments are performed with different Laurentide Ice Sheet configurations: one using the ICE-5G geophysical reconstruction and the other using an alternative reconstruction based on a flow-line model that simulates glacier dynamics over deformable and rigid beds. These two reconstructions have widely contrasting ice sheet geometries at the Last Glacial Maximum, with the ICE-5G reconstruction having a much larger Keewatin Dome over west-central Canada, while the largest mass center according to the flow-line model is in the Labrador Dome over eastern Canada. This disparity in ice sheet geometry may result in large differences in simulated climate and net ice sheet mass balance. Initial results suggest that 1) the ICE-5G ice sheet forces a Last Glacial Maximum climate in conflict with paleoceanographic reconstructions of ocean circulation, whereas the flow-line ice sheet is in better agreement with circulation reconstructions; and 2) the initial increase in boreal summer insolation could trigger a negative mass balance for the Laurentide Ice Sheet by 21 ka, driving ice retreat. We will also compare our mass balance results with existing

  17. 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.

  18. Recent ice dynamic and surface mass balance of Union Glacier in the West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

    Rivera, A.; Zamora, R.; Uribe, J. A.; Jaña, R.; Oberreuter, J.

    2014-08-01

    Here we present the results of a comprehensive glaciological investigation of Union Glacier (79°46' S/83°24' W) in the West Antarctic Ice Sheet (WAIS), a major outlet glacier within the Ellsworth Mountains. Union Glacier flows into the Ronne Ice Shelf, where recent models have indicated the potential for significant grounding line zone (GLZ) migrations in response to changing climate and ocean conditions. To elaborate a glaciological base line that can help to evaluate the potential impact of this GLZ change scenario, we installed an array of stakes on Union Glacier in 2007. The stake network has been surveyed repeatedly for elevation, velocity, and net surface mass balance. The region of the stake measurements is in near-equilibrium, and ice speeds are 10 to 33 m a-1. Ground-penetrating radars (GPR) have been used to map the subglacial topography, internal structure, and crevasse frequency and depth along surveyed tracks in the stake site area. The bedrock in this area has a minimum elevation of -858 m a.s.l., significantly deeper than shown by BEDMAP2 data. However, between this deeper area and the local GLZ, there is a threshold where the subglacial topography shows a maximum altitude of 190 m. This subglacial condition implies that an upstream migration of the GLZ will not have strong effects on Union Glacier until it passes beyond this shallow ice pinning point.

  19. Runoff, precipitation, mass balance, and ice velocity measurements at South Cascade Glacier, Washington, 1993 balance year

    USGS Publications Warehouse

    Krimmel, R.M.

    1994-01-01

    Winter snow accumulation and summer snow, firn, and ice ablation were measured at South Cascade Glacier, Wash., to determine the winter and net balance for the 1993 balance year. The 1993 winter balance, averaged over the glacier, was 1.98 meters, and the net balance was -1.23 meters. This negative valance continued a trend of negative balance years beginning in 1977. Air temperature, barometric pressure, and runoff from this glacier basin and an adjacent non-glacierized basin were also continuously measured. Surface ice velocity was measured over an annual period. This report makes all these data available to users throughout the glaciological and climato1ogical community.

  20. Insight into glacier climate interaction: reconstruction of the mass balance field using ice extent data

    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.

  1. Changes of the Arctic Ice Caps from ICESat and GRACE - A study of mass balance.

    NASA Astrophysics Data System (ADS)

    Nilsson, Johan; Sandberg Sørensen, Louise; Barletta, Valentina Roberta; Forsberg, René

    2013-04-01

    Data from ICESat, compared with GRACE data, were used to estimate the mass balance of the smaller Arctic ice caps on Svalbard, Iceland and the Canadian Arctic from the years 2003-2009. In this study we used the repeat track method to estimate the surface elevation change of the Arctic ice caps from ICESat altimetry. The GRACE mass balance was obtained using a point mass modeling method, which allowed a better separation of the dominant signal from the Greenland Ice Sheet. In the ICESat part of the study we used several different methods for estimating the mass balance. The methods where based on both interpolation and extrapolation of the elevation change estimates over the ice caps, using both parametric and non-parametric approaches. We found that all Arctic ice caps show a consistent negative mass balance from the year 2003-2009. Ranging from -3 to -26 Gt/yr from the ICESat estimates for the different regions, which is in good agreement with the GRACE results. Also found is that the choice of method used for the ICESat analysis can have a significant impact on the mass balance.

  2. 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.

  3. Multiyear sea ice thermal regimes and oceanic heat flux derived from an ice mass balance buoy in the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Lei, Ruibo; Li, Na; Heil, Petra; Cheng, Bin; Zhang, Zhanhai; Sun, Bo

    2014-01-01

    The conductive and oceanic heat fluxes and the mass balance of sea ice were investigated utilizing an ice mass balance buoy (IMB) deployed in the Arctic Ocean. After IMB deployment, the ice thinned from 1.95 m in late August to 1.46 m by mid-October 2008. From then on, ice growth until mid-June 2009 increased the ice thickness to 3.12 m. The ice temperature and consequently the conductive heat flux at the ice surface exhibited persistent high-frequency variations due to diurnal and synoptic-scale atmospheric forcing. These signals propagated downward with damped magnitude and temporal lag. The competition of oceanic and conductive heat flux dominated the low-frequency variations of ice growth. However, high-frequency variations in ice growth were controlled largely by the oceanic heat flux. From mid-November 2008 to mid-June 2009, the average oceanic heat flux along a track from 86.2°N, 115.2°W to 84.6°N, 33.9°W was 7.1 W/m2. This was in agreement with that derived from an IMB deployed in 2005, about 1.5° to the north of our buoy. We attributed the relatively high oceanic heat flux (10-15 W/m2) observed during autumn and early winter to summer warming of the surface ocean. Upward mixing of warm deep water, as observed when our buoy drifted over the shallow region of the Lomonosov Ridge (85.4°-85.9°N, 52.2°-66.4°W), demonstrated the impact of bathymetry on the oceanic heat flux under ice cover, and consequently on the basal ice mass balance.

  4. Mass Balance Changes and Ice Dynamics of Greenland and Antarctic Ice Sheets from Laser Altimetry

    NASA Astrophysics Data System (ADS)

    Babonis, G. S.; Csatho, B.; Schenk, T.

    2016-06-01

    During the past few decades the Greenland and Antarctic ice sheets have lost ice at accelerating rates, caused by increasing surface temperature. The melting of the two big ice sheets has a big impact on global sea level rise. If the ice 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 Ice, Cloud and land Elevation Satellite mission (ICESat) and airborne laser campaigns, such as Airborne Topographic Mapper (ATM) and Land, Vegetation and Ice Sensor (LVIS). For detecting changes in ice 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 ice caps and the temporal extension from 1993 to 2014 for the Greenland Ice Sheet and for a comprehensive reconstruction of ice thickness and mass changes for the Antarctic Ice Sheets.

  5. Gravimetric mass balance products for the Antarctic and Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Horwath, Martin; Groh, Andreas; Horvath, Alexander; Forsberg, Rene; Meister, Rakia; Shepherd, Andrew; Hogg, Anna; Muir, Alan

    2016-04-01

    Within the framework of ESA's Climate Change Initiative (CCI) mass balance products for both the Antarctic Ice Sheet (AIS) and the Greenland Ice Sheet (GIS) have been developed by the AIS_cci and the GIS_cci project. These Gravimetric Mass Balance (GMB) products are derived from satellite gravimetry data acquired by GRACE (Gravity Recovery and Climate Experiment), which is the only sensor directly sensitive to changes in mass. Using monthly GRACE gravity field solutions covering the period from 2002 until present two different GMB products are derived: (a) time series of monthly mass changes for the entire ice sheet and for individual drainage basins, and (b) gridded mass changes covering the entire ice sheet. The gridded product depicts spatial patterns of mass changes at a formal resolution of about 50 km, although the effective resolution provided by GRACE is about 200-500km. The algorithms used for the product generation have been selected within an open round robin experiment and are optimized to account for the complex GRACE error structures, to advance the limited spatial resolution and to separate signals super-imposed to mass changes of the cryosphere. Here the first release of the ESA CCI GMB products is presented. Both the basin averaged and the gridded products are assessed regarding their signal content and error characteristics. Finally, up-to-date mass balance estimates are presented for both ice sheets. The GMB products are freely accessible through data portals hosted by the AIS_cci and the GIS_cci project.

  6. 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.

  7. 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

  8. Using GRACE measurements of time variable gravity, elevation changes from ICESat, OIB and ENVISAT and surface mass balance outputs from RACMO to improve ice mass balance estimates

    NASA Astrophysics Data System (ADS)

    Sutterley, T. C.; Velicogna, I.; Csatho, B. M.; van den Broeke, M. R.; Wahr, J. M.; Flament, T.; Rezvan-Behbahani, S.; Babonis, G. S.; A, G.

    2013-12-01

    The glacial isostatic adjustment (GIA) correction represents a source of uncertainty for ice sheet mass balance estimates from the Gravity Recovery and Climate Experiment (GRACE) time variable gravity measurements. We evaluate Greenland and Antarctic GIA corrections by comparing the spatial patterns of GRACE-derived ice mass trends corrected for glacial isostatic adjustment with volume changes from ICESat (Ice, Cloud, and Land Elevation Satellite), OIB (Operation IceBridge) and ENVISAT altimetry missions, and surface mass balance (SMB) products from the Regional Atmospheric Climate Model (RACMO). We show that using the spatial and temporal characteristics of the different contributions to the ice mass balance estimates that it is possible to evaluate different GIA corrections. In Greenland, the GRACE ice mass changes obtained using the Simpson et al. (2009) and Geruo et al. (2013) GIA corrections show good agreement in the spatial patterns and amplitude. The GRACE estimate corrected using the Wu et al. (2010) GIA shows similar spatial patterns to the other two, but produces an average ice mass loss for the entire ice sheet that is 50% smaller. In Antarctica, the total magnitude and spatial structure of the GRACE-estimated ice mass change is highly dependent on the GIA correction. In key basins of East Antarctica, the interpretation of regional ice mass changes can reflect the GIA model selection as the ice mass to GIA signal ratio is smaller. We apply the same methodology used for the Greenland ice sheet in Antarctica to evaluate the different GIA corrections and check for consistency between the different techniques at a regional scale.

  9. Mass balance, meteorological, ice motion, surface altitude, runoff, and ice thickness data at Gulkana Glacier, Alaska, 1995 balance year

    USGS Publications Warehouse

    March, Rod S.

    2000-01-01

    The 1995 measured winter snow, maximum winter snow, net, and annual balances 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 balance was 0.94 meter on April 19, 1995, 0.6 standard deviation below the long-term average; the maximum winter snow balance, 0.94 meter, was reached on April 25, 1995; the net balance (from September 18, 1994 to August 29, 1995) was -0.70 meter, 0.76 standard deviation below the long-term average. The annual balance (October 1, 1994, to September 30, 1995) was -0.86 meter. Ice-surface motion and altitude changes measured at three index sites document seasonal ice 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 ice-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 balances 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 balances. The balance increase is of the order of 15 percent for net balance.

  10. Mass balance of Icelandic ice caps from CryoSat swath mode altimetry

    NASA Astrophysics Data System (ADS)

    Foresta, L.; Gourmelen, N.; Pálsson, F.; Willis, I. C.; Nienow, P. W.; Shepherd, A.

    2015-12-01

    Satellite altimetry has been traditionally used in the past to infer elevation of land ice, quantify changes in ice topography and infer mass balance over large and remote areas such as the Greenland and Antarctic ice sheets. Radar Altimetry (RA) is particularly well suited to this task due to its all-weather year-round capability for observing the ice surface. However, monitoring of ice caps 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 mass balance estimates from RA rely on extrapolation methods to regionalize elevation change.Since 2010, the Synthetic Interferometric Radar Altimeter (SIRAL) on board the ESA radar altimetry CryoSat mission has collected ice elevation measurements over ice caps. Ground track interspacing (~4km at 60°) is one order of magnitude smaller than ERS/ENVISAT missions and half of ICESAT's, providing dense spatial coverage. Additionally the Synthetic Aperture Radar Interferometric (SARIn) mode of CryoSat provides a reduced footprint and the ability to locate accurately the position of the surface reflection. Conventional altimetry provides the elevation of the Point Of Closest Approach (POCA) within each waveform, every 250 m along the flight path. Time evolution of POCA elevation is then used to investigate ice elevation change.Here, we present an assessment of the geodetic mass balance of Icelandic ice caps using a novel processing approach, swath altimetry, applied to CryoSat SARIn mode data. In swath mode altimetry, elevation beyond the POCA is extracted from the waveform when coherent echoes are present providing between one and two orders of magnitude more elevations when compared to POCA. We generate maps of ice elevation change that are then used to compute geodetic mass balance for the period 2010 to 2015. We compare our results to estimates generated using

  11. 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.

  12. 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.

  13. 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

  14. A possible change in mass balance of Greenland and Antarctic ice sheets in the coming century

    SciTech Connect

    Ohmura, A.; Wild, M.; Bengtsson, L.

    1996-09-01

    A high-resolution GCM is found to simulate precipitation and surface energy balance of high latitudes with high accuracy. This opens new possibilities to investigate the future mass balance of polar glaciers and its effect on sea level. The surface mass balance of the Greenland and the Antarctic ice sheets is simulated using the ECHAM3 GCM with T106 horizontal resolution. With this model, two 5-year integrations for the present and doubled carbon dioxide conditions based on the boundary conditions provided by the ECHAM1/T21 transient to what extent the effect of climate change on the mass balance on the two largest glaciers of the world can differ. On Greenland one sees a slight decrease in accumulation and a substantial increase in melt, while on Antarctica a large increase in accumulation without melt is projected. Translating the mass balances into terms of sea-level equivalent, the Greenland discharge causes a sea level rise of 1.1 mm yr{sup {minus}1}, while the accumulation on Antarctica tends to lower it by 0.9 mm yr{sup {minus}1}. The change in the combined mass balance of the two continents is almost zero. The sea level change of the next century can be affected more effectively by the thermal expansion of seawater and the mass balance of smaller glaciers outside of Greenland and Antarctica. 24 refs., 11 figs., 2 tabs.

  15. 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

  16. 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

  17. Columbia Glacier stake location, mass balance, glacier surface altitude, and ice radar data, 1978 measurement year

    USGS Publications Warehouse

    Mayo, L.R.; Trabant, D.C.; March, Rod; Haeberli, Wilfried

    1979-01-01

    A 1 year data-collection program on Columbia Glacier, Alaska has produced a data set consisting of near-surface ice kinematics, mass balance, and altitude change at 57 points and 34 ice 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)

  18. Regional ice mass balance for Greenland from GRACE and ICESat modelled by radial basis functions

    NASA Astrophysics Data System (ADS)

    Eicker, A.; Springer, A.; Jensen, L.; Kusche, J.

    2012-04-01

    This contribution presents a tailored regional mass balance for the Greenland ice sheet from GRACE and ICESat observations. A regional gravity field trend model is calculated directly from the GRACE level 1B observations using the short arc method. The gravity field model is parameterized by harmonic space localizing radial basis functions that can be tailored to the specific signal characteristics in Greenland. The ICESat along-track ice elevation changes are co-estimated together with the local topography in order to be independent from external elevation models. The along-track observations are then evaluated without any necessary gridding consistently with the GRACE processing in the same basis of radial basis functions. This allows further joint analysis of the two data sets in this same basis.

  19. Estimation of Greenland's Ice Sheet Mass Balance Using ICESat and GRACE Data

    NASA Astrophysics Data System (ADS)

    Slobbe, D.; Ditmar, P.; Lindenbergh, R.

    2007-12-01

    Data of the GRACE gravity mission and the ICESat laser altimetry mission are used to create two independent estimates of Greenland's ice sheet mass balance 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 mass 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 mass balance 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 mass balance 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.

  20. Small impact of surrounding oceanic conditions on 2007-2012 Greenland Ice Sheet surface mass balance

    NASA Astrophysics Data System (ADS)

    Noël, B.; Fettweis, X.; van de Berg, W. J.; van den Broeke, M. R.; Erpicum, M.

    2014-03-01

    During recent summers (2007-2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North-Atlantic Oscillation (NAO), favouring warmer than normal conditions over the GrIS. In addition, it has been suggested that significant anomalies in sea ice cover (SIC) and sea surface temperature (SST) may partially explain recent anomalous GrIS surface melt. To assess the impact of 2007-2012 SIC and SST anomalies on GrIS surface mass balance (SMB), a set of sensitivity experiments was carried out with the regional climate model MAR. These simulations suggest that changes in SST and SIC in the seas surrounding Greenland do not significantly impact GrIS SMB, due to the katabatic winds blocking effect. These winds are strong enough to prevent oceanic near-surface air, influenced by SIC and SST variability, from penetrating far inland. Therefore, the ice sheet SMB response is restricted to coastal regions, where katabatic winds are weaker. However, anomalies in SIC and SST could have indirectly affected the surface melt by changing the general circulation in the North Atlantic region, favouring more frequent warm air advection to the GrIS.

  1. From Outlet Glacier Changes to Ice Sheet Mass Balance - Evolution of Greenland Ice Sheet from Laser Altimetry Data

    NASA Astrophysics Data System (ADS)

    Csatho, B. M.; Schenk, A.; Nagarajan, S.; Babonis, G. S.

    2010-12-01

    Investigations of ice sheet mass balance 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 Ice 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 ice 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 ice 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 Ice Sheet between 2003 and 2009 on a high-resolution grid. Our reconstruction, consistent with GRACE results, shows ice sheet thinning propagating

  2. Airborne Laser Altimetry Mapping of the Greenland Ice Sheet: Application to Mass Balance Assessment

    NASA Technical Reports Server (NTRS)

    Abdalati, W.; Krabill, W.; Frederick, E.; Manizade, S.; Martin, C.; Sonntag, J.; Swift, R.; Thomas, R.; Wright, W.; Yungel, J.

    2000-01-01

    In 1998 and '99, the Arctic Ice Mapping (AIM) program completed resurveys of lines occupied 5 years earlier revealing elevation changes of the Greenland ice sheet and identifying areas of significant thinning, thickening and balance. In planning these surveys, consideration had to be given to the spatial constraints associated with aircraft operation, the spatial nature of ice 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 balance of the Greenland ice sheet. The surveys covered the entire ice sheet with an average distance of 21.4 km between each location on the ice sheet and the nearest flight line. For most of the ice 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 balance of the entire ice 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 balance.

  3. Assessing the links between Greenland Ice Sheet Surface Mass Balance and Arctic climate using Climate Models and Observations

    NASA Astrophysics Data System (ADS)

    Mottram, Ruth; Rodehacke, Christian; Boberg, Fredrik; Langen, Peter; Sloth Madsen, Marianne; Høyer Svendsen, Synne; Yang, Shuting; Hesselbjerg Christensen, Jens; Olesen, Martin

    2016-04-01

    Changes in different parts of the Arctic cryosphere may have knock-on effects on other parts of the system. The fully coupled climate model EC-Earth, which includes the ice sheet model PISM, is a useful tool to examine interactions between sea ice, ice sheet, ocean and atmosphere. Here we present results from EC-Earth experimental simulations that show including an interactive ice sheet model changes ocean circulation, sea ice extent and regional climate with, for example, a dampening of the expected increase in Arctic temperatures under the RCP scenarios when compared with uncoupled experiments. However, the relatively coarse resolution of the climate model likely influences the calculated surface mass balance forcing applied to the ice sheet model and it is important therefore to evaluate the model performance over the ice sheet. Here, we assess the quality of the climate forcing from the GCM to the ice sheet model by comparing the energy balance and surface mass balance (SMB) output from EC-Earth with that from a regional climate model (RCM) run at very high resolution (0.05 degrees) over Greenland. The RCM, HIRHAM5, has been evaluated over a wide range of climate parameters for Greenland which allows us to be confident it gives a representative climate forcing for the Greenland ice sheet. To evaluate the internal variability in the climate forcing, we compare simulations from HIRHAM5 forced with both the EC-Earth historical emissions and the ERA-Interim reanalysis on the boundaries. The EC-Earth-PISM RCP8.5 scenario is also compared with an EC-Earth run without an ice sheet to assess the impact of an interactive ice sheet on likely future changes. To account for the resolution difference between the models we downscale both EC-Earth and HIRHAM5 simulations with a simple offline energy balance model (EBM).

  4. Constraining ice sheet mass balance trends using Cryosat-2 and laser altimetry

    NASA Astrophysics Data System (ADS)

    Griggs, J.; Bamber, J. L.

    2012-12-01

    The mass balance of the Antarctic and Greenland is required to assess their contribution to sea level rise as well as evaluate their sensitivities to variable future forcings. There is general agreement that the ice sheets are losing mass and that loss may be increasing. However, the range of estimates and the uncertainty in those estimates is in many cases, larger than the signal measured, particularly in a regional sense. Cryosat-2 will improve on the legacy satellite measurements from ERS-1 and -2 by using its interferometric model to determine elevation on steep slopes and through it's greater across - track resolution. The new technique will overcome many of the limitations of previous radar altimeters but elevations will still suffer from variable penetration in the firn and errors due to short-wavelength roughness. Building on previous work comparing and combining laser and radar altimeter data, we will assess the uncertainty in elevation due to these limitations. We use NASA Operation Ice Bridge airborne laser altimetry to assess biases in absolute elevation and elevation rates from Cryosat-2 data. We focus on the first 6 months of released data from the mission so that variability in penetration observed can be attributed to seasonal temperature, melt and accumulation variations can be assessed. Unfortunately, coincident airborne data is not currently available so we will assess the impact of the time difference between the datasets as well as presenting comparisons to older, longer time period, NASA ICESat satellite altimetry. The project aims to fully quantify biases and develop algorithms to correct for them and here we present our first comparisons. This will allow us to determine the likely improvement in mass balance estimates from Cryosat-2 as compared to legacy datasets.

  5. A mascon approach to assess ice sheet and glacier mass balances and their uncertainties from GRACE data

    NASA Astrophysics Data System (ADS)

    Schrama, Ernst J. O.; Wouters, Bert; Rietbroek, Roelof

    2014-07-01

    The purpose of this paper is to assess the mass changes of the Greenland Ice Sheet (GrIS), Ice Sheets over Antarctica, and Land glaciers and Ice Caps with a global mascon method that yields monthly mass variations at 10,242 mascons. Input for this method are level 2 data from the Gravity Recovery and Climate Experiment (GRACE) system collected between February 2003 and June 2013 to which a number of corrections are made. With glacial isostatic adjustment (GIA) corrections from an ensemble of models based on different ice histories and rheologic Earth model parameters, we find for Greenland a mass loss of -278 ± 19 Gt/yr. Whereas the mass balances for the GrIS appear to be less sensitive to GIA modeling uncertainties, this is not the case with the mass balance of Antarctica. Ice history models for Antarctica were recently improved, and updated historic ice height data sets and GPS time series have been used to generate new GIA models. We investigated the effect of two new GIA models for Antarctica and found -92 ± 26 Gt/yr which is half of what is obtained with ICE-5G-based GIA models, where the largest GIA model differences occur on East Antarctica. The mass balance of land glaciers and ice caps currently stands at -162 ± 10 Gt/yr. With the help of new GIA models for Antarctica, we assess the mass contribution to the mean sea level at 1.47 ± 0.09 mm/yr or 532 ± 34Gt/yr which is roughly half of the global sea level rise signal obtained from tide gauges and satellite altimetry.

  6. Evaluation of glacier mass balance by observing variations in transient snowline positions. [Jostedalsbreen ice cap, Norway

    NASA Technical Reports Server (NTRS)

    Oestrem, G. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. The transient snowline on five outlet glaciers from the Jostedalsbreen ice-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' mass balance 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.

  7. The Thermal Circulation on Kilimanjaro, Tanzania and its Relevance to Summit Ice-Field Mass Balance.

    NASA Astrophysics Data System (ADS)

    Pepin, N. C.; Duane, W. J.

    2008-12-01

    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 ice-field mass balance 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 ice fields on Kilimanjaro, and make mass-balance somewhat divorced from larger-scale advective changes associated

  8. Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1994 balance year

    USGS Publications Warehouse

    March, Rod S.

    1998-01-01

    The 1994 measured winter snow, maximum winter snow, net, and annual balances 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 balance was 1.34 meters on April 29, 1994, 0.9 standard deviation above the long-term average; the maximum winter snow balance, 1.43 meters, was reached on April 18, 1994; the net balance (from September 8, 1993 to September 17, 1994) was -0.72 meter, 0.7 standard deviation below the long-term average. The annual balance (October 1, 1992, to September 30, 1993) was -0.88 meter. Ice-surface motion and altitude changes measured at three index sites document seasonal ice speed and glacier-thickness changes. Annual stream runoff was 1.93 meters averaged over the basin, approximately equal to the long-term average.

  9. Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1992 balance year

    USGS Publications Warehouse

    March, R.S.; Trabant, D.C.

    1996-01-01

    The 1992 measured winter snow, maximum winter snow, net, and annual balances in the Gulkana Glacier basin were evaluated on the basis of meteorological, hydrological, and glaciological data measured in the basin and are reported herein. Averaged over the glacier, the measured winter snow balance was 0.97 meters on March 26, 1992; the maximum winter snow balance was 1.05 meters on May 19, 1992; the net balance (from September 8, 1991 to August 17, 1992) was -0.29 meters; and the annual balance (October 1, 1991 to September 30, 1992) was -0.38 meters. Ice surface, motion, and altitude changes measured at three index sites document seasonal changes in ice speed and glacier thickness. Annual stream runoff was 1.24 meters averaged over the basin.

  10. Assessment of Antarctic Ice-Sheet Mass Balance Estimates: 1992 - 2009

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Giovinetto, Mario B.

    2011-01-01

    Published mass balance estimates for the Antarctic Ice Sheet (AIS) lie between approximately +50 to -250 Gt/year for 1992 to 2009, which span a range equivalent to 15% of the annual mass 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 mass 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 ice-sheet area than the 85% faster-moving parts. Our calculations show that the published extrapolation overestimates the ice 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 mass 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 mass input and only 0.2 mm/year SLE. Our preferred estimate for 1992-2001 is - 47 Gt

  11. Greenland Ice Sheet Mass Balance: Distribution of Increased Mass Loss with Climate Warming; 2003-07 Versus 1992-2002

    NASA Technical Reports Server (NTRS)

    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.; Yi, Donghui; Wang, Weili

    2011-01-01

    We derive mass changes of the Greenland ice 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 balance 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 mass changes into two components: (1) from changes in melting and ice 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 mass changes. Increased losses from melting and ice 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 ice flow. Increased thinning at higher elevations appears to be induced by dynamic coupling to thinning at the margins on decadal timescales.

  12. Improved GRACE regional mass balance estimates of the Greenland ice sheet cross-validated with the input-output method

    NASA Astrophysics Data System (ADS)

    Xu, Zheng; Schrama, Ernst J. O.; van der Wal, Wouter; van den Broeke, Michiel; Enderlin, Ellyn M.

    2016-04-01

    In this study, we use satellite gravimetry data from the Gravity Recovery and Climate Experiment (GRACE) to estimate regional mass change of the Greenland ice sheet (GrIS) and neighboring glaciated regions using a least squares inversion approach. We also consider results from the input-output method (IOM). The IOM quantifies the difference between the mass input and output of the GrIS by studying the surface mass balance (SMB) and the ice discharge (D). We use the Regional Atmospheric Climate Model version 2.3 (RACMO2.3) to model the SMB and derive the ice discharge from 12 years of high-precision ice velocity and thickness surveys. We use a simulation model to quantify and correct for GRACE approximation errors in mass change between different subregions of the GrIS, and investigate the reliability of pre-1990s ice discharge estimates, which are based on the modeled runoff. We find that the difference between the IOM and our improved GRACE mass change estimates is reduced in terms of the long-term mass change when using a reference discharge derived from runoff estimates in several subareas. In most regions our GRACE and IOM solutions are consistent with other studies, but differences remain in the northwestern GrIS. We validate the GRACE mass balance in that region by considering several different GIA models and mass change estimates derived from data obtained by the Ice, Cloud and land Elevation Satellite (ICESat). We conclude that the approximated mass balance between GRACE and IOM is consistent in most GrIS regions. The difference in the northwest is likely due to underestimated uncertainties in the IOM solutions.

  13. Climatic mass balance of the ice cap Vestfonna, Svalbard: A spatially distributed assessment using ERA-Interim and MODIS data

    NASA Astrophysics Data System (ADS)

    MöLler, Marco; Finkelnburg, Roman; Braun, Matthias; Hock, Regine; Jonsell, Ulf; Pohjola, Veijo A.; Scherer, Dieter; Schneider, Christoph

    2011-09-01

    The ice cap Vestfonna in the northern Svalbard archipelago is one of the largest ice bodies of the European Arctic (˜2400 km2), but little is known about its mass balance. We model the climatic mass balance of the ice cap for the period September 2000 to August 2009 on a daily basis. Ablation is calculated by a spatially distributed temperature-radiation-index melt model. Air temperature forcing is provided by ERA-Interim data that is downscaled using data from an automatic weather station operated on the ice cap. Spatially distributed net shortwave radiation fluxes are obtained from standard trigonometric techniques combined with Moderate Resolution Imaging Spectroradiometer-based cloud cover and surface albedo information. Accumulation is derived from ERA-Interim precipitation data that are bias corrected and spatially distributed as a function of elevation. Refreezing is incorporated using the Pmax approach. Results indicate that mass balance years are characterized by short ablation seasons (June to August) and correspondingly longer accumulation periods (September to May). The modeled, annual climatic mass balance rate shows an almost balanced mean of -0.02 ± 0.20 m w.e. yr-1 (meters water equivalent per year) with an associated equilibrium line altitude of 383 ± 54 m above sea level (mean ± one standard deviation). The mean winter balance is +0.32 ± 0.06 m w.e. yr-1, and the mean summer balance -0.35 ± 0.17 m w.e. yr-1. Roughly one fourth of total surface ablation is retained by refreezing indicating that refreezing is an important component of the mass budget of Vestfonna.

  14. Thickening and Thinning of Antarctic Ice Shelves and Tongues and Mass Balance Estimates

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Li, Jun; Giovinetto, Mario; Robbins, John; Saba, Jack L.; Yi, Donghui

    2011-01-01

    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 Ice Shelf, were mostly thinning and losing mass whereas the Ronne Ice shelf also in WA was mostly thickening. The estimated total mass loss for the floating ice shelves and ice tongues from ice draining WA and the AP was 95 Gt/a. In contrast, the floating ice shelves and ice tongues from ice draining East Antarctica (EA), including the Filchner, Fimbul, Amery, and Western Ross, were mostly thickening with a total estimated mass 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 ice shelf and -42.4 and - 27.2 cm/a on the East Getz ice shelf, and some values that indicate more thinning in the latter period, including -17.9 and -36.2 cm/a on the Larsen C ice 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 mass change estimates for 2003 - 2008.

  15. Characteristics and distribution patterns of snow and meteoric ice in the Weddell Sea and their contribution to the mass balance of sea ice

    NASA Astrophysics Data System (ADS)

    Eicken, Hajo; Lange, Manfred A.; Wadhams, Peter

    1994-01-01

    Based on snow- and ice-thickness measurements at >11 000 points augmented by snow- and icecore studies during 4 expeditions from 1986 - 92 in the Weddell Sea, we describe characteristics and distribution patterns of snow and meteoric ice and assess their importance for the mass balance of sea ice. For first-year ice (FY) in the central and eastern Weddell Sea, mean snow depth amounts to 0.16 m (mean ice thickness 0.75 m) compared to 0.53 m (mean ice thickness 1.70 m) for second-year ice (SY) in the northwestern Weddell Sea. Ridged ice retains a thicker snow cover than level ice, with ice thickness and snow depth negatively correlated for the latter, most likely due to aeolian redistribution. During the different expeditions, 8, 15, 17 and 40% of all drill holes exhibited negative freeboard. As a result of flooding and brine seepage into the snow pack, snow salinities averaged 4‰. Through 18O measurements the distribution of meteoric ice (i.e. precipitation) in the sea-ice cover was assessed. Roughly 4% of the total ice thickness consist of meteoric ice (FY 3%, SY 5%). With a mean density of 290 kg/m3, the snow cover itself contributes 8% to total ice mass (7% FY, 11% SY). Analysis of 18O in snow indicates a local maximum in accumulation in the 65 to 75°S latitude zone. Hydrogen peroxide in the snow has proven useful as a temporal tracer and for identification of second-year floes. Drawing on accumulation data from stations at the Weddell Sea coast, it becomes clear that the onset of ice growth is important for the evolution of ice thickness and the interaction between ice and snow. Loss of snow to leads due to wind drift may be considerable, yet is reduced owing to metamorphic processes in the snow column. This is confirmed by a comparison of accumulation data from coastal stations and from snow depths over sea ice. Temporal and spatial accumulation patterns of snow are shown to be important in controlling the sea-ice cover evolution.

  16. Freshwater fluxes into the subpolar North Atlantic from secular trends in Arctic land ice mass balance

    NASA Astrophysics Data System (ADS)

    Bamber, J. L.; Enderlin, E. M.; Howat, I. M.; Wouters, B.; van den Broeke, M.

    2015-12-01

    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 ice 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 mass balance and gravimetry to produce consistent estimates of solid ice and liquid FWF into the Arctic and North Atlantic Oceans. The total cumulative FWF anomaly from land ice mass 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

  17. Overview and Assessment of Antarctic Ice-Sheet Mass Balance Estimates: 1992-2009

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Giovinetto, Mario B.

    2011-01-01

    Mass balance estimates for the Antarctic Ice 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 mass 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 mass 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 mass loss with time from GRACE-based studies cite agreement with IOM results, our evaluation does not support that conclusion

  18. Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1993 balance year

    USGS Publications Warehouse

    March, Rod; Trabant, Dennis

    1997-01-01

    The 1993 measured winter snow, maximum winter snow, net, and annual balances in the Gulkana Glacier basin were evaluated on the basis of meteorological, hydrological, and glaciological data measured in the basin and are reported herein. Averaged over the glacier, the measured winter snow balance was 0.81 meter on March 31, 1993, 1.2 standard deviations below the long-term average; the maximum winter snow balance, 0.84 meter, was reached on May 10, 1993 and remained until May 11, 1993; the net balance (from August 18, 1992 to September 8, 1993) was 1.80 meters, the most negative balance year on record at 2.8 standard deviations below the long-term average. The annual balance (October 1, 1992 to September 30, 1993) was 1.64 meters. Ice-surface motion and altitude changes measured at three index sites document seasonal ice speed and glacier thickness changes. Annual stream runoff was 1.996 meters averaged over the basin, 0.2 standard deviations above the long-term average.

  19. On Deriving Requirements for the Surface Mass Balance forcing of a Greenland Ice Sheet Model using Uncertainty Analyses

    NASA Astrophysics Data System (ADS)

    Schlegel, N.; Larour, E. Y.; Box, J. E.

    2015-12-01

    During July of 2012, the percentage of the Greenland surface exposed to melt was the largest in recorded history. And, even though evidence of increased melt rates had been captured by remote sensing observations throughout the last decade, this particular event took the community by surprise. How Greenland ice flow will respond to such an event or to increased frequencies of extreme melt events in the future is unclear, as it requires detailed comprehension of Greenland surface climate and the ice sheet's sensitivity to associated uncertainties. With established uncertainty quantification (UQ) tools embedded within the Ice Sheet System Model (ISSM), we conduct decadal-scale forward modeling experiments to 1) quantify the spatial resolution needed to effectively force surface mass balance (SMB) in various regions of the ice sheet and 2) determine the dynamic response of Greenland outlet glaciers to variations in SMB. First, we perform sensitivity analyses to determine how perturbations in SMB affect model output; results allow us to investigate the locations where variations most significantly affect ice flow, and on what spatial scales. Next, we apply Monte-Carlo style sampling analyses to determine how errors in SMB propagate through the model as uncertainties in estimates of Greenland ice discharge and regional mass balance. This work is performed at the California Institute of Technology's Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration's Cryosphere Program.

  20. Mass Balance of the Northern Antarctic Peninsula and its Ongoing Response to Ice Shelf Loss

    NASA Astrophysics Data System (ADS)

    Scambos, T. A.; Berthier, E.; Haran, T. M.; Shuman, C. A.; Cook, A. J.; Bohlander, J. A.

    2012-12-01

    An assessment of the most rapidly changing areas of the Antarctic Peninsula (north of 66°S) shows that ice mass loss for the region is dominated by areas affected by eastern-Peninsula ice shelf losses in the past 20 years. Little if any of the mass 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 ice mass 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 ice drainages affected by recent ice 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. Mass 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 mass loss emphasizes the significant and multi-decadal response to ice shelf loss. Areas with shelf losses occurring 30 to 100s of years ago seem to be relatively stable or losing mass only slowly (western glaciers, northernmost areas). The

  1. Oxygen Isotope Mass-Balance Constraints on Pliocene Sea Level and East Antarctic Ice Sheet Stability

    NASA Astrophysics Data System (ADS)

    Winnick, M. J.; Caves, J. K.

    2015-12-01

    The mid-Pliocene Warm Period (MPWP, 3.3-2.9 Ma), with reconstructed atmospheric pCO2 of 350-450 ppm, represents a potential analogue for climate change in the near future. Current highly cited estimates place MPWP maximum global mean sea level (GMSL) at 21 ± 10 m above modern, requiring total loss of the Greenland (GIS) and marine West Antarctic Ice Sheets (WAIS) and a substantial loss of the East Antarctic Ice Sheet (EAIS), with only a concurrent 2-3 ºC rise in global temperature. Many estimates of Pliocene GMSL are based on the partitioning of oxygen isotope records from benthic foraminifera (δ18Ob) into changes in deep-sea temperatures and terrestrial ice sheets. These isotopic budgets are underpinned by the assumption that the δ18O of Antarctic ice (δ18Oi) was the same in the Pliocene as it is today, and while the sensitivity of δ18Ob to changing meltwater δ18O has been previously considered, these analyses neglect conservation of 18O/16O in the ocean-ice system. Using well-calibrated δ18O-temperature relationships for Antarctic precipitation along with estimates of Pliocene Antarctic surface temperatures, we argue that the δ18Oi of the Pliocene Antarctic ice sheet was at minimum 1‰-4‰ higher than present. Assuming conservation of 18O/16O in the ocean-ice system, this requires lower Pliocene seawater δ18O (δ18Osw) without a corresponding change in ice sheet mass. This effect alone accounts for 5%-20% of the δ18Ob difference between the MPWP interglacials and the modern. With this amended isotope budget, we suggest that Pliocene GMSL was likely 9-13.5 m and very likely 5-17 m above modern, which suggests the EAIS is less sensitive to radiative forcing than previously inferred from the geologic record.

  2. Greenland ice sheet surface mass-balance modeling in a 131-year perspective, 1950-2080

    SciTech Connect

    Mernild, Sebastian Haugard; Liston, Glen; Hiemstra, Christopher; Christensen, Jens

    2009-01-01

    Fluctuations in the Greenland Ice Sheet (GrIS) surface mass-balance (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 balance 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 GrIS 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.

  3. Mass balance and sliding velocity of the Puget lobe of the cordilleran ice sheet during the last glaciation

    USGS Publications Warehouse

    Booth, D.B.

    1986-01-01

    An estimate of the sliding velocity and basal meltwater discharge of the Puget lobe of the Cordilleran ice sheet can be calculated from its reconstructed extent, altitude, and mass balance. Lobe dimensions and surface altitudes are inferred from ice limits and flow-direction indicators. Net annual mass balance 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 ice 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 ice 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.

  4. Antarctic Ice Sheet Surface Mass Balance Estimates from 2003 TO 2015 Using Icesat and CRYOSAT-2 Data

    NASA Astrophysics Data System (ADS)

    Xie, Huan; Hai, Gang; Chen, Lei; Liu, Shijie; Liu, Jun; Tong, Xiaohua; Li, Rongxing

    2016-06-01

    An assessment of Antarctic ice sheet surface mass balance from 2003 to 2015 has been carried out using a combination of ICESat data from 2003 to 2009 and CryoSat-2 data from 2010 to 2015. Both data sets are of L2 and are currently processed separately using different models. First, a repeat-track processing method that includes terms accounting for the trend and the first order fit of topography is applied to repeat-track measurements of all ICESat Campaigns. It uses the Least Squares fitting of the model to all observations in a box of 500 m x 500 m. The estimated trends in these boxes are then averaged inside a 30 km x 30 km cell. Similarly, the cells are used to estimate basin and ice sheet level surface elevation change trends. Mass balance calculating is performed at the cell level by multiplying the ice density by the volume change and then extended to the basin and the ice sheet level. Second, in CryoSat-2 data processing we applied a model within a cell of 5 km x 5 km considering that CryoSat-2 does not maintain repeated tracks. In this model the elevation trend, and a higher order topography are solved in an iterative way using the least squares technique. The mass change is computed at the cell level in the same way as the ICESat data. GIA correction is applied for both ICESat and CryoSat-2 estimates. Detailed information about the data processing, elevation and mass balance changes, and comparison with other studies will be introduced.

  5. Point measurements of mass balance of the Greenland Ice Sheet using precision vertical Global Positioning System (GPS) surveys

    NASA Astrophysics Data System (ADS)

    Hamilton, Gordon S.; Whillans, Ian M.

    2000-07-01

    Rates of ice sheet thickening or thinning in Greenland are measured using the coffee-can technique. This entails computing the difference in the vertical velocity of markers anchored in firn and the long-term rate of snow accumulation. The velocities are obtained from repeat surveys using the Global Positioning System (GPS). With corrections for densification and along-slope flow, this difference is the local mass balance. For two sites in western Greenland (Camp Century and a site just south of the EGIG line (Crawford Point)) results show ice sheet thinning. A third west Greenland site (inland from Upernavik) is close to balance. Two sites, Dye-2 in western Greenland and Summit, are thickening slowly.

  6. Present-day and future Antarctic ice sheet climate and surface mass balance in the Community Earth System Model

    NASA Astrophysics Data System (ADS)

    Lenaerts, Jan T. M.; Vizcaino, Miren; Fyke, Jeremy; van Kampenhout, Leo; van den Broeke, Michiel R.

    2016-02-01

    We present climate and surface mass balance (SMB) of the Antarctic ice 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 ice extent, large-scale atmospheric circulation and near-surface climate, but fails to simulate the recent expansion of Antarctic sea ice. The present-day Antarctic ice sheet SMB equals 2280 ± 131 {Gt year^{-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 scenario RCP8.5), CESM projects an increase of Antarctic ice sheet SMB of about 70 {Gt year^{-1}} per degree warming. This increase is driven by enhanced snowfall, which is partially counteracted by more surface melt and runoff along the ice 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.

  7. Balance Velocities of the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Joughin, Ian; Fahnestock, Mark; Ekholm, Simon; Kwok, Ron

    1997-01-01

    We present a map of balance velocities for the Greenland ice sheet. The resolution of the underlying DEM, which was derived primarily from radar altimetry data, yields far greater detail than earlier balance velocity estimates for Greenland. The velocity contours reveal in striking detail the location of an ice 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 balance map is useful for ice-sheet modelling, mass balance studies, and field planning.

  8. Changes in the Mass Balance of the Greenland Ice Sheet in a Warming Climate During 2003-2009

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Luthcke, Scott

    2010-01-01

    Mass changes of the Greenland ice sheet (GIS) derived from ICESat and GRACE data both show that the net mass loss from GIS during 2003-2009 is about 175 Gt/year, which contributes 0.5mm/yr global sea-level rise. The rate of mass loss has increased significantly since the 1990's when the GIS was close to mass balance. Even though the GIS was close to mass balance 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 ice 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 mass loss between the two periods, from increased melting and ice dynamics, increased by about 190 Gt/year while the mass gain, from increased precipitation and accumulation, increased by only about 15Gt/year. These ice changes occurred during a time when the temperature on GIS changed at rate of about 2K/decade. The distribution of elevation and mass 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 mass gains and losses among accumulation, melting, and ice discharge from outlet

  9. Analysis of Antarctic Ice-Sheet Mass Balance from ICESat Measurements

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Li, Jun; Robbins, John; Saba, Jack L.; Yi, Donghui

    2011-01-01

    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 mass. We find that for all reasonable nebular masses, these planetesimals contain a minimum of 3% water as ice by mass. The fraction of ice increases as the planetesimals increase in size and as the nebular mass 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?

  10. The dynamics of frazil ice formation in leads and its role in the mass balance of the sea ice pack.

    NASA Astrophysics Data System (ADS)

    Heorton, Harry; Feltham, Daniel

    2015-04-01

    Lead are cracks in sea ice that expose the ocean to the cold atmosphere resulting in the supercooling of the ocean and the formation of frazil ice crystals within the mixed layer. Here we present two studies of ice formation in leads: a single lead model focussing on frazil crystals of varying size within the vertical structure of the mixed layer; a new module explicitly describing frazil ice formation in leads incorporated into the Los Alamos sea ice model (CICE). Both studies consider the supercooling of the ocean, the concentration of frazil crystals within the ocean and their precipitation to the ocean surface as grease ice pushed against one of the lead edges by wind and water drag. The results from the single lead model show how the vertical structure of the mixed layer develops after the lead opens. Sensitivity studies reveal how changing wind speeds play the greatest role in the time taken to refreeze a lead. In the CICE model the new module slows down the refreezing of leads resulting in an longer period of frazil ice production when compared to the original model code. The fraction of frazil-derived sea ice increases from 10% to 50% with the inclusion of the new module. Ice formation rates are increased in areas of high ice concentration and thus has a greater impact within multiyear ice than in the marginal seas. The thickness of sea ice in the central Arctic increases by over 0.5 m whereas within the Antarctic it remains unchanged.

  11. Surface Mass Balance of the Greenland Ice Sheet: Connections to Mechanisms of Climate Variability on Decadal to Centennial Time Scales

    NASA Astrophysics Data System (ADS)

    Andres, H.; Peltier, W. R.

    2011-12-01

    The role of natural forcing in generating variability in the surface mass balance of the Greenland ice sheet (GrIS) remains unclear. Furthermore, mass variations in the GrIS over the past several centuries are poorly constrained. Until the impact of natural climate variations is better understood, it will be difficult to isolate the role anthropogenic greenhouse gases have had on GrIS-induced sea level rise, and to make predictions of GrIS changes in the future. To begin to address these issues, we have performed a suite of global, atmosphere-ocean general circulation model simulations of the past millennium. These runs are long enough to establish the connection between Arctic climate conditions and surface mass balance changes over the Greenland ice sheet over a wide range of timescales. We have created five historical simulations from years 850 to 2000 using the Community Climate System Model 3 and boundary conditions consistent with the Paleoclimate Modelling Intercomparison Project Phase 3. Over this preindustrial period, we have examined how average temperatures and total precipitation over regions of the GrIS varied with Arctic sea ice extent, NAO/NAM, Atlantic Meridional Overturning Circulation, Atlantic Multi-decadal Oscillation, ENSO, volcanic aerosol loading, and total solar irradiance changes. Overall, we find that variations on timescales longer than 30 years correlate well with several of these sources of climate variability, and that variations on shorter timescales are less well-connected. We also find that there are clear regional differences in the temperature and precipitation responses. Thus, in this presentation we focus on the sources of climate variability that we find to be most important to Greenland regional temperatures and precipitation in our suite of millennium simulations. Finally, we extended these simulations into the future using representative concentration pathways from the Coupled Model Intercomparison Project Phase 5. We

  12. Imaging spectroscopy to assess the composition of ice surface materials and their impact on glacier mass balance

    NASA Astrophysics Data System (ADS)

    Naegeli, Kathrin; Huss, Matthias; Damm, Alexander; de Jong, Rogier; Schaepman, Michael; Hoelzle, Martin

    2014-05-01

    The ice-albedo feedback plays a crucial role in various glaciological processes, but especially influences ice melt. Glacier surface albedo is one of the most important variables in the energy balance of snow and ice, but depends in a complicated way on many factors, such as cryoconite concentration, impurities due to mineral dust, soot or organic matter, grain size or ice surface morphology. Our understanding on how these various factors influence glacier albedo is still limited hindering a spatially and temporally explicit parameterization of energy balance models and requiring strongly simplified assumptions on actual albedo values. Over the last two decades, several studies have focused on glacier surface albedo using automatic in-situ weather stations in combination with radiation measurement setups or satellite images. Due to limitations of both approaches in matching either the spatial or the temporal length scale of glacier albedo, still fairly little is known about the state, changes and impact of glacier surface albedo in the Swiss Alps, although there are obvious changes in surface characteristics on most alpine glaciers over the last years. With use of the APEX (Airborne Prism EXperiment) image spectrometer, measurements of reflected radiation were acquired in high spatial and spectral resolution on Glacier de la Plaine Morte, Switzerland, to explicitly analyse the ice surface. In-situ radiometric measurements were acquired with an ASD field spectrometer in parallel to APEX overflights. These data are intended to be used for validation purposes as well as input data for the linear spectral unmixing analysis of the APEX data. Seasonal glacier mass balance is monitored since five years using the direct glaciological method. This contribution presents a first evaluation of the data collected in summer 2013. The obtained in-situ and airborne reflectance measurements were used in combination with a spectral mixture analysis (SMA) approach to assess the

  13. Geodetically-Constrained Glacial Isostatic Adjustment models of Antarctica: Implications for the Mass Balance of the West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

    Willis, M. J.; Wilson, T. J.; James, T. S.; Mazzotti, S.; Bevis, M. G.; Kendrick, E. C.; Brown, A. K.

    2010-12-01

    The IJ05 Antarctic ice sheet history is employed to drive a suite of approximately one thousand two-layered, laterally-homogeneous spherical Earth models and generate predictions of Antarctic crustal uplift due to glacial isostatic adjustment (GIA). GPS data collected between 1996 and 2010 on the flanks of the West Antarctic Rift System are used to produce bedrock uplift rates that are compared with the model predictions. The models that display the best fit to the data have softer, weaker upper-mantle viscosities than those published in many previous studies. A low viscosity upper-mantle is in agreement with seismic tomography that indicates that the upper mantle beneath much of West Antarctica has slower than average seismic shear-wave velocities. Best fit models further feature thin elastic lithospheres, a situation that is also corroborated by recent airborne gravity and seismic investigations. The best fit GIA models are used to generate crustal uplift rates and gravity changes that are larger than previously published models used to correct GRACE observations and infer Antarctic ice mass balance.The new models, which are the first GPS-constrained GIA corrections for GRACE in Antarctica, increases the ice-mass loss estimate for West Antarctica.

  14. Very high resolution modelling of the Surface Mass Balance of the Greenland Ice Sheet: Present day conditions and future prospects.

    NASA Astrophysics Data System (ADS)

    Mottram, Ruth; Aðalgeirsdóttir, Guðfinna; Boberg, Fredrik; Hesselbjerg Christensen, Jens; Bøssing Christensen, Ole; Langen, Peter; Rodehacke, Christian; Stendel, Martin; Yang, Shuting

    2014-05-01

    Recent experiments with the Regional Climate Model (RCM) HIRHAM5 have produced new surface mass balance (SMB) estimates at the unprecedented high horizontal resolution of 0.05 degrees (~5.5km). These simulations indicate a present day SMB of 347 ± 98 Gt/year over the whole ice sheet averaged over the period 1989 - 2012 driven by the ERA-Interim reanalysis dataset. We validate accumulation rates over the ice sheet using estimates from shallow firn cores to confirm the importance of resolution to accurate estimates of accumulation. Comparison with PROMICE and GC-Net automatic weather station observations shows the model represents present day climate and climate variability well when driven by the ERA-Interim reanalysis dataset. Comparison with a simulation at 0.25 degrees (~27km) resolution from the same model shows a significantly different calculated SMB over the whole ice sheet, largely due to changes in precipitation distribution over Greenland. The very high resolution requires a more sophisticated treatment of sub-grid scale processes in the snow pack including meltwater retention and refreezing and an enhanced albedo scheme. Our results indicate retention processes account for a significant proportion of the total surface budget based on a new parameterization scheme in the model. SMB projections, driven by the EC-Earth Global Climate Model (GCM) at the boundaries for the RCP 4.5 scenario indicate a declining surface mass balance over the 21st century with some compensation for warmer summer temperatures and enhanced melt in the form of increased precipitation. A cold bias in the driving GCM for present day conditions suggests that this simulation likely underestimates the change in SMB. However, the downscaled precipitation fields compare well with those in the reanalysis driven simulations. A soon-to-be complete simulation uses driving fields from the GCM running the RCP8.5 scenario.

  15. Interaction of katabatic wind and local surface mass balance at Scharffenbergbotnen Blue Ice Area, Antarctica

    NASA Astrophysics Data System (ADS)

    Zwinger, T.; Malm, T.; Schäfer, M.; Stenberg, R.; Moore, J. C.

    2015-04-01

    We model the wind causing the formation of a blue ice area in Scharffenbergbotnen valley, Antarctica, using the finite element code Elmer. The high resolution numerical simulations of the local wind flow from katabatic wind fronts show highly spatially variable wind impact patterns and good congruence between places of enhanced wind-impact and the blue ice area. The results were fortuitously confirmed by the destruction of a field camp located in a high wind speed area and its subsequent redistribution to low velocity areas. In addition we perform wind simulations on an altered glacier geometry that resembles the thicker ice cover at the Late Glacial Maximum (LGM). These simulations indicate that the pronounced spatial wind-impact patterns depend on present day geometry and did not occur during the LGM. This leads to the conclusion that the formation of the blue ice area that is situated more inside the valley of Scharffenbergbotnen started only after the lowering of the ice surface, later than the LGM. Experiments with smoothed surface topography suggest that detailed positions of the high wind regions and hence individual blue ice fields, may have varied as the ice sheet lowered. The experiments and the field observations are consistent with localized violent katabatic events, rather than synoptic scale storms, playing the dominant role in the formation and maintenance of this, and perhaps many blue ice areas.

  16. Satellite Observations of Blowing Snow in and Around Antarctica: Implications for Ice Sheet Mass Balance and Atmospheric Chemistry

    NASA Astrophysics Data System (ADS)

    Palm, S. P.; Yang, Y.; Marshak, A.

    2014-12-01

    Blowing snow in the polar regions is known to be important for a variety of reasons including ice sheet mass balance, atmospheric water vapor transport, interpretation of paleoclimate records and atmospheric chemistry. Over Antarctica, persistent katabatic winds produce extreme blowing snow events often covering 100,000 square kilometers or more and reaching heights of 300-400 meters. New techniques of blowing snow detection using active and passive satellite data are providing a new understanding of the frequency, magnitude and spatial coverage of blowing snow over and around the Antarctic continent. Current research is utilizing these methods to obtain a nearly 10 year climatology of blowing snow events over Antarctica and estimate the amount of mass being blown off the continent and sublimated into the atmosphere on an annual basis. In addition, recent research indicates that blowing snow over sea ice may be important in the process of transporting seal salt aerosol into the atmosphere where it is implicated in the production of bromine compounds that strongly influence many aspects of tropospheric chemistry.

  17. Extent of Low-accumulation 'Wind Glaze' Areas on the East Antarctic Plateau: Implications for Continental Ice Mass Balance

    NASA Technical Reports Server (NTRS)

    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.; Neumann, T.; Albert, M.; Winther, J.-G.

    2012-01-01

    Persistent katabatic winds form widely distributed localized areas of near-zero net surface accumulation on the East Antarctic ice 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 ice-sheet undulations and megadunes. Adjacent, leeward high-accumulation regions (isolated dunes) are generally smaller and do not compensate for the local low in surface mass balance (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 mass 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.

  18. Sensitivity of Greenland Ice Sheet surface mass balance to perturbations in sea surface temperature and sea ice cover: a study with the regional climate model MAR

    NASA Astrophysics Data System (ADS)

    Noël, B.; Fettweis, X.; van de Berg, W. J.; van den Broeke, M. R.; Erpicum, M.

    2014-10-01

    During recent summers (2007-2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North Atlantic Oscillation (NAO), favoring warmer atmospheric conditions than normal over the GrIS. Simultaneously, large anomalies in sea ice cover (SIC) and sea surface temperature (SST) were observed in the North Atlantic, suggesting a possible connection. To assess the direct impact of 2007-2012 SIC and SST anomalies on GrIS surface mass balance (SMB), a set of sensitivity experiments was carried out with the regional climate model MAR forced by ERA-Interim. These simulations suggest that perturbations in SST and SIC in the seas surrounding Greenland do not considerably impact GrIS SMB, as a result of the katabatic wind blocking effect. These offshore-directed winds prevent oceanic near-surface air, influenced by SIC and SST anomalies, from penetrating far inland. Therefore, the ice sheet SMB response is restricted to coastal regions, where katabatic winds cease. A topic for further investigation is how anomalies in SIC and SST might have indirectly affected the surface melt by changing the general circulation in the North Atlantic region, hence favoring more frequent warm air advection towards the GrIS.

  19. Troughs on Martian Ice Sheets: Analysis of Their Closure and Mass Balance

    NASA Technical Reports Server (NTRS)

    Fountain, A.; Kargel, J.; Lewis, K.; MacAyeal, D.; Pfeffer, T.; Zwally, J.

    2000-01-01

    At the Copenhagen workshop on Martian polar processes, Ralf Greve commented that the flow regime surrounding scarps and troughs of the Martian polar ice sheets cannot be modeled using traditional "plan view" ice-sheet models. Such models are inadequate because they typically use reduced equations that embody certain simplifications applicable only to terrestrial ice sheets where the upper ice 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 ice sheet, (b) the consequences of different flowlaws and ice compositions on scarp evolution and, in particular, scarp age, and (c) the role of dust and debris in scarp evolution.

  20. Troughs on Martian Ice Sheets: Analysis of Their Closure and Mass Balance

    NASA Astrophysics Data System (ADS)

    Fountain, A.; Kargel, J.; Lewis, K.; MacAyeal, D.; Pfeffer, T.; Zwally, J.

    2000-08-01

    At the Copenhagen workshop on Martian polar processes, Ralf Greve commented that the flow regime surrounding scarps and troughs of the Martian polar ice sheets cannot be modeled using traditional "plan view" ice-sheet models. Such models are inadequate because they typically use reduced equations that embody certain simplifications applicable only to terrestrial ice sheets where the upper ice 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 ice sheet, (b) the consequences of different flowlaws and ice compositions on scarp evolution and, in particular, scarp age, and (c) the role of dust and debris in scarp evolution.

  1. A downscaled 1 km dataset of daily Greenland ice sheet surface mass balance components (1958-2014)

    NASA Astrophysics Data System (ADS)

    Noel, B.; Van De Berg, W. J.; Fettweis, X.; Machguth, H.; Howat, I. M.; van den Broeke, M. R.

    2015-12-01

    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 mass balance (SMB) components over the narrow ablation zones, marginal outlet glaciers and neighbouring ice caps of the Greenland ice 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 ice 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 ice 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 ice 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

  2. Contemporary (1960-2012) Evolution of the Climate and Surface Mass Balance of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    van Angelen, J. H.; van den Broeke, M. R.; Wouters, B.; Lenaerts, J. T. M.

    2014-09-01

    We assess the contemporary (1960-2012) surface mass balance (SMB) of the Greenland ice sheet (GrIS), its individual components and trends. We use output of the high-resolution (11 km) regional atmospheric climate model (RACMO2), evaluated with automatic weather stations and GRACE data. A persistent negative North Atlantic oscillation index over the last 6 years resulted in the summertime advection of relatively warm continental air toward the GrIS. Added to the enhanced radiative forcing by increased CO2 levels, this has resulted in an increase in near-surface temperature of more than 2 K during 2007-2012 compared to 1960-1990. The associated decrease in albedo led to an extra absorption of shortwave radiation of ˜6 Wm-2 (11 %) in the summer months, which is the main driver of enhanced surface melting and runoff in recent years. From 1990 onward, we see a steady increase in meltwater runoff and an associated decrease in the SMB, accelerating after 2005, with the record low SMB year in 2010. Despite the fact that the GrIS was subject to the highest surface melt rates in 2012, relatively high accumulation rates prevented 2012 to set a record low SMB. In 2012, melt occurred relatively high on the ice sheet where melt water refreezes in the porous firn layer. Up to 2005, increased runoff was partly offset by increased accumulation rates. Since then, accumulation rates have decreased, resulting in low SMB values. Other causes of decreased SMB are the loss of firn pore space and decreasing refreezing rates in the higher ablation area. The GrIS has lost in total 1,800 ± 300 Gt of mass from surface processes alone since 1990 and about half of that in the last 6 years.

  3. Barrow real-time sea ice mass balance data: ingestion, processing, dissemination and archival of multi-sensor data

    NASA Astrophysics Data System (ADS)

    Grimes, J.; Mahoney, A. R.; Heinrichs, T. A.; Eicken, H.

    2012-12-01

    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 ice mass balance 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 ice and a humidity sensor. Each sensor has a unique specification and configuration. The data from multiple sensors are combined to generate sea ice data products. For example, ice thickness is calculated from the positions of the upper and lower ice surfaces, which are determined using data from downward-looking and upward-looking acoustic altimeters above and below the ice, 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

  4. Sea ice pCO2 dynamics and air-ice CO2 fluxes during the Sea Ice Mass Balance in the Antarctic (SIMBA) experiment - Bellingshausen Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Geilfus, N.-X.; Tison, J.-L.; Ackley, S. F.; Galley, R. J.; Rysgaard, S.; Miller, L. A.; Delille, B.

    2014-12-01

    Temporal evolution of pCO2 profiles in sea ice in the Bellingshausen Sea, Antarctica, in October 2007 shows physical and thermodynamic processes controls the CO2 system in the ice. During the survey, cyclical warming and cooling strongly influenced the physical, chemical, and thermodynamic properties of the ice cover. Two sampling sites with contrasting characteristics of ice and snow thickness were sampled: one had little snow accumulation (from 8 to 25 cm) and larger temperature and salinity variations than the second site, where the snow cover was up to 38 cm thick and therefore better insulated the underlying sea ice. We show that each cooling/warming event was associated with an increase/decrease in the brine salinity, total alkalinity (TA), total dissolved inorganic carbon (TCO2), and in situ brine and bulk ice CO2 partial pressures (pCO2). Thicker snow covers reduced the amplitude of these changes: snow cover influences the sea ice carbonate system by modulating the temperature and therefore the salinity of the sea ice cover. Results indicate that pCO2 was undersaturated with respect to the atmosphere both in the in situ bulk ice (from 10 to 193 μatm) and brine (from 65 to 293 μatm), causing the sea ice to act as a sink for atmospheric CO2 (up to 2.9 mmol m-2 d-1), despite supersaturation of the underlying seawater (up to 462 μatm).

  5. Assessing the Sensitivity of Satellite-Derived Estimates of Ice Sheet Mass Balance to Regional Climate Model Simulations of Snow Accumulation and Firn Compaction

    NASA Astrophysics Data System (ADS)

    Briggs, K.; Shepherd, A.; Horwath, M.; Horvath, A.; Nagler, T.; Wuite, J.; Muir, A.; Gilbert, L.; Mouginot, J.

    2015-12-01

    Surface mass balance (SMB) estimates from Regional Climate Models (RCMs) are fundamental for assessing and understanding ice sheet mass trends. Mass budget and altimetry assessments rely on RCMs both directly for estimates of the SMB contribution to the total mass trend, and indirectly for ancillary data in the form of firn compaction corrections. As such, mass balance assessments can be highly sensitive to RCM outputs and therefore their accuracy. Here we assess the extent to which geodetic measurements of mass balance are sensitive to RCM model outputs at different resolutions. We achieve this by comparing SMB dependent estimates of mass balance from the mass budget method and altimetry, with those from satellite gravimetry that are independent of SMB estimates. Using the outputs of the RACMO/ANT 2.3 model at 5.5 km and 27 km horizontal spatial resolution, we generate estimates of mass balance using the mass budget method and altimetry for the Western Palmer Land region of the Antarctic Peninsula between 2003 and 2014. We find a 19% increase in the long-term (1980 to 2014) mean annual SMB for the region when enhancing the model resolution to 5.5 km. This translates into an approximate 50% reduction in the total mass loss from 2003 to 2014 calculated with the mass budget method and a 15% increase in the altimetry estimate. The use of the enhanced resolution product leads to consistency between the estimates of mass loss from the altimetry and the mass budget method that is not observed with the coarser resolution product, in which estimates of cumulative mass fall beyond the relative errors. Critically, when using the 5.5 km product, we find excellent agreement, both in pattern and magnitude, with the independent estimate derived from gravimetry. Our results point toward the crucial need for high resolution SMB products from RCMs for mass balance assessments, particularly in regions of high mass turnover and complex terrain as found over the Antarctic Peninsula.

  6. Reducing Uncertainties in Greenland Surface Mass Balance Using IceBridge and ICESat Altimetry, GRACE Data and Regional Atmospheric Climate Model Outputs

    NASA Astrophysics Data System (ADS)

    Mohajerani, Y.; Sutterley, T. C.; Velicogna, I.; van den Broeke, M. R.; Fettweis, X.

    2015-12-01

    The mass of the Greenland Ice Sheet is undergoing rapid changes due to increase in surface melt and ice discharge. Considerable progress has been made to reduce the overall uncertainty of mass balance assessments. Here, we address the uncertainty in runoff production, which is of the largest remaining uncertainty in ice sheet mass balance. Runoff model outputs are difficult to evaluate due to a lack of in-situ monitoring networks. We document the uncertainty in runoff and how it varies spatially by comparing runoff products from different regional climate models (RCM) with two other sets of observations: 1) GRACE regional time series calculated using a least-squares mascon approach and corrected for regional ice discharge - with an emphasis on regions where ice dynamics is less significant: southwest and north Greenland; 2) At the smaller scale, NASA IceBridge and ICESat surface elevation change products, dh/dt, in the ablation zone to compare the observed volume changes with those predicted by RCMs. These two comparisons help evaluate how well seasonal melt and runoff are modeled by RCMs. The results help constrain uncertainties in present-day surface mass balance and runoff, as well as identify sources of RCM error. We also examine the constraints applied to the models (re-analysis data, albedo, energy budget, scheme to implement water retention, etc.) to gain insights into the processes responsible for the difference between models. Overall, we find substantial differences between MAR and RACMO results, and the results vary by region in terms of magnitude, timing and duration of surface melt. For instance, melt-water production and refreeze in the southwest are greater in RACMO, but total runoff is greater in MAR, and RACMO agrees better with GRACE. In the northeast, MAR predicts less runoff than RACMO and agrees better with GRACE. In the southeast, we find that the current version of MAR over-predicts runoff production. This work was funded by NASA

  7. Reconstruction of mass balance of Nevado Coropuna glaciers (Southern Peru) for Late Pleistocene, Little Ice Age and the present.

    NASA Astrophysics Data System (ADS)

    Ubeda, J.; Palacios, D.

    2009-04-01

    The Nevado Coropuna volcanic complex (15th 31'S-72 ° 39 ° W) is the quaternary stratovolcano northernmost of the central volcanic zone (CVZ) in the western flank of the Central Andes (Southern Peru). This consists in four adjacent volcanic buildings that are occupied over 5.100-5.700 masl by a system of glaciers covering an area of 47 Km2 in 2007 (Ubeda et al, 2008). The maximum expansion of glaciers during the Pleistocene affected an area of ~449 Km2, dropping to altitudes around 3.600-4800 m (Ubeda et al, 2007). In this work were mapped several hundreds of moraines which constitute a record of climate change since the last glacial maximum (LGM). Current glacier system is formed by dozen of glaciers descending slope down in all directions. Coropuna complex is an excellent laboratory for to investigate the control that climate change, tectonics and volcanism exert on the dynamics of glaciers, a scale of tens of years (by studying current glaciers) and also of tens of thousands of years (by analyzing the geomorphological evidence of its evolution in the past). Ubeda et al. (2008) analyzed the evolution of eighteen glaciers of Nevado Coropuna using indicators as surfaces and Equilibrium Line Altitudes (ELAs) of ice masses in 2007, 1986, 1955, Little the Ice Age (LIA) and Last Glacial Maximum (LGM). The glaciers were grouped into two sets: NE group (seven glaciers) and SE group (eleven glaciers). The work included statistical series of ELAs in each phase, estimates by Area x Altitud Balance Ratio (AABR) method, which was proposed by Osmaston (2005), in addition with estimates of timing (~17Cl36 Ka) and magnitude (~ 782-911 m) of ELA depression during LGM. The work included statistical series of ELAs in each phase, estimates by the method Area x Altitud Balance Ratio (AABR) proposed by Osmaston (2005), and in addition estimates of the timing (~17Cl36 Ka) and magnitude (~ 782-911 m) of ELA depression during LGM. The objective of this work is to estimate the current

  8. Parameterizations of daily temperature standard deviation for modeling ice sheet mass balances using a temperature-index method under paleoclimate conditions

    NASA Astrophysics Data System (ADS)

    Erokhina, Olga; Rogozhina, Irina

    2016-04-01

    A number of recent studies have suggested time-dependent parameterizations of daily temperature standard deviation for modelling surface mass balances of ice sheets and glaciers using a temperature-index method. These have been inferred from in-situ measurements and climate reanalysis data, which are only available on yearly to decadal time scales. To date, the existing literature has not explored their applicability to climate conditions that are different from those of today. This study presents an ensemble of simulations of the Greenland Ice Sheet's history since the Last Glacial Maximum to assess the performance of existing parameterizations of daily temperature standard deviation on millennial time scales. To limit the influence of the uncertainties arising from poorly constrained external and internal factors we adopt climate strategies of different complexities and a sensitivity analysis of ice sheet model parameters. Our study reveals that previously proposed parameterizations of daily temperature standard deviation have a limited performance during the deglaciation stage, failing to simulate the retreat of ice masses as suggested by geological reconstructions. In contrast multiple studies that use constant values of daily temperature standard deviation within the range of 4 to 5°C receive support from our analysis, implying that either the ice sheet model used is missing the fundamental physics necessary to capture complex processes associated with rapid deglaciation or the values of daily temperature standard deviation suggested by parameterizations based on present-day observations are too low to ensure the consistent Wisconsin-to-Holocene ice sheet retreat.

  9. Mass balance, meteorology, area altitude distribution, glacier-surface altitude, ice motion, terminus position, and runoff at Gulkana Glacier, Alaska, 1996 balance year

    USGS Publications Warehouse

    March, Rod S.

    2003-01-01

    The 1996 measured winter snow, maximum winter snow, net, and annual balances in the Gulkana Glacier Basin were evaluated on the basis of meteorological, hydrological, and glaciological data. Averaged over the glacier, the measured winter snow balance was 0.87 meter on April 18, 1996, 1.1 standard deviation below the long-term average; the maximum winter snow balance, 1.06 meters, was reached on May 28, 1996; and the net balance (from August 30, 1995, to August 24, 1996) was -0.53 meter, 0.53 standard deviation below the long-term average. The annual balance (October 1, 1995, to September 30, 1996) was -0.37 meter. Area-averaged balances 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 balance 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 ice-motion changes measured at three index sites document seasonal ice-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.

  10. Mass balance assessment using GPS

    NASA Technical Reports Server (NTRS)

    Hulbe, Christina L.

    1993-01-01

    Mass balance 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 ice can also be accurately positioned. Change in the monument's vertical position is a direct indicator of ice thickness change. Because the monument is not connected to the ice, its motion is due to both mass balance change and to the settling of firn as it densifies into ice. 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 Ice 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.

  11. A century of variation in the dependence of Greenland iceberg calving on ice sheet surface mass balance and regional climate change.

    PubMed

    Bigg, G R; Wei, H L; Wilton, D J; Zhao, Y; Billings, S A; Hanna, E; Kadirkamanathan, V

    2014-06-01

    Iceberg calving is a major component of the total mass balance of the Greenland ice sheet (GrIS). A century-long record of Greenland icebergs comes from the International Ice 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 mass balance (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-ice 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. PMID:24910517

  12. A century of variation in the dependence of Greenland iceberg calving on ice sheet surface mass balance and regional climate change

    PubMed Central

    Bigg, G. R.; Wei, H. L.; Wilton, D. J.; Zhao, Y.; Billings, S. A.; Hanna, E.; Kadirkamanathan, V.

    2014-01-01

    Iceberg calving is a major component of the total mass balance of the Greenland ice sheet (GrIS). A century-long record of Greenland icebergs comes from the International Ice 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 mass balance (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-ice 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. PMID:24910517

  13. Development of a multi-sensor elevation time series pole-ward of 86°S in support of altimetry validation and ice sheet mass balance studies

    NASA Astrophysics Data System (ADS)

    Studinger, M.; Brunt, K. M.; Casey, K.; Medley, B.; Neumann, T.; Manizade, S.; Linkswiler, M. A.

    2015-12-01

    In order to produce a cross-calibrated long-term record of ice-surface elevation change for input into ice sheet models and mass balance studies it is necessary to "link the measurements made by airborne laser altimeters, satellite measurements of ICESat, ICESat-2, and CryoSat-2" [IceBridge 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 IceBridge and ICESat-2 science teams have designed IceBridge 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 IceBridge 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 mass 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 ice sheet mass balance studies.

  14. Modelling the feedbacks between mass balance, ice flow and debris transport to predict the response to climate change of debris-covered glaciers in the Himalaya

    NASA Astrophysics Data System (ADS)

    Rowan, Ann V.; Egholm, David L.; Quincey, Duncan J.; Glasser, Neil F.

    2015-11-01

    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-ice surfaces. Debris-covered glaciers can persist well below the altitude that would be sustainable for clean-ice glaciers, resulting in much longer timescales of mass 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-ice surfaces, and yield conflicting results. We developed a numerical model that couples the flow of ice and debris and includes important feedbacks between debris accumulation and glacier mass balance. 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 mass loss when compared with estimates based on glacierised area. Since the Little Ice 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.

  15. Geodetic mass balance record with rigorous uncertainty estimates deduced from aerial photographs and lidar data - Case study from Drangajökull ice cap, NW Iceland

    NASA Astrophysics Data System (ADS)

    Magnússon, E.; Muñoz-Cobo Belart, J.; Pálsson, F.; Ágústsson, H.; Crochet, P.

    2016-01-01

    In this paper we describe how recent high-resolution digital elevation models (DEMs) can be used to extract glacier surface DEMs from old aerial photographs and to evaluate the uncertainty of the mass balance record derived from the DEMs. We present a case study for Drangajökull ice cap, NW Iceland. This ice cap covered an area of 144 km2 when it was surveyed with airborne lidar in 2011. Aerial photographs spanning all or most of the ice cap are available from survey flights in 1946, 1960, 1975, 1985, 1994 and 2005. All ground control points used to constrain the orientation of the aerial photographs were obtained from the high-resolution lidar DEM. The lidar DEM was also used to estimate errors of the extracted photogrammetric DEMs in ice- and snow-free areas, at nunataks and outside the glacier margin. The derived errors of each DEM were used to constrain a spherical semivariogram model, which along with the derived errors in ice- and snow-free areas were used as inputs into 1000 sequential Gaussian simulations (SGSims). The simulations were used to estimate the possible bias in the entire glaciated part of the DEM and the 95 % confidence level of this bias. This results in bias correction varying in magnitude between 0.03 m (in 1975) and 1.66 m (in 1946) and uncertainty values between ±0.21 m (in 2005) and ±1.58 m (in 1946). Error estimation methods based on more simple proxies would typically yield 2-4 times larger error estimates. The aerial photographs used were acquired between late June and early October. An additional seasonal bias correction was therefore estimated using a degree-day model to obtain the volume change between the start of 2 glaciological years (1 October). This correction was largest for the 1960 DEM, corresponding to an average elevation change of -3.5 m or approx. three-quarters of the volume change between the 1960 and the 1975 DEMs. The total uncertainty of the derived mass balance record is dominated by uncertainty in the volume

  16. Sea level rise from the Greenland Ice Sheet during the Eemian interglacial: Review of previous work with focus on the surface mass balance

    NASA Astrophysics Data System (ADS)

    Plach, Andreas; Hestnes Nisancioglu, Kerim

    2016-04-01

    The contribution from the Greenland Ice 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 mass balance. 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 mass balance. In addition, as a first step for future work, the surface mass balance 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.

  17. Satellite-derived, melt-season surface temperature of the Greenland Ice Sheet (2000-2005) and its relationship to mass balance

    USGS Publications Warehouse

    Hall, D.K.; Williams, R.S., Jr.; Casey, K.A.; DiGirolamo, N.E.; Wan, Z.

    2006-01-01

    Mean, clear-sky surface temperature of the Greenland Ice 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 ice 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 ice sheet; a reduction in area of the dry-snow facies would indicate a more-negative mass balance. 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. Copyright 2006 by the American Geophysical Union.

  18. Micromechanical Oscillating Mass Balance

    NASA Technical Reports Server (NTRS)

    Altemir, David A. (Inventor)

    1997-01-01

    A micromechanical oscillating mass balance 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 mass of the beam increases and the resonant frequency of the beam shifts, and the mass added is determined.

  19. Surface melt dominates Alaska glacier mass balance

    USGS Publications Warehouse

    Larsen Chris F; Burgess, E; Arendt, A.A.; O'Neel, Shad; Johnson, A.J.; Kienholz, C.

    2015-01-01

    Mountain glaciers comprise a small and widely distributed fraction of the world's terrestrial ice, yet their rapid losses presently drive a large percentage of the cryosphere's contribution to sea level rise. Regional mass balance 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 mass balance of −75 ± 11 Gt yr−1 (1994–2013). Our glacier sample is spatially well distributed, yet pervasive variability in mass balances obscures geospatial and climatic relationships. However, for the first time, these data allow the partitioning of regional mass balance by glacier type. We find that tidewater glaciers are losing mass at substantially slower rates than other glaciers in Alaska and collectively contribute to only 6% of the regional mass loss.

  20. Surface exposure chronology of the Waimakariri glacial sequence in the Southern Alps of New Zealand: Implications for MIS-2 ice extent and LGM glacial mass balance

    NASA Astrophysics Data System (ADS)

    Rother, Henrik; Shulmeister, James; Fink, David; Alexander, David; Bell, David

    2015-11-01

    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 ice 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 ice limit. We use a simple steady-state mass balance model to test the sensitivity of past glacial accumulation to various climatic parameters, and to evaluate possible climate scenarios capable of generating the ice 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 ice volume and downvalley ice 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

  1. Reconstruction of the Greenland ice sheet surface mass balance over 1900-2015 with the help of the regional climate MARv3.6 model

    NASA Astrophysics Data System (ADS)

    Fettweis, Xavier; Agosta, Cécile; Gallée, Hubert

    2016-04-01

    With the aim of studying the recent Greenland ice sheet (GrIS) Surface Mass Balance (SMB) decrease with respect to the last century, we have forced the regional climate MAR model (version 3.6) with the ERA-Interim (1979-2015), ERA-40 (1958-2001), NCEP1 (1948-2015), NCEP2 (1979-2015), JRA-55 (1958-2015), 20CRv2(c) (1880-2012) and ERA-20C (1900-2010) reanalysis. While all of these forcing products are reanalyses, MAR simulates differences in SMB over the common period. A temperature correction of +1°C (resp. -1°C) had notably to be applied to the MAR boundary conditions given that ERA-20C (resp. 20CRv2) is ~1° colder (resp. warmer) over Greenland than ERA-Interim data over 1980-2010. Comparisons with PROMICE daily temperature measurements valid these corrections. In most of regions, the SMB discrepancies between the different simulations are not significant except in the South-East where the maximum of precipitation occurs and where SMB measurements are missing. This suggests that uncertainties in the current SMB reconstruction remain and that observations are still needed. Comparisons with SMB measurements from the PROMICE data set, ice cores and satellite derived melt extent allows to select the best reanalysis forced data set. All of these simulations show that i) the period 1961-1990 usually chosen as reference for SMB and ice dynamics (stable ice sheet) over GrIS is a period when the SMB was abnormally high in respect to the last 120 years; ii) SMB has been significantly decreasing after this reference period due to increasing melt. Both ERA-20C and 20CRv2 forced simulations suggest a precipitation increase since the beginning of the last century and the ERA-20C forced simulation only suggests that SMB during the 1920-1930 warm period over Greenland was comparable with the SMB of the 2000's. Finally, the sensitivity of switching on the erosion of the snow by the wind in MARv3.6 over GrIS will be discussed.

  2. Greenland Ice Sheet: High-Elevation Balance and Peripheral Thinning.

    PubMed

    Krabill; Abdalati; Frederick; Manizade; Martin; Sonntag; Swift; Thomas; Wright; Yungel

    2000-07-21

    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 mass-balance of the Greenland Ice Sheet. Above 2000 meters elevation, the ice sheet is in balance 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 ice per year from the entire ice sheet, sufficient to raise sea level by 0.13 millimeter per year-approximately 7% of the observed rise. PMID:10903198

  3. Climate during the Last Glacial Maximum in the Wasatch Mountains Inferred from Glacier Mass-Balance and Ice-Flow Modeling

    NASA Astrophysics Data System (ADS)

    Bash, E. A.; Laabs, B. J.

    2006-12-01

    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 ice 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 ice extent to climatic changes, a physically based, two- dimensional numerical model of glacier mass balance and ice flow was applied to these valleys. The modeling approach allows the combined effects of temperature, precipitation and solar radiation on net mass balance 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

  4. Clouds enhance Greenland ice sheet mass loss

    NASA Astrophysics Data System (ADS)

    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.

    2015-04-01

    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 ice 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 mass balance 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 ice 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 ice 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 mass balance of the ice 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 mass 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 ice 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 ice sheet mass balance and global sea level rise.

  5. Glaciological constraints on current ice mass changes from modelling the ice sheets over the glacial cycles

    NASA Astrophysics Data System (ADS)

    Huybrechts, P.

    2003-04-01

    The evolution of continental ice sheets introduces a long time scale in the climate system. Large ice sheets have a memory of millenia, hence the present-day ice 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 mass-balance 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 ice mass changes is to model the past history of the ice sheets and their underlying beds over the glacial cycles. Such calculations assist to distinguish between the longer-term ice-dynamic evolution and short-term mass-balance 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 ice-sheet/lithosphere/bedrock models applied to the Antarctic and Greenland ice sheets. The simulations are forced by time-dependent boundary conditions derived from sediment and ice core records and are constrained by geomorphological and glacial-geological data of past ice sheet and sea-level stands. Current simulations suggest that the Greenland ice sheet is close to balance, while the Antarctic ice sheet is still losing mass, mainly due to incomplete grounding-line retreat of the West Antarctic ice sheet since the LGM. The results indicate that altimetry trends are likely dominated by ice thickness changes but that the gravitational signal mainly reflects postglacial rebound.

  6. A balanced water layer concept for subglacial hydrology in large scale ice sheet models

    NASA Astrophysics Data System (ADS)

    Goeller, S.; Thoma, M.; Grosfeld, K.; Miller, H.

    2012-12-01

    There is currently no doubt about the existence of a wide-spread hydrological network under the Antarctic ice sheet, which lubricates the ice base and thus leads to increased ice velocities. Consequently, ice models should incorporate basal hydrology to obtain meaningful results for future ice dynamics and their contribution to global sea level rise. Here, we introduce the balanced water layer concept, covering two prominent subglacial hydrological features for ice sheet modeling on a continental scale: the evolution of subglacial lakes and balance water fluxes. We couple it to the thermomechanical ice-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 ice sheet, resulting in a negative ice mass balance. Furthermore, we introduce an elementary parametrization of the water flux-basal sliding coupling and reveal the predominance of the ice loss through the resulting ice streams against the stabilizing influence of less hydrologically active areas. We point out, that established balance flux schemes quantify these effects only partially as their ability to store subglacial water is lacking.

  7. Glacier mass balance and runoff research in the U.S.A.

    USGS Publications Warehouse

    Mayo, L.R.

    1984-01-01

    Research on glacier mass balance began in the USA about 50 years ago. More complete studies of climate, snow and ice balance, and the hydrology of glaciers were initiated for the IGY in 1957 and the IHD in 1966. Investigations included the magnitude and geographic distribution of normal mass balance processes and unusual phenomena such as outbursting, accumulation of ice by freezing of water in firn, and ablation of glacier ice by volcanic activity and by calving. -from Author

  8. Geodetic mass balance record with rigorous uncertainty estimates deduced from aerial photographs and LiDAR data - case study from Drangajökull ice cap, NW-Iceland

    NASA Astrophysics Data System (ADS)

    Magnússon, E.; Belart, J. M. C.; Pálsson, F.; Ágústsson, H.; Crochet, P.

    2015-09-01

    In this paper we describe how recent high resolution Digital Elevation Models (DEMs) can be used as constraints for extracting glacier surface DEMs from old aerial photographs and to evaluate the uncertainty of the mass balance record derived from the DEMs. We present a case study for Drangajökull ice cap, NW-Iceland. This ice cap covered an area of 144 km2 when it was surveyed with airborne LiDAR in 2011. Aerial photographs spanning all or most of the ice cap are available from survey flights in 1946, 1960, 1975, 1985, 1994 and 2005. All ground control points used to constrain the orientation of the aerial photographs were obtained from the high resolution LiDAR DEM (2 m × 2 m cell size and vertical accuracy < 0.5 m). The LiDAR DEM was also used to estimate errors of the extracted photogrammetric DEMs in ice and snow free areas, at nunataks and outside the glacier margin. The derived errors of each DEM were used to constrain a spherical variogram model, which along with the derived errors in ice and snow free areas were used as inputs into 1000 Sequential Gaussian Simulations (SGSim). The simulations were used to estimate the possible bias in the entire glaciated part of the DEM. The derived bias correction, varying in magnitude between DEMs from 0.03 to 1.66 m (1946 DEM) was then applied. The simulation results were also used to calculate the 95 % confidence level of this bias, resulting in values between ±0.21 m (in 2005) and ±1.58 m (in 1946). Error estimation methods based on more simple proxies would typically yield 2-4 times larger error estimates. The aerial photographs used were acquired between late June and early October. An additional bias correction was therefore estimated using a degree day model to obtain the volume change between the start of two hydrological years (1 October). This correction corresponds to an average elevation change of ~ -3 m in the worst case for 1960, or about ~ 2/3 of volume change between the 1960 and the 1975 DEMs. The

  9. Greenland's Elastic and Viscoelastic Adjustments to Ice Mass Changes

    NASA Astrophysics Data System (ADS)

    Bevis, M. G.; Khan, S. A.; Brown, A.; Willis, M. J.; Sasgen, I.

    2014-12-01

    We present the latest geodetic time series from the Greenland GPS Network (GNET), assess the relative importance of instantanous elastic and delayed viscoelastic adjustments to the crustal displacement field, and discuss the complementary nature of GNET's and GRACE's sensing of ice mass changes. Clearly the most robust and best informed inversions for modern ice mass changes will utilize the GNET displacement history, GRACE's mass fields, and ice surface height changes derived from repeat altimetry and repeat optical DEMs. These inversions will also be guided by measured changes in ice flow rates, surface mass balance estimates from numerical weather models, and models of glacial isostatic adjustment. Designing an optimal inverse method requires us to asses and exploit the strengths of each class of observation in order to offset the main weaknesses in the others. GPS and GRACE are the only techniques that directly sense ice mass changes, and we present an analysis of accerations in both time series which demonstrates that GNET senses the lateral variability of ice mass accelerations in SE Greenland with much better resolution than does GRACE. When an optimal model for modern ice mass changes is achieved, and the associated elastic adjustments are subtracted from the GPS displacements, the residual displacements can be used to characterize visoelastic adjusments. These should promote an improved 'PGR correction' for GRACE.

  10. Estimation of the Greenland ice sheet surface mass balance contribution to future sea level rise using the regional climate model MAR (Arne Richter Award for Outstanding Young Scientists Lecture)

    NASA Astrophysics Data System (ADS)

    Fettweis, Xavier; Gallée, Hubert; van den Broeke, Michiel; Tedesco, Marco; van Angelen, Jan; Lenaerts, Jan; Erpicum, Michel

    2013-04-01

    With the aim of estimating the sea level rise (SLR) coming from Surface Mass Balance (SMB) changes over the Greenland ice sheet (GrIS), we report future projections obtained with the regional climate model MAR, forced by outputs of three CMIP5 General Circulation Models (GCMs). Our results indicate that in warmer climates, the mass gained due to increased winter snowfall over GrIS does not compensate the mass lost through increased meltwater run-off in summer. All the MAR projections shows similar non-linear melt increases with rising temperatures as a result of the positive surface albedo feedback, because no change is projected in the general atmospheric circulation over Greenland. Nevertheless, MAR exhibits a large range in its future projections. By coarsely estimating the GrIS SMB changes from CMIP5 GCMs outputs, we show that the uncertainty coming from the GCM-based forcing represents about half of projected SMB changes. In 2100, the CMIP5 ensemble mean projects a SLR, resulting from a GrIS SMB decrease, estimated to be 4±2 cm and 9±4 cm for the RCP 4.5 and RCP 8.5 scenarios, respectively. However, these future projections do not consider the positive melt-elevation feedback. Sensitivity MAR experiments using perturbed ice sheet topographies consistent with the projected SMB changes highlight the importance of coupling climate models to an ice sheet model. Such a coupling will allow to consider the future response of both surface processes and ice-dynamic changes, and their mutual feedbacks to rising temperatures.

  11. The Effect of Antarctic Ice Mass Changes on Crustal Motion and Global Geodetic Observables

    NASA Technical Reports Server (NTRS)

    James, T. S.; Ivins, E. R.

    1995-01-01

    Glaciological estimates of the present-day ice mass balance of Antarctica vary widely, indicating the need for additional data to constrain mass-balance models. For example, recent studies find both a positive and a negative mass balance of the Antarctic ice sheet. Analysis of studies suggest that observations of present-day crustal motion, as obtained from a GPS survey could assist in defining models.

  12. Perennial water stratification and the role of basal freshwater flow in the mass balance of the Ward Hunt Ice Shelf, Canadian High Arctic

    SciTech Connect

    Jefferies, M.O.

    1992-03-01

    A pronounced perennial water stratification in Disraeli Fjord behind the Ward Hunt Ice Shelf on the north coast of Ellesmere Island is described. The ice shelf acts as a hanging dam at the mouth of the fjord and minimizes mixing between inflowing meltwater runoff and the seawater. Consequently, a 4 1 -m-deep layer of low salinity water, interposed between a 2- to 3-m-thick fjord surface ice layer and deeper seawater, is impounded behind the ice shelf. Highly negative delta 18O Values and high tritium activity in the low salinity water indicate it is derived primarily from snow-meltwater. Highly negative delta 18O values and high tritium values in a 5-m-thick basal ice layer in Hobson's Choice Ice Island, which broke off the East Ward Hunt Ice Shelf in 1982-83, might be evidence that basal accretion from freshwater flowing out of Disraeli Fjord below the ice shelf occurred prior to the calving. Using the known chronology of tritium occurrence in precipitation since 1952 and the measured levels in the basal ice, mean basal accretion rates of 96-141 mm yr-1 (water equivalent, w.e.) are calculated. The record of ablation and accumulation at the surface of the East Ward Hunt Ice Shelf for the period 1966-1982 shows an accumulated loss at the surface of 1.26 m (w.e.) at a mean annual rate of 74 mm yr-1. Therefore, despite many consecutive warm summers with considerable surface melting and runoff, the calculated basal accretion exceeds the surface loss and the ice shelf has increased, or at least maintained, its thickness. The thickening has been possible because of the feedback system created by the location of the ice shelf across the mouth of the fjord, the resultant water stratification and the outflow of freshwater below the ice shelf.

  13. Balance of the West Antarctic Ice Sheet

    NASA Technical Reports Server (NTRS)

    2002-01-01

    For several decades, measurements of the West Antarctic Ice Sheet showed it to be retreating rapidly. But new data derived from satellite-borne radar sensors show the ice sheet to be growing. Changing Antarctic ice 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 ice sheet collapsed into the sea. Do these new measurements signal the end of the ice sheet's 10,000-year retreat? Or, are these new satellite data simply much more accurate than the sparse ice core and surface measurements that produced the previous estimates? Another possibility is that the ice accumulation may simply indicate that the ice 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 ice speed. The fast-moving central ice streams are shown in red. Slower tributaries feeding the ice 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 ice streams. Reference: Ian Joughin and Slawek Tulaczyk Science Jan 18 2002: 476-480. Image courtesy RADARSAT Antarctic Mapping Project

  14. Numerical modeling of late Glacial Laurentide advance of ice across Hudson Strait: Insights into terrestrial and marine geology, mass balance, and calving flux

    USGS Publications Warehouse

    Pfeffer, W.T.; Dyurgerov, M.; Kaplan, M.; Dwyer, J.; Sassolas, C.; Jennings, A.; Raup, B.; Manley, W.

    1997-01-01

    A time-dependent finite element model was used to reconstruct the advance of ice from a late Glacial dome on northern Quebec/Labrador across Hudson Strait to Meta Incognita Peninsula (Baffin Island) and subsequently to the 9.9-9.6 ka 14C Gold Cove position on Hall Peninsula. Terrestrial geological and geophysical information from Quebec and Labrador was used to constrain initial and boundary conditions, and the model results are compared with terrestrial geological information from Baffin Island and considered in the context of the marine event DC-0 and the Younger Dryas cooling. We conclude that advance across Hudson Strait from Ungava Bay to Baffin Island is possible using realistic glacier physics under a variety of reasonable boundary conditions. Production of ice flux from a dome centered on northeastern Quebec and Labrador sufficient to deliver geologically inferred ice thickness at Gold Cove (Hall Peninsula) appears to require extensive penetration of sliding south from Ungava Bay. The discharge of ice into the ocean associated with advance and retreat across Hudson Strait does not peak at a time coincident with the start of the Younger Dryas and is less than minimum values proposed to influence North Atlantic thermohaline circulation; nevertheless, a significant fraction of freshwater input to the North Atlantic may have been provided abruptly and at a critical time by this event.

  15. Mass balance study of gravitational mass movements in proglacial systems

    NASA Astrophysics Data System (ADS)

    Rohn, Joachim; Vehling, Lucas; Moser, Michael

    2013-04-01

    In the framework of the DFG joint research project PROSA (high resoluted measurements of morphodynamics in rapidly changing PROglacial Systems of the Alps), mass movements are investigated geotechnically and process rates will be determined. As result, the actual mass balance for gravitational mass movements will be investigated exemplarily in an alpine glacier foreland in this PROSA sub-project. Alpine glacier forelands are defined as the area between the edge of the glacier and the moraines of the latest maximum in 1850. Since then, the region has become ice free due to the retreat of the glaciers. Because of this recent development, the glacier foreland differs considerably from the surrounding landscape and exhibits a rapid morphodynamic development. Mass movements like landslides and rock falls contribute a remarkable portion to total sediment transport in this area. As study area the region between Gepatschferner and Gepatsch backwater was choosen. The study area encompasses 62,5 km², lies at altitudes between 1759 and 3539 m a.s.l. and around 30 % are covered by glacier. Basic prerequisite is the geotechnical inventory-taking including the production of a geotechnical map. All mass balance studies for gravitational mass movements will base on this data collection. Short term behaviour during extreme meteorological events will be investigated as well, as the long term behaviour of the alpine slopes. The results of repeated high-resolution airborne laser scanning will contribute to a complete area-wide detection of surface changes. Detailed periodical terrestrial laser scanning of steep rock walls and their scree cones, as well as of slopes with soft rock will complete the data set. Spot tests with nets collecting the rock fall material, constructed on elected scree cones, allow the control and verification of the collected data. Mass movements in hard rock apart from rock fall processes, like rock creep, rock sliding and sagging will be monitored

  16. Juneau Icefield Mass Balance Program 1946-2011

    NASA Astrophysics Data System (ADS)

    Pelto, M.; Kavanaugh, J.; McNeil, C.

    2013-05-01

    The mass balance records of the Lemon Creek Glacier and Taku Glacier observed by the Juneau Icefield Research Program are the longest continuous glacier mass balance data sets in North America. On Taku Glacier annual mass balance averaged +0.40 m a-1 from 1946-1985 and -0.08 m a-1 from 1986-2011. The recent mass balance decline has resulted in the cessation of the long term thickening of the glacier. Mean annual mass balance on Lemon Creek Glacier has declined from -0.30 m a-1 for the 1953-1985 period to -0.60 m a-1 during the 1986-2011 period. The overall mass balance change is -26.6 m water equivalent, a 29 m of ice thinning over the 55 yr. Probing transects above the transient snow line (TSL) indicate a consistent balance gradient from year to year. Observations of the rate of summer TSL rise on Lemon Creek and Taku Glacier indicate a comparatively consistent rate of 3.8 to 4.1 m d-1. The relationship between TSL on Lemon Creek and Taku Glacier to other Juneau Icefield glaciers, Norris, Mendenhall, Herbert, and Eagle, is strong with correlations exceeding 0.82 in all cases. doi:10.5065/D6NZ85N3

  17. 50 years of mass balance observations at Vernagtferner, Eastern Alps

    NASA Astrophysics Data System (ADS)

    Braun, Ludwig; Mayer, Christoph

    2016-04-01

    The determination and monitoring of the seasonal and annual glacier mass balances of Vernagtferner, Austria, started in 1964 by the Commission of Glaciology, Bavarian Academy of Sciences. Detailed and continuous climate- and runoff measurements complement this mass balance 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 Ice Age in 1845, the geodetic glacier volume balances cover a time span of almost 170 years. The 50 years of glacier mass balance and 40 years of water balance 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 ice dynamics. The direct mass balance observations cover not only the period of alpine-wide strong glacier mass 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 mass 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 Ice Age.

  18. 14 CFR 27.659 - Mass balance.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Mass balance. 27.659 Section 27.659... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 Mass balance. (a) The rotors... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the mass...

  19. 14 CFR 27.659 - Mass balance.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Mass balance. 27.659 Section 27.659... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 Mass balance. (a) The rotors... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the mass...

  20. 14 CFR 23.659 - Mass balance.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Mass balance. 23.659 Section 23.659 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... Surfaces § 23.659 Mass balance. The supporting structure and the attachment of concentrated mass...

  1. 14 CFR 23.659 - Mass balance.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Mass balance. 23.659 Section 23.659 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... Surfaces § 23.659 Mass balance. The supporting structure and the attachment of concentrated mass...

  2. 14 CFR 29.659 - Mass balance.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Mass balance. 29.659 Section 29.659... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 Mass balance. (a) The rotor... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the mass...

  3. 14 CFR 29.659 - Mass balance.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Mass balance. 29.659 Section 29.659... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 Mass balance. (a) The rotor... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the mass...

  4. 14 CFR 29.659 - Mass balance.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Mass balance. 29.659 Section 29.659... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 Mass balance. (a) The rotor... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the mass...

  5. 14 CFR 23.659 - Mass balance.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Mass balance. 23.659 Section 23.659 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... Surfaces § 23.659 Mass balance. The supporting structure and the attachment of concentrated mass...

  6. 14 CFR 27.659 - Mass balance.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Mass balance. 27.659 Section 27.659... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 Mass balance. (a) The rotors... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the mass...

  7. 14 CFR 23.659 - Mass balance.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Mass balance. 23.659 Section 23.659 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... Surfaces § 23.659 Mass balance. The supporting structure and the attachment of concentrated mass...

  8. 14 CFR 23.659 - Mass balance.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Mass balance. 23.659 Section 23.659 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... Surfaces § 23.659 Mass balance. The supporting structure and the attachment of concentrated mass...

  9. 14 CFR 29.659 - Mass balance.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Mass balance. 29.659 Section 29.659... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 Mass balance. (a) The rotor... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the mass...

  10. 14 CFR 27.659 - Mass balance.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Mass balance. 27.659 Section 27.659... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 Mass balance. (a) The rotors... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the mass...

  11. 14 CFR 29.659 - Mass balance.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Mass balance. 29.659 Section 29.659... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 Mass balance. (a) The rotor... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the mass...

  12. 14 CFR 27.659 - Mass balance.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Mass balance. 27.659 Section 27.659... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 Mass balance. (a) The rotors... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the mass...

  13. Mass balancing of hollow fan blades

    NASA Technical Reports Server (NTRS)

    Kielb, R. E.

    1986-01-01

    A typical section model is used to analytically investigate the effect of mass balancing as applied to hollow, supersonic fan blades. A procedure to determine the best configuration of an internal balancing mass 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 balancing mass. The addition of an optimized balancing mass is shown to stabilize the blade at the design condition.

  14. Modeling interactions between Antarctic Instability and Surface Mass Balance.

    NASA Astrophysics Data System (ADS)

    Ritz, Catherine; Agosta, Cecile; Peyaud, Vincent; Durand, Gael; Fettweis, Xavier; Favier, Vincent; Gallée, Hubert

    2015-04-01

    In the context of future global warming, Antarctic contribution to sea level rise (SLR) depends on several processes leading to opposite impacts. First, under a warming climate, precipitation is supposed to increase, inducing a plausible negative impact on SLR. Contrary to the Greenland ice sheet case, ablation should stay a marginal process at least on grounded ice. Second, oceanic warming and/or surface ponding on ice shelves may trigger a Marine Ice Sheet Instability by reducing the backforce they exert on outlet glaciers. Once engaged on such a self-entertained retreat a large positive contribution to SLR may be expected. This dynamic process is already going on in the Admundsen sea sector. Although these two processes (surface mass balance -- SMB -- and ice dynamics) have been modeled separately to infer sea level contribution, little work has been done to study their interactions. In this presentation we focus on how grounding line retreat can affect estimation of SMB in the future and the related contribution to sea level change. To evaluate the shift of precipitation pattern while the steep surface slope region migrates inward due to the grounding line retreat, we simulate surface mass balance on various surface topographies of the Antarctic ice sheet. Each ice sheet topography is obtained with an ice sheet model (GRISLI) in which grounding line retreat is parameterized according to glaciological considerations. Because we are looking at coastal changes, a high resolution is needed for the atmospheric model and here we use the regional circulation model MAR with a resolution of 40 km. The preliminary results show that the topographic change induces a shift in the precipitation pattern as high accumulation regions tend to follow the slope break at the ice sheet / shelf transition. This affects the calculation of total SMB on the grounded ice sheet (and sea level contribution) and its amplitude is related to the amplitude of the retreat. In our simulations

  15. Ice flow dynamics and mass loss of Totten Glacier, East Antarctica, from 1989 to 2015

    NASA Astrophysics Data System (ADS)

    Li, Xin; Rignot, Eric; Mouginot, Jeremie; Scheuchl, Bernd

    2016-06-01

    Totten Glacier has the largest ice discharge in East Antarctica and a basin grounded mostly below sea level. Satellite altimetry data have revealed ice thinning in areas of fast flow. Here we present a time series of ice velocity measurements spanning from 1989 to 2015 using Landsat and interferometric synthetic-aperture radar data, combined with ice thickness from Operation IceBridge, and surface mass balance from Regional Atmospheric Climate Model. We find that the glacier speed exceeded its balance speed in 1989-1996, slowed down by 11 ± 12% in 2000 to bring its ice flux in balance with accumulation (65 ± 4 Gt/yr), then accelerated by 18 ± 3% until 2007, and remained constant thereafter. The average ice mass loss (7 ± 2 Gt/yr) is dominated by ice dynamics (73%). Its acceleration (0.6 ± 0.3 Gt/yr2) is dominated by surface mass balance (80%). Ice velocity apparently increased when ocean temperature was warmer, which suggests a linkage between ice dynamics and ocean temperature.

  16. Estimates of Regional Equilibrium Line Altitudes and Net Mass Balance from MODIS Imagery

    NASA Astrophysics Data System (ADS)

    Shea, J. M.; Menounos, B.; Moore, R. D.

    2011-12-01

    Glacier mass balance is a key variable used to assess the health of glaciers and ice sheets. Estimates of glacier mass balance are required to model the dynamic response of glaciers and ice sheets to climate change, estimate sea-level contribution from surface melt, and document the response of glaciers to climate forcing. Annually resolved estimates of regional mass balance for mountain ranges is often inferred from a sparse network of ground-based measurements of mass balance for individual glaciers. Given that net mass balance is highly correlated with the annual equilibrium line altitude (ELA), we develop an automated approach to estimate the ELA, and by inference net mass balance, on large glaciers and icefields using MODIS 250 m imagery (MOD02QKM). We discriminate areas of bare ice and snow/firn using the product of MODIS' red (0.620 - 0.670 μ m) and near infrared (0.841 - 0.876 μ m) bands. To assess the skill in estimating glacier ELAs, we compare ELAs derived from (1) manual delineation and (2) unsupervised classification of the band product to ground-based observations of ELA and net mass balance at seven long term mass-balance monitoring sites in western North America (Gulkana, Wolverine, Lemon Creek, Taku, Place, Peyto, and South Cascade). Spatial and temporal variations in MODIS-derived ELAs provide an opportunity to validate regional mass-balance models, estimate surface melt contributions to sea-level rise, and examine the cryospheric response to climate change.

  17. Constraining the margins of Neoproterozoic ice masses: depositional signature, palaeoflow and glaciodynamics

    NASA Astrophysics Data System (ADS)

    Busfield, Marie; Le Heron, Daniel

    2016-04-01

    The scale and distribution of Neoproterozoic ice masses remains poorly understood. The classic Snowball Earth hypothesis argues for globally extensive ice sheets, separated by small ocean refugia, yet the positions of palaeo-ice sheet margins and the extent of these open water regions are unknown. Abundant evidence worldwide for multiple cycles of ice advance and recession is suggestive of much more dynamic mass balance changes than previously predicted. Sedimentological analysis enables an understanding of the changing ice margin position to be gained through time, in some cases allowing it to be mapped. Where the maximum extent of ice advance varies within a given study area, predictions can also be made on the morphology of the ice margin, and the underlying controls on this morphology e.g. basin configuration. This can be illustrated using examples from the Neoproterozoic Kingston Peak Formation in the Death Valley region of western USA. Throughout the Sperry Wash, northern Kingston Range and southern Kingston Range study sites the successions show evidence of multiple cycles of ice advance and retreat, but the extent of maximum ice advance is extremely variable, reaching ice-contact conditions at Sperry Wash but only ice-proximal settings in the most distal southern Kingston Range. The overall advance is also much more pronounced at Sperry Wash, from ice-distal to ice-contact settings, as compared to ice-distal to ice-proximal settings in the southern Kingston Range. Therefore, the position of the ice margin can be located at the Sperry Wash study site, where the more pronounced progradation is used to argue for topographically constrained ice, feeding the unconstrained shelf through the northern into the southern Kingston Range. This raises the question as to whether Neoproterozoic ice masses could be defined as topographically constrained ice caps, or larger ice sheets feeding topographically constrained outlet glaciers.

  18. Ice Mass Fluctuations and Earthquake Hazard

    NASA Technical Reports Server (NTRS)

    Sauber, J.

    2006-01-01

    In south central Alaska, tectonic strain rates are high in a region that includes large glaciers undergoing ice 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 ice elevation decreases from 1-3 meters/year (see summary and references in Molnia, 2005). The elastic response of the solid Earth to this ice mass 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 ice mass 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) ice 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 ice elevation changes [Sauber et al., 2005, Muskett et al., 2005]. Since we are interested in evaluating the effect of ice 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 ice mass fluctuations altered the seismic rate of background seismicity. Although we primarily focus on

  19. Energy and Mass Balance At Gran Campo Nevado, Patagonia, Chile

    NASA Astrophysics Data System (ADS)

    Schneider, C.; Kilian, R.; Casassa, G.

    The Gran Campo Nevado (GCN) Ice Cap on Peninsula Muñoz Gamero, Chile, is lo- cated in the southernmost part of the Patagonian Andes at 53S. It comprises an ice cap and numerous outlet glaciers which mostly end in proglacial lakes at sea level. The total ice covered area sums up to approximately 250 km2. GCN forms the only major ice 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 ice mass from the accumulation area of the GCN Ice 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 mass balance 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 balance 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 balance. Since high cloud cover rates prevail, air tempera- ture is the key factor for the energy balance of the glacier. Despite high rain fall rates, energy input from rain fall is of only minor importance to the overall energy balance. From the energy balance computed, it was possible to derive summer-time degree-day factors for Glaciar Lengua. With data from the nearby

  20. Miniature Piezoelectric Macro-Mass Balance

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart; Trebi-Ollennu, Ashitey; Bonitz, Robert G.; Bar-Cohen, Yoseph

    2010-01-01

    Mass balances usually use a strain gauge that requires an impedance measurement and is susceptible to noise and thermal drift. A piezoelectric balance can be used to measure mass directly by monitoring the voltage developed across the piezoelectric balance, which is linear with weight or it can be used in resonance to produce a frequency change proportional to the mass change (see figure). The piezoelectric actuator/balance is swept in frequency through its fundamental resonance. If a small mass is added to the balance, the resonance frequency shifts down in proportion to the mass. By monitoring the frequency shift, the mass can be determined. This design allows for two independent measurements of mass. 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 mass is added to the plate, the piezoelectrics are stressed, causing them to produce a voltage that is proportional to the mass and acceleration. In addition, a change in mass 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 mass and acceleration. Alternatively, the acceleration could be used to force the mass on the plate, and the inertial effects of the mass on the plate would produce a shift in the resonance frequency with the change in frequency related to the mass change. Three prototypes of the mass balance mechanism were developed. These macro-mass balances each consist of a solid base and an APA 60 Cedrat flextensional piezoelectric actuator supporting a measuring plate. A similar structure with 3 APA

  1. Improving Mass Balance Modeling of Benchmark Glaciers

    NASA Astrophysics Data System (ADS)

    van Beusekom, A. E.; March, R. S.; O'Neel, S.

    2009-12-01

    The USGS monitors long-term glacier mass balance at three benchmark glaciers in different climate regimes. The coastal and continental glaciers are represented by Wolverine and Gulkana Glaciers in Alaska, respectively. Field measurements began in 1966 and continue. We have reanalyzed the published balance time series with more modern methods and recomputed reference surface and conventional balances. Addition of the most recent data shows a continuing trend of mass loss. We compare the updated balances to the previously accepted balances and discuss differences. Not all balance quantities can be determined from the field measurements. For surface processes, we model 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 modernize the traditional degree-day model as well as derive new degree-day factors in an effort to closer match the balance time series and thus better predict the future state of the benchmark glaciers. For subsurface processes, we model the refreezing of meltwater for internal accumulation. We examine the sensitivity of the balance time series to the subsurface process of internal accumulation, with the goal of determining the best way to include internal accumulation into balance estimates.

  2. Juneau Icefield Mass Balance Program 1946-2011

    NASA Astrophysics Data System (ADS)

    Pelto, M.; Kavanaugh, J.; McNeil, C.

    2013-11-01

    The annual surface mass balance records of the Lemon Creek Glacier and Taku Glacier observed by the Juneau Icefield Research Program are the longest continuous glacier annual mass balance data sets in North America. Annual surface mass balance (Ba) measured on Taku Glacier averaged +0.40 m a-1 from 1946-1985, and -0.08 m a-1 from 1986-2011. The recent annual mass balance decline has resulted in the cessation of the long-term thickening of the glacier. Mean Ba on Lemon Creek Glacier has declined from -0.30 m a-1 for the 1953-1985 period to -0.60 m a-1 during the 1986-2011 period. The cumulative change in annual surface mass balance is -26.6 m water equivalent, a 29 m of ice thinning over the 55 yr. Snow-pit measurements spanning the accumulation zone, and probing transects above the transient snow line (TSL) on Taku Glacier, indicate a consistent surface mass balance gradient from year to year. Observations of the rate of TSL rise on Lemon Creek Glacier and Taku Glacier indicate a comparatively consistent migration rate of 3.8 to 4.1 m d-1. The relationship between TSL on Lemon Creek Glacier and Taku Glacier to other Juneau Icefield glaciers (Norris, Mendenhall, Herbert, and Eagle) is strong, with correlations exceeding 0.82 in all cases. doi:10.5065/D6NZ85N3

  3. Comparison of glaciological and geodetic mass balance at Urumqi Glacier No. 1, Tian Shan, Central Asia

    NASA Astrophysics Data System (ADS)

    Wang, Puyu; Li, Zhongqin; Li, Huilin

    2016-04-01

    Glaciological and geodetic measurements are two methods to determine glacier mass balances. The mass balance of Urumqi Glacier No. 1 has been measured since 1959 by the glaciological method using ablation stakes and snowpits, except during the period 1967-1979 when the observations were interrupted. Moreover, topographic surveys have been carried out at various time intervals since the beginning of the glacier observations. Therefore, glacier volume changes are calculated by comparing topographic maps of different periods during nearly 50 years. Between 1962 and 2009, Urumqi Glacier No. 1 lost an ice volume of 29.51×106 m3, which corresponds to a cumulative ice thickness loss of 8.9 m and a mean annual loss of 0.2 m. The results are compared with glaciological mass balances over the same time intervals. The differences are 2.3%, 2.8%, 4.6%, 4.7% and 5.9% for the period 1981-86, 1986-94, 1994-2001, 2001-06 and 2006-09, respectively. For the mass balance measured with the glaciological method, the systematic errors accumulate linearly with time, whereas the errors are random for the geodetic mass balance. The geodetic balance is within the estimated error of the glaciological balance. In conclusion, the geodetic and glaciological mass balances are of high quality and therefore, there is no need to calibrate the mass balance series of Urumqi Glacier No. 1.

  4. The climatic mass balance of Svalbard glaciers: a 10-year simulation with a coupled atmosphere-glacier mass balance model

    NASA Astrophysics Data System (ADS)

    Aas, Kjetil S.; Dunse, Thorben; Collier, Emily; Schuler, Thomas V.; Berntsen, Terje K.; Kohler, Jack; Luks, Bartłomiej

    2016-05-01

    In this study we simulate the climatic mass balance of Svalbard glaciers with a coupled atmosphere-glacier model with 3 km grid spacing, from September 2003 to September 2013. We find a mean specific net mass balance of -257 mm w.e. yr-1, corresponding to a mean annual mass loss of about 8.7 Gt, with large interannual variability. Our results are compared with a comprehensive set of mass balance, meteorological, and satellite measurements. Model temperature biases of 0.19 and -1.9 °C are found at two glacier automatic weather station sites. Simulated climatic mass balance is mostly within about 100 mm w.e. yr-1 of stake measurements, and simulated winter accumulation at the Austfonna ice cap shows mean absolute errors of 47 and 67 mm w.e. yr-1 when compared to radar-derived values for the selected years 2004 and 2006. Comparison of modeled surface height changes from 2003 to 2008, and satellite altimetry reveals good agreement in both mean values and regional differences. The largest deviations from observations are found for winter accumulation at Hansbreen (up to around 1000 mm w.e. yr-1), a site where sub-grid topography and wind redistribution of snow are important factors. Comparison with simulations using 9 km grid spacing reveal considerable differences on regional and local scales. In addition, 3 km grid spacing allows for a much more detailed comparison with observations than what is possible with 9 km grid spacing. Further decreasing the grid spacing to 1 km appears to be less significant, although in general precipitation amounts increase with resolution. Altogether, the model compares well with observations and offers possibilities for studying glacier climatic mass balance on Svalbard both historically as well as based on climate projections.

  5. Glacier crevasses: Observations, models, and mass balance implications

    NASA Astrophysics Data System (ADS)

    Colgan, William; Rajaram, Harihar; Abdalati, Waleed; McCutchan, Cheryl; Mottram, Ruth; Moussavi, Mahsa S.; Grigsby, Shane

    2016-03-01

    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 ice 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 ice fracture have emerged. The combination of employing damage mechanics to represent slow upstream deterioration of ice strength and fracture mechanics to represent rapid failure at downstream termini holds promise for implementation in large-scale ice 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 mass balance.

  6. LAKE MICHIGAN MASS BALANCE ATRAZINE DATA

    EPA Science Inventory

    The Lake Michigan Mass Balance Study measured PCBs, mercury, trans-nonachlor, and atrazine in rivers, the atmosphere, sediments, lake water, and the food chain. A mathematical model will predict what effect reducing pollution will have on the lake, and its large fish (lake trout ...

  7. LAKE MICHIGAN MASS BALANCE: MODELING PROCESS

    EPA Science Inventory

    The Lake Michigan Mass Balance Study measured PCBs, mercury, trans-nonachlor, and atrazine in rivers, the atmosphere, sediments, lake water, and the food chain. A mathematical model will predict what effect reducing pollution will have on the lake, and its large fish (lake trout ...

  8. LAKE MICHIGAN MASS BALANCE PCB DATA

    EPA Science Inventory

    The Lake Michigan Mass Balance Study measured PCBs, mercury, trans-nonachlor, and atrazine in rivers, the atmosphere, sediments, lake water, and the food chain. A mathematical model will predict what effect reducing pollution will have on the lake, and its large fish (lake trout ...

  9. Automated balance for determining true mass

    SciTech Connect

    Meyer, J.E.

    1982-08-08

    An automated weighing system utilizing a precision electronic balance and a small desktop computer is described. An example of a computer program demonstrating some of the capabilities attainable with this system is included. The program demonstrates a substitution weighing technique with true mass determination for the object being weighed.

  10. When Equal Masses Don't Balance

    ERIC Educational Resources Information Center

    Newburgh, Ronald; Peidle, Joseph; Rueckner, Wolfgang

    2004-01-01

    We treat a modified Atwood's machine in which equal masses do not balance 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…

  11. Present-day Antarctic Ice Mass Changes and Crustal Motion

    NASA Technical Reports Server (NTRS)

    James, Thomas S.; Ivins, Erik R.

    1995-01-01

    The peak vertical velocities predicted by three realistic, but contrasting, present-day scenarios of Antarctic ice sheet mass balance 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 ICE-3G glacial rebound model, which are in excess of 20 mm/a. If the Holocene Antarctic deglaciation history portrayed in ICE-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 mass 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).

  12. Present-day Antarctic ice mass changes and crustal motion

    NASA Technical Reports Server (NTRS)

    James, Thomas S.; Ivins, Erik R.

    1995-01-01

    The peak vertical velocities predicted by three realistic, but contrasting, present-day scenarios of Antarctic ice sheet mass balance 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 ICE-3G glacial rebound model, which are in excess of 20 mm/a. If the Holocene Antarctic deglaciation history protrayed in ICE-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 mass 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.

  13. Net mass balance calculations for the Shirase Drainage Basin, east Antarctica, using the mass budget method

    NASA Astrophysics Data System (ADS)

    Nakamura, Kazuki; Yamanokuchi, Tsutomu; Doi, Koichiro; Shibuya, Kazuo

    2016-06-01

    We quantify the mass budget of the Shirase drainage basin (SHI), Antarctica, by separately estimating snow accumulation (surface mass balance; SMB) and glacier ice mass 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. Ice thickness data at the GL were inferred by using a free-board relationship between the measured height and the ice thickness, and considering the measured firn depth correction (4.2 m with the reference ice density of 910 kg m-3) for the nearby blue-ice 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 mass balance, -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.

  14. Understanding the Role of Wind in Reducing the Surface Mass Balance Estimates over East Antarctica

    NASA Astrophysics Data System (ADS)

    Das, I.; Scambos, T. A.; Koenig, L.; Creyts, T. T.; Bell, R. E.; van den Broeke, M. R.; Lenaerts, J.; Paden, J. D.

    2014-12-01

    Accurate quantification of surface snow-accumulation over Antarctica is important for mass balance estimates and climate studies based on ice core records. An improved estimate of surface mass balance must include the significant role near-surface wind plays in the sublimation and redistribution of snow across Antarctica. We have developed an empirical model based on airborne radar and lidar observations, and modeled surface mass balance and wind fields to produce a continent-wide prediction of wind-scour zones over Antarctica. These zones have zero to negative surface mass balance, are located over locally steep ice sheet areas (>0.002) and controlled by bedrock topography. The near-surface winds accelerate over these zones, eroding and sublimating the surface snow. This scouring results in numerous localized regions (≤ 200 km2) with reduced surface accumulation. Each year, tens of gigatons of snow on the Antarctic ice sheet are ablated by persistent near-surface katabatic winds over these wind-scour zones. Large uncertainties remain in the surface mass balance estimates over East Antarctica as climate models do not adequately represent the small-scale physical processes that lead to mass loss through sublimation or redistribution over the wind-scour zones. In this study, we integrate Operation IceBridge's snow radar over the Recovery Ice Stream with a series of ice core dielectric and depth-density profiles for improved surface mass balance estimates that reflect the mass loss over the wind-scour zones. Accurate surface mass balance estimates from snow radars require spatially variable depth-density profiles. Using an ensemble of firn cores, MODIS-derived surface snow grain size, modeled accumulation rates and surface temperatures from RACMO2, we assemble spatially variable depth-density profiles and use our mapping of snow density variations to estimate layer mass and net accumulation rates from snow radar layer data. Our study improves the quantification of

  15. Modeling Past and Future Surface Mass Balance of the Patagonian Icefields

    NASA Astrophysics Data System (ADS)

    Schaefer, M.; Casassa, G., Sr.; Machguth, H.; Falvey, M. J.

    2014-12-01

    We present surface mass balance simulations of the Patagonian Icefield that were driven by global climate data (reanalysis/GCM) which were downscaled using the regional climate model Weather Research and Forecasting (WRF) and statistical downscaling methods. The special climatic situation in the region with sharp climate gradients introduced by the blocking of the westerlies by the high peaks of the Icefield are reproduced by downscaled climatic data. The mass balance simulations were validated and interpreted using geodetic mass balances, measured point balances and a complete velocity field of the Southern Patagonia Icefield (SPI) from spring 2004. The high measured accumulation of snow as well as the high measured ablation values are reproduced by the model. Subtracting the modeled surface mass balance from the geodetic balances, calving fluxes of major outlet glaciers were inferred. Good agreement with calving fluxes estimated from velocity data was obtained in many cases however on several glaciers the inferred calving fluxes seem to overestimate the measured calving fluxes. The measured calving fluxes exhibit large uncertainties due to mostly unknown ice thickness data and evolution of glacier velocities through time. The accumulation of snow and its redistribution due to wind drift present the mayor uncertainties in the modeled surface mass balance. Assuming no substantial changes in ice flow, the surface mass balance model driven by ECHAM5 data in the A1B scenario predicts a contribution of the Patagonian Icefields to sea-level rise in the 21st century of 7.3 mm.

  16. Improvements in the determination of ice sheet mass fluxes and freshwater fluxes using Icebridge data. (Invited)

    NASA Astrophysics Data System (ADS)

    Rignot, E. J.; Schodlok, M.; Menemenlis, D.; Studinger, M.; Cochran, J. R.; Bell, R. E.

    2010-12-01

    Recent airborne campaigns under NASA's Operation Icebridge have provided a significant increase in the availability of new observations of glaciers and ice sheets. Here, we focus on new ice thickness data and how these data help us constrain glacier ice mass fluxes; and new bathymetry data used to better constrain freshwater fluxes resulting from ice-ocean interactions at the underside of floating ice shelves. Icebridge ice thickness acquired in Greenland provide new thickness gates to estimate ice discharge and complete the circumnavigation of the island; yet, significant gaps remain in places not covered by radio echo sounding or where radio echo sounding is challenged by difficult environmental conditions. In the Antarctic, Icebridge collected ice thickness data along the Bellingshausen Sea sector where hardly any data had been collected in the past, ice thickness was inferred solely based on ice surface elevation, grounding line position and assumptions of hydrostatic equilibrium, and prior mass balance results indicated a large imbalance which was not entirely consistent with GRACE data and laser altimetry data. We are now resolving these differences with the new data. Finally, underneath ice shelves, new bathymetry data of Pine Island Glacier and Larsen C ice shelf derived from airborne gravity combined with other dat sets have had a large impact on our general knowledge and understanding of sub-ice-shelf cavities and the associated ice-shelf/ocean interactions. The new data reveal unknown seafloor ridges, seabed troughs, sills and over-deepenings that affect the pattern of sub-ice-shelf ocean circulation, the access of ocean heat to sub-ice-shelf cavities and glacier grounding lines, and rates of submarine melting. We demonstrate this by comparing estimates of submarine melting obtained with old and new bathymetry in the regional MITgcm ocean model configuration for Larsen C and Pine Island Ice Shelves, in Antarctica. In addition, we compare the ECCO2

  17. Sensible heat balance estimates of transient soil ice contents for freezing and thawing conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil ice content is an important component for winter soil hydrology. The sensible heat balance (SHB) method using measurements from heat pulse probes (HPP) is a possible way to determine transient soil ice content. In a previous study, in situ soil ice contents estimates with the SHB method were in...

  18. Brief communication "The aerophotogrammetric map of Greenland ice masses"

    NASA Astrophysics Data System (ADS)

    Citterio, M.; Ahlstrøm, A. P.

    2013-03-01

    The PROMICE (Programme for Monitoring of the Greenland Ice Sheet) aerophotogrammetric map of Greenland ice masses is the first high resolution dataset documenting the mid-1980s areal extent of the Greenland Ice Sheet and all the local glaciers and ice caps. The total glacierized area excluding nunataks was 1 804 638 km2 ± 2178 km2, of which 88 083 ± 1240 km2 belonged to local glaciers and ice caps (GIC) substantially independent from the Greenland Ice Sheet. This new result of GIC glacierized area is higher than most previous estimates, 81% greater than Weng's (1995) measurements, but is in line with contemporary findings based on independent data sources. A comparison between our map and the recently released Rastner et al. (2012) inventory and GIMP (Greenland Ice Mapping Project) Ice-Cover Mask (Howat and Negrete, 2013) shows potential for change-assessment studies.

  19. An Iterated Global Mascon Solution with Focus on Land Ice Mass Evolution

    NASA Technical Reports Server (NTRS)

    Luthcke, S. B.; Sabaka, T.; Rowlands, D. D.; Lemoine, F. G.; Loomis, B. D.; Boy, J. P.

    2012-01-01

    Land ice mass 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 ice 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 balance seasons and annual mass balances. The details and causes of the spatial and temporal variability of the land ice regions studied are discussed.

  20. MBA, mass balance area user guide

    SciTech Connect

    Russell, V.K.

    1994-09-22

    This document presents the Mass BAlance (MBA) database system user instructions which explain how to record the encapsulation activity from the K Basin as it is being performed on the computer, activity associated with keeping the work area safe from going critical, and administrative functions associated with the system. This document includes the user instructions, which also serve as the software requirements specification for the system implemented on the microcomputer. This includes suggested user keystrokes, examples of screens displayed by the system, and reports generated by the system. It shows how the system is organized, via menus and screens. It does not explain system design nor provide programmer instructions. MBA was written to equip the personnel performing K-Basin encapsulation tasks with a conservative estimate of accumulated mass during the processing of canisters into and out of the chute, primarily in the K-East basin.

  1. Boundary layer stability acts to ballast the mass of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Berkelhammer, M. B.; Noone, D. C.; Steen-Larsen, H. C.; O'Neill, M.; Raudzens Bailey, A.; Cox, C.; Schneider, D. P.

    2014-12-01

    The mass of the Greenland Ice Sheet has been reduced over recent decades as a consequence of warming, the impact of which is already detectable on global sea level. However, temperature projections suggest that at interior high-altitude sites on the ice it could be decades or more before warming forces these regions to transition from a dry to wet snow facies. Shifts in boundary layer dynamics, including atmosphere-ice sheet hydrological exchange and cloud radiative forcing could expedite or delay this transition. These processes are important with respect to future ice sheet stability, yet they remain difficult to constrain. Using continuous in situ measurements of vertical profiles of the isotopic composition of water vapor at Summit Camp, the highest observatory on the ice sheet, we document the presence of a hydrologic balance between surface sublimation and condensation fluxes. This exists because of a nearly persistent temperature inversion, which hinders the efficiency with which surface water vapor mixes into the free atmosphere. In the presence of a strong temperature inversion, fog and ice particles form near the ice-atmosphere interface from surface moisture fluxes. When this condensate precipitates on or settles to the surface, it ballasts the ice sheet's mass. A decade-long trend towards lower annual accumulation at Summit may therefore reflect continuous replacement of the near surface atmosphere due to reduced atmospheric stability. If this tendency toward destabilization continues, it could accelerate mass loss at interior sites on the ice sheet. The role of boundary layer stability in ice sheet hydrological budgets discussed here is applicable beyond the accumulation zone of the Greenland Ice Sheet.

  2. Mass changes in Arctic ice caps and glaciers: implications of regionalizing elevation changes

    NASA Astrophysics Data System (ADS)

    Nilsson, J.; Sandberg Sørensen, L.; Barletta, V. R.; Forsberg, R.

    2015-01-01

    The mass balance of glaciers and ice caps is sensitive to changing climate conditions. The mass changes derived in this study are determined from elevation changes derived measured by the Ice, Cloud, and land Elevation Satellite (ICESat) for the time period 2003-2009. Four methods, based on interpolation and extrapolation, are used to regionalize these elevation changes to areas without satellite coverage. A constant density assumption is then applied to estimate the mass change by integrating over the entire glaciated region. The main purpose of this study is to investigate the sensitivity of the regional mass balance of Arctic ice caps and glaciers to different regionalization schemes. The sensitivity analysis is based on studying the spread of mass changes and their associated errors, and the suitability of the different regionalization techniques is assessed through cross-validation. The cross-validation results shows comparable accuracies for all regionalization methods, but the inferred mass change in individual regions, such as Svalbard and Iceland, can vary up to 4 Gt a-1, which exceeds the estimated errors by roughly 50% for these regions. This study further finds that this spread in mass balance is connected to the magnitude of the elevation change variability. This indicates that care should be taken when choosing a regionalization method, especially for areas which exhibit large variability in elevation change.

  3. Glacier modeling in support of field observations of mass balance at South Cascade Glacier, Washington, USA

    USGS Publications Warehouse

    Josberger, Edward G.; Bidlake, William R.

    2010-01-01

    The long-term USGS measurement and reporting of mass balance at South Cascade Glacier was assisted in balance years 2006 and 2007 by a new mass balance model. The model incorporates a temperature-index melt computation and accumulation is modeled from glacier air temperature and gaged precipitation at a remote site. Mass balance modeling was used with glaciological measurements to estimate dates and magnitudes of critical mass balance phenomena. In support of the modeling, a detailed analysis was made of the "glacier cooling effect" that reduces summer air temperature near the ice 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 balances of South Cascade Glacier, computed with this new, model-augmented methodology, were 2.61 and 3.41 mWE, respectively. The 2006 and 2007 summer balances were -4.20 and -3.63 mWE, respectively, and the 2006 and 2007 net balances were -1.59 and -0.22 mWE. PDF version of a presentation on the mass balance of South Cascade Glacier in Washington state. Presented at the American Geophysical Union Fall Meeting 2010.

  4. Balancing The Books - A Statistical Theory of Mass Balances

    NASA Astrophysics Data System (ADS)

    O'Kane, J. P.

    Mass budgets, without a theory, are an empirical "method of choice" in the environ- mental sciences. There is however a difficulty. Budgets are usually presented as perfect balances with no closing error, justified by the law of mass conservation. Neverthe- less, there is always a closing error! Declaring the error, e, simply raises the question of the acceptability of the budget. To answer this we need a reference quantity against which to compare e. This quantity can only be provided by theory and must also be a mathematical function of all the budget data. Two statistical techniques provide the theory and the function: (1) Probability sampling for estimating the terms of the bud- get, the closing error and their sampling precision, and (2) Hypothesis testing that any particular value of e is due to chance alone. Both techniques must satisfy R.A. Fisher's "vital requirement that the actual and physical conduct of experiments should govern the statistical procedure of their interpretation". Probability sampling is any sampling procedure governed by sets of random numbers. Applying the calculus of probability to the chosen procedure, delivers the theoretical probability distribution of the terms of the budget, and the closing error e', on the assumption that there are no systematic errors of measurement or missing fluxes. In the simplest case, we may use simple or stratified random sampling, defined on a spatio- temporal sampling frame, which covers the duration of the budget on the space-filling object. When the number of independent measurements (samples) is statistically large, the central limit theorem implies that e' is normally distributed. The assumption that there are no systematic errors of measurement, sampling bias, or missing fluxes, and the law of mass conservation, together imply that E(e') = 0. Unbiased, independent sampling of the terms of the budget makes the variance Var(e') equal to the sum of the sampling variances of the individual terms in the

  5. Brief communication "The aerophotogrammetric map of Greenland ice masses"

    NASA Astrophysics Data System (ADS)

    Citterio, M.; Ahlstrøm, A. P.

    2012-09-01

    The PROMICE (Programme for Monitoring of the Greenland Ice Sheet) aerophotogrammetric map of Greenland ice masses is the first high resolution dataset documenting the mid-1980's extent of the Greenland Ice Sheet and all the local glaciers and ice caps. The total glacierized area was 1 804 638 km2 ± 2178 km2, of which 88 083 ± 1240 km2 belonged to local glaciers and ice caps (GIC) substantially independent from the Greenland Ice Sheet. This new result of GIC glacierized area is higher than most previous estimates, and is in line with contemporary findings based on independent data sources. Comparison between our map and the recently released GIMP (Greenland Mapping Project) Ice Cover Mask (Howat and Negrete, 2012) show potential for change assessment studies.

  6. Earth Structure, Ice Mass Changes, and the Local Dynamic Geoid

    NASA Astrophysics Data System (ADS)

    Harig, C.; Simons, F. J.

    2014-12-01

    be used for corrections for glacio-isostatic adjustment, as necessary for the interpretation of time-variable gravity observations in terms of ice sheet mass-balance studies.

  7. Glacier Mass Balance measurements in Bhutan

    NASA Astrophysics Data System (ADS)

    Jackson, Miriam; Tenzin, Sangay; Tashi, Tshering

    2014-05-01

    Long-term glacier measurements are scarce in the Himalayas, partly due to lack of resources as well as inaccessibility of most of the glaciers. There are over 600 glaciers in Bhutan in the Eastern Himalayas, but no long-term measurements. However, such studies are an important component of hydrological modelling, and especially relevant to the proposed expansion of hydropower resources in this area. Glaciological studies are also critical to understanding the risk of jøkulhlaups or GLOFS (glacier lake outburst floods) from glaciers in this region. Glacier mass balance measurements have been initiated on a glacier in the Chamkhar Chu region in central Bhutan by the Department of Hydro-Met Services in co-operation with the Norwegian Water Resources and Energy Directorate. Chamkhar Chu is the site of two proposed hydropower plants that will each generate over 700 MW, although the present and future hydrological regimes in this basin, and especially the contribution from glaciers, are not well-understood at present. There are about 94 glaciers in the Chamkhar Chhu basin and total glacier area is about 75 sq. km. The glaciers are relatively accessible for the Himalayas, most of them can be reached after only 4-5 days walk from the nearest road. One of the largest, Thana glacier, has been chosen as a mass balance glacier and measurements were initiated in 2013. The glacier area is almost 5 sq. km. and the elevation range is 500 m (5071 m a.s.l. to 5725 m a.s.l.) making it suitable as a benchmark glacier. Preliminary measurements on a smaller, nearby glacier that was visited in 2012 and 2013 showed 1 m of firn loss (about 0.6 m w.eq.) over 12 months.

  8. Sedimentation rate determination by radionuclides mass balances

    NASA Astrophysics Data System (ADS)

    Cazala, C.; Reyss, J. L.; Decossas, J. L.; Royer, A.

    2003-04-01

    In the past, uranium mining activity took place in the area around Limoges, France. Even nowadays, this activity results in an increase in the input and availability of radionuclides in aquifer reservoirs, making of this area a suitable site to better understand the behaviour of radionuclides in the surficial environment. Water was sampled monthly over the entire year 2001 in a brook that collects mine water and in a lake fed by this brook. Samples were filtered through 0.45μm filters to remove particles. Activities of 238U, 226Ra, 210Pb, 228Th and 228Ra were measured on particulate (>0.45μm), dissolved (<0.45μm) and total (unfiltered) fractions by gamma spectrometry in the well of a high efficiency, low background, germanium detector settled in an underground laboratory, protected from cosmic rays by 1700 m of rocks (LSM, CNRS-CEA, French Alps). Activities measured in particulate and dissolved fractions were summed and compared to the one measured in unfiltered water to test the filtration yield. No significant loss or contamination were detected. In the brook water, 70% of 238U, 60% of 226Ra and 80% of 210Pb are associated with particles. Activities associated with particles decrease drastically along with the velocity of current when the stream enters the lake. An annual mass balance of radionuclides carried by particles from the stream to the lake was used to determine the sedimentation rate in the lake. The flux of particles deduced from mass balance calculations based on five isotopes corresponds to the thickness of sediment accumulated since the creation of this artificial lake (that is, 1976). This study emphasises the usefulness of radionuclides as tracers for environmental investigations.

  9. The Arctic Ocean ice balance - A Kalman smoother estimate

    NASA Technical Reports Server (NTRS)

    Thomas, D. R.; Rothrock, D. A.

    1993-01-01

    The methodology of Kalman filtering and smoothing is used to integrate a 7-year time series of buoy-derived ice motion fields and satellite passive microwave observations. The result is a record of the concentrations of open water, first-year ice, and multiyear ice that we believe is better than the estimates based on the microwave data alone. The Kalman procedure interprets the evolution of the ice cover in terms of advection, melt, growth, ridging, and aging of first-year into multiyear ice. Generally, the regions along the coasts of Alaska and Siberia and the area just north of Fram Strait are sources of first-year ice, with the rest of the Arctic Ocean acting as a sink for first-year ice via ridging and aging. All the Arctic Ocean except for the Beaufort and Chukchi seas is a source of multiyear ice, with the Chukchi being the only internal multiyear ice sink. Export through Fram Strait is a major ice sink, but we find only about two-thirds the export and greater interannual variation than found in previous studies. There is no discernible trend in the area of multiyear ice in the Arctic Ocean during the 7 years.

  10. Mass Loss of Glaciers and Ice Caps From GRACE During 2002-2015

    NASA Astrophysics Data System (ADS)

    Ciraci, E.; Velicogna, I.; Wahr, J. M.; Swenson, S. C.

    2015-12-01

    We use time series of time-variable gravity from the NASA/DLR GRACE mission using a mascon approach to estimate the ice mass balance of the Earth's Mountain Glaciers and Ice Caps (GICs), excluding the Antarctic and the Greenland peripheral glaciers, between January 2003 and October 2014. We estimate a total ice mass loss equal to -217 ± 33 Gt/yr, equivalent to a sea level rise of 0.6±0.09 mm/yr. The global signal is driven by a few regions, contributing to almost of 75% of the total ice mass loss. Among these areas, the main contributor is the Canadian Arctic Archipelago with a total mass loss of -75 ± 9 Gt/yr, followed by Alaska (-51 ± 10 Gt/yr), Patagonia (-26 ± 10 Gt/yr) and the High Mountains of Asia (-25 ± 13 Gt/yr). The mass loss for most of the arctic regions is not constant, but accelerates with time. The Canadian Archipelago, in particular, undergoes a strong acceleration in mass waste (-7±1 Gt/yr2). The signal acceleration is mainly driven by the northern located Queen Elisabeth Islands (-4.5 ± 0.6 Gt/yr2). A similar behavior is observed for Svalbard and the Russian Arctic. In this second case, however, we observe an enhanced mass loss starting from the second decade of the 21st century after a period of nearly stable mass balance. The observed acceleration helps reconcile regional ice mass estimates obtained for different time periods.

  11. Mass budget of Queen Elizabeth Islands glaciers and ice caps, Canada, from 1992 to present

    NASA Astrophysics Data System (ADS)

    Millan, R.; Rignot, E. J.; Mouginot, J.

    2015-12-01

    Recent studies indicate to say that the Canadian Artic Archipelago's mass loss has increased in recent years. However the role of ice dynamics changes in this area is not well known. In this study, we present a comprehensive velocity mapping of the CAA using ALOS/PALSAR, RADARSAT-1, ERS1 and Landsat data between 1992 and 2015. Glaciers speed are calculated using a speckle and feature tracking algorithm.The results reveals that three large marine-terminating glaciers have accelerated significantly after 2010, while most others have slowed down or retreated to a sill to become similar to land-terminating glaciers. By combining the velocities of these glaciers with ice thickness measurements from NASA's Operation IceBridge, we calculate their ice discharge. The fluxes of these glaciers increased significantly since 2000 with a marked increase after 2011. The comparison of ice discharge with the surface mass balance from RACMO-2, shows that these glaciers came out of balance after 2011, which is also a time period where their discharge almost doubled. The analysis of RACMO-2 reveals an increase in runoff between 1970's and today and a precipitation with no significant trend. We digitalize the calving front positions of the glaciers and show an increasing rate retreat since 1976. We conclude that global pattern of velocity changes shows that the mass losses due to surface mass balance will likely going to raise in the coming years and that ice discharge will have a smaller part in the contribution of the CAA to sea level rise.

  12. Water, ice, meteorological, and speed measurements at South Cascade Glacier, Washington, 1999 balance year

    USGS Publications Warehouse

    Krimmel, Robert M.

    2001-01-01

    Winter snow accumulation and summer snow, firn, and ice melt were measured at South Cascade Glacier, Washington, to determine the winter and net balances for the 1999 balance year. The 1999 winter snow balance, averaged over the glacier, was 3.59 meters, and the net balance was 1.02 meters. Since the winter balance record began in 1959, only three winters have had a higher winter balance. Since the net balance record began in 1953, only 2 years have had a greater positive net balance than 1999. Runoff was measured from the glacier and an adjacent non-glacierized basin. Air temperature, precipitation, and humidity were measured nearby, and ice speed was measured. This report makes these data available to the glaciological and climatological community.

  13. Field test and sensitivity analysis of a sensible heat balance method to determine ice contents

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil ice content impacts winter vadose zone hydrology. It may be possible to estimate changes in soil ice content with a sensible heat balance (SHB) method, using measurements from heat pulse (HP) sensors. Feasibility of the SHB method is unknown because of difficulties in measuring soil thermal pro...

  14. Glacier mass balance in high-arctic areas with anomalous gravity

    NASA Astrophysics Data System (ADS)

    Sharov, A.; Rieser, D.; Nikolskiy, D.

    2012-04-01

    All known glaciological models describing the evolution of Arctic land- and sea-ice masses 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 mass budget of glaciological objects. At best, the gravity-induced component of ice mass variations can be determined on topographically smooth, open and steady surfaces, like those of arctic planes, regular ice caps and landfast sea ice. The present research is devoted to studying gravity-driven impacts on glacier mass balance 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 ice 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 ice 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 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-1980s with modern elevation data obtained from satellite radar interferometry and lidar altimetry. Free-air gravity anomalies were

  15. A nitrogen mass balance for California

    NASA Astrophysics Data System (ADS)

    Liptzin, D.; Dahlgren, R. A.

    2010-12-01

    Human activities have greatly altered the global nitrogen cycle and these changes are apparent in water quality, air quality, ecosystem and human health. However, the relative magnitude of the sources of new reactive nitrogen and the fate of this nitrogen is not well established. Further, the biogeochemical aspects of the nitrogen cycle are often studied in isolation from the economic and social implications of all the transformations of nitrogen. The California Nitrogen Assessment is an interdisciplinary project whose aim is evaluating the current state of nitrogen science, practice, and policy in the state of California. Because of the close proximity of large population centers, highly productive and diverse agricultural lands and significant acreage of undeveloped land, California is a particularly interesting place for this analysis. One component of this assessment is developing a mass balance of nitrogen as well as identifying gaps in knowledge and quantifying uncertainty. The main inputs of new reactive nitrogen to the state are 1) synthetic nitrogen fertilizer, 2) biological nitrogen fixation, and 3) atmospheric nitrogen deposition. Permanent losses of nitrogen include 1) gaseous losses (N2, N2O, NHx, NOy), 2) riverine discharge, 3) wastewater discharge to the ocean, and 4) net groundwater recharge. A final term is the balance of food, feed, and fiber to support the human and animal populations. The largest input of new reactive nitrogen to California is nitrogen fertilizer, but both nitrogen fixation and atmospheric deposition contribute significantly. Non-fertilizer uses, such as the production of nylon and polyurethane, constitutes about 5% of the synthetic N synthesized production. The total nitrogen fixation in California is roughly equivalent on the 400,000 ha of alfalfa and the approximately 40 million ha of natural lands. In addition, even with highly productive agricultural lands, the large population of livestock, in particular dairy cows

  16. Automated chemical mass balance receptor modeling

    SciTech Connect

    Hanrahan, P.L.; Core, J.E.

    1986-09-01

    Chemical mass balance (CMB) receptor modeling provides alternative or complementary methods to dispersion models for apportioning particulate source impacts. This method estimates particulate source contributions at a receptor by comparing the chemistry of the ambient aerosol to the chemistry of the emissions from the various sources. To minimize demands on the analyst and facilitate the processing of large volumes of data, an initial version of an automated CMB model has been developed and is operational on an IBM personal computer as well as on a Harris mini-mainframe computer. Although it currently does not have all the features of the more interactive manual model, it does show promise for reducing man-power demands. The automated model is based on an early version of the EPA CMB model, which has been converted to run on an IBM-PC or compatible microcomputer. It uses the effective variance method. The interactive manual model is also undergoing modifications under an EPA contract. Some of these new features of the EPA model have been included in one version of the automated model.

  17. GIA models with composite rheology and 3D viscosity: effect on GRACE mass balance in Antarctica

    NASA Astrophysics Data System (ADS)

    van der Wal, Wouter; Whitehouse, Pippa; Schrama, Ernst

    2014-05-01

    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 mass balance estimates in Antarctica. We use a GIA model with 3D viscosity and composite rheology in combination with ice loading histories ICE-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 ICE-5G forcing is located over the Ronne-Filchner ice shelf. This is in contrast with the results obtained using a 1D model, in which the maximum gravity rate due to ICE-5G forcing is always located over the Ross ice 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 mass balance estimates for the three preferred viscosity models are -131 to -171 Gt/year for the ICE-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 ice loading histories.

  18. State of balance of the cryosphere

    NASA Technical Reports Server (NTRS)

    Van Der Veen, C. J.

    1991-01-01

    Available observations and mass balance estimates of the cryosphere are summarized. Problems discussed include mountain glaciers, the Greenland ice sheet, the Antarctic ice sheet, conventional glacier measurement techniques, and satellite applications in glacier mass balance studies. It is concluded that the interior part of the Greenland ice sheet is thickening or in near equilibrium. Estimates of the mass balance of the Antarctic ice sheet suggest that it is positive, although the error limits allow for a slightly negative balance.

  19. 3D viscosity maps for Greenland and effect on GRACE mass balance estimates

    NASA Astrophysics Data System (ADS)

    van der Wal, Wouter; Xu, Zheng

    2016-04-01

    The GRACE satellite mission measures mass loss of the Greenland ice sheet. To correct for glacial isostatic adjustment numerical models are used. Although generally found to be a small signal, the full range of possible GIA models has not been explored yet. In particular, low viscosities due to a wet mantle and high temperatures due to the nearby Iceland hotspot could have a significant effect on GIA gravity rates. The goal of this study is to present a range of possible viscosity maps, and investigate the effect on GRACE mass balance estimates. Viscosity is derived using flow laws for olivine. Mantle temperature is computed from global seismology models, based on temperature derivatives for different mantle compositions. An indication for grain sizes is obtained by xenolith findings at a few locations. We also investigate the weakening effect of the presence of melt. To calculate gravity rates, we use a finite-element GIA model with the 3D viscosity maps and the ICE-5G loading history. GRACE mass balances for mascons in Greenland are derived with a least-squares inversion, using separate constraints for the inland and coastal areas in Greenland. Biases in the least-squares inversion are corrected using scale factors estimated from a simulation based on a surface mass balance model (Xu et al., submitted to The Cryosphere). Model results show enhanced gravity rates in the west and south of Greenland with 3D viscosity maps, compared to GIA models with 1D viscosity. The effect on regional mass balance is up to 5 Gt/year. Regional low viscosity can make present-day gravity rates sensitivity to ice thickness changes in the last decades. Therefore, an improved ice loading history for these time scales is needed.

  20. The impact of supraglacial debris on the mass balance and dynamics of Khumbu Glacier, Nepalese Himalaya

    NASA Astrophysics Data System (ADS)

    Rowan, Ann; Quincey, Duncan; Glasser, Neil; Egholm, David; Gibson, Morgan; Irvine-Fynn, Tristram; Porter, Philip

    2015-04-01

    Rapid changes in glacier volumes and dynamics have been observed in the monsoon-influenced Himalaya over recent decades, with marked consequences for the hydrological budgets and glacial hazard potential of catchments such as the Dudh Kosi, a tributary of the Ganges River. For many large glaciers such as Khumbu Glacier in eastern Nepal, supraglacial rock debris modifies the thermal properties of the ice surface and mass balance variations in response to climatic change. Ice flow dynamics vary dramatically with supraglacial debris thickness -- the debris-covered section of Khumbu Glacier appears stagnant, while the clean-ice section reaches velocities exceeding 50 m per year -- resulting in spatial variation in the drivers of mass transfer and loss. However, the relative importance of supraglacial debris in modifying mass balance compared to external forcing by the summer monsoon is poorly understood, and as a result quantifying the sensitivity of this glacier to climatic change is challenging. To calculate ablation across the glacier we need to incorporate the thermal properties of the debris layer and how these vary with altitude and time into a mass balance calculation. We made field observations describing debris thickness and sub-debris melt rates on Khumbu Glacier. At four different sites, we measured vertical temperature profiles through the supraglacial debris and at the ice surface, debris thickness, and 1 m air temperature through the summer monsoon, and calculated ablation rates following the method of Nicholson and Benn (2006, J. Glacio.). These data were used with local meteorological data to calculate the spatial and temporal variability in the surface energy balance of Khumbu Glacier. To investigate the sensitivity of Khumbu Glacier to climatic change, we developed a numerical model of this glacier from our field data. Our higher-order flow model (Egholm et al., 2011; JGR) reproduces accurately the variations in ice velocity observed using feature

  1. Mass balance, meteorological, and runoff measurements at South Cascade Glacier, Washington, 1992 balance year

    USGS Publications Warehouse

    Krimmel, R.M.

    1993-01-01

    Values of winter snow accumulation and summer snow, firn, and ice ablation were measured at South Cascade Glacier, WA, to determine the winter and net balance for the 1992 balance year. The 1992 winter balance, averaged over the glacier, was 1.91 m, and the net balance was -2.01 m. This extremely negative balance continued a trend of negative balance years beginning in 1977. Air temperature (at 1,615 m and 1,867 m), barometric pressure, precipitation, and runoff from this glacier basin and an adjacent non-glacierized basin were also continuously measured. This report makes all these data, in tabular, graphical, and machine-readable forms, available to users.

  2. Surface energy balance, clouds and radiation over Antarctic sea ice during Austral spring

    NASA Astrophysics Data System (ADS)

    Vancoppenolle, M.; Ackley, S. F.; Perovich, D. K.; Tison, J.-L.

    2009-04-01

    In Sept-Oct 2007, a sea ice drift station, Ice Station Belgica, was established in the Bellingshausen Sea. Over twenty-seven days, measurements of meteorological variables, radiation and surface albedo were performed by combining ship-based and in situ data, in order to assess the surface energy balance. Visual observations of the state of the sky (clear or overcast) were also done. The sampled floe was characterized by thin (0.6m) and medium thick (1.1m) first-year ice and older, second-year ice of greater than 2m mean thickness. Snow cover depth varied from zero cm over the new ice to > 0.8m on the second year ice. The weather at Ice Station Belgica was characterized by typical spring conditions. Synoptic variability was mostly driven by the wind direction, which determines the origin - continental or oceanic - of the air masses. Under northerly winds, warm (from -5 to 0 °C) and wet (relative humidity from 90 to 100%) oceanic air was advected on the floe. Under southerlies, cold (from -20 to -10°C) and dry (70-85 %) continental air was brought on site. In turn, this also determined the state of the sky, with clear (overcast) skies mostly associated to continental (oceanic) weather. The incoming solar radiation was on average 124 W/m², with a trend of 3.5 W/m² over the ice station, while the incoming longwave radiation was on average 227 W/m², with no trend. As expected, the incoming solar radiation shows a marked diurnal cycle, while LW does not. The day-to-day variability in radiation is largely determined by changes in the state of the sky. Broadband surface albedo was measured in situ, using a bidirectional pyranometer, on two sites respectively covered by thin (10-15 cm) and deep (30-40 cm) snow. Both sites were visited every 5 days and albedo was measured on 6 points, spaced by 5 m on an 25-m long "albedo" line. Snow depth was also monitored every meter along the albedo line. The mean albedo is 0.83 ± 0.05. Variations around this mean value are

  3. Spatial and temporal distribution of mass loss from the Greenland Ice Sheet since AD 1900.

    PubMed

    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

    2015-12-17

    The response of the Greenland Ice Sheet (GIS) to changes in temperature during the twentieth century remains contentious, largely owing to difficulties in estimating the spatial and temporal distribution of ice mass 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 balance 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 ice mass 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 Ice Age at the end of the nineteenth century. We estimate the total ice mass 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 mass balance models we partition the mass balance into a term for surface mass balance (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 mass balance 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

  4. Spatial and temporal distribution of mass loss from the Greenland Ice Sheet since AD 1900

    NASA Astrophysics Data System (ADS)

    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.

    2015-12-01

    The response of the Greenland Ice Sheet (GIS) to changes in temperature during the twentieth century remains contentious, largely owing to difficulties in estimating the spatial and temporal distribution of ice mass 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 balance 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 ice mass 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 Ice Age at the end of the nineteenth century. We estimate the total ice mass 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 mass balance models we partition the mass balance into a term for surface mass balance (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 mass balance 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

  5. Recalculated mass balance record for Midre Lovénbreen, Svalbard

    NASA Astrophysics Data System (ADS)

    Kohler, J.

    2013-12-01

    Glacier mass balance has been measured since 1968 on Midre Lovénbreen, Svalbard, one of the longest high Arctic records. Available data includes areally-averaged winter, summer, and net balances. Balances by elevation, however, were not consistently reported. Here we derive a time-series of the balances as a function of elevation using original stake data from archived field notebooks and maps, graphs of balance as a function of elevation taken from old reports. We recalculate areally-averaged balances using a different fits to the data, rather than hand-drawn curves from earlier years, and adjust for changes in hypsometry. There is good agreement between in situ mass balance and geodetic changes obtained by differencing digital elevation models (DEMs) from different dates (1936, 1962, 1969, 1977, 1995, 2003, 2005). The main long-term trends over the length of the 44-yr record are that winter and net balance are decreasing overall, and that summer and net balance elevational gradients increase, the result of increasing ice loss at lower elevations.

  6. Surface Mass Balance of the Columbia Glacier, Alaska, 1978 and 2010 Balance Years

    USGS Publications Warehouse

    O'Neel, Shad

    2012-01-01

    Although Columbia Glacier is one of the largest sources of glacier mass loss in Alaska, surface mass balance measurements are sparse, with only a single data set available from 1978. The dearth of surface mass-balance data prohibits partitioning of the total mass losses between dynamics and surface forcing; however, the accurate inclusion of calving glaciers into predictive models requires both dynamic and climatic forcing of total mass balance. During 2010, the U.S. Geological Survey collected surface balance data at several locations distributed over the surface of Columbia Glacier to estimate the glacier-wide annual balance for balance year 2010 using the 2007 area-altitude distribution. This report also summarizes data collected in 1978, calculates the 1978 annual surface balance, and uses these observations to constrain the 2010 values, particularly the shape of the balance profile. Both years exhibit balances indicative of near-equilibrium surface mass-balance conditions, and demonstrate the importance of dynamic processes during the rapid retreat.

  7. Evapotranspiration: Mass balance measurements compared with flux estimation methods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evapotranspiration (ET) may be measured by mass balance methods and estimated by flux sensing methods. The mass balance 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...

  8. Mass balance and exergy analysis of a fast pyrolysis system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mass balance closure and exergetic efficiency is evaluated for a bench scale fast pyrolysis system. The USDA Agricultural Research Service (ARS) has developed this system for processing energy crops and agricultural residues for bio-oil (pyrolysis oil or pyrolysis liquids) production. Mass balance c...

  9. Optimization of regional constraints for estimating the Greenland mass balance with GRACE level-2 data

    NASA Astrophysics Data System (ADS)

    Xu, Z.; Schrama, E.; van der Wal, W.

    2015-07-01

    Data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission can be used to estimate the mass change rate for separate drainage systems (DSs) of the Greenland Ice Sheet (GrIS). One approach to do so is by inversion of the level-2 spherical harmonic data to surface mass changes in predefined regions, or mascons. However, the inversion can be numerically unstable for some individual DSs. This occurs mainly for DSs with a small mass change signal that are located in the interior region of Greenland. In this study, we present a modified mascon inversion approach with an improved implementation of the constraint equations to obtain better estimates for individual DSs. We use separate constraints for mass change variability in the coastal zone, where run-off takes place, and for the ice sheet interior above 2000 m, where mass changes are smaller. A multi-objective optimization approach is used to find optimal prior variances for these two areas based on a simulation model. Correlations between adjacent DSs are suppressed when our optimized prior variances are used, while the mass balance estimates for the combination of the DSs that make up the GrIS above 2000 m are not affected significantly. The resulting mass balance estimates for some DSs in the interior are significantly improved compared to an inversion with a single constraint, as determined by a comparison with mass balance estimates from surface mass balance modelling and discharge measurements. The rate of mass change of the GrIS for the period of January 2003 to December 2012 is found to be -266.1 ± 17.2 Gt yr-1 in the coastal zone and areas below 2000 m, and +8.2 ± 8.6 Gt yr-1 in the interior region.

  10. Using an SLR inversion to measure the mass balance of Greenland before and during GRACE

    NASA Astrophysics Data System (ADS)

    Bonin, Jennifer

    2016-04-01

    The GRACE mission has done an admirable job of measuring large-scale mass changes over Greenland since its launch in 2002. However before that time, measurements of large-scale ice mass balance 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 ice 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 mass 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 mass change over Greenland. I find favorable agreement between the pure-SLR inverted results and the 2012 Ice-sheet Mass Balance Inter-comparison Exercise (IMBIE) results, which are largely based on the "input-output" modeling method before GRACE's launch.

  11. Tree-ring based mass balance estimates along the North Pacific Rim

    NASA Astrophysics Data System (ADS)

    Malcomb, N.; Wiles, G. C.

    2009-12-01

    Glacier mass balance reconstructions provide a means of placing short-term mass balance observations into a longer-term context. In western North America, most instrumental records of mass balance are limited in duration and capture only a narrow window of glacial behavior over an interval that is dominated by warming and ablation. Tree-ring series from northwestern North America are used to reconstruct annual mass balance for Gulkana and Wolverine Glaciers in Alaska, Peyto and Place Glaciers in British Columbia, and South Cascade and Blue Glaciers in Washington State. Mass balance models rely on the temperature and precipitation sensitivity of the tree-ring chronologies and mass balance records, as well as teleconnections along the North Pacific sector. The reconstructions extend through the latter portions of the Little Ice Age (LIA) and highlight the role of decadal and secular-scale climate change in forcing mass balance. Net mass balance reconstructions are broadly consistent with the moraine record that coincides with two major intervals of positive mass balance and with cooling related to the Maunder and Dalton solar minima. Secular warming in the later portions of the 19th and the 20th centuries corresponds with a pronounced interval of negative mass balance, and model instability after 1980. These trends show that the marked changes in glacier systems over recent decades throughout the Northwestern Cordillera are unique for the last several centuries and furthermore, suggest that modest gains forced by increasing precipitation over the latter 20th century in coastal settings are not sufficient to force glacier expansion or moraine building. Reconstructed (blue) and instrumental (red) net mass balances, Northern Hemisphere Temperature anomalies (Wilson et al., 2007), and PDO index (MacDonald and Case, 2005). A= Gulkana Glacier, B=Wolverine Glacier, C=Peyto Glacier, D=Place Glacier, E=South Cascade, F=Blue Glacier, G=PDO index, and H=Northern Hemisphere

  12. DEVELOPMENT OF A CONTAMINANT TRANSPORT AND FATE MASS BALANCE CALIBRATION MODEL FOR LAKE MICHIGAN MASS BALANCE PROJECT (LMMBP)

    EPA Science Inventory

    Lake Michigan Mass Balance Project (LMMBP) was initiated to directly support the development of a lakewide management plan (LaMP) for Lake Michigan. A mass balance modeling approach is proposed for the project to addrss the realtionship between sources of toxic chemicals and thei...

  13. Modelling the deformation and force balance of anisotropic Arctic Sea Ice

    NASA Astrophysics Data System (ADS)

    Heorton, Harry; Feltham, Daniel; Tsamados, Michel; Schroeder, David

    2016-04-01

    The movement and spatial distribution of Arctic sea ice is due to its response to external forces. The deformation of Arctic sea ice is observed to have structural alignment on all length scales. By considering the alignment of diamond-shaped sea ice floes an anisotropic rheology has been developed for use in a climate sea ice model. Here we present investigations into the role of anisotropy in calculating the internal stress gradient of Arctic sea ice over climate length and time scales in a state-of-the-art climate sea ice model, the Los Alamos Sea Ice model. Our investigations are focused on the link between the external dynamical forcing and the emergent properties of sea ice such as its drift speed and thickness distribution. We analyse the model's response to external forcing over short time scales showing the characteristics of deformation events for different sea ice states and anisotropic alignment. We show how these events add up to produce the full seasonal stress balance and sea ice state over the Arctic ocean.

  14. Taking a balanced approach to estimating snow and ice melt contributions to High Asia runoff

    NASA Astrophysics Data System (ADS)

    Barrett, A. P.

    2015-12-01

    We assess the magnitude and variability of glacier and snow melt input to rivers draining the major glacierized and snow covered river basins of High Asia. The water budget provides a basic framework for hydrological analysis. Measurements of all components of the water budget allow the accuracy of estimates of each component to be checked. In glacierized catchments, the water budget is the balance between runoff, precipitation inputs (as rain or snow), loss by evaporation, and the release or uptake of water by soil moisture and ground water stores, snow cover, glaciers and permafrost, as well as by engineered reservoirs and lakes. In this paper, we estimate these components of the water budgets of the Syr Darya, Amu Darya, Indus, Ganges and Brahmaputra rivers using a combination of station observations, satellite remote sensing and reanalysis output, mass balance measurements, and simple snow cover and glacier models. We estimate the errors for each of these terms with a view to answering the question; how well can we assess glacier and snow melt contributions. Monthly changes in land surface moisture storage are estimated from the difference between runoff and net precipitation (P-E) and also from GRACE. Net precipitation (P-E) is estimated from upper air fields from the NASA MERRA reanalysis using the aerological method and from observations and reanalysis fields of precipitation and evaporation. The challenge is to separate land surface moisture storage into the component reservoirs. Estimates of glacier mass balance in each basin are based on in situ measurements, satellite altimetry, and DEM differencing. Changes in snow storage and contributions from ice melt are estimated using simple accumulation and melt models. Estimates of soil moisture, groundwater and permafrost storage are taken from the literature.

  15. Gulkana Glacier, Alaska-Mass balance, meteorology, and water measurements, 1997-2001

    USGS Publications Warehouse

    March, Rod S.; O'Neel, Shad

    2011-01-01

    The measured winter snow, maximum winter snow, net, and annual balances 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 mass balances and descriptions of ice 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 mass balance trend, especially below the equilibrium line altitude where thinning was pronounced. Ice motion also slowed, which combined with the negative mass balance, 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.

  16. Assessing streamflow sensitivity to variations in glacier mass balance

    USGS Publications Warehouse

    O'Neel, Shad; Hood, Eran; Arendt, Anthony; Sass, Louis

    2014-01-01

    The purpose of this paper is to evaluate relationships among seasonal and annual glacier mass balances, glacier runoff and streamflow in two glacierized basins in different climate settings. We use long-term glacier mass balance 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 mass balance processes impact streamflow, ultimately improving our conceptual understanding of the future evolution of glacier runoff in continental and maritime climates.

  17. Assessing streamflow sensitivity to variations in glacier mass balance

    NASA Astrophysics Data System (ADS)

    Oneel, S.; Hood, E. W.; Arendt, A. A.; Sass, L. C.; March, R. S.

    2013-12-01

    We examine long-term streamflow and mass balance data from two Alaskan glaciers located in climatically distinct basins: Gulkana Glacier, a continental glacier located in the Alaska Range, and Wolverine Glacier, a maritime glacier located in the Kenai Mountains. Both glaciers lost mass, primarily as a result of summer warming, and both basins exhibit increasing streamflow over the 1966-2011 study interval. We estimated total glacier runoff via summer mass balance, and separated the fraction related to annual mass imbalances. In both climates, the fraction of streamflow related to annual mass balance averages less than 20%, substantially smaller than the fraction related to total summer mass loss (>50%), which occurs even in years of glacier growth. The streamflow fraction related to changes in annual mass balance has increased only in the continental environment. In the maritime climate, where deep winter snowpacks and frequent rain events drive consistently high runoff, the magnitude of this streamflow fraction is small and highly variable, precluding detection of any existing trend. Changes in streamflow related to annual balance are often masked by interannual variability of maritime glacier mass balance, such that predicted scenarios of continued glacier recession are more likely to impact the quality and timing of runoff than the total basin water yield.

  18. Mass Gains of the Antarctic Ice Sheet Exceed Losses

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Li, Jun; Robbins, John; Saba, Jack L.; Yi, Donghui; Brenner, Anita; Bromwich, David

    2012-01-01

    During 2003 to 2008, the mass gain of the Antarctic ice sheet from snow accumulation exceeded the mass loss from ice 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 ice 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 ice 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 ice 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 mass 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.

  19. MATRIICES - Mass Analytical Tool for Reactions in Interstellar ICES

    NASA Astrophysics Data System (ADS)

    Isokoski, K.; Bossa, J. B.; Linnartz, H.

    2011-05-01

    The formation of complex organic molecules (COMs) observed in the inter- and circumstellar medium (ISCM) is driven by a complex chemical network yet to be fully characterized. Interstellar dust grains and the surrounding ice mantles, subject to atom bombardment, UV irradiation, and thermal processing, are believed to provide catalytic sites for such chemistry. However, the solid state chemical processes and the level of complexity reachable under astronomical conditions remain poorly understood. The conventional laboratory techniques used to characterize the solid state reaction pathways - RAIRS (Reflection Absorption IR Spectroscopy) and TPD (Temperature-Programmed Desorption) - are suitable for the analysis of reactions in ices made of relatively small molecules. For more complex ices comprising a series of different components as relevant to the interstellar medium, spectral overlapping prohibits unambiguous identification of reaction schemes, and these techniques start to fail. Therefore, we have constructed a new and innovative experimental set up for the study of complex interstellar ices featuring a highly sensitive and unambiguous detection method. MATRIICES (Mass Analytical Tool for Reactions in Interstellar ICES) combines Laser Ablation technique with a molecular beam experiment and Time-Of-Flight Mass Spectrometry (LA-TOF-MS) to sample and analyze the ice analogues in situ, at native temperatures, under clean ultra-high vacuum conditions. The method allows direct sampling and analysis of the ice constituents in real time, by using a pulsed UV ablation laser (355-nm Nd:YAG) to vaporize the products in a MALDI-TOF like detection scheme. The ablated material is caught in a synchronously pulsed molecular beam of inert carrier gas (He) from a supersonic valve, and analysed in a Reflectron Time-of-Flight Mass Spectrometer. The detection limit of the method is expected to exceed that of the regular surface techniques substantially. The ultimate goal is to fully

  20. Mass balance and streamflow variability at Place Glacier, Canada, in relation to recent climate fluctuations

    NASA Astrophysics Data System (ADS)

    Moore, R. D.; Demuth, M. N.

    2001-12-01

    Although a great deal of research has focused on the hydrologic effects of climate variability and change, relatively little research has examined the effects on streamflow of interactions between climate variability and change and resulting glacier response. Place Glacier, in the southern Coast Mountains of British Columbia, Canada, has been monitored for mass balance since 1965, and a stream gauge was operated just below the glacier terminus from 1969 to 1989. This paper presents analyses of the mass balance history and streamflow variations in relation to recorded climatic variability.Place Glacier's winter and net balances are correlated with the Pacific Decadal Oscillation (PDO). Summer balance is positively correlated with summer temperature and negatively with the preceding winter balance, which enhances the effects of changes in winter balance on net balance. The well-documented post-1976 shift from the PDO cold phase to the present warm phase initiated a significant and persistent period of more negative net balance and terminal retreat. A reconstruction of net balance extending back to the 1890s, based on a regression with winter precipitation and summer temperature, displays decadal-scale fluctuations consistent with the PDO. Summer streamflow responded to interannual variations in winter snow accumulation and summer temperatures, which control the rate of rise of the glacier snowline and melt rates. After accounting for these influences via regression analysis, August streamflow displayed a negative trend in total runoff. Examination of air photographs and the reconstructed mass balance history suggest that significant firn depletion had occurred prior to 1965, such that the dominant effect of glacier changes was a reduction in ice area, resulting in decreased meltwater production.

  1. Identifying Dynamically Induced Variability in Glacier Mass-Balance Records

    NASA Astrophysics Data System (ADS)

    Christian, J. E.; Siler, N.; Koutnik, M. R.; Roe, G.

    2015-12-01

    Glacier mass-balance (i.e., accumulation vs. ablation) provides a direct indicator of a glacier's relationship with climate. However, mass-balance records contain noise due to internal climate variability (i.e., from stochastic fluctuations in large-scale atmospheric circulation), which can obscure or bias trends in these relatively short timeseries. This presents a challenge in correctly identifying the signature of anthropogenic change. "Dynamical adjustment" is a technique that identifies patterns of variance shared between a climate timeseries of interest (e.g., mass-balance) and independent "predictor" variables associated with large-scale circulation (e.g., Sea Level Pressure, SLP, or Sea Surface Temperature, SST). Extracting the component of variance due to internal variability leaves a residual timeseries for which trends can more confidently be attributed to external forcing. We apply dynamical adjustments based on Partial Least Squares Regression to mass-balance records from South Cascade Glacier in Washington State and Wolverine and Gulkana Glaciers in Alaska, independently analyzing seasonal balance records to assess the dynamical influences on winter accumulation and summer ablation. Seasonally averaged North Pacific SLP and SST fields perform comparably as predictor variables, explaining 50-60% of the variance in winter balance and 30-40% of variance in summer balance for South Cascade and Wolverine Glaciers. Gulkana glacier, located further inland than the other two glaciers, is less closely linked to North Pacific climate variability, with the predictors explaining roughly one-third of variance in its winter and summer balance. We analyze the significance of linear trends in the raw and adjusted mass-balance records, and find that for all three glaciers, a) summer balance shows a statistically significant downward trend that is not substantially altered when dynamically induced variability is removed, and b) winter balance shows no statistically

  2. Atmospheric Pressure Error of GRACE in Antarctic Ice Mass Change

    NASA Astrophysics Data System (ADS)

    Kim, B.; Eom, J.; Seo, K. W.

    2014-12-01

    As GRACE has observed time-varying gravity longer than a decade, long-term mass changes have been emerged. In particular, linear trends and accelerated patterns in Antarctica were reported and paid attention for the projection of sea level rise. The cause of accelerated ice mass loss in Antarctica is not known since its amplitude is not significantly larger than ice mass change associated with natural climate variations. In this study, we consider another uncertainty in Antarctic ice mass loss acceleration due to unmodeled atmospheric pressure field. We first compare GRACE AOD product with in-situ atmospheric pressure data from SCAR READER project. GRACE AOD (ECMWF) shows spurious jump near Transantarctic Mountains, which is due to the regular model update of ECMWF. In addition, GRACE AOD shows smaller variations than in-situ observation in coastal area. This is possibly due to the lower resolution of GRACE AOD, and thus relatively stable ocean bottom pressure associated with inverted barometric effect suppresses the variations of atmospheric pressure near coast. On the other hand, GRACE AOD closely depicts in-situ observations far from oceans. This is probably because GRACE AOD model (ECMWF) is assimilated with in-situ observations. However, the in-situ observational sites in interior of Antarctica are sparse, and thus it is still uncertain the reliability of GRACE AOD for most region of Antarctica. To examine this, we cross-validate three different reanalysis; ERA Interim, NCEP DOE and MERRA. Residual atmospheric pressure fields as a measure of atmospheric pressure errors, NCEP DOE - ERA Interim or MERRA - ERA Interim, show long-term changes, and the estimated uncertainty in acceleration of Antarctic ice mass change is about 9 Gton/yr^2 from 2003 to 2012. This result implies that the atmospheric surface pressure error likely hinders the accurate estimate of the ice mass loss acceleration in Antarctica.

  3. Shifting balance of thermokarst lake ice regimes across the Arctic Coastal Plain of northern Alaska

    NASA Astrophysics Data System (ADS)

    Arp, C. D.; Jones, B. M.; Lu, Z.; Whitman, M. S.

    2012-08-01

    The balance of thermokarst lakes with bedfast- and floating-ice 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 ice regimes in two regions of the Arctic Coastal Plain of northern Alaska from 2003-2011, we found that 18% of the lakes had intermittent ice regimes, varying between bedfast-ice and floating-ice conditions. Comparing this dataset with a radar-based lake classification from 1980 showed that 16% of the bedfast-ice lakes had shifted to floating-ice regimes. A simulated lake ice 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.

  4. BTD building uranium mass balance study

    SciTech Connect

    Sutter, S.L.; Johnston, J.W.; Glissmeyer, J.A.; Athey, G.F.

    1985-01-01

    Fifteen test firings of depleted uranium (DU) munitions were made during the qualification study of the new target building at the BTD Range operated by the US Army Combat Systems Test Activity (CSTA) at Aberdeen Proving Ground, Maryland. Following these test firings, the total mass and mass distribution of DU inside the BTD facility was determined to define decontamination requirements for the new target building. 4 references, 17 figures, 17 tables.

  5. Effect of GIA models with 3D composite mantle viscosity on GRACE mass balance estimates for Antarctica

    NASA Astrophysics Data System (ADS)

    van der Wal, Wouter; Whitehouse, Pippa L.; Schrama, Ernst J. O.

    2015-03-01

    Seismic data indicate that there are large viscosity variations in the mantle beneath Antarctica. Consideration of such variations would affect predictions of models of Glacial Isostatic Adjustment (GIA), which are used to correct satellite measurements of ice mass change. However, most GIA models used for that purpose have assumed the mantle to be uniformly stratified in terms of viscosity. The goal of this study is to estimate the effect of lateral variations in viscosity on Antarctic mass balance estimates derived from the Gravity Recovery and Climate Experiment (GRACE) data. To this end, recently-developed global GIA models based on lateral variations in mantle temperature are tuned to fit constraints in the northern hemisphere and then compared to GPS-derived uplift rates in Antarctica. We find that these models can provide a better fit to GPS uplift rates in Antarctica than existing GIA models with a radially-varying (1D) rheology. When 3D viscosity models in combination with specific ice loading histories are used to correct GRACE measurements, mass loss in Antarctica is smaller than previously found for the same ice loading histories and their preferred 1D viscosity profiles. The variation in mass balance estimates arising from using different plausible realizations of 3D viscosity amounts to 20 Gt/yr for the ICE-5G ice model and 16 Gt/yr for the W12a ice model; these values are larger than the GRACE measurement error, but smaller than the variation arising from unknown ice history. While there exist 1D Earth models that can reproduce the total mass balance estimates derived using 3D Earth models, the spatial pattern of gravity rates can be significantly affected by 3D viscosity in a way that cannot be reproduced by GIA models with 1D viscosity. As an example, models with 1D viscosity always predict maximum gravity rates in the Ross Sea for the ICE-5G ice model, however, for one of the three preferred 3D models the maximum (for the same ice model) is found

  6. Water, Ice, and Meteorological Measurements at Xiao Dongkemadi Glacier, Central Tibetan Plateau, Balance Years from 2008 to 2011

    NASA Astrophysics Data System (ADS)

    Xiaobo, He; Baisheng, Ye; Yongjian, Ding; Jian, Zhang

    2013-04-01

    The glaciers on Tibetan Plateau play an important role in the catchment hydrology and climatology of this region. However, our knowledge with respect to water circulation in this remote area is scarce. Xiao Dongkemadi Glacier (XDG) is located near Tanggula Pass (the highest point on the Lanzhou-Lhasa road 5231ma.s.l.), central Tibetan Plateau (33°04'N, 92°04'E). Here, glacier mass balance and runoff directly reflects the glacier's response to local climate change, and glacier changes on the Tibetan Plateau strongly influence human welfare since water supplies in this arid/semi-arid region are predominantly from glacier melt. Due to its remote location, the mass balance of XDG has been monitored discontinuously since 1988 by the direct glaciological method. Recently, a more complete and fine-grained glacier monitoring system has been established on the cap of XDG, and is expected to make further contributions to research on the change of the cryospheric and climatic environment in the area. Winter snow accumulation and summer snow and ice ablation were measured at XDG, to estimate glacier mass-balance quantities for balance years from 2008 to 2011. Runoff from the basin containing the glacier and from an adjacent nonglacierized basin was gaged during all or parts of water years from 2008 and 2011. Air temperature, wind speed, precipitation, and incoming solar radiation were measured at selected locations on and near the glacier.

  7. Surface Elevation Changes in West Antarctica from Satellite Altimetry: Mass Balance Implications

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Brenner, Anita C.; Cornejo, Helen; Koblinsky, Chester J. (Technical Monitor)

    2001-01-01

    Time-series of surface elevation change, which are constructed from 7-years (1992-1999) of ERS-1 and 2 satellite radar altimeter data of Antarctica, show significant seasonal, inter-annual, and long-term changes. Elevation time-series are created from altimeter crossovers among 90-day data periods on a 50 km grid to 81.5 degrees S and fit with a multivariate linear/sinusoidal function to give the average rate of elevation change (dH/dt) and account for seasonal changes. On the major Ronne, Filchner, and Ronne ice shelves, the dH/dt 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 a(exp -1) surface elevation decrease on the Larsen ice shelf and a 65 +/- 4 cm a(exp -1) decrease on the Dotson ice shelf. Significant elevation decreases are obtained over most of the drainage basins of the Pine Island and Thwaites glaciers. Significant increases are obtained over most of the other grounded ice in Marie Byrd Land, the Antarctic Peninsula, and Coates Land. Over the sector from 85 degrees W to 115 degrees W, which includes the Pine Island and Thwaites basins, the average elevation is significantly decreasing by 8.1 cm a(exp -1). The corresponding ice thickness change is about -11 cm a(exp -1), with a corresponding mass loss of 82 Gt a(exp -1), and a 0.22 mm a(exp -1) contribution to global sea level rise. In terms of elevation change, the decrease in the Pine Island-Thwaites sector is largely balanced by the increase in the Marie Byrd Land, but only balanced by about 1/4 in terms of ice thickness change and contribution to sea level rise. The overall average elevation change for the grounded ice is + 1.2 cm a(exp -1). Using an average bedrock uplift of 2.5 cm a(exp -1), implies an average ice thickness decrease of 1.3 cm a(exp -1), a mass loss of 22 Gt a(exp -1), and a 0.06 mm a(exp -1) contribution to global sea level rise.

  8. Glacier albedo decrease in the European Alps: potential causes and links with mass balances

    NASA Astrophysics Data System (ADS)

    Di Mauro, Biagio; Julitta, Tommaso; Colombo, Roberto

    2016-04-01

    Both mountain glaciers and polar ice sheets are losing mass all over the Earth. They are highly sensitive to climate variation, and the widespread reduction of glaciers has been ascribed to the atmospheric temperature increase. Beside this driver, also ice albedo plays a fundamental role in defining mass balance of glaciers. In fact, dark ice absorbs more energy causing faster glacier melting, and this can drive to more negative balances. Previous studies showed that the albedo of Himalayan glaciers and the Greenland Ice Sheet is decreasing with important rates. In this contribution, we tested the hypothesis that also glaciers in the European Alps are getting darker. We analyzed 16-year time series of MODIS (MODerate resolution Imaging Spectrometer) snow albedo from Terra (MOD13A1, 2000-2015) and Aqua (MYD13A1, 2002-2015) satellites. These data feature a spatial resolution of 500m and a daily temporal resolution. We evaluated the existence of a negative linear and nonlinear trend of the summer albedo values both at pixel and at glacier level. We also calculated the correlation between MODIS summer albedo and glacier mass balances (from the World Glaciological Monitoring Service, WGMS database), for all the glaciers with available mass balance during the considered period. In order to estimate the percentage of the summer albedo that can be explained by atmospheric temperature, we correlated MODIS albedo and monthly air temperature extracted from the ERA-Interim reanalysis dataset. Results show that decreasing trends exist with a strong spatial variability in the whole Alpine chain. In large glaciers, such as the Aletch (Swiss Alps), the trend varies significantly also within the glacier, showing that the trend is higher in the area across the accumulation and ablation zone. Over the 17 glaciers with mass balance available in the WGMS data set, 11 gave significant relationship with the MODIS summer albedo. Moreover, the comparison between ERA-Interim temperature

  9. The impact of Saharan dust events on long-term glacier mass balance in the Alps

    NASA Astrophysics Data System (ADS)

    Bauder, A.; Gabbi, J.; Huss, M.; Schwikowski, M.

    2014-12-01

    Saharan dust falls are frequently observed in the Alpine region and are easily recognized by the unique yellowish coloration of the snow surface. Such Saharan dust events contribute to a large part to the total mineral dust deposited in snow and impact the surface energy budget by reducing the snow and ice albedo. In this study we investigate the long-term effect of such Saharan dust events on the surface albedo and the glacier's mass balance. The analysis is performed over the period 1914-2013 for two field sites on Claridenfirn, Swiss Alps, where an outstanding 100-year record of seasonal mass balance measurements is available. Based on the detailed knowledge about the mass balance, annual melt and accumulation rates are derived. A firn/ice core drilled at the glacier saddle of Colle Gnifetti (Swiss Alps) provides information on the impurity concentration in precipitation over the last century. A mass balance model combined with a parameterization for snow and ice albedo based on the specific surface area of snow and the snow impurity concentration is employed to assess the dust-albedo feedback. In order to track the position and thickness of snow layers a snow density model is implemented. Atmospheric dust enters the system of snow layers by precipitation and remains in the corresponding layer as long as there is no melt. When melt occurs, the water-insoluble part of the dust of the melted snow is supposed to accumulate in the top surface layer. The upper site has experienced only positive net mass balance and dust layers are continuously buried so that the impact of strong Saharan dust events is mainly restricted to the corresponding year. In the case of the lower site, the surface albedo is more strongly influenced by dust events of previous years due to periods with negative mass balances. Model results suggest that the enhanced melting in the 1940s yield even higher dust concentrations in 1947 compared to years with exceptional high Saharan dust deposition

  10. Surface energy balance and turbulence characteristics observed at the SHEBA Ice Camp during FIRE III

    NASA Astrophysics Data System (ADS)

    Duynkerke, Peter G.; de Roode, Stephan R.

    2001-07-01

    The Institute for Marine and Atmospheric Research Utrecht (IMAU) participated in the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE III) in May 1998. In this paper we describe surface layer measurements performed on the sea ice at the Surface Heat and Energy Balance of the Arctic Ocean (SHEBA) camp and compare these with measurements collected above a grass-covered surface in Cabauw, the Netherlands. The observations consist of both high-frequency turbulence measurements and mean-profile measurements of wind, temperature, and humidity. In addition, we measured the upward and downward components of both the longwave and the shortwave radiation, and the snow and ice temperatures in the upper 40 cm. The observations give a detailed picture of all components of the energy balance of the Arctic sea-ice surface. The turbulence measurements are used to study the surface layer scaling of the turbulence variables in the stable boundary layer. More specifically, we showed that the integral length scale of the vertical velocity fluctuations serves as the relevant turbulence length scale. The monthly averaged energy balance of the Arctic sea-ice was dominated by radiative fluxes, whereas the sensible and latent heat flux and the energy flux into the surface were rather small. A detailed inspection of the diurnal variations in the turbulent fluxes, however, indicates that although the monthly averaged values are small, the hourly averaged values for these fluxes are significant in the surface energy balance.

  11. On the role of submarine melting of tidewater glaciers in driving the Greenland ice sheet out of balance (Invited)

    NASA Astrophysics Data System (ADS)

    Rignot, E. J.; Koppes, M. N.; Velicogna, I.

    2009-12-01

    The Greenland ice sheet is losing mass and the rate of mass loss has been increasing with time. A recent comparison of the components contributing to the mass balance of the ice sheet suggests that half of the signal is caused by an increase in runoff and half by ice dynamics, i.e. the acceleration of outlet glaciers. The root cause of the glacier acceleration is a de-stabilization of the glacier frontal regions, i.e. an un-grounding of the frontal parts which reduces buttressing and allows faster rates of ice sliding to sea. While the role of surface melt water on the lubrication of the glacier bed has been highly publicized, detailed study of the effect of melt water on glacier flow suggest that it can only account for a moderate acceleration of glaciers. De-stabilization of glaciers from vertical thinning is key, yet the increase in runoff is not large enough to explain the observations. We propose instead that submarine melting of the glacier submerged faces has been the main trigger and control. In August 2008, we collected CTD and current measurements in the front of 4 glaciers, 100 km north of Jakobshavn Isbrae, in West Greenland. Calculation of heat and mass flow reveal submarine melt rates ranging from 1 to 3 meters per day, or 100 times larger than the rates of surface melt. Large variations exist from one glacier to the next, but the results suggest that submarine melting is a large contributor to glacier thinning, capable of explaining glacier un-grounding and de-stabilization. Submarine melting removes from 20% to 90% of the ice that reaches the ocean, the rest being discharged as icebergs. Prior studies totally ignored the role of submarine melting in Greenland and only considered iceberg calving. We conclude than more detailed studies of ice-ocean interactions in tidewater glacier environments are absolutely critical to better understand present-day and future evolutions of the Greenland ice sheet in a warming climate.

  12. An ice-cream cone model for coronal mass ejections

    NASA Astrophysics Data System (ADS)

    Xue, X. H.; Wang, C. B.; Dou, X. K.

    2005-08-01

    In this study, we use an ice-cream cone model to analyze the geometrical and kinematical properties of the coronal mass 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 ice-cream cone. This model is improved by (1) using an ice-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.

  13. Correction of Correlation Errors in Greenland Ice Mass Variations from GRACE using Empirical Orthogonal Function

    NASA Astrophysics Data System (ADS)

    Eom, J.; Seo, K. W.

    2015-12-01

    Since its launch in March 2002, the Gravity Recovery And Climate Experiment (GRACE) has provided monthly geopotential fields represented by Stokes coefficients of spherical harmonics (SH). Nominally, GRACE gravity solutions exclude effects from tides, ocean dynamics and barometric pressure by incorporating geophysical models for them. However, those models are imperfect, and thus GRACE solutions include the residual gravity effects. Particularly, unmodeled gravity variations of sub-monthly or shorter time scale cause aliasing error, which produces peculiar longitudinal stripes. Those north-south patterns are removed by spatial filtering, but caution is necessary for the aliasing correction because signals with longitudinal patterns are possibly removed during the procedure. This would be particularly problematic for studies associated with Greenland ice mass balance since large ice mass variations are expected in the West and South-West coast of Greenland that are elongated along the longitudinal direction. In this study, we develop a novel method to remove the correlation error using extended Empirical Orthogonal Function (extended EOF). The extended EOF is useful to separate spatially and temporally coherent signal from high frequency variations. Since temporal variability of the correlation error is high, the error is possibly removed via the extended EOF. Ice mass variations reduced by the extended EOF show more detail patterns of ice mass loss/gain than those from the conventional spatial filtering. Large amount of ice loss has occurred along the West, South-West and East coastal area during summer. The extended EOF is potentially useful to enhance signal to noise ratio and increase spatial resolution of GRACE data.

  14. A Simple Watt Balance for the Absolute Determination of Mass

    ERIC Educational Resources Information Center

    Quinn, Terry; Quinn, Lucas; Davis, Richard

    2013-01-01

    A watt balance is an electromechanical device that allows a mass to be determined in terms of measurable electrical and mechanical quantities, themselves traceable to the fundamental constants of physics. International plans are well advanced to redefine the unit of mass, the kilogram, in terms of a fixed numerical value for the Planck constant. A…

  15. Modelling mass balance and temperature sensitivity on Shallap glacier, Peru

    NASA Astrophysics Data System (ADS)

    Gurgiser, W.; Marzeion, B.; Nicholson, L. I.; Ortner, M.; Kaser, G.

    2013-12-01

    Due to pronounced dry seasons in the tropical Andes of Peru glacier melt water is an important factor for year-round water availability for the local society. Andean glaciers have been shrinking during the last decades but present day's magnitudes of glacier mass balance and sensitivities to changes in atmospheric drivers are not well known. Therefore we have calculated spatial distributed glacier mass and energy balance of Shallap glacier (4700 m - 5700 m, 9°S), Cordillera Blanca, Peru, on hourly time steps for the period Sept. 2006 to Aug. 2008 with records from an AWS close to the glacier as model input. Our model evaluation against measured surface height change in the ablation zone of the glacier yields our model results to be reasonable and within an expectable error range. For the mass balance characteristics we found similar vertical gradients and accumulation area ratios but markedly differences in specific mass balance from year to year. The differences were mainly caused by large differences in annual ablation in the glacier area below 5000m. By comparing the meteorological conditions in both years we found for the year with more negative mass balance that total precipitation was only slightly lower but mean annual temperature was higher, thus the fraction of liquid precipitation and the snow line altitude too. As shortwave net energy turned out to be the key driver of ablation in all seasons the deviations in snow line altitude and surface albedo explain most of the deviations in available melt energy. Hence, mass balance of tropical Shallap glacier was not only sensitive to precipitation but also to temperature which has not been expected for glaciers in the Peruvian Andes before. We furthermore have investigated impacts of increasing temperature due to its multiple effects on glacier mass and energy balance (fraction of liquid precipitation, long wave incoming radiation, sensible and latent heat flux). Presenting these results should allow for better

  16. On the use of the point-mass modeling technique for assessing ice-mass variations in alpine glacier systems

    NASA Astrophysics Data System (ADS)

    Reimond, Stefan; Baur, Oliver; Krauss, Sandro

    2016-04-01

    Most scientific studies dealing with gravity-based ice-mass balance estimations focus on the Earth's continental glacier systems, namely the Greenland and the Antarctica ice sheets. Alpine glacier regions such as the Alps, Himalaya or Patagonia, on the other hand, seem to be less considered. According to the most recent assessment report of the Intergovernmental Panel on Climate Change (IPCC), however, glacier shrinkage is one of the most dominant contributors to global sea level rise. In this context we investigate the capability of the point-mass modeling technique to assess ice-mass variations in small-scale alpine regions from space-borne gravimetric data. Two different approaches of this method can be distinguished: point-mass modeling with (i) predefined and fixed positions and (ii) with unknown locations of the surface mass changes. Approach (i) yields a linear functional model in which only the magnitudes of the point-masses are considered unknown. A highly non-linear optimization problem needs to be solved for approach (ii), since both the magnitudes and the coordinates of the point-masses are introduced as unknown parameters. In addition to that, owing to the effect of downward continuation, this problem is categorized as ill-posed and needs to be remedied by introducing regularization. The L-curve criterion or the generalized cross-validation method are typically used for selecting a suitable regularization factor. We conducted a series of close-loop simulation tests for various alpine glacier systems to compare the two approaches. In order to solve the global optimization problems in (i) and (ii), we make use of genetic algorithms.

  17. Breaking Off of Large Ice Masses From Hanging Glaciers

    NASA Astrophysics Data System (ADS)

    Pralong, A.; Funk, M.

    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 ice masses is required. At present, the most promising approach for such a prediction is based on the regularity by which certain large ice masses 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 ice, 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 ice, damage inhomogene- ity) and inhomogeneous boundary conditions on the damage repartition are especially investigated.

  18. Recent evolution and mass balance of Cordón Martial glaciers, Cordillera Fueguina Oriental

    NASA Astrophysics Data System (ADS)

    Strelin, Jorge; Iturraspe, Rodolfo

    2007-10-01

    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 ice-proximal ("internal") moraines of Cordón Martial, around 330 14C yr BP, during the Late Little Ice 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 ice mass (0.59 ± 0.02 × 10 6 m 3 w.e.), corresponding to an average ice 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 mass balance measured since March 2000, document the annual response of the Martial Este Glacier to the climate variation. Mass balances 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.

  19. A high-resolution record of Greenland mass balance

    NASA Astrophysics Data System (ADS)

    McMillan, Malcolm; Leeson, Amber; Shepherd, Andrew; Briggs, Kate; Armitage, Thomas W. K.; Hogg, Anna; Kuipers Munneke, Peter; Broeke, Michiel; Noël, Brice; Berg, Willem Jan; Ligtenberg, Stefan; Horwath, Martin; Groh, Andreas; Muir, Alan; Gilbert, Lin

    2016-07-01

    We map recent Greenland Ice Sheet elevation change at high spatial (5 km) and temporal (monthly) resolution using CryoSat-2 altimetry. After correcting for the impact of changing snowpack properties associated with unprecedented surface melting in 2012, we find good agreement (3 cm/yr bias) with airborne measurements. With the aid of regional climate and firn modeling, we compute high spatial and temporal resolution records of Greenland mass evolution, which correlate (R = 0.96) with monthly satellite gravimetry and reveal glacier dynamic imbalance. During 2011-2014, Greenland mass loss averaged 269 ± 51 Gt/yr. Atmospherically driven losses were widespread, with surface melt variability driving large fluctuations in the annual mass deficit. Terminus regions of five dynamically thinning glaciers, which constitute less than 1% of Greenland's area, contributed more than 12% of the net ice loss. This high-resolution record demonstrates that mass deficits extending over small spatial and temporal scales have made a relatively large contribution to recent ice sheet imbalance.

  20. Neutrino mass hierarchy extraction using atmospheric neutrinos in ice

    SciTech Connect

    Mena, Olga; Mocioiu, Irina; Razzaque, Soebur

    2008-11-01

    We show that the measurements of 10 GeV atmospheric neutrinos by an upcoming array of densely-packed phototubes buried deep inside the IceCube detector at the South Pole can be used to determine the neutrino mass hierarchy for values of sin{sup 2}2{theta}{sub 13} close to the present bound, if the hierarchy is normal. These results are obtained for an exposure of 100 Mton years and systematic uncertainties up to 10%.

  1. Modelling The Energy And Mass Balance Of A Black Glacier

    NASA Astrophysics Data System (ADS)

    Grossi, G.; Taschner, S.; Ranzi, R.

    A distributed energy balance 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/ice/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 ice-melt, while the sensible heat turns out to be the second major source of heat. Longwave radiation balance 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 ice 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 ice, debris covered ice, rock), proved by the energy balance model results was

  2. Reducing uncertainties in projections of Antarctic ice mass loss

    NASA Astrophysics Data System (ADS)

    Durand, G.; Pattyn, F.

    2015-11-01

    Climate model projections are often aggregated into multi-model averages of all models participating in an intercomparison project, such as the Coupled Model Intercomparison Project (CMIP). The "multi-model" approach provides a sensitivity test to the models' structural choices and implicitly assumes that multiple models provide additional and more reliable information than a single model, with higher confidence being placed on results that are common to an ensemble. A first initiative of the ice sheet modeling community, SeaRISE, provided such multi-model average projections of polar ice sheets' contribution to sea-level rise. The SeaRISE Antarctic numerical experiments aggregated results from all models devoid of a priori selection, based on the capacity of such models to represent key ice-dynamical processes. Here, using the experimental setup proposed in SeaRISE, we demonstrate that correctly representing grounding line dynamics is essential to infer future Antarctic mass change. We further illustrate the significant impact on the ensemble mean and deviation of adding one model with a known bias in its ability of modeling grounding line dynamics. We show that this biased model can hardly be identified from the ensemble only based on its estimation of volume change, as ad hoc and untrustworthy parametrizations can force any modeled grounding line to retreat. However, tools are available to test parts of the response of marine ice sheet models to perturbations of climatic and/or oceanic origin (MISMIP, MISMIP3d). Based on recent projections of Pine Island Glacier mass loss, we further show that excluding ice sheet models that do not pass the MISMIP benchmarks decreases the mean contribution and standard deviation of the multi-model ensemble projection by an order of magnitude for that particular drainage basin.

  3. Evaluation of three long term mass balance records in Jotunheimen, southern Norway

    NASA Astrophysics Data System (ADS)

    Andreassen, Liss M.

    2013-04-01

    The accuracy of glacier surface mass-balance measurements depends on both the accuracy of the point observations and inter- and extrapolation of point values to spatially distributed values. Long series of measurements will seldom be perfectly homogeneous because of changes in personnel and procedure, and as there will be changes in glacier area (and elevation) when averaging the data. The Jotunheimen massif is the highest area in mainland Norway. Direct surface mass balance has been measured at Storbreen since 1949 and Hellstugubreen and Gråsubreen since 1962. These three mountain glaciers are reference glaciers of the World Glacier Monitoring Service. Four more glaciers in Jotunheimen were measured for shorter periods in the 1960/1970s. Moreover, measurements started on a small ice patch in 2010. The reference glaciers have been mapped repeatedly since measurements began, latest by laser scanning in 2009. The geodetic method has been used to calculate the cumulative surface mass balance. In this study the direct and geodetic mass balance results are presented and evaluated. Measurements reveal a remarked mass balance gradient in this region with smaller mass turnover towards east. All three long term glaciers have had a cumulative mass deficit since measurements began; over 1962-2010 the mean surface mass balance was -0.34 m w.e./a. The mass deficit has accelerated over the past decade, and the mean mass balance over 2001-2010 was -0.84 m w.e./a. Storbreen has lost about 1/5 of its volume since measurements began in 1949. Results reveal that the geodetic and direct measurements compare well for the glaciers, also for the latest mapping period 1997-2009, although discrepancies occur in some periods. Calibration and correction of the direct records with the geodetic results may be appropriate for some periods. The glacier changes of the three reference glaciers are finally compared with results from other glaciers in southern Norway for evaluation of the local and

  4. Influence of Persistent Wind Scour on the Surface Mass Balance of Antarctica

    NASA Technical Reports Server (NTRS)

    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.

    2013-01-01

    Accurate quantification of surface snow accumulation over Antarctica is a key constraint for estimates of the Antarctic mass balance, as well as climatic interpretations of ice-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 mass balance rely on sparse point measurements or coarse atmospheric models that do not capture these local processes, and overestimate the net mass 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 mass input is overestimated by 11-36.5 Gt /yr in present surface-mass-balance calculations.

  5. Force, mass, and energy budgets of the Crary Ice Rise complex, Antarctica

    NASA Technical Reports Server (NTRS)

    Macayeal, D. R.; Bindschadler, R. A.; Stephenson, S.; Shabtaie, S.; Bentley, C. R.

    1987-01-01

    The stress, mass, and energy-dissipation budgets of Crary Ice Rise are analyzed using field data collected during the 1983-1985 austral summers and in previous field programs. In addition, the net back pressure and ice-discharge rate along the grounding lines of ice streams are calculated to assess the effect of the ice rise on the surrounding flow. Comparison of the ice-rise budgets with the analysis of grounding-line data confirms the influence of the ice rise on ice-sheet stability, and suggests that Crary Ice Rise may have formed recently in response to an acceleration of one of the ice streams. It is concluded that feedback between ice-stream acceleration and ice-rise formation may control the future evolution of the above ice stream and promote long-term grounding-line stability in the face of strong natural fluctuations.

  6. Constraining the recent mass balance of Pine Island and Thwaites glaciers, West Antarctica, with airborne observations of snow accumulation

    NASA Astrophysics Data System (ADS)

    Medley, B.; Joughin, I.; Smith, B. E.; Das, S. B.; Steig, E. J.; Conway, H.; Gogineni, S.; Lewis, C.; Criscitiello, A. S.; McConnell, J. R.; van den Broeke, M. R.; Lenaerts, J. T. M.; Bromwich, D. H.; Nicolas, J. P.; Leuschen, C.

    2014-07-01

    In Antarctica, uncertainties in mass input and output translate directly into uncertainty in glacier mass balance and thus in sea level impact. While remotely sensed observations of ice velocity and thickness over the major outlet glaciers have improved our understanding of ice loss to the ocean, snow accumulation over the vast Antarctic interior remains largely unmeasured. Here, we show that an airborne radar system, combined with ice-core glaciochemical analysis, provide the means necessary to measure the accumulation rate at the catchment-scale along the Amundsen Sea coast of West Antarctica. We used along-track radar-derived accumulation to generate a 1985-2009 average accumulation grid that resolves moderate- to large-scale features (>25 km) over the Pine Island-Thwaites glacier drainage system. Comparisons with estimates from atmospheric models and gridded climatologies generally show our results as having less accumulation in the lower-elevation coastal zone but greater accumulation in the interior. Ice discharge, measured over discrete time intervals between 1994 and 2012, combined with our catchment-wide accumulation rates provide an 18-year mass balance history for the sector. While Thwaites Glacier lost the most ice in the mid-1990s, Pine Island Glacier's losses increased substantially by 2006, overtaking Thwaites as the largest regional contributor to sea-level rise. The trend of increasing discharge for both glaciers, however, appears to have leveled off since 2008.

  7. Constraining the recent mass balance of Pine Island and Thwaites glaciers, West Antarctica with airborne observations of snow accumulation

    NASA Astrophysics Data System (ADS)

    Medley, B.; Joughin, I.; Smith, B. E.; Das, S. B.; Steig, E. J.; Conway, H.; Gogineni, S.; Lewis, C.; Criscitiello, A. S.; McConnell, J. R.; van den Broeke, M. R.; Lenaerts, J. T. M.; Bromwich, D. H.; Nicolas, J. P.; Leuschen, C.

    2014-02-01

    In Antarctica, uncertainties in mass input and output translate directly into uncertainty in glacier mass balance and thus in sea level impact. While remotely sensed observations of ice velocity and thickness over the major outlet glaciers have improved our understanding of ice loss to the ocean, snow accumulation over the vast Antarctic interior remains largely unmeasured. Here, we show that an airborne radar system, combined with ice-core glaciochemical analysis, provide the means necessary to measure the accumulation rate at the catchment-scale along the Amundsen Sea Coast of West Antarctica. We used along-track radar-derived accumulation to generate a 1985-2009 average accumulation grid that resolves moderate- to large-scale features (> 25 km) over the Pine Island-Thwaites glacier drainage system. Comparisons with estimates from atmospheric models and gridded climatologies generally show our results as having less accumulation in lower-elevation coastal zone but greater accumulation in the interior. Ice discharge, measured over discrete time intervals between 1994 and 2012, combined with our catchment-wide accumulation rates provide an 18 yr mass balance history for the sector. While Thwaites Glacier lost the most ice in the mid-1990s, Pine Island Glacier's losses increased substantially by 2006, overtaking Thwaites as the largest regional contributor to sea-level rise. The trend of increasing discharge for both glaciers, however, appears to have leveled off since 2008.

  8. Analysis of difference between direct and geodetic mass balance measurements at South Cascade Glacier, Washington

    USGS Publications Warehouse

    Krimmel, R.M.

    1999-01-01

    Net mass balance has been measured since 1958 at South Cascade Glacier using the 'direct method,' e.g. area averages of snow gain and firn and ice loss at stakes. Analysis of cartographic vertical photography has allowed measurement of mass balance 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 balance of about -15 m, and the geodetic method shows a cumulative balance 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 mass 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.

  9. North Cascade Glacier Annual Mass Balance Record Analysis 1984-2013

    NASA Astrophysics Data System (ADS)

    Pelto, M. S.

    2014-12-01

    The North Cascade Glacier Climate Project (NCGCP) was founded in 1983 to monitor 10 glaciers throughout the range and identify their response to climate change. The annual observations include mass balance, terminus behavior, glacier surface area and accumulation area ratio (AAR). Annual mass balance (Ba) measurements have been continued on the 8 original glaciers that still exist. Two glaciers have disappeared: the Lewis Glacier and Spider Glacier. In 1990, Easton Glacier and Sholes Glacier were added to the annual balance program to offset the loss. One other glacier Foss Glacier has declined to the extent that continued measurement will likely not be possible. Here we examine the 30 year long Ba time series from this project. All of the data have been reported to the World Glacier Monitoring Service (WGMS). This comparatively long record from glaciers in one region conducted by the same research program using the same methods offers some useful comparative data. Degree day factors for melt of 4.3 mm w.e.°C-1d-1 for snow and 6.6 mm w.e.°C-1d-1 for ice has been determined from 412 days of ablation observation. The variation in the AAR for equilibrium Ba is small ranging from 60 to 67. The mean annual balance of the glaciers from 1984-2013 is -0.45 ma-1, ranging from -0.31 to -0.57 ma-1 for individual glacier's. The correlation coefficient of Ba is above 0.80 between all glaciers including the USGS benchmark glacier, South Cascade Glacier. This indicates that the response is to regional climate change, not local factors. The mean annual balance of -0.45 ma-1 is close to the WGMS global average for this period -0.50 ma-1. The cumulative loss of 13.5 m w.e. and 15 m of ice thickness represents more than 20% of the volume of the glaciers.

  10. Large Ice Discharge From the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Rignot, Eric

    1999-01-01

    The objectives of this work are to measure the ice discharge of the Greenland Ice Sheet close to the grounding line and/or calving front, and compare the results with mass accumulation and ablation in the interior to estimate the ice sheet mass balance.

  11. Radionuclide mass balance for the TMI-2 accident: data-base system and preliminary mass balance. Volume 1

    SciTech Connect

    Goldman, M I; Davis, R J; Strahl, J F; Arcieri, W C; Tonkay, D W

    1983-04-01

    After the accident at Three Mile Island, Unit 2 (TMI-2), on March 28, 1979, GEND stated its intention to support an effort to determine, as accurately as possible, the current mass balances of significant radiological toxic species. GEND gave two primary reasons for support this effort: (1) such exercises guarantee completeness of the studies, and (2) mass balance determinations ensure that all important sinks and attentuation mechanisms have been identified. The primary objective of the studies conducted by NUS Corporation was to support the goals of the GEND planners and to continue the mass balance effort by generating a preliminary accounting of key radioactive species following the TMI-2 accident. As a result of these studies, secondary objectives, namely a computerized data base and recommendations, have been achieved to support future work in this area.

  12. Climate dependent contrast in surface mass balance in East Antarctica over the past 216 kyr

    NASA Astrophysics Data System (ADS)

    Parrenin, F.; Fujita, S.; Abe-Ouchi, A.; Kawamura, K.; Masson-Delmotte, V.; Motoyama, H.; Saito, F.; Severi, M.; Stenni, B.; Uemura, R.; Wolff, E.

    2015-02-01

    Documenting past changes in the East Antarctic surface mass balance is important to improve ice core chronologies and to constrain the ice sheet contribution to global mean sea level. Here we reconstruct the past changes in the ratio of surface mass balance (SMB ratio) between the EPICA Dome C (EDC) and Dome Fuji (DF) East Antarctica ice core sites, based on a precise volcanic synchronisation of the two ice 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 ice core chronologies at DF and EDC. Such changes in SMB ratio may have been caused by (i) climatic processes related to changes in air mass 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 ice sheet modeling (for which SMB is a boundary condition) or atmospheric

  13. Greenland Ice Sheet Mass Loss and Outlet Glacier Dynamics from Laser Altimetry Record (1993-2013) (Invited)

    NASA Astrophysics Data System (ADS)

    Csatho, B. M.; Schenk, A. F.; Duncan, K.; Babonis, G. S.; Sonntag, J. G.; Krabill, W. B.; van den Broeke, M. R.; van Angelen, J.; Blair, J. B.; Hofton, M. A.

    2013-12-01

    .P. Bernstorff Glacier) after the brief period of thickening observed in 2006-2009. Increasing thinning would imply that earlier decrease in dynamic mass loss represented a short-term trend, rather than a new balance state of the ice sheet. In NE Greenland, continuing thinning at the grounding zones of Ryder, Zachariae and Nioghalvfjerdsfjorden glaciers could lead to retreat, flow acceleration and increasing mass loss as the ice plains buttressing these glaciers will become ungrounded in a region where the bed is under sea level.

  14. Quantifying the influence of refreezing melt water on the mass balance and runoff of Freya Glacier in Northeast-Greenland

    NASA Astrophysics Data System (ADS)

    Resch, G.; Weyss, G.; Hynek, B.; Schöner, W.; Glade, T.

    2012-04-01

    Refreezing of melt water is known to play an important role in both the mass and energy budgets of Arctic glaciers as internal accumulation leads to a systematic error in mass balance calculation if it is not accounted for. A variety of measurements with the aim of quantification of refreezing of melt water have been done in August 2011 on Freya Glacier, 6 km long valley glacier situated on Clavering Island, 10 km southwest of the Zackenberg research station (ZERO), situated on the northeast coast of Greenland. Its surface area is 6,6km2, reaching from 330 m to 1250 m a.s.l. and is mainly oriented to NW. Since 2007, the mass balance of Freya-Glacier is measured directly, using around 15 stakes, which represents a unique database in this area. Besides surface mass balance, firn and ice stratigraphy in shallow cores and with GPR, also discharge measurements have been done. Thermistor strings have been drilled into the ice and mounted on poles for continuous data collection of ice- and snow temperatures during the winter season. Furthermore, an AWS near the ELA has been set-up for measuring all terms needed for energy balance calculations. Shallow ice cores (2m) and snow pits serve as point information in combination with data collected by a 900Mhz GPR-profile along the flow line and the SI-zone to identify annual SI-Layers. Mapping of the retreat of the snowline with GPS, frequent reading of the ablation stakes and snow depth in combination with discharge measurements have been carried out through the ablation season, to get information about meltwater retention on a basinscale. These data serve as input for a thermodynamic, physical based mass-balance and runoff model to investigate melt water retention and water balance on a basin scale. In this poster we present first results of data analysis, especially on bias and variability between discharge measurements and stake-based mass balance calculations. Besides that, a comparison between these measurements and data

  15. LAKE MICHIGAN MASS BALANCE: ATRAZINE MODELING AND LOADS

    EPA Science Inventory

    The Lake Michigan Mass Balance Study measured PCBs, mercury, trans-nonachlor, and atrazine in rivers, the atmosphere, sediments, lake water, and the food chain. A mathematical model will predict what effect reducing pollution will have on the lake, and its large fish (lake trout ...

  16. Mass balance approaches to understanding evolution of dripwater chemistry

    NASA Astrophysics Data System (ADS)

    Fairchild, I. J.; Baker, A.; Andersen, M. S.; Treble, P. C.

    2015-12-01

    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 mass balance: a fundamental principle that provides important constraints. Mass balance 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 mass balance 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. Mass balance 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.

  17. LAKE MICHIGAN MASS BALANCE STUDY: PROGNOSIS FOR PCBS

    EPA Science Inventory

    The Lake Michigan Mass Balance 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 ...

  18. MODELLING SEDIMENT TRANSPORT FOR THE LAKE MICHIGAN MASS BALANCE PROJECT

    EPA Science Inventory

    A sediment transport model is one component of the overall ensemble of models being developed for the Lake Michigan Mass Balance. The SEDZL model is being applied to simulate the fine-grained sediment transport in Lake Michigan for the 1982-1983 and 1994-1995 periods. Model perf...

  19. CHEMICAL MASS BALANCE MODEL: EPA-CMB8.2

    EPA Science Inventory

    The Chemical Mass Balance (CMB) method has been a popular approach for receptor modeling of ambient air pollutants for over two decades. For the past few years the U.S. Environmental Protection Agency's Office of Research and Development (ORD) and Office of Air Quality Plannin...

  20. On the Contribution of Clouds to Greenland Ice Sheet Mass Loss

    NASA Astrophysics Data System (ADS)

    Van Tricht, K.; Lhermitte, S.; Lenaerts, J.; Gorodetskaya, I.; L'Ecuyer, T. S.; Noel, B.; van den Broeke, M. R.; Turner, D. D.; Van Lipzig, N. P. M.

    2015-12-01

    The Greenland ice sheet (GrIS) has become one of the main contributors to global mean sea level rise, predominantly explained by a decreasing surface mass balance (SMB). Clouds are known to have a strong influence on the surface energy budget, which in consequence impacts the SMB. For example, the potentially important role of thin liquid-bearing clouds over Greenland in enhancing ice sheet melt has recently gained interest. Yet, current research is spatially and temporally limited, focusing on particular events and cloud types, while the large-scale impact of all clouds on the SMB remains unknown. Using a unique cloud product covering the entire GrIS over the period 2007-2010, consisting of active satellite remote sensing data, ground-based observations and climate model data, together with snow model simulations, we investigate the cloud radiative effect over the GrIS and the consequences for the SMB. We show a strong sensitivity of the GrIS to clouds, with a complex interplay between enhanced and reduced mass loss. We further distinguish between ice-only and liquid-bearing clouds, temporal and spatial variations in cloud impacts, and we demonstrate the large spread in simulated clouds by state-of-the-art climate models. Our results therefore urge the need for accurate cloud representations in climate models, to improve future projections of GrIS SMB and global sea level rise.

  1. California's Snow Gun and its implications for mass balance predictions under greenhouse warming

    NASA Astrophysics Data System (ADS)

    Howat, I.; Snyder, M.; Tulaczyk, S.; Sloan, L.

    2003-12-01

    Precipitation has received limited treatment in glacier and snowpack mass balance models, largely due to the poor resolution and confidence of precipitation predictions relative to temperature predictions derived from atmospheric models. Most snow and glacier mass balance 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 ice volume under greenhouse warming. However, positive trends in the mass balance of glaciers in some warming maritime climates, as well as at high elevations of the Greenland Ice 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 mass

  2. Method of Manufacturing a Micromechanical Oscillating Mass Balance

    NASA Technical Reports Server (NTRS)

    Altemir, David A. (Inventor)

    1999-01-01

    A micromechanical oscillating mass balance 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 mass of the beam increases and the resonant frequency of the beam shifts, and the mass added is determined.

  3. Isospin effects on the mass dependence of the balance energy

    SciTech Connect

    Gautam, Sakshi; Sood, Aman D.

    2010-07-15

    We study the effect of isospin degree of freedom on balance energy throughout the mass range between 50 and 350 for two sets of isotopic systems with N/A= 0.54 and 0.57 as well as isobaric systems with N/A= 0.5 and 0.58. Our findings indicate that different values of balance energy for two isobaric systems may be mainly due to the Coulomb repulsion. We also demonstrate clearly the dominance of Coulomb repulsion over symmetry energy.

  4. A review of remote sensing methods for glacier mass balance determination

    NASA Astrophysics Data System (ADS)

    Bamber, Jonathan L.; Rivera, Andres

    2007-10-01

    Airborne and satellite remote sensing is the only practical approach for deriving a wide area, regional assessment of glacier mass balance. A number of remote sensing approaches are possible for inferring the mass balance from some sort of proxy estimate. Here, we review the key methods relevant, in particular to Andean glaciers, discussing their strengths and weaknesses, and data sets that could be more fully exploited. We also consider future satellite missions that will provide advances in our observational capabilities. The methods discussed include observation of elevation changes, estimation of ice flux, repeat measurement of changes in spatial extent, snowline elevation and accumulation-ablation area ratio estimation. The methods are illustrated utilising a comprehensive review of results obtained from a number of studies of South American glaciers, focusing specifically on the Patagonian Icefields. In particular, we present some new results from Glaciar Chico, Southern Patagonian Icefield, Chile, where a variety of different satellite and in-situ data have been combined to estimate mass balance using a geodetic or elevation change approach over about a 25 yr period.

  5. A better GRACE solution for improving the regional Greenland mass balance

    NASA Astrophysics Data System (ADS)

    Schrama, E.; Xu, Z.

    2012-04-01

    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 mass variations are represented as equivalent water height (EWH). Such maps are capable of exposing the redistribution of earth surface mass over time. In Greenland the shrinking of the ice 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 mass 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 mass distribution function on each basin. In this way we are able to estimate more accurately regional ice 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 mass balance (SMB) and ice-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

  6. Mass balance and hydrological contribution of glaciers in northern and central Chile

    NASA Astrophysics Data System (ADS)

    MacDonell, Shelley; Vivero, Sebastian; McPhee, James; Ayala, Alvaro; Pellicciotti, Francesca; Campos, Cristian; Caro, Dennys; Ponce, Rodrigo

    2016-04-01

    Water is a critical resource in the northern and central regions of Chile, as the area supports more than 40% of the country's population, and the regional economy depends on agricultural production and mining, which are two industries that rely heavily on a consistent water supply. Due to relatively low rates of rainfall, meltwater from snow and ice bodies in the highland areas provides a key component of the annual water supply in these areas. Consequently, accurate estimates of the rates of ablation of the cryosphere (i.e. snow and ice) are crucial for predicting current supply rates, and future projections. Whilst snow is generally a larger contributor of freshwater, during periods of drought, glaciers provide a significant source. This study aims to determine the contribution of glaciers to two catchments in northern and central Chile during a 2.5 year period, which largely consisted of extreme dry periods, but also included the recent El Niño event. This study combined field and modelling studies to understand glacier and rock glacier contributions in the Tapado (30°S), Yeso (33°S) catchments. In the field we undertook glaciological mass balance monitoring of three glaciers, monitored albedo and snow line changes using automatic cameras for three glaciers, measured discharge continuously at several points, installed six automatic weather stations and used thermistors to monitor thermal regime changes of two rock glaciers. The combination of these datasets where used to drive energy balance and hydrological models to estimate the contribution of ice bodies to streamflow in the two studied catchments. Over the course of the study all glaciers maintained a negative mass balance, however glaciers in central Chile lost more mass, which is due to the higher melt rates experienced due to lower elevations and higher temperatures. Areas free of debris generally contributed more to streamflow than sediment covered regions, and snow generally contributed more over

  7. Climate, not atmospheric deposition, drives the biogeochemical mass-balance of a mountain watershed

    USGS Publications Warehouse

    Baron, Jill S.; Heath, Jared

    2014-01-01

    Watershed mass-balance methods are valuable tools for demonstrating impacts to water quality from atmospheric deposition and chemical weathering. Owen Bricker, a pioneer of the mass-balance method, began applying mass-balance 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 ice and this may release elements entrained in the ice, 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.

  8. Troughs in Ice Sheets and Other Icy Deposits on Mars: Analysis of Their Radiative Balance

    NASA Astrophysics Data System (ADS)

    Fountain, A.; Kargel, J.; Lewis, K.; MacAyeal, D.; Pfeffer, T.; Zwally, H. J.

    2000-08-01

    It has long been known that groove-like structures in glaciers and ice 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 balance model presented by Pfeffer and Bretherton. Their model considers the visible band radiation regime of a V-shaped groove on a terrestrial ice 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 ice 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 ice, carbon-dioxide ice and dust) of the Martian ice sheets and valley fills.

  9. Troughs in Ice Sheets and Other Icy Deposits on Mars: Analysis of Their Radiative Balance

    NASA Technical Reports Server (NTRS)

    Fountain, A.; Kargel, J.; Lewis, K.; MacAyeal, D.; Pfeffer, T.; Zwally, H. J.

    2000-01-01

    It has long been known that groove-like structures in glaciers and ice 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 balance model presented by Pfeffer and Bretherton. Their model considers the visible band radiation regime of a V-shaped groove on a terrestrial ice 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 ice 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 ice, carbon-dioxide ice and dust) of the Martian ice sheets and valley fills.

  10. A high detail benchmark dataset of mid-1980's ice margin positions for all Greenland ice masses

    NASA Astrophysics Data System (ADS)

    Citterio, M.; Ahlstrom, A. P.

    2012-12-01

    We introduce the first complete high resolution aerophotogrammetric map of Greenland ice masses, including both the ice sheet and all local glaciers and ice caps (GIC). This PROMICE (Programme for Monitoring of the Greenland Ice Sheet) product is based on 1:150.000 scale vertical aerial photographs acquired between 1978 and 1987. The flight campaigns covered N and most of NE Greenland in 1978, E and SE Greenland in 1981, all of the west coast from 60°N to 87°N in 1985, and the remaining part of NE Greenland in 1987. Over the following decades, 1:100,000 and 1:250,000 scale topographic maps were produced by GEUS (Geological Survey of Denmark and Greenland), formerly GGU (Greenland Geological Survey) and by KMS (Danish National Survey and Cadastre). KMS also surveyed the vast majority of geodetic ground control points used for aerotriangulation. We manually edited the vector polygons from these topographic maps to correct issues related to debris covered ice, medial moraines, supraglacial lakes and ice contact lakes. The local ice masses in topological contact with the ice sheet but clearly independent in their ablation and accumulation areas were separated from the ice sheet by manually digitizing ice divides based on surface topography, resulting in all polygons belonging to one of the 'disconnected ice mass', 'local ice mass' or 'ice sheet' classes. The total glacierized area of the ice sheet and GIC in the 1980's was 1,804,638 km2 ± 27,268 km2 and the GIC alone covered 88,083 ± 1,240 km2. This GIC extent is significantly larger than most previously reported estimates, and it is in line with the area of 89,273 ± 2,767 km2 found independently by Rastner et al. (The Cryosphere Discuss., in review) using 1999-2002 30 m Landsat 7 imagery for ice masses with 'no or weak connection' to the ice sheet. It is not possible to assess glacier change by comparing these two aggregate totals because they are indistinguishable within the reported uncertainties, and also

  11. Determining the necessary conditions for Martian cloud formation: Ice nucleation in an electrodynamic balance (EDB)

    NASA Astrophysics Data System (ADS)

    Berlin, S.; Bauer, A. J.; Cziczo, D. J.

    2013-12-01

    The Martian atmosphere contains water ice clouds similar to Earth's cirrus clouds. These clouds influence the atmospheric temperature profile, alter the balance of incoming and outgoing radiation, and vertically redistribute water and mineral dust. Extrapolations of classical heterogeneous nucleation theory from Earth-like conditions to colder temperature and lower pressure regimes present in extraterrestrial atmospheres may be inaccurate, and thus hydrological models describing these regimes could lack physical meaning. In this project, we use an electrodynamic balance (EDB) to levitate individual aerosol particles and study their freezing properties. We test previously characterized aerosols such as Arizona Test Dust (ATD) and sodium chloride (NaCl). Then, we examine the less well-studied Mojave Mars Simulant (MMS) dust, which mimics the composition and size of dust particles found in the Martian atmosphere. A relative humidity, temperature, and inert atmosphere are utilized to emulate conditions found in the Martian atmosphere. We will discuss the supersaturations under which heterogeneous ice nucleation occurs on surrogate Martian ice nuclei at various temperatures.

  12. Quantifying the mass loss of peripheral Greenland glaciers and ice caps (1958-2014).

    NASA Astrophysics Data System (ADS)

    Noël, Brice; van de Berg, Willem Jan; Machguth, Horst; van den Broeke, Michiel

    2016-04-01

    Since the 2000s, mass loss from Greenland peripheral glaciers and ice 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 ice discharge. However, despite multiple observation campaigns, little remains known about the contribution of GICs to total Greenland mass 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 mass balance (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 ice 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 mass loss. These data are considered valuable for model evaluation and prediction of future sea level rise.

  13. Glacial changes and glacier mass balance at Gran Campo Nevado, Chile during recent decades

    NASA Astrophysics Data System (ADS)

    Schneider, C.; Schnirch, M.; Kilian, R.; Acuña, C.; Casassa, G.

    2003-04-01

    Within the framework of the program Global Land Ice 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 ice cap of the Gran Campo Nevado (GCN), including several outlet glaciers plus some minor glaciers and firn fields. All together the ice covered areas sum up to 260 km2. GCN forms the only major ice 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 Ice Cap. From the computed energy balance, 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

  14. Transient bright "halos" on the South Polar Residual Cap of Mars: Implications for mass-balance

    NASA Astrophysics Data System (ADS)

    Becerra, Patricio; Byrne, Shane; Brown, Adrian J.

    2015-05-01

    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 ice 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 ice 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 ice 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 mass-balance for flat portions of the SPRC in those years. A net accumulation mass-balance 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.

  15. Origin of howardites, diogenites and eucrites - A mass balance constraint

    NASA Technical Reports Server (NTRS)

    Warren, P. H.

    1985-01-01

    Two petrogenetic models for the noncumulate-basaltic parts of howardite meteorites are discussed. A mass balance constraint is developed which indicates that more than half of the basaltic components in howardites formed as residual liquids from fractional crystallization of melts that had earlier produced diogentelike pyroxene cumulate components. Other model constriants involving scandium trends, clustering near olivine-pyroxene-plagioclase peritectic, and MgO/(MgO + FeO) ratios are discussed.

  16. High-resolution modeling of coastal freshwater discharge and glacier mass balance in the Gulf of Alaska watershed

    NASA Astrophysics Data System (ADS)

    Beamer, J. P.; Hill, D. F.; Arendt, A.; Liston, G. E.

    2016-05-01

    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-balance snow/ice melt, soil water balance, 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 mass balance 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 balance 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 ice melt, and 20% rainfall. Glacier runoff, taken as the sum of rainfall, snow, and ice 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 mass balance alone, are actually measuring the full water budget of land and ice surfaces.

  17. Energy balance in a warm world without the ocean conveyor belt and sea ice

    NASA Astrophysics Data System (ADS)

    Hu, Aixue; Meehl, Gerald A.; Han, Weiqing; Lu, Jianhua; Strand, Warren G.

    2013-12-01

    a strong global warming scenario, the global mean temperature could rise up to 10°C, causing the global ocean conveyor belt to collapse and the summer sea ice to disappear. This will lead to profound changes in our climate system and to impact drastically the living conditions of the globe. Here we study how the global heat redistribution and regional heat balance will respond to these changes using the National Center for Atmospheric Research Community Climate System Model version 4. Results show that the collapsed ocean conveyor belt reduces the oceanic northward meridional heat transport (MHT) by nearly 60% with a minor increase in the atmospheric MHT. The polar amplified warming is primarily caused by the increased absorption of longwave radiation due to the increased greenhouse gases and cloudiness and by the increased absorption of shortwave radiation due to a lower albedo associated with the disappeared summer sea ice.

  18. Continuum-mechanical, Anisotropic Flow model for polar ice masses, based on an anisotropic Flow Enhancement factor

    NASA Astrophysics Data System (ADS)

    Placidi, Luca; Greve, Ralf; Seddik, Hakime; Faria, Sérgio H.

    2010-03-01

    A complete theoretical presentation of the Continuum-mechanical, Anisotropic Flow model, based on an anisotropic Flow Enhancement factor (CAFFE model) is given. The CAFFE model is an application of the theory of mixtures with continuous diversity for the case of large polar ice masses in which induced anisotropy occurs. The anisotropic response of the polycrystalline ice is described by a generalization of Glen’s flow law, based on a scalar anisotropic enhancement factor. The enhancement factor depends on the orientation mass density, which is closely related to the orientation distribution function and describes the distribution of grain orientations (fabric). Fabric evolution is governed by the orientation mass balance, which depends on four distinct effects, interpreted as local rigid body rotation, grain rotation, rotation recrystallization (polygonization) and grain boundary migration (migration recrystallization), respectively. It is proven that the flow law of the CAFFE model is truly anisotropic despite the collinearity between the stress deviator and stretching tensors.

  19. Modeling past and future mass balance and discharge of Gulkana Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Roth, A. C.; Hock, R. M.; Arendt, A. A.; Zhang, J.

    2010-12-01

    The trends of climate change indicate that glacier melt will continue to increase. It is imperative that we understand and quantify how this will affect freshwater river runoff and downstream hydrology in order to better inform local response, policy, and resource management. The purpose of this study was to calibrate a model of discharge and mass balance of Gulkana Glacier and predict the glacier’s response to climate change. Gulkana Glacier is a U.S. Geological Survey (USGS) benchmark glacier located on the south flank of the eastern Alaska Range with an area of 15 km2. Using a temperature-index model including potential clear-sky direct radiation, discharge and mass balance of Gulkana Glacier were simulated over the period of 1967-2009 with a daily time step and a 40 m resolution DEM. Input data for the model were daily temperatures and precipitation data obtained from the USGS climate station near the glacier. Model parameters including precipitation lapse rate, precipitation correction, snowfall correction, melt factor, radiation melt factor for ice, and radiation melt factor for snow, were calibrated until the best agreement between measured and simulated discharged and winter, summer, and annual mass balance data was obtained. Future climate data defined by three time slices (2010-2019, 2050-2059, and 2090-2099) were obtained by a hierarchical climate modeling system, in which the CCSM3 simulations were downscaled with the high resolution regional model Arctic MM5. The 21st century climate is based on the middle-of-the-road A1B scenario, which represents balanced fossil and non-fossil fuel use. The mean temperature difference between each time slice and the mean measured temperature for 2000-2009 was found. These values were added to the daily temperatures for 2000-2009 and the model was used to calculate future discharge and mass balance for each time slice. Precipitation input was the measured 2000-2009 data for each time slice. Compared to the 2000

  20. How much can Greenland melt? An upper bound on mass loss from the Greenland Ice Sheet through surface melting

    NASA Astrophysics Data System (ADS)

    Liu, X.; Bassis, J. N.

    2015-12-01

    With observations showing accelerated mass loss from the Greenland Ice Sheet due to surface melt, the Greenland Ice Sheet is becoming one of the most significant contributors to sea level rise. The contribution of the Greenland Ice 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 Ice Sheet both due to uncertainty in atmospheric forcing and the ice 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 balance 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 ice volume loss and related sea-level rise associated with surface melting. To estimate the upper bound, we assume the Greenland Ice Sheet is perpetually covered in thick clouds, which maximize longwave radiation to the ice sheet. We further assume that deposition of black carbon darkens the ice 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 ice sheet increases mass loss in the short term, refreezing of retained water warms the ice 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 Ice 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

  1. Stable isotope mass balance of lakes: a contemporary perspective (Invited)

    NASA Astrophysics Data System (ADS)

    Gibson, J. J.; Birks, S. J.; YI, Y.; Jasechko, S.

    2013-12-01

    Stable isotopes are widely used in paleoclimate studies of lakes to reconstruct water balance and/or climatic conditions, but there are a variety of assumptions that are often made to simplify and operationalize the isotope transfer functions. Based on recent studies conducted on a wide range of lakes across North America, as well as a comprehensive compilation of existing data from around the globe, we present contemporary examples of stable-isotope mass-balance studies based on site-specific to regional lake datasets. We illustrate the need in most cases to understand and characterize the local climate and hydrological setting to accurately model the observed isotopic enrichment, as well as the importance of amount-weighting liquid fluxes and evaporation-flux-weighting vapour fluxes. Potential complications due to atmospheric feedback are also explored by presenting a new analysis of the Laurentian Great Lakes where we apply a model that considers the timing of evaporation, which occurs mainly in the winter, and accounts for downwind lake effects, humidity and isotopic build-up in the boundary layer. One future opportunity of lake-based paleoclimate research may be to develop controlled studies that allow for specific atmospheric or water-balance processes to be targeted and reconstructed. We also show relationships between selected water quality indicators and isotope-based water balance indicators that should, in principle, be preserved in the lake sediment record.

  2. Selenium mass balance in the Great Salt Lake, Utah

    USGS Publications Warehouse

    Diaz, X.; Johnson, W.P.; Naftz, D.L.

    2009-01-01

    A mass balance for Se in the south arm of the Great Salt Lake was developed for September 2006 to August 2007 of monitoring for Se loads and removal flows. The combined removal flows (sedimentation and volatilization) totaled to a geometric mean value of 2079??kg Se/yr, with the estimated low value being 1255??kg Se/yr, and an estimated high value of 3143??kg Se/yr at the 68% confidence level. The total (particulates + dissolved) loads (via runoff) were about 1560??kg Se/yr, for which the error is expected to be ?? 15% for the measured loads. Comparison of volatilization to sedimentation flux demonstrates that volatilization rather than sedimentation is likely the major mechanism of selenium removal from the Great Salt Lake. The measured loss flows balance (within the range of uncertainties), and possibly surpass, the measured annual loads. Concentration histories were modeled using a simple mass balance, which indicated that no significant change in Se concentration was expected during the period of study. Surprisingly, the measured total Se concentration increased during the period of the study, indicating that the removal processes operate at their low estimated rates, and/or there are unmeasured selenium loads entering the lake. The selenium concentration trajectories were compared to those of other trace metals to assess the significance of selenium concentration trends. ?? 2008 Elsevier B.V.

  3. Temperature-index modeling of mass balance and runoff in the Valdez Glacier catchment in 2012 and 2013

    NASA Astrophysics Data System (ADS)

    Davis, Jennifer L.

    Glaciers play an important role in both storage and generation of runoff within individual watersheds. The Valdez Glacier catchment (342 km2), located in southern Alaska in the Chugach mountains off of Prince William Sound, is characterized by large annual volumes of rain- and snowfall. As Valdez Glacier and other glaciers within the catchment (comprising 58% of the catchment area) continue to melt in a warming climate, it is unclear how the runoff will be affected. Temperature-index modeling is one method used to estimate glacier mass balance and runoff in highly glacierized catchments, and may be suitable for predicting future runoff regimes. In this study, we used a combination of field measurements (air temperature, glacier mass balance, streamflow, and ground-penetrating radar (GPR)-derived snow water equivalent (SWE) from a parallel study) and modeled climate data (PRISM) to a) calibrate a temperature-index model to glacier mass balance in 2012; b) validate the model to laser altimetry; and c) calibrate a temperature-index model to runoff measurements in fall of 2012 and in spring, summer and fall of 2013. We calibrated the snow-radiation coefficient (rsnow), ice-radiation coefficient (rice), and melt factor (MF) of the temperature-index model to glacier mass balance measurements from 2012. Using the calibrated- rsnow, r ice, and MF (i.e. rsnow, rice, and MF = 0.20, 0.50 and 4.0, respectively), we calculated 2012 annual glacier mass balance (Ba) at 0.05 +/- 0.49 meters water equivalent (m w.eq.). We next validated the model to 2012 laser altimetry annual glacier mass balance estimates (Ba = 0.20 +/- 0.6 m w.eq.). We then modeled glacier mass balance in 2013 using rsnow, rice, and MF from the 2012 calibration. The model underestimated summer glacier mass balance in 2013, resulting in annual glacier mass balance (Ba = 0.55 m w.eq.) that did not fall within the 2013 laser altimetry annual balance estimate (Ba = -1.15 +0.29/-0.30 m w.eq.). We therefore re

  4. Mass and energy balance of the cold Io torus

    NASA Technical Reports Server (NTRS)

    Moreno, M. A.; Barbosa, D. D.

    1986-01-01

    A new model of the cold Io torus is described. Ions and energy are injected into the system by independent processes so that the mass balance is isolated from the energy balance. The primary source of energy is local ionization and acceleration of hot pickup ions resulting from charge exchange between thermal ions and an extended cloud of Iogenic sulfur and oxygen atoms. The primary energy loss mechanism of the plasma is collisionally excited line emission at optical wavelengths. The primary ion source is radial diffusion inward from the hot torus on a time scale of 140-710 days. The primary ion loss mechanism is a novel two-step enhanced recombination mechanism involving charge exchange between thermal ions and an extended cloud of neutral SO2 molecules, followed by rapid dissociative recombination of the resultant molecular ion. The model provides a self-consistent solution which reconciles a number of diverse observations with known physical processes.

  5. A relationship between ion balance and the chemical compounds of salt inclusions found in the Greenland Ice Core Project and Dome Fuji ice cores

    NASA Astrophysics Data System (ADS)

    Iizuka, Yoshinori; Horikawa, Shinichiro; Sakurai, Toshimitsu; Johnson, Sigfus; Dahl-Jensen, Dorthe; Steffensen, JøRgen Peder; Hondoh, Takeo

    2008-04-01

    We have proposed a method of deducing the chemical compounds found in deep polar ice cores by analyzing the balance between six major ions (Cl-, NO3-, SO42-, Na+, Mg2+, and Ca2+). The method is demonstrated for the Holocene and last glacial maximum regions of the Dome Fuji and GRIP ice cores. The dominant compounds depend only on the ion balance and the sequence of chemical reactions. In priority order, the principle salts are calcium sulfate, other sulfates, nitrate, chloride, and carbonate. The chemical abundances deduced by this method agree well with the results of Raman spectroscopy on individual salt inclusions. The abundances in the ice cores are shown to reflect differences in climatic periods (the acidic environment of the Holocene versus the reductive environment of the last glacial maximum) and regional conditions (the marine environment of Antarctica versus the continental environment of Greenland).

  6. Surface energy balance measurements and modeling on the ice cap of King George Island, West Antarctica

    NASA Astrophysics Data System (ADS)

    Falk, U.; Braun, M.; Sala, H.; Menz, G.

    2012-04-01

    The Antarctic Peninsula is amongst the fastest warming places on Earth and further temperature increase is to be expected. It has undergone rapid environmental changes in the past decades. Exceptional rates of surface air temperature increases (2.5K in 50 years) are concurrent with retreating glacier fronts, an increase in melt areas, surface lowering and rapid retreat, break-up and disintegration of ice shelves. The South Shetland Islands are located on the northern tip of the Peninsula and are especially vulnerable to climate change due to their maritime climate. For King George Island we have compiled a unique data set comprising direct measurements of evaporation and sensible heat flux by eddy covariance on the Warszawa Icefield for the austral summers November 2010 to March 2011 and January to February 2012 in combination with a fully equipped automated weather station measuring long- and short-wave radiation components, profiles of temperature, humidity and wind velocities as well as glacier ice temperatures in profile. The combination with the eddy covariance data allows for analysis of variability and seasonality of surface energy balance components on a glacier for an entire year. Repeat measurements of surface lowering at different locations on King George Island are used for analysis of multi-sensor satellite data to identify melt patterns and bare ice areas during summer. In combination with long-term time series of weather data, these data give indication of the sensitivity of the inland ice cap to the ongoing changes. This research is part of the ESF project IMCOAST funded by BMBF. Field work was carried out at the Dallmann laboratory (Jubany, King George Island) in cooperation of the Instituto Antartico Argentino (Argentina) and the Alfred-Wegener Institute (German).

  7. Detailed comparison of the geodetic and direct glaciological mass balances on an annual time scale at Hintereisferner, Austria

    NASA Astrophysics Data System (ADS)

    Klug, Christoph; Bollmann, Erik; Galos, Stephan; Kaser, Georg; Prinz, Rainer; Rieg, Lorenzo; Sailer, Rudolf

    2016-04-01

    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 ice and firn zones. The resulting grids with according conversion factors (900 and 700 kg/m³ for ice and firn, respectively) are combined to calculate mass changes. In a last step, the survey dates are adjusted, using numerous field observations. On an annual time scale, the geodetic mass balances 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 mass balances. Regarding the cumulative mass balance, 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 mass balances. 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

  8. The mass balance of earthquakes and earthquake sequences

    NASA Astrophysics Data System (ADS)

    Marc, O.; Hovius, N.; Meunier, P.

    2016-04-01

    Large, compressional earthquakes cause surface uplift as well as widespread mass wasting. Knowledge of their trade-off is fragmentary. Combining a seismologically consistent model of earthquake-triggered landsliding and an analytical solution of coseismic surface displacement, we assess how the mass balance of single earthquakes and earthquake sequences depends on fault size and other geophysical parameters. We find that intermediate size earthquakes (Mw 6-7.3) may cause more erosion than uplift, controlled primarily by seismic source depth and landscape steepness, and less so by fault dip and rake. Such earthquakes can limit topographic growth, but our model indicates that both smaller and larger earthquakes (Mw < 6, Mw > 7.3) systematically cause mountain building. Earthquake sequences with a Gutenberg-Richter distribution have a greater tendency to lead to predominant erosion, than repeating earthquakes of the same magnitude, unless a fault can produce earthquakes with Mw > 8 or more.

  9. Can Volcanic Eruptions Produce Ice Ages or Mass Extinctions?

    NASA Astrophysics Data System (ADS)

    Robock, A.; Ammann, C.; Oman, L.; Shindell, D.; Stenchikov, G.

    2006-12-01

    Volcanic eruptions are well known to be important causes of interannual and even interdecadal climate change. But can very large eruptions initiate ice ages, as has been suggested for the Toba eruption ~74,000 years ago? Could flood basalt eruptions, such as the Deccan Traps 65,000,000 years ago or the Siberian Traps 250,000,000 years ago, have produced climate change large enough and long-lasting enough, along with other atmospheric pollution, to have caused mass extinctions? Here we conduct climate model simulations of the effects of a volcanic eruption 100 times larger than the 1991 Pinatubo eruption as a test of the climatic effects of Toba. We use two different state-of-the-art climate models, CCSM 3.0 from the National Center for Atmospheric Research and ModelE from the NASA Goddard Institute for Space Studies, to investigate the dependence of the results on the climate model used. We find that although the "Toba" eruption produces very large global cooling for a couple years, of up to 10°C, the volcanic aerosols leave the atmosphere quickly and the climate largely recovers in a decade. We investigated the mechanism of vegetation response to the cold and dark, but this mechanism was not strong enough to prolong the response enough to allow ice sheets to grow. On the other hand, continuous emissions from massive flood basalt eruptions lasting several decades could make it so cold and dark at the Earth's surface that many species would find it hard to survive. On longer time scales, however, continued large greenhouse gas emissions would have a significant warming effect. With good estimates of the amount and timing of gas and particle emissions into the atmosphere, we have the climate modeling tools to calculate their impact on climate.

  10. Modeling of Firn Compaction for Estimating Ice-Sheet Mass Change from Observed Ice-Sheet Elevation Change

    NASA Technical Reports Server (NTRS)

    Li, Jun; Zwally, H. Jay

    2011-01-01

    Changes in ice-sheet surface elevation are caused by a combination of ice-dynamic imbalance, ablation, temporal variations in accumulation rate, firn compaction and underlying bedrock motion. Thus, deriving the rate of ice-sheet mass change from measured surface elevation change requires information on the rate of firn compaction and bedrock motion, which do not involve changes in mass, 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 ice sheet in order to separate the accumulation-driven changes from the ice-dynamic/ablation-driven changes, and thus to derive the corresponding mass 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 mass change is not valid where the accumulation and the dynamic elevation changes are of opposite sign.

  11. Estimating nutrient loadings using chemical mass balance approach.

    PubMed

    Jain, C K; Singhal, D C; Sharma, M K

    2007-11-01

    The river Hindon is one of the important tributaries of river Yamuna in western Uttar Pradesh (India) and carries pollution loads from various municipal and industrial units and surrounding agricultural areas. The main sources of pollution in the river include municipal wastes from Saharanpur, Muzaffarnagar and Ghaziabad urban areas and industrial effluents of sugar, pulp and paper, distilleries and other miscellaneous industries through tributaries as well as direct inputs. In this paper, chemical mass balance approach has been used to assess the contribution from non-point sources of pollution to the river. The river system has been divided into three stretches depending on the land use pattern. The contribution of point sources in the upper and lower stretches are 95 and 81% respectively of the total flow of the river while there is no point source input in the middle stretch. Mass balance calculations indicate that contribution of nitrate and phosphate from non-point sources amounts to 15.5 and 6.9% in the upper stretch and 13.1 and 16.6% in the lower stretch respectively. Observed differences in the load along the river may be attributed to uncharacterized sources of pollution due to agricultural activities, remobilization from or entrainment of contaminated bottom sediments, ground water contribution or a combination of these sources. PMID:17616829

  12. Mass balance assessment for mercury in Lake Champlain

    USGS Publications Warehouse

    Gao, N.; Armatas, N.G.; Shanley, J.B.; Kamman, N.C.; Miller, E.K.; Keeler, G.J.; Scherbatskoy, T.; Holsen, T.M.; Young, T.; McIlroy, L.; Drake, S.; Olsen, Bill; Cady, C.

    2006-01-01

    A mass balance model for mercury in Lake Champlain was developed in an effort to understand the sources, inventories, concentrations, and effects of mercury (Hg) contamination in the lake ecosystem. To construct the mass balance model, air, water, and sediment were sampled as a part of this project and other research/monitoring projects in the Lake Champlain Basin. This project produced a STELLA-based computer model and quantitative apportionments of the principal input and output pathways of Hg for each of 13 segments in the lake. The model Hg concentrations in the lake were consistent with measured concentrations. Specifically, the modeling identified surface water inflows as the largest direct contributor of Hg into the lake. Direct wet deposition to the lake was the second largest source of Hg followed by direct dry deposition. Volatilization and sedimentation losses were identified as the two major removal mechanisms. This study significantly improves previous estimates of the relative importance of Hg input pathways and of wet and dry deposition fluxes of Hg into Lake Champlain. It also provides new estimates of volatilization fluxes across different lake segments and sedimentation loss in the lake. ?? 2006 American Chemical Society.

  13. Prescribing hemodialysis using a weekly urea mass balance model.

    PubMed

    Leypoldt, J K; Kablitz, C; Gregory, M C; Senekjian, H O; Cheung, A K

    1991-01-01

    Prescribing hemodialysis by monitoring only predialysis BUN concentrations is not sufficient to guarantee adequate therapy. Results from the National Cooperative Dialysis Study have suggested that hemodialysis therapy is adequate if the protein catabolic rate is maintained greater than 1 g/day/kg body weight and simultaneously if sufficient hemodialysis is prescribed to maintain either a time-averaged BUN concentration (TACurea) less than 50 mg/dl or a value of Kt/V greater than unity. In the present study mathematical relationships were derived from a weekly urea mass balance model that permit an evaluation of TACurea and of protein catabolism via the urea generation rate (G) without the need for conventional urea kinetic modeling. The parameters TACurea and G were simply calculated from a midweek predialysis BUN concentration (BUNMW) by: TACurea = 0.7 BUNMW G = 0.7 BUNMW(Kr + Kd tau/T) where Kr, Kd, tau and T denote residual renal urea clearance, dialyzer urea clearance, number of minutes of hemodialysis per week, and number of minutes total in a week, respectively. Clinical results from 139 modeling sessions on 91 patients demonstrated that TACurea and G derived from urea kinetic modeling correlated highly with those calculated from the above equations (r = 0.96 and 0.94, respectively). It is concluded that individualized hemodialysis prescription and adequacy of therapy can be assessed by monitoring TACurea and G by calculation from a weekly urea mass balance model. PMID:1819316

  14. Deducing high-altitude precipitation from glacier mass balance measurements

    NASA Astrophysics Data System (ADS)

    Giesen, Rianne H.; Immerzeel, Walter W.; Wanders, Niko

    2016-04-01

    The spatial distribution of precipitation in mountainous terrain is generally not well known due to underrepresentation of gauge observations at higher elevations. Precipitation tends to increase with elevation, but since observations are mainly performed in the valleys, the vertical precipitation gradient cannot be deduced from these measurements. Furthermore, the spatial resolution of gridded meteorological data is often too coarse to resolve individual mountain chains. Still, a reliable estimate of high-elevation precipitation is required for many hydrological applications. We present a method to determine the vertical precipitation gradient in mountainous terrain, making use of glacier mass balance observations. These measurements have the advantage that they provide a basin-wide precipitation estimate at high elevations. The precipitation gradient is adjusted until the solid precipitation over the glacier area combined with the calculated melt gives the measured annual glacier mass balance. Results for the glacierized regions in Central Europe and Scandinavia reveal spatially coherent patterns, with predominantly positive precipitation gradients ranging from -4 to +28 % (100 m)‑1. In some regions, precipitation amounts at high elevations are up to four times as large as in the valleys. A comparison of the modelled winter precipitation with observed snow accumulation on glaciers shows a good agreement. Precipitation measured at the few high-altitude meteorological stations is generally lower than our estimate, which may result from precipitation undercatch. Our findings will improve the precipitation forcing for glacier modelling and hydrological studies in mountainous terrain.

  15. Mass balance of dioxins over a cement kiln in China.

    PubMed

    Li, Yeqing; Chen, Tong; Zhang, Jiang; Meng, Weijie; Yan, Mi; Wang, Huanzhong; Li, Xiaodong

    2015-02-01

    The cement production process may be a potential source of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, "dioxins"), due to the widespread distribution of dioxins and potential precursors in raw materials and to conditions favorable to de novo formation in the heat exchangers. The emission, gas/particle distribution, and mass balance of PCDD/Fs were investigated at a typical state-of-the-art Chinese cement kiln. Input and output inventories were established for three campaigns, including two in normal operation and one while co-processing refuse derived fuel (RDF). Sample analysis from stack gas, cement kiln dust, raw meal, fly dust and clinker for the analysis of PCDD/Fs were reported in this study. Dioxins were also analyzed at various positions in the pre-heater, presenting an adsorption-desorption circulation process of PCDD/Fs. The over-all dioxin mass balance was negative, indicating that this cement kiln is not a source but a sink process of dioxins. PMID:25532674

  16. Mass Balance of Perfluoroalkyl Acids in the Baltic Sea

    PubMed Central

    2013-01-01

    A mass balance was assembled for perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorodecanoic acid (PFDA), and perfluorooctanesulfonic acid (PFOS) in the Baltic Sea. Inputs (from riverine discharge, atmospheric deposition, coastal wastewater discharges, and the North Sea) and outputs (to sediment burial, transformation of the chemical, and the North Sea), as well as the inventory in the Baltic Sea, were estimated from recently published monitoring data. Formation of the chemicals in the water column from precursors was not considered. River inflow and atmospheric deposition were the dominant inputs, while wastewater treatment plant (WWTP) effluents made a minor contribution (<5%). A mass balance of the Oder River watershed was assembled to explore the sources of the perfluoroalkyl acids (PFAAs) in the river inflow. It indicated that WWTP effluents made only a moderate contribution to riverine discharge (21% for PFOA, 6% for PFOS), while atmospheric deposition to the watershed was 1–2 orders of magnitude greater than WWTP discharges. The input to the Baltic Sea exceeded the output for all four PFAAs, suggesting that inputs were higher during 2005–2010 than during the previous 20 years despite efforts to reduce emissions of PFAAs. One possible explanation is the retention and delayed release of PFAAs from atmospheric deposition in the soils and groundwater of the watershed. PMID:23528236

  17. Atmospheric methyl bromide: Trends and global mass balance

    SciTech Connect

    Khalil, M.A.K.; Rasmussen, R.A.; Gunawardena, R. )

    1993-02-20

    Atmospheric methyl bromide is of considerable environmental importance as the largest reservoir of gaseous bromine in the atmosphere. Bromine gases can catalytically destroy stratospheric ozone. Since agricultural activities, automobiles, biomass burning, and other human activities produce CH[sub 3]Br, it is of interest to know its global mass balance and particularly the specific sources and sinks. In this paper the authors provide a decadal time series of global CH[sub 3]Br concentrations in the Earth's atmosphere. The data show that average concentrations are about 10 pptv and during the last 4 years may be increasing at 0.3 [plus minus] 0.1 pptv/yr (3%/yr [plus minus] 1%/yr). They estimate that the atmospheric lifetime of CH[sub 3]Br that is due to reaction with OH, is about 2 years, resulting in a calculated global emission rate of about 100 Gy/yr. Ocean supersaturations of 140-180% are observed, and atmospheric concentrations over the open oceans are higher than at comparably located coastal sites. The ocean source is estimated to be about 35 Gg/yr. The remaining emissions must come from other natural sources and anthropogenic activities. The results are based on some 2,200 samples obtained over more than a decade. Mass balance calculations explain most aspects of the present data but other implications are not easily reconciled, leaving open the possibility of undiscovered sources and sinks. 20 refs., 5 figs., 4 tabs.

  18. Has Natural Variability Masked the Expected Increase in Antarctic Surface Mass Balance with Global Warming?

    NASA Astrophysics Data System (ADS)

    Previdi, Michael; Polvani, Lorenzo M.

    2016-04-01

    One of the expected and rather paradoxical consequences of anthropogenic global warming is an increase in Antarctic surface mass balance (or net snow accumulation), as robustly simulated by both global and regional climate models. This surface mass balance (SMB) increase occurs because the higher moisture content of a warmer atmosphere leads to increases in precipitation, with this precipitation falling in the form of snow over Antarctica. Despite these robust model projections, however, observations indicate that there has been no significant change in Antarctic SMB during the past several decades. Here, we show that this apparent discrepancy between models and observations can be explained by the fact that the anthropogenic climate change signal is still relatively small compared to the noise associated with natural climate variability. Using an ensemble of 35 global coupled climate models to separate signal and noise, we find that the forced SMB increase due to global warming in recent decades is unlikely to be detectable in a statistical sense as a result of large natural SMB variability on interannual-to-multidecadal timescales. However, our analysis reveals that if the world continues to follow the present trajectory of greenhouse gas emissions, the anthropogenic impact on Antarctic SMB will emerge from natural variability by the middle of the current century. With this, SMB increases over Antarctica will begin to mitigate global sea-level rise, partially offsetting the effects of dynamic ice loss.

  19. Assessment Of Errors In Long-Term Mass Balance Records From Alaska, USA

    NASA Astrophysics Data System (ADS)

    March, R. S.; van Beusekom, A. E.; O'Neel, S.

    2009-12-01

    The USGS maintains a long-term glacier mass balance monitoring program at Gulkana and Wolverine glaciers in Alaska. The records produced by this program are a major component of the world’s mountain glacier balance inventory due to the scarcity of such long-term measurements. Recent data that show rapid glacier volume loss in Alaska further emphasize the importance of these records. An integral part of the long-term mass balance program is repeated assessment of the validity of the methods because bias errors in mass balance data are cumulative. Long-term glacier mass balance records in Alaska have previously been shown to be in good agreement with geodetically determined volume changes despite a minimal network of mass balance stakes. Because the rates of negative mass balance and change in glacier geometry have recently increased, this work reassess whether or not the existing stake networks and method of determining glacier-average balance are still working adequately.

  20. Combined Ice and Water Balances of Gulkana and Wolverine Glaciers, Alaska, and South Cascade Glacier, Washington, 1965 and 1966 Hydrologic Years

    USGS Publications Warehouse

    Meier, Mark Frederick; Tangborn, Wendell V.; Mayo, Lawrence R.; Post, Austin

    1971-01-01

    Glaciers occur in northwestern North America between lat 37 deg and 69 deg N. in two major mountain systems. The Pacific Mountain System, near the west coast, receives large amounts of precipitation, has very mild temperatures, and contains perhaps 90 percent of the glacier ice. The Rocky Mountain or Eastern System, on the other hand, receives nearly an order of magnitude less precipitation, has temperatures that range from subpolar to subtropic, and contains glaciers that are much smaller in both size and total area. As a contribution to the International Hydrological Decade program on combined balances at selected glaciers, the U.S. Geological Survey is conducting studies of ice and water balance on four glaciers in the Pacific Mountain System: Wolverine and Gulkana Glaciers in Alaska, South Cascade Glacier in Washington, and Maclure Glacier in California. Similar data are being collected by other organizations at five glaciers in western Canada, including two in the Rocky Mountain System, and at one glacier in the Rocky Mountain System in northern Alaska. Gulkana, Wolverine, South Cascade, and Maclure Glaciers have dissimilar mass balances, and each is fairly representative of the glaciers for its particular region. Gulkana Glacier (lat 63 deg 15' N., Alaska Range, Alaska) normally has an equilibrium line at an altitude of 1,800 m (meters), an activity index of about 6 mm/m (millimeters per meter), a winter balance of about 1.0 m, and an annual exchange of about 2.2 m. (Balance values are given in terms of water-equivalent measure; the winter balance of 1 m, for example, indicates a volume of ice equal in mass to a volume of water 1 m in depth covering the area of the glacier.) The normal approximate parameters for the other glaciers studied are as follows: Wolverine Glacier (lat 60 deg 24' N., Kenai Mountains, Alaska) - equilibrium-line altitude 1,200 m, activity index 9 mm/m, winter balance 2.5 m, and annual exchange 5.5 m; South Cascade Glacier (lat 48 deg 22

  1. Rising river flows and glacial mass balance in central Karakoram

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Biswajit; Khan, Asif

    2014-05-01

    glacial mass balance in central Karakoram is nearly neutral. The rising river flows accompanying non-negative glacier mass balance are consistent with predicted future river flows derived from hydrologic modeling coupled with a climate projection suggesting increasing temperature and precipitation with unchanged glacier covers. This investigation reconciles two apparently contradictory observations namely rising river flows and either zero or slightly positive mass balance of central Karakoram glaciers.

  2. Mass balance model parameter transferability on a tropical glacier

    NASA Astrophysics Data System (ADS)

    Gurgiser, Wolfgang; Mölg, Thomas; Nicholson, Lindsey; Kaser, Georg

    2013-04-01

    The mass balance and melt water production of glaciers is of particular interest in the Peruvian Andes where glacier melt water has markedly increased water supply during the pronounced dry seasons in recent decades. However, the melt water contribution from glaciers is projected to decrease with appreciable negative impacts on the local society within the coming decades. Understanding mass balance processes on tropical glaciers is a prerequisite for modeling present and future glacier runoff. As a first step towards this aim we applied a process-based surface mass balance model in order to calculate observed ablation at two stakes in the ablation zone of Shallap Glacier (4800 m a.s.l., 9°S) in the Cordillera Blanca, Peru. Under the tropical climate, the snow line migrates very frequently across most of the ablation zone all year round causing large temporal and spatial variations of glacier surface conditions and related ablation. Consequently, pronounced differences between the two chosen stakes and the two years were observed. Hourly records of temperature, humidity, wind speed, short wave incoming radiation, and precipitation are available from an automatic weather station (AWS) on the moraine near the glacier for the hydrological years 2006/07 and 2007/08 while stake readings are available at intervals of between 14 to 64 days. To optimize model parameters, we used 1000 model simulations in which the most sensitive model parameters were varied randomly within their physically meaningful ranges. The modeled surface height change was evaluated against the two stake locations in the lower ablation zone (SH11, 4760m) and in the upper ablation zone (SH22, 4816m), respectively. The optimal parameter set for each point achieved good model skill but if we transfer the best parameter combination from one stake site to the other stake site model errors increases significantly. The same happens if we optimize the model parameters for each year individually and transfer

  3. Enforcing elemental mass and energy balances for reduced order models

    SciTech Connect

    Ma, J.; Agarwal, K.; Sharma, P.; Lang, Y.; Zitney, S.; Gorton, I.; Agawal, D.; Miller, D.

    2012-01-01

    Development of economically feasible gasification and carbon capture, utilization and storage (CCUS) technologies requires a variety of software tools to optimize the designs of not only the key devices involved (e., g., gasifier, CO{sub 2} adsorber) but also the entire power generation system. High-fidelity models such as Computational Fluid Dynamics (CFD) models are capable of accurately simulating the detailed flow dynamics, heat transfer, and chemistry inside the key devices. However, the integration of CFD models within steady-state process simulators, and subsequent optimization of the integrated system, still presents significant challenges due to the scale differences in both time and length, as well the high computational cost. A reduced order model (ROM) generated from a high-fidelity model can serve as a bridge between the models of different scales. While high-fidelity models are built upon the principles of mass, momentum, and energy conservations, ROMs are usually developed based on regression-type equations and hence their predictions may violate the mass and energy conservation laws. A high-fidelity model may also have the mass and energy balance problem if it is not tightly converged. Conservations of mass and energy are important when a ROM is integrated to a flowsheet for the process simulation of the entire chemical or power generation system, especially when recycle streams are connected to the modeled device. As a part of the Carbon Capture Simulation Initiative (CCSI) project supported by the U.S. Department of Energy, we developed a software framework for generating ROMs from CFD simulations and integrating them with Process Modeling Environments (PMEs) for system-wide optimization. This paper presents a method to correct the results of a high-fidelity model or a ROM such that the elemental mass and energy are conserved perfectly. Correction factors for the flow rates of individual species in the product streams are solved using a

  4. Infrared Observations of Hot Gas and Cold Ice Toward the Low Mass Protostar Elias 29

    NASA Technical Reports Server (NTRS)

    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.

    2000-01-01

    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 ice and the interrelationship of interstellar ice and hot core gases around low mass protostars. We see abundant hot CO and H2O gas, as well as the absorption bands of CO, CO2, H2O and "6.85 micrometer" ices. We compare the abundances and physical conditions of the gas and ices toward Elias 29 with the conditions around several well studied luminous, high mass protostars. The high gas temperature and gas/solid ratios resemble those of relatively evolved high mass objects (e.g. GL 2591). However, none of the ice 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 mass object Elias 29 is qualitatively different from that of high mass protostars. This is possibly related to a different density gradient of the envelope or shielding of the ices in a circumstellar disk. This result is important for our understanding of the evolution of interstellar ices, and their relation to cometary ices.

  5. Balancing mass and momentum in the Local Group

    NASA Astrophysics Data System (ADS)

    Diaz, J. D.; Koposov, S. E.; Irwin, M.; Belokurov, V.; Evans, N. W.

    2014-09-01

    In the rest frame of the Local Group (LG), the total momentum of the Milky Way (MW) and Andromeda (M31) should balance to zero. We use this fact to constrain new solutions for the solar motion with respect to the LG centre of mass, the total mass of the LG, and the individual masses of M31 and the MW. Using the set of remote LG galaxies at >350 kpc from the MW and M31, we find that the solar motion has amplitude V⊙ = 299 ± 15 km s-1 in a direction pointing towards galactic longitude l⊙ = 98.4° ± 3.6° and galactic latitude b⊙ = -5.9° ± 3.0°. The velocities of M31 and the MW in this rest frame give a direct measurement of their mass ratio, for which we find log10(MM31/MMW) = 0.36 ± 0.29. We combine these measurements with the virial theorem to estimate the total mass within the LG as MLG = (2.5 ± 0.4) × 1012 M⊙. Our value for MLG is consistent with the sum of literature values for MMW and MM31. This suggests that the mass of the LG is almost entirely located within the two largest galaxies rather than being dispersed on larger scales or in a background medium. The outskirts of the LG are seemingly rather empty. Combining our measurement for MLG and the mass ratio, we estimate the individual masses of the MW and M31 to be MMW = (0.8 ± 0.5) × 1012 M⊙ and MM31 = (1.7 ± 0.3) × 1012 M⊙, respectively. Our analysis favours M31 being more massive than the MW by a factor of ˜2.3, and the uncertainties allow only a small probability (9.8 per cent) that the MW is more massive. This is consistent with other properties such as the maximum rotational velocities, total stellar content, and numbers of globular clusters and dwarf satellites, which all suggest that MM31/MMW > 1.

  6. Constraining the recent mass balance of Pine Island and Thwaites glaciers, West Antarctica with airborne observations of snow accumulation (Invited)

    NASA Astrophysics Data System (ADS)

    Medley, B.; Joughin, I. R.; Smith, B. E.; Das, S. B.; Steig, E. J.; Conway, H.; Gogineni, P. S.; Criscitiello, A. S.; McConnell, J. R.; van den Broeke, M. R.; Lenaerts, J.; Bromwich, D. H.; Nicolas, J. P.

    2013-12-01

    One of the largest sources of uncertainty in quantifying ice-sheet mass balance originates from our lack of understanding of spatiotemporal snow accumulation rates. Traditional in situ measurements of the accumulation rate (i.e., firn cores, snow pits, and stake farms) do not adequately capture the complex spatial variations in regional accumulation and are not suitable for regional mass balance studies. Accumulation measurements using ground-based radar systems capture the spatial variability in accumulation over discrete (i.e., annual to multi-decadal) and consistent time intervals along hundreds of kilometers of survey paths but cannot access certain areas of the ice sheet (e.g., highly crevassed regions). On the other hand, spatiotemporally complete global and regional atmospheric models of the accumulation rate are increasingly being used in place of measurements, but few regional measurements exist to rigorously test the temporal skill of these models. Here, we use data from two airborne radar systems, developed by the Center for Remote Sensing of Ice Sheets, to calculate recent accumulation rates over the Pine Island and Thwaites drainage systems along the Amundsen Coast of West Antarctica. These measurements are then used to: (1) assess the skill of global and regional atmospheric models and (2) precisely determine basin-wide accumulation rates for mass balance estimates. The spatial coverage limitation that makes field measurements disadvantageous for regional mass balance studies is overcome by aerial survey designed for maximum spatial coverage of these drainage basins. We measure the snow accumulation rate using the ultra-wideband airborne radar data to track near-surface internal horizons. The horizon thickness is converted to a water-equivalent thickness using a regionally representative density profile. Accumulation rates are calculated by dividing the water-equivalent thickness by the horizon age, which is determined either by annual count or using

  7. OXALATE MASS BALANCE DURING CHEMICAL CLEANING IN TANK 6F

    SciTech Connect

    Poirier, M.; Fink, S.

    2011-07-22

    The Savannah River Remediation (SRR) is preparing Tank 6F for closure. The first step in preparing the tank for closure is mechanical sludge removal. Following mechanical sludge removal, SRS performed chemical cleaning with oxalic acid to remove the sludge heel. Personnel are currently assessing the effectiveness of the chemical cleaning to determine whether the tank is ready for closure. SRR personnel collected liquid samples during chemical cleaning and submitted them to Savannah River National Laboratory (SRNL) for analysis. Following chemical cleaning, they collected a solid sample (also known as 'process sample') and submitted it to SRNL for analysis. The authors analyzed these samples to assess the effectiveness of the chemical cleaning process. Analysis of the anions showed the measured oxalate removed from Tank 6F to be approximately 50% of the amount added in the oxalic acid. To close the oxalate mass balance, the author collected solid samples, leached them with nitric acid, and measured the concentration of cations and anions in the leachate. Some conclusions from this work are: (1) Approximately 65% of the oxalate added as oxalic acid was removed with the decanted liquid. (2) Approximately 1% of the oxalate (added to the tank as oxalic acid) formed precipitates with compounds such as nickel, manganese, sodium, and iron (II), and was dissolved with nitric acid. (3) As much as 30% of the oxalate may have decomposed forming carbon dioxide. The balance does not fully account for all the oxalate added. The offset represents the combined uncertainty in the analyses and sampling.

  8. Melting standardized aluminum scrap: A mass balance model for europe

    NASA Astrophysics Data System (ADS)

    Boin, U. M. J.; Bertram, M.

    2005-08-01

    Although individual aluminum recycling companies have good knowledge of scrap in terms of its characteristic metal yield during melting, an overall view of this industry is still missing. An aluminum mass balance for the aluminum recycling industry in the European Union member states from 1995 to 2004 (EU-15) has been carried out. The objective was to increase the transparency of the complex recycling system and to determine how resource-conservative the industry is when melting aluminum scrap. Results show that in 2002, about 7 million tonnes of purchased, tolled, and internal scrap—with a metal content of 94%—were recycled in the EU-15. By comparing the net metal input to the final product, the study finds a very respectable metal recovery rate of 98%.

  9. Maintaining Atmospheric Mass and Water Balance Within Reanalysis

    NASA Technical Reports Server (NTRS)

    Takacs, Lawrence L.; Suarez, Max; Todling, Ricardo

    2015-01-01

    This report describes the modifications implemented into the Goddard Earth Observing System Version-5 (GEOS-5) Atmospheric Data Assimilation System (ADAS) to maintain global conservation of dry atmospheric mass as well as to preserve the model balance of globally integrated precipitation and surface evaporation during reanalysis. Section 1 begins with a review of these global quantities from four current reanalysis efforts. Section 2 introduces the modifications necessary to preserve these constraints within the atmospheric general circulation model (AGCM), the Gridpoint Statistical Interpolation (GSI) analysis procedure, and the Incremental Analysis Update (IAU) algorithm. Section 3 presents experiments quantifying the impact of the new procedure. Section 4 shows preliminary results from its use within the GMAO MERRA-2 Reanalysis project. Section 5 concludes with a summary.

  10. Mass-balance model for predicting nitrate in ground water

    USGS Publications Warehouse

    Frimpter, Michael H.; Donohue, John J.; Rapacz, Michael V.

    1990-01-01

    A mass-balance accounting model can be used to guide the management of septic systems and fertilizers to control the degradation of ground-water quality in zones of an aquifer that contribute water to public-supply wells. The nitrate concentration of the mixture in the well can be predicted for steady-state conditions by calculating the concentration that results from the total weight of nitrogen and total volume of water entering the zone of contribution to the well. These calculations will allow water-quality managers to predict the nitrate concentrations that would be produced by different types and levels of development, and to plan development accordingly. Computations for different development schemes provide a technical basis for planners and managers to compare water-quality effects and to select alternatives that limit nitrate concentration in wells.

  11. Resolving Trends in Antarctic Ice Sheet Mass Loss and Glacio-isostatic Adjustment Through Spatio-temporal Source-separation

    NASA Astrophysics Data System (ADS)

    Bamber, J. L.; Schoen, N.; Zammit-Mangion, A.; Rougier, J.; Flament, T.; Luthcke, S. B.; Petrie, E. J.; Rémy, F.

    2013-12-01

    There remains considerable inconsistency between different methods and approaches for determining ice mass trends for Antarctica from satellite observations. There are three approaches that can provide near global coverage for mass trends: altimetry, gravimetry and mass budget calculations. All three approaches suffer from a source separation problem where other geophysical processes limit the capability of the method to resolve the origin and magnitude of a mass change. A fourth approach, GPS vertical motion, provides localised estimates of mass change due to elastic uplift and an indirect estimate of GIA. Each approach has different source separation issues and different spatio-temporal error characteristics. In principle, it should be possible to combine the data and process covariances to minimize the uncertainty in the solution and to produce robust, posterior errors for the trends. In practice, this is a challenging problem in statistics because of the large number of degrees of freedom, the variable spatial and temporal sampling between the different observations and the fact that some processes remain under-sampled, such as firn compaction. Here, we present a novel solution to this problem using the latest methods in statistical modelling of spatio-temporal processes. We use Bayesian hierarchical modelling and employ stochastic partial differential equations to capture our physical understanding of the key processes that influence our observations. Due to the huge number of observations involved (> 10^8) methods are required to reduce the dimensionality of the problem and care is required in treatment of the observations as they are not independent. Here, we focus mainly on the results rather than the full suite of methods and we present time evolving fields of surface mass balance, ice dynamic-driven mass loss, and firn compaction for the period 2003-2009, derived from a combination of ICESat, ENVISAT, GRACE, InSAR, GPS and regional climate model output

  12. Surface mass balance studies by the Norwegian-US scientific traverse in East Antarctica

    NASA Astrophysics Data System (ADS)

    Mueller, K.; Sinisalo, A. K.; Anschuetz, H.; Hamran, S.; Hagen, J.; McConnell, J. R.; Pasteris, D. R.

    2009-12-01

    Surface mass balance (SMB) on the East Antarctic Plateau (EAP) and its variability is poorly understood due to sparse and regionally confined measurements. The joint Norwegian - U.S. IPY traverse 2007-2009 traveled east of the ice divide in Dronning Maud Land from the coast to South Pole and back via the newly discovered Recovery Lakes. We present SMB estimates derived by a C-band (5.3 GHz) ground penetrating radar (GPR) and a new ultra-wide band GPR (0.5-3 GHz) calibrated by several firn cores. Dielectric profiling (DEP) and chemistry analysis of the cores allow dating of firn layers by identifying several known volcanic events. Mean accumulation rate of 23.8 ± 4.8 kg m-2 a-1 over the last 200 years was derived by GPR for an 860 km long stretch. An empirical relationship between the GPR derived accumulation rate and SAR backscatter allows for large scale estimates of SMB. We estimate 200 year mean accumulation rate of 26.3+-3.3 kg m-2 a-1 over 76000 km2 large test area close to the ice divide. It can be further applied to the dry firn zone on the East Antarctic Plateau covered by SAR images. Centimeter scale resolution of the ultra-wide band GPR allows detailed studies of the upper 100 m of the firn pack where isochronous firn layers can be tracked with high accuracy and confidence. Comparisons to large scale mass balance studies in Antarctica show that our accumulation rates over the 200-year period lie below the lower range of the given 50-year period values, and indicate either a recent increase in accumulation rate or a former overestimation of accumulation at the ice divide of up to 50% by the previous studies. The data over the 50-year period (currently processed) will provide new information about the temporal variability of accumulation rate in large, unknown areas on EAP in a changing climate.

  13. Meteorite infall as a function of mass - Implications for the accumulation of meteorites on Antarctic ice

    NASA Technical Reports Server (NTRS)

    Huss, Gary R.

    1990-01-01

    Antarctic meteorites are considerably smaller, on average, than those recovered elsewhere in the world, and seem to represent a different portion of the mass distribution of infalling meteorites. When an infall rate appropriate to the size of Antarctic meteorites is used (1000 meteorites 10 grams or larger/sq km/1 million years), it is found that direct infall can produce the meteorite accumulations found on eight ice fields in the Allan Hills region in times ranging from a few thousand to nearly 200,000 years, with all but the Allan Hills Main and Near Western ice fields requiring less than 30,000 years. Meteorites incorporated into the ice over time are concentrated on the surface when the ice flows into a local area of rapid ablation. The calculated accumulation times, which can be considered the average age of the exposed ice, agree well with terrestrial ages for the meteorites and measured ages of exposed ice. Since vertical concentration of meteorites through removal of ice by ablation is sufficient to explain the observed meteorite accumulations, there is no need to invoke mechanisms to bring meteorites from large areas to the relatively small blue-ice patches where they are found. Once a meteorite is on a bare ice surface, freeze-thaw cycling and wind break down the meteorite and remove it from the ice. The weathering lifetime of a 100-gram meteorite on Antarctic ice is on the order of 10,000 + or - 5,000 years.

  14. Single Particle Laser Mass Spectrometry Applied to Differential Ice Nucleation Experiments at the AIDA Chamber

    SciTech Connect

    Gallavardin, S. J.; Froyd, Karl D.; Lohmann, U.; Moehler, Ottmar; Murphy, Daniel M.; Cziczo, Dan

    2008-08-26

    Experiments conducted at the Aerosol Interactions and Dynamics in the Atmosphere (AIDA) chamber located in Karlsruhe, Germany permit investigation of particle properties that affect the nucleation of ice at temperature and water vapor conditions relevant to cloud microphysics and climate issues. Ice clouds were generated by heterogeneous nucleation of Arizona test dust (ATD), illite, and hematite and homogeneous nucleation of sulfuric acid. Ice crystals formed in the chamber were inertially separated from unactivated, or ‘interstitial’ aerosol particles with a pumped counterflow virtual impactor (PCVI), then evaporated. The ice residue (i.e., the aerosol which initiated ice nucleation plus any material which was scavenged from the gas- and/or particle-phase), was chemically characterized at the single particle level using a laser ionization mass spectrometer. In this manner the species that first nucleated ice could be identified out of a mixed aerosol population in the chamber. Bare mineral dust particles were more effective ice nuclei (IN) than similar particles with a coating. Metallic particles from contamination in the chamber initiated ice nucleation before other species but there were few enough that they did not compromise the experiments. Nitrate, sulfate, and organics were often detected on particles and ice residue, evidently from scavenging of trace gas-phase species in the chamber. Hematite was a more effective ice nucleus than illite. Ice residue was frequently larger than unactivated test aerosol due to the formation of aggregates due to scavenging, condensation of contaminant gases, and the predominance of larger aerosol in nucleation.

  15. Mass Balance of Glaciers In Southern Chile, Based On Dems From Aster and Aerial Photographs

    NASA Astrophysics Data System (ADS)

    Rivera, A.; Casassa, G.; Bown, F.; Fernandez, A.

    The glaciers located in the Chilean southern Andes region (41-51S) have been re- treating and shrinking during most of the last century, in response to a climate warm- ing trend recognised in many climatic stations of the country. During recent years, several calving and small mountain glaciers have been analysed, in an attempt to cor- relate the short historical glacier variation (no longer than 150 years) with long term dendrochronological series (from 300 to 1000 years). The aim of this analysis is to un- derstand climate change during the last millennia, as well as the mechanisms of glacier response to such climatic changes. In this context, mass balance studies are one of the most important approaches to determine the specific relationship of glaciers to annual and decadal climatic changes. In Chile, only one glacier (glaciar Echaurren, 33S) has been systematically measured since 1975, generating the longest mass balance series of the country. To account for the mass balance of glaciers in the southern region of Chile, a geodetic method is presented, based upon the comparison of digital elevation models (DEM) obtained from aerial photographs and ASTER imagery from different dates. This method have been applied to glaciar Chico located at 49S in the Southern Patagonia Icefield, where we have generated DEMs from aerial photographs of 1975 and 1995, as well as one DEM from an ASTER image of October 2001. The DEMs are geo-referenced to a network of GPS points, measured in several field campaigns carried out during recent years at rock outcrops and in the accumulation area of the glacier. The last campaign was done during September and October 2001, allowing a high accuracy ground control validation for DEM derived from the contemporary ASTER image. The mass balance analysis is complemented with frontal variations derived from Landsat TM imagery, as well as field data and aerial photographs. One preliminary result of this study shows a consistent ice thinning, at

  16. The modelled surface mass balance of the Antarctic Peninsula at 5.5 km horizontal resolution

    NASA Astrophysics Data System (ADS)

    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.

    2015-09-01

    This study presents a high-resolution (~ 5.5 km) estimate of Surface Mass Balance (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 mass. Snowmelt is widespread over the AP, reaching 500 mm we yr-1 towards the northern ice 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 ice shelves. The average AP ice sheet integrated SMB, including ice 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

  17. Sustainability of algae derived biodiesel: a mass balance approach.

    PubMed

    Pfromm, Peter H; Amanor-Boadu, Vincent; Nelson, Richard

    2011-01-01

    A rigorous chemical engineering mass balance/unit operations approach is applied here to bio-diesel from algae mass culture. An equivalent of 50,000,000 gallons per year (0.006002 m3/s) of petroleum-based Number 2 fuel oil (US, diesel for compression-ignition engines, about 0.1% of annual US consumption) from oleaginous algae is the target. Methyl algaeate and ethyl algaeate diesel can according to this analysis conceptually be produced largely in a technologically sustainable way albeit at a lower available diesel yield. About 11 square miles of algae ponds would be needed with optimistic assumptions of 50 g biomass yield per day and m2 pond area. CO2 to foster algae growth should be supplied from a sustainable source such as a biomass-based ethanol production. Reliance on fossil-based CO2 from power plants or fertilizer production renders algae diesel non-sustainable in the long term. PMID:20933402

  18. Geochemical mass balances of major elements in Lake Baikal

    USGS Publications Warehouse

    Callender, E.; Granina, L.

    1997-01-01

    Major element mass balances for Lake Baikal are calculated with mostly previously published data for soluble fluxes and new, unpublished data for riverine suspended particulate matter chemistry. Physical transport seems to be the most important riverine process. The elements Ca, Mg, and Na seem to be very mobile in the weathering mantle and K and Si seem to be relatively mobile. A comparison of elemental input-output budgets and mass accumulation rates (MAR) in bottom sediments shows that most major elements, except Ca, Si, and Mn, have comparable riverine particulate matter fluxes and MARs. The addition of wet atmospheric deposition fluxes results in an excess of Ca, Mg, and Na entering the lake. The additive effect of these excess inputs during a 40-year period amounts to undetectable concentration increases in the water column. If erosion of weathered bedrock is the source of most dissolved and all particulate matter transported to the lake, theoretical elemental fluxes can be calculated with Al as the conservative element. Flux ratios (observed/theoretical) range from 0.7 to 2.2, but most fall within the acceptable range of 0.7-1.5. Major rock-forming elements are carried by rivers as weathering products and there are minimal biogeochemical processes that modify these inputs as suspended particulate matter accumulates in the bottom sediments of the lake.

  19. Coupled Gravity and Elevation Measurement of Ice Sheet Mass Change

    NASA Technical Reports Server (NTRS)

    Jezek, K. C.; Baumgartner, F.

    2005-01-01

    During June 2003, we measured surface gravity at six locations about a glaciological measurement site located on the South-central Greenland Ice. We operated a GPS unit for 90 minutes at each site -the unit was operated simultaneously with a base station unit in Sondrestrom Fjord so as to enable differential, post-processing of the data. We installed an aluminum, accumulation-rate-pole at each site. The base section of the pole also served as the mount for the GPS antenna. Two gravimeters were used simultaneously at each site. Measurements were repeated at each site with at time lapse of at least 50 minutes. We measured snow physical properties in two shallow pits The same measurement sites were occupied in 1981 and all were part of a hexagonal network of geodetic and glaciological measurements established by The Ohio State University in 1980. Additional gravity observations were acquired at three of the sites in 1993 and 1995. Gravity data were collected in conjunction with Doppler satellite measurements of position and elevation in 1981 and global positioning system measurements subsequently. The use of satellite navigation techniques permitted reoccupation of the same sites in each year to within a few 10 s of meters or better. After detrending the gravity data, making adjustments for tides and removing the residual effects of local spatial gradients in gravity, we observe an average secular decrease in gravity of about 0.01 milligal/year, but with tenths of milligal variations about the mean trend. The trend is consistent with a nearly linear increase in surface elevation of between 7 to 10 c d y r (depending on location) as measured by repeated airborne laser altimeter, surface Doppler satellite and GPS elevation measurements. Differences between the residual gravity anomalies after free air correction may be attributable to local mass changes. This project is a collaboration between the Byrd Polar Research Center of the Ohio State University and the Arctic

  20. Quantifying groundwater dependence of a sub-polar lake cluster in Finland using an isotope mass balance approach

    NASA Astrophysics Data System (ADS)

    Isokangas, E.; Rozanski, K.; Rossi, P. M.; Ronkanen, A.-K.; Kløve, B.

    2015-03-01

    A stable isotope study of 67 kettle lakes and ponds situated on an esker aquifer (90 km2) in northern Finland was carried out to determine the role and extent of groundwater inflow in groundwater-dependent lakes. Distinct seasonal fluctuations in the δ18O and δ2H values of lakes are the result of seasonal ice cover prohibiting evaporation during the winter. An iterative isotope mass balance approach was used to calculate the inflow-to-evaporation ratios (ITOT/E) of all 67 lakes during the summer of 2013 when the isotopic compositions of the lakes were approaching a steady-state. The balance calculations were carried out independently for 2H and 18O data. Since evaporation rates were derived independently of any mass balance considerations, it was possible to determine the total inflow (ITOT) and mean turnover time (MTT) of the lakes. Furthermore, the groundwater seepage rates to all studied lakes were calculated. A quantitative measure was introduced for the dependence of a lake on groundwater (G index) that is defined as the percentage contribution of groundwater inflow to the total inflow of water to the given lake. The G index values of the lakes studied ranged from ca. 39 to 98%, revealing generally large groundwater dependency among the studied lakes. This study shows the effectiveness of applying an isotope mass balance approach to quantify the groundwater reliance of lakes situated in a relatively small area with similar climatic conditions.

  1. Nitrogen mass balances for pilot-scale biofilm stabilization ponds under tropical conditions.

    PubMed

    Babu, M A; van der Steen, N P; Hooijmans, C M; Gijzen, H J

    2011-02-01

    Nitrogen removal in biofilm waste stabilization ponds were modeled using nitrogen mass balance equations. Four pilot-scale biofilm maturation ponds were constructed in Uganda. Pond 1 was control; the others had 15 baffles in each of them. Two loading conditions were investigated (period 1, 18.2g and period 2, 26.8 g NH(4)-Nd(-1)). Total nitrogen and TKN mass balances were made. Bulk water and biofilm nitrification rates were determined and used in the TKN mass balance. Results for total nitrogen mass balance showed that for both periods, denitrification was the major removal mechanism. Nitrogen uptake by algae was more important during period 1 than in period 2. The TKN mass balance predicted well effluent TKN for period 2 than period 1. This could be due to fluctuations in algae density and ammonia uptake during period 1, no conclusions on reliability of mass balance model in period 1 was made. PMID:21183339

  2. Water-mass transformation by sea ice in the upper branch of the Southern Ocean overturning

    NASA Astrophysics Data System (ADS)

    Abernathey, Ryan P.; Cerovecki, Ivana; Holland, Paul R.; Newsom, Emily; Mazloff, Matt; Talley, Lynne D.

    2016-08-01

    Ocean overturning circulation requires a continuous thermodynamic transformation of the buoyancy of seawater. The steeply sloping isopycnals of the Southern Ocean provide a pathway for Circumpolar Deep Water to upwell from mid depth without strong diapycnal mixing, where it is transformed directly by surface fluxes of heat and freshwater and splits into an upper and lower branch. While brine rejection from sea ice is thought to contribute to the lower branch, the role of sea ice in the upper branch is less well understood, partly due to a paucity of observations of sea-ice thickness and transport. Here we quantify the sea-ice freshwater flux using the Southern Ocean State Estimate, a state-of-the-art data assimilation that incorporates millions of ocean and ice observations. We then use the water-mass transformation framework to compare the relative roles of atmospheric, sea-ice, and glacial freshwater fluxes, heat fluxes, and upper-ocean mixing in transforming buoyancy within the upper branch. We find that sea ice is a dominant term, with differential brine rejection and ice melt transforming upwelled Circumpolar Deep Water at a rate of ~22 × 106 m3 s-1. These results imply a prominent role for Antarctic sea ice in the upper branch and suggest that residual overturning and wind-driven sea-ice transport are tightly coupled.

  3. A California Nitrogen Mass Balance: Uncertainties and information needs

    NASA Astrophysics Data System (ADS)

    Liptzin, D.; Dahlgren, R. A.

    2011-12-01

    The goal of the California Nitrogen (N) Assessment (CNA) is to evaluate the current state of N science, practice, and policy in the state of California. One component is to develop a N mass balance for the state. Because the CNA is an assessment, evaluating the data quality and quantifying uncertainty are also part of the mass balance . We estimate that a total of 1500 Gg of new reactive N is added to California every year. Of this new N, only about half of the N leaves the state while the rest is retained. The main inputs of new reactive N to California are, in order of importance: synthetic N fertilizer, fossil fuel combustion, and biological N fixation. The three largest N outputs from the state are, in order of importance, atmospheric advection, wastewater discharge to the ocean, and riverine discharge to the ocean. Approximately half of the stored N leaches to groundwater, with the other half divided between soils and vegetation, reservoirs, and urban landscapes. These N flows vary not just in magnitude, but also in the uncertainty associated with them. There was no trend in the tonnage of fertilizer sold from 1981-2001, but the 2002-2007 average has remained higher (760 Gg N) than the long-term average (520 Gg N). Bottom up calculations based on crop acreage and fertilization rates are more consistent with the 1980-2001 average suggesting a problem with the sales data. The emission of NOx from fossil fuel burning is one of the most well established flows of N. The production of ammonia and nitrous oxide from fossil fuel combustion is significantly lower than NOx, but there is less evidence to support the emissions inventories. Rates of biological N fixation are speculative with evidence more limited in natural lands than croplands. For most crops it appears that N fixation rates are strongly related to plant production, suggesting that using a single rate across large regions may be inappropriate. In addition, many studies either only measure aboveground N

  4. ASTER image based assessment of glacier mass balance of Nanga Parbat massif, Pakistan

    NASA Astrophysics Data System (ADS)

    Kargel, Jeffrey; Leonard, Gregory; Haritashya, Umesh

    2014-05-01

    Starting with the analytical approach given in detail by Nuth and Kääb (2011; henceforth NK2011), we have further developed an approach toward analysis of repeat stereo ASTER-derived DEMs to extract specific and net annual mass balance of glaciers of Nanga Parbat, Pakistan. We used the approach of NK2011 to coregister DEMs obtained from ASTER stereo images acquired in September 2004 and October 2010, and the glacier outlines produced by Haritashya et al. (2014 in prep) as a mask to isolate glacier from stable (nonglacier) areas. We then devised a protocol to remove DEM data deemed to be the pits, cones, and bulges that are common artifacts with ASTER DEM data. We developed an approach similar to that given by NK2011 to make corrections for cross- and along-track errors of elevation differences and to zero out the mean elevation difference bias for stable (non-glacier points). The largest sources of correctable error were cross-track and along-track slope-dependent artifacts, which we corrected using an approach modified from that of NK2011. Several small systematic errors, such as that related to elevation, became even smaller when cross- and along-track errors were corrected. We then proceeded to analyze the statistics for the cumulative ice area and for individual glaciers. Also using the DEM-change spread function for stable areas, we deconvolved the random error from the actual change signal present in the glacier areas. Ten glaciers of Nanga Parbat thinned by an average of 6 m, i.e., 1 m/year over the 6-year period. Ice in the highest elevations remained fairly stable or even thickened by a few meters, whereas that in lower elevations thinned. Bazhin Glacier apparently was undergoing a surge-like phenomenon of rapid mass transfer from higher elevations (where thinning occurred) to lower elevations (where it thickened), though the terminus advanced by only ~182 m (Haritashya et al. 2014). Hence, our results indicate fluctuations of glaciers in Nanga Parbat

  5. Mass balance of Greenland from GRACE, altimetry and GPS uplift by integrated inversion

    NASA Astrophysics Data System (ADS)

    Forsberg, R.; Sandberg, L.; Barletta, V.

    2013-12-01

    With more than 10 years of GRACE satellite data now available, the ice mass loss trend of Greenland are clearly demonstrating ice mass loss in marginal zones of the ice sheets, and increasing mass loss trends in some regions such as the north west marginal regions. Although the GRACE release-5 products have provided a significant increase in resolution, the detailed space-based detection of where the ice sheet is loosing mass needs to come from other sources, notably altimetry (IceSat, EnviSat and CryoSat) which clearly points out the areas of change, but also GPS uplift, which can give a high temporal resolution from the elastic effects in the surrounding regions of the observation sites. In the paper we outline a novel direct inversion method, where all satellite and GPS data can be utilized in a general inverse estimation scheme. In the method systematic errors, such as errors in conversion of surface elevation change to mass changes, and GIA effects, are lumped into correction surfaces which can be estimated empirically as well from the data. We demonstrate overall mass change results from Greenland 2003-12, with the accelerating overall mass loss of around 240 GT/yr strongly constrained by the GRACE data, and the change regions clearly outlined by IceSat and CryoSat.

  6. A two-dimensional energy balance climate model including radiation and ice caps-albedo feedback

    NASA Astrophysics Data System (ADS)

    Yingyi, Chen; Jiping, Chao

    1984-11-01

    A simplified two-dimensional energy balance climate model including the solar and infrared radiation transports, the turbulent exchanges of heat in vertical and horizontal directions and the ice caps-albedo feedback is developed. The solutions show that if the atmosphere is considered as a grey body and the grey coefficient depends upon the distributions of absorption medium and cloudiness, both horizontal and vertical distribution of temperature are identical to the observation. On the other hand, comparing the models that the atmosphere is considered as a grey body with ones that the infrared radiation is parameterized as a linear function of temperature, as was considered by Budyko, Sellers(1969), then the results show that even though both of them can obtain the earth's surface temperature in agreement with the observation, the sensitivity of the climate to the changes of solar constant is very different. In the former case, the requirement for the ice edge to move southward from the normal 72°N to 50°N(i.e. where the glacial climate would take place) is that the solar constant should decrease by 13% to 16%. However, in the latter case, the climate is highly sensitive to the changes of solar radiation. In this case, the requirement of solar radiation occurring in the glacial climate should decrease by, 2% to 6%. According to the investigations mentioned above we must be careful when the parameterizations of the radiation and other processes are conducted in a climate model., otherwise the reliability of the results is suspicious.

  7. Considerations affecting the additional weight required in mass balance of ailerons

    NASA Technical Reports Server (NTRS)

    Diehl, W S

    1937-01-01

    This paper is essentially a consideration of mass balance of ailerons from a preliminary design standpoint, in which the extra weight of the mass counterbalance is the most important phase of the problem. Equations are developed for the required balance weight for a simple aileron and this weight is correlated with the mass-balance coefficient. It is concluded the location of the c.g. of the basic aileron is of paramount importance and that complete mass balance imposes no great weight penalty if the aileron is designed to have its c.g. inherently near to the hinge axis.

  8. Time Series of Greenland Ice-Sheet Elevations and Mass Changes from ICESat 2003-2009

    NASA Astrophysics Data System (ADS)

    Zwally, H. J.; Li, J.; Medley, B.; Robbins, J. W.; Yi, D.

    2015-12-01

    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 ice 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 ice volume change estimates. The I(t) are especially useful for studying the seasonal cycle of mass 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 ice 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 ice flow is at a rate of 1 m/yr, giving an annual mass 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

  9. Fe and Cu isotope mass balances in the human body

    NASA Astrophysics Data System (ADS)

    Balter, V.; Albarede, F.; Jaouen, K.

    2011-12-01

    The ranges of the Fe and Cu isotope compositions in the human body are large, i.e. ~3% and ~2%, respectively. Both isotopic fractionations appear to be mainly controlled by redox conditions. The Fe and Cu isotope compositions of the tissues analyzed so far plot on a mixing hyperbolae between a reduced and an oxidized metals pools. The reduced metals pool is composed by erythrocytes, where Fe is bounded to hemoglobin as Fe(II) and Cu to superoxide-dismutase as Cu(I). The oxidized metals pool is composed by hepatocytes, where Fe and Cu are stored as Fe(III) ferritin and as Cu(II) ceruloplasmine, respectively. The position of each biological component in the δ56Fe-δ65Cu diagram therefore reflects the oxidation state of Fe and Cu of the predominant metal carrier protein and allows to quantify Fe and Cu fluxes between organs using mass balance calculations. For instance, serum and clot Fe and Cu isotope compositions show that current biological models of erythropoiesis violates mass conservation requirements, and suggest hidden Fe and Cu pathways during red blood cells synthesis. The results also show that a coupled Fe-Cu strong gender isotopic effect is observed in various organs. The isotopic difference between men and women is unlikely to be due to differential dietary uptake or endometrium loss, but rather reflects the effect of menstrual losses and a correlative solicitation of hepatic stores. We speculate that thorough studies of the metabolism of stable isotopes in normal conditions is a prerequisite for the understanding of the pathological dysregulations.

  10. A 30-year record of surface mass balance (1966-95) and motion and surface altitude (1975-95) at Wolverine Glacier, Alaska

    USGS Publications Warehouse

    Mayo, Lawrence R.; Trabant, Dennis C.; March, Rod S.

    2004-01-01

    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 mass balance of the surface strata-snow, new firn, superimposed ice, and old firn and ice mass at each site were based on these measurements. Calculations of fixed-date annual mass balances for each hydrologic year (October 1 to September 30), as well as net balances and the dates of minimum net balance measured between time-transgressive summer surfaces on the glacier, were made on the basis of the strata balances augmented by air temperature and precipitation recorded in the basin. From 1966 through 1995, the average annual balance 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 mass balance stake, and glacier surface altitudes was added to the data set in 1975 to detect the glacier motion responses to variable climate and mass balance 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.

  11. Oxalate Mass Balance During Chemical Cleaning in Tank 5F

    SciTech Connect

    Poirier, M.; Fink, S.

    2011-07-08

    The Savannah River Site (SRS) is preparing Tank 5F for closure. The first step in preparing the tank for closure is mechanical sludge removal. Following mechanical sludge removal, SRS performed chemical cleaning with oxalic acid to remove the sludge heel. Personnel are currently assessing the effectiveness of the chemical cleaning to determine whether the tank is ready for closure. SRS personnel collected liquid samples during chemical cleaning and submitted them to Savannah River National Laboratory (SRNL) for analysis. Following chemical cleaning, they collected a solid sample (also known as 'process sample') and submitted it to SRNL for analysis. The authors analyzed these samples to assess the effectiveness of the chemical cleaning process. Analysis of the anions showed the measured oxalate removed from Tank 5F to be approximately 50% of the amount added in the oxalic acid. To close the oxalate mass balance, the author collected solid samples, leached them with nitric acid, and measured the concentration of cations and anions in the leachate.

  12. CMB8: New software for chemical mass balance receptor modeling

    SciTech Connect

    Lewis, C.W.

    1997-12-31

    The Chemical Mass Balance (CMB) method for receptor modeling of ambient air pollutants has been in use for over two decades. over the past year the U.S. Environmental Protection Agency`s Office of Research and Development and Office of Air Quality Planning and standards have jointly sponsored the development of a new generation of CMB software, CMB8. Developmental work has been performed by the Desert Research Institute, Reno, NV. Changes embodied in CMB8 include (1) switch from a DOS-based to a Windows-based environment, (2) increased attention to volatile organic compounds (VOC) applications, (3) correction of some flaws in the previous version (CMB7), (4) more options for input and output data formats, (5) addition of a more accurate least squares computational algorithm, (6) a new treatment of source collinearity, (7) multiple defaults for sources and fitting species, and (8) choice of fitting criteria. Details of the changes and the procedure for obtaining CMB8 are given.

  13. Biogeochemical phosphorus mass balance for Lake Baikal, southeastern Siberia, Russia

    USGS Publications Warehouse

    Callender, E.; Granina, L.

    1997-01-01

    Extensive data for Lake Baikal have been synthesized into a geochemical mass balance for phosphorus (P). Some of the P budget and internal cycling terms for Baikal have been compared to similar terms for oligotrophic Lake Superior, mesotrophic Lake Michigan and the Baltic Sea, and the Ocean. Lake Baikal has a large external source of fluvial P compared to the Laurentian upper Great Lakes and the Ocean. The major tributary to Lake Baikal has experienced substantial increases in organic P loading during the past 25 years. This, coupled with potential P inputs from possible phosphorite mining, may threaten Baikal's oligotrophic status in the future. Water-column remineralization of particulate organic P is substantially greater in Lake Baikal than in the Laurentian Great Lakes. This is probably due to the great water depths of Lake Baikal. There is a gradient in P burial efficiency, with very high values (80%) for Lake Baikal and Lake Superior, lower values (50%) for Lake Michigan and the Baltic Sea, and a low value (13%) for the Ocean. The accumulation rate of P in Lake Baikal sediments is somewhat greater than that in the Laurentian upper Great Lakes and the Baltic Sea, and much greater than in the Ocean. Benthic regeneration rates are surprisingly similar for large lacustrine and marine environments and supply less than 10% of the P utilized for primary production in these aquatic environments.

  14. Stable isotope mass balance of lakes: a contemporary perspective

    NASA Astrophysics Data System (ADS)

    Gibson, J. J.; Birks, S. J.; Yi, Y.

    2016-01-01

    The theoretical basis for application of stable isotope mass balance of lakes is described for a range of climatic situations including low latitude, high latitude, high altitude, continental and coastal systems, as well as cases where the atmospheric boundary layer is significantly modified by the lake evaporation process. The effects of seasonality on isotopic offset between precipitation and atmospheric vapour and the slope of the local evaporation line are described. Atmospheric feedback and its role in labelling the isotopic composition of the Laurentian Great Lakes and tropical lakes is discussed. Several important considerations are suggested to improve parameterization of quantitative paleoclimatic reconstructions including use of assumptions that are appropriate for the climatic setting, for the atmospheric feedback situation, for salinity, and headwater setting. Potential for use of dual-isotopes to trace past changes in seasonality and input, and a dual-lake index method that can potentially be used to trace connectivity of lakes are presented. In cases where modern or paleo-evaporation systems may be under-defined there are inherent limitations in the degree of quantification that can be attained.

  15. Mass and energy balance in the 1973 August 9 flare

    NASA Technical Reports Server (NTRS)

    Dere, K. P.; Cook, J. W.

    1983-01-01

    The mass and energy balance of the thermal plasma during the decay phase of the solar flare of August 9, 1973, are studied. The analysis is based on observationally determined values for the differential emission measure, density, turbulent and bulk velocities, and physical dimensions. The total particle content and total thermal energy content of the flare plasmas with temperatures above 100,000 K and their variation with time are calculated. The particle loss and the energy losses through radiation, conduction, and convection are evaluated. The decrease in total particle content can be accounted for by the convective losses through the loop footprints at 100,000 K. Radiation is the dominant energy loss mechanism although convective losses at 100,000 K can be important. Conductive losses at 100,000 K into cooler chromospheric material appear to be negligible. The decrease in the total energy content during the decay phase is equal to the sum of the energy losses over the period of observation. No requirement is found for continued heating during the decay phase.

  16. Diet modification to reduce phosphorus surpluses: a mass balance approach.

    PubMed

    Maguire, R O; Crouse, D A; Hodges, S C

    2007-01-01

    Diet modification to reduce phosphorus (P) concentrations in manures has been developed in response to environmental concerns over P losses from animal agriculture to surface waters. We used USDA-NASS statistics on animal numbers and crop production to calculate county scale mass balances for manure P production, P removed in harvested portion of crops, and the potential effects of diet modification. Although spreading manure evenly over all crop acreage within a county is unlikely to occur, these calculations give a good indication as to the impact diet modification to reduce P can have at a regional or national scale. There was a high degree of regional variability in manure P surpluses (e.g., with the large crop acreages in the grain belt leading to large P offtake in crops preventing most P surpluses). In 89% of counties, there was a deficit of manure P relative to crop P removal; therefore there was a manure P surplus in 11% of counties. Diet modification decreased the percentage of states with a manure P surplus from 11 to 8%, a decrease of approximately 27%. Diet modification decreased the percentage of counties with the greatest surpluses of manure P (>30 kg ha(-1)) from 3% of all counties to 1%. Diet modification to decrease manure P is an important part of strategies to alleviate environmental concerns associated with surplus manure P in many areas, but additional strategies to deal with manure P surpluses are needed in some areas. PMID:17636283

  17. Mass balance and composition analysis of shredder residue.

    SciTech Connect

    Pomykala, J. A., Jr.; Jody, B. J.; Spangenberger, J. S.; Daniels, E. J.; Energy Systems

    2007-01-01

    The process of shredding end-of-life vehicles to recover metals results in a byproduct commonly referred to as shredder residue. The four-and-a-half million metric tons of shredder residue produced annually in the United States is presently land filled. To meet the challenges of automotive materials recycling, the U.S. Department of Energy is supporting research at Argonne National Laboratory in cooperation with the Vehicle Recycling Partnership (VRP) of the United States Council for Automotive Research (USCAR) and the American Plastics Council. This paper presents the results of a study that was conducted by Argonne to determine variations in the composition of shredder residue from different shredders. Over 90 metric tons of shredder residues were processed through the Argonne pilot plant. The contents of the various separated streams were quantitatively analyzed to determine their composition and to identify materials that should be targeted for recovery. The analysis established a reliable mass balance for the different materials in shredder residue.

  18. Spatial and temporal Antarctic Ice Sheet mass trends, glacio-isostatic adjustment, and surface processes from a joint inversion of satellite altimeter, gravity, and GPS data

    NASA Astrophysics Data System (ADS)

    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.

    2016-02-01

    We present spatiotemporal mass balance trends for the Antarctic Ice 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 ice dynamics, surface mass balance 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 mass 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 mass 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 mass loss is partly compensated by a significant mass gain of 56 ± 18 Gt yr-1 in East Antarctica due to a positive trend of surface mass balance anomalies.

  19. Surface water mass composition changes captured by cores of Arctic land-fast sea ice

    NASA Astrophysics Data System (ADS)

    Smith, I. J.; Eicken, H.; Mahoney, A. R.; Van Hale, R.; Gough, A. J.; Fukamachi, Y.; Jones, J.

    2016-04-01

    In the Arctic, land-fast sea ice growth can be influenced by fresher water from rivers and residual summer melt. This paper examines a method to reconstruct changes in water masses using oxygen isotope measurements of sea ice cores. To determine changes in sea water isotope composition over the course of the ice growth period, the output of a sea ice thermodynamic model (driven with reanalysis data, observations of snow depth, and freeze-up dates) is used along with sea ice oxygen isotope measurements and an isotopic fractionation model. Direct measurements of sea ice growth rates are used to validate the output of the sea ice growth model. It is shown that for sea ice formed during the 2011/2012 ice growth season at Barrow, Alaska, large changes in isotopic composition of the ocean waters were captured by the sea ice 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 ice 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 masses as indicated by oxygen isotope composition can be reconstructed using oxygen isotope analysis of sea ice 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 ice regions, which is important for climate studies in a rapidly changing Arctic. Land-fast sea ice 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 mass component proportion calculations. In particular, the equations given can be used to inform choices made when

  20. Airborne Tomographic Swath Ice Sounding Processing System

    NASA Technical Reports Server (NTRS)

    Wu, Xiaoqing; Rodriquez, Ernesto; Freeman, Anthony; Jezek, Ken

    2013-01-01

    Glaciers and ice 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 mass balance and dynamics. To estimate the current ice mass balance, and to predict future changes in the motion of the Greenland and Antarctic ice sheets, it is necessary to know the ice sheet thickness and the physical conditions of the ice sheet surface and bed. This information is required at fine resolution and over extensive portions of the ice sheets. A tomographic algorithm has been developed to take raw data collected by a multiple-channel synthetic aperture sounding radar system over a polar ice sheet and convert those data into two-dimensional (2D) ice thickness measurements. Prior to this work, conventional processing techniques only provided one-dimensional ice thickness measurements along profiles.

  1. Reducing uncertainties in Antarctic ice sheet mass loss projections

    NASA Astrophysics Data System (ADS)

    Pattyn, Frank; Durand, Gaël

    2014-05-01

    Climate model projections are often aggregated into multi-model averages of all models participating in an Intercomparison Project, such as CMIP. Several authors have questioned whether this is the best use of the information and whether the community is ready to move beyond the 'one-model-one-vote' approach, based on the intrinsic quality of each of the models. Ice sheet models are not as far developed as climate or ocean models. Many of these models are still struggling over basic thermo-mechanical issues related to ice deformation, while at the same time disproportionate efforts are made on the interaction with the atmosphere, basal hydrology, sliding, sediment deformation, ice/ocean interaction, calving, grounding-line migration, etc. We can therefore reasonably question whether averaging all model results at equal weight is the best strategy and to which extent coupling of ice sheet models that are lacking the representation of crucial physical processes, to other components of the climate system could lead to spurious errors. We now have tools available to test parts of the response of marine ice sheet models to perturbations of climatic and/or oceanic origin. Results show that the type of model as well as the way boundary conditions are implemented greatly affects the response of each ice sheet system. Based on MISMIP experimental output as well as the experimental response of Antarctic glaciers and drainage basins to ocean perturbations (e.g. Favier et al., 2014), we provide a guidance for the evaluation of model-response to perturbations on Century time scales.

  2. Early 21st-Century Mass loss of the North-Atlantic Glaciers and Ice Caps (Arne Richter Award for Outstanding Young Scientists Lecture)

    NASA Astrophysics Data System (ADS)

    Wouters, Bert; Ligtenberg, Stefan; Moholdt, Geir; Gardner, Alex S.; Noel, Brice; Kuipers Munneke, Peter; van den Broeke, Michiel; Bamber, Jonathan L.

    2016-04-01

    Historically, ice loss from mountain glaciers and ice caps has been one of the largest contributors to sea level rise over the last century. Of particular interest are the glaciers and ice 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 ice 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 ice caps. In this presentation, we will discuss the progress that has been made in estimating the ice mass balance 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 mass loss in the North Atlantic. We find excellent agreement between the altimetry measurements and independent observations by the GRACE mission, which directly 'weighs' the ice caps, albeit at a much lower resolution. Mass 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 ice caps. Importantly, the mass loss is not stationary, but shows large regional interannual variability, with mass loss shifting between eastern and western regions from year to year. Comparison with regional climate models shows that these shifts can be

  3. Very high resolution surface mass balance over Greenland modeled by the regional climate model MAR with a downscaling technique

    NASA Astrophysics Data System (ADS)

    Kittel, Christoph; Lang, Charlotte; Agosta, Cécile; Prignon, Maxime; Fettweis, Xavier; Erpicum, Michel

    2016-04-01

    This study presents surface mass balance (SMB) results at 5 km resolution with the regional climate MAR model over the Greenland ice sheet. Here, we use the last MAR version (v3.6) where the land-ice 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 mass balance data base than the extrapolated 10 km MAR SMB results.

  4. Application of terrestrial photogrammetry for the mass balance calculation on Montasio Occidentale Glacier (Julian Alps, Italy)

    NASA Astrophysics Data System (ADS)

    Piermattei, Livia; Carturan, Luca; Calligaro, Simone; Blasone, Giacomo; Guarnieri, Alberto; Tarolli, Paolo; Dalla Fontana, Giancarlo; Vettore, Antonio

    2014-05-01

    Digital elevation models (DEMs) of glaciated terrain are commonly used to measure changes in geometry and hence infer the mass balance 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 mass balance 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, ice, 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

  5. The influence of mantle viscosity structure and past decadal to millennial-scale ice mass changes on present-day land motion in Greenland.

    NASA Astrophysics Data System (ADS)

    Simpson, Matthew; Wake, Leanne; Milne, Glenn; Huybrechts, Philippe

    2010-05-01

    We show predictions of present-day vertical land motion in Greenland using a recently developed Glacial Isostatic Adjustment (GIA) model, calibrated using both relative sea-level observations and geomorphological contraints on ice extent (Simpson et al., 2009). Predictions from our GIA model are in good agreement to the relatively small number of GPS measurements of absolute vertical motion from south and southwest Greenland. This suggests that our model of ice sheet evolution over the Holocene period is reasonably accurate. The uplift predictions are highly sensitive to variations of upper mantle viscosity; depending on the Earth model adopted different periods of ice loading change dominate the present-day response in particular regions of Greenland. We shall present a suite of results to demonstrate this sensitivity. We also consider the possible influence of more recent changes in the ice sheet by applying a second ice model; specifically, a surface mass balance (SMB) model (Wake et al., 2009), which covers the period 1866 to 2005. Predictions from this model suggest that decadal-scale SMB changes over the last c. 140 years play only a small role in determining the present-day viscous response. However, high rates of peripheral thinning from 1995 to 2005 in the SMB model produce large elastic uplift rates in west and southwest Greenland. Using the same SMB model, we extend our study period to cover the last thousand years (for which there is less accurate climate data) and constrain ice mass changes over this time using new high resolution records of relative sea-level change. Our preliminary findings suggest that century-scale ice mass variation over the last thousand years may contribute significantly to the present-day viscous response. Simpson, M.J.R, Milne, G.A., Huybrechts, P., Long, A.J., 2009. Calibrating a glaciological model of the Greenland ice sheet from the last glacial maximum to present-day using field observations of relative sea level and ice

  6. Simple energy balance model resolving the seasons and the continents - Application to the astronomical theory of the ice ages

    NASA Technical Reports Server (NTRS)

    North, G. R.; Short, D. A.; Mengel, J. G.

    1983-01-01

    An analysis is undertaken of the properties of a one-level seasonal energy balance climate model having explicit, two-dimensional land-sea geography, where land and sea surfaces are strictly distinguished by the local thermal inertia employed and transport is governed by a smooth, latitude-dependent diffusion mechanism. Solutions of the seasonal cycle for the cases of both ice feedback exclusion and inclusion yield good agreements with real data, using minimal turning of the adjustable parameters. Discontinuous icecap growth is noted for both a solar constant that is lower by a few percent and a change of orbital elements to favor cool Northern Hemisphere summers. This discontinuous sensitivity is discussed in the context of the Milankovitch theory of the ice ages, and the associated branch structure is shown to be analogous to the 'small ice cap' instability of simpler models.

  7. Glaciers in a changing global climate: first results of worldwide glacier mass balance measurements 2000/2001

    NASA Astrophysics Data System (ADS)

    Frauenfelder, R.; Hoelzle, M.; Haeberli, W.

    2003-04-01

    Glacier signals from mountain areas are key elements of early detection strategies for dealing with possible man-induced climate change. The IPCC Third Assessment Report indeed defines mountain glaciers as one of the best natural indicators of atmospheric warming with the highest reliability ranking. In the chain of processes linking climate and glacier fluctuations, glacier length variation is the indirect/delayed response, whereas glacier mass change is the direct/undelayed reaction. Internationally coordinated long-term monitoring of glaciers started in 1894. The responsibility to collect and publish standardized data has been assumed since 1986 by the World Glacier Monitoring Service (WGMS). This work is primarily being carried out under the auspices of the International Commission on Snow and Ice (ICSI/IAHS) and the Federation of Astronomical and Geophysical Services (FAGS/ICSU). The WGMS maintains data exchange with the ICSU World Data Center A (WDC-A) for Glaciology in Boulder, Colorado. Corresponding data bases and measurement networks form an essential part of the Global Terrestrial Network for Glaciers (GTN-G: operated by the WGMS) as a pilot project within the Global Terrestrial Observing System (GTOS/GCOS). A network of 60 glacier mass balance observations provides information on presently observed rates of change in glacier mass, corresponding acceleration trends and regional distribution patterns. A preliminary calculation of the mass balance observations in 2000/2001 relating to 23 selected data sets provide a mean specific (annual) net balance of -367 mm w.e., 26 % of the observed balances were positive. The corresponding mean in six mountain ranges was -571 mm w.e. Such values indicate that mass losses in 2000/2001 have been less extreme than in the extraordinary years before but are still strongly negative. Over the past two decades glacier melt appears to continue at a considerable and possibly even an accelerating rate. The observed average

  8. The modelled surface mass balance of the Antarctic Peninsula at 5.5 km horizontal resolution

    NASA Astrophysics Data System (ADS)

    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.

    2016-02-01

    This study presents a high-resolution (˜ 5.5 km) estimate of surface mass balance (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 six 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, complicating a full model evaluation. The SMB map reveals large accumulation gradients, with precipitation values above 3000 mm we yr-1 in the western AP (WAP) and below 500 mm we yr-1 in the eastern AP (EAP), not resolved by coarser data sets such as ERA-Interim. The average AP ice-sheet-integrated SMB, including ice 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 modelled AP SMB components, except for snowmelt that shows a significant decrease over the last 36 years (-0.36 Gt yr-2).

  9. Chloride-Mass-Balance: Cautions in Predicting Increased Recharge Rates

    SciTech Connect

    Gee, Glendon W.; Zhang, Z. F.; Tyler , S. W.; Albright , W. H.; Singleton , M. J.

    2005-02-01

    The chloride-mass-balance (CMB) method has been used extensively to estimate recharge in arid and semi-arid environments. Required data include estimates of annual precipitation, total chloride input (from dry fallout and precipitation), and pore-water chloride concentrations. Typically, CMB has been used to estimate ancient recharge but recharge from recent land-use change has also been documented. Recharge rates below a few mm/yr are reliably detected with CMB; however, estimates above a few mm/yr appear to be less reliable. We tested the CMB method against 26 years of drainage from a 7.6 m deep lysimeter at a simulated waste-burial ground, located on the Department of Energy’s Hanford Site in southeastern Washington State, USA where land-use change has increased recharge rates. Measured drainage from the lysimeter for the past 26 years averaged 62 mm/yr. Precipitation averaged 190 mm/yr with an estimated chloride input of 0.225 mg/L. Initial pore-water chloride concentration was 88 mg/L and decreased to about 6 mg/L after 26 years, while the drainage water decreased to less than 1 mg/L. A recharge estimate made using chloride concentrations in drain water was within 20% of the measured drainage rate. In contrast, recharge estimates using 1:1 (water: soil) extracts were lower than actual by factors ranging from 2 to 8 or more. The results suggest that when recharge is above a few mm/yr, soil water extracts can lead to unreliable estimates of recharge. For conditions of elevated recharge, direct sampling of pore water is the preferred method, because chloride concentrations are often 20 to 50 times higher in directly-sampled pore water than in pore-water extracts.

  10. Mass balance investigation of alpine glaciers through LANDSAT TM data

    NASA Technical Reports Server (NTRS)

    Bayr, Klaus J.

    1989-01-01

    An analysis of LANDSAT Thematic Mapper (TM) data of the Pasterze Glacier and the Kleines Fleisskees in the Austrian Alps was undertaken and compared with meteorological data of nearby weather stations. Alpine or valley glaciers can be used to study regional and worldwide climate changes. Alpine glaciers respond relatively fast to a warming or cooling trend in temperature through an advance or a retreat of the terminus. In addition, the mass balance of the glacier is being affected. Last year two TM scenes of the Pasterze Glacier of Aug. 1984 and Aug. 1986 were used to study the difference in reflectance. This year, in addition to the scenes from last year, one MSS scene of Aug. 1976 and a TM scene from 1988 were examined for both the Pasterze Glacier and the Kleines Fleisskees. During the overpass of the LANDSAT on 6 Aug. 1988 ground truthing on the Pasterze Glacier was undertaken. The results indicate that there was considerable more reflectance in 1976 and 1984 than in 1986 and 1988. The climatological data of the weather stations Sonnblick and Rudolfshuette were examined and compared with the results found through the LANDSAT data. There were relations between the meteorological and LANDSAT data: the average temperature over the last 100 years showed an increase of .4 C, the snowfall was declining during the same time period but the overall precipitation did not reveal any significant change over the same period. With the use of an interactive image analysis computer, the LANDSAT scenes were studied. The terminus of the Pasterze Glacier retreated 348 m and the terminus of the Kleines Fleisskees 121 m since 1965. This approach using LANDSAT MSS and TM digital data in conjunction with meteorological data can be effectively used to monitor regional and worldwide climate changes.

  11. The formation of a clinopyroxene corona — Mass balance considerations

    NASA Astrophysics Data System (ADS)

    Zingg, Andrew J.

    1992-06-01

    The formation of a Cpx-corona is discussed from the viewpoint of continuous reaction techniques. Two cases are distinguished: a closed and open system. The first case is based on the equation eOl w + aPl u = bPl v + Opx x + cCpx y + dSpl y Plagioclase is assumed to be a solid solution between anorthite and albite (Na uCa 1-wAl 2-uSi 2+uO 8). The other minerals are solutions of their Fe- and Mg-end-members [e.g. (Mg wFe 1-w) 2SiO 4 for olivine]. Spinel forms a ternary system of hercynite-spinel-magnetite. Stoichiometric coefficients are expressed in terms of the exchange parameters t, u, v, w, x, y and z. According to stoichiometries, the net molar quantity of phaligioclase consumed equals the number of moles of clinopyroxene and spinel produced. For each mole of olivine consumed there is one mole of opx produced. A closed system is suggested by the ability to predict one of the mineral compositions in terms of the others using one of the six mass balances (Na, Ca, Mg, Fe, Al, Si) left from the calculation of five stoichiometric coefficients. This model allows the calculation of mass transfer between different shells and explains coronas from the Adirondacks, Scandinavia and the Niquelândia layered complex (Brazil). In the second case the system is open and is described by the equation. Opx x + aPl u + kCa 2+ + hSi 4+ + fFe 2+ = cCpx y + lNa + + lAl 3 + gMg 2+ The compositional variation of orthopyroxene and clinopyroxene allows the determination of c(Cpx), -(Fe 2+) and g(Mg 2+) which are interdependent. With a known value of c and assuming a constant volume of reaction the value of a may be determined. The final equation, for a plagioclase composition of XAn = 0.75, is 1 Opx + 0.35 Pl + 0.74 Ca 2+ + 0.21 Si 4+ + 0.10 Mg 2+ = 1 Cpx + 0.61 Al 3+ + 0.10 Fe 2+ + 0.09 Na + This is the reaction responsible for the formation of Cpx-coronas in the Bushveld complex.

  12. A MASS BALANCE OF SURFACE WATER GENOTOXICITY IN PROVIDENCE RIVER (RHODE ISLAND USA)

    EPA Science Inventory

    White and Rasmussen (Mutation Res. 410:223-236) used a mass balance approach to demonstrate that over 85% of the total genotoxic loading to the St. Lawrence River at Montreal is non-industrial. To validate the mass balance approach and investigate the sources of genotoxins in sur...

  13. Mass balance, energy and exergy analysis of bio-oil production by fast pyrolysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mass, energy and exergy balances are analyzed for bio-oil production in a bench scale fast pyrolysis system developed by the USDA’s Agricultural Research Service (ARS) for the processing of commodity crops to fuel intermediates. Because mass balance closure is difficult to achieve due, in part, to ...

  14. Results of the Lake Michigan Mass Balance Project: Atrazine Modeling Report

    EPA Science Inventory

    This report covers an overview of chemical properties, measurements in air and water, model construct and assumptions, and results of mathematical mass balance modeling of the herbicide atrazine in the Lake Michigan basin. Within the context of the mass balance, an overview of a...

  15. The surface mass and energy balance of Nordenskiöldbreen, Svalbard: 7 years of in situ observations.

    NASA Astrophysics Data System (ADS)

    Tijm-Reijmer, Carleen; Pohjola, Veijo; Van Pelt, Ward; Pettersson, Rickard

    2014-05-01

    In spring 2006 a climate monitoring program on Nordenskiöldbreen, Svalbard, was initiated, which is still on going. The program focuses on the dynamics and mass budget of the glacier, and includes mass balance (stake and sonic height ranger) and automatic weather station (AWS) observations. The annual mass balance observations show large variability and no trend over the observational period (2006-2013). The equilibrium line altitude (ELA) during this period is located at about 610 m a.s.l. This is in line with the average ELA over the period 1989-2010 of 631 m a.s.l. based on output of a distributed energy balance model (EBM), and slightly higher than presented in literature for this area. At the AWS site (±600 m a.s.l.) the average annual temperature is about -8.5°C. Annual mean wind speed is about 4.5 m/s and is predominantly directed down glacier with a directional constancy of about 0.65, a predominant katabatic wind. Throughout the year the sensible heat flux is positive due to a constant surface based temperature inversion. From May to September this temperature inversion is caused by cooling of the surface by long wave radiation while in the summer months the surface temperature is limited by 0°C, the temperature of a melting surface. At the AWS site the amount of melt energy available in the summer months corresponds to about 0.82 m w.e. snow and ice melt. This is less than derived from the observations (1.1 m w.e. of which 0.7 m w.e. is ice melt). This is due to problems with the temperature observations in the summer months resulting in an underestimation of the sensible heat flux towards the surface and consequently an underestimation of the melt flux.

  16. Greenland Ice Sheet seasonal and spatial mass variability from model simulations and GRACE (2003-2012)

    NASA Astrophysics Data System (ADS)

    Alexander, Patrick M.; Tedesco, Marco; Schlegel, Nicole-Jeanne; Luthcke, Scott B.; Fettweis, Xavier; Larour, Eric

    2016-06-01

    Improving the ability of regional climate models (RCMs) and ice sheet models (ISMs) to simulate spatiotemporal variations in the mass of the Greenland Ice Sheet (GrIS) is crucial for prediction of future sea level rise. While several studies have examined recent trends in GrIS mass loss, studies focusing on mass variations at sub-annual and sub-basin-wide scales are still lacking. At these scales, processes responsible for mass change are less well understood and modeled, and could potentially play an important role in future GrIS mass change. Here, we examine spatiotemporal variations in mass 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 mass variations against those simulated by the Modèle Atmosphérique Régionale (MAR) RCM and the Ice Sheet System Model (ISSM). In order to properly compare spatial and temporal variations in GrIS mass from GRACE with model outputs, we find it necessary to spatially and temporally filter model results to reproduce leakage of mass 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 mass over the period examined, but the models appear to underestimate the rate of mass loss, especially in areas below 2000 m in elevation, where the majority of recent GrIS mass loss is occurring. On an ice-sheet-wide scale, the timing of the modeled seasonal cycle of cumulative mass (driven by summer mass loss) agrees with the GRACE-derived seasonal cycle, within limits of uncertainty from the GRACE solution. However, on sub-ice-sheet-wide scales, some areas exhibit significant differences in the timing of peaks in the annual cycle of mass change. At these scales, model biases, or processes not accounted for by models related

  17. Ice Stream Dynamics during Deglaciation of the Laurentide Ice Sheet

    NASA Astrophysics Data System (ADS)

    Stokes, C.; Margold, M.; Clark, C.

    2014-12-01

    Ice streams can rapidly drain large sectors of ice sheet interiors. At present, they account for approximately 50% and 90% of the mass loss from Greenland and Antarctica, respectively, but there are concerns over recent increases in ice discharge. This has been linked to atmospheric and oceanic warming, but the longer-term implications for ice sheet deglaciation are less clear. A key question is whether the activity of ice streams is predictably linked to climate-driven ice sheet mass balance, or whether their activity might accelerate deglaciation. To explore this, we analyse ice streaming during deglaciation of the Laurentide Ice Sheet (LIS) from ~18 to ~7 ka. Following a recent mapping inventory, we bracket the timing of >100 ice streams using published ice margin chronologies. At the Last Glacial Maximum (LGM), ice streams formed a drainage network similar to modern ice sheets. Numerous ice streams were located in topographic troughs and likely operated for thousands of years from the LGM. These drained the marine-based sectors of the northern and eastern margins of the ice sheet until ~11 ka and show a degree of spatial self-organisation. Other ice streams operated on much shorter time-scales and turned on and off, perhaps in as little as a few hundred years. These include large ice streams that switched positions over sedimentary bedrock at the western and southern terrestrial margins until ~13 ka. As the LIS retreated onto its low-relief and predominantly crystalline bedrock interior (after ~11 ka), a smaller number of large ice streams operated that were very wide (50-100 km), and have no modern analogue. Overall, the number of ice streams decreased during deglaciation and they drained a smaller proportion of the ice sheet margin: 30% at the LGM (similar to present-day Antarctica), 15% at 12 ka, and 12% at 10 ka. We use simple scaling relationships to estimate the mass loss delivered by ice streams and examine their role during deglaciation.

  18. Ice Flow in the North East Greenland Ice Stream

    NASA Technical Reports Server (NTRS)

    Joughin, Ian; Kwok, Ron; Fahnestock, M.; MacAyeal, Doug

    1999-01-01

    Early observations with ERS-1 SAR image data revealed a large ice stream in North East Greenland (Fahnestock 1993). The ice stream has a number of the characteristics of the more closely studied ice streams in Antarctica, including its large size and gross geometry. The onset of rapid flow close to the ice divide and the evolution of its flow pattern, however, make this ice stream unique. These features can be seen in the balance velocities for the ice stream (Joughin 1997) and its outlets. The ice 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 ice flow in the northeast Greenland ice stream and its outlet glaciers in order to assess their impact on the past, present, and future mass balance of the ice sheet. We will accomplish these goals using a combination of remotely sensed data and ice sheet models. We are using satellite radar interferometry data to produce a complete maps of velocity and topography over the entire ice stream. We are in the process of developing methods to use these data in conjunction with existing ice sheet models similar to those that have been used to improve understanding of the mechanics of flow in Antarctic ice streams.

  19. Determining Greenland Ice Sheet Accumulation Rates from Radar Remote Sensing

    NASA Technical Reports Server (NTRS)

    Jezek, Kenneth C.

    2001-01-01

    An important component of NASA's Program for Arctic Regional Climate Assessment (PARCA) is a mass balance investigation of the Greenland Ice Sheet. The mass balance is calculated by taking the difference between the snow accumulation and the ice discharge of the ice sheet. Uncertainties in this calculation include the snow accumulation rate, which has traditionally been determined by interpolating data from ice core samples taken throughout the ice sheet. The sparse data associated with ice 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.

  20. Glacier Ice Mass Fluctuations and Fault Instability in Tectonically Active Southern Alaska

    NASA Technical Reports Server (NTRS)

    SauberRosenberg, Jeanne M.; Molnia, Bruce F.

    2003-01-01

    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 ice mass changes perturb the tectonic rate of deformation at a variety of temporal and spatial scales. We estimated surface displacements and stresses associated with ice mass 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 ice mass fluctuations, the changes of the solid Earth due to ice loading and unloading are an important aspect of interpreting geodetic results. The ice changes associated with Bering Glacier s most recent surge cycle are large enough to cause discernible surface displacements. Additionally, ice mass 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 ice load may cause an increase in seismic rate in a region close to failure whereas ice loading may inhibit thrust faulting.

  1. Greenland ice sheet surface temperature, melt and mass loss: 2000-06

    USGS Publications Warehouse

    Hall, D.K.; Williams, R.S., Jr.; Luthcke, S.B.; DiGirolamo, N.E.

    2008-01-01

    A daily time series of 'clear-sky' surface temperature has been compiled of the Greenland ice sheet (GIS) using 1 km resolution moderate-resolution imaging spectroradiometer (MODIS) land-surface temperature (LST) maps from 2000 to 2006. We also used mass-concentration data from the Gravity Recovery and Climate Experiment (GRACE) to study mass 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 ice 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 mass 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 mass loss. This indicates that surface meltwater is flowing rapidly to the base of the ice sheet, causing acceleration of outlet glaciers, thus highlighting the metastability of parts of the GIS and the vulnerability of the ice sheet to air-temperature increases. If air temperatures continue to rise over Greenland, increased surface melt will play a large role in ice-sheet mass loss.

  2. How many stakes are required to measure the mass balance of a glacier?

    USGS Publications Warehouse

    Fountain, A.G.; Vecchia, A.

    1999-01-01

    Glacier mass balance is estimated for South Cascade Glacier and Maclure Glacier using a one-dimensional regression of mass balance with altitude as an alternative to the traditional approach of contouring mass balance 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 mass balance values equivalent to contouring methods. The effect of the number of mass balance 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 mass balance with altitude of alpine glaciers compared to transverse variations. The number of mass balance measurements required to determine the glacier balance appears to be scale invariant for small glaciers and five to ten stakes are sufficient.

  3. Evaluation of the CMIP5 models in the aim of regional modelling of the Antarctic surface mass balance

    NASA Astrophysics Data System (ADS)

    Agosta, C.; Fettweis, X.; Datta, R.

    2015-06-01

    The Antarctic surface mass balance (SMB) cannot be reliably deduced from global climate models (GCMs), both because their spatial resolution is insufficient and because their physics are not adapted for cold and snow-covered regions. By contrast, regional climate models (RCMs) adapted for polar regions can physically and dynamically downscale surface mass balance components over the ice-sheet using large scale forcing at their boundaries. Polar-oriented RCMs require appropriate GCM fields for forcing because the response of the cryosphere to a warming climate is dependent on its initial state and is not linear with respect to temperature increase. In this context, we evaluate current climate in 41 climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) dataset over Antarctica by focusing on forcing fields which may have the greatest impact on SMB components simulated by RCMs. Our inter-comparison includes 5 reanalyses, among which ERA-Interim reanalysis is chosen as a reference over 1979-2014. Model efficiency is assessed taking into account the multi-decadal variability of the fields over the 1850-1980 period. We show that less than 10 CMIP5 models show reasonable biases compared to ERA-Interim, among which ACCESS1-3 seems to be the most pertinent choice for regional climate modeling over Antarctica, followed by CMCC-CM, MIROC-ESM/MIROC-ESM-CHEM and NorESM1-M. Finally, climate change over the Southern Ocean is much more dependent on the initial state of winter sea-ice extent and on the local feedback between air temperature increase and winter sea-ice extent decrease than on the global warming signal.

  4. Bias in GRACE estimates of ice mass change due to accompanying sea-level change

    NASA Astrophysics Data System (ADS)

    Sterenborg, M. G.; Morrow, E.; Mitrovica, J. X.

    2013-04-01

    Observations of spatio-temporal variations in the geopotential using the GRACE satellites have been used to estimate recent mass fluxes from polar ice sheets and glaciers. However, these estimates have not considered the potential bias associated with the migration of water that accompanies the ice melt. This migration is driven by the diminished gravitational attraction of the melting ice reservoir, and this migration, as well as the crustal loading it induces, will contribute to the observed geopotential anomaly. The extent to which this contribution contaminates the ice mass flux estimates depends on how far the smoothing filters applied to the GRACE data extend beyond the ice margins into the ocean. Using the Antarctic Peninsula as a case study, we estimate the magnitude of this bias for a range of melt areas and Gaussian smoothing filter radii. We conclude that GRACE estimates of ice mass loss over the Antarctic Peninsula are systematically overestimating the loss by up to 10 % for filter radii of less than 500 km.

  5. Ice Mass Changes in the Russian High Arctic from Repeat High Resolution Topography.

    NASA Astrophysics Data System (ADS)

    Willis, Michael; Zheng, Whyjay; Pritchard, Matthew; Melkonian, Andrew; Morin, Paul; Porter, Claire; Howat, Ian; Noh, Myoung-Jong; Jeong, Seongsu

    2016-04-01

    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 ice 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 ice shelves. Severnaya Zemlya is also thinning in a complicated manner. A very rapid surging glacier is transferring mass into the ocean from the western periphery of the Vavilov Ice Cap on October Revolution Island, while glaciers feeding the former Matusevich Ice 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 ice dynamic changes will drive mass loss for the immediate future. The sub-marine basins beneath several of the ice caps in the region suggest the possibility that mass loss rates may accelerate in the future.

  6. Greenland Ice Sheet seasonal and spatial mass variability from model simulations and GRACE (2003-2012)

    NASA Astrophysics Data System (ADS)

    Alexander, P. M.; Tedesco, M.; Schlegel, N.-J.; Luthcke, S. B.; Fettweis, X.; Larour, E.

    2015-11-01

    Improving the ability of regional climate models (RCMs) and ice sheet models (ISMs) to simulate spatiotemporal variations in the mass of the Greenland Ice Sheet (GrIS) is crucial for prediction of future sea level rise. While several studies have examined recent trends in GrIS mass loss, studies focusing on mass variations at sub-annual and sub-basin-wide scales are still lacking. Here, we examine spatiotemporal variations in mass over the GrIS derived from the Gravity Recovery and Climate Experiment (GRACE) satellites for the 2003-2012 period using a "mascon" approach, with a nominal spatial resolution of 100 km, and a temporal resolution of 10 days. We compare GRACE-estimated mass variations against those simulated by the Modèle Atmosphérique Régionale (MAR) RCM and the Ice Sheet System Model (ISSM). In order to properly compare spatial and temporal variations in GrIS mass from GRACE with model outputs, we find it necessary to spatially and temporally filter model results to reproduce leakage of mass inherent in the GRACE solution. Both modeled and satellite-derived results point to a decline (of -179 and -240 Gt yr-1 respectively) in GrIS mass over the period examined, but the models appear to underestimate the rate of mass loss, especially in areas below 2000 m in elevation, where the majority of recent GrIS mass loss is occurring. On an ice-sheet wide scale, the timing of the modeled seasonal cycle of cumulative mass (driven by summer mass loss) agrees with the GRACE-derived seasonal cycle, within limits of uncertainty from the GRACE solution. However, on sub-ice-sheet-wide scales, there are significant differences in the timing of peaks in the annual cycle of mass change. At these scales, model biases, or unaccounted-for processes related to ice dynamics or hydrology may lead to the observed differences. This highlights the need for further evaluation of modelled processes at regional and seasonal scales, and further study of ice sheet processes not

  7. Surface mass balance reanalysis of Taku and Lemon Creek glaciers, Alaska: 1946-2015

    NASA Astrophysics Data System (ADS)

    McNeil, Christopher

    We reanalyzed geodetic and glaciological surface mass balance records of Taku and Lemon Creek glaciers for the period 1946--2015 to determine what has driven the contradictory behavior of these glaciers. During the past century, Taku Glacier has been increasing in area and mass, while Lemon Creek Glacier has simultaneously shrunk in area and mass. Between 1948 and 1999 geodetic mass balance rates are +0.33+/-0.34 m w.e. a--1 for Taku Glacier and 0.61+/-0.34 m w.e. a--1 for Lemon Creek Glacier. Geodetic mass balance rates decreased to +0.01+/-0.23 m w.e. a--1 and --0.65 +/-0.23 m w.e. a--1 for Taku and Lemon Creek glaciers respectively, between 1999 and 2013. We updated the glaciological analysis of annual field data, and found no significant difference between updated and previous annual mass balance solutions (p--value < 0.001). We used the geodetic mass balance to calibrate annual glaciological estimates between 1946 and 2015, removing systematic biases of +0.06 m w.e. a--1 from the Taku Glacier record and --0.06 m w.e. a --1 from the Lemon Creek Glacier record. Comparing mass balance anomalies we determined inter--annual variability of surface mass balance is the same for Taku and Lemon Creek glaciers. However, differences in glacier specific hypsometry and mass balance profile drive systematic differences in both annual and long--term glacier mass balance rates.

  8. Sharply increased mass loss from glaciers and ice caps in the Canadian Arctic Archipelago.

    PubMed

    Gardner, Alex S; Moholdt, Geir; Wouters, Bert; Wolken, Gabriel J; Burgess, David O; Sharp, Martin J; Cogley, J Graham; Braun, Carsten; Labine, Claude

    2011-05-19

    Mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond. The Canadian Arctic Archipelago, located off the northwestern shore of Greenland, contains one-third of the global volume of land ice outside the ice sheets, but its contribution to sea-level change remains largely unknown. Here we show that the Canadian Arctic Archipelago has recently lost 61 ± 7 gigatonnes per year (Gt yr(-1)) of ice, contributing 0.17 ± 0.02 mm yr(-1) to sea-level rise. Our estimates are of regional mass changes for the ice caps and glaciers of the Canadian Arctic Archipelago referring to the years 2004 to 2009 and are based on three independent approaches: surface mass-budget modelling plus an estimate of ice discharge (SMB+D), repeat satellite laser altimetry (ICESat) and repeat satellite gravimetry (GRACE). All three approaches show consistent and large mass-loss estimates. Between the periods 2004-2006 and 2007-2009, the rate of mass loss sharply increased from 31 ± 8 Gt yr(-1) to 92 ± 12 Gt yr(-1) in direct response to warmer summer temperatures, to which rates of ice loss are highly sensitive (64 ± 14 Gt yr(-1) per 1 K increase). The duration of the study is too short to establish a long-term trend, but for 2007-2009, the increase in the rate of mass loss makes the Canadian Arctic Archipelago the single largest contributor to eustatic sea-level rise outside Greenland and Antarctica. PMID:21508960

  9. Modeling the mass balance of the Wolverine Glacier Alaska USA using the PTAA model

    NASA Astrophysics Data System (ADS)

    Korn, D.

    2010-12-01

    Glaciers in Alaska have been increasingly losing mass over the last several decades. This trend is especially apparent in South-Central Alaska where many glaciers are undergoing rapid changes and contributing substantially to rising sea levels (Arendt et al., 2002). It is important to understand the rates at which these glaciers are losing mass as well as the important climatic drivers to better prepare for what the future holds in this region and the rest of the world. This work compares glacier mass balance data modeled through the Precipitation-Temperature Area Altitude (PTAA) mass balance model for the Wolverine Glacier in the Kenai Peninsula in South-Central Alaska to observed data from the USGS “benchmark” glacier program in order to help validate the model. The mass balance data are also correlated with climate data in order to understand the main climatic drivers of the glacier mass balance in this region.

  10. Comparative glacio-climatological analysis of mass balance variability along the geographical margin of Europe

    NASA Astrophysics Data System (ADS)

    Lehoczky, Annamária; Kern, Zoltán; Pongrácz, Rita

    2014-05-01

    Glacio-climatological studies recognise glacier mass balance 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 mass balance using records from three border regions of Europe, and investigates the relationships between the seasonal mass balance 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 mass balance 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 mass balance 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 mass balance 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 mass balance of glaciers within a region often co-vary, our specific objectives are (i) to examine the variability and the

  11. Volume and mass changes of the Greenland ice sheet inferred from ICESat and GRACE

    NASA Astrophysics Data System (ADS)

    Ewert, H.; Groh, A.; Dietrich, R.

    2012-09-01

    This study examines the recent evolution of the Greenland ice sheet and its six major drainage basins. Based on laser altimetry data acquired by the Ice, Cloud and Land Elevation Satellite (ICESat), covering the period September-November 2003 to February-March 2008, ice surface height changes and their temporal variations were inferred. Our refined repeat track analysis is solely based on ICESat data and is independent of external elevation models, since it accounts for both ice height changes and the local topography. From the high resolution ice height change pattern we infer an overall mean surface height trend of -0.12 ± 0.006 m yr-1. Furthermore, the largest changes could be identified at coastal margins of the ice sheet, exhibiting rates of more than -2 m yr-1. The total ice volume change of the entire ice sheet amounts to -205.4 ± 10.6 km3 yr-1. In addition, we assessed mass changes from 78 monthly Gravity Recovery and Climate Experiment (GRACE) solutions. The Release-04 gravity field solutions of GeoForschungsZentrum Potsdam cover the period between August 2002 and June 2009. We applied an adjusted regional integration approach in order to minimize the leakage effects. Attention was paid to an optimized filtering which reduces error effects from different sources. The overall error assessment accounts for GRACE errors as well as for errors due to imperfect model reductions. In particular, errors caused by uncertainties in the glacial isostatic adjustment models could be identified as the largest source of errors. Finally, we determined both seasonal and long-term mass change rates. The latter amounts to an overall ice mass change of -191.2 ± 20.9 Gt yr-1 corresponding to 0.53 ± 0.06 mm yr-1 equivalent eustatic sea level rise. From the combination of the volume and mass change estimates we determined a mean density of the lost mass to be 930 ± 11 kg m-3. This value supports our applied density assumption 900 ± 30 kg m-3 which was used to perform the

  12. Atmospheric summer teleconnections and Greenland Ice Sheet surface mass variations: insights from MERRA-2

    NASA Astrophysics Data System (ADS)

    Lim, Young-Kwon; Schubert, Siegfried D.; Nowicki, Sophie M. J.; Lee, Jae N.; Molod, Andrea M.; Cullather, Richard I.; Zhao, Bin; Velicogna, Isabella

    2016-02-01

    The relationship between leading atmospheric teleconnection patterns and Greenland Ice Sheet (GrIS) temperature, precipitation, and surface mass balance (SMB) are investigated for the last 36 summers (1979-2014) based on Modern-Era Retrospective analysis for Research and Applications version 2 reanalyses. The results indicate that the negative phase of both the North Atlantic Oscillation (NAO) and Arctic Oscillation, associated with warm and dry conditions for the GrIS, lead to SMB decreases within 0-1 months. Furthermore, the positive phase of the East Atlantic (EA) pattern often lags the negative NAO, reflecting a dynamical linkage between these modes that acts to further enhance the warm and dry conditions over the GrIS, leading to a favorable environment for enhanced surface mass loss. The development of a strong negative NAO in combination with a strong positive EA in recent years leads to significantly larger GrIS warming compared to when the negative NAO occurs in combination with a negative or weak positive EA (0.69 K versus 0.13 K anomaly). During 2009 and 2011, weakened (as compared to conditions during the severe surface melt cases of 2010 and 2012) local high pressure blocking produced colder northerly flow over the GrIS inhibiting warming despite the occurrence of a strong negative NAO, reflecting an important role for the EA during those years. In particular, the EA acts with the NAO to enhance warming in 2010 and 2012, and weaken high pressure blocking in 2009 and 2011. In general, high pressure blocking primarily impacts the western areas of the GrIS via advective temperature increases, while changes in net surface radiative fluxes account for both western and eastern GrIS temperature changes.

  13. Radiolysis of astrophysical ice analogs by energetic ions: the effect of projectile mass and ice temperature.

    PubMed

    Pilling, Sergio; Duarte, Eduardo Seperuelo; Domaracka, Alicja; Rothard, Hermann; Boduch, Philippe; da Silveira, Enio F

    2011-09-21

    An experimental study of the interaction of highly charged, energetic ions (52 MeV (58)Ni(13+) and 15.7 MeV (16)O(5+)) with mixed H(2)O : C(18)O(2) astrophysical ice analogs at two different temperatures is presented. This analysis aims to simulate the chemical and the physicochemical interactions induced by cosmic rays inside dense, cold astrophysical environments, such as molecular clouds or protostellar clouds as well at the surface of outer solar system bodies. The measurements were performed at the heavy ion accelerator GANIL (Grand Accelerateur National d'Ions Lourds) in Caen, France. The gas samples were deposited onto a CsI substrate at 13 K and 80 K. In situ analysis was performed by a Fourier transform infrared (FTIR) spectrometer at different fluences. Radiolysis yields of the produced species were quantified. The dissociation cross section at 13 K of both H(2)O and CO(2) is about 3-4 times smaller when O ions are employed. The ice temperature seems to affect differently each species when the same projectile was employed. The formation cross section at 13 K of molecules such as C(18)O, CO (with oxygen from water), and H(2)O(2) increases when Ni ions are employed. The formation of organic compounds seems to be enhanced by the oxygen projectiles and at lower temperatures. In addition, because the organic production at 13 K is at least 4 times higher than the value at 80 K, we also expect that interstellar ices are more organic-rich than the surfaces of outer solar system bodies. PMID:21647477

  14. Ice sheet mass loss caused by dust and black carbon accumulation

    NASA Astrophysics Data System (ADS)

    Goelles, T.; Bøggild, C. E.; Greve, R.

    2015-09-01

    Albedo is the dominant factor governing surface melt variability in the ablation area of ice sheets and glaciers. Aerosols such as mineral dust and black carbon (soot) accumulate on the ice surface and cause a darker surface and therefore a lower albedo. The darkening effect on the ice surface is currently not included in sea level projections, and the effect is unknown. We present a model framework which includes ice dynamics, aerosol transport, aerosol accumulation and the darkening effect on ice albedo and its consequences for surface melt. The model is applied to a simplified geometry resembling the conditions of the Greenland ice sheet, and it is forced by several temperature scenarios to quantify the darkening effect of aerosols on future mass loss. The effect of aerosols depends non-linearly on the temperature rise due to the feedback between aerosol accumulation and surface melt. According to our conceptual model, accounting for black carbon and dust in future projections of ice sheet changes until the year 3000 could induce an additional volume loss of 7 %. Since we have ignored some feedback processes, the impact might be even larger.

  15. Climatic impact of glacial cycle polar motion: Coupled oscillations of ice sheet mass and rotation pole position

    USGS Publications Warehouse

    Bills, Bruce G.; James, Thomas S.; Mengel, John G.

    1999-01-01

    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 ice sheets perturb the symmetry of the global mass 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 balance, 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 ice sheet growth. We also explore the evolution of the coupled system composed of ice sheet mass and pole position. Oscillatory solutions result from the conflicting constraints of rotational and thermal stability. A positive mass 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

  16. Annual and seasonal mass balances of Chhota Shigri Glacier (benchmark glacier, Western Himalaya), India

    NASA Astrophysics Data System (ADS)

    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

    2015-04-01

    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 mass balances have been measured continuously since 2002 using the glaciological method, seasonal scale observations began in 2009. The annual and seasonal mass balances were then analyzed along with meteorological conditions in order to understand the role of winter and summer balances on annual glacier-wide mass balance of Chhota Shigri glacier. During the period 2002-2013, the glacier experienced a negative glacier-wide mass balance of -0.59±0.40 m w.e. a-1 with a cumulative glaciological mass balance of -6.45 m w.e. Annual glacier-wide mass balances were negative except for four years (2004/05, 2008/09, 2009/10 and 2010/11) where it was generally close to balanced 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 mass balance, ELA and AAR data between 2002 and 2013. The winter glacier-wide mass balance 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 mass balance 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 mass balance 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

  17. Mass-Balance Fluctuations of Glaciers in the Pacific Northwest and Alaska, USA

    NASA Astrophysics Data System (ADS)

    Josberger, E. G.; Bidlake, W. R.; March, R. S.; Kennedy, B. W.

    2006-12-01

    The mass balance of mid-latitude glaciers of the Pacific Northwest and southern Alaska fluctuates in response to changes in the regional and global atmospheric climate. More than 40 years of net and seasonal mass balance records by the U.S. Geological Survey for South Cascade Glacier, Washington, and Wolverine and Gulkana Glaciers, Alaska, show annual and inter-annual fluctuations that reflect the controlling climatic conditions. South Cascade and Wolverine Glaciers are strongly affected by the warm and wet maritime climate of the Northeast Pacific Ocean, and the winter balances are strongly related to the Pacific Decadal Oscillations (PDO). Gulkana Glacier is more isolated from maritime influences and the net balance variation is more closely linked to the summer balance. By the late 1970's, mass-balance records for the three were long enough to reflect the 1976-77 shift in PDO from negative to positive. Both maritime glaciers responded, with net balance of South Cascade Glacier becoming consistently negative and that of Wolverine Glacier becoming predominantly positive. The overall trend of negative mass balance continued through 2004 for South Cascade Glacier, where the 1977 to 2004 cumulative net balance was about -22 meters water equivalent (mweq). After a gain of about 7 mweq, the trend of positive net balance for Wolverine Glacier ended in 1989. Beginning in 1989, the net balance trend for Wolverine Glacier became predominantly negative and the cumulative net balance for 1989 to 2004 was about -14 mweq. Net balance of Gulkana Glacier did not respond appreciably to the 1976-77 PDO shift. The cumulative net balance for Gulkana Glacier from the beginning of the record (1966) through 1988 was about -3 mweq. The major change in trend of mass balance occurred in 1989, when net balance became almost exclusively negative. The cumulative net balance during 1989 through 2004 was about 13 mweq. As a result trends in net balance had become strongly negative for more

  18. Ice hockey lung - a case of mass nitrogen dioxide poisoning in the Czech Republic.

    PubMed

    Brat, Kristian; Merta, Zdenek; Plutinsky, Marek; Skrickova, Jana; Stanek, Miroslav

    2013-01-01

    Nitrogen dioxide (NO₂) is a toxic gas, a product of combustion in malfunctioning ice-resurfacing machines. NO₂ poisoning is rare but potentially lethal. The authors report a case of mass NO₂ poisoning involving 15 amateur ice hockey players in the Czech Republic. All players were treated in the Department of Respiratory Diseases at Brno University Hospital in November 2010 - three as inpatients because they developed pneumonitis. All patients were followed-up until November 2011. Complete recovery in all but one patient was achieved by December 2010. None of the 15 patients developed asthma-like disease or chronic cough. Corticosteroids appeared to be useful in treatment. Electric-powered ice-resurfacing machines are preferable in indoor ice skating arenas. PMID:24032121

  19. Ice hockey lung – a case of mass nitrogen dioxide poisoning in the Czech Republic

    PubMed Central

    Brat, Kristian; Merta, Zdenek; Plutinsky, Marek; Skrickova, Jana; Ing, Miroslav Stanek

    2013-01-01

    Nitrogen dioxide (NO2) is a toxic gas, a product of combustion in malfunctioning ice-resurfacing machines. NO2 poisoning is rare but potentially lethal. The authors report a case of mass NO2 poisoning involving 15 amateur ice hockey players in the Czech Republic. All players were treated in the Department of Respiratory Diseases at Brno University Hospital in November 2010 – three as inpatients because they developed pneumonitis. All patients were followed-up until November 2011. Complete recovery in all but one patient was achieved by December 2010. None of the 15 patients developed asthma-like disease or chronic cough. Corticosteroids appeared to be useful in treatment. Electric-powered ice-resurfacing machines are preferable in indoor ice skating arenas. PMID:24032121

  20. Re-establishing seasonal mass balance observation at Abramov Glacier, Kyrgyzstan, from 1968 - 2012

    NASA Astrophysics Data System (ADS)

    Barandun, Martina; Huss, Matthias; Azisov, Erlan; Gafurov, Abror; Hoelzle, Martin; Merkushkin, Aleksandr; Salzmann, Nadine; Usubaliev, Ryskul

    2013-04-01

    The Abramov Glacier, located in the Pamir Alay in Kyrgyzstan, was subject to intense studies in the frame of various scientific programs under the former USSR. With the breakdown of the Soviet Union, the monitoring was abruptly abandoned in the late nineties. Well documented and continuous seasonal mass balance observations are available for 1968-1994. However, some inconsistencies between different publications lead to in-homogeneous data sets. Recently, the project CATCOS (Capacity Building and Twinning for Climate Observing Systems) was launched, aiming among other goals to re-establish mass balance observation on selected glaciers in Kyrgyzstan. At Abramov Glacier, a new stake network, an automatic weather station (AWS) and two automatic terrestrial cameras with instantaneous data transfer over satellite were installed in 2011. Measurements were repeated and intensified in 2012 and will be subject of a third field campaign in summer 2013. A complete re-analysis of the long-term mass balance series from 1968 to 1994 delivers corrected mass balance data for Abramov Glacier. To homogenize in-situ mass balance records, a spatially distributed mass balance model driven with local daily temperature and precipitation data was calibrated to each seasonal mass balance survey. The model resolves seasonal mass-balance measurements to a daily timescale and performs spatial inter- and extrapolation of data points based on a consistent algorithm, taking into account the principal factors of mass balance distribution. Summarizing the annually optimized parameters over the entire study period provides a robust model parameter set for years with less extensive direct measurements. From 1994 to 2011, neither direct point measurements nor meteorological data are available. In order to run the calibrated model developed for the 1960's to 90's, climate input variables were taken from bias corrected Re-analysis data (NCEP/NCAR and JRA). Evaluation of the model results was achieved

  1. Changes in ice dynamics, elevation and mass discharge of Dinsmoor-Bombardier-Edgeworth glacier system, Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Seehaus, Thorsten; Marinsek, Sebastián; Helm, Veit; Skvarca, Pedro; Braun, Matthias

    2015-10-01

    The northern Antarctic Peninsula is one of the fastest changing regions on Earth. The disintegration of the Larsen-A Ice Shelf in 1995 caused tributary glaciers to adjust by speeding up, surface lowering, and overall increased ice-mass discharge. In this study, we investigate the temporal variation of these changes at the Dinsmoor-Bombardier-Edgeworth glacier system by analyzing dense time series from various spaceborne and airborne Earth observation missions. Precollapse ice shelf conditions and subsequent adjustments through 2014 were covered. Our results show a response of the glacier system some months after the breakup, reaching maximum surface velocities at the glacier front of up to 8.8 m/d in 1999 and a subsequent decrease to ∼1.5 m/d in 2014. Using a dense time series of interferometrically derived TanDEM-X digital elevation models and photogrammetric data, an exponential function was fitted for the decrease in surface elevation. Elevation changes in areas below 1000 m a.s.l. amounted to at least 130 ± 15 m between 1995 and 2014, with change rates of ∼3.15 m/a between 2003 and 2008. Current change rates (2010-2014) are in the range of 1.7 m/a. Mass imbalances were computed with different scenarios of boundary conditions. The most plausible results amount to - 40.7 ± 3.9 Gt. The contribution to sea level rise was estimated to be 18.8 ± 1.8 Gt, corresponding to a 0.052 ± 0.005 mm sea level equivalent, for the period 1995-2014. Our analysis and scenario considerations revealed that major uncertainties still exist due to insufficiently accurate ice-thickness information. The second largest uncertainty in the computations was the glacier surface mass balance, which is still poorly known. Our time series analysis facilitates an improved comparison with GRACE data and as input to modeling of glacio-isostatic uplift in this region. The study contributed to a better understanding of how glacier systems adjust to ice shelf disintegration.

  2. Laser desorption time-of-flight mass spectrometry of ultraviolet photo-processed ices

    SciTech Connect

    Paardekooper, D. M. Bossa, J.-B.; Isokoski, K.; Linnartz, H.

    2014-10-01

    A new ultra-high vacuum experiment is described that allows studying photo-induced chemical processes in interstellar ice analogues. MATRI²CES - a Mass Analytical Tool to study Reactions in Interstellar ICES applies a new concept by combining laser desorption and time-of-flight mass spectrometry with the ultimate goal to characterize in situ and in real time the solid state evolution of organic compounds upon UV photolysis for astronomically relevant ice mixtures and temperatures. The performance of the experimental setup is demonstrated by the kinetic analysis of the different photoproducts of pure methane (CH₄) ice at 20 K. A quantitative approach provides formation yields of several new species with up to four carbon atoms. Convincing evidence is found for the formation of even larger species. Typical mass resolutions obtained range from M/ΔM ~320 to ~400 for CH₄ and argon, respectively. Additional tests show that the typical detection limit (in monolayers) is ⩽0.02 ML, substantially more sensitive than the regular techniques used to investigate chemical processes in interstellar ices.

  3. Volume and mass changes of the Greenland ice sheet inferred from ICESat and GRACE

    NASA Astrophysics Data System (ADS)

    Groh, A.; Ewert, H.; Dietrich, R. O.

    2011-12-01

    The present study utilizes laser altimetry data acquired by the Ice, Cloud and Land Elevation Satellite (ICESat) and monthly Gravity Recovery and Climate Experiment (GRACE) solutions to investigate the recent evolution of the Greenland ice sheet and its six major drainage basins. Ice surface height changes were derived from a refined repeat track analysis of ICESat altimetry data for the period September-November 2003 to February-March 2008. This analysis is independent of any external data source like a digital elevation model. The Release-04 gravity field solutions of GeoForschungsZentrum Potsdam were used to infer long-term ice mass changes and cover the period between August 2002 and June 2009. Special attention was paid to an optimized filtering in order to reduce error effects from different sources. The presented error estimates account for GRACE errors as well as for errors due to imperfect reduction models. For a direct comparison of both observational results the ICESat-derived volume changes were converted into mass changes. The applied density assumption of the ongoing mass change is supported by the estimate from the combination of the observed mass and volume changes. Finally it could be demonstrated that the mass change estimates from both observation techniques are generally in good agreement.

  4. Global application of a surface mass balance model using gridded climate data

    NASA Astrophysics Data System (ADS)

    Giesen, R. H.; Oerlemans, J.

    2012-04-01

    Global applications of surface mass balance models have large uncertainties, as a result of poor climate input data and limited availability of mass balance measurements. This study addresses several possible consequences of these limitations for the modelled mass balance. This is done by applying a simple surface mass balance model that only requires air temperature and precipitation as input data, to glaciers in different regions. In contrast to other models used in global applications, this model separately calculates the contributions of net solar radiation and the temperature-dependent fluxes to the energy balance. We derive a relation for these temperature-dependent fluxes using automatic weather station (AWS) measurements from glaciers in different climates. With local, hourly input data, the model is well able to simulate the observed seasonal variations in the surface energy and mass balance at the AWS sites. Replacing the hourly local data by monthly gridded climate data removes summer snowfall and winter melt events and hence influences the modelled mass balance most on locations with a small seasonal temperature cycle. Representative values for the multiplication factor and vertical gradient of precipitation are determined by fitting modelled winter mass balance profiles to observations on 80 glaciers in different regions. For 72 of the 80 glaciers, the precipitation provided by the climate data set has to be multiplied with a factor above unity; the median factor is 2.55. The vertical precipitation gradient ranges from negative to positive values, with more positive values for maritime glaciers and a median value of 1.5 mm a-1 m. With calibrated precipitation, the modelled annual mass balance gradient closely resembles the observations on the 80 glaciers, the absolute values are matched by adjusting either the incoming solar radiation, the temperature-dependent flux or the air temperature. The mass balance sensitivity to changes in temperature is

  5. Calibration of a surface mass balance model for global-scale applications

    NASA Astrophysics Data System (ADS)

    Giesen, R. H.; Oerlemans, J.

    2012-12-01

    Global applications of surface mass balance models have large uncertainties, as a result of poor climate input data and limited availability of mass balance measurements. This study addresses several possible consequences of these limitations for the modelled mass balance. This is done by applying a simple surface mass balance model that only requires air temperature and precipitation as input data, to glaciers in different regions. In contrast to other models used in global applications, this model separately calculates the contributions of net solar radiation and the temperature-dependent fluxes to the energy balance. We derive a relation for these temperature-dependent fluxes using automatic weather station (AWS) measurements from glaciers in different climates. With local, hourly input data, the model is well able to simulate the observed seasonal variations in the surface energy and mass balance at the AWS sites. Replacing the hourly local data by monthly gridded climate data removes summer snowfall and winter melt events and, hence, influences the modelled mass balance most on locations with a small seasonal temperature cycle. Modelled winter mass balance profiles are fitted to observations on 82 glaciers in different regions to determine representative values for the multiplication factor and vertical gradient of precipitation. For 75 of the 82 glaciers, the precipitation provided by the climate dataset has to be multiplied with a factor above unity; the median factor is 2.5. The vertical precipitation gradient ranges from negative to positive values, with more positive values for maritime glaciers and a median value of 1.5 mm a-1 m-1. With calibrated precipitation, the modelled annual mass balance gradient closely resembles the observations on the 82 glaciers, the absolute values are matched by adjusting either the incoming solar radiation, the temperature-dependent flux or the air temperature. The mass balance sensitivity to changes in temperature is

  6. Insights into Spatial Sensitivities of Ice Mass Response to Environmental Change from the SeaRISE Ice Sheet Modeling Project I: Antarctica

    NASA Technical Reports Server (NTRS)

    Nowicki, Sophie; Bindschadler, Robert A.; Abe-Ouchi, Ayako; Aschwanden, Andy; Bueler, Ed; Choi, Hyengu; Fastook, Jim; Granzow, Glen; Greve, Ralf; Gutowski, Gail; Herzfeld, Ute; Jacskon, Charles; Johnson, Jesse; Khroulev, Constantine; Larour, Eric; Levermann, Anders; Lipscomb, William H.; Martin, Maria A.; Morlighem, Mathieu; Parizek, Byron R; Pollard, David; Price, Stephen F.; Seroussi, Helene; Walker, Ryan; Wang, Wei Li

    2013-01-01

    Atmospheric, oceanic, and subglacial forcing scenarios from the Sea-level Response to Ice Sheet Evolution (SeaRISE) project are applied to six three-dimensional thermomechanical ice-sheet models to assess Antarctic ice 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) mass loss with enhanced sliding (with basins dominated by high driving stresses affected more than basins with low-surface-slope streaming ice); and (iii) mass loss with enhanced ice shelf melting (with changes in West Antarctica dominating the signal due to its marine setting and extensive ice shelves; cf. minimal impact in the Terre Adelie, George V, Oates, and Victoria Land region of East Antarctica). Ice 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 ice dynamics highlight the need for improved understanding of basal conditions, grounding-zone processes, ocean-ice interactions, and the numerical representation of all three.

  7. Application and validation of long-range terrestrial laser scanning to monitor the mass balance of very small glaciers in the Swiss Alps

    NASA Astrophysics Data System (ADS)

    Fischer, Mauro; Huss, Matthias; Kummert, Mario; Hoelzle, Martin

    2016-06-01

    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 mass balance, 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 mass balances 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 mass 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 ice-covered terrain. Zonally variable conversion factors for firn and bare ice surfaces were applied to convert geodetic volume to mass changes. We compare the geodetic results to direct glaciological mass balance measurements coinciding with the TLS surveys and assess the uncertainties and errors included in both methods. Average glacier-wide mass balances were negative in both years, showing stronger mass losses in 2014/15 (-1.65 m w.e.) compared to 2013/14 (-0.59 m w.e.). Geodetic mass balances 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 mass balances 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 mass

  8. BALANCE

    DOEpatents

    Carmichael, H.

    1953-01-01

    A torsional-type analytical balance designed to arrive at its equilibrium point more quickly than previous balances is described. In order to prevent external heat sources creating air currents inside the balance casing that would reiard the attainment of equilibrium conditions, a relatively thick casing shaped as an inverted U is placed over the load support arms and the balance beam. This casing is of a metal of good thernnal conductivity characteristics, such as copper or aluminum, in order that heat applied to one portion of the balance is quickly conducted to all other sensitive areas, thus effectively preventing the fornnation of air currents caused by unequal heating of the balance.

  9. Warm-air advection, air mass transformation and fog causes rapid ice melt

    NASA Astrophysics Data System (ADS)

    Tjernström, Michael; Shupe, Matthew D.; Brooks, Ian M.; Persson, P. Ola G.; Prytherch, John; Salisbury, Dominic J.; Sedlar, Joseph; Achtert, Peggy; Brooks, Barbara J.; Johnston, Paul E.; Sotiropoulou, Georgia; Wolfe, Dan

    2015-07-01

    Direct observations during intense warm-air advection over the East Siberian Sea reveal a period of rapid sea-ice melt. A semistationary, high-pressure system north of the Bering Strait forced northward advection of warm, moist air from the continent. Air-mass transformation over melting sea ice formed a strong, surface-based temperature inversion in which dense fog formed. This induced a positive net longwave radiation at the surface while reducing net solar radiation only marginally; the inversion also resulted in downward turbulent heat flux. The sum of these processes enhanced the surface energy flux by an average of ~15 W m-2 for a week. Satellite images before and after the episode show sea-ice concentrations decreasing from > 90% to ~50% over a large area affected by the air-mass transformation. We argue that this rapid melt was triggered by the increased heat flux from the atmosphere due to the warm-air advection.

  10. Mass-balance approach for assessing nitrate flux intidal wetlands -- lessons learned

    EPA Science Inventory

    Field experiments were carried out in 2010 and 2011 to assess the nitrate balance in a small tidal slough located in the Yaquina Estuary, Oregon. In 2010 we used a whole-slough, mass-balance approach, while a smaller scale, flume-like experiment in a tidal channel with a dense ...

  11. Spent Nuclear Fuel (SNF) Project Multi Canister Overpack (MCO) Process Flow Diagram Mass Balance Calculations

    SciTech Connect

    KLEM, M.J.

    2000-09-08

    The purpose of this calculation document is to develop the bases for the material balances of the Multi-Canister Overpack (MCO) Level 1 Process Flow Diagram (PFD). The attached mass balances support revision two of the PFD for the MCO and provide future reference.

  12. Spent Nuclear Fuel (SNF) Project Canister Storage Building (CSB) Process Flow Diagram Mass Balance Calculations

    SciTech Connect

    KLEM, M.J.

    2000-05-11

    The purpose of these calculations is to develop the material balances for documentation of the Canister Storage Building (CSB) Process Flow Diagram (PFD) and future reference. The attached mass balances were prepared to support revision two of the PFD for the CSB. The calculations refer to diagram H-2-825869.

  13. Composition of Meridiani Hematite-rich Spherules: A Mass-Balance Mixing-Model Approach

    NASA Astrophysics Data System (ADS)

    Jolliff, B. L.; Athena Science Team

    2005-03-01

    A mass-balance model using APXS data and microscopic images indicates that the composition of spherules ("blueberries"), found at the Meridiani site by the Mars Exploration Rover Opportunity and thought to be concretions, contain ~45-60 wt% hematite.

  14. Mercury mass balance in Lake Michigan--the knowns and unknowns

    EPA Science Inventory

    LM2-Mercury, a mercury mass balance model, was developed to simulate and evaluate the transport, fate, and biogeochemical transformations of mercury in Lake Michigan. The model simulates total suspended solids (TSS), disolved organic carbon (DOC), and total, elemental, divalent, ...

  15. A GIS TECHNIQUE FOR ESTIMATING NATURAL ATTENUATION RATES AND MASS BALANCES: JOURNAL ARTICLE

    EPA Science Inventory

    NRMRL-ADA-01308 Durant, ND, Srinivasan, P, Faust, CR, Burnell, DK, Klein, KL, and Burden*, D.S. A GIS Technique for Estimating Natural Attenuation Rates and Mass Balances. Battelle's Sixth International ...

  16. Evaluation of the CMIP5 models in the aim of regional modelling of the Antarctic surface mass balance

    NASA Astrophysics Data System (ADS)

    Agosta, C.; Fettweis, X.; Datta, R.

    2015-12-01

    The surface mass balance (SMB) of the Antarctic Ice Sheet cannot be reliably deduced from global climate models (GCMs), both because their spatial resolution is insufficient and because their physics are not adapted for cold and snow-covered regions. By contrast, regional climate models (RCMs) adapted for polar regions can physically and dynamically downscale SMB components over the ice sheet using large-scale forcing at their boundaries. Polar-oriented RCMs require appropriate GCM fields for forcing because the response of the cryosphere to a warming climate is dependent on its initial state and is not linear with respect to temperature increase. In this context, we evaluate the current climate in 41 climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) data set over Antarctica by focusing on forcing fields which may have the greatest impact on SMB components simulated by RCMs. Our inter-comparison includes six reanalyses, among which ERA-Interim reanalysis is chosen as a reference over 1979-2014. Model efficiency is assessed taking into account the multi-decadal variability of the fields over the 1850-1980 period. We show that fewer than 10 CMIP5 models show reasonable biases compared to ERA-Interim, among which ACCESS1-3 is the most pertinent choice for forcing RCMs over Antarctica, followed by ACCESS1-0, CESM1-BGC, CESM1-CAM5, NorESM1-M, CCSM4 and EC-EARTH. Finally, climate change over the Southern Ocean in CMIP5 is less sensitive to the global warming signal than it is to the present-day simulated sea-ice extent and to the feedback between sea-ice decrease and air temperature increase around Antarctica.

  17. Mass-balance modelling of Chhota Shigri and Patsio glacier in western Himalaya, India

    NASA Astrophysics Data System (ADS)

    Engelhardt, Markus; Kumar, Pankaj; Li, Lu; Ramanathan, Alagappan

    2016-04-01

    Projections of glacier mass-balance evolution in the Himalayas are afflicted with high uncertainty due to the diversity of the climatic conditions and the extremes in topographical relief. Large spatial variations in glacier mass balances are connected with the diverse precipitation patterns. While there are indications of recent glacier retreats in the Himalayas, only few glaciers have been monitored over long periods. In 2002, a long term continuous monitoring programme of glacier mass balance was started on Chhota Shigri glacier (15.7 km²). During the period 2002-2013, measurements show an average glacier-wide mass balance of -0.59±0.12 m w.e. after near zero annual mass balances in the 1990s. On Patsio glacier (2.3 km²) mass-balance studies were initiated in 2010. We apply a mass-balance model for the glaciers Chhota Shigri and Patsio using gridded data from two different regional climate models: 1) the Weather Research and Forecasting (WRF) Model for the period 1970-2005 (on 50 km resolution) and 1996-2005 (on 3 km resolution), and 2) the regional climate model REMO for the period and 1989-2013 (25 km resolution). The data are downscaled from its grid resolution to the glacier grid (300 m). Additional input are daily potential global radiation values, calculated using a digital elevation model (DEM) at a resolution of 30 m and considering slope, aspect and shading of the surrounding topography. The mass-balance model calculates snow accumulation, melt and runoff on a sub-daily (hourly) time scale. Calibration and validation data are the available seasonal and annual mass-balance measurements together with point measurements of temperature, precipitation and radiation. Results show that this region of the Himalayas is situated in the transition zone between areas where the annual glacier mass balance ba is controlled by summer temperature and areas where ba is controlled by winter precipitation. In addition, summer snowfalls are a major influencing factor on

  18. Sea-level feedback lowers projections of future Antarctic Ice-Sheet mass loss.

    PubMed

    Gomez, Natalya; Pollard, David; Holland, David

    2015-01-01

    The stability of marine sectors of the Antarctic Ice 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 ice sheet has a stabilizing influence on the ice sheets, and previous studies have established the importance of this feedback on ice age AIS evolution. Here we use a coupled ice 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 ice-sheet retreat significantly reduces AIS mass 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

  19. Sea-level feedback lowers projections of future Antarctic Ice-Sheet mass loss

    NASA Astrophysics Data System (ADS)

    Gomez, Natalya; Pollard, David; Holland, David

    2015-11-01

    The stability of marine sectors of the Antarctic Ice 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 ice sheet has a stabilizing influence on the ice sheets, and previous studies have established the importance of this feedback on ice age AIS evolution. Here we use a coupled ice 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 ice-sheet retreat significantly reduces AIS mass 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.

  20. Coupled Gravity and Elevation Measurements of Ice Sheet Mass Change

    NASA Technical Reports Server (NTRS)

    Jezek, K. C.

    2005-01-01

    We measured surface gravity and position at ten locations about two glaciological measurement networks located on the South-central Greenland Ice during June 2004. Six of the individual sites of the first network were occupied the previous year. At the repeat sites we were able to measure annual accumulation rate and surface displacement by referencing measurements to aluminum poles left in the firn the previous year. We occupied 4 additional sites at a second measurement network for the first time since initial observations were last made at the network in 1981. At each individual site, we operated a GPS unit for 90 minutes - the unit was operated simultaneously with a base station unit in Sondrestrom Fjord so as to enable differential, post-processing of the data. We installed an aluminum, accumulation-rate-pole at each site. The base section of the pole also served as the mount for the GPS antenna. A new, Scintrex gravimeter was used at each site and relative gravity measurements were tied to the network of absolute gravity stations in Sondrestrom. We measured snow physical properties in two shallow pits. This report summarizes our observations and data analysis.

  1. Low resolution optical remote sensing applied to the monitoring of seasonal glacier mass balance.

    NASA Astrophysics Data System (ADS)

    Drolon, Vanessa; Maisongrande, Philippe; Berthier, Etienne; Swinnen, Else

    2015-04-01

    Mass balance is a key variable to describe the state of health of glaciers, their contribution to sea level rise and, in a few dry regions, their role in water resource. We explore here a new method to retrieve seasonal glacier mass balances from low resolution optical remote sensing. We derive winter and summer snow maps for each year during 1998-2014, using the Normalized Difference Snow Index (NDSI) computed from visible and SWIR channels available with SPOT/VEGETATION. The NDSI dynamic is directly linked to the area percentage of snow in the VGT kilometric pixel. The combination of 15 years of 10-daily NDSI maps with the SRTM DEM allows us to calculate the altitude of the transition between bare soil and snow. Then, we compare the interannual dynamic of this altitude with in situ measurements of mass balance available for 60 alpine glaciers (Huss et al., 2010; Zemp et al., 2009, 2013) and find promising relationships for winter mass balance. We also explore the possibility of a real-time monitoring of winter mass balance for a selection of alpine glaciers. Finally, we discuss the robustness and genericity of these relationships for their future application in regions where in situ glaciers mass balances are scarce or not available.

  2. Mass and thermal energy balance of potato processing operations

    SciTech Connect

    Chadbourne, D.L.; Heldman, D.R.

    1981-01-01

    A mass and thermal energy analysis was conducted for a potato peeling operation. Results provide insight into opportunities for process modifications leading to increased recovery of product components and thermal energy.

  3. Time-variable ice mass redistribution and consequences for solid Earth geodesy

    NASA Astrophysics Data System (ADS)

    Ivins, E. R.; Wu, X.; James, T. S.

    2009-05-01

    Long wavelength gravity changes associated with imbalance of the cryosphere and other interannual and secular processes are now being mapped from space using GRACE (Gravity Recovery and Climate Experiment) mission data. The gravity changes are supplemented by constraints that come from bounds on Earth rotation and the drift between the Earth's center-of-mass and center-of-figure. Although the main features of northern hemispheric post-glacial rebound are clearly recovered from GRACE, there is much to be gained from improving the modeled hydrology and ocean tides. In addition, a great deal of uncertainty exists in the forward ice models that are responsible for driving predictions of the present-day signatures arising from viscoelastic relaxation of the Earth's mantle. There is a link between the uncertainties associated with glacial isostasy and the extraction of present-day ice mass changes in Greenland, the Devon Ice Cap and land ice of Canada's Arctic archipelago from space-borne gravity observations. For example, model gravity changes associated with the long-wavelength components of the collapse of the Laurentide forebulge have far greater uncertainty in the northeastern Canadian Arctic archipelago than south of Hudson Bay. This spatially variable uncertainty can now be quantified with increasing confidence, in part, due to constraints that come from tide gauge and GPS measurements. Here we examine and discuss the implications of uncertainties in the timing and size of ice sheet collapse in eastern Canada and we quantify the errors caused in estimating ice loss in Greenland and the Canadian Arctic. The uncertainty is a sensitive function of ice dome size, location, collapse history, lithospheric thickness and mantle viscosity structure.

  4. Re-analysing eleven years of mass balance observations at Langenferner, Ortler-Cevedale Group, Italy

    NASA Astrophysics Data System (ADS)

    Galos, Stephan; Klug, Christoph; Rieg, Lorenzo; Sauter, Tobias; Gurgiser, Wolfgang; Kaser, Georg

    2016-04-01

    Long term surface mass balance records of glaciers are of peculiar scientific interest as they reflect the most direct link between the observed glacier changes and the underlying atmospheric forcing. Consequently they provide a unique source of information which is used in a wide range of different models (climate-, mass- or energy balance-, sea level rise- or run-off models). However, both inhomogeneities and unknown error ranges in the observational series limit the usefulness of respective datasets. Hence, the homogenization of long term records, as well as the availability of solid error values can significantly improve the quality of data and is therefore of crucial interest to the community. The surface mass balance of Langenferner / Vedretta Lunga, a small valley glacier in the Italian Eastern Alps, has been measured since the hydrological year 2003/04. The resulting series of annual mass balances was homogenized using a process based mass balance model in order to calculate the annual mass balance for points without stake measurements during the first observation years. A detailed error analysis was performed considering all significant sources of uncertainties involved in the mass balance determination applying the direct glaciological method. The homogenized mass balance values differ from the initial series mainly during the first measurement years when the number of measurements in the upper glacier parts was low and consequently large errors in the spatial extrapolation of measurements were made due to a lack of knowledge about changes in the upper glacier part. Hence the largest errors in mass balance calculation at Langenferner / Vedretta Lunga originate from inaccurate spatial extrapolation of point measurements, while other effects such as errors due to surface roughness play a role on the point scale but are canceled out by the high number of measurement points on the glacier wide scale. A comparison of the surface mass balance to the geodetic

  5. Brief Communication: Upper-air relaxation in RACMO2 significantly improves modelled interannual surface mass balance variability in Antarctica

    NASA Astrophysics Data System (ADS)

    van de Berg, Willem Jan; Medley, Brooke

    2016-03-01

    The Regional Atmospheric Climate Model (RACMO2) has been a powerful tool for improving surface mass balance (SMB) estimates from GCMs or reanalyses. However, new yearly SMB observations for West Antarctica show that the modelled interannual variability in SMB is poorly simulated by RACMO2, in contrast to ERA-Interim, which resolves this variability well. In an attempt to remedy RACMO2 performance, we included additional upper-air relaxation (UAR) in RACMO2. With UAR, the correlation to observations is similar for RACMO2 and ERA-Interim. The spatial SMB patterns and ice-sheet-integrated SMB modelled using UAR remain very similar to the estimates of RACMO2 without UAR. We only observe an upstream smoothing of precipitation in regions with very steep topography like the Antarctic Peninsula. We conclude that UAR is a useful improvement for regional climate model simulations, although results in regions with steep topography should be treated with care.

  6. Rapid Ice Mass Loss: Does It Have an Influence on Earthquake Occurrence in Southern Alaska?

    NASA Technical Reports Server (NTRS)

    Sauber, Jeanne M.

    2008-01-01

    The glaciers of southern Alaska are extensive, and many of them have undergone gigatons of ice wastage on time scales on the order of the seismic cycle. Since the ice loss occurs directly above a shallow main thrust zone associated with subduction of the Pacific-Yakutat plate beneath continental Alaska, the region between the Malaspina and Bering Glaciers is an excellent test site for evaluating the importance of recent ice wastage on earthquake faulting potential. We demonstrate the influence of cumulative glacial mass loss following the 1899 Yakataga earthquake (M=8.1) by using a two dimensional finite element model with a simple representation of ice fluctuations to calculate the incremental stresses and change in the fault stability margin (FSM) along the main thrust zone (MTZ) and on the surface. Along the MTZ, our results indicate a decrease in FSM between 1899 and the 1979 St. Elias earthquake (M=7.4) of 0.2 - 1.2 MPa over an 80 km region between the coast and the 1979 aftershock zone; at the surface, the estimated FSM was larger but more localized to the lower reaches of glacial ablation zones. The ice-induced stresses were large enough, in theory, to promote the occurrence of shallow thrust earthquakes. To empirically test the influence of short-term ice fluctuations on fault stability, we compared the seismic rate from a reference background time period (1988-1992) against other time periods (1993-2006) with variable ice or tectonic change characteristics. We found that the frequency of small tectonic events in the Icy Bay region increased in 2002-2006 relative to the background seismic rate. We hypothesize that this was due to a significant increase in the rate of ice wastage in 2002-2006 instead of the M=7.9, 2002 Denali earthquake, located more than 100km away.

  7. Ice stream activity scaled to ice sheet volume during Laurentide Ice Sheet deglaciation.

    PubMed

    Stokes, C R; Margold, M; Clark, C D; Tarasov, L

    2016-02-18

    The contribution of the Greenland and West Antarctic ice sheets to sea level has increased in recent decades, largely owing to the thinning and retreat of outlet glaciers and ice streams. This dynamic loss is a serious concern, with some modelling studies suggesting that the collapse of a major ice 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 ice-sheet scale, it is unclear how the entire drainage network of ice streams evolves over longer timescales. This represents one of the largest sources of uncertainty when predicting the contributions of ice sheets to sea-level rise. A key question is whether ice streams might increase and sustain rates of mass loss over centuries or millennia, beyond those expected for a given ocean-climate forcing. Here we reconstruct the activity of 117 ice streams that operated at various times during deglaciation of the Laurentide Ice 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 ice sheet perimeter and their total discharge decreased. The underlying geology and topography clearly influenced ice stream activity, but--at the ice-sheet scale--their drainage network adjusted and was linked to changes in ice sheet volume. It is unclear whether these findings can be directly translated to modern ice sheets. However, contrary to the view that sees ice streams as unstable entities that can accelerate ice-sheet deglaciation, we conclude that ice streams exerted progressively less influence on ice sheet mass balance during the retreat of the Laurentide Ice Sheet. PMID:26887494

  8. Modeling the surface mass balance and firn evolution of glaciers around Kongsfjorden, Svalbard

    NASA Astrophysics Data System (ADS)

    Kohler, J.; van Pelt, W. J. J.

    2014-12-01

    A coupled modeling approach is applied to simulate the long-term (1961-2012) surface mass balance and subsurface evolution of the Kongsvegen and Holtedahlfonna glacier systems in western Svalbard. Principle aims are: 1) to quantify and analyze the distributed surface mass balance evolution, 2) to estimate the contribution of melt water refreezing and internal accumulation to the mass balance, and 3) to detect changes in firn conditions over the simulation period. In order to achieve this, HIRLAM regional climate model output for 1961-2012 is projected onto the 100-m model grid and serves as input for a coupled model surface energy balance - firn model. Available stake measurements since 1987, together with weather station data and snow profiling observations, are used for parameter estimation, as well as validation of the model results. Extensive spin-up is performed to provide initialized subsurface conditions at the start of the experiments. Results indicate a slightly positive area-averaged surface mass balance of 0.08 m w.e. yr-1, which only fractionally compensates for mass loss by calving. Melt water refreezing (spatial mean 0.30 m w.e. yr-1) provides a strong buffer for mass loss, whereas substantial internal accumulation (up to 0.22 m w.e. yr-1) adds uncertainty to mass balance observations in the accumulation zone. An increasingly negative surface mass balance over the last two decades has led to a retreat of the firn line and a substantial reduction of the firn air content. Together with a negative trend in the albedo and elevated runoff this could mark the onset of accelerated near-future mass loss.

  9. Glacier mass-balance fluctuations in the Pacific Northwest and Alaska, USA

    NASA Astrophysics Data System (ADS)

    Josberger, Edward G.; Bidlake, William R.; March, Rod S.; Kennedy, Ben W.

    2007-10-01

    The more than 40 year record of net and seasonal mass-balance 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 mass-balance record grows in length, it is revealing significant changes in previously described glacier mass-balance 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 balances 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 balance of the two maritime glaciers, with a weakening of the correlation between the winter balance fluctuations and the PDO. Non-synchronous periods of positive and negative net balance for each glacier prior to 1989 were followed by a 1989-2004 period of synchronous and almost exclusively negative net balances that averaged -0.8 m for the three glaciers.

  10. Glacier mass-balance fluctuations in the Pacific Northwest and Alaska, USA

    USGS Publications Warehouse

    Josberger, E.G.; Bidlake, W.R.; March, R.S.; Kennedy, B.W.

    2007-01-01

    The more than 40 year record of net and seasonal mass-balance 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 mass-balance record grows in length, it is revealing significant changes in previously described glacier mass-balance 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 balances 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 balance of the two maritime glaciers, with a weakening of the correlation between the winter balance fluctuations and the PDO. Non-synchronous periods of positive and negative net balance for each glacier prior to 1989 were followed by a 1989-2004 period of synchronous and almost exclusively negative net balances that averaged -0.8 m for the three glaciers.

  11. Comparison of geodetic and glaciological mass-balance techniques, Gulkana Glacier, Alaska, U.S.A

    USGS Publications Warehouse

    Cox, L.H.; March, R.S.

    2004-01-01

    The net mass balance on Gulkana Glacier, Alaska, U.S.A., has been measured since 1966 by the glaciological method, in which seasonal balances are measured at three index sites and extrapolated over large areas of the glacier. Systematic errors can accumulate linearly with time in this method. Therefore, the geodetic balance, in which errors are less time-dependent, was calculated for comparison with the glaciological method. Digital elevation models of the glacier in 1974, 1993 and 1999 were prepared using aerial photographs, and geodetic balances were computed, giving - 6.0??0.7 m w.e. from 1974 to 1993 and - 11.8??0.7 m w.e. from 1974 to 1999. These balances are compared with the glaciological balances over the same intervals, which were - 5.8??0.9 and -11.2??1.0 m w.e. respectively; both balances show that the thinning rate tripled in the 1990s. These cumulative balances differ by <6%. For this close agreement, the glaciologically measured mass balance of Gulkana Glacier must be largely free of systematic errors and be based on a time-variable area-altitude distribution, and the photography used in the geodetic method must have enough contrast to enable accurate photogrammetry.

  12. Compact Sensitive Piezoelectric Mass Balance for Measurement of Unconsolidated Materials in Space

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart; Trebi-Ollennu, Ashitey; Bonitz, Robert; Bar-Cohen, Yoseph; Yen, Jesse T.

    2010-01-01

    In many in-situ instruments information about the mass of the sample could aid in the interpretation of the data and portioning instruments might require an accurate sizing of the sample mass before dispensing the sample. In addition, on potential sample return missions a method to directly assess the captured sample size would be required to determine if the sampler could return or needs to continue attempting to acquire sample. In an effort to meet these requirements piezoelectric balances were developed using flextensional actuators which are capable of monitoring the mass using two methods. A piezoelectric balance could be used to measure mass directly by monitoring the voltage developed across the piezoelectric which is linear with force, or it could be used in resonance to produce a frequency change proportional to the mass change. In this case of the latter, the piezoelectric actuator/balance would be swept in frequency through its fundamental resonance. If a mass is added to the balance the resonance frequency would shift down proportionally to the mass. By monitoring the frequency shift the mass could be determined. This design would allow for two independent measurements of the mass. In microgravity environments spacecraft thrusters could be used to provide acceleration in order to produce the required force for the first technique or to bring the mass into contact with the balance in the second approach. In addition, the measuring actuators, if driven at higher voltages, could be used to fluidize the powder to aid sample movement. In this paper, we outline some of our design considerations and present the results of a few prototype balances that we have developed.

  13. Glaciological and geodetic mass balance of ten long-term glaciers in Norway

    NASA Astrophysics Data System (ADS)

    Andreassen, L. M.; Elvehøy, H.; Kjøllmoen, B.; Engeset, R. V.

    2015-11-01

    The glaciological and geodetic methods provide independent observations of glacier mass balance. The glaciological method measures the surface mass balance, on a seasonal or annual basis, whereas the geodetic method measures surface, internal and basal mass balances, over a period of years or decades. In this paper, we reanalyse the 10 glaciers with long-term mass balance series in Norway. The reanalysis includes (i) homogenisation of both glaciological and geodetic observation series, (ii) uncertainty assessment, (iii) estimates of generic differences including estimates of internal and basal melt, (iv) validation, and (v) partly calibration of mass balance series. This study comprises an extensive set of data (454 mass balance years, 34 geodetic surveys and large volumes of supporting data, such as metadata and field notes). In total, 21 periods of data were compared and the results show discrepancies between the glaciological and geodetic methods for some glaciers, which in part are attributed to internal and basal ablation and in part to inhomogeneity in the data processing. Deviations were smaller than 0.2 m w.e. a-1 for 12 out of 21 periods. Calibration was applied to seven out of 21 periods, as the deviations were larger than the uncertainty. The reanalysed glaciological series shows a more consistent signal of glacier change over the period of observations than previously reported: six glaciers had a significant mass loss (14-22 m w.e.) and four glaciers were nearly in balance. All glaciers have lost mass after year 2000. More research is needed on the sources of uncertainty, to reduce uncertainties and adjust the observation programmes accordingly. The study confirms the value of carrying out independent high-quality geodetic surveys to check and correct field observations.

  14. Reanalysis of long-term series of glaciological and geodetic mass balance for 10 Norwegian glaciers

    NASA Astrophysics Data System (ADS)

    Andreassen, Liss M.; Elvehøy, Hallgeir; Kjøllmoen, Bjarne; Engeset, Rune V.

    2016-03-01

    Glaciological and geodetic methods provide independent observations of glacier mass balance. The glaciological method measures the surface mass balance, on a seasonal or annual basis, whereas the geodetic method measures surface, internal, and basal mass balances, over a period of years or decades. In this paper, we reanalyse the 10 glaciers with long-term mass-balance series in Norway. The reanalysis includes (i) homogenisation of both glaciological and geodetic observation series, (ii) uncertainty assessment, (iii) estimates of generic differences including estimates of internal and basal melt, (iv) validation, and, if needed, (v) calibration of mass-balance series. This study comprises an extensive set of data (484 mass-balance years, 34 geodetic surveys, and large volumes of supporting data, such as metadata and field notes). In total, 21 periods of data were compared and the results show discrepancies between the glaciological and geodetic methods for some glaciers, which are attributed in part to internal and basal ablation and in part to inhomogeneity in the data processing. Deviations were smaller than 0.2 m w.e. a-1 for 12 out of 21 periods. Calibration was applied to 7 out of 21 periods, as the deviations were larger than the uncertainty. The reanalysed glaciological series shows a more consistent signal of glacier change over the period of observations than previously reported: six glaciers had a significant mass loss (14-22 m w.e.) and four glaciers were nearly in balance. All glaciers have lost mass after the year 2000. More research is needed on the sources of uncertainty to reduce uncertainties and adjust the observation programmes accordingly. The study confirms the value of carrying out independent high-quality geodetic surveys to check and correct field observations.

  15. CryoSat-2 observations of Arctic ice-cap mass trends

    NASA Astrophysics Data System (ADS)

    Wouters, Bert; Bamber, Jonathan; Gardner, Alex; Moholdt, Geir; Schoen, Nana; Wahr, John

    2014-05-01

    The primary objective of Cryosat-2 is to measure changes in sea ice freeboard and ice sheet topography, but the satellite also provides valuable information on height changes of smaller ice caps and icefields. Compared to earlier radar altimetry missions, which where unable to retrieve elevation changes over complex terrain, Cryosat-2 has an improved capacity to locate across-track echoes and a finer spatial resolution that allows for the retrieval of elevation changes at scales of a few kilometers. We explore the utility of using Cryosat-2 interferometric SARin data to reconstruct volume changes of major ice masses in the Canadian Arctic. These measurements are compared to elevations determined from airborne (OIB ATM) and satellite (ICESat) laser altimetry. We discuss potential biases, such as slope-dependent offsets and biases depending on the orientation of the satellite track. We extrapolate the bias corrected Cryosat-2 derived elevation changes over the entire region to arrive at an estimate of the total change in glacier mass over period 2010 to 2013 and compare this to monthly glacier mass anomalies as derived from gravity measurements made by the GRACE mission.

  16. Quantifying groundwater dependence of a sub-polar lake cluster in Finland using an isotope mass balance approach

    NASA Astrophysics Data System (ADS)

    Isokangas, E.; Rozanski, K.; Rossi, P. M.; Ronkanen, A.-K.; Kløve, B.

    2014-08-01

    A stable isotope study of 67 kettle lakes and ponds situated on an esker aquifer (90 km2) in northern Finland was carried out in the summer of 2013 to determine the role of groundwater inflow in groundwater-dependent lakes. Distinct seasonal fluctuations in the δ18O and δ2H values of lakes are the result of seasonal ice cover prohibiting evaporation during the winter. An isotope mass balance approach was used to calculate the inflow-to-evaporation ratios (ITOT/E) of all 67 lakes during the summer of 2013 when the isotopic compositions of the lakes were approaching a steady-state. The normalised relative humidity needed in this approach came from assuming a terminal lake situation for one of the lakes showing the highest isotope enrichment. Since evaporation rates were derived independently of any mass balance considerations, it was possible to determine the total inflow (ITOT) and mean turnover time (MTT) of the lakes. Furthermore, the groundwater seepage rates of those lakes revealing no visible surface inflow were calculated. Here, a quantitative measure was introduced for the dependence of a lake on groundwater (G index) that is defined as the percentage contribution of groundwater inflow to the total inflow of water to the given lake. The G index values of the lakes studied ranged from 27.8-95.0%, revealing large differences in groundwater dependency among the lakes. This study shows the effectiveness of applying an isotope mass balance approach to quantify the groundwater reliance of lakes situated in a relatively small area with similar climatic conditions.

  17. A LEGO Watt balance: An apparatus to determine a mass based on the new SI

    NASA Astrophysics Data System (ADS)

    Chao, L. S.; Schlamminger, S.; Newell, D. B.; Pratt, J. R.; Seifert, F.; Zhang, X.; Sineriz, G.; Liu, M.; Haddad, D.

    2015-11-01

    A global effort to redefine our International System of Units (SI) is underway, and the change to the new system is expected to occur in 2018. Within the newly redefined SI, the present base units will still exist but be derived from fixed numerical values of seven reference constants. In particular, the unit of mass (the kilogram) will be realized through a fixed value of the Planck constant h. A so-called watt balance, for example, can then be used to realize the kilogram unit of mass within a few parts in 108. Such a balance has been designed and constructed at the National Institute of Standards and Technology. For educational outreach and to demonstrate the principle, we have constructed a LEGO tabletop watt balance capable of measuring a gram-level masses to 1% relative uncertainty. This article presents the design, construction, and performance of the LEGO watt balance and its ability to determine h.

  18. Surface energy budget and mass balance of Zhadang Glacier in the central Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Li, B.; Acharya, K.; Yu, Z.; Su, F.; liang, Z.

    2011-12-01

    It is difficult to clearly investigate the surface energy budget and glacier evolution under the changed climate environments, especially on accounts of limited data set. We attempted to calculate the summer mass balance of Zhadang Glacier (5710 m above sea level), located in the central Tibetan Plateau. This small and high-altitude glacier has been retreating during the previous decades. Energy balance was calculated on a 30 m square grid on the glacier for the summer periods in 2007 and 2008. On average, net radiation contributed more than 96% of the energy gain while only less than 4% was supplied by the sensible heat flux. Most energy loss on the glacier was contributed by the turbulent heat fluxes and only roughly 30% of the total energy was available for melting. A large deficit and a surplus summer mass balance were obtained for years 2006/07 and 2007/08, respectively. The switch in mass balance from negative to positive in the summer of 2008 is caused by early precipitation (mostly snow) resulting in low temperature on the glacier. Low temperature produces less energy that contributes to melting, whereas increased snow accumulation produces higher surface albedo reflecting away incoming solar radiation. The high sensitivity of air temperature may imply that the low temperature was more important than the increased precipitation in the mass balance switch in Zhadang Glacier. Despite a continuous negative mass balance for several decades in Zhadang Glacier 2008 may have brought a temporary relief.

  19. Mass-balance measurements in Alaska and suggestions for simplified observation programs

    USGS Publications Warehouse

    Trabant, D.C.; March, R.S.

    1999-01-01

    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 mass-balance measurements are extrapolated and integrated with area to determine glacier and basin mass balances. Unassessable errors in the glacier and basin mass-balance data reduce the value of the data set for correlations with climate change indices. The minimum glacier mass-balance program has at least three measurement sites on a glacier and the measurements must include the seasonal components of mass balance as well as the annual balance.

  20. Measuring Greenland Ice Mass Variation With Gravity Recovery and the Climate Experiment Gravity and GPS

    NASA Technical Reports Server (NTRS)

    Wu, Xiao-Ping

    1999-01-01

    The response of the Greenland ice sheet to climate change could significantly alter sea level. The ice 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 ice mass 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 ice 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 mass 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 ice model for current mass variation and a variant of the Tushingham and Peltier ICE-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 ice 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 ice mass 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 ice 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

  1. Postexercise impact of ice-cold water bath on the oxidant-antioxidant balance in healthy men.

    PubMed

    Sutkowy, Paweł; Woźniak, Alina; Boraczyński, Tomasz; Mila-Kierzenkowska, Celestyna; Boraczyński, Michał

    2015-01-01

    The aim of the study was to determine the effect of a 5 min head-out ice-cold water bath on the oxidant-antioxidant balance in response to exercise. The crossover study included the subjects (n = 24; aged 28.7 ± 7.3 years) who performed two identical stationary cycling bouts for 30 min and recovered for 10 min at room temperature (RT = 20°C; session 1) or in a pool with ice-cold water (ICW = 3°C, 5 min immersion; session 2). The concentration of thiobarbituric acid reactive substances (TBARS) in blood plasma (TBARSpl) and erythrocytes (TBARSer) and the erythrocytic activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were measured three times during each of the two study sessions: before the exercise (baseline) and 20 and 40 min after the appropriate recovery session. Lower concentration of TBARSpl 40 min after postexercise recovery in ICW was revealed as compared with that after recovery at RT (P < 0.05). Moreover, a statistically significant postexercise increase in the TBARSpl and TBARSer concentrations was found (P < 0.01 and P < 0.05, resp.). A short-term ice-cold water bath decreases postexercise lipid peroxidation. PMID:25866803

  2. Postexercise Impact of Ice-Cold Water Bath on the Oxidant-Antioxidant Balance in Healthy Men

    PubMed Central

    Boraczyński, Tomasz; Boraczyński, Michał

    2015-01-01

    The aim of the study was to determine the effect of a 5 min head-out ice-cold water bath on the oxidant-antioxidant balance in response to exercise. The crossover study included the subjects (n = 24; aged 28.7 ± 7.3 years) who performed two identical stationary cycling bouts for 30 min and recovered for 10 min at room temperature (RT = 20°C; session 1) or in a pool with ice-cold water (ICW = 3°C, 5 min immersion; session 2). The concentration of thiobarbituric acid reactive substances (TBARS) in blood plasma (TBARSpl) and erythrocytes (TBARSer) and the erythrocytic activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were measured three times during each of the two study sessions: before the exercise (baseline) and 20 and 40 min after the appropriate recovery session. Lower concentration of TBARSpl 40 min after postexercise recovery in ICW was revealed as compared with that after recovery at RT (P < 0.05). Moreover, a statistically significant postexercise increase in the TBARSpl and TBARSer concentrations was found (P < 0.01 and P < 0.05, resp.). A short-term ice-cold water bath decreases postexercise lipid peroxidation. PMID:25866803

  3. Mass balance and surface velocity reconstructions of two reference Caucasus glaciers

    NASA Astrophysics Data System (ADS)

    Rybak, Oleg; Kaminskaia, Mariia; Kutuzov, Stanislav; Lavrentiev, Ivan; Morozova, Polina; Popovnin, Victor; Rybak, Elena

    2016-04-01

    Total glacial volume of the Greater Caucasus exceeds 40 cubic km and its area exceeds 1 thousand square km. During the 20th century, mountain glaciers at the Greater Caucasus were continuously degrading. According to various estimates, their area reduced more than one-third and their volume almost by half. The process of degradation was accompanied by growing population and economical development on surrounding territories. In the 21st century under proceeding global warming, a tendency of shrinking of area and volume of glaciation is obviously expected to continue. Working out of strategy of sustainable economic development of the region is the main motivation for elaboration of predictions of glaciers' evolution in the changing environment. Growing demand of fresh water is the basic challenge for the local economy, and efficient planning of water resources is impossible without knowing future state of glaciation. Therefore our research aims at obtaining accurate evaluation of probable future change of the most prominent mountain glaciers of the Greater Caucasus in forthcoming decades and at studying impacts of changing characteristics of glaciation on the run-off in the area. Initially, we focus on two so-called reference glaciers - Marukh (Western Caucasus) and Djankuat (Central Caucasus). Intensive field observations on both of them have been conducted during the last half of the century and essential amount of detailed relevant information has been collected on their geometry change and on mass balance. Besides, meteorological measurements were episodically carried out directly on the glaciers providing enough data for correlation of the local weather conditions with the data from the closest meteorological stations. That is why studying of response of Marukh and Djankuat on the environmental change can be accurately verified, which is crucial for understanding mechanisms driving evolution of large glaciated area in the Caucasus. As the instrument of research

  4. Mass loss of Greenland's glaciers and ice caps 2003-2008 from ICESat data

    NASA Astrophysics Data System (ADS)

    Bolch, Tobias; Sandberg Sørensen, Louise; Simonsen, Sebastian B.; Mölg, Nico; Machguth, Horst; Rastner, Philipp; Paul, Frank

    2013-04-01

    The melt water of the glaciers and ice caps (GIC) on Greenland could make a substantial contribution to global sea-level rise during this century. The recently finalized Greenland glacier inventory classified all GIC according to its connectivity to the ice sheet (CL0: no connection, CL1: weak connection, CL2: strong connection). This dataset allowed us for the first time to determine their mass changes separately from the ice sheet using space-borne laser altimetry data from the ICESat GLAS sensor. The accuracy of the altimetry measurements of about ±0.5 m even over rough surfaces along with their small footprint (about 70 m) is making them very suitable to assess elevation changes over GIC. A major challenge with ICESat data is the sparse density of the tracks (horizontal separation is about 30 km in southern and ~10 km in northern Greenland), and the fact that the repeat tracks can be several hundred metres apart. A further challenge is the volume to mass conversion. We extrapolated the elevation changes based on the glacier hypsometry and applied corrections for firn compaction and ice density based on climatic conditions. The Greenland GIC which are clearly separable from the ice-sheet (CL0, CL1) lost 30.1 ± 9.4 Gt a-1 or 0.08 ± 0.026 mm a-1 sea-level equivalent (SLE) between 2003 and 2008. When considering all hydrologically separable GIC (CL0-2, including the Geikie Plateau) the loss is 46.8 ± 13.4 Gt a-1 (0.12 ± 0.038 mm a-1 SLE). This is a significant fraction (about 20%) of the reported overall mass loss of Greenland (including the ice sheet) and up to 10% of the estimated contribution from the world's GIC to global sea-level rise. The mass loss of the GIC is per unit area about 2.5 times higher than for the ice sheet, and marine-terminating glaciers account for about half of the mass loss. The loss was highest in the south-eastern sector and lowest in the northern sector of Greenland.

  5. Retrieval of ice crystals' mass from ice water content and particle distribution measurements: a numerical optimization approach

    NASA Astrophysics Data System (ADS)

    Coutris, Pierre; Leroy, Delphine; Fontaine, Emmanuel; Schwarzenboeck, Alfons; Strapp, J. Walter

    2016-04-01

    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' mass as a function of their size, environmental temperature and crystal microphysical history, this study presents the methodology to retrieve the mass 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 Ice Crystals (HAIC) / High Ice 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 ice 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 ice 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' mass 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

  6. Ice mass loss in Greenland, the Gulf of Alaska, and the Canadian Archipelago: Seasonal cycles and decadal trends

    NASA Astrophysics Data System (ADS)

    Harig, Christopher; Simons, Frederik J.

    2016-04-01

    Over the past several decades mountain glaciers and ice caps have been significant contributors to sea level rise. Here we estimate the ice mass changes in the Canadian Archipelago, the Gulf of Alaska, and Greenland since 2003 by analyzing time-varying gravimetry data from the Gravity Recovery and Climate Experiment. Prior to 2013, interannual ice mass variability in the Gulf of Alaska and in regions around Greenland remains within the average estimated over the whole data span. Beginning in summer 2013, ice mass in regions around Greenland departs positively from its long-term trend. Over Greenland this anomaly reached almost 500 Gt through the end of 2014. Overall, long-term ice mass loss from Greenland and the Canadian Archipelago continues to accelerate, while losses around the Gulf of Alaska region continue but remain steady with no significant acceleration.

  7. Mass Balance. Operational Control Tests for Wastewater Treatment Facilities. Instructor's Manual [and] Student Workbook.

    ERIC Educational Resources Information Center

    Carnegie, John W.

    This module describes the process used to determine solids mass and location throughout a waste water treatment plant, explains how these values are used to determine the solids mass balance around single treatment units and the entire system, and presents calculations of solids in pounds and sludge units. The instructor's manual contains a…

  8. The mass balance approach: application to interpreting the chemical evolution of hydrologic systems.

    USGS Publications Warehouse

    Plummer, L.N.; Back, W.

    1980-01-01

    Mass balance calculations are applied to observed chemical and isotopic data of three natural water systems involving carbonate reactions in order to define mineral stoichiometry of reactants and products, relative rates of reactions, and mass transfer. One study evaluates reactions in a lagoon on the east coast of the Yucatan Peninsula, Mexico.- from Authors

  9. A 3-axis force balanced accelerometer using a single proof-mass

    SciTech Connect

    Lemkin, M.A.; Boser, B.E.; Auslander, D.; Smith, J.

    1997-04-01

    This paper presents a new method for wideband force balancing a proof-mass in multiple axes simultaneously. Capacitive position sense and force feedback are accomplished using the same air-gap capacitors through time multiplexing. Proof of concept is experimentally demonstrated with a single-mass monolithic surface micromachined 3-axis accelerometer.

  10. Comparison of direct and geodetic mass balances on a multi-annual time scale

    NASA Astrophysics Data System (ADS)

    Fischer, A.

    2010-07-01

    Glacier mass balance is measured with the direct or the geodetic method. In this study, the geodetic mass balances of six Austrian glaciers in 19 periods between 1953 and 2006 are compared to the direct mass balances in the same periods. The mean annual geodetic mass balance for all periods is -0.5 m w.e./year. The mean difference between the geodetic and the direct data is -0.7 m w.e., the minimum -7.3 m w.e. and the maximum 5.6 m w.e. The accuracy of geodetic mass balance resulting from the accuracy of the DEMs ranges from 2 m w.e. for photogrammetric data to 0.002 m w.e. for LIDAR data. Basal melt, seasonal snow cover and density changes of the surface layer contribute up to 0.7 m w.e. for the period of 10 years to the difference to the direct method. The characteristics of published data of Griesgletscher, Gulkana Glacier, Lemon Creek glacier, South Cascade, Storbreen, Storglaciären, and Zongo Glacier is similar to these Austrian glaciers. For 26 analyzed periods with an average length of 18 years the mean difference between the geodetic and the direct data is -0.4 m w.e., the minimum -7.2 m w.e. and the maximum 3.6 m w.e. Longer periods between the acquisition of the DEMs do not necessarily result in a higher accuracy of the geodetic mass balance. Specific glaciers show specific trends of the difference between the direct and the geodetic data according to their type and state. In conclusion, geodetic and direct mass balance data are complementary, but differ systematically.

  11. Crustal uplift due to ice mass variability on Upernavik Isstrøm, west Greenland

    NASA Astrophysics Data System (ADS)

    Nielsen, Karina; Khan, Shfaqat Abbas; Korsgaard, Niels J.; Kjær, Kurt H.; Wahr, John; Bevis, Michael; Stearns, Leigh A.; Timm, Lars H.

    2012-11-01

    We estimate the mass loss rate of Upernavik Isstrøm (UI) using surface elevation changes between a SPOT 5 Digital Elevation Model (DEM) from 2008 and NASA's Airborne Topographic Mapper (ATM) data from 2010. To assess the validity of our mass loss estimate, we analyze GPS data between 2007 and 2011 from two continuous receivers, UPVK and SRMP which are established on bedrock and located ∼65 and ∼2 km from the front of UI, respectively. We construct along-track elevation changes on UI for several time intervals during 2005-2011, based on ATM, SPOT 5 and Ice, Cloud, and land Elevation Satellite (ICESat) data to assess temporal changes of UI. We estimate a mass loss rate of -6.7±4.2 Gt/yr, over an area of ∼1600 km2. The ice mass loss occurs primarily over the northern glacier of UI. This pattern is also observed ∼40 km upstream, where we observe glacier thinning at a rate of -1.6±0.3 m/yr across the northern portion of UI and -0.5±0.1 m/yr across the southern portion. GPS measurements suggest bedrock uplift rates of 7.6±0.6 mm/yr (UPVK) and 16.2±0.6 mm/yr (SRMP). The modeled ice mass loss of UI causes bedrock uplift rates of 1.3±0.6 mm/yr (UPVK) and 8.3±4.2 mm/yr (SRMP). Including additional contributions from ice mass changes outside UI and from Glacial Isostatic Adjustment (GIA), we obtain total modeled uplift rates of 4.7±0.6 mm/yr (UPVK) and 13.8±4.2 mm/yr (SRMP). The modeled uplift rates from our UI ice mass loss are substantially lower, indicating that additional mass loss is taking place outside of UI. We obtain a difference of 0.6 mm/yr between the modeled and observed relative uplift rates (SRMP relative to UPVK), suggesting that the mass loss of UI is well captured in the model. We observe elevation changes from -15 to -40 m/yr near the front during the period 2005-2011, indicating that UI undergoes large variations in thinning pattern over short time spans.

  12. Distinguishing neutrino mass hierarchies using dark matter annihilation signals at IceCube

    SciTech Connect

    Allahverdi, Rouzbeh; Dutta, Bhaskar; Ghosh, Dilip Kumar; Knockel, Bradley; Saha, Ipsita

    2015-12-01

    We explore the possibility of distinguishing neutrino mass hierarchies through the neutrino signal from dark matter annihilation at neutrino telescopes. We consider a simple extension of the standard model where the neutrino masses and mixing angles are obtained via the type-II seesaw mechanism as an explicit example. We show that future extensions of IceCube 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 mass hierarchies, in this model.

  13. To wet or not to wet? Dispersion forces tip the balance for water ice on metals

    NASA Astrophysics Data System (ADS)

    Carrasco, Javier; Santra, Biswajit; Klimes, Jiri; Michaelides, Angelos

    2012-02-01

    For almost 30 years now, density functional theory (DFT) has been used to explore the molecular level details of water-metal interfaces. However, since the typical generalized gradient approximation exchange-correlation functionals used in these studies do not account for van der Waals (vdW) dispersion forces, the role dispersion plays in water adsorption remains unclear. Here, we tackle this issue head on applying a newly developed non-local functional [J. Klimes et al., J. Phys.: Condens. Matter 22, 022201 (2010)] to two of the most widely studied water-ice adsorption systems, namely water on Cu(110) and Ru(0001). We show that non-local correlations contribute substantially to the water-metal bond and that this is an important factor in governing the relative stabilities of wetting layers and 3D bulk ice [J. Carrasco et al., Phys. Rev. Lett. 106, 026101 (2011)]. Due to the greater polarizability of the substrate metal atoms, non-local correlations between water and the metal exceed those between water within ice. This sheds light on a long-standing problem, wherein common DFT exchange-correlation functionals incorrectly predict that none of the low temperature experimentally characterized ice-like wetting layers are thermodynamically stable.

  14. Relative sea-level response to Little Ice Age ice mass change in south central Alaska: Reconciling model predictions and geological evidence

    NASA Astrophysics Data System (ADS)

    Barlow, Natasha L. M.; Shennan, Ian; Long, Antony J.

    2012-01-01

    Integration of geological data and glacio-isostatic adjustment (GIA) modelling shows that it is possible to decouple complex mechanisms of relative sea-level (RSL) change in a tectonically active glacial environment. We model a simplest solution in which RSL changes in upper Cook Inlet, Alaska, are a combination of the interplay of tectonic and isostatic processes driven by the unique rheology of this tectonically active location. We calculate interseismic uplift during latter part of the penultimate earthquake cycle to vary from 0.3 to 0.7 mm/yr. Diatom based reconstructions of RSL from tidal marsh sediment sequences coupled with detailed age models, from AD 1400 to the AD 1964 great earthquake, show deviations from a purely tectonically driven model of regional RSL. Glacial isostatic modelling, constrained by GPS data, predicts up to 70 cm sea-level change due to mountain glacier mass balance changes during the Little Ice Age. Misfits between the GIA model predictions and RSL reconstructions in the 19th and 20th century highlight that the tidal marshes of upper Cook Inlet potentially record a hemispheric-wide acceleration in sea level and that other more complex Earth process combinations may contribute to regional RSL change.

  15. Present and future mass standards for the LNE watt balance and the future dissemination of the mass unit in France

    NASA Astrophysics Data System (ADS)

    Pinot, Patrick; Beaudoux, Florian; Bentouati, Djilali; Espel, Patrick; Madec, Tanguy; Thomas, Matthieu; Silvestri, Zaccari; Ziane, Djamel; Piquemal, François

    2016-08-01

    The value of the Planck constant h was determined in 2014 by means of the LNE watt balance experiment. The relative standard uncertainty was 31 parts in 108. This first determination was performed in air with a 500 g mass standard made from XSH Alacrite. The main uncertainty components in air associated with the mass involve the calibration, the mass stability, the buoyancy correction and the magnetic interaction correction. The combined relative uncertainty due to the mass is 7.2 parts in 108. The use in 2016 of a mass standard made from platinum iridium alloy significantly reduces the component of uncertainty arising from the mass standard for a Planck constant measurement either in air or under vacuum. The relative uncertainty due to this contribution is estimated to be about 3 parts in 108 in air and one part in 108 under vacuum. The future system for the dissemination of the mass unit using the LNE watt balance will be based on a primary realization with three 500 g mass standards made from platinum–iridium alloy, pure iridium and Udimet 720 respectively, coupled with a pool of kilograms made from different materials. Pure iridium and Udimet 720 are new materials to make reference mass standards proposed by CNAM and LNE respectively and have never been used by any NMI for manufacturing mass standards until now. Some new results concerning their surface behavior are given.

  16. The Influence of Platelet Ice and Snow on Antarctic Land-fast Sea Ice

    NASA Astrophysics Data System (ADS)

    Hoppmann, M.; Nicolaus, M.

    2011-12-01

    Sea ice fastened to coasts, icebergs and ice shelves is of crucial importance for climate- and ecosystems. Near Antarctic ice shelves, this land-fast sea ice exhibits two unique characteristics that distinguish it from most other sea ice: a sub-ice layer of ice platelets and a highly stratified and thick snow cover. Ice platelets are flat, plate-like ice crystals forming and growing in a layer of super-cooled water which originates from ice shelf cavities. During growth, heat is lost to the super-cooled ocean rather than conducted to the atmosphere. The crystals accumulate beneath the solid sea-ice cover, forming a layer of loose platelets and eventually becoming incorporated into the sea-ice fabric as platelet ice. Considering the fact that the amount of platelet ice contributes between 10 and 60% to the mass of the land-fast sea ice around Antarctica, very little is known about its spatial and temporal variability. A thick and partly multi-year snow cover develops on top of the Antarctic fast ice, ultimately altering the sea-ice surface and affecting the sea-ice thermodynamics and mass balance. It typically leads to snow-ice formation, surface flooding, and the development of superimposed ice from snow melt water. In order to investigate the role of platelet ice and snow for Antarctic fast ice, we have initiated a regular observation program on the land-fast sea ice of Atka Bay as part of the international Antarctic Fast Ice Network (AFIN). We performed manual measurements of sea-ice and snow thicknesses from June to December 2010 and 2011. Additionally, a mass balance buoy and an automatic weather station were deployed in 2011 and ice cores were taken. Our measurements will reveal insight into the spatial and temporal variability of sea-ice and snow thickness distributions on Atka Bay fast ice. First results show that sea-ice thickness is lowest in the eastern part of the Bay, where a thick snow cover leads to extensive surface flooding. In the West, dynamic

  17. Global Trends and Variability In the Mass Balance of Mountain and Valley Glaciers

    NASA Astrophysics Data System (ADS)

    Medwedeff, W. G.; Roe, G.

    2015-12-01

    Glacier mass balance (i.e., accumulation and ablation) is the most direct connection between climate and glaciers. We perform a comprehensive evaluation of the available global network of mass-balance measurements, with a particular interest given to mountain and valley glaciers. Each mass-balance time series is decomposed into a trend and the variability about that trend. Observed variability ranges by an order of magnitude, depending on climate setting (i.e., maritime vs. continental). For the great majority of glaciers, variability is well characterized by normally distributed, random fluctuations that are uncorrelated between seasons, or in subsequent years. The magnitude of variability for both summer and winter is well correlated with mean wintertime balance, which reflects the climatic setting. Collectively, summertime variability exceeds wintertime variability, except for maritime glaciers. Trends in annual mass balance are generally negative, driven primarily by summertime changes. Approximately 25% of annual-mean records show statistically significant negative trends when judged in isolation. In aggregate, the global trend is negative and significant. We further evaluate the magnitude of trends relative to the variability. We find that, on average, trends are approximately -0.2 standard deviations per decade, although there is a broad spread among individual glaciers. Finally, for two long records we also compare mass-balance trends and variability with nearby meteorological stations. We find significant differences among stations meaning caution is warranted in interpreting any point measurement (such as mass balance) as representative of region-wide behavior. By placing observed trends in the context of natural variability, the results are useful for interpreting past glacial history, and for placing constraints on future predictability.

  18. Trends and variability in the global dataset of glacier mass balance

    NASA Astrophysics Data System (ADS)

    Medwedeff, William G.; Roe, Gerard H.

    2016-06-01

    Glacier mass balance (i.e., accumulation and ablation) is the most direct connection between climate and glaciers. We perform a comprehensive evaluation of the available global network of mass-balance measurements. Each mass-balance time series is decomposed into a trend and the variability about that trend. Observed variability ranges by an order of magnitude, depending on climate setting (i.e., maritime vs continental). For the great majority of glaciers, variability is well characterized by normally distributed, random fluctuations that are uncorrelated between seasons, or in subsequent years. The magnitude of variability for both summer and winter is well correlated with mean wintertime balance, which reflects the climatic setting. Collectively, summertime variability exceeds wintertime variability, except for maritime glaciers. Trends in annual mass balance are generally negative, driven primarily by summertime changes. Approximately 25 % of annual-mean records show statistically significant negative trends when judged in isolation. In aggregate, the global trend is negative and significant. We further evaluate the magnitude of trends relative to the variability. We find that, on average, trends are approximately -0.2 standard deviations per decade, although there is a broad spread among individual glaciers. Finally, for two long records we also compare mass-balance trends and variability with nearby meteorological stations. We find significant differences among stations meaning caution is warranted in interpreting any point measurement (such as mass balance) as representative of region-wide behavior. By placing observed trends in the context of natural variability, the results are useful for interpreting past glacial history, and for placing constraints on future predictability.

  19. Assessing modeled Greenland surface mass balance in the GISS Model E2 and its sensitivity to surface albedo

    NASA Astrophysics Data System (ADS)

    Alexander, Patrick; LeGrande, Allegra N.; Koenig, Lora S.; Tedesco, Marco; Moustafa, Samiah E.; Ivanoff, Alvaro; Fischer, Robert P.; Fettweis, Xavier

    2016-04-01

    The surface mass balance (SMB) of the Greenland Ice Sheet (GrIS) plays an important role in global sea level change. Regional Climate Models (RCMs) such as the Modèle Atmosphérique Régionale (MAR) have been employed at high spatial resolution with relatively complex physics to simulate ice sheet SMB. Global climate models (GCMs) incorporate less sophisticated physical schemes and provide outputs at a lower spatial resolution, but have the advantage of modeling the interaction between different components of the earth's oceans, climate, and land surface at a global scale. Improving the ability of GCMs to represent ice sheet SMB is important for making predictions of future changes in global sea level. With the ultimate goal of improving SMB simulated by the Goddard Institute for Space Studies (GISS) Model E2 GCM, we compare simulated GrIS SMB against the outputs of the MAR model and radar-derived estimates of snow accumulation. In order to reproduce present-day climate variability in the Model E2 simulation, winds are constrained to match the reanalysis datasets used to force MAR at the lateral boundaries. We conduct a preliminary assessment of the sensitivity of the simulated Model E2 SMB to surface albedo, a parameter that is known to strongly influence SMB. Model E2 albedo is set to a fixed value of 0.8 over the entire ice sheet in the initial configuration of the model (control case). We adjust this fixed value in an ensemble of simulations over a range of 0.4 to 0.8 (roughly the range of observed summer GrIS albedo values) to examine the sensitivity of ice-sheet-wide SMB to albedo. We prescribe albedo from the Moderate Resolution Imaging Spectroradiometer (MODIS) MCD43A3 v6 to examine the impact of a more realistic spatial and temporal variations in albedo. An age-dependent snow albedo parameterization is applied, and its impact on SMB relative to observations and the RCM is assessed.

  20. The influence of air temperature inversions on snowmelt and glacier mass-balance simulations, Ammassalik island, SE Greenland

    SciTech Connect

    Mernild, Sebastian Haugard; Liston, Glen

    2009-01-01

    In many applications, a realistic description of air temperature inversions is essential for accurate snow and glacier ice melt, and glacier mass-balance 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 ice 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 ice-choked fjords and ocean. To account for the influence of these inversions on the spatiotemporal variation of air 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 mass-balance 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.eq. y

  1. Mass-balance Approach to Interpreting Weathering Reactions in Watershed Systems

    NASA Astrophysics Data System (ADS)

    Bricker, O. P.; Jones, B. F.; Bowser, C. J.

    2003-12-01

    The mass-balance approach is conceptually simple and has found widespread applications in many fields over the years. For example, chemists use mass balance (Stumm and Morgan, 1996) to sum the various species containing an element in order to determine the total amount of that element in the system (free ion, complexes). Glaciologists use mass balance to determine the changes in mass of glaciers ( Mayo et al., 1972 and references therein). Groundwater hydrologists use this method to interpret changes in water balance in groundwater systems ( Rasmussen and Andreasen, 1959; Bredehoeft et al., 1982; Heath, 1983; Konikow and Mercer, 1988; Freeze and Cherry, 1979; Ingebritsen and Sanford, 1998). This method has also been used to determine changes in chemistry along a flow path ( Plummer et al., 1983; Bowser and Jones, 1990) and to quantify lake hydrologic budgets using stable isotopes ( Krabbenhoft et al., 1994). Blum and Erel (see Chapter 5.12) discuss the use of strontium isotopes, Chapelle (see Chapter 5.14) treats carbon isotopes in groundwater, and Kendall and Doctor (see Chapter 5.11) and Kendall and McDonnell (1998) discuss the use of stable isotopes in mass balance. Although the method is conceptually simple, the parameters that define a mass balance are not always easy to measure. Watershed investigators use mass balance to determine physical and chemical changes in watersheds ( Garrels and Mackenzie, 1967; Plummer et al., 1991; O'Brien et al., 1997; Drever, 1997). Here we focus on describing the mass-balance approach to interpret weathering reactions in watershed systems including shallow groundwater.Because mass balance is simply an accounting of the flux of material into a system minus the flux of material out of the system, the geochemical mass-balance approach is well suited to interpreting weathering reactions in watersheds (catchments) and in other environmental settings (Drever, 1997). It is, perhaps, the most accurate and reliable way of defining

  2. Earth rotation changes since -500 CE driven by ice mass variations

    NASA Astrophysics Data System (ADS)

    Hay, Carling; Mitrovica, Jerry X.; Morrow, Eric; Kopp, Robert E.; Huybers, Peter; Alley, Richard B.

    2016-08-01

    We predict the perturbation to the Earth's length-of-day (LOD) over the Common Era using a recently derived estimate of global sea-level change for this time period. We use this estimate to derive a time series of "clock error", defined as the difference in timing of two clocks, one based on a theoretically invariant time scale (terrestrial time) and one fixed to Earth rotation (universal time), and compare this time series to millennial scale variability in clock error inferred from ancient eclipse records. Under the assumption that global sea-level change over the Common Era is driven by ice mass flux alone, we find that this flux can reconcile a significant fraction of the discrepancies between clock error computed assuming constant slowing of Earth's rotation and that inferred from eclipse records since 700 CE. In contrast, ice mass flux cannot reconcile the temporal variability prior to 700 CE.

  3. Evaporation and the mass and energy balances of the Dead Sea (Invited)

    NASA Astrophysics Data System (ADS)

    Lensky, N.; Gavrieli, I.; Gertman, I.; Nehorai, R.; Lensky, I. M.; Lyakhovsky, V.; Dvorkin, Y.

    2009-12-01

    The Dead Sea is a hypersaline terminal lake experiencing a water level drop of about 1 m/yr over the last decade. The existing estimations for the water balance of the lake are widely variable, reflecting the unknown subsurface water inflow, the rate of evaporation, and the rate of salt accumulation at the lake bottom. To estimate these we calculate the energy and mass balances for the Dead Sea utilizing measured meteorological and hydrographical data from 1996 to 2009. The data is measured from a buoy located in the Dead Sea 5, km from the nearest shore. The data includes solar radiation (incoming), long wave radiation (downward and upward looking), wind velocity, relative humidity, air temperature, air pressure and water temperature profile. Using energy balance we calculate the evaporation rate, taking into account the impact of lowered surface water activity. From mass balance considerations we calculate the salt precipitation rate, which was about 0.1 m/yr during this period. Using an overall mass balance we get the relation between water inflows, which are the least constrained quantity, and the evaporation rate. The average annual inflow is 265-325 mcm/yr, corresponding to an evaporation rate of 1.1-1.2 m/yr. Higher inflows, suggested in previous studies, call for increased evaporation rate and are therefore not in line with the energy balance. We also take into account the spatial variations and discuss how well the data measured in the buoy represent the Dead Sea surface conditions.

  4. Normalized vertical ice mass flux profiles from vertically pointing 8-mm-wavelength Doppler radar

    NASA Technical Reports Server (NTRS)

    Orr, Brad W.; Kropfli, Robert A.

    1993-01-01

    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 ice mass content (imc). The flux of imc, or, alternatively, ice mass flux (imf), is also an important parameter of a cirrus cloud system. Ice mass 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 ice mass 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.

  5. Improving the XAJ Model on the Basis of Mass-Energy Balance

    NASA Astrophysics Data System (ADS)

    Fang, Yuanghao; Corbari, Chiara; Zhang, Xingnan; Mancini, Marco

    2014-11-01

    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 mass balance. 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 mass balance to compute the ET following the energy-mass balance scheme of FEST-EWB. model.

  6. Relations between atmospheric circulation and mass balance of South Cascade Glacier, Washington, USA

    USGS Publications Warehouse

    McCabe, G.J., Jr.; Fountain, A.G.

    1995-01-01

    The yearly net mass balance of South Cascade Glacier, Washington, has decreased since the mid-1970s. Resuls show that the decrease is primarily caused by a significant decrease in the winter mass balance. Changes in atmospheric circulation indicate a decrease in the movement of storms and moisture from the Pacific Ocean into the western contiguous United States. In addition, the increase in winter mean 700-mb heights over western Canada and the northern western contiguous United States indicates an increase in subsidence, which results in a warming and drying of the air that further reduces precipitation and also increases the ratio of rain to snow during the cold season. These factors contribute to below-average winter mass balances. -from Authors

  7. WATER ICE IN HIGH MASS-LOSS RATE OH/IR STARS

    SciTech Connect

    Suh, Kyung-Won; Kwon, Young-Joo

    2013-01-10

    We investigate water-ice features in spectral energy distributions (SEDs) of high mass-loss rate OH/IR stars. We use a radiative transfer code which can consider multiple components of dust shells to make model calculations for various dust species including water ice in the OH/IR stars. We find that the model SEDs are sensitively dependent on the location of the water-ice dust shell. For two sample stars (OH 127.8+0.0 and OH 26.5+0.6), we compare the detailed model results with the infrared observational data including the spectral data from the Infrared Space Observatory (ISO). For the two sample stars, we reproduce the crystalline water-ice features (absorption at 3.1 {mu}m and 11.5 {mu}m; emission at 44 and 62 {mu}m) observed by ISO using a separate component of the water-ice dust shell that condensed at about 84-87 K (r {approx} 1500-1800 AU) as well as the silicate dust shell that condensed at about 1000 K (r {approx} 19-25 AU). For a sample of 1533 OH/IR stars, we present infrared two-color diagrams (2CDs) using the Infrared Astronomical Satellite and AKARI data compared with theoretical model results. We find that the theoretical models clearly show the effects of the crystalline water-ice features (absorption at 11.5 {mu}m and emission at 62 {mu}m) on the 2CDs.

  8. Simulating the climatic mass balance of Svalbard glaciers from 2003 to 2013 with a high-resolution coupled atmosphere-glacier model

    NASA Astrophysics Data System (ADS)

    Aas, K. S.; Dunse, T.; Collier, E.; Schuler, T. V.; Berntsen, T. K.; Kohler, J.; Luks, B.

    2015-10-01

    In this study we simulate the climatic mass balance of Svalbard glaciers with a coupled atmosphere-glacier model with 3 km grid spacing, from September 2003 to September 2013. We find a mean specific net mass balance of -167 mm w.e. yr-1, corresponding to a mean annual mass loss of about 5.7 Gt, with large interannual variability. Our results are compared with a comprehensive set of mass balance, meteorological and satellite measurements. Model temperature biases of 0.17 and -1.9 °C are found at two glacier automatic weather station sites. Simulated climatic mass balance is mostly within about 0.1 m w.e. yr-1 of stake measurements, and simulated winter accumulation at the Austfonna ice cap shows mean absolute errors of 0.05 and 0.06 m w.e. yr-1 when compared to radar-derived values for the selected years 2004 and 2006. Comparison of surface height changes from 2003 to 2008 from model, and satellite altimetry reveals good agreement in both mean values and regional differences. The largest deviations from observations are found for winter accumulation at Hansbreen (up to around 1 m w.e. yr-1), a site where sub-grid topography and wind redistribution of snow are important factors. Comparison with simulations using a 9 km grid spacing reveal considerable differences on regional and local scales. In addition, the 3 km grid spacing allows for a much more detailed comparison with observations than what is possible with a 9 km grid spacing. Further decreasing the grid spacing to 1 km appears to be less significant, although in general precipitation amounts increase with resolution. Altogether, the model compares well with observations and offers possibilities for studying glacier climatic mass balance on Svalbard both historically as well as based on climate projections.

  9. Re-analysis of Alaskan benchmark glacier mass-balance data using the index method

    USGS Publications Warehouse

    Van Beusekom, Ashely E.; O'Nell, Shad R.; March, Rod S.; Sass, Louis C.; Cox, Leif H.

    2010-01-01

    At Gulkana and Wolverine Glaciers, designated the Alaskan benchmark glaciers, we re-analyzed and re-computed the mass balance 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 balance time series more closely. We estimated missing yearly-site data with a new balance 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 mass balances, the re-analyzed balances showed a continuing trend of mass loss. We noted that the time series, and thus our estimate of the cumulative mass 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.

  10. ENSO influence on surface energy and mass balance at Shallap Glacier, Cordillera Blanca, Peru

    NASA Astrophysics Data System (ADS)

    Maussion, F.; Gurgiser, W.; Großhauser, M.; Kaser, G.; Marzeion, B.

    2015-05-01

    The El Niño/Southern Oscillation (ENSO) is a major driver of climate variability in the tropical Andes, where recent Niño and Niña events left an observable footprint on glacier mass balance. The nature and strength of the relationship between ENSO and glacier mass balance, however, varies between regions and time periods, leaving several unanswered questions about its exact mechanisms. The starting point of this study is a four-year long time series of distributed surface energy and mass balance (SEB/SMB) calculated using a process-based model driven by observations at Shallap Glacier (Cordillera Blanca, Peru). These data are used to calibrate a regression-based downscaling model that links the local SEB/SMB fluxes to atmospheric reanalysis variables on a monthly basis, allowing an unprecedented quantification of the ENSO influence on the SEB/SMB at climatological time scales (1980-2013, ERA-Interim period). We find a stronger and steadier anti-correlation between pacific sea surface temperature (SST) and glacier mass balance than previously reported. This relationship is most pronounced during the wet season (December-May) and at low altitudes where Niño (Niña) events are accompanied with a snowfall deficit (excess) and a higher (lower) radiation energy input. We detect a weaker but significant ENSO anti-correlation with total precipitation (Niño dry signal) and positive correlation with the sensible heat flux, but find no ENSO influence on sublimation. Sensitivity analyses comparing several downscaling methods and reanalysis datasets resulted in stable mass balance correlations with pacific SST but also revealed large uncertainties in computing the mass balance trend of the last decades. The newly introduced open-source downscaling tool can be applied easily to other glaciers in the tropics, opening new research possibilities on even longer time scales.

  11. ENSO influence on surface energy and mass balance at Shallap Glacier, Cordillera Blanca, Peru

    NASA Astrophysics Data System (ADS)

    Maussion, F.; Gurgiser, W.; Großhauser, M.; Kaser, G.; Marzeion, B.

    2015-08-01

    The El Niño/Southern Oscillation (ENSO) is a major driver of climate variability in the tropical Andes, where recent Niño and Niña events left an observable footprint on glacier mass balance. The nature and strength of the relationship between ENSO and glacier mass balance, however, varies between regions and time periods, leaving several unanswered questions about its exact mechanisms. The starting point of this study is a 4-year long time series of distributed surface energy and mass balance (SEB/SMB) calculated using a process-based model driven by observations at Shallap Glacier (Cordillera Blanca, Peru). These data are used to calibrate a regression-based downscaling model that links the local SEB/SMB fluxes to atmospheric reanalysis variables on a monthly basis, allowing an unprecedented quantification of the ENSO influence on the SEB/SMB at climatological time scales (1980-2013, ERA-Interim period). We find a stronger and steadier anti-correlation between Pacific sea-surface temperature (SST) and glacier mass balance than previously reported. This relationship is most pronounced during the wet season (December-May) and at low altitudes where Niño (Niña) events are accompanied with a snowfall deficit (excess) and a higher (lower) radiation energy input. We detect a weaker but significant ENSO anti-correlation with total precipitation (Niño dry signal) and positive correlation with the sensible heat flux, but find no ENSO influence on sublimation. Sensitivity analyses comparing several downscaling methods and reanalysis data sets resulted in stable mass balance correlations with Pacific SST but also revealed large uncertainties in computing the mass balance trend of the last decades. The newly introduced open-source downscaling tool can be applied easily to other glaciers in the tropics, opening new research possibilities on even longer time scales.

  12. Siple Coast ice streams reorganization following the reactivation of Kamb Ice Stream tributaries, West Antarctica

    NASA Astrophysics Data System (ADS)

    Christoffersen, P.; Bougamont, M. H.; Price, S. F.; Fricker, H. A.; Tulaczyk, S. M.; Carter, S. P.

    2015-12-01

    Ice streams in Antarctica account for most of the ice volume discharged to the ocean, and their flow variability greatly influences the mass balance of the ice sheet. Today, the Siple Coast region is the only one in West Antarctica to experience a positive mass balance of 36 Gt/yr, as a consequence of the stagnation of Kamb Ice Stream 170 years ago as well as the ongoing slowdown of Whillans Ice Stream. However, this positive trend could be temporary, as reconstructions of past flow show that the Siple Coast ice streams have experienced significant flow variability over the past millennia, with episodes of stagnation typically followed by reactivation on a centennial timescale. The impact that this internally induced variability may have on the future mass balance remains unknown. Here, we use the three-dimensional ice sheet model CISM to study the flow variability of the Ross ice streams over a 250 year period, during which the basal properties controlling ice flow evolve according to the distribution of meltwater in a dynamic, regional hydrological system, coupled to a subglacial till layer. To obtain realistic initial flow conditions, we assimilate the 1997 velocity data available for this region. During the forward simulation, all ice streams undergo dynamic changes, traced to persistently weak bed conditions beneath the tributaries of the currently dormant Kamb Ice Stream. This source of regional instability propagates into the catchments of Whillans as well as Bindschadler ice streams within decades, and re-organizes the flow of all the Ross ice streams within two centuries. Ice piracy from Kamb Ice Stream prolongs the fast flow on Whillans Ice Stream, maintaining its trunk active during the first modeled century. At the same time, ice piracy into the catchment of Bindschadler ice stream reactivates the relict Siple Ice Stream, which significantly reduces the mass balance for this region. The trunk of Kamb Ice Stream reactivates last (during the second half

  13. Response of glacier mass balance to climate change in the Tianshan Mountains during the second half of the twentieth century

    NASA Astrophysics Data System (ADS)

    Liu, Qiao; Liu, Shiyin

    2016-01-01

    Systematic differences in glacier mass balance response to climate warming are apparent in the Tianshan Mountains, which are primarily caused by different climatic regimes and glacier hypsography. Combined mass balance data of nine monitored glaciers in the Tianshan Mountains shows that most glaciers accelerated their mass losing rate since 1970s (averaged from -24.6 mm w.e. a-1 in 1957-1970 to -444.6 mm w.e. a-1 in 1971-2009), but also exhibiting discrepancy and consistency during the second half of the twentieth century. To see their climatic-mass balance relationships, we employ a simple temperature index mass balance model on five well monitored glaciers in Tianshan. The model is calibrated by the observed annual, summer and winter mass balance data over the period of 1957-1980 and validated over 1981-2002. A comparison of modeled and measured annual mass balance yields an overall standard deviation of 0.465 m w.e. during the period of model runs. The calibrated mass balance model is also used to perform sensitivity experiments, which indicates the significant differences of individual glaciers in response to climate changes. This study, for the first time, tests a temperature index mass balance model on the selected observed glaciers in the Tianshan Mountains. Although there exists considerable uncertainties, we propose its potential possibility of improvement and applicability for regional glacier mass balance reconstructions and future predictions.

  14. Ice sheet topography by satellite altimetry

    USGS Publications Warehouse

    Brooks, R.L.; Campbell, W.J.; Ramseier, R.O.; Stanley, H.R.; Zwally, H.J.

    1978-01-01

    The surface elevation of the southern Greenland ice sheet and surface features of the ice 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 ice volume, the mass balance of the present ice sheets could be determined by repetitive mapping of the surface elevation and the surface could be monitored to detect surging or significant changes in ice flow. ?? 1978 Nature Publishing Group.

  15. Monitoring southwest Greenland's ice sheet melt with ambient seismic noise.

    PubMed

    Mordret, Aurélien; Mikesell, T Dylan; Harig, Christopher; Lipovsky, Bradley P; Prieto, Germán A

    2016-05-01

    The Greenland ice sheet presently accounts for ~70% of global ice sheet mass loss. Because this mass 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 ice sheet mass balance is of paramount concern. Spaceborne mass balance 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 ice sheet mass balance. Seasonal loading and unloading of glacial mass 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) ice sheet mass balance, yielding new constraints on ice sheet evolution and its contribution to global sea-level changes. An increased number of seismic stations in the vicinity of ice sheets will enhance our ability to create detailed space-time records of ice mass variations. PMID:27386524

  16. A method to estimate the ice volume and ice-thickness distribution of alpine glaciers

    NASA Astrophysics Data System (ADS)

    Farinotti, Daniel; Huss, Matthias; Bauder, Andreas; Funk, Martin; Truffer, Martin

    Sound knowledge of the ice volume and ice-thickness distribution of a glacier is essential for many glaciological applications. However, direct measurements of ice thickness are laborious, not feasible everywhere and necessarily restricted to a small number of glaciers. In this paper, we present a method to estimate the ice-thickness distribution and the total ice volume of alpine glaciers. This method is based on glacier mass turnover and principles of ice-flow mechanics. The required input data are the glacier surface topography, the glacier outline and a set of borders delineating different 'ice-flow catchments'. Three parameters describe the distribution of the 'apparent mass balance', which is defined as the difference between the glacier surface mass balance and the rate of ice-thickness change, and two parameters define the ice-flow dynamics. The method was developed and validated on four alpine glaciers located in Switzerland, for which the bedrock topography is partially known from radio-echo soundings. The ice thickness along 82 cross-profiles can be reproduced with an average deviation of about 25% between the calculated and the measured ice thickness. The cross-sectional areas differ by less than 20% on average. This shows the potential of the method for estimating the ice-thickness distribution of alpine glaciers without the use of direct measurements.

  17. Laser desorption time-of-flight mass spectrometry of vacuum UV photo-processed methanol ice

    NASA Astrophysics Data System (ADS)

    Paardekooper, D. M.; Bossa, J.-B.; Linnartz, H.

    2016-07-01

    Context. Methanol in the interstellar medium mainly forms upon sequential hydrogenation of solid CO. With typical abundances of up to 15% (with respect to water) it is an important constituent of interstellar ices where it is considered as a precursor in the formation of large and complex organic molecules (COMs), e.g. upon vacuum UV (VUV) photo-processing or exposure to cosmic rays. Aims: This study aims at detecting novel complex organic molecules formed during the VUV photo-processing of methanol ice in the laboratory using a technique more sensitive than regular surface diagnostic tools. In addition, the formation kinetics of the main photo-products of methanol are unravelled for an astronomically relevant temperature (20 K) and radiation dose. Methods: The VUV photo-processing of CH3OH ice is studied by applying laser desorption post-ionisation time-of-flight mass spectrometry (LDPI TOF-MS), and analysed by combining molecule-specific fragmentation and desorption features. Results: The mass spectra correspond to fragment ions originating from a number of previously recorded molecules and from new COMs, such as the series (CO)xH, with x = 3 and y < 3x-1, to which prebiotic glycerin belongs. The formation of these large COMs has not been reported in earlier photolysis studies and suggests that such complex species may form in the solid state under interstellar conditions.

  18. IR-MALDESI MASS SPECTROMETRY IMAGING OF BIOLOGICAL TISSUE SECTIONS USING ICE AS A MATRIX

    PubMed Central

    Robichaud, Guillaume; Barry, Jeremy A.; Muddiman, David C.

    2014-01-01

    Infrared Matrix-Assisted Laser Desorption Electrospray Ionization (IR-MALDESI) Mass Spectrometry imaging of biological tissue sections using a layer of deposited ice as an energy absorbing matrix was investigated. Dynamics of plume ablation were first explored using a nanosecond exposure shadowgraphy system designed to simultaneously collect pictures of the plume with a camera and collect the FT-ICR mass spectrum corresponding to that same ablation event. Ablation of fresh tissue analyzed with and without using ice as a matrix were both compared using this technique. Effect of spot-to-spot distance, number of laser shots per pixel and tissue condition (matrix) on ion abundance was also investigated for 50 µm thick tissue sections. Finally, the statistical method called design of experiments was used to compare source parameters and determine the optimal conditions for IR-MALDESI of tissue sections using deposited ice as a matrix. With a better understanding of the fundamentals of ablation dynamics and a systematic approach to explore the experimental space, it was possible to improve ion abundance by nearly one order of magnitude. PMID:24385399

  19. Regional sea level change in response to ice mass loss in Greenland, the West Antarctic and Alaska

    NASA Astrophysics Data System (ADS)

    Brunnabend, S.-E.; Schröter, J.; Rietbroek, R.; Kusche, J.

    2015-11-01

    Besides the warming of the ocean, sea level is mainly rising due to land ice mass loss of the major ice sheets in Greenland, the West Antarctic, and the Alaskan Glaciers. However, it is not clear yet how these land ice mass losses influence regional sea level. Here, we use the global Finite Element Sea-ice Ocean Model (FESOM) to simulate sea surface height (SSH) changes caused by these ice mass losses and combine it with the passive ocean response to varying surface loading using the sea level equation. We prescribe rates of fresh water inflow, not only around Greenland, but also around the West Antarctic Ice Sheet and the mountain glaciers in Alaska with approximately present-day amplitudes of 200, 100, and 50 Gt/yr, respectively. Perturbations in sea level and in freshwater distribution with respect to a reference simulation are computed for each source separately and in their combination. The ocean mass change shows an almost globally uniform behavior. In the North Atlantic and Arctic Ocean, mass is redistributed toward coastal regions. Steric sea level change varies locally in the order of several centimeters on advective timescales of decades. Steric effects to local sea level differ significantly in different coastal locations, e.g., at North American coastal regions the steric effects may have the same order of magnitude as the mass driven effect, whereas at the European coast, steric effects remain small during the simulation period.

  20. Mass analysis for the Space Station ECLSS using the balance spreadsheet method

    NASA Technical Reports Server (NTRS)

    Chu, Wen-Ho

    1989-01-01

    The balance spreadsheet method is applied to mass analysis of the Environmental Control and Life Support System (ECLSS). The spreadsheet layout reduces the complexity of the ECLSS analysis by concisely defining the sources, sinks, and net changes in mass for each fluid. The analysis method is illustrated by using information from the latest Space Station ECLSS Architectural Control Documents and a given Space Station assembly sequence. The analysis results are plotted and discussed.

  1. Balancing

    NASA Astrophysics Data System (ADS)

    Harteveld, Casper

    At many occasions we are asked to achieve a “balance” in our lives: when it comes, for example, to work and food. Balancing is crucial in game design as well as many have pointed out. In games with a meaningful purpose, however, balancing is remarkably different. It involves the balancing of three different worlds, the worlds of Reality, Meaning, and Play. From the experience of designing Levee Patroller, I observed that different types of tensions can come into existence that require balancing. It is possible to conceive of within-worlds dilemmas, between-worlds dilemmas, and trilemmas. The first, the within-world dilemmas, only take place within one of the worlds. We can think, for example, of a user interface problem which just relates to the world of Play. The second, the between-worlds dilemmas, have to do with a tension in which two worlds are predominantly involved. Choosing between a cartoon or a realistic style concerns, for instance, a tension between Reality and Play. Finally, the trilemmas are those in which all three worlds play an important role. For each of the types of tensions, I will give in this level a concrete example from the development of Levee Patroller. Although these examples come from just one game, I think the examples can be exemplary for other game development projects as they may represent stereotypical tensions. Therefore, to achieve harmony in any of these forthcoming games, it is worthwhile to study the struggles we had to deal with.

  2. REVIEW OF VOLATILE ORGANIC COMPOUND SOURCE APPORTIONMENT BY CHEMICAL MASS BALANCE. (R826237)

    EPA Science Inventory

    The chemical mass balance (CMB) receptor model has apportioned volatile organic compounds (VOCs) in more than 20 urban areas, mostly in the United States. These applications differ in terms of the total fraction apportioned, the calculation method, the chemical compounds used ...