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Sample records for helheim glacier greenland

  1. Interpreting Terminus Fluctuations at Helheim Glacier, Southeast Greenland, through Modeling and Observations

    NASA Astrophysics Data System (ADS)

    Kehrl, L. M.; Joughin, I. R.; Shapero, D.

    2014-12-01

    Marine-terminating outlet glaciers are highly sensitive to changes at the ice-ocean boundary. Changes at the ice-ocean boundary (calving events, submarine melting) can alter the terminus position and thereby the stress balance. If the terminus retreats into deeper water, more of the driving stress must then be balanced by longitudinal stress gradients, which cause the glacier to speed up. This study combines satellite observations and modeling (Elmer/Ice) to investigate the relationship between glacier dynamics and terminus position at Helheim Glacier, southeast Greenland, from 2000-2014. Helheim Glacier retreated about 7 km from 2001-2005 as warm ocean water entered the nearby fjord. From 2005-2006, the glacier re-advanced by 3 km as a floating or near-floating ice tongue formed over the basal overdeepening in front of the glacier terminus. Since then, Helheim's terminus position has remained relatively stable, with terminus fluctuations of < 2 km. Our model experiments consider both large terminus fluctuations (> 2 km) associated with rapid retreat and small terminus fluctuations (< 500 m) associated with individual calving events. We run the model simulations with both a flowline and three-dimensional model to better constrain our uncertainties. Our results show that Helheim Glacier responds rapidly to changes in terminus position of more than a few hundred meters. Small terminus fluctuations can cause velocity variations that extend up to 30 km inland, which roughly corresponds with the spatial extent of the weak bed (20-40 kPa) underneath Helheim Glacier.

  2. Dynamics of Glacier Calving at the Ungrounded Margin of Helheim Glacier, South-East Greenland

    NASA Astrophysics Data System (ADS)

    Murray, T.; Selmes, N.; James, T.; Edwards, S.; Martin, I.; O'Farrell, T.; Aspey, R. A.; Nettles, M.; Rutt, I. C.

    2014-12-01

    Iceberg calving is a key mass loss mechanism for tidewater glaciers, and has been the major contributor to increased contribution to sea-level rise from several regions of Greenland, including the south-east. In summer 2013 we installed a network of 19 GNSS sensors at the margin of Helheim Glacier in south-east Greenland together with 5 oblique cameras to study iceberg calving mechanisms. The network collected data at rates up to every 7 seconds and was designed to be robust to the loss of sensor nodes as the glacier calved. Data collection covered 55 days during July through to early September 2013, and many sensors survived in locations right at the glacier front to the time of iceberg calving. The observation period included a number of significant calving events, and in consequence the glacier retreated ~1.5 km. Throughout the summer the glacier was seen to calve by a process of buoyancy-force-induced bottom-crevassing in which the ice downglacier of flexion zones rotates upwards because it is out of buoyant equilibrium. Calving then occurs back to the flexion zone. This calving process provides a compelling and complete explanation for the data collected. Tracking of the oblique camera images allows identification and characterisation of the flexion zones and their propagation downglacier. Interpretation of the GNSS data and camera data in combination allows us to place constraints on the geometry of the basal cavity that forms beneath the rotating ice downglacier of the flexion zone before calving. Theoretical considerations suggest that the process of bottom crevasse propagation is strongly enhanced when the glacier base is deeper than buoyant equilibrium. We therefore suggest that this calving mechanism will be prevalent whenever this occurs. Interactions between the fjord water and the glacier are likely to enhance calving rates and the process also has implications for mixing in the proglacial fjord.

  3. Dynamics of glacier calving at the ungrounded margin of Helheim Glacier, southeast Greenland

    NASA Astrophysics Data System (ADS)

    Murray, Tavi; Selmes, Nick; James, Timothy D.; Edwards, Stuart; Martin, Ian; O'Farrell, Timothy; Aspey, Robin; Rutt, Ian; Nettles, Meredith; Baugé, Tim

    2015-06-01

    During summer 2013 we installed a network of 19 GPS nodes at the ungrounded margin of Helheim Glacier in southeast Greenland together with three cameras to study iceberg calving mechanisms. The network collected data at rates up to every 7 s and was designed to be robust to loss of nodes as the glacier calved. Data collection covered 55 days, and many nodes survived in locations right at the glacier front to the time of iceberg calving. The observations included a number of significant calving events, and as a consequence the glacier retreated ~1.5 km. The data provide real-time, high-frequency observations in unprecedented proximity to the calving front. The glacier calved by a process of buoyancy-force-induced crevassing in which the ice downglacier of flexion zones rotates upward because it is out of buoyant equilibrium. Calving then occurs back to the flexion zone. This calving process provides a compelling and complete explanation for the data. Tracking of oblique camera images allows identification and characterisation of the flexion zones and their propagation downglacier. Interpretation of the GPS data and camera data in combination allows us to place constraints on the height of the basal cavity that forms beneath the rotating ice downglacier of the flexion zone before calving. The flexion zones are probably formed by the exploitation of basal crevasses, and theoretical considerations suggest that their propagation is strongly enhanced when the glacier base is deeper than buoyant equilibrium. Thus, this calving mechanism is likely to dominate whenever such geometry occurs and is of increasing importance in Greenland.

  4. Dynamics of glacier calving at the ungrounded margin of Helheim Glacier, southeast Greenland.

    PubMed

    Murray, Tavi; Selmes, Nick; James, Timothy D; Edwards, Stuart; Martin, Ian; O'Farrell, Timothy; Aspey, Robin; Rutt, Ian; Nettles, Meredith; Baugé, Tim

    2015-06-01

    During summer 2013 we installed a network of 19 GPS nodes at the ungrounded margin of Helheim Glacier in southeast Greenland together with three cameras to study iceberg calving mechanisms. The network collected data at rates up to every 7 s and was designed to be robust to loss of nodes as the glacier calved. Data collection covered 55 days, and many nodes survived in locations right at the glacier front to the time of iceberg calving. The observations included a number of significant calving events, and as a consequence the glacier retreated ~1.5 km. The data provide real-time, high-frequency observations in unprecedented proximity to the calving front. The glacier calved by a process of buoyancy-force-induced crevassing in which the ice downglacier of flexion zones rotates upward because it is out of buoyant equilibrium. Calving then occurs back to the flexion zone. This calving process provides a compelling and complete explanation for the data. Tracking of oblique camera images allows identification and characterisation of the flexion zones and their propagation downglacier. Interpretation of the GPS data and camera data in combination allows us to place constraints on the height of the basal cavity that forms beneath the rotating ice downglacier of the flexion zone before calving. The flexion zones are probably formed by the exploitation of basal crevasses, and theoretical considerations suggest that their propagation is strongly enhanced when the glacier base is deeper than buoyant equilibrium. Thus, this calving mechanism is likely to dominate whenever such geometry occurs and is of increasing importance in Greenland.

  5. Dynamics of glacier calving at the ungrounded margin of Helheim Glacier, southeast Greenland

    PubMed Central

    Selmes, Nick; James, Timothy D.; Edwards, Stuart; Martin, Ian; O'Farrell, Timothy; Aspey, Robin; Rutt, Ian; Nettles, Meredith; Baugé, Tim

    2015-01-01

    Abstract During summer 2013 we installed a network of 19 GPS nodes at the ungrounded margin of Helheim Glacier in southeast Greenland together with three cameras to study iceberg calving mechanisms. The network collected data at rates up to every 7 s and was designed to be robust to loss of nodes as the glacier calved. Data collection covered 55 days, and many nodes survived in locations right at the glacier front to the time of iceberg calving. The observations included a number of significant calving events, and as a consequence the glacier retreated ~1.5 km. The data provide real‐time, high‐frequency observations in unprecedented proximity to the calving front. The glacier calved by a process of buoyancy‐force‐induced crevassing in which the ice downglacier of flexion zones rotates upward because it is out of buoyant equilibrium. Calving then occurs back to the flexion zone. This calving process provides a compelling and complete explanation for the data. Tracking of oblique camera images allows identification and characterisation of the flexion zones and their propagation downglacier. Interpretation of the GPS data and camera data in combination allows us to place constraints on the height of the basal cavity that forms beneath the rotating ice downglacier of the flexion zone before calving. The flexion zones are probably formed by the exploitation of basal crevasses, and theoretical considerations suggest that their propagation is strongly enhanced when the glacier base is deeper than buoyant equilibrium. Thus, this calving mechanism is likely to dominate whenever such geometry occurs and is of increasing importance in Greenland. PMID:27570721

  6. Ice-front variation and tidewater behavior on Helheim and Kangerdlugssuaq Glaciers, Greenland

    NASA Astrophysics Data System (ADS)

    Joughin, Ian; Howat, Ian; Alley, Richard B.; Ekstrom, Goran; Fahnestock, Mark; Moon, Twila; Nettles, Meredith; Truffer, Martin; Tsai, Victor C.

    2008-03-01

    We used satellite images to examine the calving behavior of Helheim and Kangerdlugssuaq Glaciers, Greenland, from 2001 to 2006, a period in which they retreated and sped up. These data show that many large iceberg-calving episodes coincided with teleseismically detected glacial earthquakes, suggesting that calving-related processes are the source of the seismicity. For each of several events for which we have observations, the ice front calved back to a large, pre-existing rift. These rifts form where the ice has thinned to near flotation as the ice front retreats down the back side of a bathymetric high, which agrees well with earlier theoretical predictions. In addition to the recent retreat in a period of higher temperatures, analysis of several images shows that Helheim retreated in the 20th Century during a warmer period and then re-advanced during a subsequent cooler period. This apparent sensitivity to warming suggests that higher temperatures may promote an initial retreat off a bathymetric high that is then sustained by tidewater dynamics as the ice front retreats into deeper water. The cycle of frontal advance and retreat in less than a century indicates that tidewater glaciers in Greenland can advance rapidly. Greenland's larger reservoir of inland ice and conditions that favor the formation of ice shelves likely contribute to the rapid rates of advance.

  7. TanDEM-X DEMs and feature-tracking of Helheim and Kangerdlugssuaq glaciers in south-east Greenland

    NASA Astrophysics Data System (ADS)

    Bevan, Suzanne; Luckman, Adrian; Murray, Tavi

    2013-04-01

    We use sequences of TanDEM-X acquisitions over 'supersites' Helheim and Kangerdlugssuaq glaciers in south-east Greenland to generate interferometric digital elevation models (DEMs) and to feature-track surface displacement between image acquisitions. The high spatial resolution, day/night, and cloud-penetrating capabilities of the X-band SAR system enabled the production of more than 20 DEMs for each glacier with a spatial resolution of 8 m or better. The DEMs span the period June 2011 to March 2012, at 11-day intervals, with a few breaks. Time-lapse animations of Helheim DEMs reveal the development of troughs in surface elevation close to the front. The troughs propagate down flow and develop into the rifts from which calving takes place. On both glaciers, regions of high variance in elevation can be identified caused by the transit of crevasses. In addition, on Helheim, a 1 km wide band of high variance adjacent to the calving front may be interpreted as the response to tidal forcing of a partially floating tongue. In addition to the DEMs we will also present featured tracked high-quality surface velocity fields at a spatial resolution of 2 m coincident with the DEMs. On Helheim these velocity fields indicate a winter deceleration of less than 10% at a point 4 km behind the calving front.

  8. Response of major Greenland outlet glaciers to oceanic and atmospheric forcing: Results from numerical modeling on Petermann, Jakobshavn and Helheim Glacier.

    NASA Astrophysics Data System (ADS)

    Nick, F. M.; Vieli, A.; Pattyn, F.; Van de Wal, R.

    2011-12-01

    Oceanic forcing has been suggested as a major trigger for dynamic changes of Greenland outlet glaciers. Significant melting near their calving front or beneath the floating tongue and reduced support from sea ice or ice melange in front of their calving front can result in retreat of the terminus or the grounding line, and an increase in calving activities. Depending on the geometry and basal topography of the glacier, these oceanic forcing can affect the glacier dynamic differently. Here, we carry out a comparison study between three major outlet glaciers in Greenland and investigate the impact of a warmer ocean on glacier dynamics and ice discharge. We present results from a numerical ice-flow model applied to Petermann Glacier in the north, Jakobshavn Glacier in the west, and Helheim Glacier in the southeast of Greenland.

  9. Annual down-glacier drainage of lakes and water-filled crevasses at Helheim Glacier, southeast Greenland

    NASA Astrophysics Data System (ADS)

    Everett, A.; Murray, T.; Selmes, N.; Rutt, I. C.; Luckman, A.; James, T. D.; Clason, C.; O'Leary, M.; Karunarathna, H.; Moloney, V.; Reeve, D. E.

    2016-10-01

    Supraglacial lake drainage events are common on the Greenland ice sheet. Observations on the west coast typically show an up-glacier progression of drainage as the annual melt extent spreads inland. We use a suite of remote sensing and modeling techniques in order to study a series of lakes and water-filled crevasses within 20 km of the terminus of Helheim Glacier, southeast Greenland. Automatic classification of surface water areas shows a down-glacier progression of drainage, which occurs in the majority of years between 2007 and 2014. We demonstrate that a linear elastic fracture mechanics model can reliably predict the drainage of the uppermost supraglacial lake in the system but cannot explain the pattern of filling and draining observed in areas of surface water downstream. We propose that the water levels in crevasses downstream of the supraglacial lake can be explained by a transient high-pressure wave passing through the subglacial system following the lake drainage. We support this hypothesis with analysis of the subglacial hydrological conditions, which can explain both the position and interannual variation in filling order of these crevasses. Similar behavior has been observed in association with jökulhaups, surging glaciers, and Antarctic subglacial lakes but has not previously been observed on major outlets of the Greenland ice sheet. Our results suggest that the behavior of near-terminus surface water may differ considerably from that of inland supraglacial lakes, with the potential for basal water pressures to influence the presence of surface water in crevasses close to the terminus of tidewater glaciers.

  10. Continuous Monitoring of Greenland Outlet Glaciers Using an Autonomous Terrestrial LiDAR Scanning System: Design, Development and Testing at Helheim Glacier

    NASA Astrophysics Data System (ADS)

    LeWinter, A. L.; Finnegan, D. C.; Hamilton, G. S.; Stearns, L. A.; Gadomski, P. J.

    2014-12-01

    Greenland's fast-flowing tidewater outlet glaciers play a critical role in modulating the ice sheet's contribution to sea level rise. Increasing evidence points to the importance of ocean forcing at the marine margins as a control on outlet glacier behavior, but a process-based understanding of glacier-ocean interactions remains elusive in part because our current capabilities for observing and quantifying system behavior at the appropriate spatial and temporal scales are limited. A recent international workshop on Greenland's marine terminating glaciers (US CLIVAR, Beverly, MA, June 2013) recommended the establishment of a comprehensive monitoring network covering Greenland's largest outlet glacier-fjord systems to collect long-term time series of critical in situ glaciological, oceanographic and atmospheric parameters needed to understand evolving relationships between different climate forcings and glacier flow. Given the remote locations and harsh environments of Greenland's glacial fjords, the development of robust autonomous instrumentation is a key step in making the observing networks a reality. This presentation discusses the design and development of a fully-autonomous ground-based Light Detection and Ranging (LiDAR) system for monitoring outlet glacier behavior. Initial deployment of the system is planned for spring 2015 at Helheim Glacier in southeast Greenland. The instrument will acquire multi-dimensional point-cloud measurements of the mélange, terminus, and lower-reaches of the glacier. The heart of the system is a long-range, 1064 nm wavelength Terrestrial Laser Scanner (TLS) that we have previously used in campaign-style surveys at Helheim Glacier and at Hubbard Glacier in Alaska. We draw on this experience to design and fabricate the power and enclosure components of the new system, and use previously acquired data from the instrument, collected August 2013 and July 2014 at Helheim, to optimize our data collection strategy and design the data

  11. Tidewater Glacier Velocities from Repeat Ground-Based Terrestrial LiDAR Scanning; Helheim Glacier, Southeast Greenland

    NASA Astrophysics Data System (ADS)

    Finnegan, D. C.; Hamilton, G. S.; Stearns, L. A.; LeWinter, A. L.; Farid, H.; Renedo, H.

    2014-12-01

    Tidewater glaciers exhibit dynamic behaviors across a range of spatial and temporal scales, posing a challenge to both in situ and remote sensing observations. In situ measurements capture variability over very short time intervals, but with limited spatial coverage, and at significant cost and risk to deploy. Conversely, airborne and satellite remote sensing is capable of measuring changes over large spatial extents but at limited temporal resolution. Here we use a near-situ approach to observing dynamic glacier behavior. Terrestrial LiDAR Scanning (TLS) combines the rapid acquisition capabilities of in situ measurements with the broad spatial coverage of traditional remote sensing, and can be carried out from a safe off-ice location. Repeat (30 min) high-resolution, long-range (6-10km) TLS surveys were conducted at Helheim Glacier, southeast Greenland, during July 9-14, 2014, and coincident in situ global positioning system (GPS) observations were acquired close to the glacier terminus. Analysis of these data allows for independent estimates of flow displacement and verification of 3D analytic techniques for quantifying vector motion. These techniques will enable the automated processing of large volumes of repeat scanning data to be collected during planned the deployment of an autonomous version of our LiDAR scanning system.

  12. What can we learn from inverse methods regarding the processes behind the acceleration and retreat of Helheim glacier (Greenland)?

    NASA Astrophysics Data System (ADS)

    Gagliardini, O.; Gillet-chaulet, F.; Martin, N.; Monnier, J.; Singh, J.

    2011-12-01

    Greenland outlet glaciers control the ice discharge toward the sea and the resulting contribution to sea level rise. Physical processes at the root of the observed acceleration and retreat, - decrease of the back force at the calving terminus, increase of basal lubrication and decrease of the lateral friction -, are still not well understood. All these three processes certainly play a role but their relative contributions have not yet been quantified. Helheim glacier, located on the east coast of Greenland, has undergone an enhanced retreat since 2003, and this retreat was concurrent with accelerated ice flow. In this study, the flowline dataset including surface elevation, surface velocity and front position of Helheim from 2001 to 2006 is used to quantify the sensitivity of each of these processes. For that, we used the full-Stokes finite element ice flow model DassFlow/Ice, including adjoint code and full 4d-var data assimilation process in which the control variables are the basal and lateral friction parameters as well as the calving front pressure. For each available date, the sensitivity of each processes is first studied and an optimal distribution is then inferred from the surface measurements. Using this optimal distribution of these parameters, a transient simulation is performed over the whole dataset period. The relative contributions of the basal friction, lateral friction and front back force are then discussed under the light of these new results.

  13. High temporal and spatial resolution inverse modeling of mélange rheology at Helheim Glacier, southeast Greenland

    NASA Astrophysics Data System (ADS)

    James, T.; Borstad, C. P.; Drocourt, Y. J. R.; Murray, T.

    2015-12-01

    The calving of icebergs is responsible for a significant proportion of annual mass loss from marine-terminating glaciers and is believed to be a major factor in the rapid demise of paleo-ice sheets. Iceberg calving indirectly influences buttressing against the ice flow by controlling the structure and extent of ice mélange. This mixture of icebergs and seasonal sea ice that forms at the ice-ocean interface of many fast flowing outlet glaciers is believed to have an important influence on the flow of outlet glaciers. However, its physical properties are not well understood and there is disagreement about how to represent it in models. With recent forecasts anticipating that the majority of mass loss from the Greenland Ice Sheet will be dynamic in origin over the next two centuries, improving understanding of the mélange is key. We applied stereo digital photogrammetric methods to a high temporal and spatial resolution time series of time-lapse imagery to generate velocity fields and elevation models of the terminal region and ice mélange of Helheim glacier in Greenland's southeast. For the first time, we use an inverse method implemented in an ice sheet model to determine the spatial pattern of mélange rheology that is consistent with the velocity fields. We explore the variation of the rheology pattern through time to identify areas that support higher stresses and thus provide greater buttressing.

  14. Calving localization at Helheim Glacier using multiple local seismic stations

    NASA Astrophysics Data System (ADS)

    Mei, M. Jeffrey; Holland, David M.; Anandakrishnan, Sridhar; Zheng, Tiantian

    2017-02-01

    A multiple-station technique for localizing glacier calving events is applied to Helheim Glacier in southeastern Greenland. The difference in seismic-wave arrival times between each pairing of four local seismometers is used to generate a locus of possible event origins in the shape of a hyperbola. The intersection of the hyperbolas provides an estimate of the calving location. This method is used as the P and S waves are not distinguishable due to the proximity of the local seismometers to the event and the emergent nature of calving signals. We find that the seismic waves that arrive at the seismometers are dominated by surface (Rayleigh) waves. The surface-wave velocity for Helheim Glacier is estimated using a grid search with 11 calving events identified at Helheim from August 2014 to August 2015. From this, a catalogue of 11 calving locations is generated, showing that calving preferentially happens at the northern end of Helheim Glacier.

  15. Investigating the Greenland firn aquifer near Helheim Glacier based on geophysical noninvasive methods and in situ measurements

    NASA Astrophysics Data System (ADS)

    Miège, C.; Koenig, L.; Forster, R. R.; Miller, O. L.; Solomon, D. K.; Legchenko, A.; Schmerr, N. C.; Montgomery, L. N.; Brucker, L.

    2015-12-01

    Prior to the onset of seasonal surface melt, widespread perennial aquifers are detected at an average depth of 22 m below the snow surface in the firn of the Greenland ice sheet from airborne radar data. With an elevation range of ~1200-2000 m, the aquifers are mainly located within the percolation zone of the southern and southeastern parts of the ice sheet, in high snow accumulation regions. The impact of the aquifer on Greenland ice sheet hydrology and the direct (or indirect) contribution to sea-level rise remain unconstrained and require further attention. Our study is located on the upper portion of Helheim Glacier in SE Greenland, ~50 km west of the glacier calving front. We first used repeated airborne radar data collected by CReSIS to infer the presence of the firn over the last two decades from missing bed echoes. For 1993-2008, the aquifer remained relatively stable, after 2008 it expanded to higher elevations, and after spring 2012, drainage of its lower-elevation portion is suspected. Based on these initial insights, recent fieldwork was carried out along the surveyed radar line, following an elevation gradient. Geophysical investigation includes seismic refraction and magnetic resonance soundings to complement the radar data and to provide constraints on the base of the aquifer, water volume, and the transition from water-saturated firn to ice. In addition, piezometers and data-logging stations were deployed at point locations to measure hydraulic conductivity, water table vertical fluctuations, and firn temperature. We report on the different techniques used, initial observations made, and present some preliminary interpretations. Water appears to flow laterally in a highly-permeable unconfined aquifer, topographically driven by ice-sheet surface undulations until water encounters local sinks like crevasses. The aquifer impacts on the ice sheet are numerous, including firn densification, alteration of the ice thermal state, and water from the aquifer

  16. Controls on Helheim Glacier calving rates from 2001-2014

    NASA Astrophysics Data System (ADS)

    Stearns, L. A.; Foga, S. C.; Hamilton, G. S.; Straneo, F.; Sutherland, D.; van der Veen, C. J.; Oltmanns, M.; Schild, K. M.

    2014-12-01

    Iceberg calving is an efficient mechanism for ice mass loss. While the physical controls on calving are not well understood, recent field and remote sensing observations from Helheim Glacier, southeast Greenland, suggest calving is dependent on both glacier and fjord conditions. This presentation investigates the sensitivity of calving rates to ice velocity, ocean temperature and mélange composition using a combination of in situ and satellite observations. Ocean properties in Sermilik Fjord for 2009-2014 are reconstructed using mooring data, and an object-based image analysis (OBIA) that inventories icebergs, sea-ice and small icebergs quantifies mélange composition several times a season. Ice velocity from InSAR and optical imagery is used to calculate calving rates and investigate the role of longitudinal gradients on calving. Ice velocity appears to be the dominant control on calving rates at Helheim Glacier. However, calving rates exhibit a complex pattern of seasonal and interannual variability, which does not simply mimic ice velocity patterns. We explore the relative roles of ocean properties, glacier geometry, and mélange composition on calving rates from 2001-2014 in order to improve physically-based glacier models.

  17. Towards a robust calving and melt-history for Helheim Glacier, SE Greenland, for the last 100 years

    NASA Astrophysics Data System (ADS)

    Andersen, T. J.; Ellegaard, M.; Markussen, T. N.

    2013-12-01

    Observations of increased ice-discharge from tidewater glaciers in Greenland in the early and mid 2000s has led to concern about a possible rapid loss of ice from the ice sheet in a scenario with increasing air and ocean water temperatures. In order to evaluate the strength and uniqueness of the observed increase a robust data-set on the temporal variation of calving and melt is strongly needed. The only reliable data prior to the period of aerial photographs and instrumental observations is the archive preserved at the seabed in the fjords and coastal waters off the ice sheet. Establishment of core-chronology is central in studies of these archives and is based on Pb-210 dating which will reach approx. 100 years back in time. Establishment of a detailed and accurate core-chronology by means of Pb-210 dating and Cs-137 peaks is by no means a trivial task in environments influenced by episodic deposition of ice-rafted debris (IRD). The deposition will have a relatively large component of random variability which could be mistaken for actual changes in sedimentation rate, especially so if only one or a few cores are analyzed. To increase the reliability of the calving reconstruction, a total of 13 cores have been sampled in this study in Sermilik Fjord in August 2012 at depths between approximately 700 to 900 m. Eleven of the cores are from within the central basin north of 66 degrees North and two are from the outer part of the fjord south of that line. CTD-profiles and measurements of floc size in situ indicate that the sedimentation is significantly influenced by deposition of IRD and temporal changes in sediment accumulation rates will therefore be examined for all the cores. The cores are also being analyzed for their content of dinoflagellate cysts and diatoms in order to examine possible temporal changes in ocean water temperature in the fjord. So far (August 2013) six cores have been studied and the total average accumulation rate for each year since 1925 has

  18. Glaciers of Greenland

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1995-01-01

    Landsat imagery, combined with aerial photography, sketch maps, and diagrams, is used as the basis for a description of the geography, climatology, and glaciology, including mass balance, variation, and hazards, of the Greenland ice sheet and local ice caps and glaciers. The Greenland ice sheet, with an estimated area of 1,736,095+/-100 km2 and volume of 2,600,000 km3, is the second largest glacier on the planet and the largest relict of the Ice Age in the Northern Hemisphere. Greenland also has 48,599+/-100 km2 of local ice caps and other types of glaciers in coastal areas and islands beyond the margin of the ice sheet.

  19. Calving dynamics at Helheim Glacier from a high-resolution observational network.

    NASA Astrophysics Data System (ADS)

    Selmes, Nick; Aspey, Robin; Baugé, Tim; Bevan, Suzanne; Edwards, Stuart; Everett, Alistair; James, Timothy; Loskot, Pavel; Luckman, Adrian; Martin, Ian; Murray, Tavi; O'Farrell, Tim; Rutt, Ian

    2014-05-01

    Calving glaciers play a crucial role in the mass balance of the Greenland Ice Sheet; acceleration of these glaciers results in increased mass loss from the ice sheet interior and a corresponding rise in sea level. Understanding the controls on calving is crucial for predicting the dynamic response of tidewater glaciers to environmental change, but understanding of calving is hindered by the difficulty of obtaining appropriate field measurements, and by the complexity of the system being observed. We designed and deployed a wireless network of GPS nodes which transmit to off-glacier base stations every few seconds, allowing observations right up to node loss through calving. We ran a network of 20 sensors over the period July - September 2013 on the highly crevassed surface of Helheim Glacier, one of the largest and fastest flowing of the Greenland outlets. Topographic change, additional velocities, and calving flux were provided by two sets of stereo time-lapse cameras, TanDEM-X satellite imagery, repeat airborne lidar, and airborne and spaceborne optical remotely-sensed imagery. At the start of our field season we observed the expression on the fjord surface of a point-source subglacial meltwater plume. We monitored the evolution of the plume and its effect on the exposed calving face and ice mélange from time-lapse cameras, optical remotely-sensed imagery and lidar data. We compare these observations to our record of frontal positions to study the plume's role in controlling the spatial extent of iceberg calving. Our 53 day study period contained several large calving events which resulted in frontal retreat of ~1.5 km. We present the glacier's dynamic and topographic response to these calving events through this very large and rich dataset. Typically the glacier ice flows down slope and speeds up as ice progresses towards the calving front, with notable acceleration after each calving event. Intriguingly we see periods where sensors behave in unexpected ways

  20. Greenland Glacier Albedo Variability

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The program for Arctic Regional Climate Assessment (PARCA) is a NASA-funded project with the prime goal of addressing the mass balance of the Greenland ice sheet. Since the formal initiation of the program in 1995, there has been a significant improvement in the estimates of the mass balance of the ice sheet. Results from this program reveal that the high-elevation regions of the ice sheet are approximately in balance, but the margins are thinning. Laser surveys reveal significant thinning along 70 percent of the ice sheet periphery below 2000 m elevations, and in at least one outlet glacier, Kangerdlugssuaq in southeast Greenland, thinning has been as much as 10 m/yr. This study examines the albedo variability in four outlet glaciers to help separate out the relative contributions of surface melting versus ice dynamics to the recent mass balance changes. Analysis of AVHRR Polar Pathfinder albedo shows that at the Petermann and Jakobshavn glaciers, there has been a negative trend in albedo at the glacier terminus from 1981 to 2000, whereas the Stor+strommen and Kangerdlugssuaq glaciers show slightly positive trends in albedo. These findings are consistent with recent observations of melt extent from passive microwave data which show more melt on the western side of Greenland and slightly less on the eastern side. Significance of albedo trends will depend on where and when the albedo changes occur. Since the majority of surface melt occurs in the shallow sloping western margin of the ice sheet where the shortwave radiation dominates the energy balance in summer (e.g. Jakobshavn region) this region will be more sensitive to changes in albedo than in regions where this is not the case. Near the Jakobshavn glacier, even larger changes in albedo have been observed, with decreases as much as 20 percent per decade.

  1. Tidal analysis of GNSS data from a high resolution sensor network at Helheim Glacier

    NASA Astrophysics Data System (ADS)

    Martin, Ian; Aspey, Robin; Baugé, Tim; Edwards, Stuart; Everett, Alistair; James, Timothy; Loskot, Pavel; Murray, Tavi; O'Farrell, Tim; Rutt, Ian

    2014-05-01

    Changes in Greenland and Antarctic ice sheets due to ice flow/ice-berg calving are a major uncertainty affecting sea-level rise forecasts. Latterly GNSS (Global Navigation Satellite Systems) have been employed extensively to monitor such glacier dynamics. Until recently however, the favoured methodology has been to deploy sensors onto the glacier surface, collect data for a period of time, then retrieve and download the sensors. This approach works well in less dynamic environments where the risk of sensor loss is low. In more extreme environments e.g. approaching the glacial calving front, the risk of sensor loss and hence data loss increases dramatically. In order to provide glaciologists with new insights into flow dynamics and calving processes we have developed a novel sensor network to increase the robustness of data capture. We present details of the technological requirements for an in-situ Zigbee wireless streaming network infrastructure supporting instantaneous data acquisition from high resolution GNSS sensors thereby increasing data capture robustness. The data obtained offers new opportunities to investigate the interdependence of mass flow, uplift, velocity and geometry and the network architecture has been specifically designed for deployment by helicopter close to the calving front to yield unprecedented detailed information. Following successful field trials of a pilot three node network during 2012, a larger 20 node network was deployed on the fast-flowing Helheim glacier, south-east Greenland over the summer months of 2013. The utilisation of dual wireless transceivers in each glacier node, multiple frequencies and four 'collector' stations located on the valley sides creates overlapping networks providing enhanced capacity, diversity and redundancy of data 'back-haul', even close to 'floor' RSSI (Received Signal Strength Indication) levels around -100 dBm. Data loss through radio packet collisions within sub-networks are avoided through the

  2. Modelling Greenland Outlet Glaciers

    NASA Technical Reports Server (NTRS)

    vanderVeen, Cornelis; Abdalati, Waleed (Technical Monitor)

    2001-01-01

    The objective of this project was to develop simple yet realistic models of Greenland outlet glaciers to better understand ongoing changes and to identify possible causes for these changes. Several approaches can be taken to evaluate the interaction between climate forcing and ice dynamics, and the consequent ice-sheet response, which may involve changes in flow style. To evaluate the icesheet response to mass-balance forcing, Van der Veen (Journal of Geophysical Research, in press) makes the assumption that this response can be considered a perturbation on the reference state and may be evaluated separately from how this reference state evolves over time. Mass-balance forcing has an immediate effect on the ice sheet. Initially, the rate of thickness change as compared to the reference state equals the perturbation in snowfall or ablation. If the forcing persists, the ice sheet responds dynamically, adjusting the rate at which ice is evacuated from the interior to the margins, to achieve a new equilibrium. For large ice sheets, this dynamic adjustment may last for thousands of years, with the magnitude of change decreasing steadily over time as a new equilibrium is approached. This response can be described using kinematic wave theory. This theory, modified to pertain to Greenland drainage basins, was used to evaluate possible ice-sheet responses to perturbations in surface mass balance. The reference state is defined based on measurements along the central flowline of Petermann Glacier in north-west Greenland, and perturbations on this state considered. The advantage of this approach is that the particulars of the dynamical flow regime need not be explicitly known but are incorporated through the parameterization of the reference ice flux or longitudinal velocity profile. The results of the kinematic wave model indicate that significant rates of thickness change can occur immediately after the prescribed change in surface mass balance but adjustments in flow

  3. Melting beneath Greenland outlet glaciers and ice streams

    NASA Astrophysics Data System (ADS)

    Alexander, David; Perrette, Mahé; Beckmann, Johanna

    2015-04-01

    Basal melting of fast-flowing Greenland outlet glaciers and ice streams due to frictional heating at the ice-bed interface contributes significantly to total glacier mass balance and subglacial meltwater flux, yet modelling this basal melt process in Greenland has received minimal research attention. A one-dimensional dynamic ice-flow model is calibrated to the present day longitudinal profiles of 10 major Greenland outlet glaciers and ice streams (including the Jakobshavn Isbrae, Petermann Glacier and Helheim Glacier) and is validated against published ice flow and surface elevation measurements. Along each longitudinal profile, basal melt is calculated as a function of ice flow velocity and basal shear stress. The basal shear stress is dependent on the effective pressure (difference between ice overburden pressure and water pressure), basal roughness and a sliding parametrization. Model output indicates that where outlet glaciers and ice streams terminate into the ocean with either a small floating ice tongue or no floating tongue whatsoever, the proportion of basal melt to total melt (surface, basal and submarine melt) is 5-10% (e.g. Jakobshavn Isbrae; Daugaard-Jensen Glacier). This proportion is, however, negligible where larger ice tongues lose mass mostly by submarine melt (~1%; e.g. Nioghalvfjerdsfjorden Glacier). Modelled basal melt is highest immediately upvalley of the grounding line, with contributions typically up to 20-40% of the total melt for slippery beds and up to 30-70% for resistant beds. Additionally, modelled grounding line and calving front migration inland for all outlet glaciers and ice streams of hundreds of metres to several kilometres occurs. Including basal melt due to frictional heating in outlet glacier and ice stream models is important for more accurately modelling mass balance and subglacial meltwater flux, and therefore, more accurately modelling outlet glacier and ice stream dynamics and responses to future climate change.

  4. Simulating rapid changes of a Greenland outlet glacier using an embedded numerical model

    NASA Astrophysics Data System (ADS)

    Weitz, N. A.; Hamilton, G. S.; Fastook, J.

    2012-12-01

    The Greenland Ice Sheet loses most of its mass through outlet glaciers, meaning the behavior of outlet glaciers is an important factor to include in future sea level estimations. Between 2001 and 2006, Helheim Glacier in Southeast Greenland rapidly retreated about 7 km, nearly doubled its flow velocities from 6 km yr-1 to 11 km yr-1, and thinned by more than 200 m. Numerous other outlet glaciers around the coast of Greenland underwent similar changes at approximately the same time, yet the causes are not fully known. Outlet glacier dynamics are complex and several factors, acting in combination or separately, can trigger terminus retreat. Here, we investigate possible triggering mechanisms for the rapid retreat of Helheim Glacier using the embedded grid capabilities of the University of Maine Ice Sheet Model (UMISM). Ice-sheet physics based on the shallow ice approximation are solved with the finite element method. The model operates in two horizontal dimensions, rather than a flowline, in order to capture the effects of complex subsurface geometries. We model Helheim Glacier on a high resolution 750 m grid embedded in a coarser (15 km) solution of the whole Greenland Ice Sheet. Changes in input variables affect model outcomes in the following ways: 1) Warmer air temperatures change the mass balance which in turn alters the surface profile, which influences flow velocities and ice flux towards the terminus. 2) Increased surface melt water production can lead to more calving events in the terminus region due to hydrofracturing. 3) Enhanced surface melt water penetrating to the glacier bed can lead to enhanced sliding over the bedrock. 4) An increase in ocean temperature enhances the melt rate at the grounding line which can lead to changes in terminus position. A subsequent reduction of backstress at the calving front leads to an increase in flow velocity and dynamic thinning of the glacier. Our simulations show that three different triggering mechanisms could have

  5. Calving Signature in Ocean Waves: Helheim Glacier and Sermilik Fjord Dynamics

    NASA Astrophysics Data System (ADS)

    Vankova, I.; Holland, D.

    2015-12-01

    In this work, we investigate the characteristics of calving on Helheim glacier from data recorded on an array of five high frequency pressure meters placed along Sermilik fjord. Calving generated tsunami waves were recorded and used to construct a calving event catalog and to characterize the post-calving ocean state. Calving on Helheim is highly seasonal: it onsets after months of inactivity in early spring, immediately following the rise of daily average temperatures above freezing point, which indicates the potentially dominant role of meltwater in the calving mechanism. Tidal phase and amplitude, ocean temperature variations or surges did not seem to be significant calving factors. In the ocean spectra, we observe discrete peaks between 0.4 to 6 mHz associated with calving events. These peak frequencies are consistent among all the events and they travel as propagating modes up and down the fjord for several hours while being slowly radiated away to the open ocean, an observation which we support with a model. Large part of the spectrum is trapped in evanescent modes or is quickly dissipated. These observations are relevant for our understanding of the time scale and rate of mixing in glacier fjords, and eventually for improving boundary conditions for ocean models.

  6. Brief communication: Getting Greenland's glaciers right - a new data set of all official Greenlandic glacier names

    NASA Astrophysics Data System (ADS)

    Bjørk, A. A.; Kruse, L. M.; Michaelsen, P. B.

    2015-12-01

    Place names in Greenland can be difficult to get right, as they are a mix of Greenlandic, Danish, and other foreign languages. In addition, orthographies have changed over time. With this new data set, we give the researcher working with Greenlandic glaciers the proper tool to find the correct name for glaciers and ice caps in Greenland and to locate glaciers described in the historic literature with the old Greenlandic orthography. The data set contains information on the names of 733 glaciers, 285 originating from the Greenland Ice Sheet (GrIS) and 448 from local glaciers and ice caps (LGICs).

  7. Brief Communication: 2014 velocity and flux for five major Greenland outlet glaciers using ImGRAFT and Landsat-8

    NASA Astrophysics Data System (ADS)

    Messerli, A.; Karlsson, N. B.; Grinsted, A.

    2014-12-01

    This study presents average velocity fields, mass flux estimates and central flowline profiles for five major Greenland outlet glaciers; Jakobshavn Isbræ, Nioghalvfjerdsbræ, Kangerdlugssuaq, Helheim and Petermann glaciers, spanning the period (August) 2013-(September) 2014. The results are produced by the feature tracking toolbox, ImGRAFT using Landsat-8, panchromatic data. The resulting velocity fields agree with the findings of existing studies. Furthermore, our results show an unprecedented speed of over 50 m day-1 at Jakobshavn Isbræ as it continues to retreat. All the processed data will be freely available for download at http://imgraft.glaciology.net.

  8. Earthshots: Satellite images of environmental change – Petermann Glacier, Greenland

    USGS Publications Warehouse

    Adamson, Thomas

    2016-01-01

    This calving is normal, but it’s worth watching Petermann and other Greenland glaciers closely. Petermann is one of the major marine-terminating glaciers of Greenland. Ice loss from the Greenland Ice Sheet has increased recently. An article in Nature concluded that climate change may cause Petermann and other Greenland glaciers to contribute to sea level rise. Landsat helps glaciologists keep a close eye on this remote but significant glacier.

  9. Greenland's pronounced glacier retreat not irreversible

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2012-02-01

    In recent decades, the combined forces of climate warming and short-term variability have forced the massive glaciers that blanket Greenland into retreat, with some scientists worrying that deglaciation could become irreversible. The short history of detailed glacier observations, however, makes pinning the ice loss to either short-term dynamics or long-term change difficult. Research by Young et al. detailing the effects of two bouts of sudden and temporary cooling during an otherwise warm phase in Greenland's climate history could help answer that question by showing just how heavy a hand short-term variability can have in dictating glacier dynamics. Along the western edge of Greenland the massive Jakobshavn Isbræ glacier reaches out to the coast, its outflow dropping icebergs into Baffin Bay during the summer months. Flanking the glacier's tongue are the Tasiussaq and Marrait moraines—piles of rock marking the glacier's former extent. Researchers suspected the moraines were tied to two periods of abrupt cooling that hit Greenland 9300 and 8200 years ago, and that association was reinforced by the authors' radiocarbon and beryllium isotope analyses of the area surrounding the moraines. Beryllium-10 forms when cosmic radiation travels through the atmosphere and strikes the Earth's surface, with surface rock concentrations indicating how long it has been ice-free.

  10. Complex Greenland outlet glacier flow captured.

    PubMed

    Aschwanden, Andy; Fahnestock, Mark A; Truffer, Martin

    2016-02-01

    The Greenland Ice Sheet is losing mass at an accelerating rate due to increased surface melt and flow acceleration in outlet glaciers. Quantifying future dynamic contributions to sea level requires accurate portrayal of outlet glaciers in ice sheet simulations, but to date poor knowledge of subglacial topography and limited model resolution have prevented reproduction of complex spatial patterns of outlet flow. Here we combine a high-resolution ice-sheet model coupled to uniformly applied models of subglacial hydrology and basal sliding, and a new subglacial topography data set to simulate the flow of the Greenland Ice Sheet. Flow patterns of many outlet glaciers are well captured, illustrating fundamental commonalities in outlet glacier flow and highlighting the importance of efforts to map subglacial topography. Success in reproducing present day flow patterns shows the potential for prognostic modelling of ice sheets without the need for spatially varying parameters with uncertain time evolution.

  11. Complex Greenland outlet glacier flow captured

    NASA Astrophysics Data System (ADS)

    Aschwanden, Andy; Fahnestock, Mark A.; Truffer, Martin

    2016-02-01

    The Greenland Ice Sheet is losing mass at an accelerating rate due to increased surface melt and flow acceleration in outlet glaciers. Quantifying future dynamic contributions to sea level requires accurate portrayal of outlet glaciers in ice sheet simulations, but to date poor knowledge of subglacial topography and limited model resolution have prevented reproduction of complex spatial patterns of outlet flow. Here we combine a high-resolution ice-sheet model coupled to uniformly applied models of subglacial hydrology and basal sliding, and a new subglacial topography data set to simulate the flow of the Greenland Ice Sheet. Flow patterns of many outlet glaciers are well captured, illustrating fundamental commonalities in outlet glacier flow and highlighting the importance of efforts to map subglacial topography. Success in reproducing present day flow patterns shows the potential for prognostic modelling of ice sheets without the need for spatially varying parameters with uncertain time evolution.

  12. Complex Greenland outlet glacier flow captured

    PubMed Central

    Aschwanden, Andy; Fahnestock, Mark A.; Truffer, Martin

    2016-01-01

    The Greenland Ice Sheet is losing mass at an accelerating rate due to increased surface melt and flow acceleration in outlet glaciers. Quantifying future dynamic contributions to sea level requires accurate portrayal of outlet glaciers in ice sheet simulations, but to date poor knowledge of subglacial topography and limited model resolution have prevented reproduction of complex spatial patterns of outlet flow. Here we combine a high-resolution ice-sheet model coupled to uniformly applied models of subglacial hydrology and basal sliding, and a new subglacial topography data set to simulate the flow of the Greenland Ice Sheet. Flow patterns of many outlet glaciers are well captured, illustrating fundamental commonalities in outlet glacier flow and highlighting the importance of efforts to map subglacial topography. Success in reproducing present day flow patterns shows the potential for prognostic modelling of ice sheets without the need for spatially varying parameters with uncertain time evolution. PMID:26830316

  13. Ocean impact on Nioghalvfjerdsfjorden Glacier, Northeast Greenland

    NASA Astrophysics Data System (ADS)

    Schaffer, Janin; Kanzow, Torsten; von Appen, Wilken-Jon; Mayer, Christoph

    2017-04-01

    The ocean plays an important role in modulating the mass balance of the Greenland Ice Sheet by delivering heat to the marine-terminating outlet glaciers around Greenland. The largest of three outlet glaciers draining the Northeast Greenland Ice Stream is Nioghalvfjerdsfjorden Glacier (also referred to as 79 North Glacier). Historic observations showed that warm waters of Atlantic origin are present in the subglacial cavity below the 80 km long floating ice tongue of the Nioghalvfjerdsfjorden Glacier and cause strong basal melt at the grounding line, but to date it has been unknown how those warm water enter the cavity. In order to understand how Atlantic origin waters carry heat into the subglacial cavity beneath Nioghalvfjerdsfjorden Glacier, we performed bathymetric, hydrographic, and velocity observations in the vicinity of the main glacier calving front aboard RV Polarstern in summer 2016. The bathymetric multibeam data shows a 500 m deep and 2 km narrow passage downstream of a 310 m deep sill. This turned out to be the only location deep enough for an exchange of Atlantic waters between the glacier cavity and the continental shelf. Hydrographic and velocity measurements revealed a density driven plume in the vicinity of the glacier calving front causing a rapid flow of waters of Atlantic origin warmer 1°C into the subglacial cavity through the 500 m deep passage. In addition, glacially modified waters flow out of the glacier cavity below the 80 m deep ice base. In the vicinity of the glacier, the glacially modified waters form a distinct mixed layer situated above the Atlantic waters and below the ambient Polar water. At greater distances from the glacier this layer is eroded by lateral mixing with ambient water. Based on our observations we will present an estimate of the ocean heat transport into the subglacial cavity. In comparison with historic observations we find an increase in Atlantic water temperatures throughout the last 20 years. The resulting

  14. On the Influence of the NAO on Outlet Glacier Stability in SE Greenland during the Past 100 Years

    NASA Astrophysics Data System (ADS)

    Andresen, C. S.

    2014-12-01

    The Greenland Ice sheet has gained massive attention in recent years due to a sudden increase in mass loss at the onset of this century. A significant part of this mass loss has been attributed to increased ice discharge at the margin through iceberg calving from marine-terminating outlet glaciers. However, due to the lack of instrumental data beyond the past 20-30 years it is difficult to evaluate if this was an outstanding event or if it was part of a recurring phenomenon acting on inter-annual, inter-decadal or centennial timescales. In order to improve understanding of the timescales involved in glacier changes and on the influence of ocean and atmosphere variability we investigate sediment archives from fjords with marine terminating glaciers. Near the glacier margin the sedimentation rates are relatively high due to glacial flour input and rafting of iceberg debris. Our studies of several sediment cores obtained from Sermilik Fjord by Helheim Glacier in Southeast Greenland has allowed us to reconstruct glacier calving, shelf temperature and fjord water renewal rate for the past 100 years. These studies show that dominant modes of climate variability, i.e. the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation, affect ocean properties near the glacier and that the recorded variability concurs with reconstructed outlet glacier changes. This presentation provides an overview these studies.

  15. Distinct patterns of seasonal Greenland glacier velocity.

    PubMed

    Moon, Twila; Joughin, Ian; Smith, Ben; van den Broeke, Michiel R; van de Berg, Willem Jan; Noël, Brice; Usher, Mika

    2014-10-28

    Predicting Greenland Ice Sheet mass loss due to ice dynamics requires a complete understanding of spatiotemporal velocity fluctuations and related control mechanisms. We present a 5 year record of seasonal velocity measurements for 55 marine-terminating glaciers distributed around the ice sheet margin, along with ice-front position and runoff data sets for each glacier. Among glaciers with substantial speed variations, we find three distinct seasonal velocity patterns. One pattern indicates relatively high glacier sensitivity to ice-front position. The other two patterns are more prevalent and appear to be meltwater controlled. These patterns reveal differences in which some subglacial systems likely transition seasonally from inefficient, distributed hydrologic networks to efficient, channelized drainage, while others do not. The difference may be determined by meltwater availability, which in some regions may be influenced by perennial firn aquifers. Our results highlight the need to understand subglacial meltwater availability on an ice sheet-wide scale to predict future dynamic changes.

  16. ASTER Views Large Calving Event at Petermann Glacier, Greenland

    NASA Image and Video Library

    2010-08-12

    This image of Petermann Glacier and the new iceberg was acquired from NASA Terra spacecraft on Aug. 12, 2010. On Aug. 5, 2010, an enormous chunk of ice broke off the Petermann Glacier along the northwestern coast of Greenland.

  17. Pathways of Petermann Glacier's Meltwaters, Greenland

    NASA Astrophysics Data System (ADS)

    Heuzé, C.; Wahlin, A.; Johnson, H. L.; Muenchow, A.

    2016-02-01

    Radar and satellite observations suggest that the floating ice shelf of Petermann glacier, north Greenland, loses up to 80% of its mass through basal melting, caused by the intrusion of warm Atlantic water into the fjord and under the ice shelf. Although Greenland meltwaters are key to sea level rise projections and can potentially disrupt the whole ocean circulation, the fate of Petermann's glacial meltwater is still largely unknown. It is investigated here, using hydrographic observations collected during a research cruise onboard I/B Oden in August 2015. Two layers are found: one at 200 m (i.e. terminus depth) mostly on the eastern side of the fjord where a calving event occurred this summer, and one around 500 m depth (i.e. the grounding line) on the western side. At the sill, approximately 3 mSv of freshwater leave the fjord around 150 m on the eastern side. On the western side, a more complex circulation occurs as waters intrude in. Outside of the fjord in Hall Basin, only one layer is found, around 300 m, but its oxygen content and T-S properties suggests it is a mixture between Petermann's meltwater, meltwater from the neighbouring glaciers, surface run-off and sea ice. As Atlantic water warms up, it is key to monitor Greenland melting glaciers to properly assess sea level rise.

  18. Velocity Estimates of Fast-Moving Outlet Glaciers on the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Abdalati, Waleed; Krabill, W. B.

    1998-01-01

    In recent years, airborne laser altimetry has been used with great success to investigate the mass balance characteristics of the Greenland ice sheet. One spinoff of this activity has been the application of these measurements to the study of surface velocities in some of Greenland's fast-moving drainage glaciers. This is accomplished by tracking the motion of elevation features, primarily crevasses, in pairs of aircraft laser altimetry surveys. Detailed elevation measurements are made along or across glaciers of interest with a scanning swath of 150 to 200 meters, and the surveys are repeated several days later, typically to within better than 50 meters of the previous flight line. Surface elevation features are identified in each image, and their offsets are compared yielding detailed velocities over narrow regions. During the 1998 field season, repeat flights were made over three glaciers for the purpose of estimating their surface velocities. These were the Kangerdlugssuaq and Helheim glaciers on the east coast and the Jakobshavn Isbrae on the west coast. Each flows at such high speeds (on the order of a few kilometers per year) that their flow rates are difficult to assess by means of radar interferometry. The flexibility of the aircraft platform, however, allows for detailed measurements of the elevation and flow of these drainage areas, which are responsible for a significant portion of the ice discharge from the Greenland ice sheet. Velocity estimates for transects that span these glaciers will be presented, and where the ice thickness values are available (provided by researchers from the University of Kansas) the fluxes will be calculated.

  19. Velocity Estimates of Fast-Moving Outlet Glaciers on the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Abdalati, Waleed; Krabill, W. B.

    1998-01-01

    In recent years, airborne laser altimetry has been used with great success to investigate the mass balance characteristics of the Greenland ice sheet. One spinoff of this activity has been the application of these measurements to the study of surface velocities in some of Greenland's fast-moving drainage glaciers. This is accomplished by tracking the motion of elevation features, primarily crevasses, in pairs of aircraft laser altimetry surveys. Detailed elevation measurements are made along or across glaciers of interest with a scanning swath of 150 to 200 meters, and the surveys are repeated several days later, typically to within better than 50 meters of the previous flight line. Surface elevation features are identified in each image, and their offsets are compared yielding detailed velocities over narrow regions. During the 1998 field season, repeat flights were made over three glaciers for the purpose of estimating their surface velocities. These were the Kangerdlugssuaq and Helheim glaciers on the east coast and the Jakobshavn Isbrae on the west coast. Each flows at such high speeds (on the order of a few kilometers per year) that their flow rates are difficult to assess by means of radar interferometry. The flexibility of the aircraft platform, however, allows for detailed measurements of the elevation and flow of these drainage areas, which are responsible for a significant portion of the ice discharge from the Greenland ice sheet. Velocity estimates for transects that span these glaciers will be presented, and where the ice thickness values are available (provided by researchers from the University of Kansas) the fluxes will be calculated.

  20. Processing time-series point clouds to reveal strain conditions of the Helheim Glacier terminus and its adjacent mélange

    NASA Astrophysics Data System (ADS)

    Byers, L. C.; Stearns, L. A.; Finnegan, D. C.; LeWinter, A. L.; Gadomski, P. J.; Hamilton, G. S.

    2014-12-01

    Flow near the termini of tidewater glaciers varies over short time-scales due to mechanisms that are poorly understood. Repeat observations with high temporal and spatial resolution, recorded around the terminus, are required to better understand the processes that control flow variability. Progress in light detection and ranging (LiDAR) technology permit such observations of the near-terminus and the pro-glacial ice mélange, though standard workflows for quantifying deformation from point clouds currently do not exist. Here, we test and develop methods for processing displacements from LiDAR data of complexly deforming bodies. We use data collected at 30-minute intervals over three-days in August 2013 at Helheim Glacier, Greenland by a long-range (6-10 km), 1064 nm wavelength Terrestrial LiDAR Scanner (TLS). The total area of coverage was ~25 km2. Distributed shear in glaciers prevents a simple transformation for aligning repeat point clouds, but within small regions (~100 m2) strain is assumed to be minor between scans. Registering a large number of these individual regions, subset from the full point-cloud, results in reduced alignment errors. By subsetting in a regular grid, rasters of velocities between scans are created. However, using data-dependent properties such as point density causes the generation of unevenly spaced velocity estimations, which can locally improve resolution or decrease registration errors. The choice of subsets therefore controls the output product's resolution and accuracy. We test how the spatial segmentation scheme affects the displacement results and alignment errors, finding that displacements can be quantified with limited assumption of the true value of displacement for the subset, barring great morphological changes. By identifying areas that do not deform over the temporal domain of the dataset, and using these as the subsets to align, it should be possible to deduce which structures are accommodating strain. This allows for

  1. Using ISSM to Simulate the LIA to Present Ice Margin Change at Upernavik Glacier, Greenland

    NASA Astrophysics Data System (ADS)

    Haubner, K.; Larour, E. Y.; Box, J.; Schlegel, N.; Larsen, S. H.; Kjeldsen, K. K.; Kjaer, K. H.

    2015-12-01

    The possibility for rapid melting of the Greenland ice sheet ranks among the most serious societal climate threats. This project puts the rate of contemporary climate change-driven Greenland ice mass change in a temporal context, by simulating the Greenland ice sheet margin throughout the Holocene and comparing the results with past ice margin positions (e.g. Andresen et al., 2014; Bjørk et al., 2012) and records of glacier activity based on fjord sediment strata (Andresen et al. 2012). Here we show first steps to achieve this goal and model the evolution of the Upernavik Isstrøm, a set of marine-terminating glaciers in Northwest Greenland, during the 20thcentury, using the Ice Sheet System Model (ISSM) (Larour et. al 2012). The simulation runs from 1900, shortly after the Little Ice Age (LIA), to year 2013, initialized using trimline data marking the former extent of the ice sheet and forced by a surface mass balance reconstruction after Box (2013). We address uncertainties in ice front positions and thickness by comparing our simulation output with present ice margin positions in the area. Finally, we investigate the possibility of simulating historic changes at ice sheet margins with this finite element ice sheet model. Andresen, C. S., Kjeldsen, K. K., Harden, B., Nørgaard-Pedersen, N. and Kjær, K. H. 2014. Outlet glacier dynamics and bathymetry at Upernavik Isstrøm and Upernavik Isfjord, North-West Greenland. GEUS Bulletin 31 Andresen, C. S., Straneo, F., Ribergaard, M. H., Bjørk, A. A., Andersen, T.J., Kuijpers, A., Nørgaard-Pedersen, N., Kjær, K. H., Schjøth, F., Weckström, K. and Ahlstrøm, A. P. 2012: Rapid response of Helheim Glacier in Greenland to climate variability over the past century. Nature Geoscience 5 Bjørk, A. A., Kjær, K. H., Korsgaard, N. J., Khan, A., S., Kjeldsen, K. K., Andresen, C. S., Box, J. E., Larsen, N. K. and Funder, S. 2012. Historical aerial photographs uncover eighty years of ice-climate interaction in southeast

  2. The first glacier inventory for entire Greenland

    NASA Astrophysics Data System (ADS)

    Rastner, P.; Bolch, T.; Mölg, N.; Le Bris, R.; Paul, F.

    2012-04-01

    Detailed glacier data is becoming more and more important in the last decades to solve several research issues. One of the most prominent questions in this regard is the potential contribution of glaciers and icecaps (GIC) to global sea-level rise. Primarily, estimates are uncertain due to the globally still incomplete information about glacier location and size, as well as large uncertainties in future climate scenarios. Recent studies that calculate global sea-level rise from GIC have developed simplified approaches using information from glacier inventories or gridded data sets and a range of different global climate models and emission scenarios. However, for several strongly glacierized regions very rough assumptions about the ice distribution have to be made and an urgent demand for a globally complete glacier inventory is expressed. The GIC on Greenland are one of the regions with lacking information. Within the EU FP7 project ice2sea we mapped the GIC on Greenland using Landsat TM/ETM+ imagery acquired around the year 2000, along with an additional dataset in the North (DCW - Digital Chart of the World). A digital elevation model (DEM) with 90 m resolution (GIMP DEM) was used to derive drainage divides and henceforth topographic parameters for each entity. A major challenge in this regard is the application of a consistent strategy to separate the local GIC from the ice sheet. For this purpose we have defined different levels of connectivity (CL) of the local GIC with the ice sheet: CL0: Not connected. CL1: Connected but separable (either with drainage divides in the accumulation region or in touch only - and thus separable - in the ablation region). CL2: Connected but non-separable (the local GIC contribute to the flow of an ice sheet outlet in the ablation area). Up to now close to 12'000 GIC (only CL0 and CL1) with a total area of about 129'000 km2 have been mapped considering only entities larger than 0.1 km2. The area of the ice sheet itself is

  3. Distinct patterns of seasonal Greenland glacier velocity

    PubMed Central

    Moon, Twila; Joughin, Ian; Smith, Ben; van den Broeke, Michiel R; van de Berg, Willem Jan; Noël, Brice; Usher, Mika

    2014-01-01

    Predicting Greenland Ice Sheet mass loss due to ice dynamics requires a complete understanding of spatiotemporal velocity fluctuations and related control mechanisms. We present a 5 year record of seasonal velocity measurements for 55 marine-terminating glaciers distributed around the ice sheet margin, along with ice-front position and runoff data sets for each glacier. Among glaciers with substantial speed variations, we find three distinct seasonal velocity patterns. One pattern indicates relatively high glacier sensitivity to ice-front position. The other two patterns are more prevalent and appear to be meltwater controlled. These patterns reveal differences in which some subglacial systems likely transition seasonally from inefficient, distributed hydrologic networks to efficient, channelized drainage, while others do not. The difference may be determined by meltwater availability, which in some regions may be influenced by perennial firn aquifers. Our results highlight the need to understand subglacial meltwater availability on an ice sheet-wide scale to predict future dynamic changes. Key Points First multi-region seasonal velocity measurements show regional differences Seasonal velocity fluctuations on most glaciers appear meltwater controlled Seasonal development of efficient subglacial drainage geographically divided PMID:25821275

  4. Investigating the Response of Greenland Outlet Glaciers to Perturbations Using a 1D Flowline Model

    NASA Astrophysics Data System (ADS)

    Petrakopoulos, K.; Stearns, L. A.; van der Veen, C. J.

    2015-12-01

    Over the past two decades, the behavior of many Greenland tidewater outlet glaciers has been characterized by dramatic acceleration, thinning, and retreat. In some cases this behavior is followed by re-advance, thickening and deceleration. The mechanisms that control glacier stability are not fully understood, and hinder ice sheet mass balance projections. Many studies suggest that accelerations are caused exclusively by processes at the terminus, namely by mechanisms that result in increases in iceberg calving rates. In this study we investigate whether comparable accelerations can initiate at different places along the glacier trunk due to changes in subglacial processes or shear margin evolution. We begin our experiments using a prognostic depth integrated (1-D) flowline model applied to Helheim Glacier, and investigate its flow response to perturbations at the terminus and up-flow. Our work shows that large-scale accelerations could have initiated up-flow far from the terminus. The results of this study will contribute to the long-lasting debate about the role of terminus dynamics, and thus ocean conditions, in modulating ice sheet mass balance.

  5. Pathways of Petermann Glacier meltwater, Greenland

    NASA Astrophysics Data System (ADS)

    Heuzé, Céline; Wåhlin, Anna; Johnson, Helen; Münchow, Andreas

    2016-04-01

    Radar and satellite observations suggest that the floating ice shelf of Petermann Glacier loses up to 80% of its mass through basal melting, caused by the intrusion of warm Atlantic Water into the fjord and under the ice shelf. The fate of Petermann's glacial meltwater is still largely unknown. It is investigated here, using hydrographic observations collected during a research cruise on board I/B Oden in August 2015. Two methods are used to detect the meltwater from Petermann: a mathematical one that provides the concentration of ice shelf meltwater, and a geometrical one to distinguish the meltwater from Petermann and the meltwater from other ice shelves. The meltwater from Petermann mostly circulates on the north side of the fjord. At the sill, 0.5 mSv of meltwater leave the fjord, mostly on the northeastern side between 100 and 350 m depth, but also in the central channel, albeit with a lesser concentration. Meltwater from Petermann is found in all the casts in Hall Basin, notably north of the sill by Greenland coast. The geometrical method reveals that the casts closest to the Canadian side mostly contain meltwater from other, unidentified glaciers. As Atlantic Water warms up, it is key to monitor Greenland melting glaciers and track their meltwater to properly assess their impact on the ocean circulation and sea level rise.

  6. The Petermann Glacier Experiment, NW Greenland

    NASA Astrophysics Data System (ADS)

    Mix, A. C.; Jakobsson, M.; Andrews, J. T.; Jennings, A. E.; Mayer, L. A.; Marcott, S. A.; Muenchow, A.; Stoner, J. S.; Andresen, C. S.; Nicholls, K. W.; Anderson, S. T.; Brook, E.; Ceperley, E. G.; Cheseby, M.; Clark, J.; Dalerum, F.; Dyke, L. M.; Einarsson, D.; Eriksson, B.; Frojd, C.; Glueder, A.; Hedman, U.; Heirman, K.; Heuzé, C.; Hogan, K.; Holden, R.; Holm, C.; Jerram, K.; Krutzfeldt, J.; Nicolas, L.; Par, L.; Lomac-MacNair, K.; Madlener, S.; McKay, J. L.; Meijer, T.; Meiton, A.; Brian, M.; Mohammed, R.; Molin, M.; Moser, C.; Normark, E.; Padman, J.; Pecnerova, P.; Reilly, B.; Reusche, M.; Ross, A.; Stranne, C.; Trinhammer, P.; Walczak, M. H.; Walczak, P.; Washam, P.; Karasti, M.; Anker, P.

    2016-12-01

    The Petermann Glacier Experiment is a comprehensive study on land, ocean, and ice in Northwest Greenland, staged from Swedish Icebreaker Oden in 2015 as a collaboration between the US, Sweden, UK, and Denmark. This talk introduces the strategic goals of the experiment and connects the various scientific results. Petermann Glacier drains a significant marine-based sector of the northern Greenland Ice Sheet and terminates in a floating ice tongue, one of the largest remaining systems of its kind in the northern hemisphere. Records of the modern state of Petermann Glacier and its past variations are of interest to understand the sensitivity of marine terminating outlet glaciers to change, and to constrain the rates and extent of changes that have actually occurred. With this case study we are learning the rules of large scale dynamics that cannot be understood from modern observations alone. Although past behavior is not an simple analog for the future, and no single system captures all possible behaviors, insights from these case studies can be applied through models to better project how similar systems may change in the future. The Petermann Expedition developed the first comprehensive bathymetric maps of the region, drilled through the floating ice tongue to obtain sub-shelf sediment cores near the grounding line and to monitor sub-ice conditions, recovered a broad array of sediment cores documenting changing oceanic conditions in Petermann Fjord, Hall Basin, and Nares Strait, measured watercolumn properties to trace subsurface watermasses that bring heat from the Arctic Ocean into deep Petermann Fjord to melt the base of the floating ice tongue, developed a detailed record of relative sealevel change on land to constrain past ice loads, and recovered pristine boulders for cosmogenic exposure dating of areal ice retreat on land. Together, these studies are shedding new light on the dynamics of past glaciation in Northwest Greenland, and contributing to fundamental

  7. 21st-century evolution of Greenland outlet glacier velocities.

    PubMed

    Moon, T; Joughin, I; Smith, B; Howat, I

    2012-05-04

    Earlier observations on several of Greenland's outlet glaciers, starting near the turn of the 21st century, indicated rapid (annual-scale) and large (>100%) increases in glacier velocity. Combining data from several satellites, we produce a decade-long (2000 to 2010) record documenting the ongoing velocity evolution of nearly all (200+) of Greenland's major outlet glaciers, revealing complex spatial and temporal patterns. Changes on fast-flow marine-terminating glaciers contrast with steady velocities on ice-shelf-terminating glaciers and slow speeds on land-terminating glaciers. Regionally, glaciers in the northwest accelerated steadily, with more variability in the southeast and relatively steady flow elsewhere. Intraregional variability shows a complex response to regional and local forcing. Observed acceleration indicates that sea level rise from Greenland may fall well below proposed upper bounds.

  8. Instrument for Analysis of Greenland's Glacier Mills

    NASA Technical Reports Server (NTRS)

    Behar, Alberto E.; Matthews, Jaret B.; Tran, Hung B.; Steffen, Konrad; McGrath, Dan; Phillips, Thomas; Elliot, Andrew; OHern, Sean; Lutz, Colin; Martin, Sujita; Wang, Henry

    2010-01-01

    A new instrument is used to study the inner workings of Greenland s glacier mills by riding the currents inside a glacier s moulin. The West Greenland Moulin Explorer instrument was deployed into a tubular shaft to autonomously record temperature, pressure, 3D acceleration, and location. It is built with a slightly positive buoyancy in order to assist in recovery. The unit is made up of several components. A 3-axis MEMS (microelectromechanical systems) accelerometer with 0.001-g resolution forms the base of the unit. A pressure transducer is added that is capable of withstanding 500 psi (=3.4 MPa), and surviving down to -40 C. An Iridium modem sends out data every 10 minutes. The location is traced by a GPS (Global Positioning System) unit. This GPS unit is also used for recovery after the mission. Power is provided by a high-capacity lithium thionyl chloride D-sized battery. The accelerometer is housed inside a cylindrical, foot-long (=30 cm) polyvinyl chloride (PVC) shell sealed at each end with acrylic. The pressure transducer is attached to one of these lids and a MEMS accelerometer to the other, recording 100 samples per second per axis.

  9. Outlet glaciers of southeast Greenland: rapid, synchronised regional retreat at the start of the Holocene?

    NASA Astrophysics Data System (ADS)

    Dyke, L. M.; Hughes, A. L.; Murray, T.; Ródes

    2012-12-01

    We report new in-situ cosmogenic isotope (10Be) exposure dates from two major fjord systems in southeast (SE) Greenland. Low elevation erratic pairs from Kangerdlugssuaq Fjord reveal the onset of coastal deglaciation at ~11 ky BP. Overlapping exposure ages from a fjord axis transect show this was followed by a period of rapid deglaciation to a position at least 50 km from the mouth. The rapid deglaciation of Kangerdlugssuaq Fjord taken together with similar dates from Sermilik Fjord situated ~350 km southwards (Hughes et al., 2012), shows synchronous coastal deglaciation. This regional synchronicity implies a common regional driving mechanism. Ice sheet retreat from the continental shelf was underway by 15 ky BP, probably in response to long term climate amelioration following the Last Glacial Maximum (LGM). We suggest that the 'fjord phase' of deglaciation occurred rapidly due to significant climatic amelioration and changing oceanic conditions at the end of the Younger Dryas stadial. To test the synchronicity of regional deglaciation further, we will report exposure ages and retreat rates from Bernstorffs Isfjord, 650 km south of Kangerdlugssuaq and 300 km south of Sermilik Fjord. Bathymetric data and geomorphological evidence from Bernstorffs Isfjord hint at a still-stand or re-advance during the Holocene: exposure dates will be used to test this hypothesis. Widespread changes have been reported in the marine terminating glaciers of the southeast sector of the Greenland Ice Sheet (GrIS) during the early 2000s. Our results show retreat rates that are either significantly faster or persist for much longer than those observed recently, and demonstrate the great sensitivity of these marine-terminating glaciers to climatic change. References: Hughes, A.L.C., Rainsley, E., Murray T., Fogwill, C.J., Schnabel, C. and Xu, S. (2012) Rapid response of Helheim Glacier, southeast Greenland, to early Holocene climate warming. Geology, 40, 427-430.

  10. (abstract) A Mini-Surge on the Ryder Glacier, Greenland

    NASA Technical Reports Server (NTRS)

    Joughin, I.; Tulaczyk, Slawek; Fahnestock, M.; Kwok, R.

    1996-01-01

    We have detected a dramatic short-term speedup of the Ryder Glacier, Greenland, using satellite radar interferometry. The accelerated flow represents a substantial, though short-lived, change in the ice discharge from the basin. We use the term.

  11. Investigating connections between local-remote atmospheric variability and Greenland outlet glacier behavior

    NASA Astrophysics Data System (ADS)

    Sobolowski, Stefan; Chen, Linling; Miles, Victoria

    2016-04-01

    The outlet glaciers along the margins of the Greenland Ice Sheet (GrIS) exhibit a range of behaviors, which are crucial for understanding GrIS mass changes from a dynamical point of view. However, the drivers of this behavior are still poorly understood. Arguments (counter-arguments) have been made for a strong (weak) local oceanic influence on marine terminating outlet glaciers while decadal-scale drivers linked to fluctuations in the Ice sheet itself and the North Atlantic ocean (e.g. Atlantic Multidecadal Variability) have also been posited as drivers. Recently there have also been studies linking (e.g. seasonal to interannual) atmospheric variability, synoptic activity and the Ice Sheet variability. But these studies typically investigate atmospheric links to the large-scale behavior of the Ice Sheet itself and do not go down to the scale of the outlet glaciers. Conversely, investigations of the outlet glaciers often do not include potential links to non-local atmospheric dynamics. Here the authors attempt to bridge the gap and investigate the relationship between atmospheric variability across a range of scales and the behavior of three outlet glaciers on Greenland's southeast coast over a 33-year period (1980-2012). The glaciers - Helheim, Midgard and Fenris - are near Tasiilaq, are marine terminating and exhibit varying degree of connection to the GrIS. ERA-Interim reanalysis, sea-ice data and glacier observations are used for the investigation. Long records of mass balance are unavailable for these glaciers and front position is employed as a measure of glacier atmosphere interactions across multiple scales, as it exhibits robust relationships to atmospheric variability on time scales of seasons to many years, with the strongest relationships seen at seasonal - interannual time scales. The authors do not make the argument that front position is a suitable proxy for mass balance, only that it is indicative of the role of local and remote atmospheric

  12. Greenland ice sheet outlet glacier front changes: comparison of year 2008 with past years

    NASA Astrophysics Data System (ADS)

    Decker, D. E.; Box, J.; Benson, R.

    2008-12-01

    NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) imagery are used to calculate inter-annual, end of summer, glacier front area changes at 10 major Greenland ice sheet outlets over the 2000-2008 period. To put the recent 8 end of summer net annual changes into a longer perspective, glacier front position information from the past century are also incorporated. The largest MODIS-era area changes are losses/retreats; found at the relatively large Petermann Gletscher, Zachariae Isstrom, and Jakobshavn Isbrae. The 2007-2008 net ice area losses were 63.4 sq. km, 21.5 sq. km, and 10.9 sq. km, respectively. Of the 10 largest Greenland glaciers surveyed, the total net cumulative area change from end of summer 2000 to 2008 is -536.6 sq km, that is, an area loss equivalent with 6.1 times the area of Manhattan Is. (87.5 sq km) in New York, USA. Ice front advances are evident in 2008; also at relatively large and productive (in terms of ice discharge) glaciers of Helheim (5.7 sq km), Store Gletscher (4.9 sq km), and Kangerdlugssuaq (3.4 sq km). The largest retreat in the 2000-2008 period was 54.2 sq km at Jakobshavn Isbrae between 2002 and 2003; associated with a floating tongue disintegration following a retreat that began in 2001 and has been associated with thinning until floatation is reached; followed by irreversible collapse. The Zachariae Isstrom pro-glacial floating ice shelf loss in 2008 appears to be part of an average ~20 sq km per year disintegration trend; with the exception of the year 2006 (6.2 sq km) advance. If the Zachariae Isstrom retreat continues, we are concerned the largest ice sheet ice stream that empties into Zachariae Isstrom will accelerate, the ice stream front freed of damming back stress, increasing the ice sheet mass budget deficit in ways that are poorly understood and could be surprisingly large. By approximating the width of the surveyed glacier frontal zones, we determine and present effective glacier normalized length (L

  13. 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

    along the NW coast, and thinning expanding to higher elevations in SW and N Greenland. Several outlet glaciers, for example Humboldt and Petermann glaciers in NW Greenland and Kangilerngata Sermia in W Greenland exhibit a complex spatial and temporal pattern of thickening-thinning with regions of thickening observed at lower elevations. We will examine the thickening and thinning history and the record of surface velocity of these glaciers to investigate the processes responsible for initiating and sustaining these changes. Moreover, by analyzing the detailed surface elevation change history along flowlines or across drainage basins, the propagation of thinning following perturbations at the glacier terminus can be investigated. Results, depicting the evolution of surface elevation changes of three major outlet glaciers, Jakobshavn, Helheim and Kangerlussuaq glaciers, will be shown.

  14. Marine-terminating glaciers sustain high productivity in Greenland fjords.

    PubMed

    Meire, Lorenz; Mortensen, John; Meire, Patrick; Juul-Pedersen, Thomas; Sejr, Mikael K; Rysgaard, Søren; Nygaard, Rasmus; Huybrechts, Philippe; Meysman, Filip J R

    2017-08-04

    Accelerated mass loss from the Greenland ice sheet leads to glacier retreat and an increasing input of glacial meltwater to the fjords and coastal waters around Greenland. These high latitude ecosystems are highly productive and sustain important fisheries, yet it remains uncertain how they will respond to future changes in the Arctic cryosphere. Here we show that marine-terminating glaciers play a crucial role in sustaining high productivity of the fjord ecosystems. Hydrographic and biogeochemical data from two fjord systems adjacent to the Greenland ice sheet, suggest that marine ecosystem productivity is very differently regulated in fjords influenced by either land-terminating or marine-terminating glaciers. Rising subsurface meltwater plumes originating from marine-terminating glaciers entrain large volumes of ambient deep water to the surface. The resulting upwelling of nutrient-rich deep water sustains a high phytoplankton productivity throughout summer in the fjord with marine-terminating glaciers. In contrast, the fjord with only land-terminating glaciers lack this upwelling mechanism, and is characterized by lower productivity. Data on commercial halibut landings support that coastal regions influenced by large marine-terminating glaciers have substantially higher marine productivity. These results suggest that a switch from marine-terminating to land-terminating glaciers can substantially alter the productivity in the coastal zone around Greenland with potentially large ecological and socio-economic implications. © 2017 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

  15. Contrasting response of South Greenland glaciers to recent climatic change

    SciTech Connect

    Warren, C.R.; Glasser, N.F. )

    1992-05-01

    A unique geographical configuration of glaciers exists in the Narsarsuaq district of South Greenland. Two large outlet glaciers divide into seven distributaries, such that each glacier system has land-terminating, tidewater-calving, and fresh-water-calving termini. Despite a similar climatic regime, these seven glaciers have exhibited strongly contrasting terminal behavior in historical time, as shown by historical records, aerial photographs, and fieldwork in 1989. The behavior of the calving glaciers cannot be accounted for with reference solely to climatic parameters. The combination of iceberg calving dynamics and topographic control has partially decoupled them from climatic forcing such that their oscillations relate more closely to glaciodynamic than glacioclimatic factors.

  16. A calving law for ice sheet models; Investigating the role of surface melt on dynamics of Greenland outlet glaciers

    NASA Astrophysics Data System (ADS)

    Nick, F. M.; van der Veen, C. J.; Vieli, A.

    2008-12-01

    alving of icebergs accounts for perhaps as much as half the ice transferred from the Greenland Ice Sheet into the surrounding ocean, and virtually all of the ice loss from the Antarctic Ice Sheet. We have formulated a calving model that can be readily incorporated into time-evolving numerical ice-flow models. Our model is based on downward penetration of water-filled surface crevasses and upward propagation of basal crevasses. A calving event occurs when the depth of the surface crevasse (which increases as melting progresses through the summer) reaches the height of the basal crevasse. Our numerical ice sheet model is able to reproduce observed seasonal changes of Greenland outlet glaciers, such as fluctuations in flow speed and terminus positions. We have applied the model to Helheim Glacier on the east coast, and Petermann Glacier in the northwest. Our model suggests that rapid retreat of the claving front is highly affected by the amplified calving rate due to increasing water level in surface crevasses during warmer summers. Our results show little response to seasonally enhanced basal lubrication from surface melt. This modeling study provides insights into the role of surface and basal hydrology to ice sheet dynamics and on how to incorporate calving in ice sheet models and therefore advances our ability to predict future ice sheet change.

  17. No slowing down of Jakobshavn Isbræ in 2014: Results from feature-tracking five Greenland outlet glaciers using Landsat-8 data and the ImGRAFT toolbox

    NASA Astrophysics Data System (ADS)

    Messerli, Alexandra; Karlsson, Nanna B.; Grinsted, Aslak

    2015-04-01

    Data from the Landsat-8, panchromatic band, spanning the period (August) 2013 - (September) 2014 have been feature-tracked to construct ice velocities and flux estimates for five major Greenland outlet glaciers: Jakobshavn Isbræ, Nioghalvfjerdsbræ, Kangerdlugssuaq, Helheim and Petermann glaciers. The outlet glaciers are responsible for draining more than 20% of the Greenland Ice Sheet, and thus have a significant impact on its mass balance. The feature-tracking is performed with the newly developed ImGRAFT toolbox, a Matlab-based, freely available software (http://imgraft.glaciology.net). Overall, the resulting velocity fields and fluxes agree with the findings of existing studies. Notably, we find that Jakobshavn Isbræ has reached an unprecedented speed of over 50m/day, and exhibit large, seasonal fluctuations. In contrast, on the east coast of Greenland, Helheim and Kangerdlugssuaq Glaciers have returned to pre-speed up velocities, following a peak in ice flux about a decade ago. Petermann and Nigohalvfjerdsbræ show little variability in speeds with typical flow speeds of less than 5m/day.

  18. Bathymetric Controls On Observed Tidewater Glacier Retreat In Northwest Greenland

    NASA Astrophysics Data System (ADS)

    Porter, D. F.; Tinto, K. J.; Boghosian, A.; Cochran, J. R.; Bell, R. E.

    2013-12-01

    Although many of the largest glaciers in Greenland are losing mass, the large variability in observed mass wastage of the remaining glaciers clouds interpretation of the proposed external forcings, such as warming of the ocean or atmosphere. Some glaciers are accelerating and thinning while other nearby glaciers advance and gain mass. Recent efforts suggest that increased ocean temperatures may be responsible for the observed glacial retreat in Greenland and Antarctica through increased basal melting beneath floating ice tongues and vertical ice faces of tidewater glaciers. Basal melting may contribute significantly to calving and thinning, and to an eventual speeding up of the glacier, resulting in thinning further inland. Knowledge of fjord geometry is crucial for ice-ocean interaction because the availability of ocean heat to the ice will be restricted by narrow sills and shallow grounding lines. We investigate whether the variability in observed changes among Greenland glaciers can be partially explained by variation in fjord geometry. Some features of a fjord that could influence the ice-ocean system include the depth of the grounding line, the presence of sills, sloping bed, and the water cavity shape beneath floating ice. New estimates of fjord bathymetries in northwest Greenland, using airborne gravimetry measurements from NASA Operation IceBridge flights, are compared to estimates of ice acceleration and mass wastage of neighboring glaciers. We investigate the correlation between fjord geometry features and several glacier parameters, such as surface velocity and elevation changes. We determine that the geometry of glacial fjords play a large role in determining the stability of outlet glaciers. Deep sills and deep terminus grounding lines will allow greater interaction with the deep and warm Atlantic water off the shelf break. For two neighboring glaciers in northwest Greenland, we find that the glacier with a deeper grounding line, and presumably in

  19. Reconstruction of the past 2000 years of ocean and glacier variability in Sermilik Fjord, SE Greenland, based on sediment archives

    NASA Astrophysics Data System (ADS)

    Stoican, Andreea; Andresen, Camilla; Seidenkrantz, Marit-Solveig; Kjaer, Kurt; Kuijpers, Antoon; Massé, Guillaume; Weckström, Kaarina

    2013-04-01

    Glaciomarine sediments represent valuable archives of climate and glacier variability in the arctic environment. Especially the fjords along Greenland's east coast represent a dynamic and complicated system, influenced by regional ocean circulation, local currents and by glacier terminations. Therefore, they represent appropriate locations for sedimentary core studies in order to detect the relative glacier and ocean variability. The aim of this project is to reconstruct the past 2000 years of glacier and ocean variability in Sermilik fjord, SE Greenland, into which Helheim glacier terminates. This is done by analysing two sedimentary cores (ER11 and ER07) and hereby reconstruct fluctuations in marine-terminating outlet glacier dynamics (including iceberg and to a lesser extent melt water production) and the interaction with oceanographic changes. The oceanographic variability is reconstructed on the basis of benthic and planktonic foraminiferal analysis and the content of the biomarker IP25 and these proxies are interpreted to reflect changes in the inflow of the warm Irminger Current and polar waters in association with the East Greenland Current. Interestingly, studies show that the onset of the Little Ice Age was characterised by intensified inflow of Irminger Current water masses to the Southeastern and Southwestern shelves of Greenland and that these may be associated with a contracted subpolar gyre. At the same time, the EGC Polar Water transport also intensified leading to a stratified water column on the shelf and this may have favoured entrainment of warm subsurface IC waters. Alternatively, the relatively warm rim of the eastern subpolar gyre may have promoted intense submarine melting of extended outlet glaciers at this time, producing enhanced melt water outflow which favoured estuarine circulation processes maintaining the inflow of IC water masses. Thus the aim of this study is to investigate in detail the circulation of these LIA warm waters from

  20. Using ISSM to simulate the LIA to present ice margin change at Upernavik Glacier, Greenland

    NASA Astrophysics Data System (ADS)

    Haubner, Konstanze; Larsen, Signe H.; Box, Jason E.; Andersen, Morten L.; Andresen, Camilla S.; Kjær, Kurt H.; Weidick, Anker

    2015-04-01

    The possibility for rapid melting of the Greenland ice sheet ranks among the most serious societal climate threats. To improve predictions it is useful to know more about past ice volume changes. This project puts the rate of contemporary climate change-driven Greenland ice mass change in a temporal context, by simulating the Greenland ice sheet margin throughout the Holocene. The modelled results can be compared with historical ice positions and with records of past glacier activity (i.e. calving) based on studies of sediment cores from the fjord (Andresen et al. 2012). Another data source of ice margins derives from aerial photography and ice trimline positions (Kjær et al. 2012). Here we present a simulation using the Ice Sheet System Model (ISSM) (Larour et. al 2012) of the Upernavik Isstrøm, a set of NW Greenland marine-terminating glaciers. The simulation runs from year 1840 in the Little Ice Age (LIA) to year 2012, forced by an updated surface mass balance reconstruction after Box (2013). The work establishes a base from which we can model the entire Greenland Ice Sheet. To resolve where model development is needed most, using observations that are iteratively excluded from the simulation, we evaluate the relative importance of each data set on the total uncertainty. We discuss the challenges associated with the general model boundary conditions such as the ice-ocean interaction representation in the model and lacking bathymetrical data. Finally, we address the need for further observations and the perspective of applying the model to other glaciers. works cited: • Andresen, C. S., Straneo, F., Ribergaard, M. H., Bjørk, A. A., Andersen, T.J., Kuijpers, A., Nørgaard-Pedersen, N., Kjær, K. H., Schjøth, F., Weckström, K. and Ahlstrøm, A. P. 2012: Rapid response of Helheim Glacier in Greenland to climate variability over the past century. Nature Geoscience 5, 37-41, doi:10.1038/ngeo1349. • Box, J. E. 2013. Greenland ice sheet mass balance

  1. Oceanic forcing and terminus retreat at east Greenland's tidewater glaciers

    NASA Astrophysics Data System (ADS)

    Cowton, Tom; Sole, Andrew; Nienow, Peter; Slater, Donald; Wilton, David; Hanna, Edward

    2017-04-01

    The role of oceanic forcing in the retreat of Greenland's tidewater outlet glaciers remains equivocal, in part due to the difficulty of quantifying how this forcing varies over time and between glaciers. Using plume modelling, we demonstrate that the strength of buoyancy-driven circulation in fjords is highly sensitive to the glacier grounding line depth and runoff discharge, allowing a simple parameterisation for oceanic forcing based on up-fjord oceanic heat transport. In conjunction with time series of glacier runoff and shelf water temperature, we use this parameterisation to elucidate controls on the terminus position of 10 outlet glaciers in east Greenland over a 20-year period. We find that up to 70 % of terminus position variability is explained by modelled oceanic forcing, while comparably strong correlations are also obtained between glacier length and runoff and shelf water temperature. Our findings indicate that despite the complexity of tidewater glacier behaviour and current limitations in understanding of calving front processes, over multi-year time scales a significant proportion of terminus position change can be explained as a simple function of key environmental variables.

  2. Ocean-Glacier Interactions in Alaska and Comparison to Greenland

    NASA Astrophysics Data System (ADS)

    Motyka, R. J.; Truffer, M.

    2011-12-01

    Meltwater from Alaska's coastal glaciers and icefields accounts for nearly half of the total freshwater discharged into the Gulf of Alaska (GOA), with 10% coming from glacier volume loss associated with rapid thinning and retreat of glaciers (Neal et al, 2010). This glacier freshwater discharge contributes to maintaining the Alaska Coastal Current (ACC), which eventually reaches the Arctic Ocean (Royer and Grosch, 2006), thereby linking changes of glaciers along the coast of Alaska to the whole Arctic system. Water column temperatures on the shelf of northern GOA, monitored at buoy GAK1 near Seward, have increased by about 1 deg C since 1970 throughout the 250 m depth and vertical density stratification has also increased. Roughly half of the glacier contribution to ACC is derived from the ~ 50 tidewater glaciers (TWG) that drain from Alaska's coastal mountains into the Gulf of Alaska (GOA). Fjord systems link these TWGs to the GOA, with fjord circulation patterns driven in part by buoyancy-driven convection of subglacial freshwater discharge at the head of the fjord. Neoglacial shallow sills (< 50 m deep) modulate the influx of warm ocean waters (up to 10 deg C) into these fjords. Convection of these warm waters melts icebergs and submerged faces of TWGs. The study of interactions between glaciers, fjords, and the ocean in coastal Alaska has had a long but very sporadic history. We examine this record starting with the "TWG cycle" hypothesis. We next examine recent hydrographic data from several different TWG fjords, representative of advancing and retreating TWGs (Columbia, Yahtse, Hubbard, and LeConte Glaciers), evaluate similarities and differences, and estimate the relative contributions of submarine glacier melting and subglacial discharge to fjord circulation. Circulation of warm ocean waters in fjords has also been hypothesized to play an important role in destabilizing and modulating glacier discharge from outlet glaciers in Greenland. We therefore compare

  3. Greenland outlet glacier dynamics from Extreme Ice Survey (EIS) photogrammetry

    NASA Astrophysics Data System (ADS)

    Hawbecker, P.; Box, J. E.; Balog, J. D.; Ahn, Y.; Benson, R. J.

    2010-12-01

    Time Lapse cameras fill gaps in our observational capabilities: 1. By providing much higher temporal resolution than offered by conventional airborne or satellite remote sensing. 2. While GPS or auto-theodolite observations can provide higher time resolution data than from photogrammetry, survival of these instruments on the hazardous glacier surface is limited, plus, the maintenance of such systems can be more expensive than the maintenance of a terrestrial photogrammetry installation. 3. Imagery provide a high spatial density of observations across the glacier surface, higher than is realistically available from GPS or other in-situ observations. 4. time lapse cameras provide observational capabilities in Eulerian and Lagrangian frames while GPS or theodolite targets, going along for a ride on the glacier, provide only Lagrangian data. Photogrammetry techniques are applied to a year-plus of images from multiple west Greenland glaciers to determine the glacier front horizontal velocity variations at hourly to seasonal time scales. The presentation includes comparisons between glacier front velocities and: 1. surface melt rates inferred from surface air temperature and solar radiation observations; 2. major calving events identified from camera images; 3. surface and near-surface ocean temperature; 4. land-fast sea ice breakup; 5. tidal variations; 6. supra-glacial melt lake drainage events observed in daily optical satellite imagery; and 7.) GPS data. Extreme Ice Survey (EIS) time lapse camera overlooking the Petermann glacier, installed to image glacier dynamics and to capture the predicted ice "island" detachment.

  4. Large fluctuations in speed on Greenland's Jakobshavn Isbrae glacier.

    PubMed

    Joughin, Ian; Abdalati, Waleed; Fahnestock, Mark

    2004-12-02

    It is important to understand recent changes in the velocity of Greenland glaciers because the mass balance of the Greenland Ice Sheet is partly determined by the flow rates of these outlets. Jakobshavn Isbrae is Greenland's largest outlet glacier, draining about 6.5 per cent of the ice-sheet area, and it has been surveyed repeatedly since 1991 (ref. 2). Here we use remote sensing data to measure the velocity of Jakobshavn Isbrae between 1992 and 2003. We detect large variability of the velocity over time, including a slowing down from 6,700 m yr(-1) in 1985 to 5,700 m yr(-1) in 1992, and a subsequent speeding up to 9,400 m yr(-1) by 2000 and 12,600 m yr(-1) in 2003. These changes are consistent with earlier evidence for thickening of the glacier in the early 1990s and rapid thinning thereafter. Our observations indicate that fast-flowing glaciers can significantly alter ice discharge at sub-decadal timescales, with at least a potential to respond rapidly to a changing climate.

  5. Undercutting of marine-terminating glaciers in West Greenland

    NASA Astrophysics Data System (ADS)

    Rignot, Eric; Fenty, Ian; Xu, Yun; Cai, Cilan; Kemp, Chris

    2015-07-01

    Marine-terminating glaciers control most of Greenland's ice discharge into the ocean, but little is known about the geometry of their frontal regions. Here we use side-looking, multibeam echo sounding observations to reveal that their frontal ice cliffs are grounded deeper below sea level than previously measured and their ice faces are neither vertical nor smooth but often undercut by the ocean and rough. Deep glacier grounding enables contact with subsurface, warm, salty Atlantic waters (AW) which melts ice at rates of meters per day. We detect cavities undercutting the base of the calving faces at the sites of subglacial water (SGW) discharge predicted by a hydrological model. The observed pattern of undercutting is consistent with numerical simulations of ice melt in which buoyant plumes of SGW transport warm AW to the ice faces. Glacier undercutting likely enhances iceberg calving, impacting ice front stability and, in turn, the glacier mass balance.

  6. Leakage of the Greenland Ice Sheet through accelerated ice flow

    NASA Astrophysics Data System (ADS)

    Rignot, E.

    2005-12-01

    A map of coastal velocities of the Greenland ice sheet was produced from Radarsat-1 acquired during the background mission of 2000 and combined with radio echo sounding data to estimate the ice discharge from the ice sheet. On individual glaciers, ice discharge was compared with snow input from the interior and melt above the flux gate to determine the glacier mass balance. Time series of velocities on several glaciers at different latitudes reveal seasonal fluctuations of only 7-8 percent so that winter velocities are only 2 percent less than the yearly mean. The results show the northern Greenland glaciers to be close to balance yet losing mass. No change in ice flow is detected on Petermann, 79north and Zachariae Isstrom in 2000-2004. East Greenland glaciers are in balance and flowing steadily north of Kangerdlussuaq, but Kangerdlussuaq, Helheim and all the southeastern glaciers are thinning dramatically. All these glaciers accelerated, Kangerdlussuaq in 2000, Helheim prior to 2004, and southeast Greenland glaciers accelerated 10 to 50 percent in 2000-2004. Glacier acceleration is generally brutal, probably once the glacier reached a threshold, and sustained. In the northwest, most glaciers are largely out of balance. Jakobshavn accelerated significantly in 2002, and glaciers in its immediate vicinity accelerated more than 50 percent in 2000-2004. Less is known about southwest Greenland glaciers due to a lack of ice thickness data but the glaciers have accelerated there as well and are likely to be strongly out of balance despite thickening of the interior. Overall, I estimate the mass balance of the Greenland ice sheet to be about -80 +/-10 cubic km of ice per year in 2000 and -110 +/-15 cubic km of ice per year in 2004, i.e. more negative than based on partial altimetry surveys of the outlet glaciers. As climate continues to warm, more glaciers will accelerate, and the mass balance will become increasingly negative, regardless of the evolution of the ice sheet

  7. Fjord circulation promotes significant glacier-wide submarine melting at a west Greenland tidewater glacier

    NASA Astrophysics Data System (ADS)

    Slater, Donald A.; Straneo, Fiamma; Das, Sarah B.; Nienow, Peter W.

    2017-04-01

    In recent decades, rapid change at Greenland's marine-terminating glaciers has significantly impacted the contribution of the ice sheet to sea level. While these changes have been widely linked to a warming of the ocean around Greenland, process understanding linking ocean forcing to glacier response, for example by submarine melting, remains at an early stage. The most rapid submarine melting likely occurs where buoyant plumes, initiated by subglacial discharge, rise up tidewater glacier calving fronts. Plumes have therefore received much attention, yet a plume typically occupies only a small fraction of the submerged calving front area. Thus melting within the plume itself may be a small contributor to the front-wide melting experienced by the glacier. A plume may however promote melting over a much larger area by inducing a fjord-scale circulation which, by increasing water velocities at the ice/ocean interface, can give rise to increased melting over the entire glacier face. Here we address this fjord-scale, plume-driven circulation and its impact on submarine melting by combining observations collected within 100 m of marine-terminating Saqqarliup Sermia in west Greenland with high-resolution fjord modelling using the MITgcm. Both field data and modelling show that water from the main plume flows away from the glacier as a subsurface jet, and that entrainment into this jet generates regions of fjord water recirculating back towards the glacier. The modelling further suggests that these recirculations drive elevated across-glacier water motion thereby promoting significant submarine melting over the full 4 km-width of the calving front, resulting in total melt volumes which substantially exceed those generated directly by the relatively narrow plume. Our results highlight the value of combining detailed field observations with modelling and demonstrate how the secondary fjord circulation generated by plumes may play a significant role in driving submarine

  8. Rapid changes in ice discharge from Greenland outlet glaciers.

    PubMed

    Howat, Ian M; Joughin, Ian; Scambos, Ted A

    2007-03-16

    Using satellite-derived surface elevation and velocity data, we found major short-term variations in recent ice discharge and mass loss at two of Greenland's largest outlet glaciers. Their combined rate of mass loss doubled in less than a year in 2004 and then decreased in 2006 to near the previous rates, likely as a result of fast re-equilibration of calving-front geometry after retreat. Total mass loss is a fraction of concurrent gravity-derived estimates, pointing to an alternative source of loss and the need for high-resolution observations of outlet dynamics and glacier geometry for sea-level rise predictions.

  9. North Atlantic warming and the retreat of Greenland's outlet glaciers.

    PubMed

    Straneo, Fiammetta; Heimbach, Patrick

    2013-12-05

    Mass loss from the Greenland ice sheet quadrupled over the past two decades, contributing a quarter of the observed global sea-level rise. Increased submarine melting is thought to have triggered the retreat of Greenland's outlet glaciers, which is partly responsible for the ice loss. However, the chain of events and physical processes remain elusive. Recent evidence suggests that an anomalous inflow of subtropical waters driven by atmospheric changes, multidecadal natural ocean variability and a long-term increase in the North Atlantic's upper ocean heat content since the 1950s all contributed to a warming of the subpolar North Atlantic. This led, in conjunction with increased runoff, to enhanced submarine glacier melting. Future climate projections raise the potential for continued increases in warming and ice-mass loss, with implications for sea level and climate.

  10. Modeling ice front Dynamics of Greenland outlet glaciers using ISSM

    NASA Astrophysics Data System (ADS)

    Morlighem, M.; Bondzio, J. H.; Seroussi, H. L.; Rignot, E. J.

    2015-12-01

    The recent increase in the rate of mass loss from the Greenland Ice Sheet is primarily due to the acceleration and thinning of outlet glaciers along the coast. This acceleration is a dynamic response to the retreat of calving fronts, which leads to a loss in resistive stresses. These processes need to be included in ice sheet models in order to be able to accurately reproduce current trends in mass loss, and in the long term reduce the uncertainty in the contribution of ice sheets to sea level rise. Today, the vast majority of ice sheet models that include moving boundaries are one dimensional flow line and vertical flow band models, that are not adapted to the complex geometries of Greenland outlet glaciers, as they do not accurately capture changes in lateral stresses. Here, we use the level set method to track moving boundaries within a 2D plane view model of the Ice Sheet System Model (ISSM), and investigate the sensitivity of Store Glacier, in western Greenland, to the amount of melting occurring at its calving front. We explore different calving laws and obtain the best results with a new simple calving law adapted from von Mises yield criterion. We show that the ocean circulation near the front and the amount of runoff are able to trigger ice front advance and retreat depending on the amount of melting that they produce at the calving face, but the bed topography controls the stable positions of the ice front. The modeled calving front of Store Glacier, for which we have quality bed topography and sea floor bathymetry data, is particularly stable because of the presence of a large sill at the glacier terminus. If the ice front detaches from this stabilizing sill due to larger amounts of melting at the front or due to large calving events, the glacier front starts to retreat as the bed deepens inland, until it finds another stabilizing feature in the bed topography. The new bed topography maps based on mass conservation make it possible to model more

  11. Surface mass balance of Greenland mountain glaciers and ice caps

    NASA Astrophysics Data System (ADS)

    Benson, R. J.; Box, J. E.; Bromwich, D. H.; Wahr, J. M.

    2009-12-01

    Mountain glaciers and ice caps contribute roughly half of eustatic sea-level rise. Greenland has thousands of small mountain glaciers and several ice caps > 1000 sq. km that have not been included in previous mass balance calculations. To include small glaciers and ice caps in our study, we use Polar WRF, a next-generation regional climate data assimilation model is run at grid resolution less than 10 km. WRF provides surface mass balance data at sufficiently high resolution to resolve not only the narrow ice sheet ablation zone, but provides information useful in downscaling melt and accumulation rates on mountain glaciers and ice caps. In this study, we refine Polar WRF to simulate a realistic surface energy budget. Surface melting is calculated in-line from surface energy budget closure. Blowing snow sublimation is computed in-line. Melt water re-freeze is calculated using a revised scheme. Our results are compared with NASA's Gravity Recovery and Climate Experiment (GRACE) and associated error is calculated on a regional and local scale with validation from automated weather stations (AWS), snow pits and ice core data from various regions along the Greenland ice sheet.

  12. Investigating Long-term Behavior of Outlet Glaciers in Greenland

    NASA Technical Reports Server (NTRS)

    Csatho, Beata; vanderVeen, Kees; Schenk, Toni

    2005-01-01

    Repeat surveys by airborne laser altimetry in the 1990s have revealed significant thinning of outlet glaciers draining the interior of the Greenland Ice Sheet, with thinning rates up to several meters per year. To fully appreciate the significance of these recent glacier changes, the magnitude of retreat and surface lowering must be placed within the broader context of the retreat since the Last Glacial Maximum and, more significantly, of the retreat following the temporary glacier advance during the Little Ice Age (LIA). The LIA maximum stand is marked by trimlines, sharp boundaries between recently deglacifated unvegetated rocks, and vegetated surfaces at higher elevations. The objective of this project was to demonstrate the use of remote sensing data to map these trimlines and other glacial geomorphologic features.

  13. Glaciers and ice caps outside Greenland

    USGS Publications Warehouse

    Sharp, Marin; Wolken, G.; Burgess, D.; Cogley, J.G.; Copland, L.; Thomson, L.; Arendt, A.; Wouters, B.; Kohler, J.; Andreassen, L.M.; O'Neel, Shad; Pelto, M.

    2015-01-01

    Mountain glaciers and ice caps cover an area of over 400 000 km2 in the Arctic, and are a major influence on global sea level (Gardner et al. 2011, 2013; Jacob et al. 2012). They gain mass by snow accumulation and lose mass by meltwater runoff. Where they terminate in water (ocean or lake), they also lose mass by iceberg calving. The climatic mass balance (Bclim, the difference between annual snow accumulation and annual meltwater runoff) is a widely used index of how glaciers respond to climate variability and change. The total mass balance (ΔM) is defined as the difference between annual snow accumulation and annual mass losses (by iceberg calving plus runoff).

  14. Warm water pathways toward Nioghalvfjerdsfjorden Glacier, Northeast Greenland

    NASA Astrophysics Data System (ADS)

    Schaffer, Janin; von Appen, Wilken-Jon; Dodd, Paul A.; Hofstede, Coen; Mayer, Christoph; de Steur, Laura; Kanzow, Torsten

    2017-05-01

    Nioghalvfjerdsfjorden Glacier (79NG) is the largest of three marine-terminating outlet glaciers draining the Northeast Greenland Ice Stream. To understand how Atlantic waters supply waters in the cavity beneath the floating 79NG, we analyze historic and recent bathymetric, hydrographic, and velocity observations obtained on the Northeast Greenland continental shelf. The bathymetry is characterized by a trough system, consisting of the Westwind Trough and the Norske Trough in the northern and southern part of the continental shelf, respectively. Atlantic waters recirculating in Fram Strait cross the shelf break and enter the trough system at its southeastern inlet toward the inner shelf. Warm Atlantic Intermediate Water (AIW) present below 200 m in the Norske Trough shows large contributions of the recirculating Atlantic water. We found that the bathymetry is sufficiently deep to provide a direct subsurface pathway for warm AIW between the shelf break and the 79NG cavity via the Norske Trough. Likewise, based on the hydrographic data, we show that the Norske Trough supplies AIW warmer than 1°C to the 79NG, which is not present in the Westwind Trough. Our moored and lowered velocity measurements indicate that a boundary current carries warm AIW along the northeastern slope of Norske Trough toward the 79NG. We suggest that anomalies in Atlantic water temperatures in Fram Strait could reach 79NG within less than 1.5 years, thereby modifying the glacier's basal melt rates.

  15. Seasonal acceleration of Russell Glacier, Western Greenland during 2009 & 2010

    NASA Astrophysics Data System (ADS)

    Fitzpatrick, A.; Quincey, D.; Joughin, I.; Luckman, A.; Van As, D.; Hubbard, A.

    2012-04-01

    Seasonal changes in surface velocity of the Russell Glacier catchment, Western Greenland, have been derived using a combination of interferometry and satellite image feature tracking and are compared with the output of a well calibrated distributed energy balance model. Analysis is conducted between the extent and longevity of melt-driven flow acceleration between two contrasting years, the relatively short melt season of 2009 and the record high melt season of 2010. In both 2009 and 2010 the largest horizontal surface acceleration occurred at the ice margin soon after initiation of melt with the effect propagating up-glacier with reduced magnitude as the melt-season evolved. In both years ice flow near the margin of the Ice Sheet (within 14 km) had returned to winter values within ~80 days of the first recorded melt. However, within each 100m elevation band, melt-induced flow acceleration and magnitude of observed speedup in 2010 exceeded that of 2009. Up glacier (to 35 km), ice speed in 2010 continued above the background winter mean 126 days after the initiation of melt, in contrast to only 102 days in 2009. Structural changes in surface velocity patterns are also evident during the winter months, with measured velocities in February 2010 (22-57km) 26% greater at the end of winter compared to values from November 2010. This study highlights the large heterogeneity in spatial and temporal velocity structure occurring at the land terminating margin of the Greenland Ice Sheet and lends support for the idea that the evolution of the subglacial drainage system acts to regulate basal flow near the ice margin, thereby limiting the feedback between meltwater and ice flux. Further up glacier (>35km) the effect of this behavior is reduced even though large fluxes of surface meltwater were still generated in 2010, which suggests that in the upper zone of the catchment (where ice thickness exceeds 1000m) there is limited evolution of the subglacial meltwater system.

  16. Accelerating Ice Loss from the Fastest Greenland and Antarctic Glaciers

    NASA Technical Reports Server (NTRS)

    Thomas, R.; Frederick, E.; Li, J.; Krabill, W.; Manizade, S.; Paden, J.; Sonntag, J.; Swift, R.; Yungel, J.

    2011-01-01

    Ice discharge from the fastest glaciers draining the Greenland and Antarctic ice sheets . Jakobshavn Isbrae (JI) and Pine Island Glacier (PIG). continues to increase, and is now more than double that needed to balance snowfall in their catchment basins. Velocity increase probably resulted from decreased buttressing from thinning (and, for JI, breakup) of their floating ice tongues, and from reduced basal drag as grounding lines on both glaciers retreat. JI flows directly into the ocean as it becomes afloat, and here creep rates are proportional to the cube of bed depth. Rapid thinning of the PIG ice shelf increases the likelihood of its breakup, and subsequent rapid increase in discharge velocity. Results from a simple model indicate that JI velocities should almost double to >20 km/a by 2015, with velocities on PIG increasing to >10 km/a after breakup of its ice shelf. These high velocities would probably be sustained over many decades as the glaciers retreat within their long, very deep troughs. Resulting sea ]level rise would average about 1.5 mm/a.

  17. Accelerating Ice Loss from the Fastest Greenland and Antarctic Glaciers

    NASA Technical Reports Server (NTRS)

    Thomas, R.; Frederick, E.; Li, J.; Krabill, W.; Manizade, S.; Paden, J.; Sonntag, J.; Swift, R.; Yungel, J.

    2011-01-01

    Ice discharge from the fastest glaciers draining the Greenland and Antarctic ice sheets . Jakobshavn Isbrae (JI) and Pine Island Glacier (PIG). continues to increase, and is now more than double that needed to balance snowfall in their catchment basins. Velocity increase probably resulted from decreased buttressing from thinning (and, for JI, breakup) of their floating ice tongues, and from reduced basal drag as grounding lines on both glaciers retreat. JI flows directly into the ocean as it becomes afloat, and here creep rates are proportional to the cube of bed depth. Rapid thinning of the PIG ice shelf increases the likelihood of its breakup, and subsequent rapid increase in discharge velocity. Results from a simple model indicate that JI velocities should almost double to >20 km/a by 2015, with velocities on PIG increasing to >10 km/a after breakup of its ice shelf. These high velocities would probably be sustained over many decades as the glaciers retreat within their long, very deep troughs. Resulting sea ]level rise would average about 1.5 mm/a.

  18. The parallel flow assumption in Greenland outlet glaciers

    NASA Astrophysics Data System (ADS)

    Gourmelen, N.; Shepherd, A.; Park, J. W.

    2012-04-01

    Climate warming over the 20th century has forced dramatic changes in the Greenland Ice Sheet (GrIS). These changes have led to a reduction in the mass of the GrIS and a consequent rise in global sea level. Satellite observations have revealed an increased flow of the glaciers to the sea [Rignot et al., 2008], increased surface melting [Steffen et al., 2004], lowering of the Ice Sheet surface [Zwally and Giovinetto, 2001], retreat of the glaciers' fronts [Box et al., 2006], and gravity anomaly related to ice mass loss [Velicogna and Wahr, 2006]. When measuring the flow of ice from spaceborne sensors, it is often assumed that the direction and dip of flow follow the direction and dip of the ice surface [Rignot et al., 2011]; this is known as the surface parallel flow assumption [Joughin et al., 1996]. This assumption is often the only way to constrain glaciers' flow, as observation by spaceborne sensors in Polar Regions is limited. Departure from the parallel flow assumption means that the magnitude of ice flow and its changes will be misestimated. Departure from the ice parallel flow assumption also provides clues on the mechanisms leading to the flow pattern and to the change in flow magnitude. Here we exploit 20 years of Synthetic Aperture Radar spaceborn missions to constrain the three-dimensional flow of marine terminating glaciers in the GrIS. We use datasets from past and present ERS1, ERS2, ENVISAT, ALOS and TerraSAR-X missions to construct 3-dimensional flow maps of selected outlet glaciers of the GrIS. This dataset is used to explore the relationship between flow patterns, its temporal evolution, and processes at play at the margins of the GrIS.

  19. In-situ glacier monitoring in Zackenberg (NE Greenland): Freya Glacier and A.P. Olsen Ice Cap

    NASA Astrophysics Data System (ADS)

    Hynek, Bernhard; Hillerup Larsen, Signe; Binder, Daniel; Weyss, Gernot; Citterio, Michele; Schöner, Wolfgang; Ahlstrøm, Andreas Peter

    2015-04-01

    Due to the scarceness of glacier mass balance measurements from glaciers and local ice caps in East Greenland and the strong impact that local glaciers and ice caps outside the Ice Sheet are expected to exert on sea level rise in the present century, in 2007 and 2008 two glaciological monitoring programmes of peripheral Greenlandic glaciers started to operate near the Zackenberg Research Station in NE Greenland (74° N, 21° W). Freya (Fröya) Glacier is a 6 km long valley glacier situated on Clavering Island 10 km southeast of the Zackenberg research station with a surface area of 5.3 km2 (2013), reaching from 1305 m to 273 m a.s.l. The glacier is mainly oriented to NW and surrounded by high mountain ridges on both sides. A.P. Olsen Ice Cap is a 295 km2 peripheral ice cap located 35 km northeast of Zackenberg. The mass balance monitoring network is situated on the SE outlet glacier reaching from 1425 m to 525 m which drains into the hydrological basin of Zackenberg. This outlet glacier dams a lake which caused several glacial outburst floods within the period of investigation. The two studied glaciers are very close to each other (35 km), but they are complementary in many ways. Apart from the difference in size, which requires different monitoring strategies, Freya Glacier is nearer to the coast and therefore exposed to a more maritime climate with higher winter accumulation. The different area-altitude distribution of both glaciers is one of the main reason for the significantly more positive mean specific mass balance of A.P. Olsen Ice Cap compared to Freya Glacier. In this talk we present the glaciological monitoring on both glaciers and the main results of the first seven years of data.

  20. Fusion of multi-sensor surface elevation data for a better characterization of rapidly changing outlet glaciers in Greenland

    NASA Astrophysics Data System (ADS)

    Schenk, A. F.; Csatho, B. M.; McCormick, D. P.; Van der Veen, C. J.

    2013-12-01

    During the last two decades surface elevation data have been gathered over the Greenland Ice Sheet (GrIS) from a variety of different sensors such as spaceborne and airborne laser altimetry (ICESat, ATM and LVIS) as well as from stereo imaging systems, most notably from ASTER and Worldview. The spatio-temporal resolution, the accuracy, and the spatial coverage of all these data differ widely. For example, laser altimetry systems are much more accurate than DEMs derived by correlation from imaging systems. On the other hand, DEMs usually have a superior spatial resolution and extended spatial coverage. We have developed the SERAC (Surface Elevation Reconstruction And Change detection) system to cope with the data complexity and the computation of elevation change histories. SERAC simultaneously determines the ice sheet surface shape and the time-series of elevation changes for surface patches whose size depends on the ruggedness of the surface and the point distribution of the sensors involved. By incorporating different sensors, SERAC is a true fusion system that generates the best plausible result (time-series of elevation changes)-a result that is better than the sum of its individual parts. We present detail examples of Kangerlussuaq and Helheim glaciers, involving ICESat, ATM and LVIS laser altimetry data, together with ASTER DEMs. ASTER DEMs are readily available but notorious for their accuracy behavior. The nominally stated accuracy of ~15 m may occasionally reach much higher values. By embedding ASTER DEMs into the SERAC time-series of elevation changes, we are able to determine plausible corrections. Thus, we can use ASTER DEMs to temporally and spatially densify the elevation change record. This is especially important on rapidly changing outlet glaciers where laser altimetry data might only be available sporadically To investigate the mechanisms controlling their behavior, we reconstructed elevation change histories along the central flowlines of these

  1. Mountain glaciers vs Ice sheet in Greenland - learning from a new monitoring site in West Greenland

    NASA Astrophysics Data System (ADS)

    Abermann, Jakob; van As, Dirk; Wacker, Stefan; Langley, Kirsty

    2017-04-01

    Only 5 out of the 20.000 peripheral glaciers and ice caps surrounding Greenland are currently monitored due to logistical challenges and despite their significance for sea level rise. Large spatial coast-to-icesheet mass and energy balance gradients limit simple upscaling methods from ice-sheet observations, which builds the motivation for this study. We present results from a new mass and energy balance time series at Qasigiannguit glacier (64°09'N; 51°21'W) in Southwest Greenland. Inter-annual variability is discussed and the surface energy balance over two summers is quantified and a ranking of the main drivers performed. We find that short-wave net radiation is by far the most dominant energy source during summer, followed by similar amounts of net longwave radiation and sensible heat, respectively. We then relate these observations to synchronous measurements at similar latitude on an outlet glacier of the ice sheet a mere 100 km away. We find very pronounced horizontal surface mass balance gradients, with generally more positive values closer to the coast. We conclude that despite minor differences of atmospheric parameters (i.e. humidity, radiation, and temperature) the main reason for the strongly different signal is a pronounced winter precipitation gradient that translates in a different duration of ice exposure and through that an albedo gradient. Modelled energy balance gradients converted into mass changes show good agreement to measured surface mass balance gradients and we explore a latitudinal signal of these findings.

  2. Holocene Mountain Glacier Variability in the Sukkertoppen Region, Western Greenland

    NASA Astrophysics Data System (ADS)

    Schweinsberg, A. D.; Briner, J. P.; Miller, G. H.; Lesnek, A. J.; Lifton, N. A.; Clements, S.

    2016-12-01

    Mountain glaciers and localized ice caps respond rapidly to small changes in climatic conditions; therefore, past fluctuations in glacier extent can be used to reconstruct valuable paleoclimatic records. Here, we reconstruct local glacier change through the Holocene using lake sediment analysis, cosmogenic exposure dating and 14C-dating of rooted mosses along recently retreating cold-based ice cap margins in the Sukkertoppen region, western Greenland. 10Be-dated erratics perched on bedrock constrain local deglaciation to 10.0±0.5 ka (n=6), and are in agreement with the lowermost 14C ages from Gnat and Crash proglacial lakes and nonglacial Easy Lake (informal lake names), that provide minimum-limiting ages for deglaciation at 7.9±0.8, 7.5±0.7 and 7.4±0.7 cal yr BP, respectively. Downcore data from Crash Lake reveals a steady decline in minerogenic input until 4.0 cal yr BP suggesting decreasing glacier size through the early to middle Holocene. Distinct transitions from black organic-rich material to mineral-rich sediments occur at 600-900 year cycles after 6.0 ka, and are superimposed on increasing mineral input (glacier growth) through the late Holocene. Radiocarbon ages (n=34) of rooted mosses from 10 different ice caps reflect the onset of Neoglacial snowline lowering 4.5-4.0 cal yr BP in this region. The onset of Neoglacial cooling is followed by a lack of 14C ages in the moss dataset until 2 cal yr BP with the exception of a single 14C age at 3.6 cal yr BP. The paucity of ages during this interval may suggest that there was little or no sustained snowline depression from 4.0-2.0 cal yr BP, or is simply an artifact of too few data. The majority (86%) of 14C ages from the moss dataset occur within the past 2000 years, clustering between 1.9-1.5, 1.3-1.0 and 0.7-0.2 cal yr BP. The intensification of summer cooling and snowline lowering at 2 ka observed in the moss dataset is coincident with the 14C-dated transition from organic-rich to mineral-rich sediments

  3. Lacustrine Records of Holocene Mountain Glacier Fluctuations from Western Greenland

    NASA Astrophysics Data System (ADS)

    Schweinsberg, A.; Briner, J. P.; Bennike, O.

    2014-12-01

    Recent studies have focused on documenting fluctuations of the Greenland Ice Sheet margin throughout the Holocene but few data exist that constrain past changes of local glaciers independent of the ice sheet. Our research combines proglacial lake sediment analysis with cosmogenic 10Be dating of Holocene moraines and radiocarbon dating of ice-cap-killed vegetation with an overall objective to use this multi-proxy approach to generate a detailed record of the coupled climate-glacier system through the Holocene. Here, we present lacustrine records of mountain glacier variability from continuous pro-glacial lake sediment sequences recovered from two glaciated catchments in northeastern Nuussuaq, western Greenland. We use radiocarbon-dated sediments from Sikuiui and Pauiaivik lakes to reconstruct the timing of advance and retreat of local glaciers. Sediments were characterized with magnetic susceptibility (MS), gamma density, Itrax XRF and visible reflectance spectroscopy at 0.2 cm intervals and sediment organic matter at 0.5 cm intervals. Basal radiocarbon ages provide minimum-age constraints on deglaciation from Sikuiui and Pauiaivik lakes of ~9.6 and 8.7 ka, respectively. Organic-rich gyttja from deglaciation until ~5.0 ka in Pauiaivik Lake suggests minimal glacial extent there while slightly elevated MS values from ~9.0 - 7.0 ka in Sikuiui Lake may reflect early Holocene glacial advances. Minerogenic sediment input gradually increases starting at ~5.0 ka in Pauiaivik Lake, which we interpret as the onset of Neoglaciation in the catchment. Furthermore, a distinct episode of enhanced glacial activity from ~4.0 - 2.2 ka in Sikuiui Lake may be correlative to a period of persistent snowline lowering evidenced by radiocarbon dates of ice-killed vegetation from nearby ice cap margins. Results from these lacustrine records and our ice-killed vegetation dataset suggest a middle Holocene onset of Neoglaciation ~5.0 - 4.0 ka in this region. We are supplementing these records

  4. The Photographic History of Greenland's Glaciers - and how the historical data plays an important role in today's glacier research

    NASA Astrophysics Data System (ADS)

    Bjork, A. A.; Kjeldsen, K. K.; Korsgaard, N. J.; Aagaard, S.; Andresen, C. S.; Bamber, J. L.; van den Broeke, M.; Colgan, W. T.; Funder, S.; Khan, S. A.; Larsen, N. K.; Machguth, H.; Nuth, C.; Schomacker, A.; Kjaer, K. H.

    2015-12-01

    As the Greenland Ice Sheet and Greenland's glaciers are continuing to loss mass at high rates, knowledge of their past response to climatic changes is ever important. By harvesting the archives for images, both terrestrial and airborne, we are able to expand the record of glacier observation by several decades, thus supplying crucial knowledge on glacier behavior to important climatic transitions such as the end of the Little Ice Age and the early 20th Century warming. Here we show how a large collection of historical aerial images portray the glacial response to the Little Ice Age deglaciation in Greenland and document frontal change throughout the 20th Century. A detailed story of the LIA-deglaciation is told by supplementing with terrestrial photos that capture the onset of retreat and high resolution aerial images that portray geomorphological evidence of the Little Ice Age maximum extent. This work is the result of several generations of Greenland researches and their efforts to portray and document the state of the glaciers, and highlights that while interpretations and conclusions may be challenged and changed through time, the raw observations remain extremely valuable. Finally, we also show how archival data besides photos may play an important role in future glacier research in Greenland.

  5. Ice Flow in the Humboldt, Petermann, and Ryder Glaciers, North Greenland

    NASA Technical Reports Server (NTRS)

    Joughin, I.; Fahnestock, M.; Kwok, R.; Gogineni, P.; Allen, C.

    1998-01-01

    Radar Interferometry, ice-penetrating radar profiles, and an elevation model are used to determine the catchment area, rates of ice discharge, and approximate states of balance for three large outlet glaciers in northeast Greenland.

  6. Ice Flow in the Humboldt, Petermann, and Ryder Glaciers, North Greenland

    NASA Technical Reports Server (NTRS)

    Joughin, I.; Fahnestock, M.; Kwok, R.; Gogineni, P.; Allen, C.

    1998-01-01

    Radar Interferometry, ice-penetrating radar profiles, and an elevation model are used to determine the catchment area, rates of ice discharge, and approximate states of balance for three large outlet glaciers in northeast Greenland.

  7. The impact of glacier geometry on meltwater plume structure and submarine melt in Greenland fjords

    NASA Astrophysics Data System (ADS)

    Carroll, D.; Sutherland, D. A.; Hudson, B.; Moon, T.; Catania, G. A.; Shroyer, E. L.; Nash, J. D.; Bartholomaus, T. C.; Felikson, D.; Stearns, L. A.; Noël, B. P. Y.; Broeke, M. R.

    2016-09-01

    Meltwater from the Greenland Ice Sheet often drains subglacially into fjords, driving upwelling plumes at glacier termini. Ocean models and observations of submarine termini suggest that plumes enhance melt and undercutting, leading to calving and potential glacier destabilization. Here we systematically evaluate how simulated plume structure and submarine melt during summer months depends on realistic ranges of subglacial discharge, glacier depth, and ocean stratification from 12 Greenland fjords. Our results show that grounding line depth is a strong control on plume-induced submarine melt: deep glaciers produce warm, salty subsurface plumes that undercut termini, and shallow glaciers produce cold, fresh surface-trapped plumes that can overcut termini. Due to sustained upwelling velocities, plumes in cold, shallow fjords can induce equivalent depth-averaged melt rates compared to warm, deep fjords. These results detail a direct ocean-ice feedback that can affect the Greenland Ice Sheet.

  8. Variations of algal communities cause darkening of a Greenland glacier.

    PubMed

    Lutz, Stefanie; Anesio, Alexandre M; Jorge Villar, Susana E; Benning, Liane G

    2014-08-01

    We have assessed the microbial ecology on the surface of Mittivakkat glacier in SE-Greenland during the exceptional high melting season in July 2012 when the so far most extreme melting rate for the Greenland Ice Sheet has been recorded. By employing a complementary and multi-disciplinary field sampling and analytical approach, we quantified the dramatic changes in the different microbial surface habitats (green snow, red snow, biofilms, grey ice, cryoconite holes). The observed clear change in dominant algal community and their rapidly changing cryo-organic adaptation inventory was linked to the high melting rate. The changes in carbon and nutrient fluxes between different microbial pools (from snow to ice, cryoconite holes and glacial forefronts) revealed that snow and ice algae dominate the net primary production at the onset of melting, and that they have the potential to support the cryoconite hole communities as carbon and nutrient sources. A large proportion of algal cells is retained on the glacial surface and temporal and spatial changes in pigmentation contribute to the darkening of the snow and ice surfaces. This implies that the fast, melt-induced algal growth has a high albedo reduction potential, and this may lead to a positive feedback speeding up melting processes.

  9. Middle to late Holocene fluctuations of the Vindue glacier, an outlet glacier of the Greenland Ice Sheet, central East Greenland.

    NASA Astrophysics Data System (ADS)

    Levy, L.; Hammer, S. K.; Kelly, M. A.; Lowell, T. V.; Hall, B. L.; Howley, J. A.; Wilcox, P.; Medford, A.

    2014-12-01

    The margins of the Greenland Ice Sheet are currently responding to present-day climate changes. Determining how the ice sheet margins have responded to past climate changes provides a means to understand how they may respond in the future. Here we present a multi-proxy record used to reconstruct the Holocene fluctuations of the Vindue glacier, an ice sheet outlet glacier in eastern Greenland. Lake sediment cores from Qiviut lake (informal name), located ~0.75 km from the present-day Vindue glacier margin contain a sharp transition from medium sand/coarse silt to laminated gyttja just prior to 6,340±130 cal yr BP. We interpret this transition to indicate a time when the Vindue glacier retreated sufficiently to cease glacial sedimentation into the lake basin. Above this contact the core contains laminated gyttja with prominent, ~0.5 cm thick, silt layers. 10Be ages of boulders on bedrock located between Qiviut lake and the present-day ice margin date to 6.81 ± 0.67 ka (n = 3), indicating the time of deglaciation. These ages also agree well with the radiocarbon age of the silt-gyttja transition in Qiviut lake cores. 10Be ages on boulders on bedrock located more proximal to the ice margin (~0.5 km) yield ages of 2.67 ± 0.18 ka (n = 2). These ages indicate either the continued recession of the ice margin during the late Holocene or an advance at this time. Boulders on the historical moraines show that ice retreated from the moraine by AD 1620 ± 20 yrs (n = 2). These results are in contrast with some areas of the western margin of the ice sheet where 10Be ages indicate that the ice sheet was behind its Historical limit from the middle Holocene (~6-7 ka) to Historical time. This may indicate that the eastern margin may have responded to late Holocene cooling more sensitively or that the advance associated with the Historical moraines overran any evidence of late Holocene fluctuations along the western margin of the ice sheet.

  10. Mechanisms that Amplify, Attenuate and Deviate Glacier Response to Climate Change in Central East Greenland. (Invited)

    NASA Astrophysics Data System (ADS)

    Jiskoot, H.

    2013-12-01

    A multidecadal review of glacier fluctuations and case-studies of glacier processes and environments in central East Greenland will be used to demonstrate Mechanisms that Amplify, Attenuate and Deviate glacier response to climate forcings (MAAD). The different spatial and temporal scales at which MAAD affect mass balance and ice flow may complicate interpretation and longterm extrapolation of glacier response to climate change. A framework of MAAD characterisation and best-practice for interpreting climate signals while taking into account MAAD will be proposed. Glaciers in the Watkins Bjerge, Geikie Plateau and Stauning Alps regions of central East Greenland (68°-72°N) contain about 50000 km2 of glacierized area peripheral to the Greenland Ice Sheet. Within the region, large north-south and coast-inland climatic gradients, as well as complicated topography and glacier dynamics, result in discrepant glacier behaviour. Average retreat rates have doubled from about 2 to 4 km2 a-1 between the late 20th and early 21st centuries. However, glaciers terminating along the Atlantic coast display two times the retreat, thinning, and acceleration rates compared to glaciers terminating in inland fjords or on land. Despite similar climatic forcing variable glacier behaviour is apparent: individual glacier length change ranges from +57 m a-1 to -428 m a-1, though most retreat -20 to -100 m a-1. Interacting dynamic, mass balance and glacio-morphological mechanisms can amplify, attenuate or deviate glacier response (MAAD) to climate change, thus complicating the climatological interpretation of glacier length, area, and thickness changes. East Greenland MAAD include a range of common positive and negative feedback mechanisms in surface mass balance and terminus and subglacial boundary conditions affecting ice flow, but also mechanisms that have longterm or delayed effects. Certain MAAD may affect glacier change interpretation on multiple timescales: e.g. surging glaciers do not

  11. Tomographic Observation and Bedmapping of Glaciers in Western Greenland with IceBridge Sounding Radar

    NASA Technical Reports Server (NTRS)

    Wu, Xiaoqing; Paden, John; Jezek, Ken; Rignot, Eric; Gim, Young

    2013-01-01

    We produced the high resolution bedmaps of several glaciers in western Greenland from IceBridge Mission sounding radar data using tomographic sounding technique. The bedmaps cover 3 regions: Russell glaciers, Umanaq glaciers and Jakobshavn glaciers of western Greenland. The covered areas is about 20x40 km(sup 2) for Russell glaciers and 300x100 sq km, and 100x80 sq km for Jakobshavn glaciers. The ground resolution is 50 meters and the average ice thickness accuracy is 10 to 20 meters. There are some void areas within the swath of the tracks in the bedmaps where the ice thickness is not known. Tomographic observations of these void areas indicate that the surface and shallow sub-surface pockets, likely filled with water, are highly reflective and greatly weaken the radar signal and reduce the energy reaching and reflected from the ice sheet bottom.

  12. Tomographic Observation and Bedmapping of Glaciers in Western Greenland with IceBridge Sounding Radar

    NASA Technical Reports Server (NTRS)

    Wu, Xiaoqing; Paden, John; Jezek, Ken; Rignot, Eric; Gim, Young

    2013-01-01

    We produced the high resolution bedmaps of several glaciers in western Greenland from IceBridge Mission sounding radar data using tomographic sounding technique. The bedmaps cover 3 regions: Russell glaciers, Umanaq glaciers and Jakobshavn glaciers of western Greenland. The covered areas is about 20x40 km(sup 2) for Russell glaciers and 300x100 sq km, and 100x80 sq km for Jakobshavn glaciers. The ground resolution is 50 meters and the average ice thickness accuracy is 10 to 20 meters. There are some void areas within the swath of the tracks in the bedmaps where the ice thickness is not known. Tomographic observations of these void areas indicate that the surface and shallow sub-surface pockets, likely filled with water, are highly reflective and greatly weaken the radar signal and reduce the energy reaching and reflected from the ice sheet bottom.

  13. Recent ice mass loss of outlet glaciers and ice caps in the Qaanaaq region, northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Sugiyama, S.; Tsutaki, S.; Sakakibara, D.; Jun, S.; Yoshihiko, O.; Mihiro, M.; Naoki, K.; Podolskiy, E. A.; Minowa, M.; Satoshi, M.; Takanobu, S.; Matoba, S.; Martin, F.; Genco, R.; Enomoto, H.

    2016-12-01

    The Greenland ice sheet and peripheral ice caps are rapidly losing mass. Recently, ice mass loss is increasing particularly in northwestern Greenland (e.g. Enderlin et al., GRL 2014). It is urgently important to understand the ongoing changes in this region, but observational data are sparse in northern Greenland. To quantify current ice mass loss in northwestern Greenland and better understand processes driving the mass loss, we studied outlet glaciers and ice caps in the Qaanaaq region (Fig. 1). This was a part of a Japanese integrated Arctic research project, GRENE Arctic Climate Change Research Project. Field and satellite observations were performed to quantify ice surface elevation change of outlet glaciers and ice caps (Saito et al., Polar Science 2016; Tsutaki et al., J. Glaciol. in press). Frontal position and ice speed of outlet glaciers were mapped by satellite data. We also studied processes occurring near the front of outlet glaciers to investigate interaction of the glaciers and the ocean (Ohashi et al., Polar Science in press). Our field activities include mass balance monitoring on Qaanaaq Ice Cap since 2012 (Sugiyama et al., Ann. Glaciol. 2014), integrated field observations near the calving front of Bowdoin Glacier since 2013 (Sugiyama et al., J. Glaciol. 2015; Podolskiy et al., GRL 2016), and ocean measurements in front of the glaciers. In this contribution, we present the overview of the results obtained in the GRENE project, and introduce a new project established under the framework of ArCS (Arctic Challenge for Sustainability Project).

  14. A novel multispectral glacier mapping method and its performance in Greenland

    NASA Astrophysics Data System (ADS)

    Citterio, M.; Fausto, R. S.; Ahlstrom, A. P.; Andersen, S. B.

    2014-12-01

    Multispectral land surface classification methods are widely used for mapping glacier outlines. Significant post-classification manual editing is typically required, and mapping glacier outlines over larger regions remains a rather labour intensive task. In this contribution we introduce a novel method for mapping glacier outlines from multispectral satellite imagery, requiring only minor manual editing.Over the last decade GLIMS (Global Land Ice Measurements from Space) improved the availability of glacier outlines, and in 2012 the Randolph Glacier Inventory (RGI) attained global coverage by compiling existing and new data sources in the wake of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5). With the launch of Landsat 8 in 2013 and the upcoming ESA (European Space Agency) Sentinel 2 missions, the availability of multispectral imagery may grow faster than our ability to process it into timely and reliable glacier outline products. Improved automatic classification methods would enable a full exploitation of these new data sources.We outline the theoretical basis of the proposed classification algorithm, provide a step by step walk-through from raw imagery to finished ice cover grids and vector glacier outlines, and evaluate the performance of the new method in mapping the outlines of glaciers, ice caps and the Greenland Ice Sheet from Landsat 8 OLI imagery. The classification output is compared against manually digitized ice margin positions, the RGI vectors, and the PROMICE (Programme for Monitoring of the Greenland Ice Sheet) aerophotogrammetric map of Greenland ice masses over a sector of the Disko Island surge cluster in West Greenland, the Qassimiut ice sheet lobe in South Greenland, and the A.P. Olsen ice cap in NE Greenland.

  15. A 70-year record of outlet glacier retreat in northern Greenland

    NASA Astrophysics Data System (ADS)

    Hill, Emily; Carr, Rachel; Stokes, Chris; Gudmundsson, Hilmar

    2017-04-01

    Over the past two decades, the Greenland Ice Sheet (GrIS) has undergone accelerated mass loss increasing its contribution to sea level rise. This is partly attributed to increased mass loss from dynamic marine-terminating outlet glaciers. Despite marine-terminating outlet glaciers in northern Greenland draining 40% of the ice sheet by area, they are comparatively less well-studied than other regions of the ice sheet (e.g. central west or south-east). This region could be susceptible to marine-ice sheet instability due to large proportions of the bedrock rested below sea level and is also unique in the presence of large floating ice tongues. Here, we use a range of satellite imagery sources, accompanied by historical maps, to examine multi-decadal front position changes at 21 outlet glaciers in northern Greenland between 1948 and 2016. We accompany these terminus changes, with annual records of ice velocity, climate-ocean forcing data, and glacier-specific factors (e.g. fjord-width and basal topography) to understand the dominant forcing on glacier dynamics in the region. Over the last 70 years, there has been a clear pattern of glacier retreat in northern Greenland. This is particularly notable during the last two decades, where 62% of our study glaciers showed accelerated retreat. This was most notable at Humboldt, Tracy, Hagen Brae, C. H. Ostenfeld and Petermann Glaciers, and in the case of the latter three glaciers, this involved substantial retreat of their floating ice tongues (> 10 km). Alongside retreat, several study glaciers underwent simultaneous velocity increases. However, the collapse of floating ice tongues did not always result in increased velocity. Similar to other regions of the ice sheet, recent glacier retreat in the northern regions of the Greenland Ice Sheet could be linked to climatic-oceanic forcing, but at this stage this remains largely unknown. This response to external forcing is further complicated by the presence of glacier

  16. Ocean Melting Greenland (OMG) bathymetric survey of northwest Greenland and implications for the recent evolution of its glaciers

    NASA Astrophysics Data System (ADS)

    Wood, M.; Rignot, E. J.; Willis, J. K.; Fenty, I. G.

    2015-12-01

    Oceans Melting Greenland (OMG) is a five-year Earth Ventures Suborbital Mission funded by NASA to investigate the role of the oceans in ice loss around the margins of the Greenland Ice Sheet, which includes measurements of seafloor bathymetry from multibeam surveys and airborne gravity, glacier surface elevation from high-frequency radar interferometry, and temperature/salinity/depth from vessels and airborne-dropped probes. Here, we describe the results of the 2016 bathymetry survey of northwest Greenland that took place in the summer of 2015: july 22-August 19 and Sept 2-Sept 16 spanning from Ilulissat to Thule AFB in north Greenland, and to be complemented by a survey of southeast Greenland in 2016. We deployed a multibeam Reson 7160 with 512 beams installed on the hull of the Cape Race vessel, with enhanced capabilities for fjord wall and ice face mapping. The survey tracks were optimized based on the IBCAO3 database, recent cruises, airborne gravity data collected by NASA Operation IceBridge which indicated the presence of troughs, bed topography mapped inland using a mass conservation approach, the spatial distribution of ice discharge to locate the largest outlets and maximizing the number of major fjords sampled during the survey, with the goal to identify all troughs that are major pathways for subsurface ocean heat, and constrain as many glacier ice front thickness as permitted by time and the practicality of navigating the ice-choked fjords. The data reveal many deep, U-shaped, submarine valleys connected to the glaciers, intercut with sills and over deepened in narrower passages where former glaciers and ice streams merged into larger units; as well as fjords ending in shallow plateaus with glaciers in retreated positions. The presence of warm, salty water of Atlantic origin (AW) in the fjords is documented using CTD. Some glaciers sit on shallow plateaus in cold, fresh polar waters (PW) at the end of deep fjords, while others are deeper and standing in

  17. Mapping tide-water glacier dynamics in east Greenland using landsat data

    USGS Publications Warehouse

    Dwyer, John L.

    1995-01-01

    Landsat multispectral scanner and thematic mapper images were co-registered For the Kangerdlugssuaq Fjord region in East Greenland and were used to map glacier drainage-basin areas, changes in the positions of tide-water glacier termini and to estimate surface velocities of the larger tide-water glaciers. Statistics were compiled to document distance and area changes to glacier termini. The methodologies developed in this study are broadly applicable to the investigation of tide-water glaciers in other areas. The number of images available for consecutive years and the accuracy with which images are co-registered are key factors that influence the degree to which regional glacier dynamics can be characterized using remotely sensed data.Three domains of glacier state were interpreted: net increase in terminus area in the southern part of the study area, net loss of terminus area for glaciers in upper Kangerdlugssuaq Fjord and a slight loss of glacier terminus area northward from Ryberg Fjord. Local increases in the concentrations of drifting icebergs in the fjords coincide with the observed extension of glacier termini positions Ice-surface velocity estimates were derived for several glaciers using automated image cross-correlation techniques The velocity determined for Kangerdlugssuaq Gletscher is approximately 5.0 km a−1 and that for Kong Christian IV Gletscher is 0.9 km a−1. The continuous presence of icebergs and brash ice in front of these glaciers indicates sustained rates of ice-front calving.

  18. Spatiotemporal variability of oxygen isotope compositions in three contrasting glacier river catchments in Greenland

    NASA Astrophysics Data System (ADS)

    Yde, J. C.; Tvis Knudsen, N.; Steffensen, J. P.; Carrivick, J. L.; Hasholt, B.; Ingeman-Nielsen, T.; Kronborg, C.; Larsen, N. K.; Mernild, S. H.; Oerter, H.; Roberts, D. H.; Russell, A. J.

    2015-06-01

    Analysis of stable oxygen isotope (δ18O) characteristics is a useful tool to investigate water provenance in glacier river systems. In order to attain knowledge on the diversity of spatio-temporal δ18O variations in glacier rivers, we have examined three glacierized catchments in Greenland with different areas, glacier hydrology and thermal regimes. At Mittivakkat Gletscher River, a small river draining a local temperate glacier in southeast Greenland, diurnal oscillations in δ18O occur with a three-hour time lag to the diurnal oscillations in runoff. Throughout the peak flow season the δ18O composition is controlled by the proportion between snowmelt and ice melt with episodic inputs of rainwater and occasional storage and release of a specific water component due to changes in the subglacial drainage system. At Kuannersuit Glacier River on the island Qeqertarsuaq, the δ18O characteristics were examined after the major 1995-1998 glacier surge event. Despite large variations in the δ18O values of glacier ice on the newly formed glacier tongue, there were no diurnal oscillations in the bulk meltwater emanating from the glacier in the post-surge years 2000-2001. In 2002 there were indications of diurnal oscillations, and in 2003 there were large diurnal fluctuations in δ18O. At Watson River, a large catchment at the western margin of the Greenland Ice Sheet, the spatial distribution of δ18O in the river system was applied to fingerprint the relative runoff contributions from sub-catchments. Spot sampling indicates that during the early melt season most of the river water (64-73 %) derived from the Qinnguata Kuussua tributary, whereas the water flow on 23 July 2009 was dominated by bulk meltwater from the Akuliarusiarsuup Kuua tributary (where 7 and 67 % originated from the Russell Glacier and Leverett Glacier sub-catchments, respectively). A comparison of the δ18O compositions from glacial river water in Greenland shows distinct differences between water

  19. Assessing Controls on Oceanic Heat Delivery to Greenland's Marine-Terminating Outlet Glaciers

    NASA Astrophysics Data System (ADS)

    Cowton, T. R.; Nienow, P. W.; Sole, A. J.; Slater, D. A.

    2015-12-01

    The recent retreat of many of Greenland's marine terminating glaciers has been coincident with a period of anomalously warm ocean temperatures. It has been hypothesised that warming ocean waters may affect the stability of glacier termini through an increase in the rate of submarine melting or a decrease in the buttressing influence of sea ice and icebergs, both of which could drive an increase in the rate of mass loss through calving. As Greenland's outlet glaciers typically terminate at the head of lengthy fjord systems, the availability of oceanic heat at the calving front is however dependent not only on the temperature of the water around the Greenland coast, but also on the advection of this heat towards the glaciers by the circulation of the fjord. Assessment of spatial and temporal variation in this up-fjord heat transport may therefore provide a means of examining the role of the ocean in forcing the dynamic variability of these glaciers. The rate at which oceanic heat is delivered to a particular glacier is likely to depend on a range of environmental factors. These may be oceanic (e.g. shelf water temperature), atmospheric (e.g. glacial melt water input, the strength of along-fjord and along-shelf winds) or topographic (e.g. fjord depth, length, width or sinuosity). Here we assess the sensitivity of up-fjord heat flux to each of these parameters by undertaking a suite of experiments using an ocean model (MITgcm), applied to an idealised fjord system. Through this, we identify those factors that are of greatest importance in controlling the delivery of oceanic heat to Greenland's marine-terminating glaciers. Our experiments facilitate assessment of 1) how the influence of the ocean may differ from one marine-terminating glacier to the next and 2) how the oceanic forcing of these glaciers may have changed, and continue to change, over time in response to varying environmental conditions.

  20. Seismic and satellite observations of calving activity at major glacier fronts in Greenland

    NASA Astrophysics Data System (ADS)

    Danesi, Stefania; Salimbeni, Simone; Urbini, Stefano; Pondrelli, Silvia; Margheriti, Lucia

    2016-04-01

    The interaction between oceans and large outlet glaciers in polar regions contributes to the budget of the global water cycle. We have observed the dynamic of sizeable outlet glaciers in Greenland by the analysis of seismic data collected by the regional seismic network Greenland Ice Sheet Monitoring Network (GLISN) trying also to find out correspondence in the glacier tongue evolution derived by the observation of satellite images. By studying the long-period seismic signals at stations located at the mouth of large fjords (e.g. ILULI, NUUG, KULLO), we identify major calving events through the detection of the ground flexure in response to seiche waves generated by iceberg detachments. 
For the time spanning the period between 2010-2014, we fill out calving-event catalogues which can be useful for the estimation of spatial and temporal variations in volume of ice loss at major active fronts in Greenland.

  1. Ensemble simulations of Greenland outlet glaciers into the 21st century

    NASA Astrophysics Data System (ADS)

    Perrette, Mahé; Beckmann, Johanna; Alexander, David; Calov, Reinhard; Ganopolski, Andrey

    2015-04-01

    Greenland ice sheet contribution to sea level rise can be partitioned between increased surface melting and enhanced dynamic discharge in the ocean, via its outlet glaciers. Marine-terminating, outlet glaciers are challenging to include in conventional Greenland-wide ice sheet models because of the large variation in scale between model grid size (typically 10 km) and outlet glacier width (typically 1-5km), making it a subgrid scale feature. A possible approach to tackle this problem is to use one-dimensional flowline models for the individual glaciers (e.g. Nick et al., 2013, Nature), as used in the IPCCAR5, but data are scarce and results are sensitive to model formulation (Enderlin et al 2013a,b, The Cryosphere). Here, we perform an extensive uncertainty analysis of projections into the 21st century with a flowline model by generating an ensemble of simulations for some of the largest Greenland outlet glaciers. Geometry, boundary conditions and forcing are systematically varied within the range of observational uncertainty and to reflect our physical understanding of processes, while remaining consistent with present-day geometry and observed changes. Dominant sources of uncertainty are analyzed and compared between the glaciers.

  2. Study of subaqueous melting of Store Glacier, West Greenland using ocean observations and numerical simulations

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Rignot, E. J.; Menemenlis, D.; van den Broeke, M. R.

    2012-12-01

    Ice discharge from the Greenland Ice Sheet is mainly through tidewater glaciers that terminate in the ocean and melt in contact with ocean waters. Subaqueous melting at the calving front is a direct mechanism for mass loss and a potential trigger for glacier acceleration. We present an analysis of oceanographic data collected in the fjord of Store Glacier, West Greenland during August 2010 and 2012. Using these data, we calculate the subaqueous melt rates. Independently, we employ the Massachusetts Institute of Technology general circulation model (MITgcm), modified to include melting at the calving front and outflow of subglacial water to model the ice melt rates of Store Glacier. Previous 2-D sensitivity studies showed that the subaqueous melt rate reaches several meters per day during the summer, increases non-linearly with subglacial runoff and linearly with ocean thermal forcing, and ceases when subglacial discharge is off during winter. We present new 3-D simulations at very high resolution, with measured oceanic temperature/salinity as boundary conditions, and subglacial runoff from the University of Utrecht's Regional Atmospheric Climate Model outputs on different years and seasons. We compare the ocean observations and numerical simulations and discuss the seasonal and inter-annual variations of subaqueous melting. This study helps evaluate the impact of the ocean on the subaqueous melting of Greenland tidewater glaciers and in turn on glacier mass balance. This work was carried out at University of California, Irvine and at the Jet Propulsion Laboratory under contract with NASA Cryosphere Science Program.

  3. Short-term variations in the dynamics of Bowdoin Glacier in northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Minowa, Masahiro; Sugiyama, Shin; Sawagaki, Takanobu; Tsutaki, Shun; Sakakibara, Daiki

    2016-04-01

    Tidewater glaciers in Greenland ice sheet are rapidly retreating by under the influence of changes in ice dynamics. For example, Bowdoin Glacier began rapid retreat in 2008, which was accompanied by significant acceleration near the glacier front. Submarine melting and ice-mélange weakening are suspected as triggering mechanisms of the rapid retreat of tidewater glaciers in the Greenland ice sheet, but details of processes at the ice-ocean interface are poorly understood. To better understand these processes, we measured ice-front position of Bowdoin Glacier in northwestern Greenland and glacier/ice-mélange movement in front of the glacier. The glacier/ice-mélange measurement was performed by processing 3-hourly photographs taken by a time-lapse camera operated over two years since July 2013. We also operated a dual-frequency GPS at 3 km from the calving front to measure ice speed from May to July in 2014 and 2015. The image analysis revealed clear seasonal variations in the ice-front position with an amplitude of ~200 m. Seasonal changes were also observed in ice speed along the center of the glacier (amplitude ~50%). During summer, the ice-front position was relatively stable, but retreated occasionally by large calving events. These events occurred near upwelling of subglacial discharge, where a large submarine melt rate is expected. The glacier began to advance in September approximately when daily mean air temperature dropped below 0°C. The glacier advanced the most in winter when the fjord was covered by ice-mélange. After winter, extended portion of the glacier rapidly disintegrated by a few calving events. Such event coincided with onset of ice-mélange movement in front of the glacier. This movement occurs when air temperature above 0°C and high wind speed were observed, suggesting the calving event was due to decrease in the mechanical support from the ice-mélange. These results indicate both ice-mélange and submarine melting play roles in

  4. Ice sheets. Reverse glacier motion during iceberg calving and the cause of glacial earthquakes.

    PubMed

    Murray, T; Nettles, M; Selmes, N; Cathles, L M; Burton, J C; James, T D; Edwards, S; Martin, I; O'Farrell, T; Aspey, R; Rutt, I; Baugé, T

    2015-07-17

    Nearly half of Greenland's mass loss occurs through iceberg calving, but the physical mechanisms operating during calving are poorly known and in situ observations are sparse. We show that calving at Greenland's Helheim Glacier causes a minutes-long reversal of the glacier's horizontal flow and a downward deflection of its terminus. The reverse motion results from the horizontal force caused by iceberg capsize and acceleration away from the glacier front. The downward motion results from a hydrodynamic pressure drop behind the capsizing berg, which also causes an upward force on the solid Earth. These forces are the source of glacial earthquakes, globally detectable seismic events whose proper interpretation will allow remote sensing of calving processes occurring at increasing numbers of outlet glaciers in Greenland and Antarctica.

  5. A moderate resolution inventory of small glaciers and ice caps surrounding Greenland and the Antarctic peninsula

    NASA Astrophysics Data System (ADS)

    Chen, C.; Box, J. E.; Hock, R. M.; Cogley, J. G.

    2011-12-01

    Current estimates of global Mountain Glacier and Ice Caps (MG&IC) mass changes are subject to large uncertainties due to incomplete inventories and uncertainties in land surface classification. This presentation features mitigative efforts through the creation of a MODIS dependent land ice classification system and its application for glacier inventory. Estimates of total area of mountain glaciers [IPCC, 2007] and ice caps (including those in Greenland and Antarctica) vary 15%, that is, 680 - 785 10e3 sq. km. To date only an estimated 40% of glaciers (by area) is inventoried in the World Glacier Inventory (WGI) and made available through the World Glacier Monitoring System (WGMS) and the National Snow and Ice Data Center [NSIDC, 1999]. Cogley [2009] recently compiled a more complete version of WGI, called WGI-XF, containing records for just over 131,000 glaciers, covering approximately half of the estimated global MG&IC area. The glaciers isolated from the conterminous Antarctic and Greenland ice sheets remain incompletely inventoried in WGI-XF but have been estimated to contribute 35% to the MG&IC sea-level equivalent during 1961-2004 [Hock et al., 2009]. Together with Arctic Canada and Alaska these regions alone make up almost 90% of the area that is missing in the global WGI-XF inventory. Global mass balance projections tend to exclude ice masses in Greenland and Antarctica due to the paucity of data with respect to basic inventory base data such as area, number of glaciers or size distributions. We address the need for an accurate Greenland and Antarctic peninsula land surface classification with a novel glacier surface classification and inventory based on NASA Moderate Resolution Imaging Spectroradiometer (MODIS) data gridded at 250 m pixel resolution. The presentation includes a sensitivity analysis for surface mass balance as it depends on the land surface classification. Works Cited +Cogley, J. G. (2009), A more complete version of the World Glacier

  6. Stable oxygen isotope variability in two contrasting glacier river catchments in Greenland

    NASA Astrophysics Data System (ADS)

    Yde, Jacob C.; Knudsen, Niels T.; Steffensen, Jørgen P.; Carrivick, Jonathan L.; Hasholt, Bent; Ingeman-Nielsen, Thomas; Kronborg, Christian; Larsen, Nicolaj K.; Mernild, Sebastian H.; Oerter, Hans; Roberts, David H.; Russell, Andrew J.

    2016-03-01

    Analysis of stable oxygen isotope (δ18O) characteristics is a useful tool to investigate water provenance in glacier river systems. In order to attain knowledge on the diversity of δ18O variations in Greenlandic rivers, we examined two contrasting glacierised catchments disconnected from the Greenland Ice Sheet (GrIS). At the Mittivakkat Gletscher river, a small river draining a local temperate glacier in southeast Greenland, diurnal oscillations in δ18O occurred with a 3 h time lag to the diurnal oscillations in run-off. The mean annual δ18O was -14.68 ± 0.18 ‰ during the peak flow period. A hydrograph separation analysis revealed that the ice melt component constituted 82 ± 5 % of the total run-off and dominated the observed variations during peak flow in August 2004. The snowmelt component peaked between 10:00 and 13:00 local time, reflecting the long travel time and an inefficient distributed subglacial drainage network in the upper part of the glacier. At the Kuannersuit Glacier river on the island Qeqertarsuaq in west Greenland, the δ18O characteristics were examined after the major 1995-1998 glacier surge event. The mean annual δ18O was -19.47 ± 0.55 ‰. Despite large spatial variations in the δ18O values of glacier ice on the newly formed glacier tongue, there were no diurnal oscillations in the bulk meltwater emanating from the glacier in the post-surge years. This is likely a consequence of a tortuous subglacial drainage system consisting of linked cavities, which formed during the surge event. Overall, a comparison of the δ18O compositions from glacial river water in Greenland shows distinct differences between water draining local glaciers and ice caps (between -23.0 and -13.7 ‰) and the GrIS (between -29.9 and -23.2 ‰). This study demonstrates that water isotope analyses can be used to obtain important information on water sources and the subglacial drainage system structure that is highly desired for understanding glacier hydrology.

  7. Inland thinning on the Greenland ice sheet controlled by outlet glacier geometry

    NASA Astrophysics Data System (ADS)

    Felikson, Denis; Bartholomaus, Timothy C.; Catania, Ginny A.; Korsgaard, Niels J.; Kjær, Kurt H.; Morlighem, Mathieu; Noël, Brice; van den Broeke, Michiel; Stearns, Leigh A.; Shroyer, Emily L.; Sutherland, David A.; Nash, Jonathan D.

    2017-04-01

    Greenland’s contribution to future sea-level rise remains uncertain and a wide range of upper and lower bounds has been proposed. These predictions depend strongly on how mass loss--which is focused at the termini of marine-terminating outlet glaciers--can penetrate inland to the ice-sheet interior. Previous studies have shown that, at regional scales, Greenland ice sheet mass loss is correlated with atmospheric and oceanic warming. However, mass loss within individual outlet glacier catchments exhibits unexplained heterogeneity, hindering our ability to project ice-sheet response to future environmental forcing. Using digital elevation model differencing, we spatially resolve the dynamic portion of surface elevation change from 1985 to present within 16 outlet glacier catchments in West Greenland, where significant heterogeneity in ice loss exists. We show that the up-glacier extent of thinning and, thus, mass loss, is limited by glacier geometry. We find that 94% of the total dynamic loss occurs between the terminus and the location where the down-glacier advective speed of a kinematic wave of thinning is at least three times larger than its diffusive speed. This empirical threshold enables the identification of glaciers that are not currently thinning but are most susceptible to future thinning in the coming decades.

  8. Cryo-life habitability on a polythermal glacier in Greenland

    NASA Astrophysics Data System (ADS)

    Lutz, S.; Anesio, A. M.; Benning, L. G.

    2012-12-01

    Modern surface glacial ice and snow are extreme environments at the edge of Earth's biosphere and potential sites of biosignatures in future planetary missions. The primary colonization of snow and ice is an important biogeological scenario with clear implications for the life detection on other icy planets [1]. Hence, knowledge of the adaptations and survival strategies adopted by extremophiles - cryophiles - in terrestrial cryogenic environments is vital for our ability to process data from future planetary missions. Despite it being one of the most extreme habitats on Earth, glacial ice and snow fields are colonised by a plethora of organisms including snow algae, bacteria, fungi, protozoa, rotifers and even invertebrates [2]. Although low in number and diversity compared to other habitats, snow and ice algae are a major primary producer in glacial settings [3,4]. Their life cycle influences the structure and diversity of neighbouring microbial communities [5] and they produce a suite of complex molecules to protect themselves against cold [6], UV [7], or nutrient deficiency [8]. However, these adaptations are poorly understood and we know very little about the complexity of the biological inventory contained within snow and ice environments. We have been investigating the potential of carbon fluxes from snow to ice, cryoconites and runoff water on the polythermal Mittivakkat glacier in SE Greenland and the effect of cell retention at the glacial surface on the albedo. The complementary microbiological and geochemical characteristics have been characterized at a suite of sampling sites in the ablation, superimposed and accumulation zone of the glacier. Results from photosynthesis and respiration measurements (e.g., snow fields, cryoconites, glacial outflow, clean snow) show that snow and ice surfaces have the potential to accumulate algal cells which become an important source of organic carbon for cryoconites. The accumulation of cells at the glacial surface

  9. Increased glacier runoff enhances the penetration of warm Atlantic Water into a large Greenland fjord

    NASA Astrophysics Data System (ADS)

    Sole, Andrew; Payne, Anthony; Nienow, Peter; Christoffersen, Poul; Cottier, Finlo; Inall, Mark

    2013-04-01

    The retreat and acceleration of Greenland's marine-terminating outlet glaciers have been linked to ocean warming. However the mechanisms which control the transmission of this warming along fjords towards the glacier termini remain poorly understood. Here we aim to elucidate observed changes in water properties in Kangerdlugssuaq Fjord (KF), east Greenland, between 1993 and 2004 using the Bergen Ocean Model (BOM). Model outputs are compared with observed potential temperature, salinity and velocity data to determine the principal controls on heat transport within KF. The BOM includes wind, tidal and glacier runoff forcing and is able to replicate observed temperature and salinity profiles. Model results describe a robust four-layer estuarine flow, consisting of two distinct circulations. The shallow circulation (0 - ˜60 m) is forced by surface wind stress and to a lesser extent supraglacial runoff, while the intermediate circulation (˜60 - 500 m) is driven by runoff discharged into the fjord subglacially. AtlanticWater (AW) and warm Polar Surface Water (PSWw) are drawn into the fjord by the intermediate and shallow circulation cells respectively, in a pattern consistent with observations, and AW reaches Kangerdlugssuaq Glacier (at the fjord head) over a single summer. Along-fjord heat transport towards KG increases significantly with both glacier runoff and coastal water temperature. A doubling of glacier runoff produces a 29 % (48 %) amplification of mean annual (summer) heat transport towards the KG terminus. Our model shows, in agreement with observations, that maximum submarine melt rates occur when AW and PSWw are present at the fjord mouth and, crucially, glacier runoff is also high. Rising ice sheet runoff therefore increases the sensitivity of KG (and other Greenland marine-terminating glaciers) to ocean warming.

  10. Adjacent fjords and glaciers respond differently to ice sheet surface melt in West Greenland

    NASA Astrophysics Data System (ADS)

    Bartholomaus, T. C.; Stearns, L. A.; Sutherland, D.; Shroyer, E.; Nash, J. D.; Walker, R. T.; Catania, G. A.; Felikson, D.; Carroll, D.; Fried, M.; Noel, B.; van den Broeke, M. R.

    2016-12-01

    Neighboring tidewater glaciers often exhibit asynchronous dynamic behavior, despite relatively uniform regional atmospheric and oceanic forcings. This variability may be controlled by a combination of local factors, including glacier and fjord geometry, fjord heat content and circulation, and glacier surface melt. In order to characterize and understand contrasts in adjacent tidewater glacier and fjord dynamics, we made coincident ice-ocean-atmosphere observations at high temporal resolution (minutes to weeks) within a 10,000 km^2 area near Uummannaq, Greenland. Water column velocity, temperature and salinity measurements reveal systematic differences in neighboring fjords that imply contrasting circulation patterns. The observed ocean velocity and hydrography, combined with numerical modeling, suggest that subglacial discharge plays a major role in setting fjord conditions. In addition, satellite remote sensing of seasonal ice flow speed and terminus position reveal both speedup and slow-down in response to melt, as well as differences in calving style among the neighboring glaciers. Glacier force budgets and modeling also point toward subglacial discharge as a key factor in glacier behavior. For the studied region, individual glacier and fjord geometry modulate subglacial discharge, which leads to contrasts in both fjord and glacier dynamics.

  11. The first complete inventory of the local glaciers and ice caps on Greenland

    NASA Astrophysics Data System (ADS)

    Rastner, P.; Bolch, T.; Mölg, N.; Machguth, H.; Le Bris, R.; Paul, F.

    2012-12-01

    Glacier inventories provide essential baseline information for the determination of water resources, glacier-specific changes in area and volume, climate change impacts as well as past, potential and future contribution of glaciers to sea-level rise. Although Greenland is heavily glacierised and thus highly relevant for all of the above points, a complete inventory of its glaciers was not available so far. Here we present the results and details of a new and complete inventory that has been compiled from more than 70 Landsat scenes (mostly acquired between 1999 and 2002) using semi-automated glacier mapping techniques. A digital elevation model (DEM) was used to derive drainage divides from watershed analysis and topographic attributes for each glacier entity. To serve the needs of different user communities, we assigned to each glacier one of three connectivity levels with the ice sheet (CL0, CL1, CL2; i.e. no, weak, and strong connection) to clearly, but still flexibly, distinguish the local glaciers and ice caps (GIC) from the ice sheet and its outlet glaciers. In total, we mapped ~ 20 300 glaciers larger than 0.05 km2 (of which ~ 900 are marine terminating), covering an area of 130 076 ± 4032 km2, or 89 720 ± 2781 km2 without the CL2 GIC. The latter value is about 50% higher than the mean value of more recent previous estimates. Glaciers smaller than 0.5 km2 contribute only 1.5% to the total area but more than 50% (11 000) to the total number. In contrast, the 25 largest GIC (> 500 km2) contribute 28% to the total area, but only 0.1% to the total number. The mean elevation of the GIC is 1700 m in the eastern sector and around 1000 m otherwise. The median elevation increases with distance from the coast, but has only a weak dependence on mean glacier aspect.

  12. Outlet Glacier and Margin Elevation Changes: Near - Coastal Thinning of The Greenland Ice Sheet

    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.; Busalacchi, Antonio (Technical Monitor)

    2000-01-01

    Repeat surveys by aircraft laser altimeter in 1993/4 and 1998/9 reveal significant thinning along 70% of the coastal parts of the Greenland ice sheet at elevations below about 2000 m. Thinning rates of more than 1 m/yr are common along many outlet glaciers, at all latitudes and, in some cases, at elevations up to 1500 m. Warmer summers along parts of the coast may have caused a few tens of cm/yr additional melting, but most of the observed thinning probably results from increased glacier velocities and associated creep rates. Three glaciers in the northeast all show patterns of thickness change indicative of surging behavior, and one has been independently documented as a surging glacier. There are a few areas of significant thickening (over 1 m/yr), and these are probably related to higher than normal accumulation rates during the observation period.

  13. A Younger Dryas re-advance of local glaciers in north Greenland

    NASA Astrophysics Data System (ADS)

    Larsen, Nicolaj K.; Funder, Svend; Linge, Henriette; Möller, Per; Schomacker, Anders; Fabel, Derek; Xu, Sheng; Kjær, Kurt H.

    2016-09-01

    The Younger Dryas (YD) is a well-constrained cold event from 12,900 to 11,700 years ago but it remains unclear how the cooling and subsequent abrupt warming recorded in ice cores was translated into ice margin fluctuations in Greenland. Here we present 10Be surface exposure ages from three moraines in front of local glaciers on a 50 km stretch along the north coast of Greenland, facing the Arctic Ocean. Ten ages range from 11.6 ± 0.5 to 27.2 ± 0.9 ka with a mean age of 12.5 ± 0.7 ka after exclusion of two outliers. We consider this to be a minimum age for the abandonment of the moraines. The ages of the moraines are furthermore constrained using Optically Stimulated Luminescence (OSL) dating of epishelf sediments, which were deposited prior to the ice advance that formed the moraines, yielding a maximum age of 12.4 ± 0.6 ka, and bracketing the formation and subsequent abandonment of the moraines to within the interval 11.8-13.0 ka ago. This is the first time a synchronous YD glacier advance and subsequent retreat has been recorded for several independent glaciers in Greenland. In most other areas, there is no evidence for re-advance and glaciers were retreating during YD. We explain the different behaviour of the glaciers in northernmost Greenland as a function of their remoteness from the Atlantic Meridional Overturning Circulation (AMOC), which in other areas has been held responsible for modifying the YD drop in temperatures.

  14. Seasonal flow speed variations of marine-terminating outlet glaciers in northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Sakakibara, Daiki; Sugiyama, Shin

    2017-04-01

    The Greenland ice sheet is losing mass under the influence of increases in surface melting and ice discharge from marine-terminating outlet glaciers. To project changes of the ice sheet under the changing climate, better understanding of the dynamics of marine-terminating outlet glaciers is required. To this end, we studied seasonal flow speed variations of 10 marine-terminating outlet glaciers along the coast of the Prudhoe Land, northwestern Greenland. Surface speed near the glacier front was measured using Landsat 8 images taken from 2014 to 2016. We obtained 18-28 speed data for each month from March to September. Area covered by supraglacial ponds and meltwater plume in front of the glacier were mapped by analyzing the Landsat images. Flow speed variations were compared with the ice front positions, sea ice condition near the termini, air temperature, area of supraglacial ponds and meltwater plume to investigate the driver of the seasonal changes in the ice dynamics. All of the study glaciers accelerated from May/June to June/July, and then slowed down from July to September. Magnitude of the speedups ranged between 120 and 680 m a-1. In early summer, flow speed increased as air temperature rose up and the area of supraglacial ponds expanded. These observations suggest that the seasonal speedup was caused by meltwater input to the glacier bed. Flow speed dropped when annual sum of the positive-degree day reached 100 K d, supraglacial water drained and meltwater plume appeared. These changes occurred before air temperature reached the summer maximum. Our interpretation of the glacier deceleration is that subglacial drainage system had developed because of the drainage of supraglacial ponds which lead to the drop in the subglacial water pressure. Our study demonstrated that the rate of meltwater production controls the seasonal acceleration, and the drainage of supraglacial ponds triggers the later deceleration.

  15. Ice dynamics of Bowdoin tidewater glacier, Northwest Greenland, from borehole measurements and numerical modelling

    NASA Astrophysics Data System (ADS)

    Seguinot, Julien; Funk, Martin; Ryser, Claudia; Jouvet, Guillaume; Bauder, Andreas; Sugiyama, Shin

    2016-04-01

    The observed rapid retreat of ocean-terminating glaciers in southern Greenland in the last two decades has now propagated to the northwest. Hence, tidewater glaciers in this area, some of which have remain stable for decades, have started retreating rapidly through iceberg calving in recent years, thus allowing a monitoring and investigation of ice dynamical changes starting from the early stages of retreat. Here, we present an ice dynamical study from Bowdoin Glacier, a tidewater outlet glacier located at the northwestern margin of the Greenland Ice Sheet. The glacier surface experiences lowering at a rate of 1.5 m/a since 2007. A rapid calving front retreat of 260 m/a was also observed since 2008, while no significant changes occurred during the previous 20 years. From July 2014 to July 2015, we monitored, 2 km upstream from the calving front, subglacial water pressure changes in boreholes, internal ice deformation through tilt sensors at different depths, englacial ice temperature profiles from the glacier bed to the surface, and high resolution surface motion from GPS records. These measurement show that the glacier is temperate-based, yet internal deformation accounts for about 10 % of the annual surface motion. A seasonal increase in both deformation and sliding at the onset of the melt season is associated with a drop in water pressure in part of the subglacial system. These observations are used to calibrate the Parallel Ice Sheet Model (PISM) for numerical simulations of ice flow in the Bowdoin Glacier catchment, aiming for a better understanding of iceberg calving processes in relation to changes in internal and basal ice dynamics.

  16. Greenland Ice Sheet Surface Roughness and Glacier Zones from MISR, 2000-2013

    NASA Astrophysics Data System (ADS)

    Nolin, A. W.; Mar, E.

    2014-12-01

    The surface of the Greenland ice sheet is shaped by wind, melt, and glacier dynamics. Surface roughness affects the surface-atmospheric interactions (via the aerodynamic roughness length) and thus influences fluxes of sensible and latent heat at the ice sheet surface. When combined with near-infrared reflectance, surface roughness has been shown to discriminate between glacier zones. We present the first ever annual time series of Greenland ice sheet surface roughness derived from the Multi-angle Imaging SpectroRadiometer (MISR) for the years 2000-2013. Our cloud-free multi-angular measurements are calibrated using airborne LiDAR data from the Airborne Topographic Mapper (ATM). Roughness values range from 10 cm in the dry, snow-covered interior of the ice sheet to over 8 m along the crevassed margins of the ice sheet. Roughness increases from April to July as the surface melts and glaciers become more active. Our roughness maps are restricted to spring and early summer due to limited ATM data. We next employed ISODATA unsupervised clustering with MISR near-infrared reflectance and surface roughness to map glacier zones on the ice sheet for years 2000-2013. The number and locations of the ISODATA-derived glacier zones are consistent from year to year with slight shifts in boundaries depending on the extent of early summer melt. These maps of Greenland ice surface roughness and glacier zones are the result of processing several hundred thousand MISR images and are the first ever full-coverage, annual maps of this kind.

  17. The Subglacial Access and Fast Ice Research Experiment - SAFIRE - on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Christoffersen, P.; Hubbard, B. P.; Doyle, S. H.; Young, T. J.; Hofstede, C. M.; Bougamont, M. H.; Todd, J.; Toberg, N.; Nicholls, K. W.; Box, J.; Walter, J. I.; Hubbard, A.

    2015-12-01

    Marine-terminating outlet glaciers drain 90 percent of the Greenland Ice Sheet and are responsible for about half of the ice sheet's net annual mass loss, which currently raises global sea level by 1 mm per year. The basal controls on these fast-flowing glaciers are, however, poorly understood, with the implication that numerical ice sheet models needed to predict future dynamic ice loss from Greenland relies on uncertain and often untested basal parameterizations. The Subglacial Access and Fast Ice Research Experiment - SAFIRE - is addressing this paucity of observational constraints by drilling to the bed of Store Glacier, a fast-flowing outlet glacier terminating in Uummannaq Fjord, West Greenland. In 2014, we gained access to the bed in four boreholes drilled to depths of 603-616 m near the center of the glacier, 30 km inland from the calving terminus where ice flows at a rate of 700 m/year. A seismic survey showed the glacier bed to consist of water-saturated, soft sediment. The water level in all four boreholes nevertheless dropped rapidly to 80 m below the ice surface when the drill connected with a basal water system, indicating effective drainage over a sedimentary bed. We were able to install wired sensor strings at the bed (water pressure, temperature, electrical conductivity and turbidity) and within the glacier (temperature and tilt) in three boreholes. The sensors operated for up to 80+ days before cables stretched and ultimately snapped due to high internal strain. The data collected during this sensor deployment show ice as cold as -21 degrees Celcius; yet, temperature of water in the basal water system was persistently above the local freezing point. With diurnal variations detected in several sensor records, we hypothesise that surface water lubricates the ice flow while also warming basal ice. The fast basal motion of Store Glacier not only occurs by basal sliding, but from high rates of concentrated strain in the bottom third of the glacier

  18. Air temperature drives 140 years of fluctuations at a major Greenlandic tidewater glacier.

    NASA Astrophysics Data System (ADS)

    Lea, James M.; Mair, Douglas WF; Nick, Faezeh M.; Rea, Brice R.; Nienow, Peter W.

    2014-05-01

    The primary controls on the fluctuations of tidewater glaciers are currently poorly understood. Both oceanic and atmospheric forcing mechanisms have been invoked to explain observed changes. Numerical modelling simulations have previously utilised only relatively short observational records for calibration and validation. Hence the longer term climatic controls on tidewater glacier stability are not well known. Herein we apply a 1-D numerical flow-band model with a crevasse water depth calving criterion (Nick et al., 2010) to Kangiata Nunaata Sermia (KNS), SW Greenland. We force the model using air and sea surface temperature records for the period 1871-2012. Model sensitivity to climate forcing was determined by varying climatic tuning coefficients using a Monte Carlo approach. The output from 1500 model runs was compared against observations of terminus position and glacier geometry from the last 140 years. The results of best-fit model runs were then used to evaluate the relative sensitivity of KNS to changes in atmospheric or oceanic forcing. Our results show that all best-fit model runs have tuning coefficients associated with strong atmospheric forcing, but do not all require strong oceanic forcing. This suggests that changes in air temperature are the primary driver of the terminus fluctuations of KNS from 1866-2012, and may be the principal climatic control on glacier stability for similar tidewater glaciers in Greenland.

  19. Spatio-temporal Variability in the Glacier-Ocean Boundary in Central West Greenland

    NASA Astrophysics Data System (ADS)

    Catania, G. A.; Fried, M.; Bartholomaus, T.; Peters, D.; Felikson, D.; Carroll, D.; Sutherland, D.; Stearns, L. A.; Shroyer, E.; Nash, J. D.

    2015-12-01

    Outlet glacier termini represent the boundary between ice and ocean systems. As such, spatio-termporal differences in terminus shape and position may be indicative of how the ice and ocean systems interact. We examine over 40 years of remote-sensing imagery collected by multiple satellites to characterize the termini of 15 outlet glaciers in Central Western Greenland with unprecedented detail. Our record consists of an average of ~300 terminus observations per glacier; during the last 5 years, we average ~20 observations per year. We find that many glaciers in this region initiated retreat around 1998, coincident with retreat further south at Jakobshavn Isbræ, although the rate and duration of retreat varies from glacier-to-glacier. We explore variations in retreat rate and extent by examining individual fjord geometries, namely changes in fjord width and depth from available ship-based sounding observations. We also explore variations in retreat rate by examining spatial variations in surface melt-induced terminus ablation using a buoyant plume model coupled with field observations. Finally, we identify glaciers in the region that did not undergo significant retreat and examine the balance of forces that may be responsible for their stability.

  20. A 3D Full-Stokes Calving Model Applied to a West Greenland Outlet Glacier

    NASA Astrophysics Data System (ADS)

    Todd, Joe; Christoffersen, Poul; Zwinger, Thomas; Råback, Peter; Chauché, Nolwenn; Hubbard, Alun; Toberg, Nick; Luckman, Adrian; Benn, Doug; Slater, Donald; Cowton, Tom

    2017-04-01

    Iceberg calving from outlet glaciers accounts for around half of all mass loss from both the Greenland and Antarctic ice sheets. The diverse nature of calving and its complex links to both internal dynamics and external climate make it challenging to incorporate into models of glaciers and ice sheets. Consequently, calving represents one of the most significant uncertainties in predictions of future sea level rise. Here, we present results from a new 3D full-Stokes calving model developed in Elmer/Ice and applied to Store Glacier, the second largest outlet glacier in West Greenland. The calving model implements the crevasse depth criterion, which states that calving occurs when surface and basal crevasses penetrate the full thickness of the glacier. The model also implements a new 3D rediscretization approach and a time-evolution scheme which allow the calving front to evolve realistically through time. We use the model to test Store's sensitivity to two seasonal environmental processes believed to significantly influence calving: submarine melt undercutting and ice mélange buttressing. Store Glacier discharges 13.9 km3 of ice annually, and this calving rate shows a strong seasonal trend. We aim to reproduce this seasonal trend by forcing the model with present day levels of submarine melting and ice mélange buttressing. Sensitivity to changes in these frontal processes was also investigated, by forcing the model with a) increased submarine melt rates acting over longer periods of time and b) decreased mélange buttressing force acting over a reduced period. The model displays a range of observed calving behaviour and provides a good match to the observed seasonal evolution of the Store's terminus. The results indicate that ice mélange is the primary driver of the observed seasonal advance of the terminus and the associated seasonal variation in calving rate. The model also demonstrates a significant influence from submarine melting on calving rate. The results

  1. Increased glacier runoff enhances the penetration of warm Atlantic water into a large Greenland fjord

    NASA Astrophysics Data System (ADS)

    Sole, A. J.; Payne, A. J.; Nienow, P. W.; Christoffersen, P.; Cottier, F. R.; Inall, M. E.

    2012-11-01

    The retreat and acceleration of Greenland's marine-terminating outlet glaciers have been linked to ocean warming. However the mechanisms which control the transmission of this warming along fjords towards the glaciers remain poorly understood. The aim of this paper is to elucidate observed changes in water properties in Kangerdlugssuaq Fjord (KF), East Greenland using the Bergen Ocean Model (BOM). Model outputs are compared with observed potential temperature, salinity and velocity data to determine the principal controls on heat transport within KF and to estimate resulting submarine ice front melt rates of Kangerdlugssuaq Glacier (KG). The BOM includes wind, tidal and glacier runoff forcing and is able to replicate observed temperature and salinity profiles. Model results describe a robust four-layer estuarine flow, consisting of two distinct circulations. The shallow circulation (0-~ 60 m) is forced by surface wind stress and to a lesser extent supraglacial runoff, while the intermediate circulation (~ 60-500 m) is driven by runoff discharged into the fjord subglacially. Atlantic Water (AW) and warm Polar Surface Water (PSWw) are drawn into the fjord by the intermediate and shallow circulation cells respectively, in a pattern consistent with observations, and AW reaches KG over a single summer. Along-fjord heat transport towards KG increases significantly with both glacier runoff and coastal water temperature. A doubling of glacier runoff produces a 29% (48%) amplification of mean annual (summer) heat transport towards the KG terminus, increasing estimated mean annual (summer) submarine melt rates from 211 to 273 (842 to 1244) m yr-1. In contrast, heat transport towards KG in the surface ~ 60 m of the fjord decreases with rising glacier runoff because the enhanced down-fjord component of the intermediate circulation interferes with the up-fjord part of the shallow circulation. Thus, as ice sheet runoff increases, KG's dynamic response to oceanic forcing will

  2. Reconstructing the history of major Greenland glaciers since the Little Ice Age

    NASA Astrophysics Data System (ADS)

    Csatho, B. M.; Schenk, A. F.; van der Veen, C. J.; Stearns, L.; Babonis, G. S.

    2008-12-01

    The Greenland Ice Sheet may have been responsible for rapid sea level rise during the last interglacial period and recent studies indicate that it is likely to make a faster contribution to sea-level rise than previously believed. Rapid thinning and velocity increase has been observed on most major outlet glaciers with terminus retreat that might lead to increased discharge from the interior and consequent further thinning and retreat. Potentially, such behavior could have serious implications for global sea level. However, the current thinning may simply be a manifestation of longer-term behavior of the ice sheet as it responds to the general warming following the Little Ice Age (LIA). Although Greenland outlet glaciers have been comprehensively monitored since the 1980s, studies of long-term changes mostly rely on records of the calving front position. Such records can be misleading because the glacier terminus, particularly if it is afloat, can either advance or retreat as ice further upstream thins and accelerates. To assess whether recent trends deviate from longer-term behavior, we examined three rapidly thinning and retreating outlet glaciers, Jakobshavn Isbrae in west, Kangerdlussuaq Glacier in east and Petermann Glacier in northwest Greenland. Glacier surface and trimline elevations, as well as terminus positions were measured using historical photographs and declassified satellite imagery acquired between the 1940s and 1985. These results were combined with data from historical records, ground surveys, airborne laser altimetry, satellite observations and field mapping of lateral moraines and trimlines, to reconstruct the history of changes since the (LIA) up to the present. We identified several episodes of rapid thinning and ice shelf break-up, including thinning episodes that occurred when the calving front was stationary. Coastal weather station data are used to assess the influence of air temperatures and intensity of surface melting, and to isolate

  3. Future sea-level rise from Greenland's main outlet glaciers in a warming climate.

    PubMed

    Nick, Faezeh M; Vieli, Andreas; Andersen, Morten Langer; Joughin, Ian; Payne, Antony; Edwards, Tamsin L; Pattyn, Frank; van de Wal, Roderik S W

    2013-05-09

    Over the past decade, ice loss from the Greenland Ice Sheet increased as a result of both increased surface melting and ice discharge to the ocean. The latter is controlled by the acceleration of ice flow and subsequent thinning of fast-flowing marine-terminating outlet glaciers. Quantifying the future dynamic contribution of such glaciers to sea-level rise (SLR) remains a major challenge because outlet glacier dynamics are poorly understood. Here we present a glacier flow model that includes a fully dynamic treatment of marine termini. We use this model to simulate behaviour of four major marine-terminating outlet glaciers, which collectively drain about 22 per cent of the Greenland Ice Sheet. Using atmospheric and oceanic forcing from a mid-range future warming scenario that predicts warming by 2.8 degrees Celsius by 2100, we project a contribution of 19 to 30 millimetres to SLR from these glaciers by 2200. This contribution is largely (80 per cent) dynamic in origin and is caused by several episodic retreats past overdeepenings in outlet glacier troughs. After initial increases, however, dynamic losses from these four outlets remain relatively constant and contribute to SLR individually at rates of about 0.01 to 0.06 millimetres per year. These rates correspond to ice fluxes that are less than twice those of the late 1990s, well below previous upper bounds. For a more extreme future warming scenario (warming by 4.5 degrees Celsius by 2100), the projected losses increase by more than 50 per cent, producing a cumulative SLR of 29 to 49 millimetres by 2200.

  4. Strong altitudinal control on the response of local glaciers to Holocene climate change in southwest Greenland

    NASA Astrophysics Data System (ADS)

    Larsen, Nicolaj K.; Strunk, Astrid; Levy, Laura B.; Olsen, Jesper; Bjørk, Anders; Lauridsen, Torben L.; Jeppesen, Erik; Davidson, Thomas A.

    2017-07-01

    Accelerating ice loss during recent years has made the Greenland Ice Sheet one of the largest single contributors to global sea level rise, accounting for 0.5 of the total 3.2 mm yr-1. This loss is predicted to continue and will most likely increase in the future as a consequence of global warming. However, the sensitivity of glaciers and ice caps (GICs) in Greenland to prolonged warm periods is less well constrained and geological records documenting the long-term glacial history are needed to put recent observations into a broader perspective. Here we report the results from three proglacial lakes where fluctuations in local glaciers located at different altitudes in Kobbefjord, southwest Greenland have been recorded. Our results show that the lakes received meltwater from the initial deglaciation of the area ∼9.2 cal. ka BP until ∼8.7-7.9 cal. ka BP when the meltwater input ceased as the glaciers most likely disappeared. Regrowth of glaciers began again at ∼5.5 cal. ka BP at ∼1370 m a.s.l., ∼3.6 cal. ka at ∼1170 m a.s.l., and ∼1.6 cal. ka BP at ∼1000 m a.s.l., clearly reflecting strong altitudinal control of the GIC response to Neoglacial cooling. Our results highlight that GICs in Kobbefjord, southwest Greenland are primarily influenced by changes in summer air temperatures and winter precipitation and that they are facing a rapid decay that most likely will result in their disappearance within the next centuries as a consequence of global warming. If current 21st Century retreat rates continue, the GICs in the study area will be completely gone in ∼30-90 years, with the smallest GICs disappearing first.

  5. 110 years of local glacier and ice cap changes in Central- and North East Greenland

    NASA Astrophysics Data System (ADS)

    Bjork, A. A.; Aagaard, S.; Kjaer, K. H.; Khan, S. A.; Box, J.

    2014-12-01

    The local glaciers and ice caps of Greenland are becoming more apparent players in global sea-level rise, and their contribution to future changes is significant. Very little information on their historical fluctuations exists as much of the focus has been on the Greenland Ice Sheet. Now, we can for the first time present historic data that spans 110 years for more than 200 of the local glaciers and ice caps covering this large and important region of the Arctic. The central- and north eastern part of Greenland is of particular interest as these areas are predicted to exhibit a more active behavior with higher mass loss in the future - simultaneously with an increase in precipitation. Our results show that the glaciers and ice caps in the region are responding very rapidly to changes in temperature and precipitation. The present retreat is the fastest observed within the last eight decades, only surpassed by the rapid post LIA retreat. The 1930s was the golden era for scientific exploration in Central- and North East Greenland as several large expeditions visited the area and photographed from land, sea and air. We use historic recordings from Danish and Norwegian aerial missions and terrestrial recordings from the renowned American Explorer Louise Boyd. These unique pictures from the early 1930s form the backbone of the study and are supplemented the more recent aerial photographs the 1940s and onwards and satellite imagery from the mid-1960s and up until present. From high resolution aerial photographs we are able to map the maximum extent of the glaciers during the LIA (Little Ice Age), from which retreat in this area is estimated to commence in 1900. Using a new SMB (Surface Mass Balance) model and its components covering the entire observational period along with high resolution DEMs and historic sea-ice records we are now able to extract valuable information on the past and present triggers of glacial change.

  6. Algal communities in cryoconite holes on the Russell glacier, Southwest Greenland

    NASA Astrophysics Data System (ADS)

    Lamsters, Kristaps; Stivrins, Normunds; Karušs, Jānis; Krievāns, Māris; Rečs, Agnis

    2017-04-01

    The surface of the Greenland Ice Sheet in ablation zone has considerably darkened in the last decades, thus absorbing more solar radiation and accelerating ice melting. Darkening of glacier is made of different impurities that reduce surface albedo. These impurities are represented as cryoconite - combination of dust, soot and microorganisms. While mineral dust composes the greatest part of cryoconite, the black carbon is the most solar radiation absorbing constituent. Microorganisms on the ice are concentrated in cryoconite holes, which have long been of scientific interest, but still remain poorly understood. In order to investigate the microbial communities in cryoconite holes, we collected 12 samples from cryoconite holes at 6 sites located on a 2.5 km long transect line on Russell glacier, Southwest Greenland. The first sampling site was set 3 km from glacier margin at 552 m a.s.l. and the last sampling site was 500 m from the glacier margin at 423 m a.s.l. Depth and diameter of each cryoconite hole, as well as pH, temperature and electrical conductivity was measured in situ on July 29, 2017. During microscopic analysis all microcharcoal (10-100 µm), spheroidal carbonaceous particles (soot), pollen, spores and algae were recorded. Principal Component Analysis reveal two clusters of cryoconite holes (located at 423-465 m a.s.l. and 465-552 m a.s.l.) indicating altitudinal differences. Further, our results show that the biomass of green algae Mesotaeniaceae is correlated with temperature. Meanwhile green algae Chlamydomonadaceae correlates with temperature, microcharcoal and soot particle abundance. Our results show that green algae are dominant type of microorganisms inhabiting cryconite holes on the Russell's glacier at least up to distance of 3 km from ice margin. It is contrary to the previous study of Uetake et al. (2010), who found that cyanobacterial (Oscillatoriaceae) community dominated at 510-635 m altitude of the ablation area of Russell glacier in

  7. Petermann Glacier, North Greenland: Large Ice-Discharge Episodes from 20 Years of Satellite Observations

    NASA Astrophysics Data System (ADS)

    Babiker, M.; Johannessen, O. M.; Miles, M. W.; Miles, V. V.

    2009-12-01

    The major marine-terminating outlet glaciers of Greenland can undergo large mass losses through calving of icebergs and bottom melting from floating ice tongues. Recent observations of outlet glaiers around Greenland have shown that large and rapid changes in solid-ice fluxes are possible. The Petermann glacier in remote northern Greenland is the region’s largest floating-tongue glacier (~70 km by 10 km). In summer 2008 a large calving event was observed, as well as large cracks upstream of the remaining calving front, portending a more massive near-term loss. These observations may herald extraordinary and unprecedented change. However, the long-term variability of calving events and ice velocities are poorly known. Our research goal here is to identify the temporal variability and possible trends in solid-ice flux indicators - variability of the calving front and ice velocity - for Petermann glacier. The methodological approach is observational, based primarily on analysis of 20 years of repetitive satellite data over a period starting from 1990, together with sporadic earlier observations. The multisensor data range from high-resolution optical images from Landsat, SPOT and Terra ASTER and high-resolution synthetic aperture radar (SAR) images from ERS and ENVISAT. These disparate data have been imported, geo-registered and analysed within a Geographic Information System. The following measurements are made: (1) delineating changes in the calving front, (2) estimating the area of glacial ice loss during calving events, and (3) estimating the ice-surface velocity using sequential satellite images. We find evidence of a number of previous calving episodes of similar magnitude to the summer 2008. The ice-velocity estimates compare well with other estimates for particular years, and moreover are relatively consistent during the 20-year period. These findings suggest business-as-usual for Petermann glacier; however, a near-term calving event exceeding those observed

  8. Reconstructing the behaviour of a major SW Greenland tidewater glacier over the last millennium.

    NASA Astrophysics Data System (ADS)

    Pearce, Danni; Mair, Doug W. F.; Rea, Brice R.; Schofield, J. Ed; Lea, James M.; Kamenos, Nick; Schoenrock, Kate; Stachnik, Lukasz

    2016-04-01

    Greenlandic tidewater glaciers have experienced widespread retreat over the last century. However, information on their dynamics prior to this are poorly constrained due to a lack of observations and paucity, in many cases of mapped or mappable deglacial evidence. Especially lacking is evidence for tidewater glacier advance during the Little Ice Age (LIA). This severely restricts our understanding of the long-term (centennial-millennial timescale) relationships between climate and calving at marine terminating margins in Greenland and elsewhere. Kangiata Nunaata Sermia (KNS) is the most dynamic tidewater glacier in southwest Greenland having retreated >22 km since its LIA-maximum (c. 1761). This project takes advantage of the site's unique combination of terrestrial evidence of glacier change (glacial geomorphology, sedimentology, and Norse archaeology) and novel marine evidence (coralline algae) to reconstruct both its advance and retreat over the last millennium. We present glacial geomorphological mapping, which followed a morphstratigraphic approach, using a combination of aerial photos, a DEM and field mapping. Radiocarbon dating from peat sequences were used to determine the timing and rates of advance of KNS to the LIAmax. This has provided evidence for pre-LIA moraines, deglacial and neoglacial, and rapid changes in meltwater routing that may have contributed to the abandonment of nearby Norse settlements. Isotopic analysis of annually banded coralline algae (Lithothamnion glaciale), collected during summer 2015, will provide proxy evidence for changes in fjord water conditions. This data will contribute towards a millennial timescale record of tidewater glacier dynamics that will help to validate models linking calving to climate.

  9. Investigation of Greenland Russell glacier with remote sensing observations and ice sheet/hydrodynamic simulations

    NASA Astrophysics Data System (ADS)

    Yun, Hyewon; Kim, Jungrack; Tsai, YaLun; Lin, ShihYuan; Choi, Yunsoo

    2016-04-01

    There is great interest in the mechanism and consequences of arctic ice sheet migration in the context of worldwide climate change. An in-depth investigation of glacial movement involving supra/under glacial hydrological channel activities is key to understanding the acceleration of Greenland's ice sheet changes and needs to be established as an integrated model. In terms of the glacial migration involving basal hydrology, we have conducted a case study over the Russell glacier in western Greenland. Remote sensed image analyses combined with a numerical model in its melt water outflow channels, such as the Akuliarusiarsuup Kuua and Qinnguata Kuussua rivers, and ice sheet simulations were performed. Employed technical approaches are summarized as follows: 1) Collecting 3D migration vectors combining differential interferometric SAR (D-InSAR) analysis, together with the in-house pixel tracking method employing optical flow and sub-pixel refinement with C band Sentinel-1 and L band ALOS PALSAR-2 images; 2) a 2D hydrodynamic simulation based on the channel bathymetry, which was driven from calibrated LANDSAT images together with along-track stereo DTM, and 3) an ice sheet model to extract the bedrock and basal characteristics of the glaciers. In addition, we tried Sentinel-1 InSAR time series to monitor ice sheet migrations over a certain time domain. The results revealed the importance of hydrological channel morphology as a governing factor over migration speeds of glaciers. Specifically, the sub glacial processes and underlying morphology traced by remote sensing observation and the numerical model were correlated with the observed local migration speeds in terminus of the Russell glacier. Those experiences naturally will lead to a more comprehensive understanding of the processes of artic glaciers. Thus, based on the output of this study, the proposed method will be extended to tackle the issues of ice sheet change occurring in the Greenland costal area

  10. Tide-modulated seismicity in the vicinity of a calving front (Bowdoin Glacier, Greenland)

    NASA Astrophysics Data System (ADS)

    Podolskiy, Evgeny A.; Sugiyama, Shin; Funk, Martin; Walter, Fabian; Genco, Riccardo; Tsutaki, Shun; Minowa, Masahiro; Ripepe, Maurizio

    2016-04-01

    For cryogenic microseismicity to be used as an indicator of climate-induced dynamic change, it must have a clear connection with glacier dynamics (including calving, basal sliding, strain, and melt). There is currently much speculation and disagreement about these connections, particularly, with respect to the relationship between tide-modulated seismicity and dynamics of calving glaciers. Here we analyze records from an on-ice seismometer placed 250 m from the calving front of Bowdoin Glacier, northwestern Greenland. We find that the overall microseismic activity of this glacier is at least an order of magnitude larger than previously reported (more than 100,000 events within 2 weeks and up to 600 events per hour) and that it is positively correlated with falling tide velocity. Using high-resolution surface displacement measurements, we show for the first time that the correlation is relayed through strain-rate variations. The strain-rate corresponds with longitudinal stretching of the glacial surface, in response to higher melt rates and falling tide, both of which accelerate glacier movement and enhance the stretching flow regime. Previous proposals to use icequakes as a proxy for grounding line migration need to be reconsidered because Bowdoin Glacier is grounded, with no tide-induced vertical bending of the near-floating tongue, which always exhibits microseismic activity due to continuous longitudinal stretching.

  11. Marine algae inform past calving rates of a tide water glacier in western Greenland.

    NASA Astrophysics Data System (ADS)

    Schoenrock, Kathryn; Kamenos, Nicholas; Mair, Douglas; Lea, James; Rea, Brice; Schofield, James; Pearce, Danni

    2017-04-01

    Coralline algae are ubiquitous in marine environments worldwide acting as ecosystem engineers by cementing reefs together and providing habitat for local communities. The calcified thallus also makes coralline algae repository for past environmental conditions, providing information on the scale of 10s-100s of years. Free living coralline algae, or maerl, can dominate local habitats along the coasts and in fjord systems of western Greenland. Using the long lived maerl species, Lithothamnion glaciale, we present multi-proxy data sets for the large fjord system adjacent to the Kangiata Nunâta Sermia (KNS) glacier. This information provides a record of glacial movement (advance and retreat) and calving for the past 70+ years which can be correlated to records of glacial calving. The KNS glacier is one of the largest tidewater glaciers in western Greenland and contributes to the mass transfer of glaciers and ice sheets into the world oceans. The present data combined with terrestrial proxies within the CALVE research project will help inform policy and models focusing on future climate conditions.

  12. Marine algae inform past calving rates of a tide water glacier in western Greenland.

    NASA Astrophysics Data System (ADS)

    Schoenrock, K. M.; Kamenos, N.; Pearce, D.; Schofield, J.; Rea, B. R.; Lea, J.; Mair, D.

    2016-02-01

    Coralline algae are ubiquitous in marine environments worldwide. They are ecosystem engineers, cementing reefs together and providing habitat for local communities with the 3D structure of their calcified thallus material. The calcified thallus make corallines a resource of environmental data as well, providing information on the scale of 10s-100s of years. Free living coralline algae, or maerl, dominate local habitats along the coasts and in fjord systems of western Greenland. Using the long lived maerl species, Lithothamnion glaciale, we present multi-proxy data sets for the large fjord system adjacent to the Kangiata Nunta Sermia (KNS) glacier. This information provides a record of glacial movement (advance and retreat) and calving from the Medieval Warm Period through the Little Ice Age to the present day. The KNS glacier is one of the largest tidewater glaciers in western Greenland and contributes to the mass transfer of glaciers and ice sheets into the world oceans. The present data combined with terrestrial proxies will help inform policy and models focusing on future climate conditions.

  13. Using reflection seismics to identify and monitor the basal conditions of Russell Glacier South West Greenland.

    NASA Astrophysics Data System (ADS)

    Hofstede, Coen; Kleiner, Thomas; Bondzio, Johannes; Eisen, Olaf; Wilhelms, Frank; Bohleber, Pascal; Fritzsche, Diedrich; Hubbard, Alun

    2015-04-01

    Russell Glacier is a land terminating glacier in South West Greenland. Survey site SHR lies at several kilometers from the terminus and is closely monitored. In recent years in Summer months, site SHR has seen unusual high ice velocities of up to 400m/a which have been linked to increased Summer melt. To capture the probably changing basal conditions of Russell Glacier at SHR we carried out two seismic surveys at site SHR, one in September 2013 at the end of the melt season and one in May 2014 at the start of the melt season. The seismic data were recorded using a 300m snow streamer and explosives. The data reveal an ice thickness of about 550m and 30 to 40m thick accreted subglacial sediments with varying degrees of water saturation in both ice and sediment. We speculate the increased ice velocity is caused by sediments that become temporarily liquefied in the Summer months.

  14. 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.

  15. Migration model establishment over Greenland Russell glacier with Remote Sensing observations and hydrodynamic simulations

    NASA Astrophysics Data System (ADS)

    Yun, H.; Kim, J.; Lin, S. Y.; Tsai, Y.; Choi, Y.

    2015-12-01

    The mechanism of arctic ice sheet migration is not yet fully identified. Glacial movement, specifically that involving supra/under glacial hydrological channel activities, may hold the key for understanding the acceleration of Greenland's ice sheet change and needs to be investigated in depth and established as an integrated model. The test area on which the above studies were conducted was in the Russell glacier in western Greenland, where glacial change has been obvious for the last century and significant fluvial flows occur in meltwater outflow channels, such as the Akuliarusiarsuup Kuua and Qinnguata Kuussua rivers. All tasks in the study were conducted in three stages: 1) collecting 3D migration vectors combining C and L band differential interferometric SAR (D-InSAR) analysis, together with the in-house pixel tracking method employing optical flow and sub-pixel refinement; 2) a 2D hydrodynamic simulation based on the channel bathymetry, which was driven from calibrated LANDSAT images together with along-track stereo DTM; and 3) the model inversion to extract the bedrock height and the physical processes under the glaciers. Throughout those approaches, the researchers intended to identify firstly the interconnected processes between subglacier melt water flow and glacial migration, and also the model establishments of the involved processes. Consequently, the study revealed highly important clues about glacial migration. First of all, the importance of hydrological channel morphology as a governing factor over glaciers' outflowed total melt water was identified. Also, it became clear that the reconstruction of sub glacial processes and morphology are feasible by employing remote sensing observations and model inversions. Those experiences will naturally lead to a more comprehensive understanding of the processes on the terminus of glacier. The overall results from these approaches were compared and validated against published bedrock heights and ice

  16. Estimating ice-melange properties with repeat UAV surveys over Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Toberg, Nick; Ryan, Johnny; Christoffersen, Poul; Snooke, Neal; Todd, Joe; Hubbard, Alun

    2016-04-01

    In the past decade, tidewater outlet glaciers of the Greenland ice sheet (GrIS) have thinned and retreated when compared to the 1980s when the ice sheet was in a state of dynamic balance. With a growing amount of ice discharged into the sea by tidewater glaciers as well as more ice melting on the surface, the Greenland Ice Sheet has become the single largest cryospheric source of global sea level rise. Today, the ice sheet causes sea level rise of 1 mm per year, highlighting the need to understand the ice sheet's response to climate change. Atmospheric warming will inevitably continue to increase surface meltwater production, but the dynamic response, which includes hundreds of fast-flowing tidewater glaciers, is largely unknown. To develop new understanding of ice sheet dynamics, we investigated the mechanism whereby icebergs break off tidewater glaciers and form a proglacial ice melange. This melange is rigid in winter when sea ice and friction along the sidewalls of the fjord, or even at the sea floor, hold it together. The result is a resistive force, which reduces the rate of iceberg calving when the ice melange is rigid and is lost when the melange disappears in the summer. From early May to late July 2014, we launched unmanned aerial vehicles (UAVs) from a basecamp on a bluff overlooking the calving front of Store Glacier, a 5 km wide tidewater glacier flowing into Uummannaq Fjord in West Greenland. The Skywalker X8 UAVs had a wing-span of 2.1m and a payload containing a high resolution camera, an autopilot system and a GPS data logger. We generated almost 70,000 georeferenced images during 63 sorties over the glacier during a 10 week field season starting 13 May 2014. The images were used to construct orhorectified mosaics and digital elevation models of the proglacial melange with Photoscan structure-from-motion software. The imagery and the DEMs were analysed statistically to understand the spatial characteristics of the ice melange. By combining the

  17. Arctic Coastal Fog over Greenland Glaciers using an Improved MODIS Fog Detection Method and Ground Observations

    NASA Astrophysics Data System (ADS)

    Jiskoot, H.; Harvey, T.; Gilson, G.

    2015-12-01

    Annual breakup of sea ice causes fog in Arctic coastal regions, which can both reduce and enhance glacier melt. With progressive sea ice loss and increasing temperatures and atmospheric moisture in the Arctic, it is essential to determine the frequency and spatial extent of fog in order to understand its present and future effects on glacier mass balance. Previously, we determined Greenland coastal fog to peak with 15-25% of days in July. Here, we present the spatial and vertical extent of significant melt-season fog events over Greenland coastal glaciers and the ice sheet. To this end, we modified a MODIS fog/low stratus detection method by Bendix et al. (2005), with verification by weather and radiosonde data, timelapse and Landsat imagery, and independent fog classifications. Our fog-detection method uses MODIS Levels 1b and 2, processed in an ENVI-ArcGIS environment as follows: 1) visual examination and application of vegetation and snow indices; 2) initial fog/low stratus discrimination with novel band thresholds and cloud products; 3) verification using cloud phase/temperature products; 4) cleaning misclassified pixels; 5) calculating fog/low stratus optical and geometrical thickness; 6) final differentiation of fog from low stratus using edge-pixel detection, trend-surface fitting, and DEM filling. The end product consists of 500 m fog-mask pixel maps over Greenland, with minimum and maximum possible extents based on classification of fog versus low stratus. Our results show that fog can cover extensive areas of the Greenland ice masses. Persistent fog events in early, mid, and late melt-season were extracted for East Greenland using fog rim detection overlain on the GIMP DEM, the Randolph Glacier Inventory, and a coast shapefile. E.g., a 4 July 2002 fog event covers 4300-5000 km2 of ice, with a maximum inland extent of 85 km to an elevation of 1250 m asl. Fog thickness over ice is 20-800 m, but can be underestimated by >50 m compared to radiosonde data.

  18. High basal melt rates observed on Store Glacier, West Greenland, using phase-sensitive FMCW radar

    NASA Astrophysics Data System (ADS)

    Young, T. J.; Christoffersen, P.; Nicholls, K. W.; Lok, L. B.; Doyle, S. H.; Hubbard, B. P.; Stewart, C.; Hofstede, C. M.; Bougamont, M. H.; Todd, J.; Brennan, P. V.; Hubbard, A.

    2016-12-01

    The Greenland ice sheet is losing mass, and is currently contributing 1 mm/year to global sea level rise. The large majority of these changes can be attributed to the recent acceleration in flow of marine-terminating outlet glaciers within the last several decades. Such fast ice flow is characterised by ice deformation, as well as basal motion. However, there are few direct observations of either of these contributing mechanisms due to the difficulty of accessing the subglacial environment. In particular, although basal melt rates have been measured on ice shelves for decades, there exist almost no equivalent observations for grounded ice sheets. We present the first time series of directly-measured rates of basal melting at the bed of Store Glacier, a major outlet glacier flowing into Uummannaq Fjord in West Greenland. The measurements were obtained using a phase-sensitive, frequency modulated continuous wave (FMCW) radar system installed 30 km upflow of the calving terminus at a location where the surface velocity of the glacier is 700 m/year. Radar data were recorded every 4 hours from 26 July to 11 December 2014. The same site was used to instrument 610-m-deep boreholes drilled to the bed as part of the Subglacial Access and Fast Ice research Experiment (SAFIRE). With internal and basal reflector ranges captured at high spatial (millimetre) and temporal (hourly) resolutions, we obtained a unique, 6-month-long time series of ice deformation and basal melting coincident with englacial and subglacial borehole measurements. Here, we report sustained basal melting of 3 m/year during winter, and maxima of 20 m/year during summer when basal motion is enhanced by surface water delivered to the bed. The lower, but more constant rate of winter basal melting is likely to be driven by frictional heat generated from basal sliding. These discoveries indicate that basal melting beneath Greenland's fast flowing outlet glaciers is considerably higher than basal melting reported

  19. Variability of subglacial discharge recorded with thermal infrared timelapse of a tidewater glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Byers, L. C.; Stearns, L. A.; Brunsell, N. A.; Catania, G. A.; Fried, M.; Bartholomaus, T.; Felikson, D.; Sutherland, D.; Carroll, D.; Shroyer, E.; Nash, J. D.; Walker, R. T.; Finnegan, D. C.; LeWinter, A.

    2015-12-01

    Subglacial hydrology and the dynamics therein are important modulators of ice flow in the Greenland Ice Sheet. At tidewater outlet glaciers the characteristics of proglacial discharge affect fjord circulation, sediment deposition, submarine melt rates, and iceberg calving. Information about the spatio-temporal variability of discharge is limited by the challenges of in situ data collection at tidewater glaciers. Here, we present summertime measurements of subglacial discharge variability using a thermal infrared (7.5μm to 13μm) camera and intervalometer at Kangerlussuup Sermia (KS), a ~4km wide outlet glacier in the Uummannaq Bay region of West Greenland (71.46 N, 51.43 W). KS has an advantageous geometry for this investigation because of its shallow grounding zone and well-entrenched subglacial hydrologic system. In tandem, these characteristics promote buoyant freshwater to rise to the fjord surface from discrete outlets at the glacier's base. We investigate the timing of plume activity at these outlets and discuss potential controls on outlet switching. Raw camera measurements cannot be accurately converted to surface temperature without correcting for environmental variables and scene geometry, both of which are time-evolving during data acquisition. Our processing methodology relies on a variety of existing techniques -- image segmentation, ray casting, atmospheric radiative transfer modeling, Monte Carlo simulations -- and a variety of ancillary data products -- satellite imagery, atmospheric reanalysis, meteorologic and hydrologic measurements -- to produce the final results. What is gained is an unprecedented view into interactions between the cryosphere, hydrosphere, and atmosphere that control the dynamic and sensitive terminus region of a tidewater outlet glacier.

  20. On the response of northwest Greenland glaciers to ocean thermal forcing

    NASA Astrophysics Data System (ADS)

    Wood, M.; Rignot, E. J.; Menemenlis, D.; Fenty, I. G.; Millan, R.; van den Broeke, M. R.

    2016-12-01

    Over the past 25 years, the tidewater glaciers of northwest Greenland have exhibited widespread retreat synchronous with warming ocean temperatures in northeast Baffin Bay, yet we also observe different behaviors from one glacier to the next, sometimes within the same fjord. Here, we calculate the ocean-induced melt rate of glaciers in the northwest using simulations from the MITgcm ocean model for various water depths, ocean thermal forcing (TF) and subglacial water fluxes (SG). We use water depth from Ocean Melting Greenland (OMG) bathymetry, ocean thermal forcing from the Estimating the Circulation and Climate of the Ocean (Phase II, ECCO2) combined with CTD data from 2012 and 2015, and time series of subglacial water flux combining runoff production from the 1-km Regional Atmospheric Climate Model (RACMO2.3) with basal melt beneath land ice from the JPL/UCI ISSM model. Time series of melt rates are formed as a function of grounding line depth, SG flux and TF. We compare the results with the calving speed of the glaciers and history of retreat rate to assess the relative glacier control between calving rate and ice melt by the ocean over the past two and a half decades. In some cases, we find that the front position is highly modulated by ocean-induced melt. For example, the melt rates at Docker Smith Gletscher and the southern-most branch of Hayes Gletscher (Hayes SS) have been comparable to or have exceeded the frontal speeds since the late 1990's, which coincides with their 5-km and 2-km retreats, respectively, despite moving into water 100 m shallower than at the start of the retreat. In other, often adjacently positioned, cases such as Gade Gletscher or another sub-branch of Hayes Gletscher (Hayes M), the frontal speeds far exceeded ocean-induced melt rates, the glaciers are dominantly controlled by calving processes, and the glacier retreat has been minimal (<300m) in the past two decades. These results illustrate the sensitivity of northwestern glaciers

  1. Petermann Glacier, North Greenland: massive calving in 2010 and the past half century

    NASA Astrophysics Data System (ADS)

    Johannessen, O. M.; Babiker, M.; Miles, M. W.

    2011-01-01

    Greenland's marine-terminating glaciers drain large amounts of solid ice through calving of icebergs, as well as melting of floating glacial ice. Petermann Glacier, North Greenland, has the Northern Hemisphere's long floating ice shelf. A massive (~270 km2) calving event was observed from satellite sensors in August 2010. In order to understand this in perspective, here we perform a comprehensive retrospective data analysis of Petermann Glacier calving-front variability spanning half a century. Here we establish that there have been at least four massive (100+ km2) calving events over the past 50 years: (1) 1959-1961 (~153 km2), (2) 1991 (~168 km2), (3) 2001 (~71 km2) and (4) 2010 (~270 km2), as well as ~31 km2 calved in 2008. The terminus position in 2010 has retreated ~15 km beyond the envelope of previous observations. Whether the massive calving in 2010 represents natural episodic variability or a response to global and/or ocean warming in the fjord remains speculative, although this event supports the contention that the ice shelf recently has become vulnerable due to extensive fracturing and channelized basal melting.

  2. An empirical approach for estimating stress-coupling lengths for marine-terminating glaciers

    USGS Publications Warehouse

    Enderlin, Ellyn; Hamilton, Gordon S.; O'Neel, Shad; Bartholomaus, Timothy C.; Morlighem, Mathieu; Holt, John W.

    2016-01-01

    Here we present a new empirical method to estimate the SCL for marine-terminating glaciers using high-resolution observations. We use the empirically-determined periodicity in resistive stress oscillations as a proxy for the SCL. Application of our empirical method to two well-studied tidewater glaciers (Helheim Glacier, SE Greenland, and Columbia Glacier, Alaska, USA) demonstrates that SCL estimates obtained using this approach are consistent with theory (i.e., can be parameterized as a function of the ice thickness) and with prior, independent SCL estimates. In order to accurately resolve stress variations, we suggest that similar empirical stress-coupling parameterizations be employed in future analyses of glacier dynamics.

  3. Relationships between fjord bathymetries and recent glacier behavior: gaining new insight from IceBridge flights over Greenland

    NASA Astrophysics Data System (ADS)

    Porter, D.; Boghosian, A.; Tinto, K. J.; Cochran, J. R.; Bell, R. E.

    2012-12-01

    The geometry of glacial fjords may play a large role in determining the stability of outlet glaciers. Sloping seafloors will feedback on a moving grounding line and shallow sills and deep continental shelf troughs will allow greater interaction with the surrounding ocean water. To better understand the role of fjord bathymetry in the glacier system, Operation IceBridge (OIB) has flown a suite of radar, lidar, gravity and magnetic instruments along the flow lines of previously inaccessible outlet glaciers and their fjords around the Greenlandic coast. Here, we combine newly collected surface elevation, ice thickness data, and gravity and magnetic anomalies from OIB flights, along with ship-based bathymetric profiles, into a single dataset. The combination of these new data are used in the construction of forward models that provide the framework for performing gravity inversions, finally resulting in many new bathymetric charts of previously unmapped fjords in Greenland. These newly created fjord bathymetries are compared to several important characteristics their outlet glaciers and ocean waters. We investigate the importance of glacier parameters such as surface velocity and area changes, as well as newly available oceanographic data from within the fjord, on recent changes in glacier behavior. Are faster flowing glaciers found in fjords with deep sills and a greater exchange with continental shelf water? Comparisons of these glacier-fjord relationships are also separated by region and by glacier type. Are glaciers in the southeast mostly changing in a similar way even though their bed geometries are quite different? These broad correlations are a starting point in an effort to investigate the role of bed geometry in the relationship between external forcing and the observed recent change of many of Greenland's largest outlet glaciers.

  4. Has dynamic thinning switched off in south-east Greenland?

    NASA Astrophysics Data System (ADS)

    Murray, T.; Scharrer, K.; James, T. D.; Dye, S. R.; Hanna, E.; Booth, A. D.; Selmes, N.; Luckman, A.; Hughes, A. L. C.; Huybrechts, P.

    2009-04-01

    Following a relatively stable period during the 1990's, dramatic changes have been reported for many tidewater outlets in the south-eastern part of the Greenland Ice Sheet (GrIS). Results from measurements using the GRACE (Gravity Recovery and Climate Experiment) mission clearly identified the south-eastern part of the GrIS as having the highest rates of mass loss (1, 2). Two of the major outlet glaciers in this area, Helheim and Kangerdlugssuaq, accelerated by about 100 percent and 40 percent, respectively, and their calving fronts retreated by several km (3). Retreat and acceleration occurred in two phases during summer 2003 and 2005 at Helheim, and in a single period between late 2004 and early 2005 at Kangerdlugssuaq. Further south widespread glacier acceleration between 1996 and 2005 affected most of the outlet glaciers (4). In all Greenland's mass loss was calculated to have doubled in the period (4). Increased discharge due to thinning in the marginal areas, coupled to rapid changes in ice dynamics and synchronous retreat of their calving front positions, led to speculations that the GrIS had crossed a "tipping point" induced by global warming. However, subsequent studies showed that during summer 2006 Helheim and Kangerlugssuaq had simultaneously slowed down and their thinning had stopped. Because variability in the ice sheet's mass loss results mostly from the SE Greenland sector, further understanding of the nature, distribution, and controls of dynamic change in this region is essential. In order to examine the extent of the dynamic changes and to identify their cause we used satellite data to measure glacier surface elevation and calving front positions of 24 outlets of 14 major tidewater terminating glaciers, as well as speeds of 9 outlets in SE Greenland. We concentrate on the region where the GRACE data show highest rates of mass change and our data cover the period during and after the cessation of fast flow and thinning at Helheim and

  5. Warming Beneath the 79⁰N Glacier in Northeast Greenland and Warm Atlantic Water in Fram Strait

    NASA Astrophysics Data System (ADS)

    Dodd, Paul; Schaffer, Janin; von Appen, Wilken-Jon; de Steur, Laura; Kanzow, Torsten

    2016-04-01

    Time series measurements of temperature beneath the 79°N glacier, over the East Greenland Continental Shelf and in Fram Strait suggest that recently observed warming beneath the glacier may be caused by warm recirculating Atlantic water from Fram Strait. CTD profiles close to the 79°N glacier collected between 1997 and 2015 (5 cruises) are compared with CTD profiles over the East Greenland Shelf collected between 1980 and 2015 (15 cruises) and with repeated transects across Fram Strait between 1983 and 2015 (24 cruises). The 2009 and 2014 cruises exploited a rift in the 79°N glacier to access the cavity below without the need for drilling. The time series of observations shows that the temperature of water in the cavity beneath the 79°N glacier is rising. This warm water likely reaches the cavity via the Norske-Westwind trough on the East Greenland Shelf. The temperature of water in the southern part of this trough responded quickly to the temperature of water in Fram Strait, showing a distinct peak in 2006-8. The northern part of the trough responded less strongly, probably because it is upstream of the region where the bulk of the Atlantic Water recirculates in Fram Strait. Subsurface warm water at the northern end of the trough also had a colder signature suggesting it originates from Atlantic Water that has recirculated further into the central Arctic. We are concerned that the trough system on the East Greenland Shelf provides a short-circuit allowing heat transported from low latitudes by northward flowing Atlantic water to directly affect the Greenland Ice Sheet. If our assumptions are correct, the rising temperature of water in the Norwegian Atlantic Current potentially threatens the 79°N glacier, which drains a major part of the Northeast Greenland Ice Sheet.

  6. Annual glacier dammed lake drainage in Zackenberg, Northeast Greenland

    NASA Astrophysics Data System (ADS)

    Lane, Timothy; Adamson, Kathryn; Matthews, Tom

    2016-04-01

    A.P. Olsen is a 295 km2 ice cap in the Zackenberg region of Northeast Greenland (74.6° N, 21.5° W), 35 km from the ZERO Zackenberg Research Station. The ice cap lies on a gneissic plateau, covering an elevation of 200 to 1450 m a.s.l. A.P. Olsen mass balance has been monitored since 2008 and reconstructed for the period 1995-2007. Meltwater from this ice cap drains into the Zackenberg River, and into Young Sund via the Zackenberg Delta. One outlet dams a c. 0.8 km2 lake fed by the northern part of the ice cap. Observational data suggests this lake drains annually, flooding subglacially into the Zackenberg River. But the impacts of these flood events on the hydrology, sediment transfer, and geomorphology of the proglacial zone downstream have not been examined in detail. Understanding the impacts of glacial lake outburst flood events is important in the sensitive Arctic environment, where glacial change is rapid. We use Landsat scenes to reconstruct lake extent from 1999-2015. This is compared to Zackenberg River discharge measurements, available from the ZERO Zackenberg monitoring programme. These datasets are used to examine the nature and timing of flood events, and assess the impacts on the Zackenberg river downstream.

  7. Oxygen isotope ratios in the shell of Mytilus edulis: archives of glacier meltwater in Greenland?

    NASA Astrophysics Data System (ADS)

    Versteegh, E. A. A.; Blicher, M. E.; Mortensen, J.; Rysgaard, S.; Als, T. D.; Wanamaker, A. D., Jr.

    2012-09-01

    Melting of the Greenland Ice Sheet (GrIS) is accelerating and will contribute significantly to global sea level rise during the 21st century. Instrumental data on GrIS melting only cover the last few decades, and proxy data extending our knowledge into the past are vital for validating models predicting the influence of ongoing climate change. We investigated a potential meltwater proxy in Godthåbsfjord (West Greenland), where glacier meltwater causes seasonal excursions with lower oxygen isotope water (δ18Ow) values and salinity. The blue mussel (Mytilus edulis) potentially records these variations, because it precipitates its shell calcite in oxygen isotopic equilibrium with ambient seawater. As M. edulis shells are known to occur in raised shorelines and kitchen middens from previous Holocene warm periods, this species may be ideal in reconstructing past meltwater dynamics. We investigate its potential as a palaeo-meltwater proxy. First, we confirmed that M. edulis shell calcite oxygen isotope (δ18Oc) values are in equilibrium with ambient water and generally reflect meltwater conditions. Subsequently we investigated if this species recorded the full range of δ18Ow values occurring during the years 2007 to 2010. Results show that δ18Ow values were not recorded at very low salinities (< ~19), because the mussels appear to cease growing. This implies that M. edulis δ18Oc values are suitable in reconstructing past meltwater amounts in most cases, but care has to be taken that shells are collected not too close to a glacier, but rather in the mid region or mouth of the fjord. The focus of future research will expand on the geographical and temporal range of the shell measurements by sampling mussels in other fjords in Greenland along a south-north gradient, and by sampling shells from raised shorelines and kitchen middens from prehistoric settlements in Greenland.

  8. Oxygen isotope ratios in the shell of Mytilus edulis: archives of glacier meltwater in Greenland?

    NASA Astrophysics Data System (ADS)

    Versteegh, E. A. A.; Blicher, M. E.; Mortensen, J.; Rysgaard, S.; Als, T. D.; Wanamaker, A. D., Jr.

    2012-12-01

    Melting of the Greenland Ice Sheet (GrIS) is accelerating and will contribute significantly to global sea level rise during the 21st century. Instrumental data on GrIS melting only cover the last few decades, and proxy data extending our knowledge into the past are vital for validating models predicting the influence of ongoing climate change. We investigated a potential meltwater proxy in Godthåbsfjord (West Greenland), where glacier meltwater causes seasonal excursions with lower oxygen isotope water (δ18Ow) values and salinity. The blue mussel (Mytilus edulis) potentially records these variations, because it precipitates its shell calcite in oxygen isotopic equilibrium with ambient seawater. As M. edulis shells are known to occur in raised shorelines and archaeological shell middens from previous Holocene warm periods, this species may be ideal in reconstructing past meltwater dynamics. We investigate its potential as a palaeo-meltwater proxy. First, we confirmed that M. edulis shell calcite oxygen isotope (δ18Oc) values are in equilibrium with ambient water and generally reflect meltwater conditions. Subsequently we investigated if this species recorded the full range of δ18Ow values occurring during the years 2007 to 2010. Results show that δ18Ow values were not recorded at very low salinities (< ~ 19), because the mussels appear to cease growing. This implies that Mytilus edulis δ18Oc values are suitable in reconstructing past meltwater amounts in most cases, but care has to be taken that shells are collected not too close to a glacier, but rather in the mid-region or mouth of the fjord. The focus of future research will expand on the geographical and temporal range of the shell measurements by sampling mussels in other fjords in Greenland along a south-north gradient, and by sampling shells from raised shorelines and archaeological shell middens from prehistoric settlements in Greenland.

  9. Impact of fine debris on ice melt rates at Russell Glacier, central-west Greenland

    NASA Astrophysics Data System (ADS)

    Carr, Rachel; Linighan, James; Cumming, Alex M. J.

    2017-04-01

    Losses from the Greenland Ice Sheet (GrIS) have increased sharply in recent years, due to accelerated glacier discharge and increased surface melting. In 2012, 99% of the Greenland ice sheet experienced melt, which was exceptional on centennial timescales, but is expected to occur frequently in the future, as climate warms. Ice albedo is a primary control on melt rates and remotely sensed data shows that the GrIS has darkened substantial in recent decades, due to both inorganic and biological material. This has been particularly marked in south- and central-west Greenland and can lead to the development of positive feedbacks. Consequently, it is important to understand the relationship between melt and surface albedo on the GrIS. Here we use a combination of satellite remote sensing and field data to assess the impact of fine debris on melt rates at Russell Glacier, central-west Greenland. Our field data demonstrate that areas with a greater percentage coverage of fine, largely inorganic debris experienced higher melt rates than in areas with a sparse coverage. However, the relationship between melt and debris cover was highly spatially variable. Furthermore, the debris cover evolved substantially over time and we saw marked changes over a period of a few days. Using ASTER imagery, we show that the spatial extent of debris has expanded markedly in this section of the GrIS during the last decade, which could substantially accelerate melting. However, the complex and variable relationship between debris cover and melt rates highlights the need for further research, in order to accurately forecast its impact on GrIS melt rates.

  10. 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.

  11. Identifying potential seasonal and historical drivers of marine-terminating glacier retreat in Disko and Uummannaq Bays, West Greenland

    NASA Astrophysics Data System (ADS)

    York, A.; Frey, K. E.; Das, S. B.

    2015-12-01

    The variability in outlet glacier termini positions is an important indicator of overall glacier health and the net effects of ice-ocean-atmosphere interactions. Glacier margins fluctuate on both seasonal and interannual time scales and satellite imagery provides a critical spatially- and temporally-extensive resource for monitoring glacier behavior. Outlet glaciers have generally been retreating globally over recent decades, but the magnitude of seasonal variation, overall retreat, and foremost drivers have proven unique to each glacier. The outlet glaciers in central West Greenland are generally experiencing the same regional atmospheric forcing, yet previous studies have shown varying magnitudes of retreat over the last forty years. In this study, we utilize Landsat imagery between the years 1985 and 2014 to digitize a time series of glacier front positions of 18 marine-terminating outlet glaciers in the Disko and Uummannaq Bay regions of West Greenland. We examine potential drivers of trends in outlet glacier retreat through satellite observations of adjacent sea ice concentrations and sea surface temperatures. Additionally, reanalysis data and long-term automatic weather station measurements are investigated to contextualize the role of atmospheric drivers at both a regional and local scale. Results indicate retreat of all glaciers in the region over the study period and no indication of a south to north trend in magnitude of retreat on either a seasonal or long-term scale. The 11 glaciers in Uummannaq Bay retreated between 25 m and 3.5 km, an average of 1.22 ± 1.20 km over the entire study period. The retreat of 7 glaciers in Disko Bay ranged from 181 m to 2.3 km, an average of 1.0 ± 0.78 km over the period. Although the mean terminus retreat rate between the two bays is comparable, there remains a wide range of total retreat amounts among the glaciers. We investigate the degree of seasonal variation in terminus position as an indicator of longer

  12. Community interactive webtool to retrieve Greenland glacier data for 1-D geometry

    NASA Astrophysics Data System (ADS)

    Perrette, Mahé

    2015-04-01

    Marine-terminating, outlet glaciers are challenging to include in conventional Greenland-wide ice sheet models because of the large variation in scale between model grid size (typically 10 km) and outlet glacier width (typically 1-5km), making it a subgrid scale feature. A possible approach to tackle this problem is to use one-dimensional flowline models for the individual glaciers (e.g. Nick et al., 2013, Nature; Enderlin et al 2013a,b, The Cryosphere). Here we present a python- and javascript- based webtool to prepare data required to feed in or validate a flowline model. It is designed primarily to outline the glacier geometry and returns relevant data averaged over cross-sections. The tool currently allows to: visualize 2-D ice sheet data (zoom/pan), quickly switch between datasets (e.g. ice thickness, bedrock elevation, surface velocity) interpolated / transformed on a common grid. draw flowlines from user-input seeds on the map, calculated from a vector field of surface velocity, as an helpful guide for point 3 interactively draw glacier outline (side and middle lines) on top of the data mesh the outlined glacier domain in the horizontal plane extract relevant data into a 1-D longitudinal profile download the result as a netCDF file The project is hosted on github to encourage collaboration, under the open-source MIT Licence. The server-side is written in python (open-source) using the web-framework flask, and the client-side (javascript) makes use of the d3 library for interactive figures. For now it only works locally in a web browser (start server: "python runserver.py"). Data need to be downloaded separately from the original sources. See the README file in the project for information how to use it. Github projects: https://github.com/perrette/webglacier1d (main) https://github.com/perrette/dimarray (dependency)

  13. Rerouting of subglacial water flow between neighboring glaciers in West Greenland

    NASA Astrophysics Data System (ADS)

    Chu, Winnie; Creyts, Timothy T.; Bell, Robin E.

    2016-05-01

    Investigations of the Greenland ice sheet's subglacial hydrological system show that the connectivity of different regions of the system influences how the glacier velocity responds to variations in surface melting. Here we examine whether subglacial water flow paths can be rerouted beneath three outlet glaciers in the ablation zone of western Greenland. We use Lamont-Doherty and Center for Remote Sensing of Ice Sheets of University of Kansas (CReSIS) ice-penetrating radar data to create a new ice thickness map. We then use a simple subglacial water flow model to examine whether flow paths can be rerouted and identify the topographic conditions that are sensitive to subglacial rerouting. By varying water pressures within an observationally constrained range, we show that moderate changes in pressure can cause flow paths to reroute and exchange water from one subglacial catchment to another. Flow across subglacial overdeepenings is particularly sensitive to rerouting. These areas have low hydraulic gradients driving flow, so subtle water pressure variations have a strong influence on water flow direction. Based on correlations between water flow paths and ice velocity changes, we infer that water piracy between neighboring catchments can result in a different spatial pattern of hydrologically induced ice velocity speedup depending on the amount and timing of surface melt. The potential for subglacial water to reroute across different catchments suggests that multiple hydrographs from neighboring glaciers are likely necessary to accurately ascertain melt budgets from proglacial point measurements. The relationship between surface runoff, ice dynamics, and proglacial discharge can be altered by rerouting of subglacial water flow within and across outlet glaciers.

  14. Partitioning of Submarine Melt and Calving across the front of Store Glacier, Greenland

    NASA Astrophysics Data System (ADS)

    Hubbard, A., II; Chauche, N.

    2015-12-01

    Processes unique to the marine-termini of fast-flowing tidewater outlet glaciers can potentially drive extreme rates of mass wastage thereby providing a rapid link between the terrestrial ice reservoir and the oceanic sink. Here we attempt to directly quantify the pattern and magnitude of calving and melt at the front of Store Glacier, a major outlet draining the western sector of the Greenland ice sheet. Integration of range-survey technologies on a robust, heavy displacement marine platform coupled with high-resolution photogrammetry allowed the production of accurate, ~m resolution 3d digital terrain models (DTMs) of the glacier front. A swath-interferometric sonar system calibrated via an inertial motion unit stabilized with RTK GPS and vector-compass data-streams was combined with photogrammetric processing of repeat UAV surveys. The results of three repeat surveys across the front of Store Glaciers in 2012 is presented during which significant ice flow, melt and calving events were imaged, complimented with AWS, on-ice GPS stations and time-lapse/video camera sequences. The residual of successive DTMs yield the 3d pattern of frontal change allowing the processes calving and melt to be quantified and constrained in unprecedented detail. The pattern of submarine melt is further validated against indirect estimates of submarine melt derived from oceanographic circulation measurements within the fjord.

  15. Modeling Subglacial Meltwater Plumes across Greenland's Outlet Glaciers: Implications for Ice-Ocean Coupling in a Warming Climate

    NASA Astrophysics Data System (ADS)

    Carroll, D.; Sutherland, D.; Moon, T. A.; Hudson, B.; Noel, B.; Felikson, D.; Catania, G. A.; Nash, J. D.; Shroyer, E.; Bartholomaus, T.; Stearns, L. A.; van den Broeke, M.

    2015-12-01

    Meltwater accumulated on the Greenland Ice Sheet (GrIS) drains to glacier beds, often discharging into outlet glacier fjords hundreds of meters below sea level. The injection of buoyant meltwater at depth drives a turbulent plume that entrains warm bottom water as it rises along the ice face, resulting in increased submarine melt rates. Recent studies have used remotely sensed data to identify distinct seasonal flow patterns in GrIS outlet glacier dynamics, suggesting some glaciers are especially sensitive to changes at the terminus. However, we currently lack an understanding of the corresponding regional patterns in near-glacier circulation that are a first-order control on submarine melt rates and indirectly modulate the resultant estuarine exchange flow and mixing of fjord waters. In this study, we use a buoyant plume model combined with a synthesis of shipboard hydrography, moored observations, estimates of subglacial discharge, and remotely sensed data on glacier characteristics, to provide an estimate of plume properties across GrIS outlet glaciers in both time and space. We validate our model results with detailed ice-ocean measurements from neighboring outlet glacier fjords in Uummannaq Bay, west Greenland. Model and observations agree that strongly stratified fjords with deep outlet glaciers result in warm, subsurface plumes, while shallow fjords result in surface-intensified plumes that retain their cold meltwater signature. We compare these results to a high-resolution ocean model to provide an estimate of submarine melt rates during peak summer discharge. One advantage of our approach is the rapid characterization of distinct plume regimes across GrIS outlet glacier parameter space. Finally, we compare these plume regimes with characteristics of glacier behavior (ice velocity, surface elevation, terminus position), over decadal and seasonal time-scales. This comparison allows us to investigate which outlet glacier systems might be more sensitive to

  16. Has dynamic thinning switched off in south-east Greenland?

    NASA Astrophysics Data System (ADS)

    Murray, T.; Scharrer, K.; James, T.; Luckman, A.; Selmes, N.; Cook, S.; Hughes, A.; Cordero Llana, L.; Booth, A.; McGovern, J.; Rutt, I.

    2008-12-01

    Following a relatively stable period during the 1990s, dramatic changes have been reported for many tidewater outlets in SE Greenland. Some of the most important results come from measurements using the GRACE (Gravity Recovery and Climate Experiment) mission (1, 2). These data clearly identified the SE of the Greenland Ice Sheet (GrIS) as having the highest rates of mass loss. Two of the major outlet glaciers in this area, Helheim and Kangerdlugssuaq accelerated by about 100% and 40%, respectively, and their calving fronts retreated by several km (3, 4). Retreat and acceleration occurred in two phases during summer 2003 and 2005 at Helheim, and in a single period between late 2004 and early 2005 at Kangerdlugssuaq. Further south, widespread glacier acceleration between 1996 and 2005 affected most of the outlet glaciers, and Greenland's mass loss doubled in the period (5). Increased discharge due to thinning in the marginal areas, coupled to rapid changes in ice dynamics and synchronous retreat of calving front positions, led to speculations that the GrIS had crossed a "tipping point" induced by global warming. However, subsequent studies in summer 2006 showed that Helheim and Kangerdlugssuaq had simultaneously slowed down again and thinning stopped (6). In summer 2007, we collected lidar data over Helheim and Kangerdlugssuaq flown by the NERC Airborne Research and Survey Facility. Data collected were single swaths over mountain areas, as well as centerline profiles. In cooperation with NASA Goddard Space Flight Center, we conducted a similar but extended campaign in 2008, collecting lidar and radar data for the 16 largest outlet glaciers in SE Greenland, targeting the full extent of the major GRACE anomaly. We used lidar swaths from bedrock as ground-control for extracting DEMs from ASTER satellite images covering the period with major changes in 2004 to 2006, and compared them to lidar and SPOT 5 DEMs to produce the most recent volume change and velocity estimates

  17. Seafloor geomorphology and glacimarine sedimentation associated with fast-flowing ice sheet outlet glaciers in Disko Bay, West Greenland

    NASA Astrophysics Data System (ADS)

    Streuff, Katharina; Ó Cofaigh, Colm; Hogan, Kelly; Jennings, Anne; Lloyd, Jeremy M.; Noormets, Riko; Nielsen, Tove; Kuijpers, Antoon; Dowdeswell, Julian A.; Weinrebe, Wilhelm

    2017-08-01

    Fast-flowing outlet glaciers currently drain the Greenland Ice Sheet (GIS), delivering ice, meltwater and debris to the fjords around Greenland. Although such glaciers strongly affect the ice sheet's mass balance, their glacimarine processes and associated products are still poorly understood. This study provides a detailed analysis of lithological and geophysical data from Disko Bay and the Vaigat Strait in central West Greenland. Disko Bay is strongly influenced by Jakobshavn Isbræ, Greenland's fastest-flowing glacier, which currently drains ∼7% of the ice sheet. Streamlined glacial landforms record the former flow of an expanded Jakobshavn Isbræ and adjacent GIS outlets through Disko Bay and the Vaigat Strait towards the continental shelf. Thirteen vibrocores contain a complex set of lithofacies including diamict, stratified mud, interbedded mud and sand, and bioturbated mud deposited by (1) suspension settling from meltwater plumes and the water column, (2) sediment gravity flows, and (3) iceberg rafting and ploughing. The importance of meltwater-related processes to glacimarine sedimentation in West Greenland fjords and bays is emphasised by the abundance of mud preserved in the cores. Radiocarbon dates constrain the position of the ice margin during deglaciation, and suggest that Jakobshavn Isbræ had retreated into central Disko Bay before 10.6 cal ka BP and to beyond Isfjeldsbanken by 7.6-7.1 cal ka BP. Sediment accumulation rates were up to 1.7 cm a-1 for ice-proximal glacimarine mud, and ∼0.007-0.05 cm a-1 for overlying distal sediments. In addition to elucidating the deglacial retreat history of Jakobshavn Isbræ, our findings show that the glacimarine sedimentary processes in West Greenland are similar to those in East Greenland, and that variability in such processes is more a function of time and glacier proximity than of geographic location and associated climatic regime.

  18. Ocean properties, ice-ocean interactions, and calving front morphology at two major west Greenland glaciers

    NASA Astrophysics Data System (ADS)

    Chauché, N.; Hubbard, A.; Gascard, J.-C.; Box, J. E.; Bates, R.; Koppes, M.; Sole, A.; Patton, H.

    2013-11-01

    Warm sub-polar mode water (SPMW) has been identified as a primary driver of mass loss of marine terminating glaciers draining the Greenland Ice Sheet (GrIS) yet, the specific mechanisms by which SPMW interacts with these tidewater termini remain uncertain. We present oceanographic data from Rink Glacier (RG) and Store Glacier (SG) fjords, two major marine outlets draining the western sector of the GrIS into Baffin Bay over the contrasting melt-seasons of 2009 and 2010. Submarine melting occurs wherever ice is in direct contact with warmer water and the consistent presence of 2.8 °C SPMW adjacent to both ice fronts below 400 m throughout all surveys indicates that melting is maintained by a combination of molecular diffusion and large scale, weak convection, diffusional (hereafter called ubiquitous) melting. At shallower depths (50-200 m), cold, brine-enriched water (BEW) formed over winter appears to persist into the summer thereby buffering this melt by thermal insulation. Our surveys reveal four main modes of glacier-ocean interaction, governed by water depth and the rate of glacier runoff water (GRW) injected into the fjord. Deeper than 200 m, submarine melt is the only process observed, regardless of the intensity of GRW or the depth of injection. However, between the surface and 200 m depth, three further distinct modes are observed governed by the GRW discharge. When GRW is weak (≲1000 m3 s-1), upward motion of the water adjacent to the glacier front is subdued, weak forced or free convection plus diffusional submarine melting dominates at depth, and seaward outflow of melt water occurs from the glacier toe to the base of the insulating BEW. During medium intensity GRW (∼1500 m3 s-1), mixing with SPMW yields deep mixed runoff water (DMRW), which rises as a buoyant plume and intensifies local submarine melting (enhanced buoyancy-driven melting). In this case, DMRW typically attains hydrostatic equilibrium and flows seaward at an intermediate depth of

  19. All Is Not Lost: The Transition from Order to Disorder in Greenland's Glaciers

    NASA Astrophysics Data System (ADS)

    Walker, C. C.; Schmidt, B. E.; Bassis, J. N.

    2014-12-01

    Iceberg calving is a major process involved in the removal of large volumes of ice from ice sheets to the oceans, but remains relatively poorly understood. The part of the puzzle that remains the least clear is the dynamics involved in the transition between intact glacier ice and rapid fragmentation during calving events. Because calving is a sudden rapid event, it is often the case that what gets captured by satellite observation is the before and after, rather than the exact moment of failure. Here we exploit this fact and use a statistical approach using a collapse model to investigate whether or not there exists a quantifiable critical fracture density, or "critical mass" of closely-spaced fractures, beyond which dynamic fragmentation of the glacier occurs. To do this we study the size distribution of fragments in proglacial mélange, using this information to infer physical properties of the pre-collapsed ice, such as material strength and the energy necessary to create a fragmentation event using methods widely applied in civil and even weapons engineering, but not previously applied in a glaciological context. Characterizing fracture density at different locations and quantifying a critical factor to describe the transition from highly-fractured to collapse/fragmentation region enable us to understand the distribution of observable surface fracture patterns and underlying differences within regions of individual glaciers and between glaciers. This investigation is well-served by the only-recently-available high resolution data over Greenland's glaciers by LandSat, MODIS and Operation IceBridge, among others. While many studies have focused on the propagation of crevasses in the glacier ice as a means of predicting calving, the main goal of this work is to consider the physical transition between the two phases of collapse. As such, our work focuses (1) on the pre-collapse state as characterized by crevasse pattern formation in the glacier, or level of

  20. Effect of fjord geometry on Greenland mass loss in a warming climate (Invited)

    NASA Astrophysics Data System (ADS)

    Nick, F. M.; Vieli, A.; Andersen, M. L.; Joughin, I. R.

    2013-12-01

    Over the past decade, ice loss from the Greenland Ice Sheet increased as a result of both increased surface melting and ice discharge through the narrow outlet glaciers. The complicated behaviour of narrow outlet glaciers has not yet been fully captured by the ice-sheet models used to predict Greenland's contribution to future sea level. Here we try to quantify the future dynamic contribution of four major marine terminating outlet glaciers to sea-level rise. We use a glacier flow line model that includes a fully dynamic treatment of marine termini to simulate behavior of Helheim, Kangerdlugssuaq, Petermann and Jakobshavn Isbræ. The contribution from these glaciers to sea-level rise is largely (80%) dynamic in origin and is caused by several episodic retreats past overdeepenings in outlet glacier troughs. Model results show that the shape of the glacier and its fjord can alter how the glacier will respond to a changing climate. Dynamic losses are mainly related to channel geometry and occur when an ice front retreats from a basal high through an overdeepening. Subsequent decelerations in retreat and mass loss mostly coincide with a decrease in water depth as the glacier retreats or re-advances to a new or previous bathymetric high. In some cases, channel narrowing may temporarily slowdown the terminus retreat even when the terminus is located on an upward bed slope.

  1. Interactions of the Greenland Petermann Glacier with the ocean: An initial perspective (Invited)

    NASA Astrophysics Data System (ADS)

    Falkner, K. K.; Johnson, H. L.; Melling, H.; Muenchow, A.; Samelson, R. M.; Friends Of Petermann

    2010-12-01

    Petermann Glacier is major outlet glacier that drains 6% of the area of the Greenland Ice Sheet in western North Greenland. It is one of four major outlet glaciers on Greenland with a grounding line substantially below sea level (about 500m) and one of two such glaciers to retain a substantial floating tongue. The floating ice tongue of Petermann glacier is thought to lose at least 80% of its mass through ocean interaction. Based on three opportunistic ocean surveys in Petermann Fjord, we present an overview of circulation at the fjord mouth, hydrographic structure beneath the ice tongue, oceanic heat delivered to the under-ice cavity and the fate of the resulting melt water. We also present an historical perspective on the August 2010 major calving event. The 1100m-deep fjord is separated from neighboring Hall Basin by a sill that is inferred to lie between 350m and 450m deep. Hall Basin is a section of Nares Strait that connects the Arctic Ocean (at the Lincoln Sea proceeding southward through Robeson Channel, Hall Basin, Kennedy Channel, Kane Basin and Smith Sound) to Baffin Bay. Sills in the Lincoln Sea (290m) and in Kane Basin (220m) restrict communication with the Arctic Ocean and Baffin Bay. The net flux of seawater through Nares Strait is southward and relatively fresh, conditioned by sources and processes within the Arctic Ocean and locally. Within Petermann Fjord, glacial melt water appears on the northeast side at 200-600m. A cyclonic gyre occurs within the fjord mouth, with outflow on the northeast side. Oceanic heat fluxes into the fjord are sufficient to account for the observed rate of basal melting. Cold, low salinity water intrudes far under the ice and likely limits basal melting to the inland half of the tongue. The recent major calving event resulted in a loss of 300 km2 or about 20% of the total area of the floating tongue, most of which remained intact as an ice island that garnered much media attention. Available observations show calving to

  2. Voume Change of Greenland's Peripheral Glaciers and Ice Caps from CryoSat-2

    NASA Astrophysics Data System (ADS)

    Briggs, K.

    2016-12-01

    Glaciers and ice caps (GICs) are sensitive indicators of climate change and are large contributors to present global eustatic sea level rise. The peripheral GICs of the Greenland Ice Sheet cover an area of 89,700 km2 or approximately 12% of the total global area of GICs. Between 2003 and 2009 it is estimated that the Greenland GICs were losing mass at a rate of 38 ± 7 gt/yr, which is about 15% of the estimated global mass loss from GICs (Gardner et al., 2013) and around 16% of the estimated mass loss from the main ice sheet (Shepherd et al., 2012). Here we present more recent volume change estimates of Greenland's peripheral ice caps for the period from 2010 to 2014 using data from the CryoSat-2 mission. We show how the improved capabilities of CryoSat-2 in regions of complex terrain has led to more than an eight-fold increase in the density of elevation change estimates in the region compared to estimates from earlier altimeter missions. Estimates of elevation change are evaluated using contemporaneous measurements from IceBridge airborne altimetry revealing excellent levels of agreement. We investigate emerging and evolving signals of volume change through comparison with earlier estimates from ICESat (Bolch et al., 2013).

  3. Tidewater dynamics at Store Glacier, West Greenland from daily repeat UAV surveys

    NASA Astrophysics Data System (ADS)

    Ryan, Jonathan; Hubbard, Alun; Toberg, Nick; Box, Jason; Todd, Joe; Christoffersen, Poul; Neal, Snooke

    2017-04-01

    A significant component of the Greenland ice sheet's mass wasteage to sea level rise is attributed to the acceleration and dynamic thinning at its tidewater margins. To improve understanding of the rapid mass loss processes occurring at large tidewater glaciers, we conducted a suite of daily repeat aerial surveys across the terminus of Store Glacier, a large outlet draining the western Greenland Ice Sheet, from May to July 2014 (https://www.youtube.com/watch?v=-y8kauAVAfE). The unmanned aerial vehicles (UAVs) were equipped with digital cameras, which, in combination with onboard GPS, enabled production of high spatial resolution orthophotos and digital elevation models (DEMs) using standard structure-from-motion techniques. These data provide insight into the short-term dynamics of Store Glacier surrounding the break-up of the sea-ice mélange that occurred between 4 and 7 June. Feature tracking of the orthophotos reveals that mean speed of the terminus is 16 - 18 m per day, which was independently verified against a high temporal resolution time-series derived from an expendable/telemetric GPS deployed at the terminus. Differencing the surface area of successive orthophotos enable quantification of daily calving rates, which significantly increase just after melange break-up. Likewise, by differencing bulk freeboard volume of icebergs through time we could also constrain the magnitude and variation of submarine melt. We calculate a mean submarine melt rate of 0.18 m per day throughout the spring period with relatively little supraglacial runoff and no active meltwater plumes to stimulate fjord circulation and upwelling of deeper, warmer water masses. Finally, we relate calving rates to the zonation and depth of water-filled crevasses, which were prominent across parts of the terminus from June onwards.

  4. Tidewater Dynamics at Store Glacier, West Greenland from Daily Repeat UAV Survey

    NASA Astrophysics Data System (ADS)

    Hubbard, A., II; Ryan, J.; Toberg, N.; Todd, J.; Christoffersen, P.; Snooke, N.; Box, J. E.

    2015-12-01

    A significant component of the Greenland ice sheet's mass wasteage to sea level rise is attributed to the acceleration and dynamic thinning at its tidewater margins. To improve understanding of the rapid mass loss processes occurring at large tidewater glaciers, we conducted a suite of daily repeat aerial surveys across the terminus of Store Glacier, a large outlet draining the western Greenland Ice Sheet, from May to July 2014 (https://www.youtube.com/watch?v=-y8kauAVAfE). A suite flock of Unmanned Aerial Vehicles (UAVs) were equipped with digital cameras, which, in combination with onboard GPS, enabled production of high spatial resolution orthophotos and digital elevation models (DEMs) using standard structure-from-motion techniques. These data provide insight into the short-term dynamics of Store Glacier surrounding the break-up of the sea-ice mélange that occurred between 4 and 7 June. Feature tracking of the orthophotos reveals that mean speed of the terminus is 16 - 18 md-1, which was independently verified against a high temporal resolution time-series derived from an expendable/telemetric GPS deployed at the terminus. Differencing the surface area of successive orthophotos enable quantification of daily calving rates, which significantly increase just after melange break-up. Likewise, by differencing bulk freeboard volume of icebergs through time we could also constrain the magnitude and variation of submarine melt. We calculate a mean submarine melt rate of 0.18 md-1 throughout the spring period with relatively little supraglacial runoff and no active meltwater plumes to stimulate fjord circulation and upwelling of deeper, warmer water masses. Finally, we relate calving rates to the zonation and depth of water-filled crevasses, which were prominent across parts of the terminus from June onwards.

  5. Understanding changes in ice dynamics of southeast Greenland glaciers from high resolution gravimetry data and satellite remote sensing observations

    NASA Astrophysics Data System (ADS)

    Millan, R.; Rignot, E. J.; Mouginot, J.; Menemenlis, D.; Morlighem, M.; Wood, M.

    2016-12-01

    Southeast Greenland has been one of the largest contributors to ice mass losses in Greenland in the last few decades mostly as a result of changes in ice dynamics, and to a lesser extent due to the steady increase in runoff. In 1996, the region was thinning up to the ice divide (Krabill et al., 1999) and the change were clearly of ice dynamics nature. Ice-ocean interactions played a central role in triggering a faster, systematic retreat around year 2002-2005 as water of Atlantic origin started to intrude the fjords in larger amounts due to a change in oceanic circulation in the Irminger sea. The glacier response varied significantly from one glacier to the next in response to the oceanic change, which we attribute to variatioins in fjord bathymetry, geometry control on the glaciers and calving speed of the glaciers. This region is however characterized by a dearth of topography data: the fjords have never been mapped and bed topography is challenging to obtain with radio echo sounding techniques. Here, we employ a combination of Operation IceBridge (OIB) high-resolution airborne gravity from 2016, Ocean Melting Greenland (OMG) EVS-2 mission low resolution gravity from 2016, and OMG bathymetry data from 2016 to map the bed elevation of the glaciers and fjords over the entire southeast Greenland combining gravity, thickness, and bathymetry. The data reveal the true depth of the fjords and the glacier thickness at the ice front, in a seamless fashion. We combine these data with a history of ice discharge combining estimates of ice thickness with a time series of ice velocity going back to the early 1990s. We form a time series of ice discharge, glacier per glacier, which is compared with surface mass balance from the RACMO 1-km downscaled model. We compare the results with simulations of ice melt along the calving faces of the glaciers to draw conclusions about the sensitivity of each glacier to climate forcing and re-interpret their pattern of retreat in the last

  6. Methane seeps along boundaries of receding glaciers in Alaska and Greenland

    NASA Astrophysics Data System (ADS)

    Walter Anthony, K. M.; Anthony, P. M.; Grosse, G.; Chanton, J.

    2012-12-01

    Glaciers, ice sheets, and permafrost form a 'cryosphere cap' that traps methane formed in the subsurface, restricting its flow to the Earth's surface and atmosphere. Despite model predictions that glacier melt and degradation of permafrost open conduits for methane's escape, there has been a paucity of field evidence for 'subcap' methane seepage to the atmosphere as a direct result of cryosphere disintegration in the terrestrial Arctic. Here, we document for the first time the release of sub-cryosphere methane to lakes, rivers, shallow marine fjords and the atmosphere from abundant gas seeps concentrated along boundaries of receding glaciers and permafrost thaw in Alaska and Greenland. Through aerial and ground surveys of 6,700 lakes and fjords in Alaska we mapped >150,000 gas seeps identified as bubbling-induced open holes in seasonal ice. Using gas flow rates, stable isotopes, and radiocarbon dating, we distinguished recent ecological methane from subcap, geologic methane. Subcap seeps had anomalously high bubbling rates, 14C-depletion, and stable isotope values matching microbial sources associated with sedimentary deposits and coal beds as well as thermogenic methane accumulations in Alaska. Since differential ice loading can overpressurize fluid reservoirs and cause sediment fracturing beneath ice sheets, and since the loss of glacial ice reduces normal stress on ground, opens joints, and activates faults and fissures, thereby increasing permeability of the crust to fluid flow, we hypothesized that in the previously glaciated region of Southcentral Alaska, where glacial wastage continues presently, subcap seeps should be disproportionately associated with neotectonic faults. Geospatial analysis confirmed that subcap seep sites were associated with faults within a 7 km belt from the modern glacial extent. The majority of seeps were located in areas affected by seismicity from isostatic rebound associated with deglaciation following the Little Ice Age (LIA; ca

  7. Comparison of in situ and satellite-derived reflectances of Forbindels Glacier, Greenland

    NASA Technical Reports Server (NTRS)

    Hall, D. K.; Bindschadler, R. A.; Foster, J. L.; Chang, A. T. C.; Siddalingaiah, H.

    1990-01-01

    In situ and Landsat Thematic Mapper (TM)-derived reflectances of the Forbindels Glacier, Greenland, were acquired in August of 1986. Reflectance was measured in situ using a portable spectrometer and calculated using TM data and ancillary information. Atmospheric corrections were applied to the at-satellite reflectances resulting in a 5-17 percent increase in reflectance relative to the calculated at-satellite reflectances. The satellite-derived, corrected reflectances obtained from the non-saturated TM bands corresponded to within 6 percent of the in situ reflectances measured at the nadir viewing angle with a portable spectrometer. Measurement of nadir reflectances using Landsat-TM data appears to be a viable method to obtain physically meaningful reflectances of ice and snow.

  8. Complete spatiotemporal freshwater flux budget for a major Greenland glacier-fjord system

    NASA Astrophysics Data System (ADS)

    Moon, Twila; Sutherland, David; Carroll, Dustin; Kehrl, Laura; Straneo, Fiamma; Felikson, Denis

    2017-04-01

    Freshwater flux from ice sheet mass loss raises global sea level, influences large-scale ocean circulation and stratification, and affects biological systems. Freshwater flux in glacial fjords comes from several sources: ice sheet surface melt discharged subglacially at the glacial termini, terrestrial runoff, submarine terminus melt, and melt from icebergs throughout the fjord (here, including icebergs, bergy bits, and melánge). Melt from icebergs is poorly constrained; previous efforts use limited-footprint satellite images and fail to distinguish iceberg freshwater flux from other melt sources. We have developed a new method, combining in situ and remote sensing observations with a parameterized iceberg melt model and climate reanalysis data, to calculate freshwater flux from icebergs and create a spatiotemporally complete fjord freshwater budget. Here, we apply this method to Sermilik Fjord, a major glacier-fjord system in southeast Greenland. We generate complete freshwater budgets for summer and winter periods during 2008-2013 as well as mean monthly estimates of iceberg freshwater flux over a full year. Along with this enhanced understanding of iceberg freshwater flux across time, our estimates also spatially resolve meltwater flux across the full water depth of the fjord. We find that more than 70% of iceberg melt production occurs below 10 m depth. We also compare iceberg melt flux to other freshwater sources, demonstrating that iceberg melt dominates freshwater production. Our work provides the first calculation of iceberg freshwater flux across the full fjord water depth, estimates the first complete freshwater budget for a major Greenland glacier-fjord system, and provides monthly to interannual comparisons across freshwater sources. Ultimately, these results provide a path forward in accurately representing freshwater flux, including iceberg melt production, in large-scale climate models.

  9. Fjord - Glacier Ice Interactions: Nuup Kangerlua (Godthåbsfjord) Southwest Greenland

    NASA Astrophysics Data System (ADS)

    Motyka, R. J.; Truffer, M.; Dryer, W. P.; Fahnestock, M. A.; Cassotto, R. K.; Mortensen, J.; Rysgaard, S.

    2012-12-01

    The study of interactions between glaciers, fjords, and the ocean in coastal Greenland is still in its infancy. Circulation of warm ocean waters into fjords has been hypothesized to play an important role in destabilizing and modulating glacier discharge from outlet glaciers in Greenland, but details on the dynamics of this interaction remain sparse. To help fill this gap, we conducted a series of hydrographic measurements over a six-day period in late August 2011 in the proglacial fjord Kangersuneq at the head of Nuup Kangerlua (Godthåbsfjord) near Nuuk in southwest Greenland. Because of iceberg conditions, we were unable to approach any closer than 12 km to the tidewater glacier Kangiata Nunaata Sermia (KNS) at the head of the fjord. We conducted the majority of our measurements over the KNS Little Ice Age (LIA) moraine, a sill which forms a barrier between the inner and outer fjord. The LIA sill lies about 22 km from KNS, spans the 4-km-wide fjord and has a maximum water depth of 170 m. Water depths fall to over 300 m on either side of this sill and all water entering or leaving the inner basin must flow over it. For comparison, we also conducted transects at a second location inside the inner basin, 12 km from the KNS terminus and in much deeper water (> 300 m). Our transects included shipboard CTD (conductivity, temperature, density) and current measurements, the latter using rail-mounted 150 kHz and 600 kHz RDI ADCPs (Acoustic Doppler Current Profilers). Iceberg conditions in the fjord prevented measurements while underway. The CTD measurements showed a highly stratified water column capped by a 5 m freshwater layer. The warmest (3 deg. C) and most saline water (32) lies directly over the sill, near the bottom of the water column. The freshwater fraction at 20 m water depth is 7.6% with 6.0% from subglacial freshwater discharge and 1.6% derived from submarine melting of ice. We timed our survey to bracket the neap tide to reduce complexities related to tidal

  10. A tipping point in refreezing accelerates mass loss of Greenland's glaciers and ice caps.

    PubMed

    Noël, B; van de Berg, W J; Lhermitte, S; Wouters, B; Machguth, H; Howat, I; Citterio, M; Moholdt, G; Lenaerts, J T M; van den Broeke, M R

    2017-03-31

    Melting of the Greenland ice sheet (GrIS) and its peripheral glaciers and ice caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS mass loss are well studied, the spatial and temporal evolution of GICs mass loss and the acting processes have remained unclear. Here we use a novel, 1 km surface mass balance product, evaluated against in situ and remote sensing data, to identify 1997 (±5 years) as a tipping point for GICs mass balance. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 mass loss to 36±16 Gt(-1), or ∼14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming.

  11. A tipping point in refreezing accelerates mass loss of Greenland's glaciers and ice caps

    NASA Astrophysics Data System (ADS)

    Noël, B.; van de Berg, W. J.; Lhermitte, S.; Wouters, B.; Machguth, H.; Howat, I.; Citterio, M.; Moholdt, G.; Lenaerts, J. T. M.; van den Broeke, M. R.

    2017-03-01

    Melting of the Greenland ice sheet (GrIS) and its peripheral glaciers and ice caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS mass loss are well studied, the spatial and temporal evolution of GICs mass loss and the acting processes have remained unclear. Here we use a novel, 1 km surface mass balance product, evaluated against in situ and remote sensing data, to identify 1997 (+/-5 years) as a tipping point for GICs mass balance. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 mass loss to 36+/-16 Gt-1, or ~14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming.

  12. A tipping point in refreezing accelerates mass loss of Greenland's glaciers and ice caps

    PubMed Central

    Noël, B.; van de Berg, W. J; Lhermitte, S.; Wouters, B.; Machguth, H.; Howat, I.; Citterio, M.; Moholdt, G.; Lenaerts, J. T. M.; van den Broeke, M. R.

    2017-01-01

    Melting of the Greenland ice sheet (GrIS) and its peripheral glaciers and ice caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS mass loss are well studied, the spatial and temporal evolution of GICs mass loss and the acting processes have remained unclear. Here we use a novel, 1 km surface mass balance product, evaluated against in situ and remote sensing data, to identify 1997 (±5 years) as a tipping point for GICs mass balance. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 mass loss to 36±16 Gt−1, or ∼14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming. PMID:28361871

  13. Mass loss of the Greenland peripheral glaciers and ice caps from satellite altimetry

    NASA Astrophysics Data System (ADS)

    Wouters, Bert; Noël, Brice; Moholdt, Geir; Ligtenberg, Stefan; van den Broeke, Michiel

    2017-04-01

    At its rapidly warming margins, the Greenland Ice Sheet is surrounded by (semi-)detached glaciers and ice caps (GIC). Although they cover only roughly 5% of the total glaciated area in the region, they are estimated to account for 15-20% of the total sea level rise contribution of Greenland. The spatial and temporal evolution of the mass changes of the peripheral GICs, however, remains poorly constrained. In this presentation, we use satellite altimetry from ICESat and Cryosat-2 combined with a high-resolution regional climate model to derive a 14 year time series (2003-2016) of regional elevation and mass changes. The total mass loss has been relatively constant during this period, but regionally, the GICs show marked temporal variations. Whereas thinning was concentrated along the eastern margin during 2003-2009, western GICs became the prime sea level rise contributors in recent years. Mass loss in the northern region has been steadily increasing throughout the record, due to a strong atmospheric warning and a deterioration of the capacity of the firn layer to buffer the resulting melt water.

  14. Subglacial water flux routing for the 79°N Glacier, Greenland

    NASA Astrophysics Data System (ADS)

    Rückamp, M.; Beyer, S.; Kleiner, T.; Steinhage, D.; Helm, V.; Dohn, L.; Humbert, A.

    2015-12-01

    The hydrological regime of Greenland is of major importance for the ice dynamics, as water acts as lubricant for ice flow. The 79°N Glacier is feed by two branches, one southern coming from the North East Greenland Ice Stream (NEGIS) and one northern branch. We have applied a flux routing type of hydrological model to this area prior to an airborne ice penetrating radar campaign that has been carried out in June 2015. Flux routing scheme can be used to distribute the basal water down the static hydraulic potential. In this study, local sinks in the potential field were filled using a priority flooding approach, which allows a more realistic continuation of water flow across the sinks. One distinct sink was found in the NEGIS branch, indicating a potential lake location. In the northern branch, the water flux appeared to be concentrated with a clear transition to a potentially dry area. We show the subglacial water fluxes for constant basal melt rates, as well as for spatially varying melt rates taken from the Parallel Ice Sheet Model (PISM). Using the PISM output allows assessing the likely drainage pathways with a more realistic availability of water. The airborne campaign was covering cross sections over these two locations, of which we will present the radar sections.

  15. Collaborating with the local community of Kullorsuaq, Greenland to obtain high-quality hydrographic measurements near Alison Glacier

    NASA Astrophysics Data System (ADS)

    Porter, D. F.; Turrin, M.; Tinto, K. J.; Giulivi, C. F.; Cochran, J. R.; Bell, R. E.

    2014-12-01

    Warming ocean waters around Greenland have been implicated, along with warmer air temperatures, in the rapid increase of melt of the tidewater glaciers that drain the ice sheet. Most available regional oceanographic measurements have been collected during the summer seasons and are concentrated near the largest and most accessible glaciers. In order to gain a more comprehensive picture of the changing environment around the entirety of Greenland, more fjords, especially in the north, must be sampled. In July 2014, we travelled to Kullorsuaq in Northwest Greenland in order to foster a partnership with the local community to obtain new hydrographic data from CTD casts near Alison Glacier (74.6N, 57W). The terminus of this glacier abruptly retreated 10 km between 2000 and 2006. Although adequate observations from that time period are unavailable, our recently collected temperature and salinity data suggests that the deep water near Alison is similar to the waters further south, where near-synchronous ocean warming and glacial acceleration has been documented. Over the course of two sampling days, a hand-operated winch from a small boat was used to make standard CTD casts in front of Alison Glacier. We find evidence of glacial and mélange melt and the signature of both Polar and Atlantic Water masses at depth. Along-fjord casts illustrate how the ocean waters are modified as they circulate in and out of the fjord and the interaction of this water with the melting glacial front. At 500m depths, ocean temperatures are about 3°C above the in-situ freezing point of seawater, suggesting a possible influence of warm ocean waters on the mass loss of Alison Glacier. Using NASA Operation IceBridge and satellite altimetry data, we relate our new hydrographic data to the observed recent changes in Alison Glacier. An additional important result is that this short field campaign uncovered the possibility of working with local Greenlandic communities to aid scientists in both

  16. Bathymetry data reveal glaciers vulnerable to ice-ocean interaction in Uummannaq and Vaigat glacial fjords, west Greenland

    NASA Astrophysics Data System (ADS)

    Rignot, E.; Fenty, I.; Xu, Y.; Cai, C.; Velicogna, I.; Cofaigh, C. Ó.; Dowdeswell, J. A.; Weinrebe, W.; Catania, G.; Duncan, D.

    2016-03-01

    Marine-terminating glaciers play a critical role in controlling Greenland's ice sheet mass balance. Their frontal margins interact vigorously with the ocean, but our understanding of this interaction is limited, in part, by a lack of bathymetry data. Here we present a multibeam echo sounding survey of 14 glacial fjords in the Uummannaq and Vaigat fjords, west Greenland, which extends from the continental shelf to the glacier fronts. The data reveal valleys with shallow sills, overdeepenings (>1300 m) from glacial erosion, and seafloor depths 100-1000 m deeper than in existing charts. Where fjords are deep enough, we detect the pervasive presence of warm, salty Atlantic Water (AW) (>2.5°C) with high melt potential, but we also find numerous glaciers grounded on shallow (<200 m) sills, standing in cold (<1°C) waters in otherwise deep fjords, i.e., with reduced melt potential. Bathymetric observations extending to the glacier fronts are critical to understand the glacier evolution.

  17. A millennial-scale record of tidewater glacier advance and retreat, SW Greenland.

    NASA Astrophysics Data System (ADS)

    Pearce, Danni; Mair, Doug; Rea, Brice; Schofield, Ed; Lea, James; Barr, Iestyn; Kamenos, Nick; Schoenrock, Kate

    2017-04-01

    Tidewater glaciers (TWGs) exert a major control on the short- and long-term mass balance of the Greenland Ice Sheet (GrIS) and have experienced widespread retreat over the last century. However, in many cases inferences on their dynamics, prior to this, are poorly constrained due to a lack of observations and paucity of mapped or mappable deglacial geomorphology. Especially lacking is evidence associated with TWG advance during the Little Ice Age (LIA, AD c. 1300 to 1850). Such data are crucial for numerical model calibration and validation in order to more confidently forward model ice sheet dynamics and projection future sea-level rise. Therefore, empirical data constraints from the palaeo-record, that span such timescales (decadal to millennial), are essential. Kangiata Nunaata Sermia (KNS) is the most dynamic TWG in SW Greenland, located c. 100 km inland from Nuuk, at the head of Godthabsfjord. KNS has received considerable research attention over the last decade but glacial geomorphological and numerical dating investigations have been limited. However, the adjacent topography and geomorphology presents a unique opportunity to reconstruct the advance and retreat dynamics over the LIA. We present detailed glacial geomorphological mapping for KNS, which followed a morphostratigraphic approach, using a combination of aerial photos, Landsat, a DEM and field mapping. This identified a three landsystems, which are associated with the LIA, pre-LIA and neoglacial. From the mapping inferences on rapid changes in meltwater routing have been inferred. When KNS reached its LIA maximum (c. 1761), the calving front was c. >22 km further along the fjord than present and a number of ice-dammed lakes were formed. We present new 14C dating from peat underlying lake sediments associated with an ice-dammed lake and buried palaeosols resulting from meltwater re-routing over topographic spillways. The ages support an early and rapid LIA advance phase, with advance rates being

  18. Sea ice breakup and marine melt of a retreating tidewater outlet glacier in northeast Greenland (81°N).

    PubMed

    Bendtsen, Jørgen; Mortensen, John; Lennert, Kunuk; K Ehn, Jens; Boone, Wieter; Galindo, Virginie; Hu, Yu-Bin; Dmitrenko, Igor A; Kirillov, Sergei A; Kjeldsen, Kristian K; Kristoffersen, Yngve; G Barber, David; Rysgaard, Søren

    2017-07-10

    Rising temperatures in the Arctic cause accelerated mass loss from the Greenland Ice Sheet and reduced sea ice cover. Tidewater outlet glaciers represent direct connections between glaciers and the ocean where melt rates at the ice-ocean interface are influenced by ocean temperature and circulation. However, few measurements exist near outlet glaciers from the northern coast towards the Arctic Ocean that has remained nearly permanently ice covered. Here we present hydrographic measurements along the terminus of a major retreating tidewater outlet glacier from Flade Isblink Ice Cap. We show that the region is characterized by a relatively large change of the seasonal freshwater content, corresponding to ~2 m of freshwater, and that solar heating during the short open water period results in surface layer temperatures above 1 °C. Observations of temperature and salinity supported that the outlet glacier is a floating ice shelf with near-glacial subsurface temperatures at the freezing point. Melting from the surface layer significantly influenced the ice foot morphology of the glacier terminus. Hence, melting of the tidewater outlet glacier was found to be critically dependent on the retreat of sea ice adjacent to the terminus and the duration of open water.

  19. Temporal Variations in Glacier Geometry and Glacial-Earthquake Source Parameters

    NASA Astrophysics Data System (ADS)

    Veitch, Stephen; Meredith, Nettles

    2013-04-01

    Source parameters for more than 300 glacial earthquakes in Greenland have now been published. Significant efforts have been made to establish the seismogenic source of these events, as well as their connection to broad changes in glacier-dynamic conditions on both local and Greenland-wide scales. Glacial earthquakes are caused by large ice-loss events at tidewater glaciers, and occur when the source glaciers are grounded or nearly grounded. There is a close correspondence between episodes of glacier retreat, thinning, and acceleration and the timing of glacial earthquakes. Motivated by temporal trends in earthquake location and force orientation in the published earthquake results, we compare changes in those source parameters with geometric changes at the source glaciers. We use Landsat 7 imagery from the four most seismically active glaciers in Greenland (Kangerdlugssuaq Glacier, Helheim Glacier, Jakobshavn Isbræ, and Kong Oscar Glacier) to measure both the position and orientation of the calving front. In the case of position, we consider changes in average calving-front and earthquake position during four time intervals, as errors in location for individual earthquakes are relatively large. We compare force orientations for individual earthquakes to the range of calving-front orientations observed over time at each source glacier. We find that changes in calving-front position are reflected in the glacial-earthquake locations, and that temporal variability in the force orientations results from the true variability in calving-front orientation. despite a high degree of variability, glacial-earthquake active-force orientations are consistent with the orientation of their source glaciers.

  20. A test bed for investigating the flow of outlet glaciers and ice streams embedded in the Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Calov, Reinhard; Rückamp, Martin; Schlegel, Rebecca; Ganopolski, Andrey; Humbert, Angelika

    2016-04-01

    Here, we define a test bed for fast flow regions and its vicinity embedded in an ice sheet. This test bed is designed for outlet glaciers and ice streams of the Greenland ice sheet. It consists of a fine resolution part with a manufactured basal trough over which the professional software COMSOL (Multiphysics Modeling Software) operates as a full-Stokes model. Results by COMSOL are compared with coarse resolution simulations with the ice-sheet model SICOPOLIS operating in shallow-ice-approximation mode and using parameterizations of the fast flow effects. For simplification, in this preliminary approach, both models run in isothermal mode. Definition of surface mass balance follows the EISMINT intercomparison project with parameters adapted to the Greenland ice sheet. In particular, we inspect with this test bed upstream and lateral flow effects of ice streams and outlet glaciers. We present first simulations with this approach, although presentation of the test bed itself is the main emphasis of this presentation.

  1. Constraining millennial scale dynamics of a Greenland tidewater glacier for the verification of a calving criterion based numerical model

    NASA Astrophysics Data System (ADS)

    Lea, J.; Mair, D.; Rea, B.; Nick, F.; Schofield, E.

    2012-04-01

    The ability to successfully model the behaviour of Greenland tidewater glaciers is pivotal to understanding the controls on their dynamics and potential impact on global sea level. However, to have confidence in the results of numerical models in this setting, the evidence required for robust verification must extend well beyond the existing instrumental record. Perhaps uniquely for a major Greenland outlet glacier, both the advance and retreat dynamics of Kangiata Nunata Sermia (KNS), Nuuk Fjord, SW Greenland over the last ~1000 years can be reasonably constrained through a combination of geomorphological, sedimentological and archaeological evidence. It is therefore an ideal location to test the ability of the latest generation of calving criterion based tidewater models to explain millennial scale dynamics. This poster presents geomorphological evidence recording the post-Little Ice Age maximum dynamics of KNS, derived from high-resolution satellite imagery. This includes evidence of annual retreat moraine complexes suggesting controlled rather than catastrophic retreat between pinning points, in addition to a series of ice dammed lake shorelines, allowing detailed interpretation of the dynamics of the glacier as it thinned and retreated. Pending ground truthing, this evidence will contribute towards the calibration of results obtained from a calving criterion numerical model (Nick et al, 2010), driven by an air temperature reconstruction for the KNS region determined from ice core data.

  2. Reverse glacier motion during iceberg calving and the cause of glacial earthquakes

    NASA Astrophysics Data System (ADS)

    Murray, T.; Nettles, M.; Selmes, N.; Cathles, L. M.; Burton, J. C.; James, T. D.; Edwards, S.; Martin, I.; O'Farrell, T.; Aspey, R.; Rutt, I.; Baugé, T.

    2015-07-01

    Nearly half of Greenland’s mass loss occurs through iceberg calving, but the physical mechanisms operating during calving are poorly known and in situ observations are sparse. We show that calving at Greenland’s Helheim Glacier causes a minutes-long reversal of the glacier’s horizontal flow and a downward deflection of its terminus. The reverse motion results from the horizontal force caused by iceberg capsize and acceleration away from the glacier front. The downward motion results from a hydrodynamic pressure drop behind the capsizing berg, which also causes an upward force on the solid Earth. These forces are the source of glacial earthquakes, globally detectable seismic events whose proper interpretation will allow remote sensing of calving processes occurring at increasing numbers of outlet glaciers in Greenland and Antarctica.

  3. Simulating Ice-Flow and Calving on Store Glacier, West Greenland, with a 3D Full Stokes Model

    NASA Astrophysics Data System (ADS)

    Todd, J.; Christoffersen, P.; Zwinger, T.; Luckman, A. J.; Benn, D.

    2015-12-01

    The mass balance and long-term stability of the ice sheets in Greenland and Antarctica depend heavily on the dynamics of their ice-ocean margins. Iceberg calving accounts for the majority of the net annual loss of ice in Antarctica and around half of that from Greenland. Furthermore, climate driven changes to dynamics at these calving margins can be transmitted far inland. Thus, predicting future sea level contribution from the cryosphere requires an improved understanding of calving, and the processes which link it to climate and ice-sheet flow. We present results from a new 3D calving model coupled to a full-Stokes, time evolving glacier dynamic model, implemented for Store Glacier, a 5-km-wide calving glacier in the Uummannaq region of West Greenland, which flows at a rate of 20 m/day at its terminus. The model is developed using the open source finite element package Elmer/Ice, with the criterion that calving occurs when surface and basal crevasses meet. Crevasses open in response to tensile stresses near the terminus and water pressure at the bed. When the model was applied in 2D for the central flowline of Store Glacier, we found that basal topography exerts overarching control on the long term position of the calving front, while ice mélange buttressing allows the seasonal extension of a floating tongue, which collapses in early summer. New results emerging from implementation of calving in a 3D model indicate significant spatial heterogeneity in calving dynamics because the northern half of the terminus is grounded whereas the southern half is floating. This contrasting setting affects calving dynamics, further underlining the importance of geometry and basal topography, and suggesting that lower dimensional calving models may miss important aspects of calving dynamics. Our results also suggest that implementing grounding line dynamics is important for modelling calving, even for glaciers which are, for the most part, firmly grounded.

  4. Rapid advance and retreat of a major Greenland tidewater glacier: demonstrating extreme sensitivity of terminus stability to climate change

    NASA Astrophysics Data System (ADS)

    Lea, J.; Mair, D. W.; Rea, B. R.; Schofield, J.; Kamenos, N.; Pearce, D.; Schoenrock, K. M.; Stachnik, L.; Vad, J.

    2016-12-01

    Here we present the first record of an advance and retreat cycle of a major Greenlandic tidewater glacier, providing evidence for advance rates occurring at a similar magnitude to contemporary retreat rates. Previous records of ice sheet outlet behaviour used for model validation are often limited to satellite/aerial photo observations, with the Little Ice Age (LIA) readvance curtailing the length of records by destroying geomorphological and sedimentological evidence of the advance dynamics. This temporally limits most records to the 20th century, where they are dominated by thinning/retreat behaviour. Their utility for providing a range of behaviour for effective model validation is therefore reduced. By reconstructing the advance and retreat of Kangiata Nunaata Sermia (KNS), SW Greenland, over the last 1000 years the dataset presented here overcomes these shortfalls. The topographic setting of KNS has allowed preservation of sediments recording the advance and upstream thickening of the glacier prior to its LIA maximum being achieved c.250 years ago. Subsequent to this, the glacier has the longest observationally based reconstruction of behaviour anywhere in Greenland, extending back to 1761 (Lea et al., 2014a; 2014b). By combining these records, a complete reconstruction of the advance and retreat cycle of this major outlet glacier from c. AD 1000 to present has been achieved. In combination with well-constrained boundary conditions, this provides an unparalleled dataset allowing the testing and validation of ice flow models that seek to simulate outlet glacier dynamics. The reconstruction itself indicates that KNS rapidly advanced by 17 km between c. AD 1100-1250, coincident with a rapid cooling in air temperature. It is notable that the terminus response corresponds to a mean advance rate of 110 m a-1, which is of a similar magnitude to present-day terminus retreat rates. A further advance of 5 km occurred subsequently, taking the terminus to its LIA maximum

  5. A synthesis of the ongoing seasonal work in a west Greenland tidewater outlet glacier fjord, Godthåbsfjord

    NASA Astrophysics Data System (ADS)

    Mortensen, J.; Bendtsen, J.; Rysgaard, S.

    2015-12-01

    The coastal waters off west Greenland is subjected to significant temperature fluctuations which might affect the mass loss from local tidewater outlet glaciers from the Greenland Ice Sheet in different ways. We present a comprehensive hydrographic data set from a west Greenland fjord, Godthåbsfjord, a fjord in contact with the Greenland Ice Sheet through tidewater outlet glaciers. We analyze with respect to water masses, dynamics, seasonal and interannual hydrographic variability. Through seasonal observations of hydrographic and moored observations we recognize a seasonal pattern in the fjords circulation system, where an intermediate baroclinic circulation mode driven by tidal currents at the fjord entrance is associated as an important local heat source for the fjord. Four distinct circulation modes are observed in the fjord of which all can contribute to glacial ice melt. In water observation of a subglacial plume core will be presented and discussed with respect to vertical distribution of water masses and local heat budget in the fjord. The example of the extreme case of subglacial plume will be discussed (ice-dammed lake drainage).

  6. Hydrologically active palaeofluvial and subglacial channel networks beneath Humboldt Glacier, Greenland

    NASA Astrophysics Data System (ADS)

    Ely, Jeremy; Livingstone, Stephen; Chu, Winnie; Kingslake, Jonathan

    2017-04-01

    Subglacial drainage systems influence both the flow of overlying ice and the evolution of subglacial landscapes. Yet, the persistence, pattern, origin and spatio-temporal evolution of subglacial drainage remains poorly understood. Whilst the beds of former ice sheets record numerous examples of channelized subglacial drainage systems, any influence these may have had upon ice sheet dynamics is difficult to decipher without contemporary analogues. Therefore, in order to understand the fates of past, present and future ice sheets, further study of contemporary subglacial hydraulic systems is required. Here, we present evidence from satellite imagery, digital elevation models and radio-echo sounding data for previously unknown channelized networks beneath Humboldt Glacier, northern Greenland. We find that two major channel networks exist beneath Humboldt Glacier: (i) a dendritic channel network to the north of the catchment, which extends for over >250 km beneath the ice sheet; and (ii) a series of linear channels in the south of the catchment, which are up to 80 km in length, 2.5 km wide and 400 m deep. These two morphologically contrasting systems likely have separate origins. We interpret the dendritic channel network to be of palaeofluvial origin, whilst the linear channels are likely to be subglacially formed tunnel valleys - analogous to those observed on former ice sheet beds. Radio-echo sounding indicates that basal meltwater is actively being routed along both systems. The dichotomy in subglacial drainage system origin corresponds to a division in ice flow regime, with faster flowing ice occurring over the palaeo-fluvial system. We therefore hypothesise that the large-scale bed channelization by subglacial meltwater erosion, which occurs beneath the slower flowing southern portion of Humboldt, results in a long-term reduction in basal water pressures and ice flow velocities.

  7. Analysis of recent glacial earthquakes in Greenland

    NASA Astrophysics Data System (ADS)

    Olsen, K.; Nettles, M.

    2015-12-01

    Large calving events at Greenland's outlet glaciers produce teleseismically detectable glacial earthquakes. These events are observed in the seismic record for the past 22 years, but the complete catalog of glacial earthquakes still numbers only ~300. The annual occurrence of these long-period events has increased over time, which makes recent years especially valuable in expanding the global dataset. Glacial earthquakes from 1993- 2010 have been analyzed systematically (Tsai and Ekström, 2007; Veitch and Nettles, 2012). Here, we analyze more recent events using the same centroid—single-force (CSF) approach as previous authors, focusing initially on data from 2013. In addition, we perform a focused study of selected events from 2009-2010 to assess the reliability of the force azimuths obtained from such inversions. Recent spatial and temporal patterns of glacial earthquakes in Greenland differ from those in previous years. In 2013, three times as many events occurred on the west coast as on the east, and these events originated predominantly from two glaciers: Jakobshavn Glacier on the west coast and Helheim Glacier on the east. Kangerdlugssuaq Glacier, on the east coast, produced no glacial earthquakes in 2013, though it produced many events in earlier years. Previous CSF results for glacial earthquakes show force azimuths perpendicular to the glacier front during a calving event, with force plunges near horizontal. However, some azimuths indicate forces initially oriented upglacier, while others are oriented downglacier (seaward). We perform a set of experiments on events from 2009 and 2010 and find two acceptable solutions for each glacial earthquake, oriented 180° apart with plunges of opposite sign and centroid times differing by approximately one half of the assumed duration of the earthquake time function. These results suggest the need for a more complex time function to model glacial earthquakes more accurately.

  8. Recent Changes in Arctic Glaciers, Ice Caps, and the Greenland Ice Sheet: Cold Facts About Warm Ice

    NASA Astrophysics Data System (ADS)

    Abdalati, W.

    2005-12-01

    One of the major manifestations of Arctic change can be observed in the state of balance of Arctic glaciers and ice caps and the Greenland ice sheet. These ice masses are estimated to contain nearly 3 million cubic kilometers of ice, which is more than six times greater than all the water stored in the Earth's lakes, rivers, and snow combined and is the equivalent of over 7 meters of sea level. Most of these ice masses have been shrinking in recent in years, but their mass balance is highly variable on a wide range of spatial and temporal scales. On the Greenland ice sheet most of the coastal regions have thinned substantially as melt has increased and some of its outlet glaciers have accelerated. Near the equilibrium line in West Greenland, we have seen evidence of summer acceleration that is linked to surface meltwater production, suggesting a relatively rapid response mechanism of the ice sheet change to a warming climate. At the same time, however, the vast interior regions of the Greenland ice sheet have shown little change or slight growth, as accumulation in these areas may have increased. Throughout much of the rest of the Arctic, many glaciers and ice caps have been shrinking in the past few decades, and in Canada and Alaska, the rate of ice loss seems to have accelerated during the late 1990s. These recent observations offer only a snapshot in time of the long-term behavior, but they are providing crucial information about the current state of ice mass balance and the mechanisms that control it in one of the most climatically sensitive regions on Earth. As we continue to learn more through a combination of remote sensing observations, in situ measurements and improved modeling capabilities, it is important that we coordinate and integrate these approaches effectively in order to predict future changes and their impact on sea level, freshwater discharge, and ocean circulation.

  9. Constraining calving front processes on W Greenland outlet glaciers using inertial-corrected laser scanning & swath-bathymetry

    NASA Astrophysics Data System (ADS)

    Bates, R.; Hubbard, A.; Neale, M.; Woodward, J.; Box, J. E.; Nick, F.

    2010-12-01

    Calving and submarine melt account for the majority of loss from the Antarctic and over 50% of that from the Greenland Ice Sheet. These ice-ocean processes are highly efficient mass-loss mechanisms, providing a rapid link between terrestrial ice (storage) and the oceanic sink (sea level/freshwater flux) which renders the ocean-outlet-ice sheet system potentially highly non-linear. Despite this, the controls on tidewater processes are poorly understood and a process based description of them is lacking from the present generation of coupled ice sheet models. We present details from an innovative study where two survey techniques are integrated to enable the construction of accurate, ~m resolution 3d digital terrain models (DTMs) of the aerial and submarine ice front of calving outlet glaciers. A 2km range terrestrial laser scanner was combined with a 416KHz swath-interferometric system and corrected via an inertial motion unit stabilized by RTK GPS and gyro-compass data. The system was mounted aboard a heavy displacement (20,000kg) yacht in addition to a light displacement (100kg) semi-autonomous boat and used to image the aerial and submarine calving fronts of two large outlet glaciers in W Greenland. Six daily surveys, each 2.5km long were repeated across Lille Glacier during which significant ice flow, melt and calving events were observed and captured from on-ice GPS stations and time-lapse sequences. A curtain of CTD and velocity casts were also conducted to constrain the fresh and oceanic mass and energy fluxes within the fjord. The residual of successive DTMs yield the spatial pattern of frontal change enabling the processes of aerial and submarine calving and melt to be quantified and constrained in unprecedented detail. These observed frontal changes are tentatively related to local dynamic, atmospheric and oceanographic processes that drive them. A partial survey of Store Glacier (~7km calving front & W Greenland 2nd largest outlet after Jakobshavn Isbrae

  10. Melting glaciers stimulate large summer phytoplankton blooms in southwest Greenland waters

    NASA Astrophysics Data System (ADS)

    Arrigo, Kevin R.; van Dijken, Gert L.; Castelao, Renato M.; Luo, Hao; Rennermalm, Ósa K.; Tedesco, Marco; Mote, Thomas L.; Oliver, Hilde; Yager, Patricia L.

    2017-06-01

    Each summer, large quantities of freshwater and associated dissolved and particulate material are released from the Greenland Ice Sheet (GrIS) into local fjords where they promote local phytoplankton growth. Whether the influx of freshwater and associated micronutrients in glacial meltwater is able to stimulate phytoplankton growth beyond the fjords is disputed, however. Here we show that the arrival of freshwater discharge from outlet glaciers from both southeast and southwest GrIS coincides with large-scale blooms in the Labrador Sea that extend over 300 km from the coast during summer. This summer bloom develops about a week after the arrival of glacial meltwater in early July and persists until the input of glacial meltwater slows in August or September, accounting for 40% of annual net primary production for the area. In view of the absence of a significant change in the depth of the mixed layer associated with the arrival of glacial meltwater to the Labrador Sea, we suggest that the increase in phytoplankton biomass and productivity in summer is likely driven by a greater nutrient supply (most likely iron). Our results highlight that the ecological impact of meltwater from the GrIS likely extends far beyond the boundaries of the local fjords, encompassing much of the eastern Labrador Sea. Such impacts may increase if melting of the GrIS accelerates as predicted.

  11. Observations and modeling of ocean-induced melt beneath Petermann Glacier Ice Shelf in northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Cai, Cilan; Rignot, Eric; Menemenlis, Dimitris; Nakayama, Yoshihiro

    2017-08-01

    We update observationally based estimates of subaqueous melt, Qm, beneath Petermann Glacier Ice Shelf (PGIS), Greenland, and model its sensitivity to oceanic thermal forcing, TF, and subglacial runoff, Qsg, using the Massachusetts Institute of Technology general circulation model (MITgcm), in a two-dimensional domain, with 20 m vertical and 40 m horizontal resolution at the grounding line. We adjust the drag coefficient to match the observationally based Qm. With the inclusion of Qsg, the maximum melt rate (Qmmax) is 2 times larger in summer and 1/3 larger annually than in winter. Qmmax increases above linear with TF and below linear with Qsg. We estimate that Qmmax increased by 24% (+8.1 m/yr) beneath PGIS from the 1990s to the 2000s from a 0.21°C warming in ocean temperature and a doubling in Qsg, hence contributing to its thinning. If the PGIS is removed, we estimate that the modeled melt rate near the grounding line will increase 13-16 times.

  12. Investigating near-glacier circulation and plume theory with high-resolution fjord surveys in West Greenland

    NASA Astrophysics Data System (ADS)

    Jackson, R. H.; Nash, J. D.; Shroyer, E.; Sutherland, D.; Fried, M.; Catania, G. A.; Carroll, D.; Bartholomaus, T. C.; Stearns, L. A.

    2016-12-01

    The plumes that emanate from Greenland's glaciers are hotspots of mixing between meltwater and ambient fjord waters. The dynamics of these plumes affect both submarine melting of glacier termini and the dilution of freshwater as it is exported into the ocean. Modeling studies often rely on buoyant plume theory to represent the circulation and mixing at the ocean/ice interface. However, a dearth of measurements in the near-glacier region has left open many questions about glacial plumes, entrainment, and the applicability of idealized plume theory to these environments. Here, we present near-glacier ocean surveys from Kangerdlugssuaq Sermerssua in central West Greenland in three consecutive summers (2013-2015). High-resolution measurements of velocity and water properties were collected by ship, by surface drifters, and by a remotely operated surface vessel - all focusing on the region within 2 km of the glacier terminus. These novel measurements of the 3D circulation capture a persistent near-surface plume, along with its time-evolution over a tidal cycle and between different summers. Concurrent multibeam sonar measurements of the submarine terminus morphology show that the plume emerges from a large undercut subglacial channel outlet. Plume theory, when applied with this fjord's stratification and any flux of subglacial discharge, cannot match the observed plume's volume flux and water properties. The discrepancy between our observations and plume theory suggests that there is enhanced entrainment at depth that is not adequately represented in plume theory. The details of this entrainment have important consequences for submarine melt rates, terminus morphology, and fjord circulation.

  13. A modeling study of the effect of runoff variability on the effective pressure beneath Russell Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Fleurian, Basile; Morlighem, Mathieu; Seroussi, Helene; Rignot, Eric; Broeke, Michiel R.; Kuipers Munneke, Peter; Mouginot, Jeremie; Smeets, Paul C. J. P.; Tedstone, Andrew J.

    2016-10-01

    Basal sliding is a main control on glacier flow primarily driven by water pressure at the glacier base. The ongoing increase in surface melting of the Greenland Ice Sheet warrants an examination of its impact on basal water pressure and in turn on basal sliding. Here we examine the case of Russell Glacier, in West Greenland, where an extensive set of observations has been collected. These observations suggest that the recent increase in melt has had an equivocal impact on the annual velocity, with stable flow on the lower part of the drainage basin but accelerated flow above the Equilibrium Line Altitude (ELA). These distinct behaviors have been attributed to different evolutions of the subglacial draining system during and after the melt season. Here we use a high-resolution subglacial hydrological model forced by reconstructed surface runoff for the period 2008 to 2012 to investigate the cause of these distinct behaviors. We find that the increase in meltwater production at low elevation yields a more efficient drainage system compatible with the observed stagnation of the mean annual flow below the ELA. At higher elevation, the model indicates that the drainage system is mostly inefficient and is therefore strongly sensitive to an increase in meltwater availability, which is consistent with the observed increase in ice velocity.

  14. A plastic network approach to model calving glacier advance and retreat

    NASA Astrophysics Data System (ADS)

    Ultee, Lizz; Bassis, Jeremy N.

    2017-03-01

    Calving glaciers contribute substantially to sea level rise, but they are challenging to represent in models. Fine resolution is required for continental-scale models to accurately resolve calving dynamics and in many cases glacier geometry is too complicated to be adequately reflected by more simplified models. Flowline models are able to resolve flow along the main branch of a glacier, but many of those in current use either ignore tributaries entirely or parameterize their effect using a measure of “equivalent width”. Here we present a simple method to simulate terminus advance and retreat for an interacting network of glacier branches, based on a model extending Nye’s 1953 perfect plastic flow approximation to calving glaciers. We apply the method to case studies of four marine-terminating glaciers: Jakobshavn Isbræ and Helheim Glacier of Greenland, and Columbia and Hubbard Glaciers of Alaska. Given bed topography and upstream elevation history, our method reproduces observed patterns of terminus advance and retreat in all cases, as well as centerline profiles for all branches.

  15. An Empirical Approach for Estimating Stress-Coupling Lengths for Marine-Terminating Glaciers

    NASA Astrophysics Data System (ADS)

    Enderlin, Ellyn; Hamilton, Gordon; O'Neel, Shad; Bartholomaus, Timothy; Morlighem, Mathieu; Holt, John

    2016-12-01

    Variability in the dynamic behavior of marine-terminating glaciers is poorly understood, despite an increase in the abundance and resolution of observations. When paired with ice thicknesses, surface velocities can be used to quantify the dynamic redistribution of stresses in response to environmental perturbations through computation of the glacier force balance. However, because the force balance is not purely local, force balance calculations must be performed at the spatial scale over which stresses are transferred within glacier ice, or the stress-coupling length (SCL). Here we present a new empirical method to estimate the SCL for marine-terminating glaciers using high-resolution observations. We use the empirically-determined periodicity in resistive stress oscillations as a proxy for the SCL. Application of our empirical method to two well-studied tidewater glaciers (Helheim Glacier, SE Greenland, and Columbia Glacier, Alaska, USA) demonstrates that SCL estimates obtained using this approach are consistent with theory (i.e., can be parameterized as a function of the ice thickness) and with prior, independent SCL estimates. In order to accurately resolve stress variations, we suggest that similar empirical stress-coupling parameterizations be employed in future analyses of glacier dynamics.

  16. Reverse glacier motion during iceberg calving and the cause of glacial earthquakes

    NASA Astrophysics Data System (ADS)

    Murray, T.; Nettles, M.; Selmes, N.; Cathles, M.; Burton, J. C.; James, T.; Edwards, S.; Martin, I.; O'Farrell, T.; Aspey, R. A.; Rutt, I. C.; Bauge, T.

    2015-12-01

    About half Greenland's mass loss results from iceberg calving, but the physical mechanisms of calving are poorly known and in situobservations are sparse. Glacial earthquakes, globally detectable seismic events, are associated with calving and are occurring at increasing numbers of outlet glaciers in Greenland and Antarctica. However, the processes causing them have not been clear. We installed a wireless network of on-ice GPS sensors at the calving margin of Helheim Glacier for 55 days during summer 2013. The glacier is a major SE Greenland tidewater outlet and during our observations retreated ~1.5 km in a series of calving events. Our GPS sensors captured glacier motion with cm-level accuracy at locations very close to the calving front with a high temporal sampling rate. Calving causes a minutes-long reversal of the glacier's horizontal flow and a downward deflection of its terminus seen on multiple GPS sensors. Each major calving event is associated with a glacial earthquake. For example, a glacial earthquake / calving event on day 206 produced an iceberg of volume 0.36 km3and aspect ratio 0.23. A GPS sensor close to the front showed a pre-earthquake speed of 29 m/day. Immediately prior to the earthquake centroid time, the sensor reversed its direction and moved upglacier at ~40 m/day and downward 10 cm. The reversed motion was sustained for ~200 s and was followed by downglacier rebound and upward movement. The reverse motion of the glacier results from the horizontal force caused by iceberg capsize and acceleration away from the front. We use analog laboratory experiments to demonstrate that the downward motion results from hydrodynamic pressure drop behind the capsizing berg, which also causes an upward force on the solid Earth. We show that these horizontal and vertical forces are the source of glacial earthquakes. Proper interpretation of the earthquake events should allow remote sensing of calving processes at the margins of Greenland and Antarctic

  17. 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

  18. The Subglacial Access and Fast Ice Research Experiment (SAFIRE): 1. Programme of investigation on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Christoffersen, Poul; Hubbard, Bryn; Bougamont, Marion; Doyle, Samuel; Young, Tun Jan; Hofstede, Coen; Nicholls, Keith; Todd, Joe; Box, Jason; Ryan, Johnny; Toberg, Nick; Walter, Jacob; Hubbard, Alun

    2015-04-01

    Marine-terminating outlet glaciers drain 90 percent of the Greenland Ice Sheet and are responsible for about half of the ice sheet's net annual mass loss, which currently raises global sea level by almost 1 mm per year. Understanding the processes that drive the fast flow of these glaciers is crucial because a growing body of evidence points to a strong, but spatially varied and often complex, response to oceanographic as well as atmospheric forcing. While the bed of glaciers elsewhere is known to strongly influence the flow of ice, no observations have ever been made at the bed of a marine-terminating glacier in Greenland. The flow of ice in numerical models of the Greenland Ice Sheet consequently rely on untested basal parameterisations, which form a likely and potentially significant source of error in the prediction of sea level rise over the coming decades and century. The Subglacial Access and Fast Ice Research Experiment (SAFIRE) is addressing this paucity of observational constraints by gaining access to the bed of Store Glacier, a marine-terminating outlet of the Greenland Ice Sheet which has a drainage basin of 35,000 square kilometres and terminates in Uummannaq Fjord. In 2014, the SAFIRE programme drilled four boreholes in a region where ice flows at a rate of 700 m per year and where a seismic survey revealed a bed consisting of soft sediment. (See joint abstract by Hofstede et al. for details.) The boreholes were 603-616 m deep and direct access to the bed was confirmed by a clear hydrological connectivity with a basal water system. (See joint abstract by Doyle et al. for details.) With sensors deployed englacially (temperature and tilt) and at the bed (water pressure, turbidity, electrical conductivity), the SAFIRE will inform the ratio of internal ice deformation and basal slip, vertical strain, ice temperature, and fluctuations in water pressure linked to supraglacial lake drainage as well as diurnal drainage into moulins. In 2015, we plan to

  19. Preliminary results from hot-water drilling and borehole instrumentation on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Doyle, S. H.; Christoffersen, P.; Hubbard, B. P.; Young, T. J.; Hofstede, C. M.; Box, J.; Todd, J.; Bougamont, M. H.; Hubbard, A.

    2015-12-01

    As part of the Subglacial Access and Fast Ice Research Experiment (SAFIRE) pressurised hot water was used to drill four 603-616 m-long boreholes to the bed of the Greenland Ice Sheet at a site located 30 km from the calving front of fast-flowing, marine-terminating Store Glacier (70° N, ~1000 m elevation). Despite the boreholes freezing within hours, 4 wired sensor strings were successfully deployed in three of the boreholes. These included a thermistor string to obtain the englacial temperature profile installed in the same borehole as a string of tilt sensors to measure borehole deformation, and two sets of water pressure, electrical conductivity and turbidity sensors installed just above the bed in separate, adjacent boreholes. The boreholes made a strong hydrological connection to the bed during drilling, draining rapidly to ~80 m below the ice surface. The connection of subsequent boreholes was observed as a perturbation in water pressure and temperature recorded in neighbouring boreholes, indicating an effective hydrological sub- or en-glacial connection between them. The sensors, which were all connected to loggers at the surface by cables, operated for between ~30 and 80+ days before indications suggest that the cables stretched and then snapped - with the lowermost sensors failing first. The records obtained from these sensors reveal (i) high and increasing water pressure varying diurnally close to overburden albeit of a small magnitude (~ 0.3 m H2O), (ii) a minimum extrapolated englacial temperature of -21°C with above-freezing temperatures at the bed, and (iv) high rates of internal deformation and strain increasing towards the bed as evinced by increasing tilt with depth. These borehole observations are complemented by GPS measurements of ice motion, meteorological data, and seismic and radar surveys.

  20. Greenland snow accumulation rates estimated by the retracking of percolation facies from airborne radar

    NASA Astrophysics Data System (ADS)

    de la Pena, S.; Howat, I. M.

    2012-12-01

    The margins of the Greenland Ice Sheet are experiencing substantial thinning due to warming in the arctic regions, and there is a growing concern about the effects that mass imbalance of the ice sheet could have on climate and sea level rise. Although volume changes of the ice sheet may be inferred by remote sensing methods, mass gain and accumulation fluctuations are not easily distinguished and are poorly resolved. Recent advances in airborne radar techniques have resulted in systems capable of resolving snow accumulation by retracking internal layers formed by refreezing of surface meltwater that percolates through the snowpack, a phenomenon increasingly common in Greenland. We present accumulation rates for the catchment areas of the Jakobshavn, Helheim, and Rusell glaciers derived from snow depth resolved by snow and Ku-band airborne radar, flown as part of NASA's Operation IceBridge.

  1. Greenland Ice Sheet glacier motion and ice loss: New understanding of ice sheet behavior through remote sensing

    NASA Astrophysics Data System (ADS)

    Moon, T. A.; Fahnestock, M. A.; Scambos, T.; Joughin, I.

    2015-12-01

    Ice loss from the Greenland Ice Sheet makes up roughly a third of current sea level rise, also generating substantial local and regional freshwater fluxes. Containing more than 6 meters of sea level rise equivalent in ice, Greenland has the potential to contribute much more to rising ocean levels and freshening water in the future. Understanding the dynamics of the ice sheet, particularly the behavior of fast flowing coastal outlet glaciers, is critical to improving predictions of future ice sheet change and associated impacts. Combining velocity, glacier ice front, sea ice, and ice sheet surface melt data, we made several important advances in characterizing and understanding seasonal glacier behavior and the processes driving change: 1) seasonal velocity patterns fall into at least 3 distinct patterns, 2) these seasonal velocity patterns likely indicate differences in glacier responsiveness to ocean versus subglacial hydrologic processes, and 3) in some regions seasonal versus multi-year velocity changes appear most strongly influenced by different environmental factors. Further progress was previously hampered by limits in measurement resolution across space and time. To address this challenge, we are creating a new - and continuously growing - ice velocity dataset from Landsat 8 imagery. This data stream supports comprehensive global measurements of ice flow, providing a leap in our understanding of ice sheet motion across space and time. We offer a high-level discussion of our research findings and an introduction to the new Landsat 8-enabled data stream. Our results and measurement capabilities deliver critical new knowledge about ice sheet behavior and interaction with ocean and climate factors. These advances, in turn, have important implications for other elements of Earth system research, including climate, oceanography, and biology.

  2. IceBridge Provides Novel Evidence for Thick Units of Basal Freeze-on Ice Along Petermann Glacier, Greenland

    NASA Astrophysics Data System (ADS)

    Bell, R. E.; Tinto, K. J.; Wolovick, M.; Block, A. E.; Frearson, N.; Das, I.; Abdi, A.; Creyts, T. T.; Cochran, J. R.; Csatho, B. M.; Babonis, G. S.

    2011-12-01

    The Petermann Glacier, one of the major outlet glaciers in Greenland, drains six percent of the Greenland ice from a basin largely below sea level. Petermann Glacier and its large ice shelf may be susceptible to increased change as the waters along the Greenland margin warm. The 2010 and 2011 Operation IceBridge mission, acquired a comprehensive aerogeophysical data set over the Petermann Glacier that provides insights into the ice sheet structure. This analysis employs most of the data streams acquired by the Icebridge platform including ice-penetrating radar, laser altimetry, gravity and magnetics. An orthogonal 10 km grid extends from 60 km upstream of the grounding line to 240 km inland. The ice velocities in the region range from <50m/yr to >200m/yr. On the interior lines the internal layers are pulled down over 2-3 km wide regions. Up to 400m of ice from the base of the ice sheet appears to be absent in these regions. We interpret these pulled down regions as basal melt. These melt regions are mainly located along the upstream side of a 80 km wide east-west trending topographic ridge that separates the interior ice from the Petermann Fjord. The IceBridge magnetic data indicates that this broad flat ridge is the boundary between the Franklinian Basins and the Ellsmerian Foldbelt to the north. Downstream of these pull-down layers we have identified 4 distinct packages of ice that thicken downstream and are characterized by a strong upper reflector. These packages develop at the base of the ice sheet and reach thicknesses of 500-700m over distances of 10-20 km. These basal packages can be traced for 30-100 km following the direction of flow, and may be present close to the grounding line. These basal reflectors deflect the overlying internal layers upward indicating the addition of ice to the base of the ice sheet. The IceBridge gravity data indicates that these features are probably not off-nadir topography since these would show up as around 30mGal anomalies

  3. Committed sea-level rise for the next century from Greenland ice sheet dynamics during the past decade.

    PubMed

    Price, Stephen F; Payne, Antony J; Howat, Ian M; Smith, Benjamin E

    2011-05-31

    We use a three-dimensional, higher-order ice flow model and a realistic initial condition to simulate dynamic perturbations to the Greenland ice sheet during the last decade and to assess their contribution to sea level by 2100. Starting from our initial condition, we apply a time series of observationally constrained dynamic perturbations at the marine termini of Greenland's three largest outlet glaciers, Jakobshavn Isbræ, Helheim Glacier, and Kangerdlugssuaq Glacier. The initial and long-term diffusive thinning within each glacier catchment is then integrated spatially and temporally to calculate a minimum sea-level contribution of approximately 1 ± 0.4 mm from these three glaciers by 2100. Based on scaling arguments, we extend our modeling to all of Greenland and estimate a minimum dynamic sea-level contribution of approximately 6 ± 2 mm by 2100. This estimate of committed sea-level rise is a minimum because it ignores mass loss due to future changes in ice sheet dynamics or surface mass balance. Importantly, > 75% of this value is from the long-term, diffusive response of the ice sheet, suggesting that the majority of sea-level rise from Greenland dynamics during the past decade is yet to come. Assuming similar and recurring forcing in future decades and a self-similar ice dynamical response, we estimate an upper bound of 45 mm of sea-level rise from Greenland dynamics by 2100. These estimates are constrained by recent observations of dynamic mass loss in Greenland and by realistic model behavior that accounts for both the long-term cumulative mass loss and its decay following episodic boundary forcing.

  4. Elevation Change of Greenland's Jakobshavn Glacier from ICESat, IceBridge Altimetry and TerraSAR-X DEMs

    NASA Astrophysics Data System (ADS)

    Qi, W.; Braun, A.

    2012-12-01

    The recent accelerated ice mass loss of the Greenland ice sheet, and its outlet glacier in particular, has been widely documented. The Jakobshavn Isbrae/Glacier is one of the fastest melting and retreating glaciers in Greenland. Recent observations from the laser altimetry mission ICESat (2003-2009) and the airborne campaigns of the IceBridge project (2009-2011) were used to determine Jakobshavn's total elevation change for those time periods as well as annual elevation change rates. TerraSAR-X data acquired in 2009 were processed to form 3 m horizontal resolution digital elevation models (DEM), which were constrained using ICESat measurements. The elevation change results confirm previously determined rates of several decimeters per year of elevation loss. More specifically, while the outlet glacier shows elevation loss of up to several meters per year, the higher elevation areas of the ice sheet exhibit only a few decimeters per year loss and even elevation gain for some years. The study area below 1500 m elevation shows elevation change rates between -0.5 to -2.5 m/yr, the higher elevation area exhibits a much decreased rate between +0.34 and -0.55 m/yr. The Jakobshavn outlet glacier showed a consistently increasing elevation change rate of -3.0 to -5.0 m/yr between 2003 and 2011. It demonstrates that both ICESat and IceBridge observations allow for the accurate estimation of elevation change rates with uncertainties of less than 0.5 m/yr standard deviation. The major contributor to the uncertainty is the slope correction needed to project two footprints at different epochs onto a common location. The slope correction was applied based on the DEMs from ICESat and TerraSAR-X data or the IceBridge slope measurements. Both ICESat and IceBridge observations are able to demonstrate the variations in annual and seasonal elevation change rates exceeding 0.5 m/yr, a rate which is by far exceeded for low-elevation areas below 1500 m. By having an improved understanding

  5. Automated Ground-based Time-lapse Camera Monitoring of West Greenland ice sheet outlet Glaciers: Challenges and Solutions

    NASA Astrophysics Data System (ADS)

    Ahn, Y.; Box, J. E.; Balog, J.; Lewinter, A.

    2008-12-01

    Monitoring Greenland outlet glaciers using remotely sensed data has drawn a great attention in earth science communities for decades and time series analysis of sensory data has provided important variability information of glacier flow by detecting speed and thickness changes, tracking features and acquiring model input. Thanks to advancements of commercial digital camera technology and increased solid state storage, we activated automatic ground-based time-lapse camera stations with high spatial/temporal resolution in west Greenland outlet and collected one-hour interval data continuous for more than one year at some but not all sites. We believe that important information of ice dynamics are contained in these data and that terrestrial mono-/stereo-photogrammetry can provide theoretical/practical fundamentals in data processing along with digital image processing techniques. Time-lapse images over periods in west Greenland indicate various phenomenon. Problematic is rain, snow, fog, shadows, freezing of water on camera enclosure window, image over-exposure, camera motion, sensor platform drift, and fox chewing of instrument cables, and the pecking of plastic window by ravens. Other problems include: feature identification, camera orientation, image registration, feature matching in image pairs, and feature tracking. Another obstacle is that non-metric digital camera contains large distortion to be compensated for precise photogrammetric use. Further, a massive number of images need to be processed in a way that is sufficiently computationally efficient. We meet these challenges by 1) identifying problems in possible photogrammetric processes, 2) categorizing them based on feasibility, and 3) clarifying limitation and alternatives, while emphasizing displacement computation and analyzing regional/temporal variability. We experiment with mono and stereo photogrammetric techniques in the aide of automatic correlation matching for efficiently handling the enormous

  6. Mass loss of Greenland's glaciers and ice caps 2003-2008 revealed from ICESat laser altimetry data

    NASA Astrophysics Data System (ADS)

    Bolch, T.; Sandberg SøRensen, L.; Simonsen, S. B.; MöLg, N.; Machguth, H.; Rastner, P.; Paul, F.

    2013-03-01

    The recently finalized inventory of Greenland's glaciers and ice caps (GIC) allows for the first time to determine the mass changes of the GIC separately from the ice sheet using space-borne laser altimetry data. Corrections for firn compaction and density that are based on climatic conditions are applied for the conversion from volume to mass changes. The GIC which are clearly separable from the icesheet (i.e., have a distinct ice divide or no connection) lost 27.9 ± 10.7 Gt a-1 or 0.08 ± 0.03 mm a-1 sea-level equivalent (SLE) between October 2003 and March 2008. All GIC (including those with strong but hydrologically separable connections) lost 40.9 ± 16.5 Gt a-1 (0.12 ± 0.05 mm a-1 SLE). This is a significant fraction (~14 or 20%) of the reported overall mass loss of Greenland and up to 10% of the estimated contribution from the world's GIC to sea level rise. The loss was highest in southeastern and lowest in northern Greenland.

  7. A predictive model for routing of supraglacial meltwater to the bed of glaciers: application to Leverett Glacier, western Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Clason, Caroline; Mair, Douglas; Nienow, Peter

    2010-05-01

    Recent studies have shown that Greenland outlet glacier velocities may be responding to increased meltwater generation (Shepherd et al, 2009; Zwally et al, 2002). Where sufficient supraglacial meltwater is routed into crevasses and moulins it could act to lubricate the bed, resulting in dynamic thinning and accelerated transfer of ice mass to glacier termini. The extent to which this mechanism contributes to mass loss is largely unknown, but may be increasingly important if current trends of warming are to continue, particularly in high northerly latitudes. This study introduces a modelling routine for prediction of moulin formation and quantification of meltwater delivery to the bed from digital elevation models, ice surface velocity data and meteorological input data. Supraglacial meltwater pathways are predicted from ice surface topography using a single flow direction hydrological flow routing algorithm. A temperature-index model driven by measured air temperature is used to produce values of distributed ice surface melt, integrated within stream accumulation to produce estimates of supraglacial stream discharge throughout the predicted network. Ice surface strain rates are calculated from satellite-derived surface velocities acquired using feature tracking. Strain rates are converted to stresses through the constitutive relation for glacier ice, after Nye (1957). Surface tensile stresses are calculated from the resultant principal stresses using the Von Mises criteria for failure of ductile materials, with areas of crevassing predicted where tensile stresses exceed a prescribed value of fracture toughness. Where supraglacial streams and areas of crevassing intersect, surficial moulin locations are predicted. A simple model for propagation of water-filled crevasses is applied to determine where moulins will penetrate through the full ice thickness, delivering meltwater to the bed. Derived from linear elastic fracture mechanics, the model calculates crevasse

  8. Modeling of ocean-induced ice melt rates of five west Greenland glaciers over the past two decades

    NASA Astrophysics Data System (ADS)

    Rignot, E.; Xu, Y.; Menemenlis, D.; Mouginot, J.; Scheuchl, B.; Li, X.; Morlighem, M.; Seroussi, H.; den Broeke, M. van; Fenty, I.; Cai, C.; An, L.; Fleurian, B. de

    2016-06-01

    High-resolution, three-dimensional simulations from the Massachusetts Institute of Technology general circulation model ocean model are used to calculate the subaqueous melt rate of the calving faces of Umiamako, Rinks, Kangerdlugssup, Store, and Kangilerngata glaciers, west Greenland, from 1992 to 2015. Model forcing is from monthly reconstructions of ocean state and ice sheet runoff. Results are analyzed in combination with observations of bathymetry, bed elevation, ice front retreat, and glacier speed. We calculate that subaqueous melt rates are 2-3 times larger in summer compared to winter and doubled in magnitude since the 1990s due to enhanced subglacial runoff and 1.6 ± 0.3°C warmer ocean temperature. Umiamako and Kangilerngata retreated rapidly in the 2000s when subaqueous melt rates exceeded the calving rates and ice front retreated to deeper bed elevation. In contrast, Store, Kangerdlugssup, and Rinks have remained stable because their subaqueous melt rates are 3-4 times lower than their calving rates, i.e., the glaciers are dominated by calving processes.

  9. Spring bloom dynamics in a subarctic fjord influenced by tidewater outlet glaciers (Godthåbsfjord, SW Greenland)

    NASA Astrophysics Data System (ADS)

    Meire, Lorenz; Mortensen, John; Rysgaard, Søren; Bendtsen, Jørgen; Boone, Wieter; Meire, Patrick; Meysman, Filip J. R.

    2016-06-01

    In high-latitude fjord ecosystems, the spring bloom accounts for a major part of the annual primary production and thus provides a crucial energy supply to the marine food web. However, the environmental factors that control the timing and intensity of these spring blooms remain uncertain. In 2013, we studied the spring bloom dynamics in Godthåbsfjord, a large fjord system adjacent to the Greenland Ice Sheet. Our surveys revealed that the spring bloom did not initiate in the inner stratified part of the fjord system but only started farther away from tidewater outlet glaciers. A combination of out-fjord winds and coastal inflows drove an upwelling in the inner part of the fjord during spring (April-May), which supplied nutrient-rich water to the surface layer. This surface water was subsequently transported out-fjord, and due to this circulation regime, the biomass accumulation of phytoplankton was displaced away from the glaciers. In late May, the upwelling weakened and the dominant wind direction changed, thus reversing the direction of the surface water transport. Warmer water was now transported toward the inner fjord, and a bloom was observed close to the glacier terminus. Overall, our findings imply that the timing, intensity, and location of the spring blooms in Godthåbsfjord are controlled by a combination of upwelling strength and wind forcing. Together with sea ice cover, the hydrodynamic regime hence plays a crucial role in structuring food web dynamics of the fjord ecosystem.

  10. Committed sea-level rise for the next century from Greenland ice sheet dynamics during the past decade

    PubMed Central

    Price, Stephen F.; Payne, Antony J.; Howat, Ian M.; Smith, Benjamin E.

    2011-01-01

    We use a three-dimensional, higher-order ice flow model and a realistic initial condition to simulate dynamic perturbations to the Greenland ice sheet during the last decade and to assess their contribution to sea level by 2100. Starting from our initial condition, we apply a time series of observationally constrained dynamic perturbations at the marine termini of Greenland’s three largest outlet glaciers, Jakobshavn Isbræ, Helheim Glacier, and Kangerdlugssuaq Glacier. The initial and long-term diffusive thinning within each glacier catchment is then integrated spatially and temporally to calculate a minimum sea-level contribution of approximately 1 ± 0.4 mm from these three glaciers by 2100. Based on scaling arguments, we extend our modeling to all of Greenland and estimate a minimum dynamic sea-level contribution of approximately 6 ± 2 mm by 2100. This estimate of committed sea-level rise is a minimum because it ignores mass loss due to future changes in ice sheet dynamics or surface mass balance. Importantly, > 75% of this value is from the long-term, diffusive response of the ice sheet, suggesting that the majority of sea-level rise from Greenland dynamics during the past decade is yet to come. Assuming similar and recurring forcing in future decades and a self-similar ice dynamical response, we estimate an upper bound of 45 mm of sea-level rise from Greenland dynamics by 2100. These estimates are constrained by recent observations of dynamic mass loss in Greenland and by realistic model behavior that accounts for both the long-term cumulative mass loss and its decay following episodic boundary forcing. PMID:21576500

  11. A statistical-dynamical approach to represent Greenland ocean-ice sheet interactions

    NASA Astrophysics Data System (ADS)

    Perrette, Mahé; Calov, Reinhard; Ganopolski, Andrey; Robinson, Alex

    2013-04-01

    An understanding of the dynamics of the Greenland ice sheet is fundamental, because of its potential to contribute strongly to future sea level rise. In recent years there has been a discussion about the role of the ocean in the Greenland ice sheet's present and future mass balance. The ocean interacts with the ice sheet's outlet glaciers via the water circulation in the fjords and considerably affects melting at the termini of the outlet glaciers. Processes related to this interaction are difficult to represent in Greenland-wide ice-sheet models because grid resolution of such models is typically 10 km, whereas large fjords are more commonly only 1 to 5 km wide. Local refinement techniques (e.g. finite elements with adaptive mesh) can be a way of addressing that problem but are still computationally expensive to run. Here we propose a simpler, statistical-dynamical approach suited for large ensemble simulations over 100- to 1000-year integration times, in the EMIC spirit: the fjord-outlet glacier system is restricted to its most fundamental dynamics, controlled by a handful of parameters describing the major characteristics of the system. The model has a generic structure, i.e., it is designed such that it applies to every Greenland outlet glacier. Some of its parameters are fixed by using the (little) available observational data - e.g. for Helheim, Kangerdlugssuaq and Jakobshavn Isbrae - other parameters may vary depending on location. It is not our aim to simulate every single small outlet glacier in its full accuracy; but we aim to represent, on average, important characteristics like ice discharge and general advance/retreat rate on a regional scale over major catchment areas. Aspects of the coupling strategy with the 3D ice-sheet model (SICOPOLIS) are discussed, e.g., critical issues such as the treatment of mass balance. Preliminary design and results will be presented.

  12. Glaciers

    NASA Astrophysics Data System (ADS)

    Hambrey, Michael; Alean, Jürg

    2004-12-01

    Glaciers are among the most beautiful natural wonders on Earth, as well as the least known and understood, for most of us. Michael Hambrey describes how glaciers grow and decay, move and influence human civilization. Currently covering a tenth of the Earth's surface, glacier ice has shaped the landscape over millions of years by scouring away rocks and transporting and depositing debris far from its source. Glacier meltwater drives turbines and irrigates deserts, and yields mineral-rich soils as well as a wealth of valuable sand and gravel. However, glaciers also threaten human property and life. Our future is indirectly connected with the fate of glaciers and their influence on global climate and sea level. Including over 200 stunning photographs, the book takes the reader from the High-Arctic through North America, Europe, Asia, Africa, New Zealand and South America to the Antarctic. Michael Hambrey is Director of the Centre for Glaciology at the University of Wales, Aberystwyth. A past recipient of the Polar Medal, he was also given the Earth Science Editors' Outstanding Publication Award for the first edition of Glaciers (Cambridge, 1995). Hambrey is also the author of Glacial Environments (British Columbia, 1994). JÜrg Alean is Professor of Geography at the Kantonsschule ZÜrcher Unterland in BÜlach, Switzerland.

  13. A Mini-Surge on theRyder Glacier, Greenland Observed via Satelite Radar Interferometry

    NASA Technical Reports Server (NTRS)

    Joughin, I.; Tulaczyk, S.; Fahnestock, M.; Kwok, R.

    1996-01-01

    A dramatic short term speed up of the Ryder glacier has been detected using satellite radar interferometry. The accelerated flow represents a substantial, though short-lived, change in the ice discharge from this basin. We believe that meltwater was involved in this event, either as an active participant, as meltwater-filled lakes on the surface of the glacier drained during the period of rapid motion.

  14. A Mini-Surge on theRyder Glacier, Greenland Observed via Satelite Radar Interferometry

    NASA Technical Reports Server (NTRS)

    Joughin, I.; Tulaczyk, S.; Fahnestock, M.; Kwok, R.

    1996-01-01

    A dramatic short term speed up of the Ryder glacier has been detected using satellite radar interferometry. The accelerated flow represents a substantial, though short-lived, change in the ice discharge from this basin. We believe that meltwater was involved in this event, either as an active participant, as meltwater-filled lakes on the surface of the glacier drained during the period of rapid motion.

  15. A High-Resolution Sensor Network for Monitoring Glacier Dynamics

    NASA Astrophysics Data System (ADS)

    Edwards, S.; Murray, T.; O'Farrell, T.; Rutt, I. C.; Loskot, P.; Martin, I.; Selmes, N.; Aspey, R.; James, T.; Bevan, S. L.; Baugé, T.

    2013-12-01

    Changes in Greenland and Antarctic ice sheets due to ice flow/ice-berg calving are a major uncertainty affecting sea-level rise forecasts. Latterly GNSS (Global Navigation Satellite Systems) have been employed extensively to monitor such glacier dynamics. Until recently however, the favoured methodology has been to deploy sensors onto the glacier surface, collect data for a period of time, then retrieve and download the sensors. This approach works well in less dynamic environments where the risk of sensor loss is low. In more extreme environments e.g. approaching the glacial calving front, the risk of sensor loss and hence data loss increases dramatically. In order to provide glaciologists with new insights into flow dynamics and calving processes we have developed a novel sensor network to increase the robustness of data capture. We present details of the technological requirements for an in-situ Zigbee wireless streaming network infrastructure supporting instantaneous data acquisition from high resolution GNSS sensors thereby increasing data capture robustness. The data obtained offers new opportunities to investigate the interdependence of mass flow, uplift, velocity and geometry and the network architecture has been specifically designed for deployment by helicopter close to the calving front to yield unprecedented detailed information. Following successful field trials of a pilot three node network during 2012, a larger 20 node network was deployed on the fast-flowing Helheim glacier, south-east Greenland over the summer months of 2013. The utilisation of dual wireless transceivers in each glacier node, multiple frequencies and four ';collector' stations located on the valley sides creates overlapping networks providing enhanced capacity, diversity and redundancy of data 'back-haul', even close to ';floor' RSSI (Received Signal Strength Indication) levels around -100 dBm. Data loss through radio packet collisions within sub-networks are avoided through the

  16. Meltwater pathways from marine terminating glaciers of the Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Gillard, Laura C.; Hu, Xianmin; Myers, Paul G.; Bamber, Jonathan L.

    2016-10-01

    The Greenland ice sheet (GrIS) stores the largest amount of freshwater in the Northern Hemisphere and has been recently losing mass at an increasing rate. An eddy-permitting ocean general circulation model is forced with realistic estimates of freshwater flux from the GrIS. Two approaches are used to track the meltwater and its trajectory in the ocean. We show that freshwater from western and eastern GrIS have markedly different fates, on a decadal time scale. Freshwater from west Greenland predominantly accumulates in Baffin Bay before being exported south down the Labrador shelf. Meanwhile, GrIS freshwater entering the interior of the Labrador Sea, where deep convection occurs, comes predominantly (˜80%) from east Greenland. Therefore, hosing experiments, which generally assume a uniform freshwater flux spatially, will not capture the true hydrographic response and regional impacts. In addition, narrow boundary currents are important for freshwater transport and distribution, requiring simulations with eddy-resolving resolution.

  17. Of Images, Archives, and Anonymity: Glacier Photographs from Louise Arner Boyd's East Greenland Expeditions, 1933, 1937, and 1938

    NASA Astrophysics Data System (ADS)

    Nelson, F. E.; Peschel, S. M.; Hall, D. K.

    2010-12-01

    Louise A. Boyd (1887-1972) was raised to wealth and privilege in San Raphael, CA. Her inherited fortune allowed unlimited travel, and in 1924 she arrived in Spitsbergen as a tourist. Infatuated by Arctic landscapes, Boyd resolved to return north in a more assertive role and ran three "preliminary" expeditions to Greenland, in 1926, 1928, and 1931. Boyd’s expeditions to East Greenland in 1933, 1937, and 1938 were predictive of the type of campaign that after WWII would characterize government-sponsored and international scientific efforts. “Planned as a unit,” these campaigns, sponsored by the American Geographical Society (AGS), were thoroughly integrated scientific expeditions incorporating glaciology, periglacial and glacial geomorphology, bedrock geology, botany, hydrography, topographic surveys, tides and currents, and magnetic observations within representative areas. The goal of the expeditions was to provide comprehensive characterization of the physical environment. The volumes resulting from this work contain many large-scale hydrographic and topographic maps, photomosaics, glacier maps, and chapters on the geology, glacial history, botany, and hydrology of the region. Boyd received extensive publicity for her Arctic expeditions, although much of it was concerned with the novelty of expeditions to remote locations being led by a woman. Boyd’s expeditions employed scientists who eventually became highly influential in their respective fields. Boyd employed, among others, the earth scientists J.H. Bretz, R.F. Flint, and A.L. Washburn. Other important personnel on these expeditions included AGS cartographer/surveyor O.M. Miller and his assistant, W.A. Wood, who employed novel ground-based photogrammetric techniques to construct a series of glacier maps at scales as large as 1:5000. The maps featured detailed error analyses, and are probably the first large-scale maps of known accuracy to be made of the Greenland Ice Sheet’s outlet glaciers. Boyd

  18. Microbial community variation in cryoconite granules on Qaanaaq Glacier, NW Greenland.

    PubMed

    Uetake, Jun; Tanaka, Sota; Segawa, Takahiro; Takeuchi, Nozomu; Nagatsuka, Naoko; Motoyama, Hideaki; Aoki, Teruo

    2016-09-01

    Cryoconite granules are aggregations of microorganisms with mineral particles that form on glacier surfaces. To understand the processes by which the granules develop, this study focused on the altitudinal distribution of the granules and photosynthetic microorganisms on the glacier, bacterial community variation with granules size and environmental factors affecting the growth of the granules. Size-sorted cryoconite granules collected from five different sites on Qaanaaq Glacier were analyzed. C and N contents were significantly higher in large (diameter greater than 250 μm) granules than in smaller (diameter 30-249 μm) granules. Bacterial community structures, based on 16S rRNA gene amplicon sequencing, were different between the smaller and larger granules. The filamentous cyanobacterium Phormidesmis priestleyi was the dominant bacterial species in larger granules. Multivariate analysis suggests that the abundance of mineral particles on the glacier surface is the main factor controlling growth of these cyanobacteria. These results show that the supply of mineral particles on the glacier enhances granule development, that P. priestleyi is likely the key species for primary production and the formation of the granules and that the bacterial community in the granules changes over the course of the granule development.

  19. Jakobshavn Glacier

    Atmospheric Science Data Center

    2013-04-17

    article title:  Greenland's Coast in Holiday Colors     ... blues adorn this view of the area surrounding the Jakobshavn Glacier on the western coast of Greenland. The image is a false-color (near-infrared, green, blue) view ...

  20. Calculating Freshwater Input from Iceberg Melt in Greenlandic Fjords by Combining In Situ Observations of Iceberg Movement with High Resolution Satellite Imagery

    NASA Astrophysics Data System (ADS)

    Sulak, D. J.; Sutherland, D.; Stearns, L. A.; Hamilton, G. S.

    2015-12-01

    Understanding fjord circulation in Greenland's outlet glacial fjords is crucial to explaining recent temporal and spatial variability in glacier dynamics, as well as freshwater transport on the continental shelf. The fjords are commonly assumed to exhibit a plume driven circulation that draws in warmer and saltier Atlantic-origin water toward the glacier at depth. Freshwater input at glacier termini directly drives this circulation and significantly influences water column stratification, which indirectly feeds back on the plume driven circulation. Previous work has focused on freshwater inputs from surface runoff and submarine melting, but the contribution from iceberg melt, a potentially important freshwater source, has not been quantified. Here, we develop a new technique combining in situ observations of movement from iceberg-mounted GPS units with multispectral satellite imagery from Landsat 8. The combination of datasets allows us to examine the details of iceberg movement and quantify mean residence times in a given fjord. We then use common melt rate parameterizations to estimate freshwater input for a given iceberg, utilizing novel satellite-derived iceberg distributions to scale up to a fjord-wide freshwater contribution. We apply this technique to Rink Isbræ and Kangerlussuup Sermia in west Greenland, and Helheim Glacier in southeast Greenland. The analysis can be rapidly expanded to look at other systems as well as seasonal and interannual changes in how icebergs affect the circulation and stratification of Greenland's outlet glacial fjords. Ultimately, this work will lead to a more complete understanding of the wide range of factors that control the observed regional variability in Greenland's glaciers.

  1. Ice-Ocean Interactions to the North-West of Greenland: Glaciers, Straits, Ice Bridges, and the Rossby Radius (Invited)

    NASA Astrophysics Data System (ADS)

    Muenchow, A.; Falkner, K. K.; Melling, H.; Johnson, H. L.; Huntley, H. S.; Ryan, P.; Friends Of Petermann

    2010-12-01

    Petermann Glacier at 81 N latitude is a major outlet glacier adjacent to Nares Strait. It terminates in a long (70 km), narrow (16 km) and thin (50 m) floating tongue and has a grounding line more than 500 m below sea level. A calving event in 2010 reduced the floating area by 25% and produced a single 240 km2 ice island currently moving south in Nares Strait where it will likely interact with island to potentially create a temporary polynya in Nares Strait. The 2010 calving from Petermann Glacier contributes <10% to its mass balance as more than 80% is lost due to basal melting by the ocean. Hence the largely unexplored physics at the ice-ocean interface determine how a changing climate impacts this outlet glacier. Conducting exploratory surveys inside Petermann Fjord in 2003, 2007, and 2009, we find a 1100 m deep fjord connected to Nares Strait via a sill at 350-450 m depth. The fjord receives about 3 times the amount of heat required for the basal melt rates. Furthermore, limited data and analytical modeling suggests a 3-dimensional circulation over the upper 300-m of the water column with a coastally trapped buoyant outflow. We integrate these findings with more complete oceanic time series data from an array moored in Nares Strait from 2003 through 2009 near 80.5 N. In the past Nares Strait and Petermann Fjord were covered by land fast sea ice during the 9-10 month long winter season. Archeological and remotely sensed records indicate that an ice bridge formed regularly at the southern end of Nares Strait creating the North-Water polynya near 79 N latitude. Since 2006 this ice bridge has largely failed to form, leading, perhaps, to the occasional formation of a secondary ice bridge 300 km to the north where Nares Strait connects to the Arctic Ocean. However, this ice bridge appears to form for shorter periods only. Consequently Arctic sea ice can now exit the Arctic in winter via pathways to the west of Greenland all year. We speculate that this changed ocean

  2. Investigating Greenland Outlet Glacier Annual Motion in Response to Varying Subglacial Hydraulic Structure

    NASA Astrophysics Data System (ADS)

    Nienow, P. W.; Tedstone, A. J.; Gourmelen, N.; Sole, A. J.

    2014-12-01

    The relationship between surface melting and ice motion will affect how the Greenland Ice Sheet responds to climate and the structure of the subglacial drainage system may be crucial in controlling how changing melt-rates impact ice motion. Several lines of evidence indicate that hydraulically efficient subglacial channels extend tens of km inland from land-terminating margins of the Greenland Ice Sheet during the melt-season. However, it remains unclear the extent to which water pressure variations in these drainage axes perturb ice-motion in areas both proximal and distal to the channels where the drainage system is likely hydraulically inefficient. Here, we present ice velocities observed with field based GPS and remotely sensed TerraSAR-X data across a land-terminating region of the south-west Greenland ice sheet during the melt-year 2012-2013, to examine the impact of varying drainage system structure on the spatial pattern of seasonal and annual ice motion. We find that whilst spatial variability in the configuration of the subglacial drainage system controls ice motion at short timescales, this configuration has negligible impact on the spatial pattern of the proportion of annual motion which occurs during summer. Whilst absolute annual velocities vary substantially, the proportional contribution of summer motion to annual motion does not. Subglacial hydrology does not therefore have a significant impact on the overall extent to which summer motion contributes to annual motion. These findings imply that the representation of hydrology in ice sheet models may be simplified.

  3. The North Water Polynya and Velocity, Calving Front and Mass Change in Surrounding Glaciers in Greenland and Canada Over the Last 30 Years

    NASA Astrophysics Data System (ADS)

    Edwards, L.

    2015-12-01

    Major uncertainties surround future estimates of sea level rise attributable to mass loss from Greenland and the surrounding ice caps in Canada. Understanding changes across these regions is vital as their glaciers have experienced dramatic changes in recent times. Attention has focused on the periphery of these regions where land ice meets the ocean and where ice acceleration, thinning and increased calving have been observed. Polynyas are areas of open water within sea ice which remain unfrozen for much of the year. They vary significantly in size (~3 km2 to > ~85,000 km2 in the Arctic), recurrence rates and duration. Despite their relatively small size, polynyas strongly impact regional oceanography and play a vital role in heat and moisture exchange between the polar oceans and atmosphere. Where polynyas are present adjacent to tidewater glaciers their influence on ocean circulation and water temperatures has the potential to play a major part in controlling subsurface ice melt rates by impacting on the water masses reaching the calving front. They also have the potential to influence air masses reaching nearby glaciers and ice caps by creating a maritime climate which may impact on the glaciers' accumulation and surface melt and hence their thickness and mass balance. Polynya presence and size also have implications for sea ice extent and therefore may influence the buttressing effect on neighbouring tidewater glaciers. The work presented uses remote sensing and mass balance model data to study changes in the North Water polynya (extent, ice concentration, duration) and neighbouring glaciers and ice caps (velocities, calving front positions and mass balance) in Canada and Greenland over a period of approximately 30 years from the mid-1980s through to 2015.

  4. The kinematic response of Petermann Glacier, Greenland to ice shelf perturbation

    NASA Astrophysics Data System (ADS)

    Hubbard, A.; Box, J. E.; Bates, R.; Nick, F.; Luckman, A. J.; van de Wal, R.; Doyle, S. H.

    2010-12-01

    The acceleration and dynamic thinning of interior zones of the polar ice sheets due to outlet/ice shelf retreat has been identified as a factor hastening their demise and contribution to global sea-level rise. The detachment of a 275 square km area of the Petermann Glacier ice shelf in August, 2010 presents a natural experiment to investigate the timing, mechanisms and efficacy of upstream dynamic feedbacks resulting from a singular but potentially significant frontal perturbation. In 2009, a permanent geodetic/differential GPS strain network logging every 10 seconds was deployed along a 200 km longitudinal profile from the ice front across the grounding line extending into the interior of Petermann Glacier to characterize the system’s state before, during and after any such event. We present an overview of the geophysical measurements conducted and analyze the kinematics of the shelf detachment in relation to local environmental forcing. Finally, we discuss the postulated instantaneous and ongoing evolution in force-balance and concomitant dynamic response resulting from the perturbation along with its implications for Petermann's ongoing stability. Petermann Glacier GNSS base & telemetric GPS facility: community AA & rehab meet point. On ice geodetic-GPS station flat out & reading 0 Volts

  5. Investigating the dynamics of deglaciation in coastal areas of southeast Greenland

    NASA Astrophysics Data System (ADS)

    Dyke, Laurence M.; Hughes, Anna L. C.; Andresen, Camilla S.; Murray, Tavi; Hiemstra, John F.; Rodés, Ángel

    2016-04-01

    passive areas appears to have occurred later than in the major fjord systems; this suggests that ice dynamic processes were a key driver of deglaciation in SE Greenland. References: Hughes, A. L. C.; Rainsley, E.; Murray, T.; Fogwill, C. J.; Schnabel, C., Xu, S., 2012. Rapid response of Helheim Glacier, southeast Greenland, to early Holocene climate warming. Geology 40, 427-430.

  6. Assessing supraglacial water volume and the changing dynamics of the surface topography near the Jakobshavn Glacier, Greenland

    NASA Astrophysics Data System (ADS)

    Adler, John J.

    On the Greenland Ice Sheet (GIS), the effect of the melt season's changing supraglacial lakes on outlet glacier discharge is not well understood. It is known that many supraglacial lakes drain rapidly during each melt season. While there are conflicting theories of the significance of supraglacial lake drainages towards enhancing ice sheet flow, it is highly important to quantify the actual water volume of supraglacial lakes since their drainage via crevasses or moulins enables the injection of melt water directly into the GIS. The 2008 Arctic MUltiSensor Cryospheric Observation eXperiment (Arctic MUSCOX) was the first scientific Unmanned Aircraft System (UAS) used in Greenland. The goal was determination of the changing volumes of supraglacial melt water lakes through the fusion of disparate data sets from in-situ, airborne, and satellite sensors. Near the Jakobshavn Isbrae region, four supraglacial lakes at different elevations along a transect at 68.73°N were monitored over the 2006, 2007, and 2008 melt seasons. The changing lake volumes are calculated for each day of usable MODIS imagery, employing DEM's from both ASTER Global and the MUSCOX lidar survey. During this three year period, no observed lake was larger in volume than 0.15km3, or larger in area than 10.4km2, implying a size limit for supraglacial lakes. In this study a new technique is developed calculating runoff using daily changing albedo and surface height measurements (dH) from the Greenland Climatic Network (GC-Net) Automatic Weather Stations (AWS) at locations JAR1 and JAR2. Runoff is calculated on a daily basis, both regionally and for a 1,183km 2 inset strip straddling the transect. At JAR1 the calculated linear runoff for 2006, 2007, and 2008 is 1.79m, 1.99m, and 1.96m, respectively; at JAR2 the calculated runoff is 2.11m, 2.86m, and 2.40m, respectively. Regional projections are made that account for future atmospheric temperature increases between 0.5°C and 3.0°C; they indicate up to a

  7. The Subglacial Access and Fast Ice Research Experiment (SAFIRE): 1. Borehole-based englacial and subglacial measurements from a rapidly-moving tidewater glacier: Store Glacier, Greenland

    NASA Astrophysics Data System (ADS)

    Hubbard, Bryn; Doyle, Samuel; Christoffersen, Poul; Young, Tun Jan; Hofstede, Coen; Hubbard, Alun; Box, Jason; Todd, Joe; Bougamont, Marion

    2016-04-01

    As part of the Subglacial Access and Fast Ice Research Experiment (SAFIRE) pressurised hot water was used to drill four 603-616 m-long boreholes to the bed of the Greenland Ice Sheet at a site located 30 km from the calving front of fast-flowing, marine-terminating Store Glacier (70 degrees N, ~1000 m elevation). Four wired sensor strings were successfully installed in three of the boreholes. These included a thermistor string to obtain the englacial temperature profile installed in the same borehole as a string of tilt sensors to measure borehole deformation, and two sets of combined water pressure, electrical conductivity and turbidity sensors installed just above the bed in separate, adjacent boreholes. The boreholes made a strong hydrological connection to the bed during drilling, draining rapidly to ~80 m below the ice surface. The connection of subsequent boreholes was observed as a perturbation in water pressure and temperature recorded in neighbouring boreholes, indicating an effective hydrological connection between them. The sensors, which were wired to data-loggers at the surface, operated for between ~30 and >80 days from late summer into autumn before the cables stretched and snapped, with the lowermost sensors failing first. The records obtained from these sensors reveal (i) subglacial water pressures that were close to overburden but which generally increased through the period of measurement and varied diurnally by ~0.3 m, (ii) a minimum englacial temperature of -21 degrees C underlain by a zone of temperate ice, some tens of m thick, located immediately above the bed, and (iii) high rates of internal deformation and strain that increased towards the bed. These borehole observations are complemented by GPS measurements of ice motion, meteorological data, and seismic and radar surveys.

  8. Investigating the Cause of the 2012 Acceleration of Jakobshavn Isbræ, Greenland Using High Resolution Observations of the Glacier Terminus

    NASA Astrophysics Data System (ADS)

    Cassotto, R.; Fahnestock, M. A.; Boettcher, M. S.; Amundson, J. M.; Truffer, M.

    2014-12-01

    After decades of relative stability, Jakobshavn Isbræ, a tidewater glacier in West Greenland, started to destabilize at the turn of the century. The glacier thinned, the perennial tongue disintegrated, velocities doubled, and the terminus retreated. The glacier evolved over the next several years as it showed large seasonal variations in speed and a progressive kilometer-scale retreat of its calving front. Then, during the 2012 summer, Jakobshavn set a new record when its speed increased to rates more than four times the 1990s values, and consequently became the fastest glacier recorded by satellite yet. A 2-week field study was conducted along the terminus at that time; ground portable radar interferometers (GPRI), time-lapse cameras, GPS, and a tide gauge were deployed to characterize glacier dynamics along the ice-ocean boundary. We use >10,000 interferograms recorded with the terrestrial interferometers to probe the cause of this acceleration. We observe a 33% increase in glacier speed and a 250% increase in the amplitude of response to tidal forcing during our study period. We explore how the location of the terminus along the reverse bed slope contributed to the observed speedup, and we compare our findings with the long-term record of satellite observations. Our data show that understanding tidewater glacier dynamics requires knowledge of short-term variations along glacier termini that is currently not available from satellites. This study provides insight into such short-term dynamics on spatial scales comparable to satellite InSAR but with temporal resolution similar to GPS.

  9. Geomicrobiology of subglacial meltwater samples from Store Landgletscher and Russell Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Cameron, K. A.; Dieser, M.; Choquette, K.; Christner, B. C.; Hagedorn, B.; Harrold, Z.; Liu, L.; Sletten, R. S.; Junge, K.

    2012-12-01

    The melting of the Greenland Ice Sheet provides direct connections between atmospheric, supraglacial and subglacial environments. The intraglacial hydrological pathways that result are believed to accommodate the microbial colonization of subglacial environments; however, little is known about the abundance, diversity and activity of microorganisms within these niches. The Greenland Ice Sheet (1.7 million square kilometers) and its associated surpaglacial and subglacial ecosystems may contribute significantly to biogeochemical cycling processes. We analyzed subglacial microbial assemblages in subglacial outflows, near Thule and Kangerlussuaq, West Greenland. The investigative approach included correlating microbial diversity, inferred function, abundance, melt water chemistry, O-18 water isotope ratios, alkalinity and sediment load. Using Illumina sequencing, bacterial small subunit ribosomal RNA hypervariable regions have been targeted and amplified from both extracted DNA and reverse transcribed rRNA. Over 3 billion sequence reads have been generated to create a comprehensive diversity profile. Total abundances ranged from 2.24E+04 to 1.58E+06 cells mL-1. In comparison, the total abundance of supraglacial early season snow samples ranged from 3.35E+02 to 2.8E+04 cells mL-1. 65 % of samples incubated with cyano ditoyl tetrazolium chloride (CTC), used to identify actively respiring cells, contained CTC-positive cells. On average, these cells represented 1.9 % of the estimated total abundance (1.86E+02 to 2.19E+03 CTC positive cells mL-1; 1.39E+03 cells mL-1 standard deviation); comparative to those measured in temperate freshwater lakes. The overarching objective of our research is to provide data that indicates the role of microbial communities, associated with ice sheets, in elemental cycling and in the release of biomass and nutrients to the surrounding marine biome.

  10. Climatic influences on the geochemistry and microbial communities of glacial outflow from a southern Greenland outlet glacier.

    NASA Astrophysics Data System (ADS)

    Christie, L.; Stevenson, E. I.; Sheik, C.; Aciego, S.; Robbins, M.

    2016-12-01

    Polar ice sheet melt waters are important conduits of particulate and dissolved elements (e.g. silica and iron) to proglacial environments and oceans. Both biotic and abiotic process in the subglacial environment enrich glacial melt waters in solutes, where it has been inferred that both subglacial hydrology and microbial communities are intimately linked [1]. At the glacier terminus, ejected water is mixed from differing sources, from surface, meteoric, sub-glacial or englacial environments. To disentangle the potential sources of waters and links to daily climate, we present a late melt season progression of glacial hydro-geochemistry and microbial community diversity from Qoorqup Sermia, in southern Greenland (CD 208 to CD 266 2015). Over the course of sampling bulk stream hydrochemistry and elemental concentrations remain fairly stable with dissolved Si 17.2 μM L, P 0.37 μM L, S 0.7 μM L and Fe 0.2 μM L-1, and are within range of previous measurements [2]. Despite stable water geochemistry, there are several large punctuated increases in the phylogenetic diversity of microbial communities especially between days 217 and 237. Such increases in phylogenetic diversity have also been observed at Lemon Creek Glacier [3]. The lack of correlation between phylogenetic diversity and the geochemistry of the bulk subglacial outflow, suggests that changes in diversity may not be driven by a change in the subglacial system. Rather, microbial diversity changes at the terminus may be indicative of supra or englacial processes driven by localized climatic events during the melt season. These results, although preliminary, may indicate a relationship between surface melting and meteoric water flux through a glacier, and suggest microbes carried along with these waters may be used as indicators of water source and mixing rates with subglacial waters. [1] Tranter et al., 2005; Hydrol. Proc. 19, 995-998 [2] Aciego et al., 2015; EPSL, 424, 51-58 [3] Sheik et al., 2015; Front

  11. Geophysical constraints on the controls for outlet-glacier velocity variability

    NASA Astrophysics Data System (ADS)

    Nettles, M.

    2012-12-01

    The surface of the solid Earth is not opaque to signals generated in its fluid envelope, including the cryosphere. Among the signals now routinely recorded on seismographs anchored to the solid Earth are long-period surface waves generated by glacial earthquakes occurring in Greenland and Antarctica. Interdisciplinary study utilizing seismological and space-based remote sensing along with geodetic data has identified the source mechanism that generates this seismic signal: discrete ice-loss events of cubic-km scale at the margins of large outlet glaciers generate surface waves comparable to those from M~5 tectonic earthquakes. By combining the seismological observations with geodetic, meteorological, and glaciological approaches, the study of glacial earthquakes also allows the identification of these large ice-loss events as a primary control on short-term velocity variability at marine-terminating outlet glaciers. An understanding of this signal allows assessment of flow variability driven by surface melt, and by tidal forcing, that would otherwise be obscured by the calving signal. Much remains unknown about how these controls operate in detail, however. We use a comprehensive dataset of glacier position and velocity estimates derived from high-rate, continuous Global Positioning System (GPS) observations to examine changes in the velocity and strain field across multiple ice-loss events at East Greenland's Helheim Glacier. While we find that increases in glacier flow speed and longitudinal strain rate reliably coincide with large-scale losses of grounded ice, the amplitude of the response and the time period over which it is sustained are variable. We use these variations to assess additional controls on the glacier response to ice loss, and compare the variations due to ice loss with those resulting from variable input of surface meltwater.

  12. Phylogenetic analysis of anaerobic psychrophilic enrichment cultures obtained from a greenland glacier ice core

    NASA Technical Reports Server (NTRS)

    Sheridan, Peter P.; Miteva, Vanya I.; Brenchley, Jean E.

    2003-01-01

    The examination of microorganisms in glacial ice cores allows the phylogenetic relationships of organisms frozen for thousands of years to be compared with those of current isolates. We developed a method for aseptically sampling a sediment-containing portion of a Greenland ice core that had remained at -9 degrees C for over 100,000 years. Epifluorescence microscopy and flow cytometry results showed that the ice sample contained over 6 x 10(7) cells/ml. Anaerobic enrichment cultures inoculated with melted ice were grown and maintained at -2 degrees C. Genomic DNA extracted from these enrichments was used for the PCR amplification of 16S rRNA genes with bacterial and archaeal primers and the preparation of clone libraries. Approximately 60 bacterial inserts were screened by restriction endonuclease analysis and grouped into 27 unique restriction fragment length polymorphism types, and 24 representative sequences were compared phylogenetically. Diverse sequences representing major phylogenetic groups including alpha, beta, and gamma Proteobacteria as well as relatives of the Thermus, Bacteroides, Eubacterium, and Clostridium groups were found. Sixteen clone sequences were closely related to those from known organisms, with four possibly representing new species. Seven sequences may reflect new genera and were most closely related to sequences obtained only by PCR amplification. One sequence was over 12% distant from its closest relative and may represent a novel order or family. These results show that phylogenetically diverse microorganisms have remained viable within the Greenland ice core for at least 100,000 years.

  13. Phylogenetic analysis of anaerobic psychrophilic enrichment cultures obtained from a greenland glacier ice core

    NASA Technical Reports Server (NTRS)

    Sheridan, Peter P.; Miteva, Vanya I.; Brenchley, Jean E.

    2003-01-01

    The examination of microorganisms in glacial ice cores allows the phylogenetic relationships of organisms frozen for thousands of years to be compared with those of current isolates. We developed a method for aseptically sampling a sediment-containing portion of a Greenland ice core that had remained at -9 degrees C for over 100,000 years. Epifluorescence microscopy and flow cytometry results showed that the ice sample contained over 6 x 10(7) cells/ml. Anaerobic enrichment cultures inoculated with melted ice were grown and maintained at -2 degrees C. Genomic DNA extracted from these enrichments was used for the PCR amplification of 16S rRNA genes with bacterial and archaeal primers and the preparation of clone libraries. Approximately 60 bacterial inserts were screened by restriction endonuclease analysis and grouped into 27 unique restriction fragment length polymorphism types, and 24 representative sequences were compared phylogenetically. Diverse sequences representing major phylogenetic groups including alpha, beta, and gamma Proteobacteria as well as relatives of the Thermus, Bacteroides, Eubacterium, and Clostridium groups were found. Sixteen clone sequences were closely related to those from known organisms, with four possibly representing new species. Seven sequences may reflect new genera and were most closely related to sequences obtained only by PCR amplification. One sequence was over 12% distant from its closest relative and may represent a novel order or family. These results show that phylogenetically diverse microorganisms have remained viable within the Greenland ice core for at least 100,000 years.

  14. Phylogenetic analysis of anaerobic psychrophilic enrichment cultures obtained from a greenland glacier ice core.

    PubMed

    Sheridan, Peter P; Miteva, Vanya I; Brenchley, Jean E

    2003-04-01

    The examination of microorganisms in glacial ice cores allows the phylogenetic relationships of organisms frozen for thousands of years to be compared with those of current isolates. We developed a method for aseptically sampling a sediment-containing portion of a Greenland ice core that had remained at -9 degrees C for over 100,000 years. Epifluorescence microscopy and flow cytometry results showed that the ice sample contained over 6 x 10(7) cells/ml. Anaerobic enrichment cultures inoculated with melted ice were grown and maintained at -2 degrees C. Genomic DNA extracted from these enrichments was used for the PCR amplification of 16S rRNA genes with bacterial and archaeal primers and the preparation of clone libraries. Approximately 60 bacterial inserts were screened by restriction endonuclease analysis and grouped into 27 unique restriction fragment length polymorphism types, and 24 representative sequences were compared phylogenetically. Diverse sequences representing major phylogenetic groups including alpha, beta, and gamma Proteobacteria as well as relatives of the Thermus, Bacteroides, Eubacterium, and Clostridium groups were found. Sixteen clone sequences were closely related to those from known organisms, with four possibly representing new species. Seven sequences may reflect new genera and were most closely related to sequences obtained only by PCR amplification. One sequence was over 12% distant from its closest relative and may represent a novel order or family. These results show that phylogenetically diverse microorganisms have remained viable within the Greenland ice core for at least 100,000 years.

  15. Phylogenetic Analysis of Anaerobic Psychrophilic Enrichment Cultures Obtained from a Greenland Glacier Ice Core

    PubMed Central

    Sheridan, Peter P.; Miteva, Vanya I.; Brenchley, Jean E.

    2003-01-01

    The examination of microorganisms in glacial ice cores allows the phylogenetic relationships of organisms frozen for thousands of years to be compared with those of current isolates. We developed a method for aseptically sampling a sediment-containing portion of a Greenland ice core that had remained at −9°C for over 100,000 years. Epifluorescence microscopy and flow cytometry results showed that the ice sample contained over 6 × 107 cells/ml. Anaerobic enrichment cultures inoculated with melted ice were grown and maintained at −2°C. Genomic DNA extracted from these enrichments was used for the PCR amplification of 16S rRNA genes with bacterial and archaeal primers and the preparation of clone libraries. Approximately 60 bacterial inserts were screened by restriction endonuclease analysis and grouped into 27 unique restriction fragment length polymorphism types, and 24 representative sequences were compared phylogenetically. Diverse sequences representing major phylogenetic groups including alpha, beta, and gamma Proteobacteria as well as relatives of the Thermus, Bacteroides, Eubacterium, and Clostridium groups were found. Sixteen clone sequences were closely related to those from known organisms, with four possibly representing new species. Seven sequences may reflect new genera and were most closely related to sequences obtained only by PCR amplification. One sequence was over 12% distant from its closest relative and may represent a novel order or family. These results show that phylogenetically diverse microorganisms have remained viable within the Greenland ice core for at least 100,000 years. PMID:12676695

  16. Melt Undercutting and Calving from Tidewater Glaciers: Observations and Model Results

    NASA Astrophysics Data System (ADS)

    Benn, D.; Cook, S.; Åström, J. A.; Luckman, A. J.; Zwinger, T.

    2014-12-01

    Dynamic models incorporating crevasse-depth calving laws have enjoyed considerable success in simulating observed behavior of tidewater glaciers. Such models are based on the assumption that longitudinal strain rates exert a first-order control on calving, and that penetration of surface and basal crevasses provides the ultimate constraint on glacier extent. However, 'second-order' processes such as melt undercutting may significantly amplify calving rates, initiating seasonal and longer-term glacier retreats. We present high temporal and spatial resolution TerraSAR-X data from Svalbard that indicate a strong annual cycle in calving rates, peaking in September-October coincident with maximum fjord temperatures. This pattern is consistent for all studied glaciers irrespective of glacier activity (fast, slow, surging or quiescent), and we conclude that in Svalbard calving is paced by melt-undercutting followed by mechanical destabilization of the ice tongue. Although parameterizations of melt undercutting are included in many models employing the crevasse-depth calving criterion, amplification of calving by melt undercutting (the 'O'Leary Effect') has not been rigorously analyzed or tested against observations. We take a novel approach to this problem, and couple the finite element model Elmer-Ice with a discrete particle model (DPM) to explore in detail the links between melt undercutting and failure of the ice tongue. Employing glacier front geometries representative of Kronebreen (Svalbard), Columbia Glacier (Alaska) and Helheim Glacier (Greenland), we use Elmer-Ice to simulate progressive undercutting of the ice front by melting. At selected time steps, the model geometry was exported into the DPM, and runs conducted to study fracturing and calving behavior using different values of the fracture stress. We quantify the O'Leary Effect for different geometries, and propose a modified calving law incorporating the effects of melt-undercutting. The results highlight

  17. Dynamics of a vertical turbulent plume in a stratification typical of Greenland fjords: an idealized model of subglacial discharge

    NASA Astrophysics Data System (ADS)

    Stenberg, Erik; Ezhova, Ekaterina; Cenedese, Claudia; Brandt, Luca

    2017-04-01

    We the report results of large eddy simulations of a turbulent buoyant plume in a configuration providing an idealized model of subglacial discharge from a submarine glacier in stratifications typical of Greenland Fjords. We neglect a horizontal momentum of the plume and assume that its influence on the plume dynamics is small and important only close to the source. Moreover, idealized models have considered the plume adjacent to the glacier as a half-conical plume (e.g., [1]). Thus, to compare the results for such plume with the classical plume theory, developed for free plumes entraining ambient fluid from all directions, it is convenient to add the second half-conical part and consider a free plume with double the total discharge as a model. Given the estimate of the total subglacial discharge for Helheim Glacier in Sermilik Fjord [2], we perform simulations with double the total discharge in order to investigate the dynamics of the flow in typical winter and summer stratifications in Greenland fjords [3]. The plume is discharged from a round source of various diameters. In winter, when the stratification is similar to an idealised two-layers case, turbulent entrainment and generation of internal waves by the plume top are in agreement with the theoretical and numerical results obtained for turbulent jets in a two-layer stratification. In summer, instead, the stratification is more complex and turbulent entrainment is significantly reduced. The subsurface layer in summer is characterized by a strong density gradient and the oscillating plume generates non-linear internal waves which are able to mix this layer even if the plume does not penetrate to the surface. The classical theory for the integral parameters of a turbulent plume in a homogeneous fluid gives accurate predictions of the plume parameters in the weakly stratified lower layer up to the pycnocline. [1] Mankoff, K. D., F. Straneo, C. Cenedese, S. B. Das, C. D. Richards, and H. Singh, 2016: Structure

  18. Investigating the Role of Buoyancy in Tidewater Glacier Iceberg Calving Dynamics

    NASA Astrophysics Data System (ADS)

    Trevers, M.; Payne, A. J.; Cornford, S. L.

    2016-12-01

    In recent decades, many of Greenland's major outlet glaciers have retreated dramatically due to increased iceberg calving, associated with an increase in velocity and inland thinning. The potential contribution to sea level rise (SLR) of a complete collapse of the Greenland Ice Sheet (GrIS) is 7m. Iceberg calving is an important process not only as a major source of mass loss from the GrIS, but also for the controlling influence it has on the dynamics of the grounding line and over the ice sheet as a whole. Despite plenty of scientific attention and a diverse body of literature, the processes involved in calving, their controlling factors and how it feeds back into glacier and ice sheet dynamics are still not fully understood. This presents a major uncertainty into projections of SLR over the coming decades and centuries. Buoyancy forces have been proposed as a major influencing factor in inducing calving in large Greenland tidewater glaciers such as Helheim Glacier. We present a new conceptual model for buoyancy-induced calving, in which a small initial calving event quickly increases the buoyant load on the terminus, leading to fast basal crevassing and much larger calving events. Using Elmer/Ice we are able to resolve the stress distributions in high resolution at the calving front. By investigating the stress distributions induced in a buoyant calving front, we hope to gain an understanding of how environmental influences such as surface thinning and waterline notch-cutting influence the calving rate. We will provide evidence for our new conceptual model from numerical simulation results and calving observations.

  19. Hydraulic conductivity of a firn aquifer system in southeast Greenland

    NASA Astrophysics Data System (ADS)

    Miller, Olivia L.; Solomon, D. Kip; Miège, Clément; Koenig, Lora S.; Forster, Richard R.; Montgomery, Lynn N.; Schmerr, Nicholas; Ligtenberg, Stefan R. M.; Legchenko, Anatoly; Brucker, Ludovic

    2017-05-01

    Some regions of the Greenland ice sheet, where snow accumulation and melt rates are high, currently retain substantial volumes of liquid water within the firn pore space throughout the year. These firn aquifers, found between 10-30 m below the snow surface, may significantly affect sea level rise by storing or draining surface meltwater. The hydraulic gradient and the hydraulic conductivity control flow of meltwater through the firn. Here we describe the hydraulic conductivity of the firn aquifer estimated from slug tests and aquifer tests at six sites located upstream of Helheim Glacier in southeastern Greenland. We conducted slug tests using a novel instrument, a piezometer with a heated tip that melts itself into the ice sheet. Hydraulic conductivity ranges between 2.5x10-5 and 1.1x10-3 m/s. The geometric mean of hydraulic conductivity of the aquifer is 2.7x10-4 m/s with a geometric standard deviation of 1.4 from both depth specific slug tests (analyzed using the Hvorslev method) and aquifer tests during the recovery period. Hydraulic conductivity is relatively consistent between boreholes and only decreases slightly with depth. The hydraulic conductivity of the firn aquifer is crucial for determining flow rates and patterns within the aquifer, which inform hydrologic models of the aquifer, its relation to the broader glacial hydrologic system, and its effect on sea level rise.

  20. Sub-glacier ocean properties and mass balance estimates of Petermann Gletscher's floating tongue in Northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Steffen, K.; Huff, R. D.; Cullen, N.; Rignot, E.; Bauder, A.

    2004-12-01

    Petermann Gletscher is the largest and most influential outlet glacier in central northern Greenland. Located at 81 N, 60 W, it drains an area of 71,580 km2, with a discharge of 12 cubic km of ice per year into the Arctic Ocean. We finished a third field season in spring 2004 collecting in situ data on local climate, ice velocity, ice thickness profiles and bottom melt rates of the floating ice tongue. In addition, water properties (salinity and temperature profiles) in large, channel-like bottom cavities beneath the floating ice tongue were measured. The melt rates in these "channels" are in excess of 10 m/y and probably responsible for most of the mass loss of the Petermann Gletscher. The ocean measurements will be discussed in comparison with other ocean-profile soundings in the region. The bottom topography of the floating ice tongue has been mapped for some regions using surface-based ground penetrating radar at 25 MHz frequency and NASA aircraft radar profiles. A new map showing these under-ice features will be presented. GPS tidal motion has been measured over one lunar cycle at the flex zone and on the free floating ice tongue. These results will be compared to historic measurements made at the beginning of last century. A "worm-like" sheer feature of 80 m in height and several km in length has been studied using differential GPS readings. The mean velocity of the floating tongue ice is 1.08 km/y in that region, whereas the ice along the margin has a 30%-reduced flow speed, resulting in this strange looking sheer feature. Finally, the mass balance of the floating ice tongue will be discussed based on in situ measurements, aircraft profiles, satellite data, and model approximations.

  1. Flying Low over Southeast Greenland

    NASA Image and Video Library

    Few of us ever get to see Greenland's glaciers from 500 meters above the ice. But in this video — recorded on April 9,2013 in southeast Greenland using a cockpit camera installed and operated by ...

  2. 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.

  3. Changing tidewater glacier extent and response to climate from Little Ice Age to present: observations and modelling of Kangiata Nunaata Sermia, SW Greenland

    NASA Astrophysics Data System (ADS)

    Mair, D.; Lea, J. M.; Nick, F. M.; Rea, B. R.; Nienow, P. W.

    2013-12-01

    Records of Greenlandic tidewater glacier (TWG) change are primarily restricted to the period covered by satellite observation. This study extends the record of terminus change of the tidewater outlet glacier Kangiata Nunaata Sermia (KNS), SW Greenland to its Little Ice Age maximum (LIAmax). This is achieved using a combination of geomorphology, written observations, and historical and satellite imagery. We explore likely marine and atmospheric controls on terminus change by comparison with existing records of local air and ocean temperatures and, for earlier periods, by modelling glacier response to systematic changes in marine and oceanic forcings at the terminus. Results from the glacier reconstruction show that retreat began in the late 18th century, with the terminus retreating at least 12 km from its LIAmax by 1859. KNS then experienced a period of relative stability before advancing to its 20th century maximum by ~1920. Significant retreat occurred from 1921-1965, before periods of advance and retreat up until 1997. Subsequent to this, KNS has retreated by 2 km up to the end of the 2012 melt season. The LIAmax to present retreat of KNS totals 22.6 km. Comparison of terminus fluctuations to local air temperature (1866-present) and sea surface temperature (1870-present) anomalies demonstrate that air temperature exerts a significant modulating control on terminus stability for the duration of the record. A state-of-the-art 1-dimensional flow-band model driven by submarine melt (SM) and crevasse water depth (CWD; Nick et al, 2010) is capable of reconstructing observed terminus fluctuations during earlier periods for realistic values of SM using a range of CWD. This provides confidence that such models are capable of predicting TWG terminus variability over centennial timescales.

  4. Phylogenetic and physiological diversity of microorganisms isolated from a deep greenland glacier ice core

    NASA Technical Reports Server (NTRS)

    Miteva, V. I.; Sheridan, P. P.; Brenchley, J. E.

    2004-01-01

    We studied a sample from the GISP 2 (Greenland Ice Sheet Project) ice core to determine the diversity and survival of microorganisms trapped in the ice at least 120,000 years ago. Previously, we examined the phylogenetic relationships among 16S ribosomal DNA (rDNA) sequences in a clone library obtained by PCR amplification from genomic DNA extracted from anaerobic enrichments. Here we report the isolation of nearly 800 aerobic organisms that were grouped by morphology and amplified rDNA restriction analysis patterns to select isolates for further study. The phylogenetic analyses of 56 representative rDNA sequences showed that the isolates belonged to four major phylogenetic groups: the high-G+C gram-positives, low-G+C gram-positives, Proteobacteria, and the Cytophaga-Flavobacterium-Bacteroides group. The most abundant and diverse isolates were within the high-G+C gram-positive cluster that had not been represented in the clone library. The Jukes-Cantor evolutionary distance matrix results suggested that at least 7 isolates represent new species within characterized genera and that 49 are different strains of known species. The isolates were further categorized based on the isolation conditions, temperature range for growth, enzyme activity, antibiotic resistance, presence of plasmids, and strain-specific genomic variations. A significant observation with implications for the development of novel and more effective cultivation methods was that preliminary incubation in anaerobic and aerobic liquid prior to plating on agar media greatly increased the recovery of CFU from the ice core sample.

  5. Phylogenetic and physiological diversity of microorganisms isolated from a deep greenland glacier ice core

    NASA Technical Reports Server (NTRS)

    Miteva, V. I.; Sheridan, P. P.; Brenchley, J. E.

    2004-01-01

    We studied a sample from the GISP 2 (Greenland Ice Sheet Project) ice core to determine the diversity and survival of microorganisms trapped in the ice at least 120,000 years ago. Previously, we examined the phylogenetic relationships among 16S ribosomal DNA (rDNA) sequences in a clone library obtained by PCR amplification from genomic DNA extracted from anaerobic enrichments. Here we report the isolation of nearly 800 aerobic organisms that were grouped by morphology and amplified rDNA restriction analysis patterns to select isolates for further study. The phylogenetic analyses of 56 representative rDNA sequences showed that the isolates belonged to four major phylogenetic groups: the high-G+C gram-positives, low-G+C gram-positives, Proteobacteria, and the Cytophaga-Flavobacterium-Bacteroides group. The most abundant and diverse isolates were within the high-G+C gram-positive cluster that had not been represented in the clone library. The Jukes-Cantor evolutionary distance matrix results suggested that at least 7 isolates represent new species within characterized genera and that 49 are different strains of known species. The isolates were further categorized based on the isolation conditions, temperature range for growth, enzyme activity, antibiotic resistance, presence of plasmids, and strain-specific genomic variations. A significant observation with implications for the development of novel and more effective cultivation methods was that preliminary incubation in anaerobic and aerobic liquid prior to plating on agar media greatly increased the recovery of CFU from the ice core sample.

  6. Phylogenetic and physiological diversity of microorganisms isolated from a deep greenland glacier ice core.

    PubMed

    Miteva, V I; Sheridan, P P; Brenchley, J E

    2004-01-01

    We studied a sample from the GISP 2 (Greenland Ice Sheet Project) ice core to determine the diversity and survival of microorganisms trapped in the ice at least 120,000 years ago. Previously, we examined the phylogenetic relationships among 16S ribosomal DNA (rDNA) sequences in a clone library obtained by PCR amplification from genomic DNA extracted from anaerobic enrichments. Here we report the isolation of nearly 800 aerobic organisms that were grouped by morphology and amplified rDNA restriction analysis patterns to select isolates for further study. The phylogenetic analyses of 56 representative rDNA sequences showed that the isolates belonged to four major phylogenetic groups: the high-G+C gram-positives, low-G+C gram-positives, Proteobacteria, and the Cytophaga-Flavobacterium-Bacteroides group. The most abundant and diverse isolates were within the high-G+C gram-positive cluster that had not been represented in the clone library. The Jukes-Cantor evolutionary distance matrix results suggested that at least 7 isolates represent new species within characterized genera and that 49 are different strains of known species. The isolates were further categorized based on the isolation conditions, temperature range for growth, enzyme activity, antibiotic resistance, presence of plasmids, and strain-specific genomic variations. A significant observation with implications for the development of novel and more effective cultivation methods was that preliminary incubation in anaerobic and aerobic liquid prior to plating on agar media greatly increased the recovery of CFU from the ice core sample.

  7. Greenland Flow Dynamics: (De)coding Process Understanding

    NASA Astrophysics Data System (ADS)

    Alley, R. B.; Parizek, B. R.; Anandakrishnan, S.; Applegate, P. J.; Christianson, K. A.; Dixon, T. H.; Holland, D. M.; Holschuh, N.; Keller, K.; Koellner, S. J.; Lampkin, D. J.; Muto, A.; Nicholas, R.; Stevens, N. T.; Voytenko, D.; Walker, R. T.

    2015-12-01

    Extensive modeling informed by the growing body of observational data yields important insights to the controlling processes operating across a range of spatiotemporal scales that have influenced the dynamic variability of the Greenland ice sheet. Pressurized basal lubrication enhances ice flow. This lubricating water is largely produced by basal and/or surface melt. For the North East Greenland Ice Stream, elevated geothermal heat flux (GHF) near its onset helps initiate the streaming flow. We suggest that the elevated GHF is likely caused by melt production and migration due to cyclical loading of the lithosphere over glacial timescales. On sub-seasonal timescales, surface meltwater production and transmission to the subglacial environment can enhance flow for pressurized, distributed hydraulic systems and diminish regional sliding for lower-pressure, channelized systems. However, in a warming climate, this lubricating source occurs across an expanding ablation zone, possibly softening shear margins and triggering basal sliding over previously frozen areas. Yet, the existence of active englacial conduits can lead to a plumbing network that helps preserve ice tongues and limit the loss of important buttressing of outlet glacier flow. Ocean forcing has been implicated in the variability of outlet glacier speeds around the periphery of Greenland. The extent and timescale over which those marginal changes influence inland flow depends on the basal rheology that, on a local scale, also influences the concentration of englacial stresses. Detailed observations of a calving event on Helheim Glacier have helped constrain diagnostic simulations of the pre- and post-calving stress states conducted in hopes of informing improved calving relationships. Furthermore, warm-water-mass variability within Irminger/Atlantic Waters off Greenland may play an important role in the monthly modulation of outlet glacier flow speeds, as has been observed for an ice stream draining into

  8. High resolution monitoring of a calving glacier using a wireless network of GNSS sensors.

    NASA Astrophysics Data System (ADS)

    Selmes, Nick; Aspey, Robin; Edwards, Stuart; James, Timothy; Loskot, Pavel; Martin, Ian; Moshin, Anas; Murray, Tavi; Nettles, Meredith; O'Farrell, Tim; Rigelsford, Jonathan; Rutt, Ian

    2013-04-01

    Calving glaciers have been identified as having a crucial role in the mass balance of the Greenland Ice Sheet, with acceleration and retreat of these glaciers resulting in major mass loss from the ice sheet interior, leading to a corresponding sea level rise. The ability to reproduce observed glacier behaviour in calving models is very desirable, but this is hindered by the difficulty of obtaining appropriate field measurements, combined with the complex interaction of the possible controls on iceberg calving. Our project brings together experts in glaciology, Global Navigation Satellite Systems (GNSS) technology and processing, and wireless networking, to design, install and operate a wireless network of GNSS sensors at the margin of a heavily crevassed Greenland outlet glacier. The network will provide velocity and elevation data of unprecedented resolution in time and space for the key marginal area of the glacier, where recent changes in glacier dynamics appear to have initiated. These will be analysed in conjunction with contemporaneous auxiliary data, such as surface and airborne lidar measurements of surface topography, crevasse spacing and calving rates, to yield new insights into processes active at the margins of tidewater glaciers. Our major field campaign will be in summer 2013, with a network of approximately 20 GNSS sensors being deployed, and a suite of ancillary data being collected in tandem. In preparation, we deployed a small test network of three GNSS sensors along the Helheim Glacier flowline in summer 2012, and here we present results from these sensors as a demonstration of the detail we expect to obtain in our main field season. The deployment of our GNSS sensors in summer 2012 coincided with a large calving event. We have no direct observations of this event; however, 250-500 m of ice was lost from the northern half of the calving front during the period 22-24th July, inferred from MODIS imagery. This retreat coincided with a significant

  9. Rapid advance, and rapid retreat at Kangiata Nunaata Sermia: potential for long term numerical model validation of Greenland outlet glacier dynamics.

    NASA Astrophysics Data System (ADS)

    Pearce, Danni; Mair, Doug; Rea, Brice; Lea, James; Schofield, Ed; Barr, Iestyn; Kamenos, Nick

    2017-04-01

    At present, there is a poor understanding of centennial Greenlandic tidewater glacier (TWG) dynamics, with the majority of numerical modelling studies focussing on retreat during the last few decades. This is the result of an observational bias towards the last 40-50 years, during which time behaviour has been dominated by retreat. Consequently, the datasets currently used for model calibration/validation do not include a full range of glacier behaviour. To have confidence in model results that seek to simulate over centennial timescales (i.e. to 2100), it is therefore crucial to be able to (1) validate model behaviour over these timescales and (2) test models against significant advance as well as retreat phases. Kangiata Nunaata Sermia (KNS), located c. 100 km inland from Nuuk at the head of Godthåbsfjord, SW Greenland, is the largest TWG south of Jakobshavn Isbræ. Here, we use multiple terrestrial proxies (14C, geomorphology, pollen) and modelling, to demonstrate that KNS first advanced, then retreated >22 km during the last 1000 years. Notably, ages support a rapid (>100 ma-1) Little Ice Age (LIA; AD c. 1300 to 1850) advance phase in the early part of the millennium, before undergoing stepped, rapid multi-kilometre retreats following its LIA maximum. These data provide a potentially excellent dataset to calibrate and validate numerical models over multi-decadal to centennial timescales, helping to more comprehensively understand TWG dynamics and increase confidence in their projected contributions to future sea-level rise.

  10. Spatial extent and temporal variability of Greenland firn aquifers detected by ground and airborne radars

    NASA Astrophysics Data System (ADS)

    Miège, Clément; Forster, Richard R.; Brucker, Ludovic; Koenig, Lora S.; Solomon, D. Kip; Paden, John D.; Box, Jason E.; Burgess, Evan W.; Miller, Julie Z.; McNerney, Laura; Brautigam, Noah; Fausto, Robert S.; Gogineni, Sivaprasad

    2016-12-01

    We document the existence of widespread firn aquifers in an elevation range of 1200-2000 m, in the high snow-accumulation regions of the Greenland ice sheet. We use NASA Operation IceBridge accumulation radar data from five campaigns (2010-2014) to estimate a firn-aquifer total extent of 21,900 km2. We investigate two locations in Southeast Greenland, where repeated radar profiles allow mapping of aquifer-extent and water table variations. In the upper part of Helheim Glacier the water table rises in spring following above-average summer melt, showing the direct firn-aquifer response to surface meltwater production changes. After spring 2012, a drainage of the firn-aquifer lower margin (5 km) is inferred from both 750 MHz accumulation radar and 195 MHz multicoherent radar depth sounder data. For 2011-2014, we use a ground-penetrating radar profile located at our Ridgeline field site and find a spatially stable aquifer with a water table fluctuating less than 2.5 m vertically. When combining radar data with surface topography, we find that the upper elevation edge of firn aquifers is located directly downstream of locally high surface slopes. Using a steady state 2-D groundwater flow model, water is simulated to flow laterally in an unconfined aquifer, topographically driven by ice sheet surface undulations until the water encounters crevasses. Simulations suggest that local flow cells form within the Helheim aquifer, allowing water to discharge in the firn at the steep-to-flat transitions of surface topography. Supported by visible imagery, we infer that water drains into crevasses, but its volume and rate remain unconstrained.

  11. Warm Atlantic inflow toward the Helmheim-Sermilik glacier-fjord system, South-East Greenland: Insights from a high-resolution Eulerian-Lagrangian model study.

    NASA Astrophysics Data System (ADS)

    Koszalka, I. M.; Haine, T. W. N.; Magaldi, M. G.

    2015-12-01

    The recent rapid increase in mass loss from the Greenland ice sheet has been primarily attributed to the acceleration of outlet glaciers. Helmheim-Sermilik is one of the major glacier-fjord systems in southeast Greenland that has been observed to retreat and nearly double its flow speed during the past decade. One possible cause of this acceleration is enhanced melting at the glacier terminus driven by the advection of warm waters of Atlantic origin over the East Greenland Shelf and into the Sermilik fjord (38E,66N). We use a high resolution configuration of the MITgcm circulation model (2km- and 15m grid spacing in horizontal and vertical directions, respectively), forced by Era-Interim winds and with a bathymetry updated by recent ship- and seal-borne measurements, to study intra-seasonal variability of the intrusions of the warm Atlantic water on the East Greenland Shelf advected toward the Sermilik fjord. The modeled T-S properties in the vicinity of the fjord sill are in good agreement with available observations. The warm inflow into the fjord occurs in quasi-oscillatory pulses of 1-10 day periodicity and of 50-200m vertical extent. The inflow occurs for (10-40)% time of the year (depending on depth), with a slight preference for winter months. The velocity and heat flux distributions are nearly Gaussian at 300m depth and non-Gaussian (Kurtosis>7) at greater depths, with a long positive tail corresponding to high (>0.4m/s) inflow events in winter. We quantify the relative importance of synoptic winds and internal dynamics in generating this variability. The Eulerian analysis is supplemented by backward tracing of O(10,000) Lagrangian particles revealing pathways and water-mass transformation of the inflow that is primarily fed by Irminger Current intruding on the shelf in the vicinity of the Spill Jet section (32E,65N) and channeled through the Sermilik Deep Opening. We ephasize the importance of proper representation of topographic features on the shelf

  12. Records of Local Glacier Variability in Western Greenland During the Holocene From Lake Sediments, Ice-cap-killed Vegetation, and 10Be Dating

    NASA Astrophysics Data System (ADS)

    Schweinsberg, A.; Briner, J. P.; Miller, G. H.; Bennike, O.

    2015-12-01

    Local mountain glaciers and ice caps are common and widespread along the periphery of Greenland and provide valuable paleoclimatic records because they respond sensitively to climate change. In contrast to extensive research on Greenland Ice Sheet (GIS) margin changes, the relative timing of mountain glaciation during the Holocene is poorly documented. Here, we use a multi-proxy approach to document the timing of local glacier advance and retreat throughout the past ~10 ka in western Greenland by combining: (1) proglacial lake sediment analysis, (2) 14C-dating of ice-cap-killed in situ plants, and (3) cosmogenic 10Be dating. Radiocarbon-dated sediment cores from Sikuiui and Pauiaivik lakes, eastern Nuussuaq, provide minimum-limiting ages for local deglaciation of 9.4 ± 0.06 and 8.8 ± 0.16 ka, respectively, and are in agreement with 10Be ages of regional deglaciation that average 10.9 ± 0.7 ka (n=8). Radiocarbon ages (n=54) of in situ plants along retreating cold-based ice cap margins reveal net snowline lowering beginning ~5 ka and are concurrent with the onset of Neoglaciation recorded in both lake systems. Modes of vegetation kill dates highlight distinct ice cap expansion phases at ~3.7, ~3.0, ~1.5 ka, and during the Little Ice Age. The most pronounced snowline lowering event ~4-3 ka is expressed in both lake records by deposition of mineral-rich sediments between ~4.5 and 2.5 ka. Ice cap expansion phases are broadly correlative with elevated minerogenic input in both lakes with some modes in the vegetation ages occurring just prior to increases in mineral-rich sediment input. Published studies of the western GIS margin suggest a major cooling event between ~4.3-3.2 ka, which overlaps with periods of enhanced local glacier activity and ice cap expansion in our dataset. Lastly, the dominant ice cap expansion episode ~3.7 ka in western Greenland is synchronous with a significant snowline lowering event on Baffin Island, suggesting a common climate forcing

  13. The Subglacial Access and Fast Ice Research Experiment (SAFIRE): 2. High magnitude englacial strain detected with autonomous phase-sensitive FMCW radar on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Young, Tun Jan; Christoffersen, Poul; Nicholls, Keith; Bun Lok, Lai; Doyle, Samuel; Hubbard, Bryn; Stewart, Craig; Hofstede, Coen; Bougamont, Marion; Todd, Joseph; Brennan, Paul; Hubbard, Alun

    2016-04-01

    Fast-flowing outlet glaciers terminating in the sea drain 90% of the Greenland Ice Sheet. It is well-known that these glaciers flow rapidly due to fast basal motion, but its contributing processes and mechanisms are, however, poorly understood. In particular, there is a paucity of data to quantify the extent to which basal sliding and internal ice deformation by viscous creep contribute to the fast motion of Greenland outlet glaciers. To study these processes, we installed a network of global positioning system (GPS) receivers around an autonomous phase-sensitive radio-echo sounder (ApRES) capable of imaging internal reflectors and the glacier bed. The ApRES system, including antennas, were custom-designed to monitor and image ice sheets and ice shelves in monostatic and multiple-input multiple-output (MIMO) modes. Specifically, the system transmits a frequency-modulated continuous-wave (FMCW) that increases linearly from 200 to 400 MHz over a period of 1 second. We installed this system 30 km up-flow of the tidewater terminus of Store Glacier, which flows into Uummannaq Fjord in West Greenland, and data were recorded every hour from 06 May to 16 July 2014 and every 4 hours from 26 July to 11 December 2014. The same site was used to instrument 600 m deep boreholes drilled to the bed as part of the SAFIRE research programme. With range and reflector distances captured at high temporal (hourly) and spatial (millimetre) resolutions, we obtained a unique, 6-month-long time series of strain through the vertical ice column at the drill site where tilt was independently recorded in a borehole. Our results show variable, but persistently high vertical strain. In the upper three-fourths of the ice column, we have calculated strain rates on the order of a few percent per year, and the strain regime curiously shifts from vertical thinning in winter to vertical thickening at the onset of summer melt. In the basal ice layer we observed high-magnitude vertical strain rates on

  14. Three-dimensional surface velocities of Storstrømmen glacier, Greenland, derived from radar interferometry and ice-sounding radar measurements

    NASA Astrophysics Data System (ADS)

    Reeh, Niels; Mohr, Johan Jacob; Nørvang Madsen, Søren; Oerter, Hans; Gundestrup, Niels S.

    Non-steady-state vertical velocities of up to 5 m a-1 exceed the vertical surface-parallel flow (SPF) components over much of the ablation area of Storstrømmen, a large outlet glacier from the East Greenland ice sheet. Neglecting a contribution to the vertical velocity of this magnitude results in substantial errors (up to 20%) also on the south-north component of horizontal velocities derived by satellite synthetic aperture radar interferometry (InSAR) measurements. In many glacier environments, the steady-state vertical velocity component required to balance the annual ablation rate is 5-10m a-1 or more.This indicates that the SPFassumption may be problematic also for glaciers in steady state. Here we derive the three-dimensional surface velocity distribution of Storstrømmen by using the principle of mass conservation (MC) to combine InSAR measurements from ascending and descending satellite tracks with airborne ice-sounding radar measurement of ice thickness. The results are compared to InSAR velocities previously derived by using the SPF assumption, and to velocities obtained by in situ global positioning system (GPS) measurements. The velocities derived by using the MC principle are in better agreement with the GPS velocities than the previously calculated velocities derived with the SPFassumption.

  15. Reconstruction of past oceanographic variability in Southeast Greenland from marine sedimentary records: The influence from the Atlantic Multi-decadal Oscillation

    NASA Astrophysics Data System (ADS)

    Hansen, M. J.; Andresen, C. S.; Seidenkrantz, M.-S.; Kuijpers, A.; Nørgaard-Pedersen, N.

    2012-04-01

    The Greenland ice sheet is one of the most significant water contributors to the rising global sea level, and therefore there are concerns about its long term stability. However, prediction of its contribution to global sea-level rise is complicated by lack of knowledge about mechanisms behind ice sheet change. In particular ice streams and their interaction with components of the atmospheric and oceanic climate system needs further investigation in order to make realistic models of future sea level rise. The SEDIMICE project ('Linking sediments with ice-sheet response and glacier retreat in Southeast Greenland') investigates past outlet glacier fluctuations in Southeast Greenland. The aim is to extend the knowledge from observational time series further back in time by analysing sediment cores retrieved from fjords by outlet glaciers and from the shelf. This presentation is based on results from a core retrieved near Sermilik Fjord by Helheim Glacier. The past 6000 years of Irminger water variability on the shelf has been reconstructed by analysing sediments from a side-bassin to the through connecting Sermilik fjord with the Irminger Sea. This reconstruction shows the Late-Holocene climate deterioration and is superimposed by a centennial-scale climate variability, which at times concurs with the climate records obtained for Northwest Europe. A wavelet analysis of the high-resolution K/Ti data (indicating grainsize variability) shows that the AMO (50-70 yr quasi-periodicity) recurrently controls Irminger water variability on the shelf. These results highlight the importance of adequate representation of regional climate modes in prognostic ice-sheet models.

  16. Investigation of Firn Aquifer Structure in Southeastern Greenland Using Active Source Seismology

    NASA Astrophysics Data System (ADS)

    Montgomery, Lynn N.; Schmerr, Nicholas; Burdick, Scott; Forster, Richard R.; Koenig, Lora; Legchenko, Anatoly; Ligtenberg, Stefan; Miège, Clément; Miller, Olivia L.; Solomon, D. Kip

    2017-02-01

    In spring of 2011, a perennial storage of water was observed in the firn of the southeastern Greenland ice sheet, a region of both high snow accumulation and high melt. This aquifer is created through percolation of surface meltwater downward through the firn, saturating the pore space above the ice-firn transition. The aquifer may play a significant role in sea level rise through storage or draining freshwater into the ocean. We carried out a series of active source seismic experiments using continuously refracted P-waves and inverted the first P-arrivals using a transdimensional Bayesian approach where the depth, velocity, and number of layers are allowed to vary to identify the seismic velocities associated with the base of the aquifer. When our seismic approach is combined with a radar sounding of the water table situated at the top of the firn aquifer, we are able to quantify the volume of water present. In our study region, the base of the aquifer lies on average 27.7±2.9 m beneath the surface, with an average thickness of 11.5±5.5 m. Using a Wyllie average for porosity, we found the aquifer has an average water content of 16±8%, with considerable variation in water storage capacity along the studied east-west flow line, 40 km upstream of the Helheim glacier terminus. Between 2015 and 2016, we observed a 1-2 km uphill expansion of the aquifer system, with a site dry in summer 2015 exhibiting a water content of 530 kg m-2 in summer 2016. We estimate the volume of water stored in the aquifer across the entire region upstream of Helheim glacier to be 4.7±3.1 Gt, approximately 3% of the total water stored in firn aquifers across the Greenland ice sheet. Elucidating the volume of water stored within these recently discovered aquifers is vital for determining the hydrological structure and stability of the southeastern Greenland ice sheet.

  17. Modelling meltwater delivery to the ice-bed interface through full thickness fractures on outlet glaciers of the western Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Clason, C.; Mair, D.; Nienow, P. W.

    2010-12-01

    Dynamic response to increased supraglacial meltwater generation and subsequent influx to the subglacial hydrological system is well documented in temperate glaciers. Meltwater-enhanced acceleration of ice surface velocities, or ‘spring events’, have also more recently been observed on polythermal glaciers and outlet glaciers of the Greenland Ice Sheet (GrIS). These high velocity events may be a response to increased basal lubrication and basal water pressures when meltwater reaches the subglacial system directly through moulins. Supraglacial meltwater can provide hydrostatic stresses adequate to offset closure due to the lithostatic stress of the ice when streams intersect and enter surface crevasses. A crevasse will continue to propagate through the full ice thickness provided the meltwater head within the crevasse remains sufficient, thereby allowing this flux of meltwater to be delivered to the ice-bed interface. A spatially distributed model for prediction of full ice thickness water-driven fracture and quantification of meltwater delivered to the bed has been produced. The model consists of three major components: the first sub-routine calculates surface tensile stresses from measured ice surface velocities and identifies areas likely to contain crevassing following the Von Mises failure criteria; the second is a degree day melt model and flow routing model run using measured meteorological inputs; the third sub-routine calculates crevasse penetration depths using an established linear elastic fracture mechanics model for propagation of water-filled fractures. The daily outputs of melt modelling weight routing of meltwater across the ice surface, and in turn determine the discharge into crevasses. This allows the supraglacial meltwater head, and thus fracture propagation speed, to vary daily within crevasse depth modelling. The temporal resolution of the model also allows the evolution of moulin formation through the ablation season to be captured. We

  18. Heat, salt, and freshwater budgets for a glacial fjord in Greenland

    NASA Astrophysics Data System (ADS)

    Jackson, R. H.; Straneo, F.

    2015-12-01

    Fjords link the ocean and outlet glaciers of the Greenland ice sheet. As the ice sheet loses mass - potentially triggered by submarine melting - measurements of ocean heat transport in fjords are increasingly being used to diagnose submarine melting and freshwater fluxes. The full budgets that underlie such methods, however, have been largely neglected. Here, we present complete heat, salt, and mass budgets for glacial fjords and new equations for inferring the freshwater fluxes of submarine melting and runoff. Building on estuarine studies of salt budgets, this method includes a decomposition of the fjord transports (into barotropic, exchange, and fluctuating components) that is crucial for conserving mass in the budgets and appropriately accounting for temporal variability. These methods are applied to moored records from Sermilik Fjord, near the terminus of Helheim Glacier, to evaluate the dominant balances in the fjord budgets and to estimate freshwater fluxes. We find two different regimes seasonally that align with the seasonal variations in fjord drivers: shelf variability from barrier winds and freshwater forcing. Our results highlight many important components of fjord budgets, particularly iceberg melting, heat/salt storage and barotropic fluxes, that have been neglected in previous estimates of submarine melting.

  19. Elastic and viscoelastic crustal deformations in Greenland due to ice mass changes

    NASA Astrophysics Data System (ADS)

    Khan, S. A.; Wahr, J.; Dam, T. V.; Larson, K. M.; Francis, O.; Leuliette, E. W.; Hamilton, G. S.; Stearns, L. A.

    2007-12-01

    We analyze data from ~10 continuous Global Positioning System (GPS) receivers and one tide gauge, all located along the edge of the Greenland ice sheet, to determine vertical uplift rates. We compare our results with predictions based on the ICE-5G deglaciation model of Peltier [2004]. Results from the GPS receiver at Kellyville and from the tide gauge at Nuuk, indicate that ICE-5G overestimates the subsidence rates at those locations by 1-2 mm/yr. Kellyville and Nuuk are located along the southwestern margin of the Greenland ice sheet, and the observed negative uplift rates are consistent with independent evidence that the ice margin along the southwestern edge readvanced during the last ~8 kyrs years to its current position. The ICE-5G glaciation- deglaciation history includes a readvance between the latitudes of 62 N and 72 N. The GPS measurements suggest the ICE-5G readvance may be too large. Our GPS results at Qaqortoq, located at the southern tip of Greenland, suggest a secular uplift rate of about -1 mm/yr, while ICE-5G predicts an uplift rate of 1 mm/yr. ICE-5G assumes no ice sheet readvance in south Greenland, including no readvance of the Qassimiut lobe (located at the southern tip of greenalnd) . The difference of 2 mm/yr can tentatively be explained as due to a ~60 km readvance of the Qassimiut lobe during the last ~3 kyrs. For the other GPS sites, the observed/predicted uplift rates are 3/-2 mm/yr at Kulusuk and indicate that ICE-5G does not exactly reproduce the correct rebound signal at those locations. The larger difference at Kulusuk, however, is probably due to the Earth's elastic response to ongoing changes in ice. The Kulusuk receiver is only ~90 km from the front of the Helheim glacier, where recent remote sensing observations have shown major periods of speedup between 2000 and 2005 [Howat et al., 2005] and thinning of the glacier by over 40 m from 2001 to 2003. We also analyze data from four continuous GPS receivers located between 0-150 km

  20. Northern Greenland

    NASA Image and Video Library

    2008-09-16

    The northernmost land in the world is located in Pearyland, Greenland, at a latitude of 83 degrees, 39.6 minutes. This is a land of permanent snows, glaciers, and 24-hours of daylight during the summer months. The ASTER image was acquired May 17, 2003, covers an area of 47.9 x 42.1 km, and is located at 83.6 degrees north latitude, 33.4 degrees west longitude. http://photojournal.jpl.nasa.gov/catalog/PIA11169

  1. Field Measurements and Modeling of the Southeast Greenland Firn Aquifer

    NASA Astrophysics Data System (ADS)

    Miller, O. L.; Solomon, D. K.; Miège, C.; Voss, C. I.; Koenig, L.; Forster, R. R.; Schmerr, N. C.; Montgomery, L. N.; Legchenko, A.; Ligtenberg, S.

    2016-12-01

    An extensive firn aquifer forms in southeast Greenland as surface meltwater percolates through the upper seasonal snow and firn layers to depth and saturates open pore spaces. The firn aquifer is found at depths from about 10 to 35 m below the snow surface in areas with high accumulation rates and high melt rates. The firn aquifer retains significant volume of meltwater and heat within the ice sheet. The first-ever hydrologic and geochemical measurements from several boreholes drilled into the aquifer have been made 50 km upstream of Helheim Glacier terminus in SE Greenland. This field data is used with a version of the SUTRA groundwater simulator that represents the freeze/thaw process to model the hydrologic and thermal conditions of the ice sheet, including aquifer water recharge, lateral flow, and discharge. Meltwater generation during the summer season is modeled using degree day methods, and meltwater recharge to the aquifer (10-70 cm/year) is calculated using water level fluctuations and volumetric flow measurements (3e-7 to 5e-6 m3/s). Aquifer hydrologic parameters, including hydraulic conductivity (2e-5 to 4e -4 m/s), storativity, and specific discharge (3e-7 to 5e-6 m/s), are estimated from aquifer pumping tests and tracer experiments. In situ measurements were obtained using a novel heated piezometer, which advances downward through the unsaturated and saturated zones of the aquifer by melting the surrounding firn. Innovative modeling approaches blending unsaturated and saturated groundwater flow modeling and ice thermodynamics indicate the importance of surface topography controls on fluid flow within the aquifer, and forecast the nature and volume of aquifer water discharge into crevasses at the edge of the ice sheet. This pioneering study is crucial to understanding the aquifer's influence on mass balance estimates of the ice sheet.

  2. Gyldenlove Glacier

    NASA Image and Video Library

    2017-09-27

    On April 11, 2011, IceBridge finally got the clear weather necessary to fly over glaciers in southeast Greenland. But with clear skies came winds of up to 70 knots, which made for a bumpy ride over the calving front of glaciers like Gyldenlove. Operation IceBridge, now in its third year, makes annual campaigns in the Arctic and Antarctic where science flights monitor glaciers, ice sheets and sea ice. Credit: NASA/GSFC/Michael Studinger To learn more about Ice Bridge go to: www.nasa.gov/mission_pages/icebridge/news/spr11/index.html NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Join us on Facebook

  3. Greenland Coast in Holiday Colors

    NASA Image and Video Library

    2003-12-23

    Vibrant reds, emerald greens, brilliant whites, and pastel blues adorn this view of the area surrounding the Jakobshavn Glacier on the western coast of Greenland captured by NASA Terra spacecraft on June 18, 2003.

  4. Northern Greenland

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The northernmost land in the world is located in Pearyland, Greenland, at a latitude of 83 degrees, 39.6 minutes. This is a land of permanent snows, glaciers, and 24-hours of daylight during the summer months. The ASTER image was acquired May 17, 2003, covers an area of 47.9 x 42.1 km, and is located at 83.6 degrees north latitude, 33.4 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  5. The Subglacial Access and Fast Ice Research Experiment (SAFIRE): 2. Preliminary outcomes from hot-water drilling and borehole instrumentation on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Doyle, Samuel; Hubbard, Bryn; Christoffersen, Poul; Young, Tun Jan; Hofstede, Coen; Todd, Joe; Bougamont, Marion; Hubbard, Alun

    2015-04-01

    As part of the SAFIRE research programme, pressurised hot water was used to drill four 603-616 m-long boreholes to the bed of the Greenland Ice Sheet at a site located 30 km from the calving front of marine-terminating Store Glacier (70° N, ~1000 m elevation). Despite the boreholes freezing within hours, 4 wired sensor strings were successfully deployed in three of the boreholes. These included a thermistor string to obtain the englacial temperature profile installed in the same borehole as a string of tilt sensors to measure borehole deformation, and two sets of water pressure, electrical conductivity and turbidity sensors installed just above the bed in separate, adjacent boreholes. The boreholes made a strong hydrological connection to the bed during drilling, draining rapidly to ~80 m below the ice surface. The connection of subsequent boreholes was observed as a perturbation in water pressure and temperature recorded in neighbouring boreholes, indicating an effective hydrological sub- or en-glacial connection between them. The short (week long) records obtained from these sensors in summer 2014 tentatively reveal (i) water pressure varying diurnally close to overburden albeit of a small magnitude (~0.3 m H2O), (ii) a minimum extrapolated englacial temperature of -21° C, (iii) and thermistors in the lowest 10 m of the borehole recorded temperatures above the pressure melting point indicating the presence of water. Data loggers were left running and longer records should become available in the near future. Differential drilling and instrument installation depths together with observations of discrete, diurnal turbidity events provisionally suggest the presence of sediment at the bed. These preliminary borehole observations will be complemented by GPS measurements of ice motion, meteorological data, and seismic and radar surveys to be undertaken over the next two years.

  6. Greenland's Biggest Losers

    NASA Astrophysics Data System (ADS)

    Box, J. E.; Hubbard, A.; Howat, I. M.; Csatho, B. M.; Decker, D. T.; Bates, R.; Tulaczyk, S. M.

    2010-12-01

    On 4 August, 2010, 275 square km of the front of the floating Petermann Glacier, far northwest Greenland, broke away. The glacier effectively retreated 15 km. Petermann has retreated 21 km since year 2000. Consulting available imagery, publications, and maps spanning the past century, we conclude that this is a retreat to a minimum extent in the observational record. This glacier is not the only ice are loser in Greenland. GRACE observations verify the concern of increased mass budget deficit. Retreat is ongoing at the 110 km wide Humboldt glacier and at the 23 km wide Zachariae ice stream. Humboldt, Zachariae, and Petermann (16 km wide) are among a handful of large marine-terminating outlets that have bedrock trenches that lead inland below sea level to the thick, interior reservoir of the ice sheet. Sleeping giants are awakening. Our area change survey of the 35 widest Greenland outlets indicates an annual marine-terminating glacier area loss rate in excess of 130 sq km per year. Here, we evaluate in this context the mechanisms for marine-terminating glacier retreat, dynamical responses to calving, and the apparent climate forcings. The work thus consults a suite of data sets, including: long-term meteorological station records; satellite-derived sea and land surface temperatures; satellite-derived sea ice extent; regional climate model output; oceanographic casts; time lapse cameras, surface elevation change, and tidal records. Cumulative area change at Greenland’s glacier top 5 “losers”. 2010 areas are measured ~1 month prior to the end of summer melt when the survey usually is made . We do not expect 2010 area changes to be much different using the future data. If anything, we expect the losses to be larger. Click here for a full resolution graphic.

  7. The Glaciers of HARMONIE

    NASA Astrophysics Data System (ADS)

    Mottram, Ruth; Gleeson, Emily; Pagh Nielsen, Kristian

    2016-04-01

    Developed by the large ALADIN-HIRLAM consortium, the numerical weather prediction (NWP) model system HARMONIE is run by a large number of national weather services and research institutions in Europe, the Middle East and North Africa for weather forecasting. It is now being adopted for climate research purposes as a limited area model in a form known as HCLIM. It is currently run for a number of domains, mostly in Europe but also including Greenland, at a very high resolution (~2.5 km). HARMONIE is a convection permitting non-hydrostatic model that includes the multi-purpose SURFEX surface model. By improving the characterization of glacier surfaces within SURFEX we show that weather forecast errors over both the Greenland ice sheet and over Icelandic glaciers can be significantly reduced. The improvements also facilitate increasingly accurate ice melt and runoff computations, which are important both for ice surface mass balance estimations and hydropower forecasting. These improvements will also benefit the operational HARMONIE domains that cover the Svalbard archipelago, the Alps and the Scandinavian mountain glaciers. Future uses of HCLIM for these regions, where accurately characterizing glacial terrain will be crucial for climate and glaciological applications, are also expected to benefit from this improvement. Here, we report the first results with a new glacier surface scheme in the HARMONIE model, validated with observations from the PROMICE network of automatic weather stations in Greenland. The scheme upgrades the existing surface energy balance over glaciers by including a new albedo parameterization for bare glacier ice and appropriate coefficients for calculating the turbulent fluxes. In addition the snow scheme from the SURFEX land surface module has been upgraded to allow the retention and refreezing of meltwater in the snowpack. These changes allow us to estimate surface mass balance over glaciers at a range of model resolutions that can take full

  8. Seasonal and interannual evolution of Jakobshavn Isbrae, Greenland from a 2008-2015 high-res DEM and velocity time series

    NASA Astrophysics Data System (ADS)

    Shean, D. E.; Joughin, I.; Smith, B.; Floricioiu, D.

    2015-12-01

    Greenland's large marine-terminating outlet glaciers have displayed marked retreat, speedup, and thinning in recent decades. Jakobshavn Isbrae, one of Greenland's largest outlet glaciers, has retreated ~15 km, accelerated ~150%, and thinned ~200 m since the early 1990s. Here, we present a comprehensive analysis of high-resolution elevation (~2-5 m/px) and velocity (~100 m/px) time series with dense temporal coverage (daily-monthly). The Jakobshavn DEM time series consists of >70 WorldView-1/2/3 stereo DEMs and >11 TanDEM-X DEMs spanning 2008-2015. Complementary point elevation data from Operation IceBridge (ATM, LVIS), pre-IceBridge ATM flights, and ICESat-1 GLAS extend the surface elevation record to 1999 and provide essential absolute control data, enabling sub-meter horizontal/vertical accuracy for gridded DEMs. Velocity data are primarily derived from TerraSAR-X/TanDEM-X image pairs with 11-day interval from 2009-2015. These elevation and velocity data capture outlet glacier evolution with unprecedented detail during the post-ICESat era. The lower trunk of Jakobshavn displays significant seasonal velocity variations, with recent rates of ~8 km/yr during winter and >17 km/yr during summer. DEM data show corresponding seasonal elevation changes of -30 to -45 m in summer and +15 to +20 m in winter, with decreasing magnitude upstream. Seasonal discharge varies from ~30-35 Gt/yr in winter to ~45-55 Gt/yr in summer, and we integrate these measurements for improved long-term mass-balance estimates. Recent interannual trends show increased discharge, velocity, and thinning (-15 to -20 m/yr), which is consistent with long-term altimetry records. The DEM time series also reveal new details about calving front and mélange evolution during the seasonal cycle. Similar time series are available for Kangerdlugssuaq and Helheim Glaciers. These observations are improving our understanding of outlet glacier dynamics, while complementing ongoing efforts to constrain estimates

  9. South Greenland, North Atlantic Ocean

    NASA Image and Video Library

    1992-04-02

    This spectacular north looking view of south Greenland (62.0N, 46.0W) shows numerous indentations along the coastline, many of which contain small settlements. These indentations are fiords carved by glaciers of the last ice age. Even today, ice in the center of Greenland is as much as 10,000 ft. thick and great rivers of ice continuously flow toward the sea, where they melt or break off as icebergs - some of which may be seen floating offshore.

  10. South Greenland, North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This spectacular north looking view of south Greenland (62.0N, 46.0W) shows numerous indentations along the coastline, many of which contain small settlements. These indentations are fiords carved by glaciers of the last ice age. Even today, ice in the center of Greenland is as much as 10,000 ft. thick and great rivers of ice continuously flow toward the sea, where they melt or break off as icebergs - some of which may be seen floating offshore.

  11. Baffin Bay, Greenland

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Along Greenland's western coast, a small field of glaciers surrounds Baffin Bay. This image was acquired by Landsat 7's Enhanced Thematic Mapper plus (ETM+) sensor on September 3, 2000. This is a false-color composite image made using near-infrared, red, and blue wavelengths. The image has also been sharpened using the sensor's panchromatic band. Image provided by the USGS EROS Data Center Satellite Systems Branch

  12. The length of the glaciers in the world - a straightforward method for the automated calculation of glacier center lines

    NASA Astrophysics Data System (ADS)

    Machguth, H.; Huss, M.

    2014-05-01

    Glacier length is an important measure of glacier geometry but global glacier inventories are mostly lacking length data. Only recently semi-automated approaches to measure glacier length have been developed and applied regionally. Here we present a first global assessment of glacier length using a fully automated method based on glacier surface slope, distance to the glacier margins and a set of trade-off functions. The method is developed for East Greenland, evaluated for the same area as well as for Alaska, and eventually applied to all ∼200 000 glaciers around the globe. The evaluation highlights accurately calculated glacier length where DEM quality is good (East Greenland) and limited precision on low quality DEMs (parts of Alaska). Measured length of very small glaciers is subject to a certain level of ambiguity. The global calculation shows that only about 1.5% of all glaciers are longer than 10 km with Bering Glacier (Alaska/Canada) being the longest glacier in the world at a length of 196 km. Based on model output we derive global and regional area-length scaling laws. Differences among regional scaling parameters appear to be related to characteristics of topography and glacier mass balance. The present study adds glacier length as a central parameter to global glacier inventories. Global and regional scaling laws might proof beneficial in conceptual glacier models.

  13. 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.

  14. Temporal and spatial variability of the Greenland firn aquifer revealed by ground and airborne radar data

    NASA Astrophysics Data System (ADS)

    Miège, C.; Forster, R. R.; Koenig, L.; Brucker, L.; Box, J. E.; Burgess, E. W.; Solomon, D. K.

    2014-12-01

    During the last two decades, the Greenland ice sheet has been losing mass, significantly contributing to sea level rise (0.33±0.08 mm yr-1). In the meantime, summer surface melt has been increasing in both duration and extent, and subsequent runoff represents about half of the total mass lost. However, small-scale heterogeneous physical processes and residence times associated with meltwater formation, infiltration in the firn, refreezing and/or runoff remain unconstrained in coarser resolution numerical models, leading to significant error bars while estimating total runoff. In Southeast and South Greenland, widespread aquifers have been observed in relative high accumulation and melt regions, persisting throughout the year, storing a significant mass of water within the firn. The presence of a persistent water table within the firn aquifer is observed using a 400 MHz ground-penetrating radar and the 750 MHz airborne Accumulation Radar over the same location. In both radar echograms, a strong reflection is present, illustrating the important dielectric contrast between dry firn and water-saturated firn. Since 2011, NASA's Operation IceBridge mission allows us to produce an ice-sheet-wide map of the location and depth of the firn aquifer using the Accumulation Radar echograms. Over the last four years, from one spring to the next, repeated flight lines demonstrate a relatively steady short-term behavior of water in the aquifer with constant lateral boundaries (with a few exceptions) and water table surface. An earlier radar survey (1993) implies the aquifer presence by lack of bed return, but the study area was limited to the Helheim Glacier region. Within the aquifer, a relatively slow flow of water is inferred from 2-D hydrological flow modeling, while assuming a constant hydraulic conductivity in the aquifer. On the aquifer low-elevation lateral boundary, connection with crevasses are observed in the airborne radar echograms and documented in this study. More

  15. The length of the world's glaciers - a new approach for the global calculation of center lines

    NASA Astrophysics Data System (ADS)

    Machguth, H.; Huss, M.

    2014-09-01

    Glacier length is an important measure of glacier geometry. Nevertheless, global glacier inventories are mostly lacking length data. Only recently semi-automated approaches to measure glacier length have been developed and applied regionally. Here we present a first global assessment of glacier length using an automated method that relies on glacier surface slope, distance to the glacier margins and a set of trade-off functions. The method is developed for East Greenland, evaluated for East Greenland as well as for Alaska and eventually applied to all ~ 200 000 glaciers around the globe. The evaluation highlights accurately calculated glacier length where digital elevation model (DEM) quality is high (East Greenland) and limited accuracy on low-quality DEMs (parts of Alaska). Measured length of very small glaciers is subject to a certain level of ambiguity. The global calculation shows that only about 1.5% of all glaciers are longer than 10 km, with Bering Glacier (Alaska/Canada) being the longest glacier in the world at a length of 196 km. Based on the output of our algorithm we derive global and regional area-length scaling laws. Differences among regional scaling parameters appear to be related to characteristics of topography and glacier mass balance. The present study adds glacier length as a key parameter to global glacier inventories. Global and regional scaling laws might prove beneficial in conceptual glacier models.

  16. North and northeast Greenland ice discharge from satellite radar interferometry

    SciTech Connect

    Rignot, E.J.; Gogineni, S.P.; Krabill, W.B.

    1997-05-09

    Ice discharge from north and northeast Greenland calculated from satellite radar interferometry data of 14 outlet glaciers is 3.5 times that estimated from iceberg production. The satellite estimates, obtained at the grounding line of the outlet glaciers, differ from those obtained at the glacier front, because basal melting is extensive at the underside of the floating glacier sections. The results suggest that the north and northeast parts of the Greenland ice sheet may be thinning and contributing positively to sea-level rise. 24 refs., 3 figs., 1 tab.

  17. North and Northeast Greenland Ice Discharge from Satellite Radar Interferometry

    NASA Technical Reports Server (NTRS)

    Rignot, E. J.; Gogineni, S. P.; Krabill, W. B.; Ekholm, S.

    1997-01-01

    Ice discharge from north and northeast Greenland calculated from satellite radar interferometry data of 14 outlet glaciers is 3.5 times that estimated from iceberg production. The satellite estimates, obtained at the grounding line of the outlet glaciers, differ from those obtained at the glacier front, because basal melting is extensive at the underside of the floating glacier sections. The results suggest that the north and northeast parts of the Greenland ice sheet may be thinning and contributing positively to sea-level rise.

  18. North and Northeast Greenland Ice Discharge from Satellite Radar Interferometry

    NASA Technical Reports Server (NTRS)

    Rignot, E. J.; Gogineni, S. P.; Krabill, W. B.; Ekholm, S.

    1997-01-01

    Ice discharge from north and northeast Greenland calculated from satellite radar interferometry data of 14 outlet glaciers is 3.5 times that estimated from iceberg production. The satellite estimates, obtained at the grounding line of the outlet glaciers, differ from those obtained at the glacier front, because basal melting is extensive at the underside of the floating glacier sections. The results suggest that the north and northeast parts of the Greenland ice sheet may be thinning and contributing positively to sea-level rise.

  19. Malaspina Glacier, Alaska

    NASA Image and Video Library

    2017-09-28

    The ice of a piedmont glacier spills from a steep valley onto a relatively flat plain, where it spreads out unconstrained like pancake batter. Elephant Foot Glacier in northeastern Greenland is an excellent example; it is particularly noted for its symmetry. But the largest piedmont glacier in North America (and possibly the world) is Malaspina in southeastern Alaska. On September 24, 2014, the Operational Land Imager (OLI) on Landsat 8 acquired this image of Malaspina Glacier. The main source of ice comes from Seward Glacier, located at the top-center of this image. The Agassiz and Libbey glaciers are visible on the left side, and the Hayden and Marvine glaciers are on the right. The brown lines on the ice are moraines—areas where soil, rock, and other debris have been scraped up by the glacier and deposited at its sides. Where two glaciers flow together, the moraines merge to form a medial moraine. Glaciers that flow at a steady speed tend to have moraines that are relatively straight. But what causes the dizzying pattern of curves, zigzags, and loops of Malaspina’s moraines? Glaciers in this area of Alaska periodically “surge,”meaning they lurch forward quickly for one to several years. As a result of this irregular flow, the moraines at the edges and between glaciers can become folded, compressed, and sheared to form the characteristic loops seen on Malaspina. For instance, a surge in 1986 displaced moraines on the east side of Malaspina by as much as 5 kilometers (3 miles). NASA Earth Observatory image by Jesse Allen, using Landsat data from the U.S. Geological Survey. Caption by Kathryn Hansen. Credit: NASA Earth Observatory NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission

  20. Nuuk, Greenland

    NASA Image and Video Library

    2008-05-23

    Nuuk or Gadthab is the capital and largest city of Greenland. It is located at the mouth of the Nuup Kangerlua inlet on the west coast of Greenland. This image was acquired August 2, 2004 by NASA Terra spacecraft.

  1. Changes in the velocity structure of the Greenland Ice Sheet.

    PubMed

    Rignot, Eric; Kanagaratnam, Pannir

    2006-02-17

    Using satellite radar interferometry observations of Greenland, we detected widespread glacier acceleration below 66 degrees north between 1996 and 2000, which rapidly expanded to 70 degrees north in 2005. Accelerated ice discharge in the west and particularly in the east doubled the ice sheet mass deficit in the last decade from 90 to 220 cubic kilometers per year. As more glaciers accelerate farther north, the contribution of Greenland to sea-level rise will continue to increase.

  2. Evolution of Crevasses Fed by Water from the East Greenland Firn Aquifer

    NASA Astrophysics Data System (ADS)

    Poinar, K.; Joughin, I. R.; Lilien, D.; Brucker, L.; Kehrl, L. M.; Nowicki, S.

    2016-12-01

    A firn aquifer in the Helheim Glacier area of East Greenland lies directly upstream of a crevasse field. New meltwater enters this firn aquifer annually and is thought to displace aquifer water into the crevasses; however, it is not known whether the crevasses carry the water to the bed or refreeze it entirely within the ice sheet. We investigate the englacial drainage of the firn-aquifer water using a thermo-visco-elastic model for the propagation of water-filled crevasses. The model calculates crevasse shape, depth, and refreezing rates as a function of water input, which we take from existing field measurements of the water flux through the aquifer, and the local stress and temperature fields. We validate our model output with data from the Airborne Topographic Mapper, which reveals the near-surface geometry of the crevasses. We find that meltwater available at the ice-sheet surface can initially drive the crevasses to the top of the firn aquifer at 15 meters depth. After tapping the aquifer, the modeled crevasses receive a steady and sizable influx of water, which causes them to penetrate 1000 meters to the bed below within 20-300 days. This wide range results from our relatively poor constraints on the water flux through the aquifer and on the shear modulus of Greenland ice. Not all combinations of these parameters cause crevasses to reach the bed. Crevasses that do reach the bed refreeze approximately 2-10% of their water, raising the average local ice temperature by approximately 1°C and enhancing deformational ice motion by 5%. We find that the crevasse field downstream of the firn aquifer likely allows a large fraction of the surface-sourced aquifer water to reach the bed. Thus, future studies should consider the aquifer and crevasses as part of a common system. This system may play an important role in ice-sheet dynamics by routing to the bed a continuous high volume of water that could channelize a distributed basal hydrologic system.

  3. NASA OMG Mission Maps Sea Floor Depth off Greenland Coast

    NASA Image and Video Library

    2016-03-08

    This image shows a region of the sea floor off the coast of northwest Greenland mapped as part of NASA Oceans Melting Greenland OMG mission. The data shown here will be used to understand the pathways by which warm water can reach glacier edges.

  4. Bibliography of glacier studies by the U.S. Geological Survey

    USGS Publications Warehouse

    Snyder, E.F.

    1996-01-01

    Reports on glaciers written by U.S. Geological Survey members between 1896 and early 1996 are listed. The reports contain information about glacier and had at least one USGS author or was dependent on USGS data or projects. Extensive glacier studies have been done by the USGS in North America, Greenland, Iceland, as well as in Antarctica.

  5. Glaciers and Sea Level Rise

    NASA Image and Video Library

    2017-09-28

    Peripheral glaciers and ice caps (isolated from the main ice sheet, which is seen in the upper right section of the image) in eastern Greenland. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Frank Paul, University of Zurich NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  6. Investigating the Greenland ice sheet evolution under changing climate using a three-dimensional full-Stokes model

    NASA Astrophysics Data System (ADS)

    Seddik, H.; Greve, R.; Zwinger, T.; Gillet-Chaulet, F.; Gagliardini, O.

    2010-12-01

    A three-dimensional, thermo-mechanically coupled model is applied to the Greenland ice sheet. The model implements the full-Stokes equations for the ice dynamics, and the system is solved with the finite-element method (FEM) using the open source multi-physics package Elmer (http://www.csc.fi/elmer/). The finite-element mesh for the computational domain has been created using the Greenland surface and bedrock DEM data with a spatial resolution of 5 km (SeaRise community effort, based on Bamber and others, 2001). The study is particularly aimed at better understanding the ice dynamics near the major Greenland ice streams. The meshing procedure starts with the bedrock footprint where a mesh with triangle elements and a resolution of 5 km is constructed. Since the resulting mesh is unnecessarily dense in areas with slow ice dynamics, an anisotropic mesh adaptation procedure has been introduced. Using the measured surface velocities to evaluate the Hessian matrix of the velocities, a metric tensor is computed at the mesh vertices in order to define the adaptation scheme. The resulting meshed footprint obtained with the automatic tool YAMS shows a high density of elements in the vicinities of the North-East Greenland Ice Stream (NEGIS), the Jakobshavn ice stream (JIS) and the Kangerdlugssuaq (KL) and Helheim (HH) glaciers. On the other hand, elements with a coarser resolution are generated away from the ice streams and domain margins. The final three-dimensional mesh is obtained by extruding the 2D footprint with 21 vertical layers, so that the resulting mesh contains 400860 wedge elements and 233583 nodes. The numerical solution of the Stokes and the heat transfer equations involves direct and iterative solvers depending on the simulation case, and both methods are coupled with stabilization procedures. The boundary conditions are such that the temperature at the surface uses the present-day mean annual air temperature given by a parameterization or directly from the

  7. Arctic polynya and glacier interactions

    NASA Astrophysics Data System (ADS)

    Edwards, Laura

    2013-04-01

    Major uncertainties surround future estimates of sea level rise attributable to mass loss from the polar ice sheets and ice caps. Understanding changes across the Arctic is vital as major potential contributors to sea level, the Greenland Ice Sheet and the ice caps and glaciers of the Canadian Arctic archipelago, have experienced dramatic changes in recent times. Most ice mass loss is currently focused at a relatively small number of glacier catchments where ice acceleration, thinning and calving occurs at ocean margins. Research suggests that these tidewater glaciers accelerate and iceberg calving rates increase when warming ocean currents increase melt on the underside of floating glacier ice and when adjacent sea ice is removed causing a reduction in 'buttressing' back stress. Thus localised changes in ocean temperatures and in sea ice (extent and thickness) adjacent to major glacial catchments can impact hugely on the dynamics of, and hence mass lost from, terrestrial ice sheets and ice caps. Polynyas are areas of open water within sea ice which remain unfrozen for much of the year. They vary significantly in size (~3 km2 to > ~50,000 km2 in the Arctic), recurrence rates and duration. Despite their relatively small size, polynyas play a vital role in the heat balance of the polar oceans and strongly impact regional oceanography. Where polynyas develop adjacent to tidewater glaciers their influence on ocean circulation and water temperatures may play a major part in controlling subsurface ice melt rates by impacting on the water masses reaching the calving front. Areas of open water also play a significant role in controlling the potential of the atmosphere to carry moisture, as well as allowing heat exchange between the atmosphere and ocean, and so can influence accumulation on (and hence thickness of) glaciers and ice caps. Polynya presence and size also has implications for sea ice extent and therefore potentially the buttressing effect on neighbouring

  8. Drainage of Southeast Greenland firn aquifer water through crevasses to the bed

    NASA Astrophysics Data System (ADS)

    Poinar, Kristin; Joughin, Ian; Lilien, David; Brucker, Ludovic; Kehrl, Laura; Nowicki, Sophie

    2017-02-01

    A firn aquifer in the Helheim Glacier catchment of Southeast Greenland lies directly upstream of a crevasse field. Previous measurements show that a 3.5-km long segment of the aquifer lost a large volume of water (26,000 - 65,000 m2 in cross section) between spring 2012 and spring 2013, compared to annual meltwater accumulation of 6000 - 15,000 m2. The water is thought to have entered the crevasses, but whether the water reached the bed or refroze within the ice sheet is unknown. We used a thermo-visco-elastic model for crevasse propagation to calculate the depths and volumes of these water-filled crevasses. We compared our model output to data from the Airborne Topographic Mapper (ATM), which reveals the near-surface geometry of specific crevasses, and WorldView images, which capture the surface expressions of crevasses across our 1.5-km study area. We found a best fit with a shear modulus between 0.2 and 1.5 GPa within our study area. We show that surface meltwater can drive crevasses to the top surface of the firn aquifer ( 20 m depth), whereupon it receives water at rates corresponding to the water flux through the aquifer. Our model shows that crevasses receiving firn-aquifer water hydrofracture through to the bed, 1000 m below, in 10-40 days. Englacial refreezing of firn-aquifer water raises the average local ice temperature by 4°C over a ten-year period, which enhances deformational ice motion by 50 m/yr, compared to the observed surface velocity of 200 m/yr. The effect of the basal water on the sliding velocity remains unknown. Were the firn aquifer not present to concentrate surface meltwater into crevasses, we find that no surface melt would reach the bed; instead, it would refreeze annually in crevasses at depths <500 m. The crevasse field downstream of the firn aquifer likely allows a large fraction of the aquifer water in our study area to reach the bed. Thus, future studies should consider the aquifer and crevasses as part of a common system. This

  9. Tropical Glaciers

    NASA Astrophysics Data System (ADS)

    Fountain, Andrew

    The term "tropical glacier" calls to mind balmy nights and palm trees on one hand and cold, blue ice on the other. Certainly author Gabriel Garcia Marqez exploited this contrast in One Hundred Years of Solitude. We know that tropical fish live in warm, Sun-kissed waters and tropical plants provide lush, dense foliage populated by colorful tropical birds. So how do tropical glaciers fit into this scene? Like glaciers everywhere, tropical glaciers form where mass accumulation—usually winter snow—exceeds mass loss, which is generally summer melt. Thus, tropical glaciers exist at high elevations where precipitation can occur as snowfall exceeds melt and sublimation losses, such as the Rwenzori Mountains in east Africa and the Maoke Range of Irian Jaya.

  10. Hinge-line Migration of Petermann Gletscher, North Greenland, Detected Using Satellite Radar Interferometry

    NASA Technical Reports Server (NTRS)

    Rignot, Eric

    1998-01-01

    The synthetic-aperture radar interferometry technique is used to detect the migration of the limit of tidal flexing, or hinge line, of the floating ice tongue of Petermann Gletscher, a major outlet glacier of north Greenland.

  11. Hinge-line Migration of Petermann Gletscher, North Greenland, Detected Using Satellite Radar Interferometry

    NASA Technical Reports Server (NTRS)

    Rignot, Eric

    1998-01-01

    The synthetic-aperture radar interferometry technique is used to detect the migration of the limit of tidal flexing, or hinge line, of the floating ice tongue of Petermann Gletscher, a major outlet glacier of north Greenland.

  12. Laser altimetry reveals complex pattern of Greenland Ice Sheet dynamics.

    PubMed

    Csatho, Beata M; Schenk, Anton F; van der Veen, Cornelis J; Babonis, Gregory; Duncan, Kyle; Rezvanbehbahani, Soroush; van den Broeke, Michiel R; Simonsen, Sebastian B; Nagarajan, Sudhagar; van Angelen, Jan H

    2014-12-30

    We present a new record of ice thickness change, reconstructed at nearly 100,000 sites on the Greenland Ice Sheet (GrIS) from laser altimetry measurements spanning the period 1993-2012, partitioned into changes due to surface mass balance (SMB) and ice dynamics. We estimate a mean annual GrIS mass loss of 243 ± 18 Gt ⋅ y(-1), equivalent to 0.68 mm ⋅ y(-1) sea level rise (SLR) for 2003-2009. Dynamic thinning contributed 48%, with the largest rates occurring in 2004-2006, followed by a gradual decrease balanced by accelerating SMB loss. The spatial pattern of dynamic mass loss changed over this time as dynamic thinning rapidly decreased in southeast Greenland but slowly increased in the southwest, north, and northeast regions. Most outlet glaciers have been thinning during the last two decades, interrupted by episodes of decreasing thinning or even thickening. Dynamics of the major outlet glaciers dominated the mass loss from larger drainage basins, and simultaneous changes over distances up to 500 km are detected, indicating climate control. However, the intricate spatiotemporal pattern of dynamic thickness change suggests that, regardless of the forcing responsible for initial glacier acceleration and thinning, the response of individual glaciers is modulated by local conditions. Recent projections of dynamic contributions from the entire GrIS to SLR have been based on the extrapolation of four major outlet glaciers. Considering the observed complexity, we question how well these four glaciers represent all of Greenland's outlet glaciers.

  13. Mass-balance characteristics of arctic glaciers

    NASA Astrophysics Data System (ADS)

    Braithwaite, Roger J.

    A survey of available mass-balance data shows that glaciers on arctic islands, i.e. mountain glaciers and ice caps in northern Canada, Greenland, Svalbard and the Eurasian islands, share mass-balance characteristics of low annual amplitude and small interannual variability. By contrast, glaciers around the Arctic (e.g. in Alaska, Iceland, mainland Scandinavia and northern Eurasia) can have exceptionally large annual amplitude and interannual variability but otherwise share characteristics with glaciers in lower latitudes. The arctic island glaciers occur in areas with low annual precipitation and high annual temperature variability, i.e. in dry-cold or continental regions. Most glaciers surrounding the Arctic (Alaska, Iceland and Scandinavia) occur in areas with high annual precipitation and low annual temperature variability, i.e. in wet-warm or maritime regions. Earlier mass-balance modelling showed that arctic island glaciers have low sensitivity to temperature changes consistent with their low mass-balance amplitude. However, very large changes in mass balance could occur on arctic island glaciers if the sea ice surrounding the arctic islands were reduced so that the climate of the arctic islands becomes more maritime.

  14. Extensive winter subglacial water storage beneath the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Chu, Winnie; Schroeder, Dustin M.; Seroussi, Helene; Creyts, Timothy T.; Palmer, Steven J.; Bell, Robin E.

    2016-12-01

    Surface meltwater that reaches the base of the Greenland Ice Sheet exerts a fundamental impact on ice flow, but observations of catchment-wide movement and distribution of subglacial water remain limited. Using radar-sounding data from two seasons, we identify the seasonal distribution of subglacial water in western Greenland. Our analysis provides evidence of widespread subglacial water storage beneath Greenland in the wintertime. The winter storage is located primarily on bedrock ridges with higher bed elevations in excess of 200 m. During the melt season water moves to the subglacial troughs. This inverse relationship with topography indicates that the material properties of the glacier bed strongly influence subglacial drainage development. Both the spatial variations in bed properties and the initial state of the subglacial hydrology system at the start of the melt season lead to differing glacier dynamical responses to surface melting across the Greenland Ice Sheet.

  15. Warm Oceans, Fast Glaciers: the connections

    NASA Astrophysics Data System (ADS)

    Truffer, M.; Fahnestock, M. A.; Amundson, J. M.

    2009-12-01

    Over the last decade many outlet glaciers from the Greenland Ice Sheet have accelerated and thinned, and in a number of cases their termini have retreated. There is much in common from glacier to glacier that emerges as these changes are studied, yet the actual physical mechanisms remain unclear. One can show that the spatial patterns and timing of outlet glacier changes around Greenland coincide with changes in sea surface temperature and length of the sea-ice-free season in the surrounding ocean, and that large glacier changes appear to initiate within one to a few years of shifts in these conditions. While ocean warming has a direct impact on rates of melting at the glacier ice/ocean interface, its impact on ice flow is less direct. The spatial and temporal coincidence between changing ocean conditions and speedup is compelling, but the causal link between warmer ocean water and rapid responses from outlet glaciers around Greenland is more complex. Observations of rapid calving retreats, the appearance of calving-related long-period seismicity at some large glaciers undergoing change, and the loss of floating ice tongues all suggest that the direct impact of ocean-driven change is on the stability of the lowest reach of these tidewater outlets. In glaciers with a floating tongue, enhanced basal melt may be destabilizing by thinning the tongue to below its structural integrity; at grounded termini this effect is lacking. However, rapid melt at the near-vertical face can play a significant role for slowly flowing systems. For large grounded glaciers with terminus flow rates of meters per day, the impact of increased melt in summer would seem less important. At such glaciers the link between ocean temperatures, sea ice cover and terminus stability manifests itself by the cessation of calving in fall and winter, which leads to terminus advance and the formation of a floating tongue. The loss of sea ice cover in early spring leads to a disintegration of the seasonal

  16. The Greenland Ice Mapping Project

    NASA Astrophysics Data System (ADS)

    Joughin, I.; Smith, B.; Howat, I. M.; Moon, T. A.; Scambos, T. A.

    2015-12-01

    Numerous glaciers in Greenland have sped up rapidly and unpredictably during the first part of the 21st Century. We started the Greenland Ice Mapping Project (GIMP) to produce time series of ice velocity for Greenland's major outlet glaciers. We are also producing image time series to document the advance and retreat of glacier calving fronts and other changes in ice-sheet geometry (e.g., shrinking ice caps and ice shelves). When the project began, there was no digital elevation model (DEM) with sufficient accuracy and resolution to terrain-correct the SAR-derived products. Thus, we also produced the 30-m GIMP DEM, which, aside from improving our processing, is an important product in its own right. Although GIMP focuses on time series, complete spatial coverage for initializing ice sheet models also is important. There are insufficient data, however, to map the full ice sheet in any year. There is good RADARSAT coverage for many years in the north, but the C-band data decorrelate too quickly to measure velocity in the high accumulation regions of the southeast. For such regions, ALOS data usually correlate well, but speckle-tracking estimates at L-band are subject to large ionospheric artifacts. Interferometric phase data are far less sensitive to the effect of the ionosphere, but velocity estimates require results from crossing orbits. Thus, to produce a nearly complete mosaic we used data from multiple sensors, beginning with ERS-1/2 data from the mid 1990s. By using a primarily phase-only solution for much of the interior, we have reduced the velocity errors to ~1-3 m/yr. For the faster moving ice-sheet margin where phase data cannot be unwrapped, we used speckle-tracking data. In particular, we have relied on TerraSAR-X for many fast-moving glaciers because the ionosphere far less affects X-band data. This pan-Greenland velocity map as well as many of the time series would not have been possible without an extensive archive of data collected using six

  17. Glacier Swap

    NASA Image and Video Library

    2014-05-16

    ISS040-E-000298 (16 May 2014) --- NASA astronaut Steve Swanson, Expedition 40 commander, works with the General Laboratory Active Cryogenic ISS Experiment Refrigerator (GLACIER) in the Destiny laboratory of the International Space Station.

  18. Glacier Swap

    NASA Image and Video Library

    2014-05-16

    ISS040-E-000297 (16 May 2014) --- NASA astronaut Steve Swanson, Expedition 40 commander, works with the General Laboratory Active Cryogenic ISS Experiment Refrigerator (GLACIER) in the Destiny laboratory of the International Space Station.

  19. Glacier Swap

    NASA Image and Video Library

    2014-05-16

    ISS040-E-000296 (16 May 2014) --- NASA astronaut Steve Swanson, Expedition 40 commander, works with the General Laboratory Active Cryogenic ISS Experiment Refrigerator (GLACIER) in the Destiny laboratory of the International Space Station.

  20. Large Fluctuations in Speed on Jakobshavn Isbrae, Greenland

    NASA Technical Reports Server (NTRS)

    Joughin, Ian; Abdalati, Waleed; Fahnestock, Mark

    2003-01-01

    We have assembled an 18-year velocity record for Jakobshavn Isbrae, Greenland. From a 1985 speed of approx. 7000 m/yr, the glacier had slowed by approx. 1000 m/ yr in 1992, which coincided with independently observed thickening in the early 1990s . The glacier then sped up by approx. 4000 m/yr between 1997 and 2000, during which time other measurements show rapid thinning . From 2000 to 2003, the glacier s floating ice tongue almost entirely disintegrated, as speed increased to 12,600 m/yr. If the retreat of the ice tongue caused the acceleration, then similar losses of floating ice tongues since the Little Ice Age may explain the current rapid thinning observed for many of Greenland s outlet glaciers.

  1. Regional Observations of Alaska Glacier Dynamics

    NASA Astrophysics Data System (ADS)

    Burgess, E. W.; Forster, R. R.; Hall, D. K.

    2010-12-01

    Alaska glaciers contribute more to sea level rise than any other glacierized mountain region in the world. Alaska is loosing ~84 Gt of ice annually, which accounts for ~0.23 mm/yr of SLR (Luthcke et al., 2008). Complex glacier flow dynamics, frequently related to tidewater environments, is the primary cause of such rapid mass loss (Larsen et al., 2007). Indirect observations indicate these complex flow dynamics occur on many glaciers throughout Alaska, but no comprehensive velocity measurements exist. We are working to measure glacier surface velocities throughout Alaska using synthetic aperture radar (SAR) offset tracking. This work focuses on the Seward/Malaspina, Bering, Columbia, Kaskawulsh, and Hubbard Glaciers and uses a MODIS land surface temperature "melt-day" product (Hall et al., 2006, 2008) to identify potential links between velocity variability and summertime temperature fluctuations. Hall, D., R. Williams Jr., K. Casey, N. DiGirolamo, and Z. Wan (2006), Satellite-derived, melt-season surface temperature of the Greenland Ice Sheet (2000-2005) and its relationship to mass balance, Geophysical Research Letters, 33(11). Hall, D., J. Box, K. Casey, S. Hook, C. Shuman, and K. Steffen (2008), Comparison of satellite-derived and in-situ observations of ice and snow surface temperatures over Greenland, Remote Sensing of Environment, 112(10), 3739-3749. Larsen, C. F., R. J. Motyka, A. A. Arendt, K. A. Echelmeyer, and P. E. Geissler (2007), Glacier changes in southeast Alaska and northwest British Columbia and contribution to sea level rise, J. Geophys. Res. Luthcke, S., A. Arendt, D. Rowlands, J. McCarthy, and C. Larsen (2008), Recent glacier mass changes in the Gulf of Alaska region from GRACE mascon solutions, Journal of Glaciology, 54(188), 767-777.

  2. Ground penetrating radar (GPR) measurements at Mittivakkat Gletscher, Southeast Greenland

    NASA Astrophysics Data System (ADS)

    Clement Yde, Jacob; Løland, Ronny; Ruud, Henry; Mernild, Sebastian H.; Riger-Kusk, Mette; de Villiers, Simon; Tvis Knudsen, N.; Malmros, Jeppe K.

    2014-05-01

    Here, we present ground penetrating radar (GPR) measurements conducted on the surface of Mittivakkat Gletscher in Southeast Greenland (the only long-term mass balance observed glacier in Greenland) and estimate the change in ice volume over an 18 year period. Between a previous direct volume survey in 1994 and the new GPR survey in 2012, the glacier has changed its volume from 2.02 ± 0.10 to 1.50 ± 0.08 km3 while the study area has decreased from 17.6 to 15.8 km2. These results are in accordance with the cumulative mass loss observed by long-term mass balance measurements (1995/1996 - 2011/2012) at Mittivakkat Gletscher and confirms that the glacier is in severe climatic disequilibrium (AAR = 0.17). The observed volume-area scaling exponent γ and coefficient c are outside the range of global scaling parameters, but are sensitive to small uncertainties. As Mittivakkat Gletscher is generally considered as representative of glaciers in Southeast Greenland, these findings could indicate that a regional volume-area scaling approach would provide a more accurate total glacier volume estimate for Greenland than using parameters given by global scaling relationships.

  3. Greenland's Coast in Holiday Colors

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Vibrant reds, emerald greens, brilliant whites, and pastel blues adorn this view of the area surrounding the Jakobshavn Glacier on the western coast of Greenland. The image is a false-color (near-infrared, green, blue) view acquired by the Multi-angle Imaging SpectroRadiometer's nadir camera. The brightness of vegetation in the near-infrared contributes to the reddish hues; glacial silt gives rise to the green color of the water; and blue-colored melt ponds are visible in the bright white ice. A scattering of small icebergs in Disco Bay adds a touch of glittery sparkle to the scene.

    The large island in the upper left is called Qeqertarsuaq. To the east of this island, and just above image center, is the outlet of the fast-flowing Jakobshavn (or Ilulissat) glacier. Jakobshavn is considered to have the highest iceberg production of all Greenland glaciers and is a major drainage outlet for a large portion of the western side of the ice sheet. Icebergs released from the glacier drift slowly with the ocean currents and pose hazards for shipping along the coast.

    The Multi-angle Imaging SpectroRadiometer views the daylit Earth continuously and the entire globe between 82 degrees north and 82 degrees south latitude is observed every 9 days. These data products were generated from a portion of the imagery acquired on June 18, 2003 during Terra orbit 18615. The image cover an area of about 254 kilometers x 210 kilometers, and use data from blocks 34 to 35 within World Reference System-2 path 10.

    MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

  4. Greenland's Coast in Holiday Colors

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Vibrant reds, emerald greens, brilliant whites, and pastel blues adorn this view of the area surrounding the Jakobshavn Glacier on the western coast of Greenland. The image is a false-color (near-infrared, green, blue) view acquired by the Multi-angle Imaging SpectroRadiometer's nadir camera. The brightness of vegetation in the near-infrared contributes to the reddish hues; glacial silt gives rise to the green color of the water; and blue-colored melt ponds are visible in the bright white ice. A scattering of small icebergs in Disco Bay adds a touch of glittery sparkle to the scene.

    The large island in the upper left is called Qeqertarsuaq. To the east of this island, and just above image center, is the outlet of the fast-flowing Jakobshavn (or Ilulissat) glacier. Jakobshavn is considered to have the highest iceberg production of all Greenland glaciers and is a major drainage outlet for a large portion of the western side of the ice sheet. Icebergs released from the glacier drift slowly with the ocean currents and pose hazards for shipping along the coast.

    The Multi-angle Imaging SpectroRadiometer views the daylit Earth continuously and the entire globe between 82 degrees north and 82 degrees south latitude is observed every 9 days. These data products were generated from a portion of the imagery acquired on June 18, 2003 during Terra orbit 18615. The image cover an area of about 254 kilometers x 210 kilometers, and use data from blocks 34 to 35 within World Reference System-2 path 10.

    MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

  5. Progressively Communicating Rich Telemetry from Autonomous Underwater Vehicles via Relays

    DTIC Science & Technology

    2012-06-01

    The Nioghalvfjerdsfjorden Glacier , shown in Fig. 1-2, poses just such questions. The melting of Greenland ice sheets, driven by climate change...KaarinaWeckstrom, andAndreas P. Ahlstrom. Rapid response of helheim glacier in greenland to climate variability over the past century. Nature Geosci...preparing for under-ice mission . . . . . . . . . . . . . 17 1-2 Details of Nioghalvfjerdsfjorden Glacier . . . . . . . . . . . . . . . . . 18 1-3 Real

  6. Malaspina Glacier, Alaska

    NASA Image and Video Library

    2003-05-01

    Malaspina Glacier in southeastern Alaska is considered the classic example of a piedmont glacier. Piedmont glaciers occur where valley glaciers exit a mountain range onto broad lowlands, are no longer laterally confined, and spread to become wide lobes.

  7. Glacier Contributions to Sea Level Rise

    NASA Astrophysics Data System (ADS)

    Gardner, A. S.; Cogley, J. G.; Moholdt, G.; Wouters, B.; Wiese, D. N.

    2015-12-01

    Global mean sea level is rising in response to two primary factors: warming oceans and diminishing glaciers and ice sheets. If melted completely, glaciers would raise sea levels by half a meter, much less than that the 80 meters or so that would result from total melt of the massive Greenland and Antarctic ice sheets. That is why glacier contributions to sea level rise have been less studied, allowing estimates of to vary widely. Glacier contributions to sea level change are challenging to quantify as they are broadly distributed, located in remote and poorly accessible high latitude and high altitude regions, and ground observations are sparse. Advances in satellite altimetry (ICESat) and gravimetry (GRACE) have helped, but they also have their own challenges and limitations. Here we present an updated (2003-2014) synthesis of multiple techniques adapted for varying regions to show that rates of glacier loss change little between the 2003-2009 and 2003-2014 periods, accounting for roughly one third of global mean sea level rise. Over the next century and beyond glaciers are expected to continue to contribute substantial volumes of water to the world's oceans, motivating continued study of how glaciers respond to climate change that will improve projections of future sea levels.

  8. Tidewater Margin Dynamics in Central East Greenland Over two Decades

    NASA Astrophysics Data System (ADS)

    Jiskoot, H.; Juhlin, D.; St. Pierre, H.; Citterio, M.

    2010-12-01

    About 50% (~50000 km2) of the glaciers peripheral to the Greenland Ice Sheet are located in central East Greenland (67°-72°N). This region of extreme topography contains ice caps, mountain glaciers and large outlet glacier systems. Regional runoff to the North Atlantic is important in global thermohaline circulation and sea ice dynamics. The region has very limited glaciological research and only few quantitative remote sensing studies. Because of factors including East Greenland being predicted as a hotspot in global climate models, the positive regional correlation between the timing of sea ice break-up and increased surface melt, and the regional glacier characteristics, it is assumed that central East Greenland is highly sensitive to climate change. Many glaciers are tidewater terminating and will have a direct dynamic response to increased ocean temperatures and rising sea level, which has in some cases already led to upstream speed-up. Additionally, some glaciers are inferred polythermal, hence projected climate change may affect their thermal regime and ice dynamic behaviour. Moreover, 30-70% of regional glaciers are of surge-type, and redistribution of glacier volume to lower elevations increases ablation. Terminus fluctuations associated with surges, as well as large multi-annual calving fluxes, complicate extraction of glacioclimatic responses. In order to assess glacier characteristics, recent changes, and climate sensitivity we compiled a detailed glacier inventory of the Geikie Plateau region, using semi-automated digitization from satellite imagery between 2000 and 2005. A mosaic was created using 68 ASTER and 6 Landsat7 scenes. Glaciers were identified using a supervised Mahalanobis Distance classification. Small polygons and irregularities were removed using the Lee Filter and manual correction. The glacier inventory contains 330 glaciers (41591 km2). The largest glacier, Kong Christian IV (10696 km2), is in part an outlet of the Greenland Ice

  9. New Gravity-Derived Grounding Line Depths Highlight Role Bathymetry Plays in Ongoing Greenland Ice Sheet Change

    NASA Astrophysics Data System (ADS)

    Boghosian, A.; Porter, D. F.; Tinto, K. J.; Bell, R. E.; Cochran, J. R.; Csatho, B. M.

    2014-12-01

    Bathymetry has been a missing piece in understanding ice-ocean interactions of marine-terminating glaciers in Greenland. As bathymetry in fjords often controls the flow of warm water to the terminus of the glacier, and the grounding line depth of the glacier can modulate the effect of this warm water on the glacier. Study of Tracy and Heilprin Glaciers, a pair of neighboring glaciers in northwest Greenland, has indicated that when exposed to similar external forcings, the glacier with the deeper grounding line will retreat more rapidly. The new comprehensive mapping of grounding line depths with Operation IceBridge gravity inversions provides the basis for examining this question for all of Greenland's glaciers. We consider 54 distinct glaciers in our analysis. Grounding line depths for these 54 come from data collected by Operation IceBridge from 2010-2012. New grounding line depths for 36 glaciers are derived from gravity measurements in locations where radar is unable to retrieve grounding line depths. 18 grounding line depths come from CReSIS Multichannel Coherent Depth Sounder radar data. Offshore bathymetry in all 54 fjords is gravity-derived. The gravity-derived bathymetry is always constrained onshore by radar, and when possible pinned offshore to acoustic bathymetric measurements.Here we present the gravity-derived grounding line depths along with recent glacier behavior, including surface lowering and terminus retreat, of these 54 glaciers. In general, the glaciers with deeper grounding lines are experiencing greater mass loss. This relationship between grounding line depth and mass balance extends to much of Greenland. We systematically discuss this relationship in the different major regions of Greenland, and note that the relationship is strongest in the southeast, and weakest in the north.

  10. Nuuk, Greenland

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Nuuk (or Gadthab) is the capital and largest city of Greenland. It is located at the mouth of the Nuup Kangerlua inlet on the west coast of Greenland. It has a population of about 15,000. The site has a long history of different inhabitation: first by the Inuit people around 2000 B.C., later by Viking explorers in the 10th century. Inuit and Vikings lived together for about 500 years until about 1500, when human habitation suddenly stopped, most likely due to change in climate and vegetation.

    The image was acquired August 2, 2004, covers an area of 22.7 x 26 km, and is located at 64.2 degrees north latitude, 51.8 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  11. Nuuk, Greenland

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Nuuk (or Gadthab) is the capital and largest city of Greenland. It is located at the mouth of the Nuup Kangerlua inlet on the west coast of Greenland. It has a population of about 15,000. The site has a long history of different inhabitation: first by the Inuit people around 2000 B.C., later by Viking explorers in the 10th century. Inuit and Vikings lived together for about 500 years until about 1500, when human habitation suddenly stopped, most likely due to change in climate and vegetation.

    The image was acquired August 2, 2004, covers an area of 22.7 x 26 km, and is located at 64.2 degrees north latitude, 51.8 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  12. Malaspina Glacier

    NASA Image and Video Library

    2017-09-27

    NASA image captured August 31, 2000 The tongue of the Malaspina Glacier, the largest glacier in Alaska, fills most of this image. The Malaspina lies west of Yakutat Bay and covers 1,500 sq. MI (3,880 sq. km). Credit: NASA/Landsat NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Join us on Facebook

  13. Glorious Glacier

    NASA Image and Video Library

    2016-07-15

    This image has low-sun lighting that accentuates the many transverse ridges on this slope, extending from Euripus Mons (mountains). These flow-like structures were previously called "lobate debris aprons," but the Shallow Radar (SHARAD) instrument on MRO has shown that they are actually debris-covered flows of ice, or glaciers. There is no evidence for present-day flow of these glaciers, so they appear to be remnants of past climates. http://photojournal.jpl.nasa.gov/catalog/PIA20745

  14. Matusevich Glacier

    NASA Image and Video Library

    2017-09-27

    NASA image acquired September 6, 2010 The Matusevich Glacier flows toward the coast of East Antarctica, pushing through a channel between the Lazarev Mountains and the northwestern tip of the Wilson Hills. Constrained by surrounding rocks, the river of ice holds together. But stresses resulting from the glacier’s movement make deep crevasses, or cracks, in the ice. After passing through the channel, the glacier has room to spread out as it floats on the ocean. The expanded area and the jostling of ocean waves prompts the ice to break apart, which it often does along existing crevasses. On September 6, 2010, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this natural-color image of the margin of Matusevich Glacier. Shown here just past the rock-lined channel, the glacier is calving large icebergs. Low-angled sunlight illuminates north-facing surfaces and casts long shadows to the south. Fast ice anchored to the shore surrounds both the glacier tongue and the icebergs it has calved. Compared to the glacier and icebergs, the fast ice is thinner with a smoother surface. Out to sea (image left), the sea ice is even thinner and moves with winds and currents. Matusevich Glacier does not drain a significant amount of ice off of the Antarctic continent, so the glacier’s advances and retreats lack global significance. Like other Antarctic glaciers, however, Matusevich helps glaciologists form a larger picture of Antarctica’s glacial health and ice sheet volume. NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Caption by Michon Scott based on image interpretation by Robert Bindschadler, NASA Goddard Space Flight Center, and Walt Meier, National Snow and Ice Data Center. Instrument: EO-1 - ALI Credit: NASA Earth Observatory NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar

  15. Associations between accelerated glacier mass wastage and increased summer temperature in coastal regions

    USGS Publications Warehouse

    Dyurgerov, M.; McCabe, G.J.

    2006-01-01

    Low-elevation glaciers in coastal regions of Alaska, the Canadian Arctic, individual ice caps around the Greenland ice sheet, and the Patagonia Ice Fields have an aggregate glacier area of about 332 ?? 103 km 2 and account for approximately 42% of all the glacier area outside the Greenland and Antarctic ice sheets. They have shown volume loss, especially since the end of the 1980s, increasing from about 45% in the 1960s to nearly 67% in 2003 of the total wastage from all glaciers on Earth outside those two largest ice sheets. Thus, a disproportionally large contribution of coastal glacier ablation to sea level rise is evident. We examine cumulative standardized departures (1961-2000 reference period) of glacier mass balances and air temperature data in these four coastal regions. Analyses indicate a strong association between increases in glacier volume losses and summer air temperature at regional and global scales. Increases in glacier volume losses in the coastal regions also coincide with an accelerated rate of ice discharge from outlet glaciers draining the Greenland and West Antarctic ice sheets. These processes imply further increases in sea level rise. ?? 2006 Regents of the University of Colorado.

  16. Glacier microseismicity

    USGS Publications Warehouse

    West, Michael E.; Larsen, Christopher F.; Truffer, Martin; O'Neel, Shad; LeBlanc, Laura

    2010-01-01

    We present a framework for interpreting small glacier seismic events based on data collected near the center of Bering Glacier, Alaska, in spring 2007. We find extremely high microseismicity rates (as many as tens of events per minute) occurring largely within a few kilometers of the receivers. A high-frequency class of seismicity is distinguished by dominant frequencies of 20–35 Hz and impulsive arrivals. A low-frequency class has dominant frequencies of 6–15 Hz, emergent onsets, and longer, more monotonic codas. A bimodal distribution of 160,000 seismic events over two months demonstrates that the classes represent two distinct populations. This is further supported by the presence of hybrid waveforms that contain elements of both event types. The high-low-hybrid paradigm is well established in volcano seismology and is demonstrated by a comparison to earthquakes from Augustine Volcano. We build on these parallels to suggest that fluid-induced resonance is likely responsible for the low-frequency glacier events and that the hybrid glacier events may be caused by the rush of water into newly opening pathways.

  17. North Greenland's Ice Shelves and Ocean Warming

    NASA Astrophysics Data System (ADS)

    Muenchow, A.; Schauer, U.; Padman, L.; Melling, H.; Fricker, H. A.

    2014-12-01

    Rapid disintegration of ice shelves (the floating extensions of marine-terminating glaciers) can lead to increasing ice discharge, thinning upstream ice sheets, rising sea level. Pine Island Glacier, Antarctica, and Jacobshavn Isbrae, Greenland, provide prominent examples of these processes which evolve at decadal time scales. We here focus on three glacier systems north of 78 N in Greenland, each of which discharges more than 10 Gt per year of ice and had an extensive ice shelf a decade ago; Petermann Gletscher (PG), Niogshalvfjerdsfjorden (79N), and Zachariae Isstrom (ZI). We summarize and discuss direct observations of ocean and glacier properties for these systems as they have evolved in the northwest (PG) and northeast (79N and ZI) of Greenland over the last two decades. We use a combination of modern and historical snapshots of ocean temperature and salinity (PG, 79N, ZI), moored observations in Nares Strait (PG), and snapshots of temperature and velocity fields on the broad continental shelf off northeast Greenland (79N, ZI) collected between 1993 and 2014. Ocean warming adjacent to PG has been small relative to the ocean warming adjacent to 79N and ZI; however, ZI lost its entire ice shelf during the last decade while 79N, less than 70 km to the north of ZI, remained stable. In contrast, PG has thinned by about 10 m/y just prior to shedding two ice islands representing almost half its ice shelf area or a fifth by volume. At PG advective ice flux divergence explains about half of the dominantly basal melting while response to non-steady external forcing explains the other half. The observations at PG,79N, and ZI suggest that remotely sensed ambient surface ocean temperatures are poor proxies to explain ice shelf thinning and retreat. We posit that local dynamics of the subsurface ocean heat flux matters most. Ocean heat must first be delivered over the sill into the fjord and then within the ice shelf cavity to the base of the shelf near the grounding line

  18. Alpine Glaciers

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 27 August 2003

    This image shows part of the western flank of Arsia Mons, the southernmost of the three great Tharsis Montes. The surface shows parallel ridges more reminiscent of a Zen garden than any typical geological feature. These ridges are not typical of lava flow fronts, so a different explanation has been proposed by Mars scientists. These ridges may instead be ancient signs of previously existing glaciers that formed high on the volcano's flank. As glaciers retreat with the seasons and shifting climate, they leave behind a mound of debris along their receding edge. Successive retreats can produce a series of parallel ridges similar to those seen here.

    Image information: VIS instrument. Latitude -6.9, Longitude 230.5 East (129.5 West). 19 meter/pixel resolution.

  19. Alpine Glaciers

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 27 August 2003

    This image shows part of the western flank of Arsia Mons, the southernmost of the three great Tharsis Montes. The surface shows parallel ridges more reminiscent of a Zen garden than any typical geological feature. These ridges are not typical of lava flow fronts, so a different explanation has been proposed by Mars scientists. These ridges may instead be ancient signs of previously existing glaciers that formed high on the volcano's flank. As glaciers retreat with the seasons and shifting climate, they leave behind a mound of debris along their receding edge. Successive retreats can produce a series of parallel ridges similar to those seen here.

    Image information: VIS instrument. Latitude -6.9, Longitude 230.5 East (129.5 West). 19 meter/pixel resolution.

  20. GLACIER SLIDING,

    DTIC Science & Technology

    The theory of the sliding of glaciers presented in earlier papers has been generalized (1) by taking into account the resistance to sliding offered...bed at the downstream side of an obstacle. The sliding velocities and controlling obstacle sizes which are found from the generalized theory are...magnitude smaller in thickness than the height of the controlling obstacles can cause an appreciable increase in the sliding velocity. The generalized

  1. Freshwater fluxes from Greenland into the ocean: A Case Study of Sermilik Fjord

    NASA Astrophysics Data System (ADS)

    Straneo, Fiamma; Beaird, Nicholas; Catania, Ginny; Felikson, Denis; Heimbach, Patrick; Moon, Twila; Sutherland, Dave; Masina, Simona; Colleoni, Florence

    2017-04-01

    Mass loss from the Greenland Ice Sheet quadrupled from 1992 to 2011, discharging an additional 2700 cubic kilometers of freshwater into the Arctic and North Atlantic Oceans. Future projections are for continued and enhanced mass loss, implying an even larger freshwater discharge into the ocean. Given the potential impact of this additional freshwater on the regional circulation, dense water formation and the marine ecosystems, it is important to include it in past model reconstructions and future model projections. At present, studies investigating the impact of Greenland freshwater on the ocean largely assume that it enters the ocean as a distributed, surface freshwater flux. Observation and model studies, however, show that much of Greenland's freshwater discharge into the ocean occurs subsurface via the melting of deep icebergs and glaciers and through the injection of seasonal surface melt from the base of glaciers hundreds of meters below the surface. Spatially, the discharge is concentrated around the major glacier/fjord systems. Here, we develop a framework to account for the different components of Greenland's freshwater discharge (ice sheet and glacier runoff, non-glaciated margin runoff, and ice discharge from marine terminating glaciers) for the period 1958-2015 and apply it to Sermilik Fjord, southeast Greenland, where present day discharge estimates can be compared to extensive observations. This effort is led by the GRISO Research Coordination Network.

  2. Investigating role of ice-ocean interaction on glacier dynamic: Results from numerical modeling applied to Petermann Glacier

    NASA Astrophysics Data System (ADS)

    Nick, F. M.; van der Veen, C. J.; Vieli, A.; Pattyn, F.; Hubbard, A.; Box, J. E.

    2010-12-01

    Calving of icebergs and bottom melting from ice shelves accounts for roughly half the ice transferred from the Greenland Ice Sheet into the surrounding ocean, and virtually all of the ice loss from the Antarctic Ice Sheet. Petermann Glacier (north Greenland) with its ~17 km wide and ~ 60 km long floating ice-shelf is experiencing high rates of bottom melting. The recent partial disintegration of its shelf (in August 2010) presents a natural experiment to investigate the dynamic response of the ice sheet to its shelf retreat. We apply a numerical ice flow model using a physically-based calving criterion based on crevasse depth to investigate the contribution of processes such as shelf disintegration, bottom melting, sea ice or sikkusak disintegration and surface run off to the mass balance of Petermann Glacier and assess its stability. Our modeling study provides insights into the role of ice-ocean interaction, and on response of Petermann Glacier to its recent massive ice loss.

  3. First Younger Dryas moraines in Greenland

    NASA Astrophysics Data System (ADS)

    Funder, Svend; Larsen, Nicolaj K.; Linge, Henriette; Möller, Per; Schomacker, Anders; Fabel, Derek; Kjær, Kurt H.; Xu, Sheng

    2016-04-01

    Over the Greenland ice sheet the Younger Dryas (YD) cold climate oscillation (12.9-11.7 kaBP) began with up to 10°C drop in temperatures and ended with up to 12°C abrupt warming. In the light of the present warming and melting of the ice sheet, and its importance for future climate change, the ice sheet's response to these dramatic changes in the past is of great interest. However, even though much effort has gone into charting YD ice margin behaviour around Greenland in recent years, no clear-cut signal of response to the oscillation has been uncovered. Here we show evidence to suggest that three major outlets from a local ice cap at Greenland's north coast advanced and retreated synchronously during YD. The evidence comprises OSL (optically stimulated luminescence) dates from a marine transgression of the coastal valleys that preceded the advance, and exposure ages from boulders on the moraines, formed by glaciers that overrode the marine sediment. The OSL ages suggest a maximum age of 12.4 ±0.6 kaBP for the marine incursion, and 10 exposure ages on boulders from the three moraines provide an average minimum age of 12.5 ±0.7 kaBP for the moraines, implying that the moraines were formed within the interval 11.8-13.0 kaBP. Elsewhere in Greenland evidence for readvance has been recorded in two areas. Most notably, in the East Greenland fjord zone outlet glaciers over a stretch of 800 km coast advanced through the fjords. In Scoresby Sund, where the moraines form a wide belt, an extensive 14C and exposure dating programme has shown that the readvance here probably culminated before YD, while cessation of moraine formation and rapid retreat from the moraine belt did not commence until c. 11.5 kaBP, but no moraines have so far been dated to YD. Readvance is also seen in Disko Bugt, the largest ice sheet outlet in West Greenland. However, here the advance and retreat of the ice stream took place in mid YD times, and lasted only a few hundred years, while YD in

  4. New constraints on the deglaciation chronology of the southeastern margin of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Levy, L.; Larsen, N. K.; Kjaer, K. H.; Bjork, A. A.; Kjeldsen, K. K.; Funder, S.; Kelly, M. A.; Howley, J. A.; Zimmerman, S. R. H.

    2015-12-01

    The Greenland Ice Sheet (GrIS) is responding rapidly to climate change. Marine terminating outlet glaciers that drain the GrIS have responded especially sensitively to present-day climate change by accelerating, thinning and retreating. In southeastern Greenland several outlet glaciers are undergoing rapid changes in mass balance and ice dynamics. To improve our understanding of the future, long-term response of these marine-terminating outlet glaciers to climate change, we focus on the response of three outlet glaciers to climate change since the Last Glacial Maximum. The timing and rates of late-glacial and early Holocene deglaciation of the southeastern sector of the GrIS are relatively unconstrained due to the inaccessibility of the region. Using a helicopter and a sailboat, we collected samples for 10Be surface exposure dating from three fjords in southeastern Greenland: Skjoldungen (63.4N), Uvtorsiutit (62.7N), and Lindenow (60.6N). These fjords drain marine terminating glaciers of the GrIS. Here we present 18 new 10Be ages from ~50 km long transects along these fjords that mark the timing of deglaciation from the outer coast inland to the present-day GrIS margin. Together with previously constrained deglaciation chronologies from Bernstorffs, Sermilik, and Kangerdlussuaq fjords in southeastern Greenland, these new chronologies offer insight into the late-glacial and early Holocene dynamics of the southeastern GrIS outlet glaciers. We compare the timing and rate of deglaciation in southeastern Greenland to climate records from the region to examine the mechanisms that drove deglaciation during late-glacial and early Holocene time. These new 10Be ages provide a longer-term perspective of marine terminating outlet glacier fluctuations in southeastern Greenland and can be used to model the ice sheet's response to late-glacial and early Holocene climate changes.

  5. Regional projections of glacier volume and runoff in response to twenty-first century climate scenarios (Invited)

    NASA Astrophysics Data System (ADS)

    Radic, V.; Bliss, A. K.; Hock, R.

    2013-12-01

    Changes in mass contained by mountain glaciers and ice caps can modify the Earth's hydrological cycle on multiple scales. On a global scale, the mass loss from glaciers contributes to sea level rise. On regional and local scales, glacier melt-water is an important contributor to and modulator of river flow. In this study we use an elevation-dependent glacier mass balance model to project annual volume changes and monthly runoff from all mountain glaciers and ice caps in the world (excluding those in the Antarctic periphery) for the 21st century forced by temperature and precipitation scenarios from 14 global climate models. The largest contributors to projected total volume loss are the glaciers in the Canadian and Russian Arctic, Alaska and glaciers peripheral to Greenland ice sheet. Although small contributors to global volume loss, glaciers in Central Europe, low-latitude South America, Caucasus, North Asia, and Western Canada and US are projected to lose more than 75% of their volume by 2100. The magnitude and sign of trends in annual runoff totals differ considerably among regions depending on the balance between enhanced melt and the reduction of the glacier reservoir by glacier retreat and shrinkage. Most regions show strong declines in glacier runoff indicating that the effect of glacier shrinkage is more dominant than increased melting rates. Some high-latitude regions (Arctic Canada North, Russian Arctic and Greenland) exhibit increases in runoff totals. Iceland and Svalbard show an increase in runoff followed by a multi-decadal decrease in annual runoff.

  6. From Glaciers to Icebergs

    NASA Astrophysics Data System (ADS)

    Zhang, Wendy

    I will describe works from a collaboration between physics and glaciology that grew out of interactions at the Computations in Science seminar Leo Kadanoff organized at the University of Chicago. The first project considers the interaction between ocean waves and Antarctic ice shelves, large floating portions of ice formed by glacial outflows. Back-of-envelop calculation and seismic sensor data suggest that crevasses may be distributed within an ice shelf to shield it from wave energy. We also examine numerical scenarios in which changes in environmental forcing causes the ice shelf to fail catastrophically. The second project investigates the aftermath of iceberg calving off glacier terminus in Greenland using data recorded via time-lapse camera and terrestrial radar. Our observations indicate that the mélange of icebergs within the fjord experiences widespread jamming during a calving event and therefore is always close to being in a jammed state during periods of terminus quiescence. Joint work with Jason Amundson, Ivo R. Peters, Julian Freed Brown, Nicholas Guttenberg, Justin C Burton, L. Mac Cathles, Ryan Cassotto, Mark Fahnestock, Kristopher Darnell, Martin Truffer, Dorian S. Abbot and Douglas MacAyeal. Kadanoff Session DCMP.

  7. Greenland Expeditions by Alfred Wegener - A photographic window to past

    NASA Astrophysics Data System (ADS)

    Leitner, M.; Tschürtz, S.; Kirchengast, G.; Kranzelbinder, H.; Prügger, B.; Krause, R. A.; Kalliokoski, M.; Thórhallsdóttir, E.

    2012-04-01

    On several expeditions to Greenland, Alfred Wegener (1880-1930) took pictures on glass plates from landscapes and glaciers, the expedition equipment, the people and animals taking part on the expeditions as well as physical phenomena as dust storm, clouds or spherical light phenomena. Chronologically the plates show the Danmark Expedition 1906-1908, the crossing of Greenland expedition with stop in Iceland 1912-1913, and the German Greenland Expedition 1929-1930. Until the tragic end of the expedition in 1930, Wegener was professor at the University of Graz, and such a stock of about 300 glass plates stayed there. The aim of our work is to digitize all plates for further studies. We present a first selection of Wegener's Greenland expedition pictures. For those made at Iceland in 1912 we will present a comparison of the past with pictures from the same viewing point made in 2011.

  8. Qassiarsuk, Greenland

    NASA Image and Video Library

    2016-09-16

    The first Norse settlement of Greenland was at Brattahlid (now Qassiarsuk), which yielded a radiocarbon date of about 1000. According to the sagas, it was also in the year 1000 that Leif Erikson left the settlement to explore the regions around Vinland, which is generally assumed to be Newfoundland. Norse settlements at their height had an estimated population of a few thousand. After 450 years, the settlements were all abandoned. Causes include: cumulative environmental damage; gradual climate change; conflicts with hostile neighbors; and loss of contact and support from Europe. The image was acquired June 13, 2016, covers an area of 30.9 by 27.7 km, and is located at 61.1 degrees north, 45.5 degrees west. http://photojournal.jpl.nasa.gov/catalog/PIA20996

  9. ICESat Observations of Southern Alaska Glaciers

    NASA Technical Reports Server (NTRS)

    Sauber, Jeanne; Molnia, Bruce F.; Mitchell, Darius

    2003-01-01

    In late February and March, 2003, the Ice, Cloud, and land Elevation Satellite (ICESat) measured ice and land elevations along profiles across southern Alaska. During this initial data acquisition stage ICESat observations were made on 8-day repeat tracks to enable calibration and validation of the ICESat data products. Each profile consists of a series of single point values derived from centroid elevations of an $\\approx$70 m diameter laser footprint. The points are s4pakated by $\\approx$172 m along track. Data siets of 8-day observations (an ascending and descending ground track) crossed the Bering and Malaspina Glacier. Following its 1993--1995 surge; the Bering Glacier has undergone major terminus retreat as well as ike thinning in the abtation zone. During the later part of the 20th century, parts of the Malaspina thinned by about 1 m/yr. The multiple observation profiles across the Bering and Malaspina piedmont lobes obtained in February/March are being geolocated on Landsat images and the elevation profiles will be used for a number o scientific objectives. Based on our simulations of ICESat performance over the varied ice surface of the Jakobshavn Glacier of GReenland, 2003, we expect to measure annual, and possibly seasonal, ice elevation changes on the large Alaskan glaciers. Using elevation data obtained from a second laser, we plan to estimate ice elevation changes on the Bering Glacier between March and October 2003.

  10. Towards a complete World Glacier Inventory

    NASA Astrophysics Data System (ADS)

    Zemp, Michael

    2013-04-01

    scale. A first globally and almost complete map with (generalized) digital outlines of all ice covered regions (incl. Greenland but excluding Antarctica) was derived from ESRI's Digital Chart of the World (DCW) and other sources by Raup and colleagues in 2000. Most recently, Arendt and colleagues produced the Randolph dataset which combines available outlines from the GLIMS, DCW, and WGI datasets as well as from many other (often unpublished) sources by using the highest quality version in each region. However, while having the advantage of being almost complete, these global estimates lack time stamps and attributes for individual glaciers. The present work provides a brief review of the various efforts, its methodological differences, and findings towards the completion of a World Glacier Inventory.

  11. The Greenland Ice Sheet Monitoring Network (GLISN)

    NASA Astrophysics Data System (ADS)

    Anderson, K. R.; Beaudoin, B. C.; Butler, R.; Clinton, J. F.; Dahl-Jensen, T.; Ekstrom, G.; Giardini, D.; Govoni, A.; Hanka, W.; Kanao, M.; Larsen, T.; Lasocki, S.; McCormack, D. A.; Mykkeltveit, S.; Nettles, M.; Agostinetti, N. P.; Stutzmann, E.; Tsuboi, S.; Voss, P.

    2010-12-01

    The GreenLand Ice Sheet monitoring Network (GLISN) is an international, broadband seismic capability for Greenland, being installed and implemented through the collaboration of Denmark, Canada, Germany, Italy, Japan, Norway, Poland, Switzerland, and USA. GLISN is a real-time sensor array of seismic stations to enhance and upgrade the performance of the sparse Greenland seismic infrastructure for detecting, locating, and characterizing glacial earthquakes and other cryo-seismic phenomena, and contributing to our understanding of Ice Sheet dynamics. Complementing data from satellites, geodesy, and other sources, and in concert with these technologies, GLISN will provide a powerful tool for detecting change, and will advance new frontiers of research in the glacial systems; the underlying geological and geophysical processes affecting the Greenland Ice Sheet; interactions between oceans, climate, and the cryosphere; and other multidisciplinary areas of interest to geoscience and climate dynamics. The glacial processes that induce seismic events (internal deformation, sliding at the base, disintegration at the calving front, drainage of supra-glacial lakes) are all integral to the overall dynamics of glaciers, and seismic observations of glaciers therefore provide a quantitative means for monitoring changes in their behavior over time. Long-term seismic monitoring of the Greenland Ice Sheet will contribute to identifying possible unsuspected mechanisms and metrics relevant to ice sheet collapse, and will provide new constraints on Ice Sheet dynamic processes and their potential roles in sea-level rise during the coming decades. GLISN will provide a new, fiducial reference network in and around Greenland for monitoring these phenomena in real-time, and for the broad seismological study of Earth and earthquakes. The 2010 summer field season saw the installation or upgrade of 9 stations in the GLISN network. Sites visited under the GLISN project include Station Nord (NOR

  12. Principles of Glacier Mechanics

    NASA Astrophysics Data System (ADS)

    Waddington, Edwin D.

    Glaciers are awesome in size and move at a majestic pace, and they frequently occupy spectacular mountainous terrain. Naturally, many Earth scientists are attracted to glaciers. Some of us are even fortunate enough to make a career of studying glacier flow. Many others work on the large, flat polar ice sheets where there is no scenery. As a leader of one of the foremost research projects now studying the flow of mountain glaciers (Storglaciaren, Norway), Roger Hooke is well qualified to describe the principles of glacier mechanics. Principles of Glacier Mechanics is written for upper-level undergraduate students and graduate students with an interest in glaciers and the landforms that glaciers produce. While most of the examples in the text are drawn from valley glacier studies, much of the material is also relevant to “glacier flatland” on the polar ice sheets.

  13. Iceberg calving dynamics of Jakobshavn Isbrae, Greenland

    NASA Astrophysics Data System (ADS)

    Amundson, Jason Michael

    Jakobshavn Isbrae, a fast-flowing outlet glacier in West Greenland, began a rapid retreat in the late 1990's. The glacier has since retreated over 15 km, thinned by tens of meters, and doubled its discharge into the ocean. The glacier's retreat and associated dynamic adjustment are driven by poorly-understood processes occurring at the glacier-ocean interface. These processes were investigated by synthesizing a suite of field data collected in 2007--2008, including timelapse imagery, seismic and audio recordings, iceberg and glacier motion surveys, and ocean wave measurements, with simple theoretical considerations. Observations indicate that the glacier's mass loss from calving occurs primarily in summer and is dominated by the semi-weekly calving of full-glacier-thickness icebergs, which can only occur when the terminus is at or near flotation. The calving icebergs produce long-lasting and far-reaching ocean waves and seismic signals, including "glacial earthquakes". Due to changes in the glacier stress field associated with calving, the lower glacier instantaneously accelerates by ˜3% but does not episodically slip, thus contradicting the originally proposed glacial earthquake mechanism. We furthermore showed that the predominance of calving during summer can be attributed to variations in the strength of the proglacial ice melange (dense pack of sea ice and icebergs). Sea ice growth in winter stiffens the melange and prevents calving; each summer the melange weakens and calving resumes. Previously proposed calving models are unable to explain the terminus dynamics of Jakobshavn Isbrae (and many other calving glaciers). Using our field observations as a basis, we developed a general framework for iceberg calving models that can be applied to any calving margin. The framework is based on mass continuity, the assumption that calving rate and terminus velocity are not independent, and the simple idea that terminus thickness following a calving event is larger than

  14. South Cascade Glacier bibliography

    SciTech Connect

    Fountain, A.G.; Fulk, M.A.

    1984-01-01

    South Cascade Glacier, in Washington State, resides in a well-defined basin with mainly unglacierized divides making it ideal for most glaciological and hydrological studies. This bibliography is divided into three cateogories: (1) studies done about South Cascade Glacier specifically; (2) studies that use data from South Cascade Glacier but do not focus on or give insight to the glacier itself; and (3) instrumentation studies and non-glacier projects including snow studies done in the basin. (ACR)

  15. Geoengineering Outlet Glaciers and Ice Streams

    NASA Astrophysics Data System (ADS)

    Wolovick, Michael

    2017-04-01

    Mass loss from Greenland and Antarctica is highly sensitive to the presence of warm ocean water that drives melting of ice shelves and marine terminated glaciers. This warm water resides offshore at depth and accesses the grounding line through deep but narrow troughs and fjords. Here, we investigate the possibility of blocking warm water transport through these choke points with an artificial sill. Using a simple width-averaged model of ice stream flow coupled to a buoyant-plume model of submarine melt, we find that grounding line retreat and sea level rise can be delayed or reversed for hundreds of years if warm water is prevented from accessing outlet glaciers and ice-shelf cavities. Glaciers with a floating shelf exhibit a strong response to the presence of the artificial sill regardless of our choice of calving law, while tidewater glaciers require a strong linkage between submarine melt and iceberg calving for the artificial sill to have an effect. As a result of this difference and as a result of differing degrees of overdeepening in the basal topography, Antarctica and Greenland present very different societal cost-benefit analyses. Intervention in Greenland would be low-cost and low-reward: the volume of the artificial sill is comparable to existing large public works projects such as the Dubai Islands or the Suez Canal, but the magnitude of averted sea-level rise is small, the success of the intervention depends on the choice of calving law, and the glaciers return to their non-geoengineered trajectories within one to two centuries. Intervention in Antarctica, on the other hand, would be high-cost and high-reward: the volume of the artificial sill is one to two orders of magnitude greater, but the averted sea level rise is much larger, the intervention is successful regardless of the choice of calving law, and the ice streams remain far from their non-geoengineered trajectories throughout the 1000 year duration of our model runs. In both cases, an

  16. Resolving bathymetry from airborne gravity along Greenland fjords

    USGS Publications Warehouse

    Boghosian, Alexandra; Tinto, Kirsty; Cochran, James R.; Porter, David; Elieff, Stefan; Burton, Bethany; Bell, Robin E.

    2015-01-01

    Recent glacier mass loss in Greenland has been attributed to encroaching warming waters, but knowledge of fjord bathymetry is required to investigate this mechanism. The bathymetry in many Greenland fjords is unmapped and difficult to measure. From 2010 to 2012, National Aeronautics and Space Administration's Operation IceBridge collected a unique set of airborne gravity, magnetic, radar, and lidar data along the major outlet glaciers and fjords in Greenland. We applied a consistent technique using the IceBridge gravity data to create 90 bathymetric profiles along 54 Greenland fjords. We also used this technique to recover subice topography where warm or crevassed ice prevents the radar system from imaging the bed. Here we discuss our methodology, basic assumptions and error analysis. We present the new bathymetry data and discuss observations in six major regions of Greenland covered by IceBridge. The gravity models provide a total of 1950 line kilometers of bathymetry, 875 line kilometers of subice topography, and 12 new grounding line depths.

  17. Resolving bathymetry from airborne gravity along Greenland fjords

    NASA Astrophysics Data System (ADS)

    Boghosian, Alexandra; Tinto, Kirsty; Cochran, James R.; Porter, David; Elieff, Stefan; Burton, Bethany L.; Bell, Robin E.

    2015-12-01

    Recent glacier mass loss in Greenland has been attributed to encroaching warming waters, but knowledge of fjord bathymetry is required to investigate this mechanism. The bathymetry in many Greenland fjords is unmapped and difficult to measure. From 2010 to 2012, National Aeronautics and Space Administration's Operation IceBridge collected a unique set of airborne gravity, magnetic, radar, and lidar data along the major outlet glaciers and fjords in Greenland. We applied a consistent technique using the IceBridge gravity data to create 90 bathymetric profiles along 54 Greenland fjords. We also used this technique to recover subice topography where warm or crevassed ice prevents the radar system from imaging the bed. Here we discuss our methodology, basic assumptions and error analysis. We present the new bathymetry data and discuss observations in six major regions of Greenland covered by IceBridge. The gravity models provide a total of 1950 line kilometers of bathymetry, 875 line kilometers of subice topography, and 12 new grounding line depths.

  18. Ellesmere Island (Canada) and Northern Greenland

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In late July, our planet.s northernmost land masses appear to finally be responding to the warmth of Northern Hemisphere summer. Ellesmere Island, Canada, (top left) and northern Greenland (right) have decided kick off their snowy winter garments in this true-color Moderate Resolution Imaging Spectroradiometer (MODIS) image from July 3, 200. Bare brown soils are exposed along the coasts of the still frozen (but thawing!) Arctic waters. Several large, permanent ice caps and glaciers will remain on Ellesmere Island year-round, and Greenland does little more than remove her mittens, but thinning, blue ice is showing up in the many fjords and inlets in the rocky coastlines, showing that temperatures are on the rise. The Nares Strait, which separates the two land masses, still has a way to go before a passage opens up between Baffin Bay to the south and the Artic Ocean to the north. Although Ellesmere Island appears to be 'higher' or farther north than Greenland, that is simply a result of the way the high-latitude scene was projected into an image. To better picture the terrain, imagine that you took a printed copy of the rectangular image and rolled it into a cylinder along its northeast-southwest axis. If you held that cylinder straight up in front of you, you would find that Peary Land, Greenland (right of center), is actually the more northern terrain. In fact Peary Land is the northernmost point on land on the Earth.

  19. Ellesmere Island (Canada) and Northern Greenland

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In late July, our planet.s northernmost land masses appear to finally be responding to the warmth of Northern Hemisphere summer. Ellesmere Island, Canada, (top left) and northern Greenland (right) have decided kick off their snowy winter garments in this true-color Moderate Resolution Imaging Spectroradiometer (MODIS) image from July 3, 200. Bare brown soils are exposed along the coasts of the still frozen (but thawing!) Arctic waters. Several large, permanent ice caps and glaciers will remain on Ellesmere Island year-round, and Greenland does little more than remove her mittens, but thinning, blue ice is showing up in the many fjords and inlets in the rocky coastlines, showing that temperatures are on the rise. The Nares Strait, which separates the two land masses, still has a way to go before a passage opens up between Baffin Bay to the south and the Artic Ocean to the north. Although Ellesmere Island appears to be 'higher' or farther north than Greenland, that is simply a result of the way the high-latitude scene was projected into an image. To better picture the terrain, imagine that you took a printed copy of the rectangular image and rolled it into a cylinder along its northeast-southwest axis. If you held that cylinder straight up in front of you, you would find that Peary Land, Greenland (right of center), is actually the more northern terrain. In fact Peary Land is the northernmost point on land on the Earth.

  20. Simulations of the Greenland ice sheet 100 years into the future with the full Stokes model Elmer/Ice

    NASA Astrophysics Data System (ADS)

    Seddik, H.; Greve, R.; Zwinger, T.; Gillet-Chaulet, F.; Gagliardini, O.

    2011-12-01

    The full Stokes thermo-mechanically coupled model Elmer/Ice is applied to the Greenland ice sheet. Elmer/Ice employs the finite element method to solve the full Stokes equations, the temperature evolution equation and the evolution equation of the free surface. The general framework of this modeling effort is a contribution to the Sea-level Response to Ice Sheet Evolution (SeaRISE) assessment project, a community-organized effort to estimate the likely range of ice sheet contributions to sea level rise over the next few hundred years (http://tinyurl.com/srise-lanl, http://tinyurl.com/srise-umt). The present geometry (surface and basal topographies) is derived from data where the basal topography was created with the preservation of the troughs at the Jakobshavn Ice Stream, Helheim, Kangerdlussuaq and Petermann glaciers. A mesh of the computational domain is created using an initial footprint which contains elements of 5 km horizontal resolution and to limit the number elements on the footprint while maximizing the spatial resolution, an anisotropic mesh adaptation scheme is employed based on the Hessian matrix of the observed surface velocities. The adaptation is carried out with the tool YAMS and the final footprint is vertically extruded to form a 3D mesh of 320880 elements with 17 equidistant, terrain-following layers. The numerical solution of the Stokes and the heat transfer equations employs direct solvers with stabilization procedures. The boundary conditions are such that the temperature at the surface uses the present-day mean annual air temperature given by a parameterization or directly from the available data, the geothermal heat flux at the bedrock is given by data and the lateral sides are open boundaries. A non-linear Weertman law is used for the basal sliding. Results for the SeaRISE 2011 sensitivity experiments are presented so that six different experiments have been conducted, grouped in two sets. The Set C (three experiments) applies a change to

  1. Chutes and Fissures in Greenland

    NASA Image and Video Library

    2015-05-12

    Scientists and crew with NASA’s Operation IceBridge, which makes annual aerial surveys of polar ice, are wrapping up their seventh campaign over the Arctic. In spring 2015, the team began using a different research aircraft—an adapted C-130 Hercules. They also added four new high-priority targets in the rapidly changing region of northeast Greenland. Many of the flights, however, were routine. And that’s exactly the point; making measurements over the same path each year provides continuity between NASA’s Ice, Cloud, and Land Elevation Satellite (ICESat) missions—the first of which ended in 2009 and the second of which is scheduled for launch in 2017. Repeat measurements show how a landscape changes over time. One area that has been surveyed repeatedly is northern Greenland’s Ryder Glacier. This photograph, taken during the IceBridge flight on May 6, 2015, shows a large moulin—dozens of meters across—atop this glacier. Moulins are holes in the ice sheet that drain melt water from the ice sheet’s surface to the bottom or out to the sea. Scientists are working to figure out what happens to melt water once it enters a moulin.

  2. Contribution of small glaciers to global sea level

    USGS Publications Warehouse

    Meier, M.F.

    1984-01-01

    Observed long-term changes in glacier volume and hydrometeorological mass balance models yield data on the transfer of water from glaciers, excluding those in Greenland and Antarctica, to the oceans, The average observed volume change for the period 1900 to 1961 is scaled to a global average by use of the seasonal amplitude of the mass balance. These data are used to calibrate the models to estimate the changing contribution of glaciers to sea level for the period 1884 to 1975. Although the error band is large, these glaciers appear to accountfor a third to half of observed rise in sea level, approximately that fraction not explained by thermal expansion of the ocean.

  3. Climatic Controls on the Distribution of Surging Glaciers

    NASA Astrophysics Data System (ADS)

    Sevestre, H.; Benn, D.

    2012-12-01

    Surge-type glaciers are scattered in a non-random fashion, gathered in clusters in some glaciated regions. One group of clusters forms an Arctic and Sub-Arctic 'crescent', spanning from Alaska-Yukon, through Arctic Canada, West and East Greenland, Iceland, Svalbard and Novaya Zemlya. Another cluster occurs in western High Asia, including the Karakoram Mountains. Although several studies have assessed the influence of environmental controls on surging, so far none has provided a satisfactory explanation for the geographical location of these clusters. The distribution of such glaciers undoubtedly holds the keys of a better understanding on the controls on surging behaviour. For this study, two glacier populations are considered. First, a global inventory of glacier surges has been compiled, based on published observations, field reports and remote sensing studies. This digital database is structured in three tables, respectively providing information on the location and geometry of each surge-type glacier, surge dates and magnitude, and methodology employed at the time of observation. This global dataset is compared to the population of "non-surge-type glaciers" based on the Randolph Glacier Inventory version 2.0 excluding the inventoried surging glaciers. In both populations, glaciers are classified depending on their geometry and thermal regime. Downscaled climatic datasets are used to identify climatic envelopes associated with clusters of surging glaciers. We identified which environments are most prone to be associated to glacier surging, and examined the influence of these parameters on the surge cycle duration and character. These results emphasize the importance of external controls on surging (as against individual surges), and promote the need to study this behaviour in the frame of an energy-balance budget.

  4. Glaciers of North America - Glaciers of Alaska

    USGS Publications Warehouse

    Molnia, Bruce F.

    2008-01-01

    Glaciers cover about 75,000 km2 of Alaska, about 5 percent of the State. The glaciers are situated on 11 mountain ranges, 1 large island, an island chain, and 1 archipelago and range in elevation from more than 6,000 m to below sea level. Alaska's glaciers extend geographically from the far southeast at lat 55 deg 19'N., long 130 deg 05'W., about 100 kilometers east of Ketchikan, to the far southwest at Kiska Island at lat 52 deg 05'N., long 177 deg 35'E., in the Aleutian Islands, and as far north as lat 69 deg 20'N., long 143 deg 45'W., in the Brooks Range. During the 'Little Ice Age', Alaska's glaciers expanded significantly. The total area and volume of glaciers in Alaska continue to decrease, as they have been doing since the 18th century. Of the 153 1:250,000-scale topographic maps that cover the State of Alaska, 63 sheets show glaciers. Although the number of extant glaciers has never been systematically counted and is thus unknown, the total probably is greater than 100,000. Only about 600 glaciers (about 1 percent) have been officially named by the U.S. Board on Geographic Names (BGN). There are about 60 active and former tidewater glaciers in Alaska. Within the glacierized mountain ranges of southeastern Alaska and western Canada, 205 glaciers (75 percent in Alaska) have a history of surging. In the same region, at least 53 present and 7 former large ice-dammed lakes have produced jokulhlaups (glacier-outburst floods). Ice-capped volcanoes on mainland Alaska and in the Aleutian Islands have a potential for jokulhlaups caused by subglacier volcanic and geothermal activity. Because of the size of the area covered by glaciers and the lack of large-scale maps of the glacierized areas, satellite imagery and other satellite remote-sensing data are the only practical means of monitoring regional changes in the area and volume of Alaska's glaciers in response to short- and long-term changes in the maritime and continental climates of the State. A review of the

  5. Glaciers of South America

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1998-01-01

    Landsat images, together with maps and aerial photographs, have been used to produce glacier inventories, define glacier locations, and study glacier dynamics in the countries of South America, along with the Andes Mountains. In Venezuela, Colombia, Ecuador, and Bolivia, the small glaciers have been undergoing extensive glacier recession since the late 1800's. Glacier-related hazards (outburst floods, mud flows, and debris avalanches) occur in Colombia, in Ecuador, and associated with the more extensive (2,600 km2) glaciers of Peru. The largest area of glacier ice is found in Argentina and Chile, including the northern Patagonian ice field (about 4,200 km2) and the southern Patagonian ice field (about 13,000 km2), the largest glacier in the Southern Hemisphere outside Antarctica.

  6. Glaciers of Europe

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1993-01-01

    ALPS: AUSTRIAN: An overview is provided on the occurrence of the glaciers in the Eastern Alps of Austria and on the climatic conditions in this area, Historical documents on the glaciers have been available since the Middle Ages. Special glaciological observations and topographic surveys of individual glaciers were initiated as early as 1846. Recent data in an inventory based on aerial photographs taken in 1969 show 925 glaciers in the Austrian Alps with a total area of 542 square kilometers. Present research topics include studies of mass and energy balance, relations of glaciers and climate, physical glaciology, a complete inventory of the glaciers, and testing of remote sensing methods. The location of the glacier areas is shown on Landsat multispectral scanner images; the improved capabilities of the Landsat thematic mapper are illustrated with an example from the Oztaler Alpen group. ALPS: SWISS: According to a glacier inventory published in 1976, which is based on aerial photography of 1973, there are 1,828 glacier units in the Swiss Alps that cover a total area of 1fl42 square kilometers. The Rhonegletscher, currently the ninth largest in the country, was one of the first to be studied in detail. Its surface has been surveyed repeatedly; velocity profiles were measured, and the fluctuations of its terminus were mapped and recorded from 1874 to 1914. Recent research on the glacier has included climatological, hydrological, and massbalance studies. Glaciological research has been conducted on various other glaciers in Switzerland concerning glacier hydrology, glacier hazards, fluctuations of glacier termini, ice mechanics, ice cores, and mass balance. Good maps are available showing the extent of glaciers from the latter decades of the 19th century. More recently, the entire country has been mapped at scales of 1:25,000, 1:50,000, 1:100,000, 1:200,000, and 1:500,000. The 1:25,000-scale series very accurately represents the glaciers as well as locates

  7. Updating the results of glacier contribution to the sea level change

    NASA Technical Reports Server (NTRS)

    Dyurgerov, Mark B.; Abdalati, Waleed Dr. (Technical Monitor)

    2005-01-01

    I have completed an update of global glacier volume change. All data of glacier annual mass balances, surface area over the period 1945/46 till 2004, outside the Greenland and Antarctic ice sheets were included in this update. As the result global glacier volume change have been calculated, also in terms of glacier contribution to sea level change. These results were sent to Working Group 1 and 2 of IPCC-4 as the basis for modeling of sea level towards the end of 2100. In this study I have concentrated on studying glacier systems of different scales, from primary (e.g. Devon ice cap) to regional (e.g. Canadian Arctic), continental scale (e,g., entire Arctic), and global (e.g., change in glacier volume and contribution to sea level rise).

  8. Updating the results of glacier contribution to the sea level change

    NASA Technical Reports Server (NTRS)

    Dyurgerov, Mark B.; Abdalati, Waleed Dr. (Technical Monitor)

    2005-01-01

    I have completed an update of global glacier volume change. All data of glacier annual mass balances, surface area over the period 1945/46 till 2004, outside the Greenland and Antarctic ice sheets were included in this update. As the result global glacier volume change have been calculated, also in terms of glacier contribution to sea level change. These results were sent to Working Group 1 and 2 of IPCC-4 as the basis for modeling of sea level towards the end of 2100. In this study I have concentrated on studying glacier systems of different scales, from primary (e.g. Devon ice cap) to regional (e.g. Canadian Arctic), continental scale (e,g., entire Arctic), and global (e.g., change in glacier volume and contribution to sea level rise).

  9. Tidal Flexure, Ice Velocities, and Ablation Rates of Peterman Gletscher, Greenland

    NASA Technical Reports Server (NTRS)

    Rignot, Eric

    1996-01-01

    Over the floating section of a tide-water glacier, single radar intererograms are difficult to use because the long-term steady motion of the ice is intermixed with the tidal vertical motion of the glacier. With multiple interferograms, it is however possible to isolate the tidal signal and remove it from the single interferograms to estimate the ice velocities. The technique is applied to ERS-1 synthetic aperture radar (SAR) images of Petermann Gletscher, north Greenland.

  10. Airborne Geophysics and Remote Sensing Applied to Study Greenland Ice Dynamics

    NASA Technical Reports Server (NTRS)

    Csatho, Beata M.

    2003-01-01

    Overview of project: we combined and jointly analysed geophysical, remote sensing and glaciological data for investigating the temporal changes in ice flow and the role of geologic control on glacial drainage. The project included two different studies, the investigation of recent changes of the Kangerlussuaq glacier and the study of geologic control of ice flow in NW Greenland, around the Humboldt, Petermann and Ryder glaciers.

  11. Tidal Flexure, Ice Velocities, and Ablation Rates of Peterman Gletscher, Greenland

    NASA Technical Reports Server (NTRS)

    Rignot, Eric

    1996-01-01

    Over the floating section of a tide-water glacier, single radar intererograms are difficult to use because the long-term steady motion of the ice is intermixed with the tidal vertical motion of the glacier. With multiple interferograms, it is however possible to isolate the tidal signal and remove it from the single interferograms to estimate the ice velocities. The technique is applied to ERS-1 synthetic aperture radar (SAR) images of Petermann Gletscher, north Greenland.

  12. Airborne Geophysics and Remote Sensing Applied to Study Greenland Ice Dynamics

    NASA Technical Reports Server (NTRS)

    Csatho, Beata M.

    2003-01-01

    Overview of project: we combined and jointly analysed geophysical, remote sensing and glaciological data for investigating the temporal changes in ice flow and the role of geologic control on glacial drainage. The project included two different studies, the investigation of recent changes of the Kangerlussuaq glacier and the study of geologic control of ice flow in NW Greenland, around the Humboldt, Petermann and Ryder glaciers.

  13. Jakobshavns Glacier drainage basin - A balance assessment

    NASA Technical Reports Server (NTRS)

    Bindschadler, R. A.

    1984-01-01

    Maximum and minimum estimates are made of the drainage basin feeding the Jakobshavns Glacier by using surface elevation maps derived from Seasat altimetry. Benson's (1962) net balance measurements are used to calculate the balance flow within the basin. Comparisons of the balance flux at the terminus with estimates of actual flux suggest the basin is in overall equilibrium or slightly thickening. This agrees with measurements along the nearby EGIG traverse. Balance velocities accelerate rapidly within 100 km of the coast. Farther upstream, balance velocities are consistent with both measured velocities along the EGIG traverse and calculated deformation velocities. It is estimated that Jakobshavns Glacier discharges between 4.8 and 7.6 percent of the annual net balance over Greenland and drains between 3.7 and 5.8 percent of the ice sheet area.

  14. Jakobshavns Glacier drainage basin - A balance assessment

    NASA Technical Reports Server (NTRS)

    Bindschadler, R. A.

    1984-01-01

    Maximum and minimum estimates are made of the drainage basin feeding the Jakobshavns Glacier by using surface elevation maps derived from Seasat altimetry. Benson's (1962) net balance measurements are used to calculate the balance flow within the basin. Comparisons of the balance flux at the terminus with estimates of actual flux suggest the basin is in overall equilibrium or slightly thickening. This agrees with measurements along the nearby EGIG traverse. Balance velocities accelerate rapidly within 100 km of the coast. Farther upstream, balance velocities are consistent with both measured velocities along the EGIG traverse and calculated deformation velocities. It is estimated that Jakobshavns Glacier discharges between 4.8 and 7.6 percent of the annual net balance over Greenland and drains between 3.7 and 5.8 percent of the ice sheet area.

  15. Storage and release of organic carbon from glaciers and ice sheets

    USGS Publications Warehouse

    Hood, Eran; Battin, Tom J.; Fellman, Jason; O'Neel, Shad; Spencer, Robert G. M.

    2015-01-01

    Polar ice sheets and mountain glaciers, which cover roughly 11% of the Earth's land surface, store organic carbon from local and distant sources and then release it to downstream environments. Climate-driven changes to glacier runoff are expected to be larger than climate impacts on other components of the hydrological cycle, and may represent an important flux of organic carbon. A compilation of published data on dissolved organic carbon from glaciers across five continents reveals that mountain and polar glaciers represent a quantitatively important store of organic carbon. The Antarctic Ice Sheet is the repository of most of the roughly 6 petagrams (Pg) of organic carbon stored in glacier ice, but the annual release of glacier organic carbon is dominated by mountain glaciers in the case of dissolved organic carbon and the Greenland Ice Sheet in the case of particulate organic carbon. Climate change contributes to these fluxes: approximately 13% of the annual flux of glacier dissolved organic carbon is a result of glacier mass loss. These losses are expected to accelerate, leading to a cumulative loss of roughly 15 teragrams (Tg) of glacial dissolved organic carbon by 2050 due to climate change — equivalent to about half of the annual flux of dissolved organic carbon from the Amazon River. Thus, glaciers constitute a key link between terrestrial and aquatic carbon fluxes, and will be of increasing importance in land-to-ocean fluxes of organic carbon in glacierized regions.

  16. Influence of Runoff and Subglacial Discharge on Heat Transport in a Subpolar Fjord (Godthåbsfjord, 64°N) in Contact with the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Bendtsen, J.; Mortensen, J.; Rysgård, S.

    2016-02-01

    Deep fjords around Greenland connects coastal water masses with the Greenland Ice Sheet. Runoff from surrounding drainage areas, including glacier ice, contribute to relatively low-saline surface water in the fjords but also calving and subglacial discharge from tidewater outlet glaciers affect water properties and fjord circulation. Relatively warm bottom water masses have been observed in front of tidewater outlet glaciers where they provide energy for subsurface melt. Thus, feedbacks between ocean heat transport and melting of tidewater outlet glaciers are critical for determining glacier melt rates and their stability in a warmer climate. Here we analyze a regional model of a Subpolar fjord (Godthåbsfjord, 64°N), located at the west coast of Greenland and in direct contact with the Greenland Ice Sheet via three tidal outlet glaciers. We apply observations from the fjord and surrounding coastal areas to analyze model simulations of temperature, salinity and δ18O. The model includes the largest freshwater sources from runoff in the area and subglacial freshwater discharge from three tidewater outlet glaciers, where entrainment of bottom water is taken into account, are included explicitly in the boundary conditions. A model sensitivity study analyze the influence of subglacial discharge and runoff on heat transports towards the glaciers and model results are compared with observations.

  17. Ice discharge from north and northeast Greenland using ERS data

    NASA Technical Reports Server (NTRS)

    Rignot, Eric

    1997-01-01

    Ice discharge from north and northeast Greenland glaciers was calculated at the grounding line using ERS radar interferometry data acquired during the tandem phase. The resulting estimates exceed the production of icebergs at the glacier fronts by a factor of 3.5. This large decrease in ice flux is attributed to extensive melting at the underside of the floating sections. When compared to the predicted grounding line ice discharge of an ice sheet in balance, the results show an excess of 28 cubic km/yr of ice lost to the ocean. The north and northeast sectors of the Greenland ice sheet are therefore thinning and contributing positively to sea-level rise.

  18. Ice discharge from north and northeast Greenland using ERS data

    NASA Technical Reports Server (NTRS)

    Rignot, Eric

    1997-01-01

    Ice discharge from north and northeast Greenland glaciers was calculated at the grounding line using ERS radar interferometry data acquired during the tandem phase. The resulting estimates exceed the production of icebergs at the glacier fronts by a factor of 3.5. This large decrease in ice flux is attributed to extensive melting at the underside of the floating sections. When compared to the predicted grounding line ice discharge of an ice sheet in balance, the results show an excess of 28 cubic km/yr of ice lost to the ocean. The north and northeast sectors of the Greenland ice sheet are therefore thinning and contributing positively to sea-level rise.

  19. Glacier calving, dynamics, and sea-level rise. Final report

    SciTech Connect

    Meier, M.F.; Pfeffer, W.T.; Amadei, B.

    1998-08-01

    The present-day calving flux from Greenland and Antarctica is poorly known, and this accounts for a significant portion of the uncertainty in the current mass balance of these ice sheets. Similarly, the lack of knowledge about the role of calving in glacier dynamics constitutes a major uncertainty in predicting the response of glaciers and ice sheets to changes in climate and thus sea level. Another fundamental problem has to do with incomplete knowledge of glacier areas and volumes, needed for analyses of sea-level change due to changing climate. The authors proposed to develop an improved ability to predict the future contributions of glaciers to sea level by combining work from four research areas: remote sensing observations of calving activity and iceberg flux, numerical modeling of glacier dynamics, theoretical analysis of the calving process, and numerical techniques for modeling flow with large deformations and fracture. These four areas have never been combined into a single research effort on this subject; in particular, calving dynamics have never before been included explicitly in a model of glacier dynamics. A crucial issue that they proposed to address was the general question of how calving dynamics and glacier flow dynamics interact.

  20. Laser altimetry reveals complex pattern of Greenland Ice Sheet dynamics

    PubMed Central

    Csatho, Beata M.; Schenk, Anton F.; van der Veen, Cornelis J.; Babonis, Gregory; Duncan, Kyle; Rezvanbehbahani, Soroush; van den Broeke, Michiel R.; Simonsen, Sebastian B.; Nagarajan, Sudhagar; van Angelen, Jan H.

    2014-01-01

    We present a new record of ice thickness change, reconstructed at nearly 100,000 sites on the Greenland Ice Sheet (GrIS) from laser altimetry measurements spanning the period 1993–2012, partitioned into changes due to surface mass balance (SMB) and ice dynamics. We estimate a mean annual GrIS mass loss of 243 ± 18 Gt⋅y−1, equivalent to 0.68 mm⋅y−1 sea level rise (SLR) for 2003–2009. Dynamic thinning contributed 48%, with the largest rates occurring in 2004–2006, followed by a gradual decrease balanced by accelerating SMB loss. The spatial pattern of dynamic mass loss changed over this time as dynamic thinning rapidly decreased in southeast Greenland but slowly increased in the southwest, north, and northeast regions. Most outlet glaciers have been thinning during the last two decades, interrupted by episodes of decreasing thinning or even thickening. Dynamics of the major outlet glaciers dominated the mass loss from larger drainage basins, and simultaneous changes over distances up to 500 km are detected, indicating climate control. However, the intricate spatiotemporal pattern of dynamic thickness change suggests that, regardless of the forcing responsible for initial glacier acceleration and thinning, the response of individual glaciers is modulated by local conditions. Recent projections of dynamic contributions from the entire GrIS to SLR have been based on the extrapolation of four major outlet glaciers. Considering the observed complexity, we question how well these four glaciers represent all of Greenland’s outlet glaciers. PMID:25512537

  1. Susitna Glacier, Alaska

    NASA Image and Video Library

    2010-09-13

    Folds in the lower reaches of valley glaciers can be caused by powerful surges of tributary ice streams. This phenomenon is spectacularly displayed by the Sustina Glacier in the Alaska Range as seen by NASA Terra spacecraft.

  2. A model for tidewater glacier undercutting by submarine melting

    NASA Astrophysics Data System (ADS)

    Slater, D. A.; Nienow, P. W.; Goldberg, D. N.; Cowton, T. R.; Sole, A. J.

    2017-03-01

    Dynamic change at the marine-terminating margins of the Greenland Ice Sheet may be initiated by the ocean, particularly where subglacial runoff drives vigorous ice-marginal plumes and rapid submarine melting. Here we model submarine melt-driven undercutting of tidewater glacier termini, simulating a process which is key to understanding ice-ocean coupling. Where runoff emerges from broad subglacial channels we find that undercutting has only a weak impact on local submarine melt rate but increases total ablation by submarine melting due to the larger submerged ice surface area. Thus, the impact of melting is determined not only by the melt rate magnitude but also by the slope of the ice-ocean interface. We suggest that the most severe undercutting occurs at the maximum height in the fjord reached by the plume, likely promoting calving of ice above. It remains unclear, however, whether undercutting proceeds sufficiently rapidly to influence calving at Greenland's fastest-flowing glaciers.

  3. Use of Glacial Fronts by Narwhals (Monodon monoceros) in West Greenland

    NASA Astrophysics Data System (ADS)

    Laidre, K. L.

    2015-12-01

    Glacial fronts in Greenland are known to be important summer habitat for narwhals (Monodon monoceros), as freshwater runoff and sediment discharge may aggregate prey at the terminus. We investigated the importance of glacial habitat characteristics in determining narwhal visitation. Narwhals (n=18) were instrumented with satellite transmitters in September 1993-1994 and 2006-2007 in Melville Bay, West Greenland. Daily narwhal locations were interpolated using a correlated random walk based on observed filtered locations and associated positional error. We also compiled a database on physical features of 41 glaciers along the northwest Greenland coast. This covered the entire coastal region with narwhal activity. Parameters included glacier ice velocity (km/yr) from radar satellite data, glacier front advance and retreat, and glacier width (km) at the ice-ocean interface derived using front position data digitized from 20-100m resolution radar image mosaics and Landsat imagery. We also quantified relative volumes and extent of glacial ice discharge, thickness of the glacial ice at the terminus (m), and water depth at the terminus (m) from gravity and airborne radar data, sediment flux from satellite-based analysis, and freshwater runoff from a regional atmospheric climate model (RACMO2.3). We quantified whale visits to glaciers at three distances (5, 7, and 10 km) and conducted proximity analyses on annual and monthly time steps. We estimated 1) narwhal presence or absence, 2) the number of 24 h periods spent at glaciers, and 3) the fraction of study animals that visited each glacier. The use of glacial habitat by narwhals expanded to the north and south between the 1990s (n=9 unique glaciers visited) and the 2000s (n=30 visited), likely due to loss of summer fast ice and later fall freeze-up trends (3.5 weeks later since 1979). We used a generalized linear mixed effects framework to quantify the glacier and fjord habitat characteristics preferred by narwhals.

  4. Spatial variation in energy exchange across coastal environments in Greenland

    NASA Astrophysics Data System (ADS)

    Lund, M.; Abermann, J.; Citterio, M.; Hansen, B. U.; Larsen, S. H.; Stiegler, C.; Sørensen, L. L.; van As, D.

    2015-12-01

    The surface energy partitioning in Arctic terrestrial and marine areas is a crucial process, regulating snow, glacier ice and sea ice melt, and permafrost thaw, as well as modulating Earth's climate on both local, regional, and eventually, global scales. The Arctic region has warmed approximately twice as much as the global average, due to a number of feedback mechanisms related to energy partitioning, most importantly the snow and ice-albedo feedback. However, direct measurements of surface energy budgets in the Arctic are scarce, especially for the cold and dark winter period and over transects going from the ice sheet and glaciers to the sea. This study aims to describe annual cycles of the surface energy budget from various surface types in Arctic Greenland; e.g. glacier, snow, wet and dry tundra and sea ice, based on data from a number of measurement locations across coastal Greenland related to the Greenland Ecosystem Monitoring (GEM) program, including Station Nord/Kronprins Christians Land, Zackenberg/Daneborg, Disko, Qaanaq, Nuuk/Kobbefjord and Upernaviarsuk. Based on the available time series, we will analyze the sensitivity of the energy balance partitioning to variations in meteorological conditions (temperature, cloudiness, precipitation). Such analysis would allow for a quantification of the spatial variation in the energy exchange in aforementioned Arctic environments. Furthermore, this study will identify uncertainties and knowledge gaps in Arctic energy budgets and related climate feedback effects.

  5. Role of ice-ocean interaction on glacier instability: Results from numerical modelling applied to Petermann Glacier

    NASA Astrophysics Data System (ADS)

    Nick, Faezeh M.; Hubbard, Alun; van der Veen, Kees; Vieli, Andreas

    2010-05-01

    Calving of icebergs and bottom melting from ice shelves accounts for roughly half the ice transferred from the Greenland Ice Sheet into the surrounding ocean, and virtually all of the ice loss from the Antarctic Ice Sheet. Petermann Glacier (north Greenland) with its 16 km wide and 80 km long floating tongue, experiences massive bottom melting. We apply a numerical ice flow model using a physically-based calving criterion based on crevasse depth to investigate the contribution of processes such as bottom melting, sea ice or sikkusak disintegration, surface run off and iceberg calving to the mass balance and instability of Petermann Glacier and its ice shelf. Our modelling study provides insights into the role of ice-ocean interaction, and on how to incorporate calving in ice sheet models, improving our ability to predict future ice sheet change.

  6. Role of ice-ocean interaction on glacier instability: Results from numerical modeling applied to Petermann Glacier (Invited)

    NASA Astrophysics Data System (ADS)

    Nick, F.; Hubbard, A.; Vieli, A.; van der Veen, C. J.; Box, J. E.; Bates, R.; Luckman, A. J.

    2009-12-01

    Calving of icebergs and bottom melting from ice shelves accounts for roughly half the ice transferred from the Greenland Ice Sheet into the surrounding ocean, and virtually all of the ice loss from the Antarctic Ice Sheet. Petermann Glacier (north Greenland) with its 16 km wide and 80 km long floating tongue, experiences massive bottom melting. We apply a numerical ice flow model using a physically-based calving criterion based on crevasse depth to investigate the contribution of processes such as bottom melting, sea ice or sikkusak disintegration, surface run off and iceberg calving to the mass balance and instability of Petermann Glacier and its ice shelf. Our modeling study provides insights into the role of ice-ocean interaction, and on how to incorporate calving in ice sheet models, improving our ability to predict future ice sheet change.

  7. Greenland as seen by the STS-66 shuttle Atlantis

    NASA Image and Video Library

    1994-11-14

    This north-looking view of southwestern Greenland was taken in November, 1994, and shows numerous indentations, many of which contain small settlements. These fjords were carved by the glaciers of the last ice age 10,000 years ago. Even today, the ice in the center of Greenland is nearly 3,500 meters (11,000 feet) thick and great rivers of ice continuously flow down toward the sea, where they melt or break off as icebergs. Some Icebergs exceed the size of small islands, weigh several million tons, and rise several hundred feet above the sea surface. Cape Farewell is visible toward the bottom right of the view. Julianehab Bay and the Bredev fjord can be seen toward the center of the photograph. Godthab, the main settlement on Greenland, is barely visible to the north of the Frederikeshabs Icefield near the left center of the view.

  8. Greenland as seen by the STS-66 shuttle Atlantis

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This north-looking view of southwestern Greenland was taken in November, 1994, and shows numerous indentations, many of which contain small settlements. These fjords were carved by the glaciers of the last ice age 10,000 years ago. Even today, the ice in the center of Greenland is nearly 3,500 meters (11,000 feet) thick and great rivers of ice continuously flow down toward the sea, where they melt or break off as icebergs. Some Icebergs exceed the size of small islands, weigh several million tons, and rise several hundred feet above the sea surface. Cape Farewell is visible toward the bottom right of the view. Julianehab Bay and the Bredev fjord can be seen toward the center of the photograph. Godthab, the main settlement on Greenland, is barely visible to the north of the Frederikeshabs Icefield near the left center of the view.

  9. NASA's Oceans Melting Greenland (OMG) mission: Year 2 Mission Update

    NASA Astrophysics Data System (ADS)

    Willis, J. K.; Rignot, E. J.; Fenty, I. G.; Schodlok, M.; Fukumori, I.; Khazendar, A.; Moller, D.; Thompson, A. F.; Holland, D.; Morison, J.; Tinto, K. J.; Forsberg, R.; Jakobsson, M.; Muenchow, A.; Dinardo, S. J.

    2016-12-01

    Oceans Melting Greenland (OMG) is an airborne NASA Mission to investigate the role of the oceans in ice loss around the margins of the Greenland Ice Sheet. A five-year campaign, OMG will directly measure ocean warming and glacier retreat around all of Greenland. By relating these two, we will explore one of the most pressing open questions about how climate change drives sea level rise: How quickly are the warming oceans melting the Greenland from the edges? Now in its second year, we update the community on the mission's status. Since 2015, we (1) conducted our first pan-shelf in situ temperature and salinity measurement campaign using 250 Airborne eXpendable Conductivity-Temperature-Depth (AXCTD) probes, (2) completed the mission's seafloor mapping campaign using a combination of multibeam echosounding sonar for glacial fjords and airborne gravimetry on the continental shelf, and (3) conducted our first pan-ice sheet glacier elevation survey using high-resolution radar interferometry. Highlights from these campaigns are presented as well as a timeline for the mission's remaining four years.

  10. Greenland ice sheet motion insensitive to exceptional meltwater forcing.

    PubMed

    Tedstone, Andrew J; Nienow, Peter W; Sole, Andrew J; Mair, Douglas W F; Cowton, Thomas R; Bartholomew, Ian D; King, Matt A

    2013-12-03

    Changes to the dynamics of the Greenland ice sheet can be forced by various mechanisms including surface-melt-induced ice acceleration and oceanic forcing of marine-terminating glaciers. We use observations of ice motion to examine the surface melt-induced dynamic response of a land-terminating outlet glacier in southwest Greenland to the exceptional melting observed in 2012. During summer, meltwater generated on the Greenland ice sheet surface accesses the ice sheet bed, lubricating basal motion and resulting in periods of faster ice flow. However, the net impact of varying meltwater volumes upon seasonal and annual ice flow, and thus sea level rise, remains unclear. We show that two extreme melt events (98.6% of the Greenland ice sheet surface experienced melting on July 12, the most significant melt event since 1889, and 79.2% on July 29) and summer ice sheet runoff ~3.9 σ above the 1958-2011 mean resulted in enhanced summer ice motion relative to the average melt year of 2009. However, despite record summer melting, subsequent reduced winter ice motion resulted in 6% less net annual ice motion in 2012 than in 2009. Our findings suggest that surface melt-induced acceleration of land-terminating regions of the ice sheet will remain insignificant even under extreme melting scenarios.

  11. 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.

  12. Greenland ice sheet motion insensitive to exceptional meltwater forcing

    PubMed Central

    Tedstone, Andrew J.; Nienow, Peter W.; Sole, Andrew J.; Mair, Douglas W. F.; Cowton, Thomas R.; Bartholomew, Ian D.; King, Matt A.

    2013-01-01

    Changes to the dynamics of the Greenland ice sheet can be forced by various mechanisms including surface-melt–induced ice acceleration and oceanic forcing of marine-terminating glaciers. We use observations of ice motion to examine the surface melt–induced dynamic response of a land-terminating outlet glacier in southwest Greenland to the exceptional melting observed in 2012. During summer, meltwater generated on the Greenland ice sheet surface accesses the ice sheet bed, lubricating basal motion and resulting in periods of faster ice flow. However, the net impact of varying meltwater volumes upon seasonal and annual ice flow, and thus sea level rise, remains unclear. We show that two extreme melt events (98.6% of the Greenland ice sheet surface experienced melting on July 12, the most significant melt event since 1889, and 79.2% on July 29) and summer ice sheet runoff ∼3.9σ above the 1958–2011 mean resulted in enhanced summer ice motion relative to the average melt year of 2009. However, despite record summer melting, subsequent reduced winter ice motion resulted in 6% less net annual ice motion in 2012 than in 2009. Our findings suggest that surface melt–induced acceleration of land-terminating regions of the ice sheet will remain insignificant even under extreme melting scenarios. PMID:24248343

  13. Expected ICESat measurement of glacier elevation change

    NASA Astrophysics Data System (ADS)

    Mitchell, D.; Sauber, J.; Harding, D.; Carabajal, C.; Krabill, W.; Manizade, S.; Bufton, J.

    2003-04-01

    The Ice, Cloud, and land Elevation Satellite (ICESat), part of NASA's Earth Observing System, was launched on 01-12-03. ICESat will measure, among other things, ice sheet elevations and changes in elevation through time [{Zwally et al.,} 2002]. ICESat elevation profiles will consist of the centroid elevations of {symbol{"7E}}70 m diameter laser footprints, with a predicted vertical accuracy of {symbol{"7E}}15 cm; the footprints will be separated by 172 m along track. By controlling spacecraft roll attitude, the laser footprint will precisely follow the same reference ground track ("exact repeat mode") for each cycle. Between one exact repeat track and the track during the next cycle, footprint location offsets of {symbol{"7E}}60 m (2σ) across track and up to {symbol{"7E}}86 m along track could occur. While ICESat's primary goal is to measure the vast ice sheets, outlet glaciers in Greenland and the Antarctic Peninsula as well as the mountain glaciers (ex. Alaska and Patagonia) represent a sensitive indicator of climate change. These glaciers, however, generally have rougher surfaces and steeper slopes than the ice sheets, which ICESat was designed to measure. In this study we evaluate ICESat performance over these dynamic ice surfaces by using aircraft laser altimetry profiles along the fast-moving Jakobshavn glacier of west central Greenland to simulate ICESat centroid elevations and other parameters. We used high-resolution laser altimetry data acquired with a P3 aircraft over Jakobshavn Glacier in 1997 and 2001 [{Krabill et al.,} 2000] to create 5 m per pixel digital elevation models (DEMs) for both years. Regions of repeated coverage indicate large elevation decreases over the 1997-2001 interval, ranging from 18-47 m, 2-17 km from the 2001 terminus, to 11-28 m, 22-27 km from the 2001 terminus. We examined the elevation centroid and variance as a function of distance from the glacier terminus for individual target regions. With the ICESat offset errors given

  14. Glacier Ecosystems of Himalaya

    NASA Astrophysics Data System (ADS)

    Kohshima, S.; Yoshimura, Y.; Takeuchi, N.; Segawa, T.; Uetake, J.

    2012-12-01

    Biological activity on glaciers has been believed to be extremely limited. However, we found various biotic communities specialized to the glacier environment in various part of the world, such as Himalaya, Patagonia and Alaska. Some of these glacier hosted biotic communities including various cold-tolerant insects, annelids and copepods that were living in the glacier by feeding on algae and bacteria growing in the snow and ice. Thus, the glaciers are simple and relatively closed ecosystems sustained by the primary production in the snow and ice. In this presentation, we will briefly introduce glacier ecosystems in Himalaya; ecology and behavior of glacier animals, altitudinal zonation of snow algal communities, and the structure of their habitats in the glacier. Since the microorganisms growing on the glacier surface are stored in the glacial strata every year, ice-core samples contain many layers with these microorganisms. We showed that the snow algae in the ice-core are useful for ice core dating and could be new environmental signals for the studies on past environment using ice cores. These microorganisms in the ice core will be important especially in the studies of ice core from the glaciers of warmer regions, in which chemical and isotopic contents are often heavily disturbed by melt water percolation. Blooms of algae and bacteria on the glacier can reduce the surface albedo and significantly affect the glacier melting. For example, the surface albedo of some Himalayan glaciers was significantly reduced by a large amount of dark-colored biogenic material (cryoconite) derived from snow algae and bacteria. It increased the melting rates of the surfaces by as much as three-fold. Thus, it was suggested that the microbial activity on the glacier could affect the mass balance and fluctuation of the glaciers.

  15. Stable microbial community composition on the Greenland Ice Sheet.

    PubMed

    Musilova, Michaela; Tranter, Martyn; Bennett, Sarah A; Wadham, Jemma; Anesio, Alexandre M

    2015-01-01

    The first molecular-based studies of microbes in snow and on glaciers have only recently been performed on the vast Greenland Ice Sheet (GrIS). Aeolian microbial seeding is hypothesized to impact on glacier surface community compositions. Localized melting of glacier debris (cryoconite) into the surface ice forms cryoconite holes, which are considered 'hot spots' for microbial activity on glaciers. To date, few studies have attempted to assess the origin and evolution of cryoconite and cryoconite hole communities throughout a melt season. In this study, a range of experimental approaches was used for the first time to study the inputs, temporal and structural transformations of GrIS microbial communities over the course of a whole ablation season. Small amounts of aeolian (wind and snow) microbes were potentially seeding the stable communities that were already present on the glacier (composed mainly of Proteobacteria, Cyanobacteria, and Actinobacteria). However, the dominant bacterial taxa in the aeolian samples (Firmicutes) did not establish themselves in local glacier surface communities. Cryoconite and cryoconite hole community composition remained stable throughout the ablation season following the fast community turnover, which accompanied the initial snow melt. The presence of stable communities in cryoconite and cryoconite holes on the GrIS will allow future studies to assess glacier surface microbial diversity at individual study sites from sampling intervals of short duration only. Aeolian inputs also had significantly different organic δ(13)C values (-28.0 to -27.0‰) from the glacier surface values (-25.7 to -23.6‰), indicating that in situ microbial processes are important in fixing new organic matter and transforming aeolian organic carbon. The continuous productivity of stable communities over one melt season makes them important contributors to biogeochemical nutrient cycling on glaciers.

  16. Stable microbial community composition on the Greenland Ice Sheet

    PubMed Central

    Musilova, Michaela; Tranter, Martyn; Bennett, Sarah A.; Wadham, Jemma; Anesio, Alexandre M.

    2015-01-01

    The first molecular-based studies of microbes in snow and on glaciers have only recently been performed on the vast Greenland Ice Sheet (GrIS). Aeolian microbial seeding is hypothesized to impact on glacier surface community compositions. Localized melting of glacier debris (cryoconite) into the surface ice forms cryoconite holes, which are considered ‘hot spots’ for microbial activity on glaciers. To date, few studies have attempted to assess the origin and evolution of cryoconite and cryoconite hole communities throughout a melt season. In this study, a range of experimental approaches was used for the first time to study the inputs, temporal and structural transformations of GrIS microbial communities over the course of a whole ablation season. Small amounts of aeolian (wind and snow) microbes were potentially seeding the stable communities that were already present on the glacier (composed mainly of Proteobacteria, Cyanobacteria, and Actinobacteria). However, the dominant bacterial taxa in the aeolian samples (Firmicutes) did not establish themselves in local glacier surface communities. Cryoconite and cryoconite hole community composition remained stable throughout the ablation season following the fast community turnover, which accompanied the initial snow melt. The presence of stable communities in cryoconite and cryoconite holes on the GrIS will allow future studies to assess glacier surface microbial diversity at individual study sites from sampling intervals of short duration only. Aeolian inputs also had significantly different organic δ13C values (-28.0 to -27.0‰) from the glacier surface values (-25.7 to -23.6‰), indicating that in situ microbial processes are important in fixing new organic matter and transforming aeolian organic carbon. The continuous productivity of stable communities over one melt season makes them important contributors to biogeochemical nutrient cycling on glaciers. PMID:25852658

  17. Glacier response to North Atlantic climate variability during the Holocene

    NASA Astrophysics Data System (ADS)

    Balascio, N. L.; D'Andrea, W. J.; Bradley, R. S.

    2015-12-01

    Small glaciers and ice caps respond rapidly to climate variations, and records of their past extent provide information on the natural envelope of past climate variability. Millennial-scale trends in Holocene glacier size are well documented and correspond with changes in Northern Hemisphere summer insolation. However, there is only sparse and fragmentary evidence for higher-frequency variations in glacier size because in many Northern Hemisphere regions glacier advances of the past few hundred years were the most extensive and destroyed the geomorphic evidence of ice growth and retreat during the past several thousand years. Thus, most glacier records have been of limited use for investigating centennial-scale climate forcing and feedback mechanisms. Here we report a continuous record of glacier activity for the last 9.5 ka from southeast Greenland derived from high-resolution measurements on a proglacial lake sediment sequence. Physical and geochemical parameters show that the glaciers responded to previously documented Northern Hemisphere climatic excursions, including the "8.2 ka" cooling event, the Holocene Thermal Maximum, Neoglacial cooling, and 20th century warming. In addition, the sediments indicate centennial-scale oscillations in glacier size during the late Holocene. Beginning at 4.1 ka, a series of abrupt glacier advances occurred, each lasting ~100 years and followed by a period of retreat, that were superimposed on a gradual trend toward larger glacier size. Thus, while declining summer insolation caused long-term cooling and glacier expansion during the late Holocene, climate system dynamics resulted in repeated episodes of glacier expansion and retreat on multi-decadal to centennial timescales. These episodes coincided with ice rafting events in the North Atlantic Ocean and periods of regional ice cap expansion, which confirms their regional significance and indicates that considerable glacier activity on these timescales is a normal feature of

  18. Variations in Sr and Nd isotopic ratios of mineral particles in cryoconite in western Greenland

    NASA Astrophysics Data System (ADS)

    Nagatsuka, Naoko; Takeuchi, Nozomu; Uetake, Jun; Shimada, Rigen; Onuma, Yukihiko; Tanaka, Sota; Nakano, Takanori

    2016-11-01

    In order to better understand the source of minerals on the dark-colored ice, located in the Greenland ice sheet ablation zone, we analyzed the Sr and Nd isotopic ratios of minerals in cryoconite, which were collected from glaciers in northwest and southwest Greenland. We focused on the following: (i) comparison of the isotopes of minerals in cyroconite with those in sediments from local and distant areas, (ii) regional variations in western Greenland, and (iii) spatial variations across an individual a glacier. The mineral components of the cryoconite showed variable Sr and Nd isotopic ratios (87Sr/86Sr: 0.711335 to 0.742406, ɛNd (0): -33.1 to -22.9), which corresponded to those of the englacial dust and moraine on and around the glaciers but were significantly different from those of the distant deserts that have been considered to be primary sources of mineral dust on the Greenland Ice Sheet. This suggests that the minerals within the cryoconites were mainly derived from local sediments, rather than from distant areas. The Sr ratios in the northwestern region were significantly higher than those in the southwestern region. This is probably due to geological differences in the source areas, such as the surrounding glaciers in each region. The isotopic ratios further varied spatially within a glacier (Qaanaaq and Kangerlussuaq areas), indicating that the silicate minerals on the glaciers were derived not from a single source but from multiple sources, such as englacial dust and wind-blown minerals from the moraine surrounding the glaciers.

  19. Extensive dynamic thinning on the margins of the Greenland and Antarctic ice sheets.

    PubMed

    Pritchard, Hamish D; Arthern, Robert J; Vaughan, David G; Edwards, Laura A

    2009-10-15

    Many glaciers along the margins of the Greenland and Antarctic ice sheets are accelerating and, for this reason, contribute increasingly to global sea-level rise. Globally, ice losses contribute approximately 1.8 mm yr(-1) (ref. 8), but this could increase if the retreat of ice shelves and tidewater glaciers further enhances the loss of grounded ice or initiates the large-scale collapse of vulnerable parts of the ice sheets. Ice loss as a result of accelerated flow, known as dynamic thinning, is so poorly understood that its potential contribution to sea level over the twenty-first century remains unpredictable. Thinning on the ice-sheet scale has been monitored by using repeat satellite altimetry observations to track small changes in surface elevation, but previous sensors could not resolve most fast-flowing coastal glaciers. Here we report the use of high-resolution ICESat (Ice, Cloud and land Elevation Satellite) laser altimetry to map change along the entire grounded margins of the Greenland and Antarctic ice sheets. To isolate the dynamic signal, we compare rates of elevation change from both fast-flowing and slow-flowing ice with those expected from surface mass-balance fluctuations. We find that dynamic thinning of glaciers now reaches all latitudes in Greenland, has intensified on key Antarctic grounding lines, has endured for decades after ice-shelf collapse, penetrates far into the interior of each ice sheet and is spreading as ice shelves thin by ocean-driven melt. In Greenland, glaciers flowing faster than 100 m yr(-1) thinned at an average rate of 0.84 m yr(-1), and in the Amundsen Sea embayment of Antarctica, thinning exceeded 9.0 m yr(-1) for some glaciers. Our results show that the most profound changes in the ice sheets currently result from glacier dynamics at ocean margins.

  20. Prokaryotic diversity in sediments beneath two polar glaciers with contrasting organic carbon substrates.

    PubMed

    Stibal, Marek; Hasan, Fariha; Wadham, Jemma L; Sharp, Martin J; Anesio, Alexandre M

    2012-03-01

    Microbial ecosystems beneath glaciers and ice sheets are thought to play an active role in regional and global carbon cycling. Subglacial sediments are assumed to be largely anoxic, and thus various pathways of organic carbon metabolism may occur here. We examine the abundance and diversity of prokaryotes in sediment beneath two glaciers (Lower Wright Glacier in Antarctica and Russell Glacier in Greenland) with different glaciation histories and thus with different organic carbon substrates. The total microbial abundance in the Lower Wright Glacier sediment, originating from young lacustrine sediment, was an order of magnitude higher (~8 × 10(6) cells per gram of wet sediment) than in Russell Glacier sediment (~9 × 10(5) cells g(-1)) that is of Holocene-aged soil origin. 4% of the microbes from the Russell Glacier sediment and 0.04-0.35% from Lower Wright Glacier were culturable at 10°C. The Lower Wright Glacier subglacial community was dominated by Proteobacteria, followed by Firmicutes. The Russell Glacier library was much less diverse and also dominated by Proteobacteria. Low numbers and diversity of both Euryarchaeota and Crenarchaeota were found in both sediments. The identified clones were related to bacteria with both aerobic and anaerobic metabolisms, indicating the presence of both oxic and anoxic conditions in the sediments.

  1. Linking the spatial variability of glacier mass loss to fjord geometry

    NASA Astrophysics Data System (ADS)

    Porter, D. F.; Tinto, K. J.; Boghosian, A.; Cochran, J. R.; Csatho, B. M.; Bell, R. E.

    2015-12-01

    There is compelling evidence of increasing mass loss of the ice sheets using a diverse set of observations, including increased thinning rates measured from both airborne and satellite altimeters, elevated mass fluxes resulting from the acceleration of outlet glaciers, and mass changes measured directly from satellite gravimetry. A dominant characteristic of observed change in Greenland outlet glaciers is that it is locally random. Numerous studies have revealed a high degree of spatial and temporal variability of outlet glacier mass change. Modeling studies suggest that increased ocean temperatures may be responsible for the observed glacial retreat in Greenland through increased basal melting, leading to increased calving rates, terminus retreat, glacier speedup, and eventually thinning of inland ice. Knowledge of fjord geometry is crucial for ice-ocean interaction because the availability of ocean heat to the ice will be restricted by narrow sills and shallow grounding lines. We investigate whether the variability in observed changes among Greenland glaciers can be partially explained by variation in fjord geometry. Using statistical techniques commonly employed to detect patterns in complex spatial data, we objectively show that mass change in Greenland tidewater glaciers between 2003 and 2009 is indeed mostly spatially incoherent. Except for a few clusters of similar change in the NW and Scoresby Sund regions, there is significant glacier-scale variability in mass loss rates. To understand the drivers of this local variability, we compare fjord bathymetries from all regions of Greenland, modeled using airborne gravimetry measurements from NASA Operation IceBridge flights, to estimates of glaciological change. Specifically, we investigate the correlation between water depths at the grounding line and the dynamic mass loss of tidewater glaciers. In theory, a deep grounding line will allow greater interaction with the warm Atlantic Water observed in most fjords

  2. Grounding line migration of Petermann Gletscher, north Greenland, detected using satellite radar interferometry

    NASA Technical Reports Server (NTRS)

    Rignot, Eric

    1997-01-01

    Ice Sheet grounding lines are sensitive indicator of changes in ice thickness, sea level or elevation of the sea bed. Here, we use the synthetic-aperture radar interferometry technique to detect the migration of thel imit of tidal flexing, or hinge line, of Petermann Gletscher, a major outlet glacier of north Greenland which develops an extensive floating tongue.

  3. Grounding line migration of Petermann Gletscher, north Greenland, detected using satellite radar interferometry

    NASA Technical Reports Server (NTRS)

    Rignot, Eric

    1997-01-01

    Ice Sheet grounding lines are sensitive indicator of changes in ice thickness, sea level or elevation of the sea bed. Here, we use the synthetic-aperture radar interferometry technique to detect the migration of thel imit of tidal flexing, or hinge line, of Petermann Gletscher, a major outlet glacier of north Greenland which develops an extensive floating tongue.

  4. Exploring glacial change - flying in the tailwind of the early 20th century Greenland explorers

    NASA Astrophysics Data System (ADS)

    Bjork, A. A.; Kjaer, K.; Kjeldsen, K. K.; Larsen, N. K.; Korsgaard, N. J.; Khan, S. A.

    2013-12-01

    In the early 1930s Greenlandic explorers and scientists began using airplanes as an effective mean of surveying and mapping the hitherto unknown and inaccessible lands. By replacing the dogsled and the drawing board with the seaplane and camera, huge areas could now be covered. Here in the 21st Century the photographs now serve as a snapshot of the state of the glaciers, and possess unique scientific value as they stand as the first testimony of hundreds of Greenlandic glaciers. In the summer of 2013, we flew in the paths of the early flights and captured the changes that occurred during the last 80 years. To revisit all the historic glaciers would be a near impossible, not to mention extremely expensive task, so we targeted the most important glaciers in terms of present mass loss as well as the most aesthetically appealing historical images. The result is a then-and-now comparison that vividly captures both the raw beauty of the land and the ongoing often dramatic glacial changes. As the historic flights covered nearly half the Greenlandic coast line, we capture both areas of massive retreat and areas of still stand and even advance. The Heinkel Seaplane is being prepared for a photo flight in southeast Greenland in 1933. Flying an open plane in 14.000 ft and -40 °C called for a special breed of pilots.

  5. Context for the Recent Massive Petermann Glacier Calving Event

    NASA Astrophysics Data System (ADS)

    Falkner, Kelly K.; Melling, Humfrey; Münchow, Andreas M.; Box, Jason E.; Wohlleben, Trudy; Johnson, Helen L.; Gudmandsen, Preben; Samelson, Roger; Copland, Luke; Steffen, Konrad; Rignot, Eric; Higgins, Anthony K.

    2011-04-01

    On 4 August 2010, about one fifth of the floating ice tongue of Petermann Glacier (also known as “Petermann Gletscher”) in northwestern Greenland calved (Figure 1). The resulting “ice island” had an area approximately 4 times that of Manhattan Island (about 253±17 square kilometers). The ice island garnered much attention from the media, politicians, and the public, who raised concerns about downstream implications for shipping, offshore oil and gas operations, and possible connections to Arctic and global warming. Does this event signal a change in the glacier's dynamics? Or can it be characterized as part of the glacier's natural variability? Understanding the known historical context of this event allows scientists and the public to judge its significance.

  6. Glaciers of Asia

    USGS Publications Warehouse

    Williams, Richard S., Jr.; Ferrigno, Jane G.

    2010-01-01

    This chapter is the ninth to be released in U.S. Geological Survey Professional Paper 1386, Satellite Image Atlas of Glaciers of the World, a series of 11 chapters. In each of the geographic area chapters, remotely sensed images, primarily from the Landsat 1, 2, and 3 series of spacecraft, are used to analyze the specific glacierized region of our planet under consideration and to monitor glacier changes. Landsat images, acquired primarily during the middle to late 1970s and early 1980s, were used by an international team of glaciologists and other scientists to study various geographic regions and (or) to discuss related glaciological topics. In each glacierized geographic region, the present areal distribution of glaciers is compared, wherever possible, with historical information about their past extent. The atlas provides an accurate regional inventory of the areal extent of glacier ice on our planet during the 1970s as part of a growing international scientific effort to measure global environmental change on the Earth?s surface. The chapter is divided into seven geographic parts and one topical part: Glaciers of the Former Soviet Union (F-1), Glaciers of China (F-2), Glaciers of Afghanistan (F?3), Glaciers of Pakistan (F-4), Glaciers of India (F-5), Glaciers of Nepal (F?6), Glaciers of Bhutan (F-7), and the Paleoenvironmental Record Preserved in Middle-Latitude, High-Mountain Glaciers (F-8). Each geographic section describes the glacier extent during the 1970s and 1980s, the benchmark time period (1972-1981) of this volume, but has been updated to include more recent information. Glaciers of the Former Soviet Union are located in the Russian Arctic and various mountain ranges of Russia and the Republics of Georgia, Kyrgyzstan, Tajikistan, and Kazakstun. The Glacier Inventory of the USSR and the World Atlas of Ice and Snow Resources recorded a total of 28,881 glaciers covering an area of 78,938 square kilometers (km2). China includes many of the mountain-glacier

  7. Afghanistan Glacier Diminution

    NASA Astrophysics Data System (ADS)

    Shroder, J. F.; Bishop, M.; Haritashya, U.; Olsenholler, J.

    2008-12-01

    Glaciers in Afghanistan represent a late summer - early fall source of melt water for late season crop irrigation in a chronically drought-torn region. Precise river discharge figures associated with glacierized drainage basins are generally unavailable because of the destruction of hydrological gauging stations built in pre-war times although historic discharge data and prior (1960s) mapped glacier regions offer some analytical possibilities. The best satellite data sets for glacier-change detection are declassified Cornona and Keyhole satellite data sets, standard Landsat sources, and new ASTER images assessed in our GLIMS (Global Land Ice Measurements from Space) Regional Center for Southwest Asia (Afghanistan and Pakistan). The new hyperspectral remote sensing survey of Afghanistan completed by the US Geological Survey and the Afghanistan Ministry of Mines offers potential for future detailed assessments. Long-term climate change in southwest Asia has decreased precipitation for millennia so that glaciers, rivers and lakes have all declined from prehistoric and historic highs. As many glaciers declined in ice volume, they increased in debris cover until they were entirely debris-covered or became rock glaciers, and the ice was protected thereby from direct solar radiation, to presumably reduce ablation rates. We have made a preliminary assessment of glacier location and extent for the country, with selected, more-detailed, higher-resolution studies underway. In the Great Pamir of the Wakhan Corridor where the largest glaciers occur, we assessed fluctuations of a randomly selected 30 glaciers from 1976 to 2003. Results indicate that 28 glacier-terminus positions have retreated, and the largest average retreat rate was 36 m/yr. High albedo, non-vegetated glacier forefields formed prior to 1976, and geomorphological evidence shows apparent glacier-surface downwasting after 1976. Climatic conditions and glacier retreat have resulted in disconnection of tributary

  8. Use of glacial fronts by narwhals (Monodon monoceros) in West Greenland.

    PubMed

    Laidre, Kristin L; Moon, Twila; Hauser, Donna D W; McGovern, Richard; Heide-Jørgensen, Mads Peter; Dietz, Rune; Hudson, Ben

    2016-10-01

    Glacial fronts are important summer habitat for narwhals (Monodon monoceros); however, no studies have quantified which glacial properties attract whales. We investigated the importance of glacial habitats using telemetry data from n = 15 whales tagged in September of 1993, 1994, 2006 and 2007 in Melville Bay, West Greenland. For 41 marine-terminating glaciers, we estimated (i) narwhal presence/absence, (ii) number of 24 h periods spent at glaciers and (iii) the fraction of narwhals that visited each glacier (at 5, 7 and 10 km) in autumn. We also compiled data on glacier width, ice thickness, ice velocity, front advance/retreat, area and extent of iceberg discharge, bathymetry, subglacial freshwater run-off and sediment flux. Narwhal use of glacial habitats expanded in the 2000s probably due to reduced summer fast ice and later autumn freeze-up. Using a generalized multivariate framework, glacier ice front thickness (vertical height in the water column) was a significant covariate in all models. A negative relationship with glacier velocity was included in several models and glacier front width was a significant predictor in the 2000s. Results suggest narwhals prefer glaciers with potential for higher ambient freshwater melt over glaciers with silt-laden discharge. This may represent a preference for summer freshwater habitat, similar to other Arctic monodontids. © 2016 The Author(s).

  9. Use of glacial fronts by narwhals (Monodon monoceros) in West Greenland

    PubMed Central

    Moon, Twila; Hauser, Donna D. W.; McGovern, Richard; Heide-Jørgensen, Mads Peter; Dietz, Rune; Hudson, Ben

    2016-01-01

    Glacial fronts are important summer habitat for narwhals (Monodon monoceros); however, no studies have quantified which glacial properties attract whales. We investigated the importance of glacial habitats using telemetry data from n = 15 whales tagged in September of 1993, 1994, 2006 and 2007 in Melville Bay, West Greenland. For 41 marine-terminating glaciers, we estimated (i) narwhal presence/absence, (ii) number of 24 h periods spent at glaciers and (iii) the fraction of narwhals that visited each glacier (at 5, 7 and 10 km) in autumn. We also compiled data on glacier width, ice thickness, ice velocity, front advance/retreat, area and extent of iceberg discharge, bathymetry, subglacial freshwater run-off and sediment flux. Narwhal use of glacial habitats expanded in the 2000s probably due to reduced summer fast ice and later autumn freeze-up. Using a generalized multivariate framework, glacier ice front thickness (vertical height in the water column) was a significant covariate in all models. A negative relationship with glacier velocity was included in several models and glacier front width was a significant predictor in the 2000s. Results suggest narwhals prefer glaciers with potential for higher ambient freshwater melt over glaciers with silt-laden discharge. This may represent a preference for summer freshwater habitat, similar to other Arctic monodontids. PMID:27784729

  10. In Brief: Melting glaciers

    NASA Astrophysics Data System (ADS)

    Showstack, Randy; Tretkoff, Ernie

    2010-12-01

    Glaciers in Patagonia and Alaska have been losing their mass, and for longer than glaciers elsewhere in the world, according to a 7 December report compiled by the United Nations Environment Programme (UNEP). “Climate change is causing significant mass loss of glaciers in high mountains worldwide,” notes the report, which calls for accelerated research, monitoring, and modeling of glaciers and snow and their role in water supplies. The report “also highlights the vulnerability and exposure of people dependent upon [glacier-fed] rivers to floods, droughts and eventually shortages as a result of changes in the melting and freezing cycles linked with climate change and other pollution impacts,” according to UNEP executive director Achim Steiner. For more information, visit http://www.grida.no/publications/high­mountain-glaciers/.

  11. How can we Optimize Global Satellite Observations of Glacier Velocity and Elevation Changes?

    NASA Astrophysics Data System (ADS)

    Willis, M. J.; Pritchard, M. E.; Zheng, W.

    2015-12-01

    We have started a global compilation of glacier surface elevation change rates measured by altimeters and differencing of Digital Elevation Models and glacier velocities measured by Synthetic Aperture Radar (SAR) and optical feature tracking as well as from Interferometric SAR (InSAR). Our goal is to compile statistics on recent ice flow velocities and surface elevation change rates near the fronts of all available glaciers using literature and our own data sets of the Russian Arctic, Patagonia, Alaska, Greenland and Antarctica, the Himalayas, and other locations. We quantify the percentage of the glaciers on the planet that can be regarded as fast flowing glaciers, with surface velocities of more than 50 meters per year, while also recording glaciers that have elevation change rates of more than 2 meters per year. We examine whether glaciers have significant interannual variations in velocities, or have accelerated or stagnated where time series of ice motions are available. We use glacier boundaries and identifiers from the Randolph Glacier Inventory. Our survey highlights glaciers that are likely to react quickly to changes in their mass accumulation rates. The study also identifies geographical areas where our knowledge of glacier dynamics remains poor. Our survey helps guide how frequently observations must be made in order to provide quality satellite-derived velocity and ice elevation observations at a variety of glacier thermal regimes, speeds and widths. Our objectives are to determine to what extent the joint NASA and Indian Space Research Organization Synthetic Aperture Radar mission (NISAR) will be able to provide global precision coverage of ice speed changes and to determine how to optimize observations from the global constellation of satellite missions to record important changes to glacier elevations and velocities worldwide.

  12. The thermophysics of glaciers

    SciTech Connect

    Zotikov, I.A.

    1986-01-01

    This volume presents the results of experimental and theoretical work on the thermodynamics of ice sheets and glaciers. The author has carried out extensive field work in both the Soviet Union and Antarctica over the last 25 years and has contributed to the understanding of the thermophysics of glaciers. The topics covered in this volume embrace heat flow measurement and temperature distributions in glaciers, the thermal drilling of glaciers, the melting and freezing of ice sheets, and other thermophysical problems. Also included are topics of relevance to glacial engineering.

  13. Icefall, Lambert Glacier, Antarctica

    NASA Image and Video Library

    2017-09-27

    Image taken 12/2/2000: The Lambert Glacier in Antarctica, is the world's largest glacier. The focal point of this image is an icefall that feeds into the Lambert glacier from the vast ice sheet covering the polar plateau. Ice flows like water, albeit much more slowly. Cracks can be seen in this icefall as it bends and twists on its slow-motion descent 1300 feet (400 meters) to the glacier below. This Icefall can be found on Landsat 7 WRS Path 42 Row 133/134/135, center: -70.92, 69.15. To learn more about the Landsat satellite go to: landsat.gsfc.nasa.gov/

  14. The Greenland ice sheet in a 6 deg World

    NASA Astrophysics Data System (ADS)

    Dahl-Jensen, Dorthe

    2014-05-01

    There is much doubt and uncertainly on the big ice sheets contribution to sea level rise in a warming world. As it continues to warm the ice sheets will become the biggest contributors to sea level rise as other sources have limited capacity: the total volume of the glaciers and ice caps equivalent to 0.5 m sea level rise, thermal expansion and land water will not change sea level more than 1 m. In the past there have been warm climatic periods where the ice sheets have been reduced. During the last interglacial (LIG or the Eemian) 130-115 thousand years ago the mean global sea level has been estimate to be 6-9 m above the present. Ice cores from the Greenland ice sheet inform that the Greenland ice sheet contributed no more than 2 m to the Eemain sea level so 75% of the ice sheet remained even though the Greenland temperatures up to 8±3 deg C warmer than at present, with an Eemian average of 5±3 deg C. Studies of the ancient dna in the last ice cores before bedrock, 3000m below the present surface of the Greenland ice sheet inform that the temperatures here were 10-15 deg C warmer than the present when the vegetation was present and the Greenland ice sheet melted away. The threshold for the existence of the Greenland ice sheet, determined from the palaeodata is an Arctic warming between 5 and 12 deg C. An Arctic warming of 12 deg C corresponds to a global warming of 6 deg C so in this case the Greenland ice sheet was gone with a 7.5 m contribution to the even larger sea level rise at this time. Our findings suggest this happened 1-3 million years ago at a time where the temperatures where much warmer than the present.

  15. The GreenLand Ice Sheet monitoring Network (GLISN)

    NASA Astrophysics Data System (ADS)

    Larsen, Tine B.; Anderson, K. R.; Beaudoin, B. C.; Butler, R.; Clinton, J. F.; Dahl-Jensen, T.; Ekstrom, G.; Giardini, D.; Hanka, W.; Kanao, M.; McCormack, D.; Mykkelveit, S.; Nettles, M.; Piana Agostinetti, N.; Tsuboi, S.; Voss, P.

    2010-05-01

    The GreenLand Ice Sheet monitoring Network (GLISN) is a new, international, broadband seismic capability for Greenland, being installed and implemented through the joint collaboration of USA, Denmark, Switzerland, Germany, Canada, Italy, Japan and Norway. GLISN is a real-time sensor array consisting of more than 20 broad band stations. The purpose of the project is to enhance and upgrade the performance of the scarce existing Greenland seismic infrastructure for detecting, locating, and characterizing both tectonic and in particular glacial earthquakes and other cryo-seismic phenomena. Complementing data from satellites, geodesy, and other sources, and in concert with these technologies, GLISN will provide a powerful tool for detecting change, and will advance new frontiers of research in the glacial systems as well as in the underlying geological and geophysical processes affecting the Greenland Ice Sheet. The glacial processes that induce seismic events are all integral to the overall dynamics of glaciers, and seismic observations of glaciers therefore provide a quantitative means for monitoring changes in their behaviour over time. Long-term seismic monitoring of the Greenland Ice Sheet will contribute to identifying possible unsuspected mechanisms, and also detect if the areas of cryo-seismic events change and expand in the coming decades. GLISN will provide a new reference network in and around Greenland for monitoring these phenomena in real-time, and for the broad seismological study of Earth and earthquakes. The GLISN development takes its starting point in the existing permanent and long-time stations in and around Greenland operated by members of GLISN. These stations will be upgraded to a common standard with real-time telemetry. The network will be expanded by installing new, telemetered, broadband seismic stations on Greenland's perimeter and ice sheet. An open virtual network is established were all GLISN data can be downloaded. In collaboration with

  16. Greenland Ice Flow

    NASA Image and Video Library

    Greenland looks like a big pile of snow seen from space using a regular camera. But satellite radar interferometry helps us detect the motion of ice beneath the snow. Ice starts flowing from the fl...

  17. SeaWinds - Greenland

    NASA Image and Video Library

    2000-05-08

    The frequent coverage provided by NASA SeaWinds instrument on the QuikScat satellite in 1999 provided unprecedented capability to monitor daily and seasonal changes in the key melt zones of Greenland.

  18. Byrd Glacier, Antarctica

    NASA Image and Video Library

    2008-11-17

    Byrd Glacier is a major glacier in Antarctica; it drains an extensive area of the polar plateau and flows eastward between the Britannia Range and the Churchill Mountains to discharge into the Ross Ice Shelf. This image is from NASA Terra satellite.

  19. A new Glacier Inventory of the Antarctic Peninsula as compiled from pre-existing Datasets

    NASA Astrophysics Data System (ADS)

    Huber, J.; Cook, A. J.; Paul, F.; Zemp, M.

    2016-12-01

    The glaciers on the Antarctic Peninsula (AP) potentially make a large contribution to sea level rise. However, this contribution was difficult to estimate, as no complete glacier inventory (outlines, attributes, separation from the ice sheet) was available so far. This work fills the gap and presents a new glacier inventory of the AP north of 70° S based on digitally combining pre-existing datasets with GIS techniques. Rock outcrops are removed from the glacier basin outlines of Cook et al. (2014) by digital intersection with the latest layer of the Antarctic Digital Database (Burton-Johnson et al. 2016). Glacier-specific topographic parameters (e.g. mean elevation, slope and aspect) as well as hypsometry have been calculated from the DEM of Cook et al. (2012). We also assigned connectivity levels to all glaciers following the concept by Rastner et al. (2012). Moreover, the bedrock dataset of Huss and Farinotti (2014) enabled us to add ice thickness and volume for each glacier. The new inventory is available from the GLIMS database and consists of 1589 glaciers covering an area of 95273 km2, slightly more than the 90000 km2 covered by glaciers surrounding the Greenland Ice Sheet. The total ice volume is 34590 km3 of which 1/3 is below sea level. The hypsometric curve has a bimodal shape due to the special topography of the AP consisting mainly of ice caps with outlet glaciers. Most of the glacierized area is located at 200-500 m a.s.l. with a secondary maximum at 1500-1900 m. About 63% of the area is drained by marine-terminating glaciers and ice shelf tributary glaciers cover 35% of the area. This combination results in a high sensitivity of the glaciers to climate change for several reasons: (1) only slightly rising equilibrium line altitudes would expose huge additional areas to ablation, (2) rising ocean temperatures increase melting of marine terminating glaciers, and (3) ice shelves have a buttressing effect on their feeding glaciers and their collapse would

  20. 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.

  1. HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF DOME AT CENTER REAR. SAME VIEW AT CA-157-2. LOOKING NNE. GIS: N-37' 43 44.3 / W-119 34 14.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

  2. 2. HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF DOME AT CENTER REAR. LOOKING NNE. GIS N-37 43 44.3 / W-119 34 14.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

  3. Low sea level rise projections from mountain glaciers and icecaps under global warming.

    PubMed

    Raper, Sarah C B; Braithwaite, Roger J

    2006-01-19

    The mean sea level has been projected to rise in the 21st century as a result of global warming. Such projections of sea level change depend on estimated future greenhouse emissions and on differing models, but model-average results from a mid-range scenario (A1B) suggests a 0.387-m rise by 2100 (refs 1, 2). The largest contributions to sea level rise are estimated to come from thermal expansion (0.288 m) and the melting of mountain glaciers and icecaps (0.106 m), with smaller inputs from Greenland (0.024 m) and Antarctica (- 0.074 m). Here we apply a melt model and a geometric volume model to our lower estimate of ice volume and assess the contribution of glaciers to sea level rise, excluding those in Greenland and Antarctica. We provide the first separate assessment of melt contributions from mountain glaciers and icecaps, as well as an improved treatment of volume shrinkage. We find that icecaps melt more slowly than mountain glaciers, whose area declines rapidly in the 21st century, making glaciers a limiting source for ice melt. Using two climate models, we project sea level rise due to melting of mountain glaciers and icecaps to be 0.046 and 0.051 m by 2100, about half that of previous projections.

  4. 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.

  5. Ice Island calves off Petermann Glacier

    NASA Image and Video Library

    2017-09-27

    NASA image acquired August 5, 2010 On August 5, 2010, an enormous chunk of ice, roughly 97 square miles (251 square kilometers) in size, broke off the Petermann Glacier, along the northwestern coast of Greenland. The Canadian Ice Service detected the remote event within hours in near real-time data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite. The Peterman Glacier lost about one-quarter of its 70-kilometer (40-mile) long floating ice shelf, said researchers who analyzed the satellite data at the University of Delaware. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured these natural-color images of Petermann Glacier 18:05 UTC on August 5, 2010 (top), and 17:15 UTC on July 28, 2010 (bottom). The Terra image of the Petermann Glacier on August 5 was acquired almost 10 hours after the Aqua observation that first recorded the event. By the time Terra took this image, skies were less cloudy than they had been earlier in the day, and the oblong iceberg had broken free of the glacier and moved a short distance down the fjord. Icebergs calving off the Petermann Glacier are not unusual. Petermann Glacier’s floating ice tongue is the Northern Hemisphere’s largest, and it has occasionally calved large icebergs. The recently calved iceberg is the largest to form in the Arctic since 1962, said the University of Delaware. To read more and or to download the high res go here: www.nasa.gov/topics/earth/features/petermann-calve.html or Click here to see more images from NASA Goddard’s Earth Observatory NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using data obtained from the Goddard Level 1 and Atmospheric Archive and Distribution System (LAADS). Caption by Holli Riebeek and Michon Scott. Instrument: Terra - MODIS NASA Goddard Space Flight Center is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft

  6. The Dynamics of Greenland's Glacial Fjords and Their Role in Climate.

    PubMed

    Straneo, Fiamma; Cenedese, Claudia

    2015-01-01

    Rapid mass loss from the Greenland Ice Sheet has sparked interest in its glacial fjords for two main reasons: Increased submarine melting of glaciers terminating in fjords is a plausible trigger for glacier retreat, and the anomalous freshwater discharged from Greenland is transformed by fjord processes before being released into the large-scale ocean. Knowledge of the fjords' dynamics is thus key to understanding ice sheet variability and its impact on climate. Although Greenland's fjords share some commonalities with other fjords, their deep sills and deeply grounded glaciers, the presence of Atlantic and Polar Waters on the continental shelves outside the fjords' mouths, and the seasonal discharge at depth of large amounts of surface melt make them unique systems that do not fit existing paradigms. Major gaps in understanding include the interaction of the buoyancy-driven circulation (forced by the glacier) and shelf-driven circulation, and the dynamics in the near-ice zone. These must be addressed before appropriate forcing conditions can be supplied to ice sheet and ocean/climate models.

  7. Regionally differentiated contribution of mountain glaciers and ice caps to future sea-level rise

    NASA Astrophysics Data System (ADS)

    Radić, Valentina; Hock, Regine

    2011-02-01

    The contribution to sea-level rise from mountain glaciers and ice caps has grown over the past decades. They are expected to remain an important component of eustatic sea-level rise for at least another century, despite indications of accelerated wastage of the ice sheets. However, it is difficult to project the future contribution of these small-scale glaciers to sea-level rise on a global scale. Here, we project their volume changes due to melt in response to transient, spatially differentiated twenty-first century projections of temperature and precipitation from ten global climate models. We conduct the simulations directly on the more than 120,000 glaciers now available in the World Glacier Inventory, and upscale the changes to 19 regions that contain all mountain glaciers and ice caps in the world (excluding the Greenland and Antarctic ice sheets). According to our multi-model mean, sea-level rise from glacier wastage by 2100 will amount to 0.124+/-0.037m, with the largest contribution from glaciers in Arctic Canada, Alaska and Antarctica. Total glacier volume will be reduced by 21+/-6%, but some regions are projected to lose up to 75% of their present ice volume. Ice losses on such a scale may have substantial impacts on regional hydrology and water availability.

  8. Experimental evidence that microbial activity lowers the albedo of glacier surfaces: the cryoconite casserole experiment.

    NASA Astrophysics Data System (ADS)

    Musilova, M.; Tranter, M.; Takeuchi, N.; Anesio, A. M.

    2014-12-01

    Darkened glacier and ice sheet surfaces have lower albedos, absorb more solar radiation and consequently melt more rapidly. The increase in glacier surface darkening is an important positive feedback to warming global temperatures, leading to ever growing world-wide ice mass loss. Most studies focus primarily on glacial albedo darkening caused by the physical properties of snow and ice surfaces, and the deposition of dark impurities on glaciers. To date, however, the important effects of biological activity have not been included in most albedo reduction models. This study provides the first experimental evidence that microbial activity can significantly decrease the albedo of glacier surfaces. An original laboratory experiment, the cryoconite casserole, was designed to test the microbial darkening of glacier surface debris (cryoconite) under simulated Greenlandic summer conditions. It was found that minor fertilisation of the cryoconite (at nutrient concentrations typical of glacial ice melt) stimulated extensive microbial activity. Microbes intensified their organic carbon fixation and even mined phosphorous out of the glacier surface sediment. Furthermore, the microbial organic carbon production, accumulation and transformation caused the glacial debris to darken further by 17.3% reflectivity (albedo analogue). These experiments are consistent with the hypothesis that enhanced fertilisation by anthropogenic inputs results in substantial amounts of organic carbon fixation, debris darkening and ultimately to a considerable decrease in the ice albedo of glacier surfaces on global scales. The sizeable amounts of microbially produced glacier surface organic matter and nutrients can thus be a vital source of bioavailable nutrients for subglacial and downstream environments.

  9. Ice speed of a calving glacier modulated by small fluctuations in basal water pressure

    NASA Astrophysics Data System (ADS)

    Sugiyama, Shin; Skvarca, Pedro; Naito, Nozomu; Enomoto, Hiroyuki; Tsutaki, Shun; Tone, Kenta; Marinsek, Sebastián; Aniya, Masamu

    2011-09-01

    Ice flow acceleration has played a crucial role in the rapid retreat of calving glaciers in Alaska, Greenland and Antarctica. Glaciers that calve in water flow much faster than those that terminate on land, as a result of enhanced basal ice motion where basal water pressure is high. However, a scarcity of subglacial observations in calving glaciers limits a mechanistic understanding. Here we present high-frequency measurements of ice speed and basal water pressures from Glaciar Perito Moreno, a fast-flowing calving glacier in Patagonia. We measured water pressure in boreholes drilled at a site where the glacier is 515+/-5m thick, and where more than 60% of the ice is below the level of proglacial lakes. We found that the mean basal water pressure was about 95% of the pressure imposed by the weight of the overlying ice. Moreover, changes in basal water pressure by a few per cent drove nearly 40% of the variations in ice flow speed. The ice speed was strongly correlated to air temperature, suggesting that glacier motion was modulated by water pressure changes as meltwater entered the system. We conclude that basal water pressure in calving glaciers is important for glacier dynamics, and closely connected to climate conditions.

  10. Greenland and Antarctica Ice Sheet Mass Changes and Effects on Global Sea Level

    NASA Astrophysics Data System (ADS)

    Forsberg, Rene; Sørensen, Louise; Simonsen, Sebastian

    2017-01-01

    Thirteen years of GRACE data provide an excellent picture of the current mass changes of Greenland and Antarctica, with mass loss in the GRACE period 2002-2015 amounting to 265 ± 25 GT/year for Greenland (including peripheral ice caps), and 95 ± 50 GT/year for Antarctica, corresponding to 0.72 and 0.26 mm/year average global sea level change. A significant acceleration in mass loss rate is found, especially for Antarctica, while Greenland mass loss, after a corresponding acceleration period, and a record mass loss in the summer of 2012, has seen a slight decrease in short-term mass loss trend. The yearly mass balance estimates, based on point mass inversion methods, have relatively large errors, both due to uncertainties in the glacial isostatic adjustment processes, especially for Antarctica, leakage from unmodelled ocean mass changes, and (for Greenland) difficulties in separating mass signals from the Greenland ice sheet and the adjacent Canadian ice caps. The limited resolution of GRACE affects the uncertainty of total mass loss to a smaller degree; we illustrate the "real" sources of mass changes by including satellite altimetry elevation change results in a joint inversion with GRACE, showing that mass change occurs primarily associated with major outlet glaciers, as well as a narrow coastal band. For Antarctica, the primary changes are associated with the major outlet glaciers in West Antarctica (Pine Island and Thwaites Glacier systems), as well as on the Antarctic Peninsula, where major glacier accelerations have been observed after the 2002 collapse of the Larsen B Ice Shelf.

  11. Observational data from the Programme for Monitoring of the Greenland Ice Sheet (PROMICE)

    NASA Astrophysics Data System (ADS)

    Andersen, S. B.; Ahlstrom, A. P.; Andersen, M. L.; Box, J. E.; Citterio, M.; Fausto, R. S.; van As, D.; Forsberg, R.; Skourup, H.; Sandberg, L.; Kristensen, S. S.; Petersen, D.

    2013-12-01

    Climate change in the Arctic has resulted in accelerated mass loss from the Greenland Ice Sheet. The shortage of observations on the Greenland ice sheet infers large uncertainties in estimates of the ice mass loss and in predicting the contribution to sea level rise. For this reason the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) was established in 2007. The aim of the programme is to quantify the mass loss of the Greenland ice sheet and track changes in the extent of the glaciers, ice caps and ice sheet margin. Within PROMICE data sets from several activities are collected. These include: A network of currently 19 automatic weather stations on the margin of the Greenland ice sheet measuring ice ablation and snow fall as well as meteorological parameters. Airborne surveys, yielding surface elevation and ice depth along the entire margin of the Greenland ice sheet. Mapping of all Greenland ice masses, based on the highest detail aero-photogrammetric maps produced from mid-80's aerial photographs. Real-time data from the PROMICE automatic weather station network is shown in at the PROMICE web site www.promice.org and the data is freely available for download. Data from the airborne surveys and mapping activities will also become freely available. Data from PROMICE also contribute to the website www.polarportal.org which is a new Danish web site for providing updated information on the arctic cryosphere to the public.

  12. Arctic Warming and Sea Ice Diminution Herald Changing Glacier and Cryospheric Hazard Regimes

    NASA Astrophysics Data System (ADS)

    Kargel, Jeffrey; Bush, Andrew; Leonard, Gregory

    2013-04-01

    The recent expansion of summertime melt zones in both Greenland and some Arctic ice caps, and the clearing of perennial sea ice from much of the Arctic, may presage more rapid shifts in mass balances of land ice than glaciologists had generally expected. The summer openings of vast stretches of open water in the Arctic, particularly in straits and the Arctic Ocean shores of the Queen Elizabeth Islands and along some Greenland coastal zones, must have a large impact on summer and early autumn temperatures and precipitation now that the surface boundary condition is no longer limited by the triple-point temperature and water-vapor pressure of H2O. This state change in the Arctic probably is part of the explanation for the expanded melt zones high in the Greenland ice sheet. However, Greenland and the Canadian Arctic are vast regions subject to climatic influences of multiple marine bodies, and the situation with sea ice and climate change remains heterogeneous, and so the local climate feedbacks from sea ice diminution remain patchy. Projected forward just a few decades, it is likely that sea ice will play a significant role in the Queen Elizabeth Islands and around Greenland only in the winter months. The region is in the midst of a dramatic climate change that is affecting the mass balances of the Arctic's ice bodies; some polar-type glaciers must be transforming to polythermal, and polythermal ones to maritime-temperate types. Attendant with these shifts, glacier response times will shorten, the distribution and sizes of glacier lakes will change, unconsolidated debris will be debuttressed, and hazards-related dynamics will shift. Besides changes to outburst flood, debris flow, and rock avalanche occurrences, the tsunami hazard (with ice and debris landslide/avalanche triggers) in glacierized fjords and the surge behaviors of many glaciers is apt to increase or shift locations. For any given location, the past is no longer the key to the present, and the present

  13. Nature and tourism in Greenland

    Treesearch

    Berit C. Kaae

    2002-01-01

    This paper provides a short summary on the development of tourism in Greenland, the cultural context, and the protection of the nature resources on which tourism heavily depends. Existing research projects related to tourism in Greenland and the focus of these projects are briefly summarized. In general, most research in Greenland focuses on natural resources, but...

  14. Effect of microorganism on Greenland ice sheet surface temperature change

    NASA Astrophysics Data System (ADS)

    Shimada, R.; Takeuchi, N.; Aoki, T.

    2012-12-01

    Greenland ice sheet holds approximately 10% of the fresh water on earth. If it melts all, sea level rises about 7.2meter. It is reported that mass of Greenland ice sheet is decreasing with temperature rising of climate change. Melting of the coastal area is particularly noticeable. It is established that 4 to 23% of the sea level rising from 1993 to 2005 is caused by the melting of Greenland ice sheet. In 2010, amount of melting per year became the largest than the past. However many climate models aren't able to simulate the recent melting of snow and ice in the Arctic including Greenland. One of the possible causes is albedo reduction of snow and ice surface by light absorbing snow impurities such as black carbon and dust and by glacial microorganisms. But there are few researches for effect of glacial microorganism in wide area. So it is important to clarify the impact of glacial microorganisms in wide area. The purpose of this study is to clarify the effect of microorganism on Greenland ice sheet surface temperature change using satellite images of visible, near infrared and thermal infrared wavelength range and observation carried out in northwestern Greenland. We use MODIS Land Surface Temperature Product as ice sheet surface temperature. It estimates land surface temperature based on split window method using thermal infrared bands. MODIS data is bound to cover the whole of Greenland, and calculated the ratio of the temperature change per year. Analysis period is from December 2002 to November 2010. Results of calculating Greenland ice sheet surface temperature change using the MODIS data, our analysis shows that it is upward trend in the whole region. We find a striking upward trend in northern and western part of Greenland. The rate is 0.33±0.03 degree Celsius per a year from 47.5°W to 49°W. While in the coastal area from 49°W to 50.7°W, the rate is 0.26±0.06 degree Celsius per a year. This large upward trend area is the same area as dark region

  15. Susitna Glacier, Alaska

    NASA Image and Video Library

    2017-09-28

    NASA image acquired August 27, 2009 Like rivers of liquid water, glaciers flow downhill, with tributaries joining to form larger rivers. But where water rushes, ice crawls. As a result, glaciers gather dust and dirt, and bear long-lasting evidence of past movements. Alaska’s Susitna Glacier revealed some of its long, grinding journey when the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite passed overhead on August 27, 2009. This satellite image combines infrared, red, and green wavelengths to form a false-color image. Vegetation is red and the glacier’s surface is marbled with dirt-free blue ice and dirt-coated brown ice. Infusions of relatively clean ice push in from tributaries in the north. The glacier surface appears especially complex near the center of the image, where a tributary has pushed the ice in the main glacier slightly southward. A photograph taken by researchers from the U.S. Geological Survey (archived by the National Snow and Ice Data Center) shows an equally complicated Susitna Glacier in 1970, with dirt-free and dirt-encrusted surfaces forming stripes, curves, and U-turns. Susitna flows over a seismically active area. In fact, a 7.9-magnitude quake struck the region in November 2002, along a previously unknown fault. Geologists surmised that earthquakes had created the steep cliffs and slopes in the glacier surface, but in fact most of the jumble is the result of surges in tributary glaciers. Glacier surges—typically short-lived events where a glacier moves many times its normal rate—can occur when melt water accumulates at the base and lubricates the flow. This water may be supplied by meltwater lakes that accumulate on top of the glacier; some are visible in the lower left corner of this image. The underlying bedrock can also contribute to glacier surges, with soft, easily deformed rock leading to more frequent surges. NASA Earth Observatory image created by Jesse Allen and Robert

  16. Amplified melt and flow of the Greenland ice sheet driven by late-summer cyclonic rainfall

    NASA Astrophysics Data System (ADS)

    Doyle, Samuel H.; Hubbard, Alun; van de Wal, Roderik S. W.; Box, Jason E.; van As, Dirk; Scharrer, Kilian; Meierbachtol, Toby W.; Smeets, Paul C. J. P.; Harper, Joel T.; Johansson, Emma; Mottram, Ruth H.; Mikkelsen, Andreas B.; Wilhelms, Frank; Patton, Henry; Christoffersen, Poul; Hubbard, Bryn

    2015-08-01

    Intense rainfall events significantly affect Alpine and Alaskan glaciers through enhanced melting, ice-flow acceleration and subglacial sediment erosion, yet their impact on the Greenland ice sheet has not been assessed. Here we present measurements of ice velocity, subglacial water pressure and meteorological variables from the western margin of the Greenland ice sheet during a week of warm, wet cyclonic weather in late August and early September 2011. We find that extreme surface runoff from melt and rainfall led to a widespread acceleration in ice flow that extended 140 km into the ice-sheet interior. We suggest that the late-season timing was critical in promoting rapid runoff across an extensive bare ice surface that overwhelmed a subglacial hydrological system in transition to a less-efficient winter mode. Reanalysis data reveal that similar cyclonic weather conditions prevailed across southern and western Greenland during this time, and we observe a corresponding ice-flow response at all land- and marine-terminating glaciers in these regions for which data are available. Given that the advection of warm, moist air masses and rainfall over Greenland is expected to become more frequent in the coming decades, our findings portend a previously unforeseen vulnerability of the Greenland ice sheet to climate change.

  17. Understanding and Modelling Rapid Dynamic Changes of Tidewater Outlet Glaciers: Issues and Implications

    NASA Astrophysics Data System (ADS)

    Vieli, Andreas; Nick, Faezeh M.

    2011-09-01

    Recent dramatic acceleration, thinning and retreat of tidewater outlet glaciers in Greenland raises concern regarding their contribution to future sea-level rise. These dynamic changes seem to be parallel to oceanic and climatic warming but the linking mechanisms and forcings are poorly understood and, furthermore, large-scale ice sheet models are currently unable to realistically simulate such changes which provides a major limitation in our ability to predict dynamic mass losses. In this paper we apply a specifically designed numerical flowband model to Jakobshavn Isbrae (JIB), a major marine outlet glacier of the Greenland ice sheet, and we explore and discuss the basic concepts and emerging issues in our understanding and modelling ability of the dynamics of tidewater outlet glaciers. The modelling demonstrates that enhanced ocean melt is able to trigger the observed dynamic changes of JIB but it heavily relies on the feedback between calving and terminus retreat and therefore the loss of buttressing. Through the same feedback, other forcings such as reduced winter sea-ice duration can produce similar rapid retreat. This highlights the need for a robust representation of the calving process and for improvements in the understanding and implementation of forcings at the marine boundary in predictive ice sheet models. Furthermore, the modelling uncovers high sensitivity and rapid adjustment of marine outlet glaciers to perturbations at their marine boundary implying that care should be taken in interpreting or extrapolating such rapid dynamic changes as recently observed in Greenland.

  18. Airborne Resurveys of the Southern Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Krabill, William B.; Frederick, Earl; Manizade, Serdar; Martin, Chreston; Sonntag, John; Swift, Robert; Thomas, Robert; Wright, Wayne; Yungel, Jim

    1999-01-01

    Airborne laser-altimeter flight lines from 1993 over southern parts of the ice sheet were resurveyed with almost complete repeat coverage. In 1993 and 1994, NASA surveyed the entire Greenland ice sheet by airborne laser altimeter, obtaining surface-elevation profiles with root mean square (rms) accuracies of 10 cm or better (Krabill 1995) along flight lines that crossed all the major catchment basins. In 1998, the ten flight lines flown in 1993 in the south of Greenland were resurveyed with about 99% repeat coverage; flight lines in the north will be resurveyed in 1999. Additional flights in 1998 were over glaciers, identified by E. Rignot, where existing SAR data give information on ice motion.

  19. Potential Climatic Effects on the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Bindschadler, R. A.

    1984-01-01

    The Greenland Ice Sheet covers an area of 1,720,000 sq. km and contains approximately 2,600,000 cu km of ice. Most of the ice sheet receives an excess of snow accumulation over the amount of ice lost to wind, meltwater run-off or other ablative processes. The majority of mass loss occurs at the margin of the ice sheet as either surface melt, which flows into the sea or calving of icebergs from the tongues of outlet glaciers. Many estimates of these processes were published. An average of five published estimates is summarized. If these estimates are correct, then the Greenland Ice Sheet is in approximate equilibrium and contributes 490 cu km/a of fresh water to the North Atlantic and Arctic Oceans. Climate effects, ice sheet flow, and application of remote sensing to tracking of the ice sheet are discussed.

  20. Airborne Resurveys of the Southern Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Krabill, William B.; Frederick, Earl; Manizade, Serdar; Martin, Chreston; Sonntag, John; Swift, Robert; Thomas, Robert; Wright, Wayne; Yungel, Jim

    1999-01-01

    Airborne laser-altimeter flight lines from 1993 over southern parts of the ice sheet were resurveyed with almost complete repeat coverage. In 1993 and 1994, NASA surveyed the entire Greenland ice sheet by airborne laser altimeter, obtaining surface-elevation profiles with root mean square (rms) accuracies of 10 cm or better (Krabill 1995) along flight lines that crossed all the major catchment basins. In 1998, the ten flight lines flown in 1993 in the south of Greenland were resurveyed with about 99% repeat coverage; flight lines in the north will be resurveyed in 1999. Additional flights in 1998 were over glaciers, identified by E. Rignot, where existing SAR data give information on ice motion.

  1. Potential Climatic Effects on the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Bindschadler, R. A.

    1984-01-01

    The Greenland Ice Sheet covers an area of 1,720,000 sq. km and contains approximately 2,600,000 cu km of ice. Most of the ice sheet receives an excess of snow accumulation over the amount of ice lost to wind, meltwater run-off or other ablative processes. The majority of mass loss occurs at the margin of the ice sheet as either surface melt, which flows into the sea or calving of icebergs from the tongues of outlet glaciers. Many estimates of these processes were published. An average of five published estimates is summarized. If these estimates are correct, then the Greenland Ice Sheet is in approximate equilibrium and contributes 490 cu km/a of fresh water to the North Atlantic and Arctic Oceans. Climate effects, ice sheet flow, and application of remote sensing to tracking of the ice sheet are discussed.

  2. Patagonia Glacier, Chile

    NASA Image and Video Library

    2001-07-21

    This ASTER image was acquired on May 2, 2000 over the North Patagonia Ice Sheet, Chile near latitude 47 degrees south, longitude 73 degrees west. The image covers 36 x 30 km. The false color composite displays vegetation in red. The image dramatically shows a single large glacier, covered with crevasses. A semi-circular terminal moraine indicates that the glacier was once more extensive than at present. ASTER data are being acquired over hundreds of glaciers worldwide to measure their changes over time. Since glaciers are sensitive indicators of warming or cooling, this program can provide global data set critical to understand climate change. This image is located at 46.5 degrees south latitude and 73.9 degrees west longitude. http://photojournal.jpl.nasa.gov/catalog/PIA02670

  3. Ablation of Martian glaciers

    NASA Technical Reports Server (NTRS)

    Moore, Henry J.; Davis, Philip A.

    1987-01-01

    Glacier like landforms are observed in the fretted terrain of Mars in the latitude belts near + or - 42 deg. It was suggested that sublimation or accumulation-ablation rates could be estimated for these glaciers if their shapes were known. To this end, photoclinometric profiles were obtained of a number of these landforms. On the basis of analyses of these profiles, it was concluded that ice is chiefly ablating from these landforms that either are inactive rock-glaciers or have materials within them that are moving exceedingly slowly at this time. These conclusions are consistent with other geologic information. The analyses were performed using a two-dimensional model of an isothermal glacier.

  4. GLACIER Express Rack Setup

    NASA Image and Video Library

    2010-09-01

    ISS024-E-012995 (1 Sept. 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, works with the General Laboratory Active Cryogenic ISS Experiment Refrigerator (GLACIER) in the Destiny laboratory of the International Space Station.

  5. Ice stream retreat following the LGM and onset of the west Greenland current in Uummannaq Trough, west Greenland

    NASA Astrophysics Data System (ADS)

    Sheldon, Christina; Jennings, Anne; Andrews, John T.; Ó Cofaigh, Colm; Hogan, Kelly; Dowdeswell, Julian A.; Seidenkrantz, Marit-Solveig

    2016-09-01

    The deglacial history and oceanography of Uummannaq Trough, central West Greenland continental shelf, was investigated using foraminiferal, sedimentological, and bathymetric records together with a radiocarbon chronology, providing a timeline for the retreat of glacial ice after the Last Glacial Maximum (LGM). To map ice stream retreat, data were collected from cores from the outer (JR175-VC45 and JR175-VC43) and inner (JR175-VC42) Uummannaq Trough. A large ice stream, fed by confluent glaciers draining the interior of the Greenland Ice Sheet, extended across the outer shelf during the LGM and was in retreat by 15.0 cal kyr BP. Foraminiferal data indicate that the 'warm' West Greenland Current (WGC) was established prior to 14.0 cal kyr BP, which is the hitherto earliest record of Atlantic Water found on the West Greenland shelf. For each of the cores, foraminifera indicate that ice sheet retreat was followed quickly by incursion of the WGC, suggesting that the warm water may have enhanced ice retreat. Prior to the Younger Dryas cold event, the radiocarbon chronology indicates that the ice sheet retreated to the mid-shelf, where it subsequently stabilised and formed a large grounding-zone wedge (GZW). After the Younger Dryas, around 11.5 cal kyr BP, the ice retreated rapidly from the GZW and into the fjords.

  6. 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.

  7. Flow Characteristics and Basal Boundary Condition for Daugaard-Jensen Gletscher, East Greenland

    NASA Astrophysics Data System (ADS)

    Perry, Thomas; Christoffersen, Poul; Dowdeswell, Julian; Palmer, Steven; Young, Duncan

    2014-05-01

    The recent acceleration of mass loss from the Greenland Ice Sheet can in part be attributed to the dynamic thinning and acceleration of its tidewater outlet glaciers. Many of these glaciers have been shown to exhibit sensitivity to conditions at their marine termini, where warm ocean currents promote ice front melting and retreat. However, these currents are confined to a northerly extent of 69N, and whilst remarkable change is seen to the south of this latitude, glaciers to the north are considerably more stable in terms of terminus position. Different environmental variables may thus control the flow characteristics of glaciers north of this well-defined geographical boundary. During 2011, high-resolution ice data was collected for Daugaard-Jensen Gletscher (71N) as part of the Greenland Outlet Glacier Geophysics (GrOGG) project. Remote sensing has confirmed its stability but few, if any, have applied an ice flow model to examine its ice dynamics in more detail. Here, the numerical Elmer-ICE model is applied to a new bed DEM in order to analyse flow characteristics and basal boundary conditions for Daugaard-Jensen Gletscher. The bed elevation of the inland part of the catchment was derived from Operation Icebridge and GrOGG ice thickness data, whilst the main glacier trunk was inferred through mass conservation calculations at a resolution of 100 m using TerraSAR-X velocity data. The latter was also used for 3D inverse modelling with Elmer-ICE, to analyse basal boundary conditions such as basal traction, sliding speed, frictional heating, and the basal melt rate. This is critical in accurately reproducing velocities and flow characteristics for the glacier, which is not always successful with a simple parameterisation in pure forward modelling. The new DEM offers considerable improvements in vertical accuracy and horizontal resolution compared to previous bed datasets created at the ice-sheet scale. Preliminary results indicate that two deep channels within the

  8. Sea ice studies in the Spitsbergen-Greenland area

    NASA Technical Reports Server (NTRS)

    Vinje, T. E. (Principal Investigator)

    1976-01-01

    The author has identified the following significant results. Detailed information on the outflow through the Fram Strait of ice from the Polar Ocean over shorter periods was obtained. It is found that the speed of the outflow may vary about 100% over periods of a few days. The core of the East Greenland Current is found between 2 deg E and 4 deg W. The speed of the surface water at 81 deg N is for a calm period estimated to be about 10 cm/s. A new surging glacier was discovered and new fronts of several glaciers were determined. The variation of the snow line with respect to distance from the coast was for the first time determined for the southern part of Spitsbergen. Great variations were observed, from 200 m in east to 550 m in the central area of the island.

  9. New Zealand Glaciers

    NASA Image and Video Library

    2017-03-09

    New Zealand contains over 3,000 glaciers, most of which are in the Southern Alps on the South Island. Since 1890, the glaciers have been retreating, with short periods of small advances, as shown in this image from NASA Terra spacecraft. The image cover an area of 39 by 46 km, and are located at 43.7 degrees south, 170 degrees east. http://photojournal.jpl.nasa.gov/catalog/PIA21509

  10. Outlet-glacier flow dynamics estimation combining in-situ and spaceborne SAR measurements

    NASA Astrophysics Data System (ADS)

    Rohner, Christoph; Henke, Daniel; Small, David; Mercenier, Rémy; Lüthi, Martin; Vieli, Andreas

    2016-04-01

    Terminus retreat and flow acceleration changes of ocean-terminating outlet glaciers contribute significantly to the current mass loss of the Greenland Ice Sheet and therefore to global sea level rise. In order to constrain models ice dynamics, detailed knowledge of geometry, ice-flow velocity and strain fields of such calving glaciers is needed. Of specific importance is the near terminus flow dynamics, as the flow fields there are highly influential on the glacier's calving rate. With the current temporal resolution of spaceborne radar systems, it is difficult to accurately capture the near terminus flow fields for fast moving outlet glaciers glaciers, while in-situ measurements using ground based radar interferometers are limited in coverage and constrained by distance and geometric shading of the glacier. We present and analyze the combined continuous velocity fields from a ground based, portable radar system as well as from spaceborne SAR scenes for Eqip Sermia, a medium-sized ocean terminating outlet glacier in western Greenland. The flow fields for the spaceborne data are calculated using feature tracking with a temporal resolution of 12 and 24 days for Sentinel-1 (Interferometric Wide Swath) and RADARSAT-2 (Ultra Fine/Fine Quad) respectively. The in-situ terrestrial radar data were recorded at one minute intervals were additionally processed using interferometry. The combination of in-situ and spaceborne radar enables a spatially continuous assessment of the strain fields of the ocean terminating outlet glacier. An assimilation of the data based on areas with both in-situ and spaceborne measurements is carried out and the results are compared to historical strain field data sets. These data ultimately provide constraints for a physical fracture and damage model.

  11. New approaches to observation and modeling of fast-moving glaciers and ice streams

    NASA Astrophysics Data System (ADS)

    Herzfeld, U. C.; Trantow, T.; Markle, M. J.; Medley, G.; Markus, T.; Neumann, T.

    2016-12-01

    In this paper, we will give an overview of several new approaches to remote-sensing observations and analysis and to modeling of fast glacier flow. The approaches will be applied in case studies of different types of fast-moving glaciers: (1) The Bering-Bagley Glacier System, Alaska (a surge-type glacier system), (2) Jakobshavn Isbræ, Greenland (a tide-water terminating fjord glacier and outlet of the Greenland Inland Ice), and (3) Icelandic Ice Caps (manifestations of the interaction of volcanic and glaciologic processes). On the observational side, we will compare the capabilities of lidar and radar altimeters, including ICESat's Geoscience Laser Altimeter System (GLAS), CryoSat-2's Synthetic Aperture Interferometric Radar Altimeter (SIRAL) and the future ICESat-2 Advanced Topographic Laser Altimeter System (ATLAS), especially regarding retrieval of surface heights over crevassed regions as typical of spatial and temporal acceleration. Properties that can be expected from ICESat-2 ATLAS data will be illustrated based on analyses of data from ICESat-2 simulator instruments: the Slope Imaging Multi-polarization Photon-counting Lidar (SIMPL) and the Multiple Altimeter Beam Experimental Lidar (MABEL). Information from altimeter data will be augmented by an automated surface classification based on image data, which includes satellite imagery such as LANDSAT and WorldView as well as airborne video imagery of ice surfaces. Numerical experiments using Elmer/Ice will be employed to link parameters derived in observations to physical processes during the surge of the Bering Bagley Glacier System. This allows identification of processes that can be explained in an existing framework and processes that may require new concepts for glacier evolution. Topics include zonation of surge progression in a complex glacier system and crevassing as an indication, storage of glacial water, influence of basal topography and the role of friction laws.

  12. greenland_summer_campaign

    NASA Image and Video Library

    2015-08-28

    Laurence Smith, chair of geography at University of California, Los Angeles, deploys an autonomous drift boat equipped with several sensors in a meltwater river on the surface of the Greenland ice sheet on July 19, 2015. “Surface melting in Greenland has increased recently, and we lacked a rigorous estimate of the water volumes being produced and their transport,” said Tom Wagner, the cryosphere program scientist at NASA Headquarters in Washington. “NASA funds fieldwork like Smith’s because it helps us to interpret satellite data, and to extrapolate measurements from the local field sites to the larger ice sheet." Credit: NASA/Goddard/Jefferson Beck

  13. Southern tip of Greenland

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Between the Arctic Ocean to the North and the Atlantic to the South, the island of Greenland remains covered in snow and ice throughout the year except for small portions of the coast line that thaw briefly in the summer. This true-color image from November 2, 2001, shows that even the southern tip of Greenland is back to winter, with even the rugged coastline snow-covered once again. About halfway up the western coastline, a phytoplankton bloom is occurring in the Davis Strait, coloring the water blue-green.

  14. Malaspina Glacier, Alaska

    NASA Image and Video Library

    2002-02-26

    This image from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra satellite covers an area of 55 by 40 kilometers (34 by 25 miles) over the southwest part of the Malaspina Glacier and Icy Bay in Alaska. The composite of infrared and visible bands results in the snow and ice appearing light blue, dense vegetation is yellow-orange and green, and less vegetated, gravelly areas are in orange. According to Dr. Dennis Trabant (U.S. Geological Survey, Fairbanks, Alaska), the Malaspina Glacier is thinning. Its terminal moraine protects it from contact with the open ocean; without the moraine, or if sea level rises sufficiently to reconnect the glacier with the ocean, the glacier would start calving and retreat significantly. ASTER data are being used to help monitor the size and movement of some 15,000 tidal and piedmont glaciers in Alaska. Evidence derived from ASTER and many other satellite and ground-based measurements suggests that only a few dozen Alaskan glaciers are advancing. The overwhelming majority of them are retreating. This ASTER image was acquired on June 8, 2001. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next six years to map and monitor the changing surface of our planet. http://photojournal.jpl.nasa.gov/catalog/PIA03475

  15. Variability in the timing of the late Holocene maximum extent of the southwest Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Carlson, A. E.; Winsor, K.; Ullman, D. J.; Murray, D. S.; Rood, D. H.; Axford, Y.

    2011-12-01

    Boreal summer climate generally cooled across the mid to late Holocene, driving growth of the Greenland Ice Sheet. The timing of maximum late Holocene Greenland Ice Sheet extent is usually assigned to the Little Ice Age (LIA), although earlier more extensive Neoglacial advances may have occurred. Here we present new 10-Be surface exposure ages from erratic boulders on bedrock just outside of historical moraines deposited during the LIA near Kangerlussuaq, Paamiut and Narsarsuaq in southwest Greenland to date when ice was more extensive than during the LIA. A more extensive Neoglacial advance at ~2 ka was previously proposed near Kangerlussuaq. Our cosmogenic dates just outside the historical moraine at Kangerlussuaq indicate, however, that ice has been within its historical limit since 6.8±0.1 ka (n=6, 1 std. error), which is similar to recently published age constraints further north in the Disko Bugt region of west Greenland. Near Narsarsuaq in south Greenland, cosmogenic boulder dates indicate that at 1.2±0.2 ka (n=4, 1 std. error), the outlet glacier Kiagtût sermiat was ~200 m thicker than its historical limit. The timing of thicker ice near Narsarsuaq is likely concurrent with an ~8 km advance the same outlet glacier relative to the modern ice margin previously inferred from one minimum limiting radiocarbon date of 1.2±0.1 ka (1σ). Cosmogenic dates from near Paamiut in southwest Greenland and additional Narsarsuaq dates are forthcoming. The timing of ice thinning and retreat near Narsarsuaq beginning at ~1.2 ka is concurrent with a switch from the dominance of Arctic- to Atlantic-sourced water masses within southern Greenland fjords, inferred from changes in fjord faunal assemblages. Modern switches in the source of fjord waters are related to variations in the North Atlantic Oscillation (NAO), with a switch from a positive to a negative phase causing the incursion of relatively warm Irminger Current waters around southern Greenland. We hypothesize that

  16. Towards quantifying the glacial runoff signal in the freshwater input to Tyrolerfjord-Young Sound, NE Greenland.

    PubMed

    Citterio, Michele; Sejr, Mikael K; Langen, Peter L; Mottram, Ruth H; Abermann, Jakob; Hillerup Larsen, Signe; Skov, Kirstine; Lund, Magnus

    2017-02-01

    Terrestrial freshwater runoff strongly influences physical and biogeochemical processes at the fjord scale and can have global impacts when considered at the Greenland scale. We investigate the performance of the HIRHAM5 regional climate model over the catchments delivering freshwater to Tyrolerfjord and Young Sound by comparing to the unique Greenland Ecological Monitoring database of in situ observations from this region. Based on these findings, we estimate and discuss the fraction of runoff originating from glacierized and non-glacierized land delivered at the daily scale between 1996 and 2008. We find that glaciers contributed on average 50-80% of annual terrestrial runoff when considering different sections of Tyrolerfjord-Young Sound, but snowpack depletion on land and consequently runoff happens about one month earlier in the model than observed in the field. The temporal shift in the model is a likely explanation why summer surface salinity in the inner fjord did not correlate to modelled runoff.

  17. Angalasut, an education and outreach project to create a bridge between scientists, local population in Greenland and the general public

    NASA Astrophysics Data System (ADS)

    Bourgain, Pascaline

    2015-04-01

    Bridging Science and Society has now become a necessity for scientists to develop new partnerships with local communities and to raise the public interest for scientific activities. The French-Greenlandic educational project called "Angalasut" reflects this desire to create a bridge between science, local people and the general public. This program was set up on the 2012-2013 school year, as part of an international scientific program dedicated to study the interactions between the ocean and glaciers on the western coast of Greenland, in the Uummannaq fjord. Greenlandic and French school children were involved in educational activities, in classrooms and out on the field, associated with the scientific observations conducted in Greenland (glacier flow, ocean chemical composition and circulation, instrumentation...). In Greenland, the children had the opportunity to come on board the scientific sailing boat, and in France, several meetings were organized between the children and the scientists of the expedition. In the small village of Ikerasak, the children interviewed Elders about sea ice evolution in the area. These activities, coupled to the organization of public conferences and to the creation of a trilingual website of the project (French, Greenlandic, English) aimed at explaining why scientists come to study