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Search Results Cite abstracts as Author(s) (2008), Title, Eos Trans. AGU,
89(53), Fall Meet. Suppl., Abstract xxxxx-xx
You've chosen 25 documents:
AN: C31B-0499
TI: Does Warming of the North Atlantic over the Last Decade Explain the Acceleration of Outlet Glaciers in Southeast Greenland?
AU: * Straneo, F
EM: fstraneo@whoi.edu
AF: Woods Hole Oceanographic Institution, MS 21, Woods Hole, MA 02543,
AU: Sutherland, D A
EM: dsutherland@whoi.edu
AF: Woods Hole Oceanographic Institution, MS 21, Woods Hole, MA 02543,
AU: Hamilton, G S
EM: gordon.hamilton@maine.edu
AF: Climate Change Institute, University of Maine, 4 Sawyer Lab Annex, Orono, ME 04469,
AU: Stearns, L A
EM: leigh.stearns@maine.edu
AF: Climate Change Institute, University of Maine, 4 Sawyer Lab Annex, Orono, ME 04469,
AB: The Greenland Ice Sheet's contribution to sea level rise more than doubled in the last five years, mostly because of increased mass flux rates from outlet glaciers in southeast Greenland. These outlet glaciers terminate at tidewater in deep fjords, which provides an intimate connection between the ice sheet and the ocean and raises the possibility that ocean warming was the trigger for recent changes in ice dynamics. Until recently, however, the oceanic role was unknown since there was no evidence that the warm waters of tropical origin, found offshore along the continental margins of southeastern and western Greenland, could cross the cold, fresh Arctic waters found on the shelf, and penetrate deep into fjords. We provide evidence that warm offshore waters both penetrate and circulate deep inside Sermilik Fjord, the 100 km long fjord in East Greenland where Helheim Glacier terminates, based on a series oceanographic surveys conducted in the summer of 2008. Furthermore, the depth at which these waters are found, as well as the observed spatial and temporal variability all indicate that the warm waters play an active role in the fjord-glacier estuarine system and suggest that they come into contact with the glacier's terminus. Then, using historical oceanographic and glaciological data we argue that the timing of Helheim Glacier's acceleration is consistent with the variability in warm water properties found offshore. Finally, because Sermilik Fjord and Helheim Glacier are typical of many fjord-glacier systems in southeast Greenland, we propose that glacier-ocean interactions can explain a significant fraction of the increased mass flux from the Greenland Ice Sheet.
DE: 0720 Glaciers
DE: 0726 Ice sheets
DE: 0758 Remote sensing
DE: 4215 Climate and interannual variability (1616, 1635, 3305, 3309, 4513)
DE: 4217 Coastal processes
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C41D-01
TI: Acceleration of Jakobshavn Isbrae Triggered by Warm, Subsurface Irminger Waters
AU: * Holland, D M
EM: holland@cims.nyu.edu
AF: New York University, 251 Mercer St, New York, NY 10012, United States
AU: Thomas, R H
EM: robert_thomas@hotmail.com
AF: EG&G, Wallops, NASA, Building N-159, Wallops Island, VA 23337, United States
AU: deYoung, B
EM: bdeyoung@physics.mun.ca
AF: Memorial University, Chemistry-Physics Building, St John's, NL A1B 3X7, Canada
AU: Ribergaard, M H
EM: mhri@dmi.dk
AF: Danish Meteorological Institute, Lyngbyvej 100, Copenhagen, DK-2100, Denmark
AU: Lyberth, B
EM: bjarne@natur.gl
AF: Greenland Institute of Natural Resources, Postboks 570, Nuuk, 3900, Greenland
AB: Observations over the past decade show a rapid acceleration of several outlet glaciers in Greenland and Antarctica. Among the largest changes seen, Jakobshavn Isbrae(JI), an outlet glacier feeding a deep ocean fjord on the west coast of Greenland, recently, and suddenly, switched its behavior from slow thickening prior to 1997 to subsequent rapid thinning and a doubling in glacier velocity. Suggested reasons for the JI speedup range from increased lubrication of the ice-bedrock interface as more meltwater drains to the bed during recently warmer summers, to weakening and breakup of the floating ice tongue. Here, we present evidence that the changes of the JI were in fact triggered by an increase in subsurface ocean temperature, based on hydrographic data showing a sudden jump during 1997 along the entire west coast of Greenland. This arrival of upstream, Irminger Sea warm water, originating near Iceland, was driven by changes in atmospheric circulation in the North Atlantic.
UR: http://efdl.cims.nyu.edu/project_oisi/realistic/jakobshavn/
DE: 0700 CRYOSPHERE (4540)
DE: 0728 Ice shelves
DE: 4200 OCEANOGRAPHY: GENERAL
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C32B-05
TI: Controls on Greenland Outlet Glacier Sensitivity to Climate Forcing: A Comparative Approach
AU: * McFadden, E M
EM: mcfadden.109@osu.edu
AF: OSU Byrd Polar Research Center, The Ohio State University 1090 Carmack Road, Columbus, OH 43210, United States
AU: Howat, I M
EM: ihowat@gmail.com
AF: OSU Byrd Polar Research Center, The Ohio State University 1090 Carmack Road, Columbus, OH 43210, United States
AU: Ahn, Y
EM: ahnysleo@gmail.com
AF: OSU Byrd Polar Research Center, The Ohio State University 1090 Carmack Road, Columbus, OH 43210, United States
AU: Joughin, I
EM: ian@apl.washington.edu
AF: University of Washington, 1013 NE 40th Street, Seattle, WA 98105, United States
AB: Significant changes in the dynamics of Greenland's marine-terminating outlet glaciers within the past few years indicate a rapid and complex response of these systems to recent climatic forcing. Widespread and substantial accelerations in glacier flow-speed along Greenland's southeast coast have been linked to destabilization and retreat of glacier fronts triggered by thinning to flotation. There is concern that ongoing coastal thinning in northern Greenland will trigger a similar response, further threatening the stability of the ice sheet. Despite regional ice thinning and retreat, the glaciers of Greenland's northwest coast have not yet undergone substantial acceleration. This suggests a lessened dynamic sensitivity of these glaciers to changes at the ice front than southeastern glaciers, likely due to differences in glacier geometry. To investigate the potential factors behind this contrasting behavior, we derive time series" of front position, ice thinning, and flow speed for approximately 70 outlet glaciers along Greenland's southeast and northwest coasts. Using these data, we look for patterns in the relationships between retreat, thinning, acceleration and geometric variables, such as surface slope, to determine the first-order controls on sensitivity to changes at the ice front. Based on these controls, we assess the future stability of these glaciers under continued climate warming.
UR: http://www.bprc.osu.edu/GDG/
DE: 0720 Glaciers
DE: 0726 Ice sheets
DE: 0758 Remote sensing
DE: 0774 Dynamics
DE: 0776 Glaciology (1621, 1827, 1863)
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C44A-08
TI: A Reconstructed 1784-2007 Time Series of Greenland Melt Extent
AU: Knappenberger, P C
EM: chip@nhes.com
AF: New Hope Environmental Services, Inc., 536 Pantops Center, #402, Charlottesville, VA 22911, United States
AU: * Frauenfeld, O W
EM: oliverf@colorado.edu
AF: CIRES National Snow and Ice Data Center, University of Colorado 449 UCB, Boulder, CO 80309-0449, United States
AU: Michaels, P J
EM: pmichaels@cato.org
AF: Cato Institute, 1000 Massachusetts Ave, NW, Washington, DC 20001-5403, United States
AB: Total melt on the Greenland ice sheet has been rising over the past several decades. The melt extent observed in 2007 was the greatest on record according to several satellite-derived indices of Greenland melt. Observed melt extent across the Greenland ice sheet has been shown to be strongly related to summer station temperatures from locations along Greenland's coastal periphery, as well as to variations in the circulation of the atmosphere across the North Atlantic. We exploit these relationships with historical temperature and circulation observations to develop a 224-yr reconstructed history of annual Greenland melt extent from the late 18th century to 2007. This reconstruction allows us to put recent melt, particularly 2007, into a historical perspective and compare current melt to the well-known warm period in the early half of the 20th century. Our reconstruction indicates that the melt observed since the late 1990s is likely among the highest extents to have occurred since the late 18th century, although recent values are not statistically different from those common during the period 1923-1961, a time when summer temperatures along the southern coast of Greenland were similarly high as those experienced in recent years. The reconstruction indicates that if the current trend toward increasing melt extent continues, total melt across the Greenland ice sheet will exceed historic values of the past two and a quarter centuries.
DE: 0726 Ice sheets
DE: 0794 Instruments and techniques
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1621 Cryospheric change (0776)
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C11B-0501
TI: Simulation of Long-Term Response of the Greenland Ice Sheet to Global Warming With an Ice Sheet Model Coupled to a Regional Energy-Moisture Balance Climate Model
AU: * Robinson, A
EM: robinson@pik-potsdam.de
AF: Potsdam Institute for Climate Impact Research, P.O. Box 60 12 03, Potsdam, 14412, Germany
AU: Calov, R
EM: calov@pik-potsdam.de
AF: Potsdam Institute for Climate Impact Research, P.O. Box 60 12 03, Potsdam, 14412, Germany
AU: Ganopolski, A
EM: ganopolski@pik-potsdam.de
AF: Potsdam Institute for Climate Impact Research, P.O. Box 60 12 03, Potsdam, 14412, Germany
AB: Using the 3D, thermo-mechanical ice sheet model SICOPOLIS coupled to a simple, regional energy-moisture balance climate model, we simulated the response of the Greenland ice sheet under various global warming scenarios. Until now, the usual approach to specify surface boundary conditions for ice sheet models has been to use present day temperature and precipitation distributions in combination with anomalies to scale the values to the past or future. This method is only justified, however, when the ice sheet area and elevation remain similar to present day, because it assumes that the patterns of temperature and precipitation remain similar to present ones. However, it is likely that the distributions of temperature and, especially, precipitation would be much different for a partially or completely ice-free Greenland. In our approach, the climatology used to force the ice sheet model explicitly accounts for albedo feedback and elevation changes. This is important for long-term (multi-centennial to multi-millennial) climate change scenarios, in which the Greenland ice sheet could melt completely, since the albedo feedback would produce higher temperatures in the interior of Greenland, altering the temperature pattern from the current distribution, and the precipitation pattern, particularly in Southern Greenland, would be strongly affected by elevation changes. We present results of simulations for several long-term global warming scenarios and compare them with those found using the traditional (anomalous) approach. We also performed a stability analysis of the Greenland Ice sheet in CO2 phase space by performing a set of equilibrium experiments for different CO2 concentrations and initial conditions.
DE: 0726 Ice sheets
DE: 0764 Energy balance
DE: 1621 Cryospheric change (0776)
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C41A-0476
TI: Hydrologic response of the Greenland Ice sheet: the role of oceanographic warming
AU: * Hanna, E
EM: ehanna@sheffield.ac.uk
AF: Department of Geography, University of Sheffield, Winter Street, Sheffield, S10 2TN, United Kingdom
AU: Cappelen, J
AF: Danish Meteorological Institute, Lyngbyvej 100, Copenhagen, DK2100, Denmark
AU: Fettweis, X
AF: Département de Géographie, Université de Liège, allée du 6 Août, 2, Liège, 4000, Belgium
AU: Huybrechts, P
AF: Departement Geografie, Vrije Universiteit Brussel, Pleinlaan 2, Brussel, B-1050, Belgium
AU: Luckman, A
AF: School of the Environment and Society, Swansea University, Singleton Park, Swansea, SA2 8PP, United Kingdom
AU: Ribergaard, M
AF: Danish Meteorological Institute, Lyngbyvej 100, Copenhagen, DK2100, Denmark
AB: The response of the Greenland Ice Sheet to ongoing climate change remains an area of great uncertainty, with most previous studies having concentrated on the contribution of the atmosphere to the ice mass- balance signature. Here we systematically assess for the first time the influence of oceanographic changes on the Ice Sheet. The first part of this assessment involves a statistical analysis and interpretation of the relative changes and variations in sea-surface and air temperatures around Greenland for the period 1870- 2007. This analysis is based on HadISST1 and Reynolds OI.v2 sea-surface temperature analyses, in situ SST and deeper-ocean temperature series, surface-air-temperature records for key points located around the Greenland coast, and examination of atmospheric pressure and geopotential height from NCEP/NCAR reanalysis. Second, we carried out a novel sensitivity experiment in which SSTs were perturbed as input to a regional climate model, and document the resulting effects on simulated Greenland climate and surface mass balance. We conclude that sea-surface/ocean temperature forcing is not sufficient to strongly influence precipitation/snow accumulation and melt/runoff of the ice sheet. Additional evidence from meteorological reanalysis suggests that high Greenland melt anomalies of summer 2007 are likely to have been primarily forced by anomalous advection of warm air masses over the Ice Sheet and to have therefore had a more remote atmospheric origin. We also take a preliminary look at summer 2008 climate and melt anomalies over Greenland and their attribution. However, there is a striking correspondence between ocean warming and dramatic accelerations and retreats of key Greenland outlet glaciers in both Southeast and Southwest Greenland during the late 1990s and early 2000s.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1621 Cryospheric change (0776)
DE: 1630 Impacts of global change (1225)
DE: 1637 Regional climate change
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C31E-0570
TI: MODIS-derived Greenland ice sheet equilibrium line altitude 2000-2008: comparison with surface melt and accumulation variability
AU: Benson, R
EM: russtron@gmail.com
AF: Byrd Polar Research Center, 1090 Carmack Rd, Columbus, OH 43210, United States
AU: * Box, J
EM: jbox.greenland@gmail.com
AF: Byrd Polar Research Center, 1090 Carmack Rd, Columbus, OH 43210, United States
AB: Equilibrium Line Altitude (ELA), where accumulation and ablation balance on an annual basis conveniently integrates the combined effect of surface melting and net snow accumulation. ELA can be monitored in optical satellite imagery for cloud-free scenes just prior to the first winter snow. We use NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) to first manually, then using reflectance thresholds, we automatically classify in many images whole-Greenland ice sheet ELA. Inter-annual ELA variations spanning years 2000-2008 are compared with precipitation and melt anomalies simulated by Polar MM5 to better understand ELA sensitivity to climate and likely future changes in ice sheet accumulation area ratio.
DE: 0700 CRYOSPHERE (4540)
DE: 0758 Remote sensing
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 3309 Climatology (1616, 1620, 3305, 4215, 8408)
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C31E-0563
TI: High-Resolution Bathymetry of Disko Bay and Ilulissat Icefjord, West- Greenland
AU: * Weinrebe, W
EM: wweinrebe@ifm-geomar.de
AF: Cluster of Excellence "The Future Ocean", University of Kiel, Wischhofstr. 1-3, Kiel, 24148, Germany
AU: * Weinrebe, W
EM: wweinrebe@ifm-geomar.de
AF: Leibniz-Institute of Marine Sciences IFM-GEOMAR, Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Kuijpers, A
EM: aku@geus.dk
AF: Geological Survey of Denmark and Greenland - GEUS, O. Voldgade 10, Copenhagen, 1350, Denmark
AU: Klaucke, I
EM: iklaucke@ifm-geomar.de
AF: Leibniz-Institute of Marine Sciences IFM-GEOMAR, Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Fink, M
EM: mfink@ifm-geomar.de
AF: Leibniz-Institute of Marine Sciences IFM-GEOMAR, Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Jensen, J B
EM: jbj@geus.dk
AF: Geological Survey of Denmark and Greenland - GEUS, O. Voldgade 10, Copenhagen, 1350, Denmark
AU: Mikkelsen, N
EM: nm@geus.info
AF: Geological Survey of Denmark and Greenland - GEUS, O. Voldgade 10, Copenhagen, 1350, Denmark
AB: About 10% of the annual production of Greenland calf ice passes Disko Bay in the northern part of West- Greenland. The amount of over 35 km3 of ice annually which is more than any other glacier outside Antarctica produces, floats with a speed of more than 1 m per hour into Disko Bay through Ilulissat Icefjord, a 60 km long and 3-6 km wide tide-water ice-stream. This highly dynamic system with the large calving production and the high velocity implies a rapid response to climate changes and is thus a key area for the understanding of West Greenland Holocene climate history. The seafloor in the icefjord and off its mouth is extensively shaped by the movement of the icebergs and characterized by abundant plow marks. Large icebergs accumulate over a sill off the fjord mouth where they reside several months until they are finally released through the combined effect of tides and streams, melting, and melt-water lubrication. All these processes shape the morphology of the seafloor and create characteristic submarine landforms. Revealing the morphology helps to understand these processes. High-resolution bathymetric maps display the relief and morphology of the seafloor, however multibeam bathymetry surveys are difficult to perform in front of moving icebergs. As recently as 2007 a first high-resolution multibeam survey was carried out with RV Maria S. Merian to map a large area of Disko Bay off the mouth of Ilulissat Icefjord. In summer 2008 the survey was extended into the fjord using a small local vessel equipped with a temporarily installed portable Seabeam 1180 multibeam system. Both datasets merged together well display the morphology of the area mostly affected by the activity of the floating ice and the movements of icebergs.
DE: 0730 Ice streams
DE: 0732 Icebergs
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1824 Geomorphology: general (1625)
DE: 3045 Seafloor morphology, geology, and geophysics
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C31E-0546
TI: Marine geophysical evidence for former expansion and flow of the Greenland Ice Sheet across the northeast Greenland continental shelf
AU: * Evans, J
EM: J.Evans2@lboro.ac.uk
AF: Department of Geography, Loughborough University, Loughborough, LE11 3SJ, United Kingdom
AU: O Cofaigh, C
EM: colm.o'cofaigh@durham.ac.uk
AF: Department of Geography, Durham University, Durham, DH1 3LE, United Kingdom
AU: Dowdeswell, J
EM: jd16@cam.ac.uk
AF: Scott Polar Research Institute, University of Cambridge, Cambridge, CB2 1ER, United Kingdom
AU: Wadhams, P
EM: pw11@damtp.cam.ac.uk
AF: Sea Ice Group, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 0WA, United Kingdom
AB: Fast-flowing glaciers in NE Greenland drain approximately 300,000 km2 or 20% of the Greenland Ice Sheet to the margin. Swath bathymetry and sub-bottom profiler acoustic data from the continental margin of northeast Greenland (78° N to 80° N) provide a record of the long-term behaviour of the Greenland Ice Sheet in this region. Geophysical data record the presence of subglacial landforms on the continental shelf that are formed in the surface of a soft sediment layer. Mega-scale glacial lineations are found in Westwind Trough that connects the outlet glaciers Nioghalvfjerdsfjorden Gletscher and Zachariae Isstrom to the continental shelf edge. The geomorphological and stratigraphical records show that the Greenland Ice Sheet covered the inner-middle shelf during the most recent ice advance of the Late Weichselian glaciation, and that ice flow through Westwind Trough was in the form of a grounded, fast-flowing ice stream. Glacimarine sediment gravity flow deposits on the continental slope imply that the ice sheet extended beyond the middle continental shelf, and supplied subglacial sediment direct to the shelf edge with subsequent remobilisation downslope. Collectively the geophysical data record for the first time that ice streams were an important glacio-dynamic feature that drained interior basins of the Late Weichselian Greenland Ice Sheet across the NE Greenland continental margin, and that the ice sheet was far more extensive in this region during the last glacial maximum than the previous terrestrial-glacial reconstructions showed.
DE: 0720 Glaciers
DE: 0726 Ice sheets
DE: 0730 Ice streams
DE: 1707 Cryosphere
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C12A-08
TI: Terrestrial photogrammetry of Greenland glacier discharge variability: comparison with surface climate anomalies
AU: * Box, J E
EM: jbox.greenland@gmail.com
AF: Byrd Polar Research Center, Scott Hall Rm 108 1090 Carmack Rd, Columbus, OH 43210, United States
AU: Yushin, A
EM: ahnysleo@gmail.com
AF: Byrd Polar Research Center, Scott Hall Rm 108 1090 Carmack Rd, Columbus, OH 43210, United States
AU: Balog, J
EM: jamesbalog@mac.com
AF: Extreme Ice Survey, 262 Bristlecone Way, Boulder, CO 80304, United States
AU: Lewinter, A
EM: adam.lewinter@gmail.com
AF: Extreme Ice Survey, 262 Bristlecone Way, Boulder, CO 80304, United States
AU: Orlowski, J
EM: orlowski@gmail.com
AF: Extreme Ice Survey, 262 Bristlecone Way, Boulder, CO 80304, United States
AB: Repeat photography provides a powerful tool to quantify glacier speed variability without the need to set foot on the hazardous glacier front. Surface displacements are derived from daily digital images from several west Greenland ice sheet outlet glaciers. Displacements are compared with surface melt intensity data to test the hypothesis that a significant inter-daily correlation exists between outlet glacier discharge and melt intensity. Neighboring and regional glacier speed co-variability on inter-daily time scales is evaluated. The effect of winter sea ice and its breakup is evaluated. Numerous time lapse sequences are presented.
UR: http://extremeicesurvey.org/
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 1621 Cryospheric change (0776)
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C31A-0485
TI: Greenland Surface Melt Trends From SSM/I And QuikSCAT Data
AU: * Bhattacharya, I
EM: bhattacharya.21@osu.edu
AF: Byrd Polar Research Center, The Ohio State University, Scott Hall Room 108,1090 Carmack Road, Columbus, OH 43210, United States
AU: Jezek, K C
EM: jezek@frosty.rsl.ohio-state.edu
AF: Byrd Polar Research Center, The Ohio State University, Scott Hall Room 108,1090 Carmack Road, Columbus, OH 43210, United States
AU: Wang, L
EM: leiwang@lsu.edu
AF: Department of Geography and Anthropology, Louisiana State University, 227 Howe- Russell, Geoscience Complex, Baton Rouge, LA 70803, United States
AU: Liu, H
EM: liu@geog.tamu.edu
AF: Department of Geography, Texas A&M University, Room 810, Eller O&M Building, College Station, TX 77843, United States
AB: We estimated surface melt on the Greenland Ice Sheet using Special Sensor Microwave/Imager (SSM/I) data during 1989-2007 and Quick Scatterometer (QuikSCAT) data during 2000-2007. We applied a multi-scale wavelet transform based edge detection technique to the SSM/I data for melt detection. For QuikSCAT data, we used a threshold based method to compute surface melt. The correlation coefficient between the surface melt areas calculated from these two different sensors and two different algorithms reaches 0.98. Our analysis shows that the temporal variation in the surface melt in Greenland can divided into three sub- periods: 1979-1989, 1990-2000, and 2000-2007. Each sub-period has a distinctive change rate in melt extent, which implies a decadal scale variability in surface melt on the Greenland Ice Sheet.
DE: 0740 Snowmelt
DE: 0758 Remote sensing
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C31B-0496
TI: GRACE Observes Small-Scale Mass Loss in Greenland
AU: Wouters, B
EM: bert.wouters@tudelft.nl
AF: TU Delft, Faculty of Aerospace Engineering, Kluyverweg 4, Delft, 2629HS, Netherlands
AU: Chambers, D
EM: chambers@csr.utexas.edu
AF: Center for Space Research, University of Texas at Austin, 3925 West Braker Lane, Suite 200, Austin, TX 78759-5321, United States
AU: * Schrama, E
EM: e.j.o.schrama@tudelft.nl
AF: TU Delft, Faculty of Aerospace Engineering, Kluyverweg 4, Delft, 2629HS, Netherlands
AB: Using gravity data from the GRACE satellites between February 2003 and January 2008, we examine changes in Greenland's mass distribution on a regional scale. During this period, Greenland lost mass at a mean rate of 179±25 Gt/yr, equivalent to a global mean sea level change of 0.5±0.1 mm/yr. Rates increase over time and are driven by mass loss during the summers, which vary substantially over the years. The largest mass losses occurred along the southeastern and northwestern coast in the summers of 2005 and 2007, when the ice sheet lost 279 Gt and 328 Gt of ice respectively within 2 months. In 2007, a substantial mass loss is observed during summer at elevations above 2000 m, for the first time since the start of the GRACE observations.
DE: 0762 Mass balance (1218, 1223)
DE: 1217 Time variable gravity (7223, 7230)
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C31B-0494
TI: Mass-balance measurements from a network of automatic weather stations in the ablation zone of the Greenland Ice Sheet
AU: * van As, D
EM: dva@geus.dk
AF: GEUS, Oster Voldgade 10, Copenhagen, 1350, Denmark
AU: Ahlstrom, A P
EM: apa@geus.dk
AF: GEUS, Oster Voldgade 10, Copenhagen, 1350, Denmark
AB: The most accurate way to record continuous mass balance variations for a specific location is by placing an automatic weather station (AWS). In spite of this, the ablation zone of the Greenland Ice Sheet had a poor spatial coverage of these measurement systems, as changing ice surfaces, strong winds, etc. may call for frequent visits, and therewith high logistical expenses. However, we are in the process of building a comprehensive network of AWSs in the ablation zone (part of the PROMICE programme for monitoring the Greenland Ice Sheet), increasing the number of permanent transects around the ice sheet from two to nine. We will present preliminary mass-balance data of the stations placed during the previous two summers, focusing on the summer of 2008. After completion of the network in 2009, the measurements will serve as input for a melt model run over the entire ice sheet. Another ambition is to use the data to validate regional climate models. We will discuss the uncertainties of such modeling in the ablation zone, and possibly compare model results for 2008 to our observations.
DE: 0740 Snowmelt
DE: 0762 Mass balance (1218, 1223)
DE: 0764 Energy balance
DE: 0772 Distribution
DE: 0794 Instruments and techniques
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C31C-0508
TI: Greenland Ice Sheet Seasonal Speedup Coupled With Surface Hydrology
AU: * Palmer, S J
EM: s.j.palmer@sms.ed.ac.uk
AF: School of GeoSciences, The University of Edinburgh, Drummond Street, Edinburgh, EH8 9XP, United Kingdom
AU: Shepherd, A
EM: Andrew.Shepherd@ed.ac.uk
AF: School of GeoSciences, The University of Edinburgh, Drummond Street, Edinburgh, EH8 9XP, United Kingdom
AU: Nienow, P
EM: Peter.Nienow@ed.ac.uk
AF: School of GeoSciences, The University of Edinburgh, Drummond Street, Edinburgh, EH8 9XP, United Kingdom
AB: We use interferometric synthetic aperture radar data from western Greenland to quantify temporal variations in ice sheet flow and to characterise the ice sheet surface hydrology. In contrast to a recent study, our data reveal a non-uniform pattern of summertime velocity increase that, in places, extends over 100 km inland. Ice speedup is intimately linked to the routing of supraglacial water, and the magnitude of seasonal flow variations is positively correlated with the area of surface hydrological catchments. During late summer, ice beneath the largest catchments flows on average ~50 % faster than in winter, but beneath small catchments there is little or no change. Our results suggest that mass losses from the Greenland Ice Sheet under a warming climate will be governed by the extent to which coupling between hydrology and flow evolves, and that ground-based experiments to study velocity fluctuations should be sited with care.
DE: 0726 Ice sheets
DE: 0746 Lakes (9345)
DE: 0758 Remote sensing
DE: 0774 Dynamics
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C23A-0586
TI: Structural Glaciology and Recent Changes of Helheimgletscher and Fenrisgletscher, East Greenland
AU: * Mayer, H
EM: mayerh@tryfan.colorado.edu
AF: Terra Mobilis Research, P.O. Box, Lafayette, CO 80026, United States
AU: Herzfeld, U C
EM: ute.herzfeld@colorado.edu
AF: CIRES, University of Colorado Boulder, Boulder, CO 80309-0449, United States
AU: Sucht, S
EM: steven.sucht@hotmail.com
AF: CIRES, University of Colorado Boulder, Boulder, CO 80309-0449, United States
AB: Drastic changes have been affecting the Greenland Ice Sheet and its outlet glaciers in recent years. While a general trend to increased melting and accelerated ice discharge is apparent, individual glaciers behave quite differently. We present a structural analysis of Helheimgletscher and Fenrisgletscher based on aerial surveys and remote-sensing data to assess their kinematics and dynamics. Our approach combines principles and techniques from structural geology with continuum mechanics and remote sensing to characterize and classify structural units within glaciers. Time series of structural classification and segmentation of a glacier derived from repeat observations provide a detailed record of its kinematic and dynamic development. Helheimgletscher is the only glacier in the Sermilik area of East Greenland that showed significant and prolonged periods of advance during the twentieth century. Our field observations of 2001 revealed that Helheimgletscher was still advancing then. Neighboring Fenrisgletscher, in contrast, was moving and retreating slowly. Since then, Helheimgletscher has changed into a phase of rapid retreat and acceleration of flow. We analyze the most recent changes based on high-resolution remote-sensing imagery.
DE: 0720 Glaciers
DE: 0726 Ice sheets
DE: 0758 Remote sensing
DE: 0774 Dynamics
DE: 0776 Glaciology (1621, 1827, 1863)
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C21D-04 INVITED
TI: Greenland ice sheet surface air temperature and accumulation rate reconstruction (1840- 2007) from in-situ data records
AU: * Box, J E
EM: jbox.greenland@gmail.com
AF: Byrd Polar Research Center, Scott Hall, Rm 108 1090 Carmack Rd, Columbus, OH 43210, United States
AU: Yang, L
EM: lei.miren.yang@gmail.com
AF: South China Sea Institute of Oceanology, 164 West XinGang Road, Guangzhou, 510301, China
AU: Bromwich, D
EM: bromwich@polarmet1.mps.ohio-state.edu
AF: Byrd Polar Research Center, Scott Hall, Rm 108 1090 Carmack Rd, Columbus, OH 43210, United States
AU: Bai, L
EM: bai@polarmet1.mps.ohio-state.edu
AF: Byrd Polar Research Center, Scott Hall, Rm 108 1090 Carmack Rd, Columbus, OH 43210, United States
AB: Meteorological station and ice core records are combined with regional climate model output to develop a continuous 168-year (1840-2007) spatial reconstruction of seasonal mean Greenland ice sheet near-surface air temperatures and ice sheet snow accumulation rates. Independent observations are used to assess and compensate systematic errors. Uncertainty is quantified using residual non-systematic error. Spatial and temporal temperature variability is investigated on seasonal and annual time scales. We find that volcanic cooling episodes are concentrated in winter and around western Greenland. Warming trends coincide with an absence of major volcanic eruptions. Year 2003 was the only year 1840-2007 with a warm anomaly that exceeds three standard deviations from the 1951-1980 base period. The annual whole ice sheet 1919-1932 warming trend is 33% greater in magnitude than the 1994-2007 warming. The recent warming was, however, stronger along western Greenland in autumn and southern Greenland in winter. Spring trends marked the 1920s warming onset while autumn lead the 1994-2007 warming. In contrast to the 1920s warming, the 1994- 2007 warming has not surpassed the northern hemisphere anomaly. An additional 1.0-1.5°C of annual mean warming would be needed for Greenland to be in phase with the Northern Hemispheric pattern. We thus predict that the ice sheet melt rates and recent mass deficit will continue to grow in the early 21st century as Greenland climate catches up with the Northern Hemispheric warming trend and Arctic climate warms according with climate forecasts. Reconstructed accumulation rates exhibit significant inter-decadal trends. Spatial and temporal surface mass balance is reconstructed from melt intensity derived from the air temperature and accumulation reconstructions. The effect of recent and past century warming on surface mass balance is presented.
DE: 0700 CRYOSPHERE (4540)
DE: 0726 Ice sheets
DE: 3309 Climatology (1616, 1620, 3305, 4215, 8408)
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C43A-01 INVITED
TI: Recent Surface Changes in Southern Greenland Outlet Glaciers from NASA's Airborne Topographic Mapper Experiments
AU: Krabill, W B
EM: william.b.krabill@nasa.gov
AF: NASA/GSFC/Wallops Flight Facility, Building N159, Room E201, Wallops Island, VA 23337, United States
AU: * Sonntag, J G
EM: sonntag@osb.wff.nasa.gov
AF: EG&G Services, Inc., NASA Wallops Flight Facility, Wallops Island, VA 23337, United States
AB: In summer 2008, NASA deployed its Airborne Topographic Mapper (ATM), along with other airborne science instruments, to several locations around the southern periphery of the Greenland ice sheet, with the aim of quantifying recent changes in a number of outlet glaciers. The ATM also joined with a Swansea University (United Kingdom) team in order to provide geodetic reference ties on the bare bedrock surrounding a dozen outlet glaciers, most of them in southeastern Greenland. The goal of this phase of the effort was to make possible the computation of volumetric change of these glaciers using a decades-long series of oblique aerial photographs, combined with the geodetic reference provided by the ATM's rock overflights. Finally, we supported a National Science Foundation and University of Kansas effort to fly a large, dense grid over the greater Jakobshavn basin to obtain bedrock topography using their 150 MHz depth-sounding radar. In the process of this, we obtained our own extensive surface-topography measurements over the same grid. Here we present initial results from these efforts, including changes in the surface topography of the Jakobshavn and Helheim glacier basins, and along the flowlines of Kangerdlugssuaq and other outlet glaciers in the southeast of Greenland. Finally we summarize initial, or baseline, measurements along the flowlines of a number of glaciers never mapped before by the ATM, which we flew as part of our other efforts and which will pay dividends when the ATM returns to refly the lines in future campaigns.
UR: http://atm.wff.nasa.gov/
DE: 0720 Glaciers
DE: 0726 Ice sheets
DE: 0758 Remote sensing
DE: 0776 Glaciology (1621, 1827, 1863)
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C31B-0498
TI: Spatial and Temporal Trends in Snow Accumulation From Radio Echo Eounding, Summit, Greenland
AU: * Overly, T B
EM: toverly@ku.edu
AF: CReSIS - Center for the Remote Sensing of Ice Sheets, University of Kansas 316 Nichols Hall 2335 Irving Hill Road, Lawrence, KS 66045-7612, United States
AB: Current estimates of snow accumulation over Greenland have large errors (20-25%) because they are derived from a relatively sparse network of point measurements (Ohmura and Reeh, 1991; Bales et al., 2001). To determine whether the Greenland ice sheet mass is increasing or decreasing and how this will affect the global sea level, the Center for Remote Sensing of Ice Sheets (CReSIS) at the University of Kansas has developed several ice penetrating radar systems. Ground based ultra-wideband radar (500-2000 MHz) operated near Summit, Greenland, in July 2005, is used to map near-surface internal layers with 10 cm free- space resolution. This high resolution allows for visual inspection of accumulation layers to a depth of over 200 meters. Radar transects connecting the GRIP and GISP2 ice cores reveal continuous reflection horizons that allow for the transfer of age-depth relationships obtained from the ice cores to the continuous radar reflections. Accurately dated and spatially continuous isochrones are valuable for calibration and verification of ice sheet models. The observed isochrones provide a detailed description of spatial and temporal variations in accumulation rate over the past 500 years and constrain the selection of parameters and climate history used to force numerical models.
DE: 0700 CRYOSPHERE (4540)
DE: 0726 Ice sheets
DE: 0933 Remote sensing
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C43A-02
TI: A new high-resolution assessment of Greenland ice sheet surface mass balance: 1957- 2008
AU: * Ettema, J
EM: J.Ettema@uu.nl
AF: Utrecht University, Institute for Marine and Atmospheric Sciences, PO Box 80005, Utrecht, 3508TA, Netherlands
AU: Van den Broeke, M
EM: m.r.vandenbroeke@uu.nl
AF: Utrecht University, Institute for Marine and Atmospheric Sciences, PO Box 80005, Utrecht, 3508TA, Netherlands
AU: Van Meijgaard, E
EM: Erik.van.Meijgaard@knmi.nl
AF: Royal Netherlands Meteorological Institute, PO Box 201, De Bilt, 3730AE, Netherlands
AU: Van de Berg, W
EM: w.j.vandeberg@uu.nl
AF: Utrecht University, Institute for Marine and Atmospheric Sciences, PO Box 80005, Utrecht, 3508TA, Netherlands
AU: Bamber, J
EM: j.bamber@bristol.ac.uk
AF: Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, United Kingdom
AU: Box, J
EM: box.11@osu.edu
AF: Byrd Polar Research Center The Ohio State University, 1090 Carmack Road, Columbus, OH 43210-1002, United States
AB: Large uncertainties remain in the surface mass balance (SMB) of the Greenland ice sheet. To assess the current state and variability of the SMB components we use the Regional Atmospheric Climate Model (RACMO2.1). A model integration for the period 1957-2008 is performed at an unprecedented high horizontal grid resolution of 11 km, which is sufficient to resolve the large melt gradients in the narrow ablation zone and study in detail processes such as percolation, retention and refreezing of melt water. The model results show excellent agreement with observations. Comparison of SMB results with other regional climate models show similar spatial patterns, but locally substantial improvements. Increasing the horizontal resolution enhances the gradients in the SMB and its components. For example, the orographically forced precipitation amount in the south-east of Greenland is much larger than previously concluded. Newly gained surface mass balance observations in this area support this. The integrated ablation and subsequent surface runoff is comparable to other studies, leading to a more positive surface mass balance for the Greenland ice sheet.
DE: 0726 Ice sheets
DE: 0762 Mass balance (1218, 1223)
DE: 0798 Modeling
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C43A-06
TI: Rapid crustal uplift due to unloading of ice from the main outlet glaciers in Greenland
AU: * Khan, S A
EM: abbas@space.dtu.dk
AF: DTU Space - National Space Institute, Juliane Maries Vej 30, Copenhagen, 2100, Denmark
AU: Wahr, J
EM: wahr@anquetil.colorado.edu
AF: Department of Physics and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, United States
AU: Hamilton, G
EM: gordon.hamilton@main.edu
AF: Climate Change Institute, University of Maine, Maine, OR 04469, United States
AU: Stearns, L
EM: leigh.stearns@maine.edu
AF: Climate Change Institute, University of Maine, Maine, OR 04469, United States
AU: Dam, T v
EM: tonie.vandam@uni.lu
AF: Faculté des Sciences, de la Technologie et de la Communication, University of Luxembourg, Luxembourg, L-1511,
AU: Francis, O
EM: olivier.francis@uni.lu
AF: Faculté des Sciences, de la Technologie et de la Communication, University of Luxembourg, Luxembourg, L-1511,
AB: The main outlet glaciers in Greenland have more than doubled their ice volume loss in the past decade. Ice volume loss due to thinning of glaciers would result in a rapid mass unloading of the earth's crust. The elastic adjustments of the lithosphere is detectable using geodetic observations. Here, we use continuous Global Positioning System (GPS) measurements to study vertical crustal motions. We analyze data from ~20 GPS receivers, all located along the edge of the Greenland ice sheet. The rapid unloading of ice from the southeastern sector of the Greenland ice sheet causes an elastic uplift of ~12 mm/yr at a GPS site in Kulusuk (a settlement located ~50 km from the ice sheet margin) and 16 mm/yr at a GPS site in Isortoq (located few km from the ice sheet margin) and 20 mm/yr at HEL2 (a GPS site near the front of the Helheim Glacier). The GPS observations can be explained as due to ice volume loss of ~150 km3 yr-1 due to thinning in the southeastern sector of the Greenland ice sheet (including the Helheim glacier and the Kangerdlugssuaq glacier). Additionally, data from 4 continuous GPS receivers located between 0-150 km from the front of Greenland's Jakobshavn Glacier, suggest an annual net loss of 20-25 km3 of ice from Jakobshavn Glacier.
DE: 0720 Glaciers
DE: 0726 Ice sheets
DE: 0762 Mass balance (1218, 1223)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1244 Standards and absolute measurements
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C53A-08
TI: Local sea-ice influence on Greenland surface melt
AU: * Rennermalm, A K
EM: akr@ucla.edu
AF: University of California Los Angeles, Department of Geography, 1255 Bunche Hall, Box 951525, Los Angeles, CA 90095, United States
AU: Smith, L C
EM: lsmith@ucla.edu
AF: University of California Los Angeles, Department of Geography, 1255 Bunche Hall, Box 951525, Los Angeles, CA 90095, United States
AU: Stroeve, J
EM: stroeve@kryos.colorado.edu
AF: National Snow and Ice Data Center, National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309-0449, United States
AU: Chu, V W
EM: vena.chu@gmail.com
AF: University of California Los Angeles, Department of Geography, 1255 Bunche Hall, Box 951525, Los Angeles, CA 90095, United States
AB: Continued reduction of Arctic sea ice may significantly alter the climate of the northern high latitudes and the mass balance of the Greenland ice-sheet. While sea ice loss and Greenland ice-surface melting both increased in the late-20th/early-21st century, the influence of sea ice on Greenland surface melt is unknown. In this presentation, we study the relationship between the variability of sea-ice/open-water and ice-sheet snow-melt extent by employing passive microwave satellite observations of both concurrently. We show that although melt and sea-ice/open-water extent vary independently in most of Greenland, anomalous covariability is observed in the general area of Kangerlussuaq, south-west Greenland. A prevalent time lag of approximately 0-2 days between the two variables suggests that sea-ice/open-water drive parts of the melt variability. In the Kangerlussuaq area, the anomalous sea-ice/open-water influence on melt variability may be a result of the proximity to the location of the average summertime sea ice edge in Davids Strait. We speculate that further northern retreat of sea ice could cause this covariability anomaly to also migrate north, to the vicinity of the Jakobshavn Isbrae.
DE: 0726 Ice sheets
DE: 0740 Snowmelt
DE: 0750 Sea ice (4540)
DE: 0758 Remote sensing
DE: 1620 Climate dynamics (0429, 3309)
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C31B-0501
TI: Warm Atlantic water drives Greenland Ice Sheet discharge dynamics
AU: * Christoffersen, P
EM: pc350@cam.ac.uk
AF: Scott Polar Research Institute, Lensfield Road, University of Cambridge, Cambridge, CB2 1ER, United Kingdom
AU: Heywood, K J
EM: k.heywood@uea.ac.uk
AF: School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, United Kingdom
AU: Dowdeswell, J A
EM: jd16@cam.ac.uk
AF: Scott Polar Research Institute, Lensfield Road, University of Cambridge, Cambridge, CB2 1ER, United Kingdom
AU: Syvitski, J P
EM: james.syvitski@colorado.edu
AF: Institute of Arctic and Alpine Research, University of Colorado, Boulder, CB2 1ER803, United States
AU: Benham, T J
EM: tjb52@cam.ac.uk
AF: Scott Polar Research Institute, Lensfield Road, University of Cambridge, Cambridge, CB2 1ER, United Kingdom
AU: Mugford, R I
EM: r.i.mugford@reading.ac.uk
AF: Scott Polar Research Institute, Lensfield Road, University of Cambridge, Cambridge, CB2 1ER, United Kingdom
AU: Joughin, I
EM: ian@apl.washington.edu
AF: Applied Physics Laboratory, University of Washington, Seattle, WA 98105, United States
AU: Luckman, A
EM: a.luckman@swansea.ac.uk
AF: School of the Environment and Society, Swansea University, Swansea, SA2 8PP, United Kingdom
AB: Greenland outlet glaciers terminating in fjords experience seasonal fluctuations as well as abrupt episodes of rapid retreat and speed-up. The cause of abrupt speed-up events is not firmly established, but synchronous occurrences suggest that it is related to Arctic warming. Here, we report major warming of water masses in Kangerdlugssuaq Fjord, East Greenland, immediately prior to the fast retreat and speed-up of Kangerdlugssuaq Glacier in 2004-05. Our hydrographic data show that this event occurred when Atlantic water entered the fjord and increased temperature of surface water by 4°C and deep water by 1°C. On the basis of meteorological records and satellite-derived sea surface temperatures, which fluctuate by up to 4°C in periods of 2-3 years, we infer that inflow of Atlantic water is controlled by the direction and intensity of prevailing winds that force coastal and offshore currents. Our results demonstrate that Greenland Ice Sheet discharge dynamics are modulated by North Atlantic climate variability, which is identified by shifts in the position of atmospheric low pressure over the Labrador and Irminger seas. A persisting westerly position of the Icelandic Low since 1999 may explain why winters in Greenland have been particularly mild during the last decade and it is feasible that widespread and synchronous discharge fluctuations from outlet glaciers, which resulted in high rates of ice loss in southeast Greenland, are a consequence of this synoptic condition.
DE: 0726 Ice sheets
DE: 0774 Dynamics
DE: 1621 Cryospheric change (0776)
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 4540 Ice mechanics and air/sea/ice exchange processes (0700, 0750, 0752, 0754)
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: U23F-01 INVITED
TI: Melting and surface mass balance over the Greenland ice sheet from satellite data, model results and ground measurements during IPY: extreme events and updated trends.
AU: * Tedesco, M
EM: mtedesco@sci.ccny.cuny.edu
AF: University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, United States
AU: * Tedesco, M
EM: mtedesco@sci.ccny.cuny.edu
AF: NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, United States
AU: * Tedesco, M
EM: mtedesco@sci.ccny.cuny.edu
AF: The City University of New York, 138th St. and Convent Av., New York, NY 10031, United States
AU: Fettweis, X
EM: xavier.fettweis@ulg.ac.be
AF: University of Liege, allée du 6 Août, Liege, 4000, Belgium
AU: van den Broeke, M
EM: m.r.vandenbroeke@uu.nl
AF: University of Utrecht, Princetonplein 5, Utrecht, 3584, Netherlands
AU: van de Wal, R
EM: r.s.w.vandewal@uu.nl
AF: University of Utrecht, Princetonplein 5, Utrecht, 3584, Netherlands
AU: Smeets, P
EM: C.J.P.P.Smeets@uu.nl
AF: University of Utrecht, Princetonplein 5, Utrecht, 3584, Netherlands
AB: The International Polar Year is offering a unique opportunity for demonstrating, following and getting involved with cutting-edge science. Many projects have been selected and many others have been stimulated and pushed forward by the discussions, results and new questions arising from the many collaborations within the IPY framework. In this study, we report results regarding an ongoing collaboration for improving snowmelt detection and surface mass balance estimation over the Greenland ice sheet from combined satellite data, model results and ground measurements. In particular, passive microwave observations are used to derived melt extent and duration over the entire Greenland ice sheet on a daily basis. These results are then compared with those obtained with a regional model (MAR), with the modeled net surface energy fluxes and with the trends of surface temperature collected along the coast at selected locations. Surface mass balance data of the Greenland ice sheet is also derived from the MAR model and compared with those from ground measuerements performed on the ablation zone of the west Greenland ice sheet along the 67° N latitude circle, at distances of 6, 38 and 88 km from the ice sheet margin at elevations of 490, 1020 and 1520 m a.s.l. Results are updated through the 2008 melting season and evaluated in the context of the 1979 – 2008 period. Satellite results show that 2008 was in agreement with the recently observed increase of melting over the Greenland ice sheet. Moreover, model results suggest a negative surface mass balance for the second year in a row, comparable to or lower than that modeled for 2007. Ground results are being analyzed at the moment of abstract submission and will be reported during the talk.
DE: 0700 CRYOSPHERE (4540)
DE: 0726 Ice sheets
DE: 0740 Snowmelt
DE: 0758 Remote sensing
DE: 0764 Energy balance
SC: Union [U]
MN: 2008 Fall Meeting
AN: C31C-0519
TI: Velocity changes in the ablation zone of the Greenland ice sheet.
AU: * wal, R v
EM: r.s.w.vandewal@uu.nl
AF: Institute for Marine and Atmospheric research Utrecht, Utrecht University, The Netherlands, Princetonplein 5, utrecht, 3584 cc, Netherlands
AU: Boot, W
AF: Institute for Marine and Atmospheric research Utrecht, Utrecht University, The Netherlands, Princetonplein 5, utrecht, 3584 cc, Netherlands
AU: Broeke, M v
AF: Institute for Marine and Atmospheric research Utrecht, Utrecht University, The Netherlands, Princetonplein 5, utrecht, 3584 cc, Netherlands
AU: Smeets, C
AF: Institute for Marine and Atmospheric research Utrecht, Utrecht University, The Netherlands, Princetonplein 5, utrecht, 3584 cc, Netherlands
AU: Reijmer, C
AF: Institute for Marine and Atmospheric research Utrecht, Utrecht University, The Netherlands, Princetonplein 5, utrecht, 3584 cc, Netherlands
AU: Oerlemans, J
AF: Institute for Marine and Atmospheric research Utrecht, Utrecht University, The Netherlands, Princetonplein 5, utrecht, 3584 cc, Netherlands
AU: Donker, J
AF: Institute for Marine and Atmospheric research Utrecht, Utrecht University, The Netherlands, Princetonplein 5, utrecht, 3584 cc, Netherlands
AB: Continuous Global Positioning (GPS) observations are used to study variations in the flow of the western ablation zone of the Greenland ice sheet. Velocities increase by a factor 4 within days of increased melt water production. Over a longer period of 17 years annual ice velocity in the region decreased slightly, suggesting an adjusting hydraulic system, where increased meltwater input increases the efficieny. Results along the K-transect are now available for a 3 year period with hourly low precision GPS measurements. At the same time weather station are operated at three sites including Sonic Height Ranger instruments which are used to study hourly ablation changes. In this presentation we will address the interannual variations in the flow characteristics.
DE: 0726 Ice sheets
DE: 0774 Dynamics
SC: Cryosphere [C]
MN: 2008 Fall Meeting
AN: C21A-0502
TI: Spatio-temporal Variability of Melt Intensity over the Greenland ice sheet from 2000-2005 using coupled MODIS Optical and Thermal Measurements
AU: * Lampkin, D
EM: djl22@psu.edu
AF: Department of Geography Department of Geoscience College of Earth and Mineral Sciences Pennsylvania State University, RM 313 Walker Building, University Park, PA 16801, United States
AB: Increased ice sheet velocity in the equilibrium zone of western Greenland Ice Sheet coincident with periods of summer melting has been demonstrated and attributed to infiltrated melt water that enhances glacial sliding. The assessment of surface melting beyond a binary classification of melt and no-melt events using passive microwave techniques, has been demonstrated using a liquid water fraction (LWF) retrieval model applied to higher resolution, cloud-free, composited MODIS optical and thermal data. Estimates of LWF were derived for composited periods from May through August for 2000 through 2005. An increase in the areal distribution of estimated LWF varies from (0-1%) during May to upwards of 15% later in the season inter- annually. A comparison to QuikSCAT derived melt zones indicate low LWF amounts associated with dry snow zones and higher LWF amounts with wet snow zones. This relationship holds spatially and temporally during the analysis period.
DE: 0726 Ice sheets
DE: 0736 Snow (1827, 1863)
DE: 0740 Snowmelt
DE: 0758 Remote sensing
SC: Cryosphere [C]
MN: 2008 Fall Meeting
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