HR: 1340h
AN: G43B-1197    [Abstracts]
TI: Elastic and viscoelastic crustal deformations in Greenland due to ice mass changes
AU: * Khan, S A
EM: abbas@space.dtu.dk
AF: 1, Danish National Space Center, DTU, Copenhagen, 2100, Denmark
AU: Wahr, J
EM: wahr@anquetil.colorado.edu
AF: 2, Department of Physics and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, United States
AU: Dam, T v
EM: tonie.vandam@uni.lu
AF: 3, University of Luxembourg, Luxembourg, L-1511, Luxembourg
AU: Larson, K M
EM: kristinem.larson@gmail.com
AF: 4, Department of Aerospace Engineering Sciences, University of Colorado, Boulder, CO 80309, United States
AU: Francis, O
EM: olivier.francis@uni.lu
AF: 3, University of Luxembourg, Luxembourg, L-1511, Luxembourg
AU: Leuliette, E W
EM: Eric.Leuliette@noaa.gov
AF: 5, National Oceanic and Atmospheric Administration, Silver Spring, MD 20910, United States
AU: Hamilton, G S
EM: gordon.hamilton@maine.edu
AF: 6, Climate Change Institute, University of Maine, Maine, ME 04469, United States
AU: Stearns, L A
EM: leigh.stearns@maine.edu
AF: 6, Climate Change Institute, University of Maine, Maine, ME 04469, United States
AB: 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 from the front of Greenland's Jakobshavn Isbr{\ae} Glacier. The GPS stations were established in bedrock to determine vertical crustal motion due to unloading of ice from Jakobshavn Isbrae. Results suggest a net loss of ~20 km3 of ice between May and August, 2006.
DE: 0720 Glaciers
DE: 0726 Ice sheets
DE: 1211 Non-tectonic deformation
DE: 1218 Mass balance (0762, 1223, 1631, 1836, 1843, 3010, 3322, 4532)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
SC: Geodesy [G]
MN: 2007 Fall Meeting