HR: 10:55h
AN: C32A-03 INVITED     [Abstracts]
TI: GPS Measurement of Glacial Isostatic Adjustment in Antarctica: Current Results and Future Prospects
AU: * Raymond, C A
EM: Carol.A.Raymond@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Ivins, E R
EM: eri@fyrxell.jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: James, T S
EM: james@pgc.nrcan.gc.ca
AF: Pacific Geoscience Centre, Geological Survey of Canada 9860 West Saanich Road , Sidney, BC V8L 4B2 Canada
AB: Global Positioning System (GPS) measurements at bedrock sites in Antarctica hold the potential for partially testing chronological models for the mid-to-late Holocene (8-0 Ka) collapse of the West Antarctic Ice Sheet. A network of permanent GPS sites exists in Antarctica mainly at coastal sites, but sites in the interior of Antarctica, near present and paleo ice accumulation centers, are key to shedding light on the history of the Antarctic ice sheet. Considerable effort has been expended by several groups of investigators during the last decade to acquire these data. These efforts have resulted in several new data points with which to test current models of postglacial rebound. We have collected GPS data quasi-continuously between November 1996 and January 2001 at two autonomous GPS stations in the northern Transantarctic Mountains, only one of which produced a high-quality vertical rate time series. The vertical rate at Mt. Coates in the Dry Valleys indicates uplift of 4.5 ñ 2.3 mm/yr, most likely due to glacial isostatic motion. Uplift at Mt. Coates deviates significantly from uplift predictions based on deglaciation models ICE-3G and ICE-4G, but is consistent with the D91-1.5 model of variable and continued ice sheet ablation to 2 kyr and a viscosity of 10$^{21}$ Pa s in the upper mantle and 10$^{22}$ Pa s in the lower mantle beneath the region. The lack of spatial coverage at reasonable wavelength results in a predicted uplift rate that is largely insensitive to lithospheric thickness. The range of upper mantle viscosities indicated by the deglaciation model that includes persistent drawdown to 2 kyr suggests a subcratonic upper mantle. However, the large error estimates on this uplift rate allow upper mantle viscosities ranging from about 2 x 10$^{20}$ Pa s to nearly 10$^{22}$ Pa s. High-quality uplift data from the interior of the continent are key to providing stronger constraints on both deglaciation history and Earth rheology. Longer and more continuous time series from a network of stations that sample the spatial gradients in uplift are needed to advance better models of glacial isostatic adjustment and complement GRACE estimates of present-day ice mass change in Antarctica.
UR: http://geodynamics.jpl.nasa.gov/antarctica
DE: 8110 Continental tectonics--general (0905)
DE: 8159 Rheology--crust and lithosphere
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 1243 Space geodetic surveys
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting