HR: 09:15h
AN: C41D-06    [Abstracts]
TI: Inferred accumulation and thickness histories near the Ross/Amundsen divide, West Antarctica
AU: Conway, H
EM: conway@ess.washington.edu
AF: University of Washington, Department of Earth and Space Sciences Box 351310, Seattle, WA 98195 United States
AU: * Neumann, T
EM: tneumann@uvm.edu
AF: University of Vermont, Geology Department, Burlington, VT 05401 United States
AU: Waddington, E
EM: edw@ess.washington.edu
AF: University of Washington, Department of Earth and Space Sciences Box 351310, Seattle, WA 98195 United States
AU: Morse, D
EM: morse@utig.ig.utexas.edu
AF: University of Texas at Austin, Institute for Geophysics, Austin, TX 78712 United States
AB: The United States ice coring community has identified the ice divide between the Ross and Amundsen Seas as the next site for a deep U.S. coring effort (Inland WAIS). As part of this program, we have used ground based radar-detected internal layers (assumed to be isochrones) to derive depth-age relationships for a prospective ice core site in the Inland WAIS area (Site E, Morse et al. 2002). Site E is located approximately 30km from the current divide on the Ross Sea side. Our initial depth-age relationship is based on radar layers tracked from the dated ice core at Byrd to the prospective site. The depth of the oldest distinct radar layer (observed at 1.5 MHz) corresponds closely to an acidity event in the Byrd core, which has been attributed to `excessive volcanism' 17,500 yrs BP (Hammer et al., 1994). The traced-radar-derived time scale for Inland WAIS is compared with results from a one-dimensional flow model to infer possible combinations of past thinning, accumulation, and ice sheet geometry at the site since the last glacial maximum (LGM). We calibrate the model and generate an initial accumulation rate profile using the measured layer-thickness and depth-age records from the Siple Dome and Byrd ice cores. Our model is based on the formulation of Dansgaard and Johnsen (1969) and includes the effects of strain-thinning, variations in accumulation rate and ice thickness in the past and basal melting. This approach also allows us to extend the depth-age relationship beyond the oldest distinct radar layer. Our results suggest that the thick ice in the region (3,300m) makes the depth-age relationship relatively insensitive to small changes in ice thickness. Variations in layer thickness on short time scales (relative to the characteristic response time of ice thickness divided by accumulation rate) arise primarily from variations in accumulation rate. Model results also suggest relatively low accumulation ($\sim$50% present) during the LGM but slightly higher than present ($\sim$110%) during the early to mid-Holocene.
DE: 1655 Water cycles (1836)
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting