HR: 0800h
AN: C51A-0087    [Abstracts]
TI: Solving for ice-surface elevation history in the southern Ross Sea using inverse methods and surface-exposure ages
AU: * Todd, C E
EM: toddce@plu.edu
AF: Department of Geosciences Pacific Lutheran University, 158 Rieke Science Center, Tacoma, WA 98447, United States
AU: Waddington, E D
EM: edw@ess.washington.edu
AF: Department of Earth and Space Sciences University of Washington, Box 351310, Seattle, WA 98195, United States
AU: Koutnik, M R
EM: mkoutnik@u.washington.edu
AF: Department of Earth and Space Sciences University of Washington, Box 351310, Seattle, WA 98195, United States
AU: Conway, H
EM: conway@ess.washington.edu
AF: Department of Earth and Space Sciences University of Washington, Box 351310, Seattle, WA 98195, United States
AU: Stone, J
EM: stone@ess.washington.edu
AF: Department of Earth and Space Sciences University of Washington, Box 351310, Seattle, WA 98195, United States
AB: Surface-exposure ages calculated from Be-10 concentrations in glacial erratics provide a history of ice-surface elevations along Reedy Glacier from approximately 17 kyr before present (B.P.) through the Holocene. These surface-exposure ages show that the most recent maximum ice thickness at Reedy Glacier occurred at different times at different locations along the glacier. For example, deposits at the Quartz Hills, located 70 m from the head of the glacier, have ages of 17.3 +/- 1.1 kyr – 14.3 +/- 0.9 kyr B.P., and indicate that the glacier surface was 250 m higher than present during this time. In contrast, deposits at the margin of McCarthy Glacier, a tributary of Reedy Glacier, show that ice thicknesses exceeded modern ice thicknesses by ~ 200 m from 9.4 +/- 0.7 kyr to 8.0 +/- 0.5 kyr B.P. Surface-exposure ages from nunataks near the mouth of Reedy Glacier provide a history of ice- surface elevations that begins approximately 7 kyr B.P., but these deposits do not capture the most recent maximum ice-surface elevation as these peaks were overrun by ice during the most recent maximum ice thickness in this area. The history of ice-surface elevation at the mouth of Reedy Glacier provides a useful constraint on past ice- surface elevations in the southern Ross Sea Sector of the West Antarctic Ice Sheet (WAIS). Improved constraints on ice-surface elevations in this region are needed to improve ice-sheet reconstructions of the WAIS during the last glacial maximum (LGM). Thus, we develop an inverse procedure to solve for the history of ice-surface elevations at the mouth of Reedy Glacier from surface-exposure-age data. We use an ice-flow model for our forward algorithm. This inverse procedure finds the history of ice-surface elevations that (1) yields glacier surfaces that best match our surface-exposure-age data at a defined tolerance, and (2) is within a range of ice- surface elevations that is physically reasonable. Results suggest that LGM ice thickness at the mouth of Reedy Glacier, in the southern Ross Sea Embayment, was approximately 1000 to 1200 m above modern sea level.
DE: 0700 CRYOSPHERE (4540)
SC: Cryosphere [C]
MN: 2007 Fall Meeting