HR: 09:15h
AN: C11B-06 INVITED     [Abstracts]
TI: Extent of West Antarctic Ice Sheet During the LGM, Timing of Retreat and Potential Contribution to MWP Ia
AU: * Anderson, J
EM: johna@rice.edu
AF: Rice University, Department of Earth Sciences, Houston, TX 77251-1892
AU: Lowe, A
EM: Ashley.Lowe@usap.gov
AF: Raytheon Polar Services Du, P.O. Box 4465, Durango, CO 81302
AU: Mosola, A
EM: amanda.b.mosola@exxonmobil.com
AF: ExxonMobil, Upstream Research Company, Houston, TX 77252
AU: Oakes, L
EM: lmoakes@hotmail.com
AF: Rice University, Department of Earth Sciences, Houston, TX 77251-1892
AB: An extensive marine geological data set has been acquired from the West Antarctic continental shelf, including all of the major troughs that occur seaward of major drainage outlets. Swath bathymetry records show a progression of geomorphic features on the continental shelf that range from subglacial meltwater features to drumlin fields to mega-scale glacial lineations in an offshore direction. There is evidence for catastrophic outbursts of meltwater beneath the ice sheet within Pine Island Bay and Marguerite Bay. Mega-scale glacial lineations comprised of soft, deformation till indicate that the ancestral WAIS was drained through ice streams that, in the case of the eastern Ross Sea, extended over a thousand kilometers to the continental shelf edge. Hence, over-extension of ice streams and subglacial meltwater outbursts may have contributed to ice sheet instability and retreat. The largest drainage system occurs in the eastern Ross Sea and southern Weddell Sea. Severe sea ice conditions have limited data acquisition in the southern Weddell Sea, but a detailed study has been conducted in the eastern Ross Sea. There, the ice sheet appears to have retreated rapidly from the continental shelf, but the distribution of grounding zone wedges suggests a somewhat diachronous retreat for different ice streams. Our efforts to constrain the timing of ice sheet retreat from the shelf focused on dating the oldest glaciomarine sediments resting on till. Unfortunately, no carbonate was recovered from cores in the eastern Ross Sea, so the timing of retreat of this portion of the ice sheet is based on TOC dates, and uncertainty about reservoir effects limits our ability to constrain the retreat history. What is implied by the combined data is that the ice sheet appears to have retreated rapidly from the shelf soon after the LGM. In western Marie Byrd Land, the ice sheet retreated from the continental shelf prior to 13 Ka. In Pine Island Bay, retreat occurred in two stages. The ice sheet retreated from the continental shelf prior to 16 Ka and from the bay by 10 Ka. A similar two-stage retreat occurred in Marguerite Bay where the ice sheet retreated from the continental shelf by 12 Ka and from the bay by 8 Ka. The one thing that these areas have in common is that retreat from the shelf was rapid, as indicated by a paucity of recessional geomorphic features and sedimentary facies, and by deep iceberg scours that reflect calving of the ice sheet margin. But, retreat of the WAIS from the continental shelf appears to have been somewhat diachronous, which reflects the different geological and glaciological controls on ice stream extent and stability. The existing data do not indicate a substantial WAIS contribution to MWP 1a.
DE: 1827 Glaciology (0736, 0776, 1863)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4207 Arctic and Antarctic oceanography (9310, 9315)
DE: 4556 Sea level: variations and mean (1222, 1225, 1641)
DE: 9310 Antarctica (4207)
SC: Cryosphere [C]
MN: Fall Meeting 2005