GLACIAL AND MARINE GEOLOGICAL EVIDENCE FOR THE ICE-SHEET CONFIGURATION IN THE WEDDELL-SEA ANTARCTIC PENINSULA REGION DURING THE LAST GLACIAL MAXIMUM

The Weddell Sea region arguably represents the largest unknown in quan tifying the Antarctic contribution to the global water balance followi ng the Last Glacial Maximum (LGM). This paper reviews the available on shore and offshore geological evidence constraining the volume of form erly expanded ice in the Weddell Sea embayment, focusing on the West A ntarctic Ice Sheet (WAIS) and provides a preliminary reconstruction of the WAIS during the LGM. Dating control is generally poor and so our WAIS reconstruction is based on the assumption that the evidence of mo st recent ice sheet expansion dates to the LGM. Our reconstruction is intended to provide initial constraints with which glaciological model s can be compared and shows grounded ice extent, flow directions, and ice surface elevations. Both marine and terrestrial geological evidenc e imply a substantial expansion of ice in the Weddell Sea embayment. M arine evidence shows that ice sheets were grounded in Crary Trough in the southern Weddell Sea and on the Antarctic Peninsula continental sh elf during the LGM. Inland, the ice thickened by between 400 m (Ellswo rth and Palmer Land) and 1900 m (Ellsworth Mountains). Ice core eviden ce suggests that the interior of the ice sheet remained the same or ev en thinned relative to present. The main unknowns now concern the exac t location of the grounding line on some sectors of the shelf and the timing of ice sheet grounding and retreat. The limited radiocarbon dat a that exist on the eastern shelf indicates that the East Antarctic Ic e Sheet retreated from the shelf prior to the LGM.