Contribution Of The Ross Sea Sector, West Antarctica, To Holocene Sea-Level Rise

Evidence for thick ice in the Ross Sea Embayment during the last glacial maximum (LGM) comes from dates of elevated moraines alongside outlet glaciers through the Transantarctic Mountains (Denton et al., 1989), recently exposed nunataks in the Ford Ranges (Stone et al., 2003), and sediment cores from the western Ross Sea (Licht and Andrews, 2002). Some recent reconstructions constrained by geological data, call for ice that was ~700m thicker than present in the central part of the Ross Embayment. In contrast, emerging evidence based on thermo-mechanical simulations of ice streams (Parizek and Alley, 2004), analysis of ice-core stable isotopes (Steig et al., 2001), and geophysical analysis of the depth-age relationship from the ice core at Siple Dome (Waddington et al., 2005) indicates more modest changes in thickness (200-400 m of thinning). Low surface elevations in the central Ross Embayment during the LGM do not preclude thicker ice along the western and eastern boundaries, but an ice sheet of such low surface slope could extend 1000 km out to the continental shelf only if its bed was very slippery. A slippery bed could preclude thick ice in the center of the embayment. Alternatively, the grounded ice in the Ross Sea during the ice age might have come from the Transantarctic Mountains and Western Marie Byrd Land, rather than from the interior of West Antarctica. We estimate that the Ross Sea sector of the ice sheet has contributed ~2.5m sea-level rise since the LGM. Geologic evidence indicates deglaciation of the Ross Embayment, which started about 16 ka BP, was still underway at 7 ka along the Transantarctic Mountains, while glaciological and exposure-age evidence suggests that Roosevelt Island and the Ford Ranges continue to deglaciate today. It is unlikely that the Ross Sea sector contributed significantly to the rapid 15-m sea-level rise 14,500 years ago (meltwater pulse 1A), thought to have originated from Antarctica (Bassett et al., 2005).