Climate impacts of an ice sheet in East Siberia during the Last Glacial Maximum

Recent evaluations of geomorphological evidence in East Siberia strongly suggest that no ice sheet existed on the East Siberian Arctic Shelf during the Last Glacial Maximum (LGM), contrary to the hypothesis of some authors. Because most general circulation model (GCM) simulations of the LGM have included such an ice sheet, the impact of an East Siberian ice sheet is crucial for understanding previous model simulations of the LGM. The experiments in this study use the Global Environmental and Ecological Simulation of Interactive Systems (GENESIS) 2.0 GCM and the Equilibrium Vegetation Ecology (EVE) vegetation model to simulate the LGM climate with (previously published simulation) and without (new simulation) an East Siberian ice sheet. Most LGM simulations have shown increased southerly advection into Beringia resulting from the dynamics of the continental ice sheets, which acts to alleviate the hemispheric-glacial cooling in Beringia. The East Siberian ice sheer provides a secondary source of warm-air advection into Beringia. In the simulation with an East Siberian ice sheet a glacial anticyclone develops over the ice sheer during winter, resulting in subsidence of air flowing off the ice sheet, increased southerly advection along the western margin of the ice sheet, and warming to the south of the ice sheet. During summer the ice sheet blocks northerly flow from the arctic, also resulting in warming south of the ice sheet. The primary vegetation difference is in the ratio of tundra to polar desert. The more mild climate with the ice sheet present produces more tundra and less polar desert. (C) 2000 Elsevier Science Ltd. All rights reserved.