Dynamics of the East Antarctic Ice Sheet

Abstract

The East Antarctic Ice Sheet has a maximum thickness of more than 4km, and covers the Antarctic continent between longitudes 30°W and 165°E. The ice flows down the surface slopes from high interior domes toward the coastline through two processes: (i) by temperature-dependent quasi-viscous internal deformation, mostly shear parallel to the bed, and (ii) by basal motion comprising water-lubricated sliding over a hard substrate or shearing of water-saturated subglacial sediments, where the basal ice is at the pressure-melting temperature. With average surface temperatures below −45°C, and precipitation ca. 0.1Myr−1 (ice equivalent) over much of its surface, the ice sheet is a polar desert. There is virtually no surface melting at present, and accumulation of snowfall on the ice sheet is approximately balanced by discharge of icebergs and melting beneath the floating ice shelves. Ice flow is channeled into relatively fast-moving ice streams and outlet glaciers near the margins. Both ice streams and outlet glaciers feed the floating ice shelves. While the East Antarctic Ice Sheet appears close to mass balance (steady state) at present, accelerated flow in outlet glaciers could draw down the center of the ice sheet, if its buttressing ice shelves should fail in a much warmer world.