AN ANALYSIS OF THE ICE-SHEET SURFACE AND SUBSURFACE TOPOGRAPHY ABOVE THE VOSTOK-STATION SUBGLACIAL LAKE, CENTRAL EAST-ANTARCTICA

Radio-echo sounding (RES) and satellite radar-altimeter data were anal yzed in order to identify the surface and subsurface topography around the largest known subglacial lake, at Vostok Station, East Antarctica (named here as Lake Vostok). In doing so, a data set was established from which a qualitative description of the flow of ice across the lak e was developed. Patterns of ice flow were constructed through conside ration of (1) the ice-sheet surface from the satellite altimeter and ( 2) internal layering from RES. It is concluded that Lake Vostok influe nces the dynamics of the overriding ice. Specifically, although the fl ow of ice across the lake is dominated by the general eastward flow of the grounded ice sheet, a southward velocity component, caused by an ice-shelf-type ice-flow mechanism, is also present over the subglacial lake. A further 67 smaller subglacial lakes exist within central regi ons of the Antarctic Ice Sheet, occupying 5-10% of the ice-sheet base. Subglacial lakes may therefore exert a significant control on ice dyn amics within central Antarctica.