GEODETIC OBSERVATION AND INTERPRETATION OF ICE FLOW VELOCITIES IN THE SOUTHERN PART OF SUBGLACIAL LAKE VOSTOK

Results of geodetic in-situ observations of ice-flow velocities in the southern part of subglacialLakeVostokare combined with data sets of the ice surface topography, ice thickness, surface accumulation, basal accretion and firn/ice density for interpretations regarding the glaciological setting of theLakeVostoksystem. Based on the ice-flow velocities and the ice thickness, mean surface accumulation rates are derived applying the flux gate method. These are representative for surface segments extending from the southern part ofLakeVostokto the Ridge B ice divide. They are consistent with the present-day accumulation rate at Vostok station and its variation upstream and thus suggest that the area has been close to steady state. In addition, ice-flow dynamics are investigated along a flow line segment extending from26 kmupstream to12 kmdownstream from Vostok station. The analysis suggests deficiencies in current modelling approaches within the transition zone from floating to grounded ice.