Space geodesy as a tool for measuring ice surface velocity in the Dome C region and along the ITASE traverse

Dome C was chosen by the European Project for Ice Coring in Antarctica (EPICA) as the site for the drilling of a deep ice core. This paper presents results from geodetic surveys of ice velocities (absolute and relative) at Dome C and along a transect to Terra Nova Bay. The purpose of the surveys was to provide accurate data for the study of ice dynamics, particularly a strain network comprising 37 poles surveyed in 1995 and again in 1999. Data indicate that the ice surface at the poles closest to the topographic summit moves horizontally by up to a few mm a(-1) in a direction consistent with downslope motion of the ice sheet, while 25 km from the summit it moves up to 211 mm a(-1). The EPICA drilling site yields an interpolated velocity of about 15 +/- 10 mm a(-1) in a north-northwesterly direction. Analysis of the velocity field and surface topography reveals that the surface flow centre is nearly co-located with the dome summit, and that both are in a steady-state condition. The measured horizontal velocities are consistent with the remote-sensing result and provide accurate ground-truth control for flow mapping. Seven snow-firn cores, up to 53 m deep, were drilled during the Terra Nova Bay-Dome C traverse. Submerged velocity systems were installed at the borehole and measured using the global positioning system (GPS). First results show a steady-state condition. Measured (horizontal) ice velocities increase from the summit of the ice sheet to the coast, reaching about 28 m a(-1) at site GPS2A.