Antarctic topography and kilometre-scale roughness derived from ERS-1 altimetry

The ERS-1 satellite has delivered altimetric data since 1992, enabling us to map most of the Antarctic ice-sheet topography south to 82° S with better precision than all previous techniques. An algorithm has been developed such that the accuracy of the height data reaches the sub-metre level. As a first step, an inverse method has been designed to map the large-scale global topography, which is of interest to the study of the ice-sheet flow dynamics. As a second step, an adapted inverse algorithm displays precisely the short-scale undulations which are controlled by the bedrock below the ice. Finally, variations in the back-scattered altimetric signal allow us to map directly the kilometre-scale roughness that is related to the basal-flow conditions. Together, these maps constitute an important data base for modelling the ice sheet.