Potential subglacial lakes derived from a new DEM from Cryosat-2 and satellite optical image in the David Glacier, Antarctica

Abstract

The potential subglacial lake locations and melt w ater path ways can be simply determined from the hydraulic potential surface in the Antarctica. The hydraulic potential is usually calculated using ice thickness and bedrock topogra phy. However, the current data sets of ice thickness and be drock topography (e.g. BEDMAP2) are not accurate enoug h to predict correct subglalcial lake locations in the David Gl acier, Antarctica. In order to improve the quality of hydraulic potential estimates, we constructed a new high-resolution d igital elevation model (DEM) by means of combining the Cr yosat-2 measurements and the satellite optical images geo statistically. The Cryosat-2 has a disadvantage that the gro und tracks are quite irregular over an area with rough topog raphy so that the radar altimetry often fails to measure the elevations in topographic hollows. To overcome this limitati on, we generate a relative elevation distribution from a singl e satellite optical image and a method called as "shape fro m shading" and combine it with the Cryosat-2 measuremen ts using the simple Kriging with local mean. The new DEM model corresponds well with the ICESat measurements. Th e improved DEM is used to map the hydraulic potential. As a result, the active subglacial lake David 1 (D1), already dis covered by the ICESat measurements, has several hydrauli c sinks indicating that the lake D1 is not a single lake. In ad dition, the ICESat tracks with large elevation change rates well agree with the potential subglacial lake locations. The GPS measurements for more than 5 months at two sites in the lake D1 also support this result.