Unusual surface morphology from digital elevation models of the Greenland ice sheet

In this study of the North Greenland ice sheet, we have used digital elevation models to investigate the topographic signatures of a large ice flow feature discovered in 1993 and a unique surface anomaly which we believe has not been observed previously. The small scale topography of the flow feature is revealed in striking detail in a high-pass filtered elevation model. Furthermore, ice penetrating radar show that the sub-stream bed is rough with undulation amplitude increasing downstream. The new feature consists of two large depressions in the ice sheet connected by a long curving trench. The low driving stresses in the region and the increased power of radio echo from the ice/bed interface over the feature clearly show presence of basal water. The shape of one of the two depressions and its location above a bedrock trough is indicative of a sub-glacial lake but we also see evidence suggesting that water transport through a basal hydrological system may be occurring.