Improved Monitoring of Subglacial Lake Activity in Greenland Using CryoSat-2 Swath Processed Data and TanDEM-X DEMs.

Subglacial lakes form beneath ice sheets and ice caps if water is available, and if bedrock and surface topography are able to retain the water. On a regional scale, the lakes modulate the timing and rate of freshwater flow through the subglacial system to the ocean by acting as reservoirs. More than one hundred hydrologically active subglacial lakes, that drain and recharge periodically, have been documented under the Antarctic Ice Sheet, while only approximately 20 active lakes have been identified in Greenland. Active lakes may be identified by local changes in ice topography caused by drainage or recharge of the lake beneath the ice. The small size of the Greenlandic subglacial lakes puts additional demands on mapping capabilities to resolve the evolving surface topography in sufficient detail to record their temporal behavior. Here, we explore the potential for using CryoSat-2 swath-processed data together with TanDEM-X digital elevation models to improve the monitoring capabilities of active subglacial lakes in Greenland. We focus on four subglacial lakes previously described in the literature, and combine the new data with ArcticDEMs to obtain improved measurements of the evolution of these four lakes.We find that with careful tuning of the swath-processor and filtering of the output data, the inclusion of these new data together with the TanDEM-X data provides important information on lake activity, documenting, for example, that the ice surface collapse basin on Flade Isblink Ice Cap was 30 meters deeper than previously recorded.