Drainage basin delineation for outlet glaciers of Northeast Greenland based on Sentinel-1 ice velocities and TanDEM-X elevations

The drainage divides of ice sheets separate the overall glaciated area into multiple sectors. These drainage basins are essential for partitioning mass changes of the ice sheet, as they specify the area over which basin specific measurements are integrated. The delineation of drainage basins on ice sheets is challenging due to their gentle slopes accompanied by local terrain disturbances and complex patterns of ice movement. Until now, in Greenland the basins have been mostly delineated along the major ice divides, which results in large drainage sectors containing multiple outlet glaciers. However, when focusing on measuring glaciological parameters of individual outlet glaciers, more detailed drainage basin delineations are needed. Here we present for the first time a detailed and fully traceable approach that combines ice sheet wide velocity measurements by Sentinel-1 and the high resolution TanDEM-X global DEM to derive individual glacier drainage basins. We delineated catchments for the Northeast Greenland Ice Sheet with a modified watershed algorithm and present results for 31 drainage basins. Even though validation of drainage basins remains a difficult task, we estimated basin probabilities from Monte-Carlo experiments and applied the method to a variety of different ice velocity and DEM datasets finding discrepancies of up to 16% in the extent of catchment areas. The proposed approach has the potential to produce drainage areas for the entirety of the Greenland and Antarctic ice sheets.