Assessment of SWOT for monitoring ice-marginal lake water levels in Greenland

The Surface Water and Ocean Topography (SWOT) satellite mission provides a powerful data set for monitoring global surface water resources. However, its performance for monitoring ice-marginal lakes in Greenland remains unknown. Due to the scarcity of in situ measurements, this study evaluated the reliability of ice-marginal lake elevations derived from the SWOT Water Mask Raster Product by comparing to ICESat-2 LiDAR altimeter data. Results show that across 204 near-contemporaneous water level points for 110 lakes, the average deviation between SWOT and ICESat-2 was 0.03 m, with a root mean square deviation of 1.43 m, showing a good agreement. The higher temporal resolution of SWOT (<21 days over Greenland) enabled better monitoring of glacial lake outburst floods (GLOFs), with a 100% increase in the number of GLOFs detected compared to ICESat-2 between 2023 and 2024. These advantages make SWOT an excellent data source for monitoring ice-marginal lakes around the Greenland Ice Sheet.