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

The Surface Water and Ocean Topography (SWOT) satellite mission provides a powerful dataset 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.