A First Look at the Snow/Ice Penetration Effect of SWOT Observations on Water Level of Global Glacial Lakes

Abstract The Surface Water and Ocean Topography (SWOT) mission promises quasi‐global monitoring of glacial lakes, yet the elevation difference arising from its Ka‐band radar penetrating lake snow/ice cover remains unquantified. This poses a challenge to assessing their level changes. We present the first quantification of this difference by intercomparing SWOT and ICESat‐2 surface elevations over 260 glacial lakes (>1 km 2 ) globally. Given ICESat‐2’s laser measures the snow/ice surface, we leverage near‐synchronous observations to treat the elevation difference as an empirical measure of the snow/ice penetration effect of SWOT. We find a globally consistent negative difference (SWOT minus ICESat‐2) of −0.25 m over the 1‐year period. This difference is dependent on season, amplifying by more than double from −0.15 m (warm) to −0.34 m (cold), with peak monthly differences nearly reaching −1 m. This study provides a framework for reconciling SWOT and ICESat‐2 observations, enabling long‐term, high‐resolution records of glacial lake variability.