Geomorphic coupling between proglacial lake dynamics and moraine failure: a new mechanism of GLOF hazard in the Samudra Tapu glacier system

Rapid glacier retreat across the Western Himalayas has led to the widespread expansion and deepening of proglacial lakes, increasing concerns over moraine stability and Glacial Lake Outburst Flood (GLOF) hazards. In this context, the present study investigates the coupled evolution of the Samudra Tapu glacier and its proglacial lake using multi-temporal Sentinel-1 SAR datasets spanning 2018–2024. The analysis focuses on lake-depth expansion toward the glacier snout and deformation of the moraine rim derived from InSAR-based techniques, enabling an assessment of their temporal interaction. Results indicate a progressive increase in lake depth from approximately 30 m during 2018–2020 to localized maxima of 60–69 m by 2023–2024. This evolution reflects enhanced and spatially variable meltwater inflow, subaqueous over-deepening, and alternating shallow–deep zones observed between 2020 and 2023. Concurrent InSAR-derived deformation patterns ranging from −0.52 m to +0.05 m correspond closely with periods of rapid lake deepening, suggesting moraine weakening driven by increased hydrostatic pressure. Notably, although lake depths appeared more balanced in 2024, deformation signals remained pronounced, indicating delayed mechanical responses of moraine materials to cumulative stress. Overall, integrating InSAR-based deformation mapping with satellite-derived bathymetry provides a robust framework for identifying instability zones and improving hazard assessment.