Multi-decadal mapping of debris-covered glaciers in the Zanskar Himalaya using Landsat Time Series on Google Earth Engine.

Glaciers in the Himalaya are undergoing rapid transformation under sustained climate warming, with supraglacial debris (SGD) exerting a critical but complex control on melt and mass balance. This study provides a four-decade assessment (1990–2020) of SGD dynamics across the Zanskar Basin, western Himalaya, using Landsat time-series data and a Random Forest (RF) classifier implemented on Google Earth Engine (GEE). The classification framework integrated spectral, topographic, and index-based variables (NDVI, NDSI, NDWI, and band ratios) to improve discrimination between debris-covered ice, clean ice, and surrounding terrain. Results indicate a gradual increase in SGD cover from 69.43 km2 (1990) to 72.84 km2 (2020), accompanied by a decline in bare ice from 997 km2 to 973 km2. The most pronounced changes occurred within mid-elevation zones (4200-4600 m), reflecting enhanced debris influx from surrounding slopes and glacier dynamics. Case studies of the Durung Drung and Pensilungpa Glaciers reveal distinct debris-evolution trends, consistent with field evidence of heterogeneous melt processes influenced by debris thickness and distribution. These findings represent the first basin-wide, multi-decadal evaluation of SGD variability in the Zanskar Himalaya, providing new insights into debris–ice interactions and their implications for glacier stability and meltwater generation under ongoing climatic change. Research highlights: Four-decade mapping reveals steady supraglacial debris expansion in Zanskar Basin. Mid-elevation zones show strongest debris change driven by slope and melt processes. Glacier case studies reveal contrasting debris evolution shaping melt and stability. [ABSTRACT FROM AUTHOR]