Estimation of paleo-extent and volume of glaciers in the Baspa basin, India

Understanding water resources' long-term availability under varying climatic conditions is vital for water security and adaptation strategies. Due to increased temperature and changes in precipitation patterns, the Himalayan glaciers undergo rapid mass loss. The extent of glaciation has varied considerably since the global Last Glacier Maxima (LGM), ~18-24 ka. Moraine studies provide a better understanding of glaciation’s paleo-extent and timing. This work investigates the extent of glaciation and volume in the Baspa basin during the global LGM. We reconstruct the extent and volume using different remote sensing techniques, including the laminar flow method (HIGHTIM), Topo to Raster tool, Volume – Area scaling, and polygon area method. These methods are applied on 61 glaciers in the basin, considering glacial geomorphology and topographic parameters of the terrain. The glacier boundary and moraines were delineated using Landsat 8 satellite image and high resolution google earth images. The current spatial distribution of ice thickness and volume was estimated using the HIGHTHIM model. Further, the ice thickness was extrapolated to the moraine area using the Topo to Raster tool of ArcGIS, with the help of Cartosat DEM to estimate paleo glacier volume. On smaller glaciers (area<1km²), the current and paleo volume was estimated using the volume-area scaling equation. The glaciated area covers about 161.3 ± 8 km² and the moraine area is calculated as 49.3 ± 0.46 km². The estimate suggests ice volume at LGM is 18.71 km³ and the current volume is 8.51 km³, i.e., about a 52% loss in ice volume from LGM. We propose estimating the mass loss in the current decades, which will help understand the acceleration of mass loss under global warming conditions.