Spatio-temporal Change in the Glaciers of Astore Basin (North-Western Himalaya), between 2016 and 2021 using Sentinel-2 Satellite Data

Abstract

About 2400 kilometers long Himalayan region hosts thousands of glaciers which covers about 40,000 km2 as per last update in September 2021. Estimation of snout variation positioning, statistical analysis of climate trends, and the Equilibrium Line Altitude (ELA) of most of the glaciers is challenging due to the rough terrain, higher altitudes and scarcity of spatio-temporal field observations. Moreover, without the climatic data and separating contour between glacier’s accumulation and ablation zones, estimation of the net variation in glacier mass loss or gain over a fixed year, leads to ambiguous results. Therefore, a quarterly trend analysis was carried out on climate data (temperature and precipitation ) and river discharge to evaluate the climate pattern in the Astore Basin. Moreover, this study uses the accumulation area ratio, AAR (0.6 ±0.5) (used for high-altitude mountain glaciers), and accumulation area balance ratio, AABR (2.24 ±0.9) with an interval of 0.05 and 0.01 to estimate ELAs, respectively. The results show that the Bazhin glacier retreat (-2.1 km²) as compared to the Chhongpher (-1.1 km²) and Chongra (-1.2 km²) glaciers. A maximum retreat of the snout position of Bazhin glacier was 1595 m , 3260 m in Chhongpher glacier, and 960 m in Chongra glacier. An increase in the ratio of annual AAR from 0.4 to 0.8 results in reductions of the accumulation area of three major glaciers in the study area. We conclude that the largest glaciers (e.g. Bazhin, Chhongpher and Chongra) stretched between lower to higher altitudes are likely to be more vulnerable, due to the highest AAR and AABR values reported between 5000-5600 meters above sea level (masl). However, the ice-lost estimates vary greatly depending on their three-dimensional surfaces.