Dynamics of Gangotri Glacier, India: unravelling the influence of climatic and anthropogenic factors

The 'Third Pole', home to numerous glaciers, serves as vital water reserves for a significant portion of the Asian population and has garnered global attention within the context of climate change due to their highly vulnerable nature. While a general decline in global glacial extent has been observed in recent decades, the pronounced regional imbalances across the Third Pole present a perplexing anomaly. To assess the impact of glacier mass changes in the Gangotri basin, we conducted a comprehensive analysis using remote sensing data to estimate spatially resolved mass changes from 2000 to 2023. Our glacier mass balance estimates were based on empirical models and the digital elevation model difference method. We also examine the relationship between glacier retreat and the variability of albedo and aerosols in the glacier ice. Analysis of the geodetic mass balance indicates that the glacier surface has decreased by 8.12 m, a loss of 0.49 m of water equivalent per annum (m.w.e. a^-1) between 2000 and 2014. The estimates and results revealed from the accumulation area ratio (AAR) mass balance, and ice velocity measurements indicate a negative mass balance of - 0.28 m.w.e. a^-1 for Gangotri between 2000 and 2023. Our analyses highlight both climatological and anthropogenic factors responsible for the accelerated rate of mass loss. Regional mass loss during the ablation season is primarily influenced by land surface temperature, yet the role of other factors, such as changes in surface albedo and light-absorbing impurities (LAIs), remains uncertain. Our analysis investigated temporal variations in mass balance values, while also considering changes in surface albedo and LAIs like black carbon (BC), organic carbon (OC) and dust concentrations. This analysis reveals that LAIs have an inverse relationship with albedo, where an increase in LAI concentration results in reduced albedo over the glacier. Consequently, as albedo decreases, the surface mass balance of the glacier also declines, which is further validated by the findings of this study. While this study highlights the detrimental effects of light-absorbing pollutants on the health of glacier, further investigation is necessary to comprehensively establish their role in reducing the albedo of the glacier surface and influencing associated mass loss.