Geodetic mass balance reveals enhanced up-glacier thinning in four major High Mountain Asia glaciers

Assessing climate change impacts on High Mountain Asia glaciers is vital for the water security of millions downstream. While several studies focused on small-to-medium-sized glaciers, the changes and responses of large glaciers—key contributors to catchment hydrology—have not been studied in a detailed, comparative manner. Here, remotely sensed multi-temporal mass balance of the four large glaciers, Fedchenko, Baltoro, Bara Shigri, and Gangotri, located in geographically distinct sub-regions of High Mountain Asia, is estimated using ASTER-derived digital elevation models between 2009 and 2022. Results show an accelerated mass loss during the recent period (~ 2015–2022), compared to the preceding period (~ 2009–2015), with losses increasingly propagating up-glacier and contributing to a general slowdown in glacier surface velocity. ASTER-derived mass loss patterns align closely with independent, high-resolution Pléiades and ICESat-2 altimetry datasets. The response of different glacier surface types—debris-covered, clean-ice, and accumulation zones—is also examined to assess their mass loss characteristics. Increased mass loss, especially in lower glacier areas, is strongly linked to rising summer temperatures. Additionally, glacier velocity analysis using NASA’s ITS_LIVE and Sentinel-1-based products reveals a pronounced slowdown in lower glacier areas, consistent with accelerated mass loss observed over the last two decades. This study provides higher spatiotemporal resolution mass balance estimates for these four large glaciers than previously published regional estimates, cross-verified with high-accuracy elevation data. The observed up-glacier thinning, despite their varying climatic and geographical setting, signals ongoing warming at higher elevations, raising concerns for glacier health and regional water security.