Melting Glaciers in the Western Himalaya: Evidence from In-Situ Seasonal and Annual Mass Balance Observations from the Ladakh Himalaya

Field-based seasonal and annual mass-balance observations collected over the past one decade from four benchmark glaciers in the Ladakh region of the western Himalaya, Viz., Pensilungpa, Drang-Drung, Kangrez, and Machoi, indicate a consistent and significant loss of glacier mass across all elevation bands. Mass-balance estimates, obtained from stake networks and snow-pit observations exhibit persistently negative annual values, with enhanced ablation in lower and mid-elevation zones and limited accumulation at higher elevations. The average annual glacier mass balance ranges from −0.4 to −1.4 m w.e. yr⁻¹, with glacier-specific mass balance ranges of −0.8 to −1.4 m w.e. (Pensilungpa), −0.6 to −1.2 m w.e. (Drang-Drung), −0.5 to −1.1 m w.e. (Kangrez), and −0.4 to −0.9 m w.e. (Machoi). Winter accumulation across these four benchmark glaciers ranges from +0.3 to +1.1 m w.e., while summer ablation varies between −0.8 and −2.0 m w.e., reflecting strong altitude-dependent glacier-melt. All glaciers show steep mass-balance gradients, with a pronounced melt in lower ablation zones, and limited but persistent accumulation at higher elevations in the accumulation zones. Drang-Drung and Kangrez exhibit relatively stronger winter mass gains at higher elevations, while Pensilungpa and Machoi display the most intense summer ablation. Although the accumulation zones still gain seasonal mass, but it is not enough to offset the significant ablation as the ablation zones dominate glacier area, causing cumulative negative mass balances. The upward-shifted equilibrium-line altitudes and the dominance of ablation over accumulation indicate the increasing glacier sensitivity to regional warming in the cold desert Ladakh region.

Based on typical uncertainties associated with stake measurements, density sampling, and spatial interpolation of point observation, the uncertainty in annual mass-balance is estimated at ±0.25–0.40 m w.e. yr⁻¹. Despite this uncertainty, the results robustly demonstrate significant glacier mass loss in the  Ladakh region, underscoring enhanced cryospheric vulnerability to climate change and potential impacts on hydrological regimes in the upper Indus basin. These findings are consistent with regional trends in the Himalaya showing accelerated ice loss and rising ELAs, underscoring the growing sensitivity of cold-arid glaciers to climate warming, once considered relatively resilient. Continued mass loss has significant implications for water security, climate adaptation, and glacier hazard risk management across the upper Indus basin.