Abstract

This study reconstructs nearly five decades of end-of-ablation-season snowline altitudes (SLAEoA) for 106 tongue-shaped glaciers in the Himalayan Climatological transitional zone using consistent Landsat observations. The regional mean SLAEoA (~4938 m asl) has risen by ~486 m, a robust and statistically significant increasing trend (Theil–Sen slope = 15.34 m year−1; Kendall’s τ = 0.659, p = 7.14 × 10−6), indicating a persistent reduction in glacier accumulation areas and increasingly negative mass balance under ongoing warming. Spatial patterns reveal strong control of Indian Summer Monsoon (ISM) moisture, elevation, glacier aspect, and morpho-topographic setting. Snowlines are generally lower in the south-eastern sector and higher in the north-west, while rates of snowline rise are greater in the southern and eastern regions, suggesting enhanced climatic sensitivity. Elevation-dependent trend analysis further shows that the rate of snowline rise decreases systematically with increasing glacier elevation, from 39.37 m year−1 for glaciers below 4500 m asl to 7.89 m year−1 for glaciers above 5500 m asl, indicating substantially greater sensitivity of lower-elevation glaciers to ongoing climatic change. Lower-elevation glaciers exhibit disproportionately rapid SLAEoA rise, suggesting that lower-elevation glaciers may be approaching critical thresholds at which accumulation zones cannot be sustained. Morphometric analysis shows that smaller, lower-elevation, and gently sloping glaciers respond more rapidly than larger and steeper ones. Aspect further influences variability, with south-facing glaciers showing higher and faster-rising snowlines than north-facing glaciers, though this contrast is diminishing over time. Climatic trends from ERA5-Land data indicate rising air temperatures and declining snowfall, identifying warming and reduced accumulation as primary drivers. The results support the hypothesis that the long-term rise in SLAEoA across the Himalayan climatological transition zone is primarily driven by regional warming and declining snowfall, while the magnitude of glacier response is further modulated by geometry and topography. Overall, SLAEoA emerges as a robust indicator of glacier health, highlighting accelerated cryospheric change in the transitional Climatological Himalaya with important implications for regional water resources.

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