Remote sensing insights into fragmentation and decline of glaciers in the Gyama Massif of Karzok, Ladakh (1980-2025)

Continuous observations of glaciers are critical for measuring climate variability and understanding its consequences for regional water supplies. This study presents a comprehensive assessment of glacier changes in terms of dimension, mass balance and surface velocity in the Gyama Massif, Karzok Range, Ladakh, from 1980 to 2025. In 1980, the Gyama contained 100 glaciers characterized by a mean area of ~0.50 km² (range 0.02–4.77 km²), steep mean surface slopes of ~26° (13–41°), and high mean elevations of ~5,797 m a.s.l. (5,590–6,140 m a.s.l.), indicating predominantly small, steep, high-altitude glacier systems. The glaciers in this region experienced a total deglaciation of ~41% between 1980 and 2025. Mass-balance measurements for 100 glaciers indicate a moderately negative mean mass balance of −0.18 ± 0.10 m w.e. y^-¹ for 2000–2018. Glacier flow velocities (1990–2022) exhibit a statistically significant decreasing trend of −0.13 m y^-¹, corresponding to a ~75% reduction in mean velocity over the 32-year period. The average velocity of all glaciers across the study period was 4.16 m y^-¹. The most pronounced areal losses occurred among the smallest glaciers: those <0.1 km² in 2000 experienced >80–100% area loss, and several glaciers disappeared completely. Glacier fragmentation increased substantially, with the number of discrete glaciers rising from 9 in 2015 to 14 in 2020 and 28 in 2025, reflecting progressive morphological disintegration associated with sustained mass loss.The substantial loss of glacier area across the Gyama Massif, together with progressive mass loss, has led to a marked slowdown in surface ice velocity, highlighting the strong coupling between glacier geometry, mass balance, and ice flow. The consistent glacier decline at very high elevations (mean ~5797 m a.s.l.) further points to the influence of elevation-dependent warming in this Trans-Himalayan region. We recommend sustained high spatio-temporal resolution remote sensing, complemented by targeted field observations, to improve glacier monitoring in this data-sparse high-altitude region. Such integrated approaches are essential for detecting glacier instability and evaluating impacts on regional hydrology and downstream water resources in the Trans-Himalaya.

Keywords: Remote sensing; Mass balance; Glacier velocity; Deglaciation; Glacier fragmentation; Ladakh Himalaya