High-Frequency observations of glacier ice velocities at Drang Drung Glacier, Western Himalaya, using a terrestrial time-lapse imaging system

Seasonal variations in the ice velocities of slow-moving glaciers ( < 100 m yr −1 ) in the high Himalaya ( > 4000 m a.s.l.) remain poorly documented, largely due to the lack of terrestrial observations and the substantial uncertainties inherent in satellite-based techniques. In this study, we present one of the first high-frequency observations of Drang Drung Glacier (33.76°N, 76.30°E) obtained from a terrestrial time-lapse camera (TLC) system, spanning from October 2023 to April 2025. Most of the Drang Drung Glacier’s ice front terminates in a lake, with a small fraction extending onto land. We found spatially heterogeneous ice velocity variations across the lake- and land-terminating regions of the glacier. Annual average at the lake-terminating region (35.4 m yr −1 ) was nearly double compared to the land-terminating region (19.5 m yr −1 ). In these regions, we observed a first cycle of speedup (June-September) and slowdown (September-November), corresponding to an increase in air temperature and solar radiation values. This behaviour is likely driven by meltwater-induced evolution of the subglacial drainage channel network from inefficient to efficient channel networks. An active subglacial hydrology and its seasonal transitions were also captured in the TLC images. The second cycle of minor speedup (November-January) and consistent slowdown until February suggests that viscous deformation led to channel closure and subsequent pressurisation by trapped water. The vertical ice velocity exhibited significant variations ( − 0 . 9 to − 2 . 0 m month −1 ) during June to October, whereas almost no changes were recorded for the other periods. Sub-weekly observations showed simultaneous glacier acceleration, lake turbidity changes, and ice-front uplift, also suggesting the role of basal water pressures in controlling ice velocity. Our results agree with in-situ GNSS-based ice velocity values and show that ITS_LIVE velocity products significantly underestimate the glacier surface velocity for Drang Drung Glacier. This study demonstrates the potential of TLC systems for resolving glacier dynamics at high resolution, which can be further useful for validating and improving satellite-based velocity products in high-altitude regions. • First high-frequency ice velocity observations of the slow-moving Himalayan glacier. • Lake-terminating regions show double the velocity of land-terminating areas. • Seasonal speedup linked to subglacial drainage evolution from spring to autumn. • Sub-weekly velocity peaks coincide with lake turbidity and terminus uplift events. • ITS_LIVE product underestimated ice velocities for slow-moving Himalayan glaciers.