Investigating 3D ice velocity variations of Rimo Glacier, Karakoram, using multitemporal Sentinel-1 ascending and descending SAR observations

To investigate the variation characteristics and evolution of the Rimo Glacier in the Karakoram Range, this study utilized Sentinel-1 ascending and descending SAR data from 2019 to 2024. We constructed a three-dimensional velocity time series of the glacier using the 3D Intensity Offset Tracking technique and derived ice elevation changes from ASTER data acquired in 2019 and 2025 to validate the reliability of the results. Offset tracking was implemented using GAMMA software, with the GLO-30 DEM employed to mitigate topographic effects. After post-processing and weighted averaging, interannual velocity maps were generated. Analysis revealed that glacier flow is predominantly eastward. Rimo South Glacier entered a surge phase in 2017, reached a peak velocity of ~1400 m yr-1 in 2019, representing an eight-to-nine-fold increase compared to its quiescent phase and subsequently stabilized. Rimo Central Glacier exhibited anomalous acceleration accompanied by thinning in the accumulation zone and thickening in the ablation zone, indicating it is in an early surge stage with potential destabilization risk in the future.