Rock glacier distribution and kinematics in Shigar and Shayok basins based on radar and optical remote sensing

Recent studies have demonstrated the rock glacier destabilisation and permafrost thawing induced by warming climate represent a continuous threat to life, infrastructure and socio-economic development in the mountainous regions of the Hindu Kush Himalaya. This study presents the first systematic rock glacier inventory for the Shigar and Shayok basins, quantifying rock glacier geomorphology and kinematics based on morphological evidence using Google Earth images and interferometric synthetic aperture radar (InSAR). The certainty index of each inventoried rock glacier is recorded, along with its geomorphological properties and kinematic attributes. The rock glacier velocity is estimated through the InSAR time series analysis of Sentinel-1 images from 2020 to 2021, with temporal baselines at 12-day intervals. We developed a rock glacier inventory consisting of 84 rock glaciers covering an area of 29 km² for the Shigar Basin and 2206 rock glaciers encompassing 369 km² for the Shayok Basin. Among these rock glaciers, 69% and 52% are categorised as active rock glaciers, respectively. Rock glaciers in both catchments are confined to elevations between 3600 and 5875 m a.s.l., with a mean area of 0.22 km². The maximum recorded velocity for active rock glaciers in the Shigar Basin is 101 ± 9 cm year⁻¹, with a median of 27 ± 10 cm year⁻¹, and in the Shayok Basin 114 ± 10 cm year⁻¹ (median of 29 ± 9 cm year⁻¹). Temporal variations in the surface velocities of the rock glaciers reveal that they increase with rising temperatures in both catchments, highlighting the seasonality in the rock glacier surface velocity. In total, we recorded the kinematic attributes of 98% of the inventoried rock glaciers in the study area.