Spatiotemporal Displacement and Frozen-Ground Conditions of the Baishuigou Rock Glacier Revealed by InSAR and In Situ Observations

Rock glaciers are important geomorphic indicators of mountain permafrost conditions, yet the mechanisms controlling spatially heterogeneous deformation within individual rock glaciers remain poorly understood. This study investigates the Baishuigou Rock Glacier (BRG) in the Qilian Mountains by integrating multi-year InSAR observations, borehole stratigraphic data, and ground-temperature measurements to characterize its deformation and explore its relationship with permafrost degradation. The results reveal pronounced spatial heterogeneity in surface displacement. The main body of the rock glacier exhibits persistent displacement, with mean annual LOS displacement rates ranging from −6.93 to 13.19 mm yr−1, corresponding to relatively well-preserved ice-rich frozen ground. The frontal zone shows stronger and more variable displacement under more degraded subsurface conditions, whereas the relict rock glacier area exhibits relatively weak displacement dominated by seasonal thermal responses. Comparisons among the borehole sites further indicate that spatial differences in surface displacement correspond to variations in active-layer thickness, ground-ice conditions, and thermal state. The integrated observations suggest a possible spatial transition from relatively well-preserved ice-rich frozen ground in the upper part of the rock glacier toward more degraded conditions downstream. This study demonstrates that integrating surface deformation with subsurface structural and thermal observations provides stronger physical constraints for understanding spatially heterogeneous rock glacier deformation and its relationship with frozen-ground conditions.