Evaluation and Prediction of the Thermal Melting Stability of Permafrost in the Source Region of Datong River Based on Geomorphic Classification

With the ongoing intensification of climate warming and human activities, the permafrost on the Qinghai–Tibet Plateau has exhibited a degradation trend characterized by rising ground temperatures and thickening active layers over the years. Particularly in ice-rich permafrost regions, thermal melting disasters, such as ground subsidence caused by thermal melting, pose a significant threat to infrastructure in permafrost areas. Based on monitoring data from the source region of the Datong River, this article developed a calculation model for active layer thickness (ALT) based on underlying surface types. Utilizing an underground ice distribution model established through geomorphic classification and lithological characteristics, in conjunction with the Nelson model, a risk evaluation of thermal melting disasters in the source region of Datong River was conducted. Based on the current warming trend, the future variation trend of ALT was predicted, and thermal stability was evaluated. The results indicated that ALT in the source region ranged from 1.0 to 3.5 m, with a close correlation between ALT and underlying surface types. The overall thermal stability of the source region is relatively satisfactory, yet it is inadequate in high-altitude areas and on bare ground. Compared to bare ground, swamp meadows and alpine meadows offer superior protective effects on the thermal stability of permafrost in the source region.