Accelerated Thermokarst Lake Expansion Associated With Ground Ice Melt in Permafrost Regions of the Northwest Tibetan Plateau

Abstract

As typical periglacial landforms, thermokarst lakes (TLs) are undergoing rapid evolution under ongoing climate warming and increasingly influence hydrological redistribution across the “Asian Water Tower.” However, systematic quantitative assessments of their long‐term dynamics and scale‐dependent driving mechanisms remain limited, particularly given the pronounced regional heterogeneity of permafrost environments. Using multi‐temporal Landsat and Sentinel‐2 imagery within the Google Earth Engine (GEE) platform, this study investigated the spatiotemporal dynamics and driving factors of TLs in the permafrost region of the northwest Tibetan Plateau (TP) from 1990 to 2025. The results show that the northwest TP currently contains 41,288 TLs with a total area of 993.53 km 2 . Small TLs (< 0.003 km 2 ) accounted for 44.3% of the total number but only 2.9% of the total area, whereas large TLs (> 0.2 km 2 ) represented only 1.9% of the total number while contributing 51.3% of the total area, revealing a pronounced scale‐dependent mismatch between lake abundance and area contribution. Most TLs were concentrated in regions characterized by continuous permafrost, ground ice content > 20%, mean annual ground temperatures between −2°C and 0°C, and active layer thicknesses < 200 cm. From 1990 to 2025, the number of TLs increased continuously, with a net gain of 28,629 lakes, representing an increase of 226%. The numbers of large, medium, and small TLs increased by 363%, 439%, and 119%, respectively, accompanied by area expansions of 393%, 376%, and 160%. XGBoost machine‐learning analysis indicated that warming‐induced ground ice melt created favorable geomorphic conditions for TL formation and expansion, while increasing air temperature and precipitation–evaporation imbalance acted as the dominant climatic drivers. In addition, enhanced extreme precipitation showed partial temporal synchrony with TL expansion, particularly around 2000 and 2025, when intensified precipitation extremes temporally coincided with more rapid TL evolution. These findings improve our understanding of thermokarst lake evolution in permafrost regions of the TP and provide important scientific support for assessing cryospheric geomorphic responses to continued climate warming.