A 2020 permafrost distribution map of the Qinghai-Tibet Plateau

Abstract

Permafrost on the Qinghai-Tibet Plateau (QTP) is undergoing rapid degradation, yet most existing distribution maps reflect long-term historical averages rather than the current thermal state of the ground. This temporal mismatch limits their usefulness for ecological, hydrological, and engineering applications. Here, we present a 1 km resolution permafrost distribution map for the 2020 period using an extended ground surface frost number model (FROSTNUM) driven by satellite-derived freezing/thawing indices. Because no concurrent field survey was available, we applied a space-for-time substitution strategy with Random Forest regression to estimate the empirical soil parameter ( E ) from environmental covariates. The resulting map shows that permafrost covered approximately 1.038 × 10 6  km 2 (39.35 % of the QTP), while seasonally frozen ground (SFG) covered 1.466 × 10 6  km 2 (55.57 %). Compared with the 2010 baseline, the permafrost area declined by 4.8 × 10 4  km 2 (a 1.82 % decrease). Degradation was spatially heterogeneous: the transition from permafrost to SFG was dominant in the central QTP, whereas the southern margin experienced substantial conversion of SFG to non-frozen ground. Validations against 109 independent borehole records yielded an overall accuracy of 0.84 and a Kappa of 0.58, outperforming existing 2020-period maps. This map provides a temporally specific reference for engineering risk assessment, ecological monitoring and the calibration of land surface models in this rapidly changing region.