A 2020 permafrost distribution map over 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, failing to capture the current thermal state required for accurate ecological and hydrological modeling. To address this temporal mismatch, this study presents a 1-km QTP permafrost distribution map for the year 2020. We employed an extended ground surface frost number model (FROSTNUM) driven by satellite-derived freezing/thawing indices. To overcome the lack of concurrent field surveys for parameter calibration, we implemented a space-for-time substitution strategy, utilizing a Random Forest regression to robustly estimate the empirical soil parameter (E) based on environmental covariates. The resulting map reveals that in 2020, permafrost covered approximately 1.038 × 10⁶ km² (39.35 % of the plateau), while seasonally frozen ground (SFG) covered 1.466 × 10⁶ km² (55.57 %). Compared to the 2010 baseline, the permafrost area declined by 4.8×10⁴ km² (a 1.82 % decrease). Spatially, the degradation of permafrost to SFG extensively occurred in the central QTP (accounting for 7.41 % of the total change), and a significant marginal contraction of SFG to non-frozen ground in the southern margin (accounting for 39.62 % of the total change). Validations against 109 independent borehole records from the 2020 period confirms the map’s reliability, achieving an overall accuracy of 0.84 and a Kappa of 0.58. This 2020 map provides an essential, up-to-date resource for quantifying the recent cryospheric shifts and supporting engineering risk assessments in this climate-sensitive region.