Warming-Driven Abrupt Shifts in Alpine Permafrost Dynamics With Elevation

Alpine permafrost constitutes a substantial climate-sensitive system due to compressed environmental gradients and elevation-dependent forcing. However, projection uncertainties persist from unresolved altitudinal thresholds governing permafrost responses. Here, we integrate large-scale thaw-depth investigations across Tibetan permafrost with regional climate, vegetation, and soil data sets, to identify an elevational transition between 4600 and 5000 m, where coupled climatic-vegetation-soil interactions shift abruptly. Below this range, vegetation-buffered permafrost is dominated by NDVI and SOC controls, while climate-exposed permafrost above it is governed by temperature. As warming intensifies across scenarios, maximum thaw-depth sensitivity to temperature rises by approximately 1.5-fold (from 0.17 to 0.25 m °C^-1). Projections incorporating this elevation dependence indicate near-linear Tibetan permafrost contraction, with 6.7%-64.6% area loss expected by 2100, liberating approximately 3.6-14.4 Pg C of cryolocked carbon subject to post-thaw biogeochemical release. These findings highlight the critical role of elevation-dependent controls in shaping permafrost-climate feedbacks and underscore the urgency of incorporating altitudinal thresholds into Earth system models to improve the accuracy of future carbon flux predictions from alpine permafrost regions.