Qinghai-Tibet Plateau wetting reduces permafrost thermal responses to climate warming

Abstract Permafrost, as one of the cryospheric indicators, is extremely sensitive to climatic changes. The Qinghai-Tibet Plateau has experienced remarkable warming and wetting since the mid-1990s. Its recent wetting alters thermal and hydrological properties in permafrost regions and inevitably affects permafrost thermal dynamics. While previous studies mostly focused on the effects of warming on permafrost, little attention has been paid to the effects of concomitant wetting. Here, a land surface model adapted for permafrost simulation is employed to quantitatively investigate the impacts of climate warming and wetting on permafrost thermal regimes by setting up a group of hypothetical numerical scenarios on the basis of historical meteorological records. The results reveal that climate wetting reduces permafrost thermal responses to warming and this effect is especially evident in the arid and semi-arid zones. It was estimated that one-degree warming induces an average increase of 0.46 m in active layer thickness (ATL) and 0.53 °C in temperature at the top of permafrost (TTOP), and a 100 mm wetting in summer precipitation leads to a mean decrease of 0.35 m in ALT and 0.36 °C in TTOP. Furthermore, we found through the simulations that increased summer precipitation imposes dual effects on permafrost in semi-arid high altitudes.