Non-Negligible Contribution to Seasonally Thawing Depth of Active Layer From Extreme Warming Events in the Tanggula Permafrost Region of Qinghai-Tibet Plateau

Despite rising interest in the impacts of long-term gradual climate warming on permafrost changes, little is known about the changes in active-layer thermal conditions after transient and abrupt extreme warming events. Here, we investigated the Tanggula permafrost region of the Qinghai-Tibet Plateau using in situ meteorological and active-layer hydrothermal data. The results showed that the magnitude of variation in the thermal condition of the active layer was positively correlated with the duration and intensity of extreme warming events. The average contribution rate of extreme warming events to seasonally thawing depth was 13.5% ± 4.9% from April to October, and higher rates occurred in the initial and final stages of the thawing process. The thawing process of the active layer was the main factor controlling the thermal responses of this layer to extreme warming events. Moreover, the interannual differences in active-layer thermal conditions during the thawing period were likely related to the interannual differences in the frequency and intensity of extreme warming events.