The Role of Winter Warming in Permafrost Change Over the Qinghai‐Tibet Plateau

Winter warming is fast than summer warming on the Qinghai‐Tibet Plateau (QTP). However, no assessment of winter warming effects on permafrost has been attempted. Here we conducted hypothetical control experiments and used the Noah land surface model to evaluate the impacts of winter warming on the QTP permafrost. The results show that air temperature in winter (November–April) was increasing at a rate of 0.66 °C/decade during 1980s−2000s, over double that in summer (May–October). The mean annual ground temperature of permafrost increased by 0.13 °C/decade. The summer warming dominated the variations in thermal regime of permafrost before 2000. After that, the influence of winter warming on permafrost thermal regime has gradually grown and exceeded that of summer warming. Winter warming has amplified the thermal degradation of permafrost. Our findings reveal that alpine continuous permafrost on the northern QTP has experienced a prominent regional warming due to rapid winter warming since 2000. Plain Language Summary As the highest and largest permafrost region in mid‐latitudes, Qinghai‐Tibet Plateau (QTP) has experienced prominent winter warming in the past three decades. To date, no study has been made to assess the impacts of winter warming on the QTP permafrost. We used the Noah land surface model to investigate this effect, based on controlled experiments including a baseline representing historical climate conditions and two intentionally constituted hypothetical experiments that remove the winter (November–April) or summer (May–October) warming from the historical records. We analyzed the seasonal changes in air temperature, evaluated the effects of winter and summer warming on the changes of frozen ground in terms of several key indicators (including active layer thickness, permafrost area, mean annual ground temperature of permafrost, and maximum freezing depth of seasonally frozen ground) and investigated the possible underlying mechanism of winter warming on permafrost. The results indicate that winter warming accelerates permafrost thermal degradation. Especially since 2000, alpine continuous permafrost on the Qiangtang High Plain, Northern QTP, has undergone an obvious regional warming induced by rapid winter warming. Key Points Winter warming in past decades is over twice than summer warming over the Qinghai‐Tibet Plateau (QTP) The influence of winter warming on permafrost thermal regime exceeded summer warming over the QTP after 2000 Alpine c