Variations in seasonally frozen ground over the Tibetan Plateau from 2021 to 2100

Under the background of climate warming, the degradation of frozen ground over the Tibetan Plateau (TP) will lead to a series of hydrological and ecological environmental issues. Therefore, it is important to study how seasonally frozen ground (SFG) will change in the future, especially on a finer scale. This study focuses on the maximum freeze depth (MFD) and freeze-thaw period (FTD) of SFG over TP from 2021 to 2100, based on air temperature and precipitation data with a 1 km×1 km spatial resolution from 13 CMIP6 models, using a well-tested fitting method. The study also evaluates how vegetation will change responds to changes on SFG. The results show that under the shared socioeconomic pathway SSP245, the average MFD and FTD over TP will be 118.4 cm and 198 days in the near future (2021-2040). In the far future (2081-2100), MFD and FTD will decrease to 92.1 cm and 177 days, considering the increased extent of SFG. Under the more extreme SSP585 scenario, the MFD and FTD will drop even further, reaching only 53.7 cm and 143 days, respectively. As radiative forcing increases, the rates of these decreases will also speed up. The impact of different socioeconomic pathways on MFD will be more significant at high altitudes, the MFD and FTD will show a faster decline as altitude increases. Vegetation indices, such as LAI, NPP, and GPP, will rise more sharply with the stronger degradation of SFG. This highlights the strong link between SFG changes and vegetation growth.