Accelerated Permafrost Thawing in the Source Region of the Yellow River Revealed by ALOS-1 and Sentinel-1 InSAR Monitoring

The source region of the Yellow River (SRYR) on the Qinghai-Tibet Plateau is a key runoff generation area for the Yellow River Basin, contributing approximately 35% of the river's water resources. Under the background of climate warming, permafrost was thawing accompanied with ground surface thaw settlement in the SRYR in recent years. Permafrost degradation has resulted in the lowered water table, shrinking lakes and wetlands and accelerated desertification, posing significant threats to ecological security and the sustainability of water resources in the SRYR. In this study, we analyzed spatiotemporal changes in permafrost degradation by deriving ground surface deformation from ALOS PALSAR data for 2007–2010 and Sentinel-1 data for 2017–2021. To better analyze variations in the deformation time series, two indicators—time-series correlation (TSR) and annual average growth rate (AAGR) were introduced to quantify the differences. Geodetector method was utilized to explore the factors influencing the spatial and temporal differences in permafrost degradation. The results show that, the average deformation rate in the study area was -2.1 and -9.2 mm/a during the 2007–2010 and 2017–2021 period, respectively, with an average seasonal deformation at approximately 19.8 and 14.1 mm, respectively. Approximately 40% of the area experienced varying degrees of degradation, primarily in the southern and northeastern of the SRYR. About 13% of the area showing an AAGR of ground deformation greater than 25%. The majority of areas experienced accelerated permafrost degradation were situated in plains, wetlands and regions where thermokarst lakes are widely distributed and developed. Differences in precipitation distribution and rising land surface temperature (LST) are the main drivers of the accelerated permafrost thawing in the SRYR.