Using InSAR for Surface Deformation Monitoring and Active Layer Thickness Retrieval in the Heihe River Basin on the Northeast Qinghai‐Tibet Plateau.

In cold regions characterized by perennially frozen soil, climate warming has caused permafrost degradation, which is manifested by surface deformation and deepening of the active layer. Interferometric synthetic aperture radar (InSAR) is a common method to obtain large‐scale surface deformation, especially in mountainous terrain where it is difficult to install a large number of monitoring sites. Here, we used Sentinel‐1A SAR data acquired from March 2017 to March 2021 to monitor surface deformation and estimate active layer thickness (ALT) using two methods—temperature‐based and soil moisture‐based—in the permafrost regions of the Heihe River Basin on the northeast Qinghai‐Tibetan Plateau. We find that the seasonal deformation amplitude ranges 10–60 mm, and the annual mean vertical deformation trend ranges from −40 to 30 mm/a. We verify the ALT estimates with observations and find that the method based on soil moisture has higher accuracy and is therefore more applicable in this particular study area. The ALT gradually decreases from the southeast to the northwest, ranging from 0.3 to 6.5 m, with an average value of 2.47 m. These results contribute to better quantifying the response of permafrost change and to understanding the spatial distribution of ALT on a large scale, serving as guidance for engineering and other applications. Plain Language Summary: The effects of global warming have led to the degradation of permafrost. To quantify changes in permafrost, we use InSAR (Interferometric Synthetic Aperture Radar) technology to monitor the surface deformation in permafrost area. The main manifestation of permafrost degradation is the deepening of the active layer (AL). Therefore, we investigate the feasibility of obtaining AL thickness in the permafrost zone based on InSAR. Mean AL thickness in the Heihe River Basin is 2.47 m and ranges 0.3–6.5 m. Compared with temperature‐based inversion models, the inversion model for ALT based on the soil moisture content has a higher accuracy. Key Points: Surface deformation based on interferometric synthetic aperture radar can be used to quantify active‐layer thickness (ALT) with high resolutionMean active layer thickness in the Heihe River Basin is 2.47 m and ranges from 0.3 to 6.5 mThe inversion model for ALT based on the soil moisture content has a higher accuracy when combined with the temperature‐based inversion model [ABSTRACT FROM AUTHOR]