[S-TT35] Synthetic Aperture Radar and its application

[STT35-P07] Revealing high-resolution permafrost active layer thickness pattern in the Qinghai-Tibet Plateau using precision InSAR observations

*Tian Chang^1,2, Jiangping Han^1,2, Yonghong Yi^1,2, Tong Hao^1,2, Ping Lu^1,2, Yuliang Wen^1,2, Rongxing Li^1,2 (1.Center for Spatial Information Science and Sustainable Development Applications, Tongji University, 1239 Siping Road, Shanghai, China, 2.College of Surveying and Geo-Informatics, Tongji University, 1239 Siping Road, Shanghai, China)

Keywords:InSAR, Permafrost, Active layer thickness, Tibetan Plateau

Accurately assessing the status of active layer thickness (ALT) in permafrost regions is crucial for understanding the impact of climate change on permafrost degradation. Interferometric synthetic aperture radar (InSAR) technology has great potential for large-scale ALT mapping with high spatio-temporal resolution. However, few studies have showcased InSAR-based ALT mapping results at a regional or plateau scale on the QTP, including arid and semi-arid permafrost regions. In this study, we developed an improved InSAR-based ALT algorithm suitable for unsaturated active layer conditions, which takes advantage of InSAR-derived deformation data and accounts for the influences of the unsaturated active layer on surface deformation and soil water exchange in the active layer. Based on the deformation data obtained from the Small Baseline Subset Interferometry (SBAS-InSAR) technology as well as the bias-corrected ERA5-Land soil moisture data using the variational mode decomposition method, we applied our developed method to the regional scale and produced a first high-resolution (30 m) InSAR-derived ALT map in the Hoh Xil region of QTP from 2016 to 2019. The validation using In-situ observations shows an overall mean bias of -23 cm with an RMSE of 63 cm. The average ALT in the region is about 210±53 cm and the mean ALT has increased significantly by 23 cm (12%) from 2016 to 2019, where larger thickening is observed around expanding lakes. The results of this study are of great significance for understanding the ALT characteristics in this region where permafrost is in a degradation process.