Surface-deformation monitoring in the permafrost regions over the Tibetan Plateau, using Sentinel-1 data

摘要

Differential Interferometric Synthetic Aperture Radar (D-InSAR) has been widely used to measure surface deformation over the Tibetan Plateau.However,the accuracy and applicability of the D-InSAR method are not well estimated due to the lack of in-situ validation.In this paper,we mapped the seasonal and long-term displacement of Tanggula (TGL) and Liangdaohe (LDH) permafrost regions with a stack of Sentinel-1 acquisitions using the Small Baseline Subset InSAR (SBAS-InSAR) method.In the TGL region,with its dry soils and sparse vegetation,the InSAR-derived surface-deformation trend was consistent with ground-based leveling results;long-term changes of the active layer showed a settlement rate of around 1 to 3 mm/a due to the melting of ground ice,indicating a degrading permafrost in this area.Around half of the deformation was picked up on monitoring,in contrast with in-situ measurements in LDH,implying that the D-InSAR method remarkably underestimated the surface-deformation.This phenomenon may be induced by the large soil-water content,high vegetation coverage,or a combination of these two factors in this region.This study demonstrates that surface deformation could be mapped accurately for a specific region with Sentinel-1 C-band data,such as in the TGL region.Moreover,although the D-InSAR technology provides an efficient solution for broad surface-deformation monitoring in permafrost regions,it shows a poor performance in the region with high soil-water content and dense vegetation coverage.