[S-TT40] 合成開口レーダーとその応用

[STT40-12] InSAR-based surface deformation reveals accelerated permafrost degradation in the Qilian mountains, Qinghai-Tibet Plateau

*Tian Chang^1,2,3、Yonghong Yi^1,2、Masato Furuya⁴ (1.Center for Spatial Information Science and Sustainable Development, Tongji University, Shanghai, China、2.College of Surveying and Geo-Informatics, Tongji University, Shanghai, China、3.Graduate School of Science, Hokkaido University, Sapporo, Japan、4.Department of Earth and Planetary Sciences, Faculty of Science, Hokkaido University, Sapporo, Japan)

キーワード：Permafrost, InSAR, Surface deformation, Qinghai-Tibet Plateau

Warming on the Qinghai-Tibet Plateau (QTP) has led to accelerated permafrost degradation, which manifests in observable surface subsidence and the deepening of the active layer (Zhao et al., 2024). Long-term monitoring of surface deformation is crucial for capturing the evolving trends of permafrost and active layer dynamics. Interferometric Synthetic Aperture Radar (InSAR) has proven to be an effective tool for detecting the surface deformation associated with these changes in permafrost regions (Liu et al., 2012; Yanagiya & Furuya, 2020). In this study, we used multi-source SAR data from ALOS-1, ALOS-2, and Sentinel-1 to analyze the long-term surface deformation in the Datong river basin of the Qilian mountain permafrost region in the QTP from 2007-2022. The deformation results show that flat areas with densely distributed small ponds undergo significant long-term subsidence (~5-20 mm/year) and seasonal subsidence (~30-50 mm). The observed subsidence correlates well with soil fragment content and ground ice content, indicating that the areas with higher ground ice and wet active layers are undergoing persistent permafrost degradation and are more sensitive to climate warming. The annual seasonal subsidence exhibits a generally consistent trend with the average air temperature during the thawing season in the region, demonstrating the direct influence of warming on active layer deepening. The sustained warming from 2019 to 2022, with a warming rate more than twice that of the period from 2007 to 2010, has led to a 25% increase in the subsidence rate compared to the earlier period. In addition to the effect of climate warming, we find that the most actively deforming areas with significant long-term and seasonal subsidence are rich in coal mining areas, and the excessive coal mining activities between 2004 and 2020 have likely contributed substantially to permafrost degradation. This human-induced disturbance further amplifies the region's vulnerability to warming. These findings provide valuable insights into the dynamics of ice-rich permafrost and its heightened vulnerability to environmental and human-induced changes, enhancing our understanding of permafrost-climate interactions in the QTP.