MT-InSAR Unveils Dynamic Permafrost Disturbances in Hoh Xil (Kekexili) on the Tibetan Plateau Hinterland

Abstract

Hoh Xil is an uninhabited extremity secluded on the Tibetan Plateau hinterland. A complete mapping of ground motion variation in Hoh Xil is essential for in-depth understanding of terrain's responses to climate change on the Tibetan Plateau. However, the inaccessibility and extremely harsh environment impeded extensive field investigations on landform alteration and its formative process. Such difficulty can be resolved by Interferometric Synthetic Aperture Radar (InSAR), which enables a broad detection of subtle permafrost motions at millimeter precision. This study, for the first time, accomplished a Multi-temporal InSAR (MT-InSAR) deformation mapping from 2015 to 2020 in Hoh Xil, with a wide coverage of about 200,000 km 2 . 1,592 Sentinel-1 images were processed based on the small baseline subset (SBAS) technique. The results show that Hoh Xil was experiencing dynamic permafrost disturbances. Thawing permafrost with both the linear subsidence rate higher than 2 mm/yr and the periodic amplitude over 2 mm was primarily detected in areas of flat or gentle slopes. The InSAR cumulative deformation is highly correlated with permafrost thawing depth. Significant lag times were identified between seasonal oscillation of InSAR deformation and land surface temperature (LST). Thermokarst landforms of retrogressive thaw slumps and thermokarst lakes broadly formed and dynamically evolved as a consequence of permafrost degradation. Particularly, widespread thawing permafrost characterized by the spatial clustering of thermokarst lakes appeared to occur in areas adjacent to large lakes. The discovered dynamic permafrost disturbances in Hoh Xil manifested even the secluded Tibetan Plateau hinterland was facing the threat of climate change.

Spatiotemporal Mechanism-Based Spacetimeformer Network for InSAR Deformation Prediction and Identification of Retrogressive Thaw Slumps in the Chumar River Basin

“…The region exhibits high evaporation rates. Notably, Zhuonai Lake and Kusai Lake, typical glacier-fed lakes, along with Haidingnor and Salt Lake, mainly replenished by rainfall, derive their primary water sources from meltwater and precipitation, respectively [14,40,41]. Observations at the Hoh Xil station (QT01) from 2004 to 2017 showed an increase in the active layer thickness from 160 cm to 176 cm.…”

“…Additionally, the open data policy of the Sentinel-1 satellite has facilitated the application of InSAR technology for large-scale deformation measurement in permafrost areas. Alternatively, multi-temporal InSAR techniques (MT-InSAR) such as permanent scatterer interferometry (PSI) [9] and small baseline subset (SBAS) [10] have been successfully used to monitor seasonal changes and interannual surface elevation changes in permafrost areas of the QTP [11][12][13][14]. These studies have effectively monitored the freeze-thaw cycles of permafrost on the QTP, including combining seasonal deformation data with the Stefan model to invert the thickness of the active layer [15,16].…”