InSAR time series analysis of seasonal surface displacement dynamics on the Tibetan Plateau

• Main Authors: Reinosch, Eike, Buckel, Johannes, Dong, Jie, Gerke, Markus, Baade, Jussi, Riedel, Björn
• Format: Text
• Language: English
• Published: 2019
• Subjects: The Sentinel; Ice; permafrost
• Online Access: https://doi.org/10.5194/tc-2019-262; https://www.the-cryosphere-discuss.net/tc-2019-262/

Climate change and the associated rise in air temperature have affected the Tibetan Plateau to a significantly stronger degree than the global average over the past decades. This has caused deglaciation, permafrost degradation and increased precipitation, heavily changing the water balance of this region. Surface displacement processes are likely to change as the ground continues to warm up and as such it is vital to understand both seasonal and interannual processes dynamics. The Nam Co area is well suited to studying these processes via Interferometric Synthetic Aperture Radar (InSAR) time series analysis, due to its lack of higher vegetation and relatively thin snow cover. The short revisit time of the Sentinel-1 system further reduces the risk of temporal decorrelation, making it possible to produce surface displacement models with good spatial coverage. We created three different surface displacement models to study freeze-thaw processes, seasonal sliding and linear creep. Most slopes of the area are unstable, with velocities of 8 to 17 mm yr −1 , and some landforms reach velocities of up to 18 cm yr −1 . The monsoonal climate accelerates those movements during the summer months through high temperatures and heavy rainfall. The fastest moving landforms, some of which have been identified as rock glaciers, do not follow this seasonal pattern of accelerated velocity in summer, instead they follow a linear sliding pattern. It is unclear if this linearity is connected to the ice content in those landforms. Flat regions at Nam Co are mostly stable on a multiannual scale but some experience subsidence, which could be caused by permafrost degradation. We observe a very clear seasonal freeze-thaw cycle in the valleys, where thawing and subsequent freezing of the active layer cause a vertical oscillation of the ground of up to a few centimeters, especially near streams and other water bodies.