Surface displacement and velocity models at Lake NamCo (Tibetan Plateau) derived from Sentinel-1 data via InSAR time series analysis

These datasets display seasonal and multiannual surface displacement models based on microwave data of ESA's Sentinel-1 satellite system. The data was processed via Interferometric Aperture Radar (InSAR) time series techniques, using an adapted version of the Small BAseline Subset (SBAS) algorithm. The purpose of this study is to understand sediment flux mechanics, especially those related to permafrost and periglacial landforms, and how the changing climate may affect these processes in the NamCo area in the future. To that end we developped three surface displacement models. The freeze-thaw model describes seasonal surface displacement caused by freezing and thawing of the active layer in autumn and spring respectively. We observe vertical amplitudes of up to 20 mm in areas, where the water content of the soil is high. The multiannual velocity model shows the mean surface velocity over the entire time period of approximetly 3-4 years. Time series results of regions with a small slopes were decomposed from ascending and descending data to show the surface velocity component in vertical and east-west direction. Time series results of regions with a larger slope were projected in the downslope direction, with the assumption that creep and sliding processes are dominant, which transport sediment along the direction of the steepest slope. Most flat areas are relatively stable but we observe material accumulation near parts of the rivers and subsidence in some permafrost areas, which could be related to permafrost degradation. The fastest landforms are rockglaciers, which move with velocities of up to 24 cm/yr. The third model is the seasonal velocity model, where we compare the line-of-sight velocities of sloped areas in the summer months to the winter months. Most slopes slide signifcantly faster in summer, driven by the thawing ground due to higher air temperature and monsoonal rainfall, while most of the fastest moving landforms move with a constant velocity throughout the year