Thaw subsidence of a yedoma landscape in northern Siberia, measured in situ and estimated from TerraSAR-X interferometry

• Main Authors: Antonova, Sofia, Sudhaus, Henriette, Strozzi, Tazio, Zwieback, Simon, Kääb, Andreas, Heim, Birgit, Langer, Moritz, Bornemann, Niko, Boike, Julia
• Format: Conference Object
• Language: unknown
• Published: Bibliothek Wissenschaftspark Albert Einstein 2018
• Subjects: Ice; lena river; permafrost; Thermokarst; Siberia
• Online Access: https://epic.awi.de/id/eprint/48095/; https://hdl.handle.net/10013/epic.1fd822e9-8b1a-44c1-a614-bf6c76e07689

In permafrost areas, seasonal freeze-thaw cycles of active layer result in upward and downward movements of the ground. Additionally, relatively uniform thawing of the ice-rich layer at the permafrost table, contributing to net long-term surface lowering, was reported for some Arctic locations. We use a simple method to quantify surface lowering (subsidence) and uplift in a yedoma area of the Lena River Delta, Siberian Arctic, using reference rods installed deeply in permafrost. The seasonal subsidence was 1.7 ±1.5 cm in the cold summer of 2013 and 4.8 ± 2 cm in the warm summer of 2014. Furthermore, we measured a pronounced multi-year net subsidence of 9.3 ± 5.7 cm from spring 2013 to the end of summer 2017. Additionally, we observed a high spatial variability of subsidence of up to 6 cm across a sub-meter horizontal scale. This variability limits the usage of a pointwise measurement for a validation of spatially extensive remote sensing products. In summer 2013, we accompanied our field measurements with Differential Synthetic Aperture Radar Interferometry (DInSAR) on repeat-pass TerraSAR-X (TSX) data over the same study area. Interferometry was strongly affected by a fast phase coherence loss, atmospheric artifacts, and possibly the choice of reference point. A cumulative ground displacement map, built from a continuous interferogram stack, did not reveal a meaningful signal on the upland but showed a distinct subsidence of up to 2 cm in most of the thermokarst basins. There, the spatial pattern of displacement corresponded well with relative surface wetness identified with the near infra-red band of a high-resolution optical image. Our study suggests that (i) although X-band SAR has serious limitations for ground movement monitoring in permafrost landscapes, it can provide valuable information for specific environments like thermokarst basins, and (ii) due to the high sub-pixel spatial variability of ground movements, a validation scheme needs to be developed and implemented for future DInSAR studies in ...