Monitoring bedfast ice in lakes of the Lena River Delta using TerraSAR-X backscatter and coherence time series

• Main Authors: Antonova, Sofia, Duguay, Claude, Kääb, Andreas, Heim, Birgit, Langer, Moritz, Westermann, Sebastian, Boike, Julia
• Format: Conference Object
• Language: unknown
• Published: 2016
• Subjects: Ice; lena river; permafrost; Thermokarst; Tundra; Siberia
• Online Access: https://epic.awi.de/id/eprint/43259/; https://epic.awi.de/id/eprint/43259/1/AGU_poster_Antonova_final.pdf; https://hdl.handle.net/10013/epic.49741; https://hdl.handle.net/10013/epic.49741.d001

Thermokarst lakes and ponds are major elements of permafrost landscapes, occupying up to 40% of the land area in some Arctic regions. Deeper lakes (> 2 m) remain unfrozen beneath floating ice during winter, leading to the formation of talik, facilitating microbial activity and greenhouse gases production throughout the year. Shallower lakes (< 2 m) experience complete freezing down to the bottom which prevents talik formation and limits the length of the greenhouse gases production period. Thus, distinguishing floating from grounded lake ice is crucial for evaluating the thermal and geobiochemical state of tundra landscapes. A remote sensing method based on differences between radar backscatter intensity signatures is most frequently used to distinguish floating from bedfast ice. Although the method has been known since the 1970s, the potential of new generation satellite radar imagery has yet to be evaluated. Our study is based on a unique TerraSAR-X (TSX) data set that spans three winter seasons (2012-2013,2013-2014 and 2014-2015). We investigate the viability of TSX backscatter intensity time series with high spatial (10 m) and temporal (11 days) resolution for monitoring bedfast lake ice in the zone of continuous permafrost in the Lena River Delta, Siberia. In situ ice thickness measurements from a number of lakes were used for validation. Additionally, an 11-day sequential interferometric coherence time series was analysed as a supplementary approach for the bedfast ice monitoring and as an explorative step for a possible derivation of shallow lakes bathymetry based on InSAR. Results demonstrate that TSX backscatter intensity time series is an excellent tool for the monitoring floating/grounded lake ice regime. Particularly, due to a better temporal resolution of TSX data, retrieval of the timing of ice grounding is improved compared to previous studies which used RADARSAT or ERS data. The coherence time series is shown to detect most ice grounding and to have the potential to monitor freezing of ...