Observation of thaw and freeze processes in an arctic tundra landscape with TerraSAR-X and RADARSAT-2 data
Space-borne imaging radar is a suitable tool for the detection of thaw and freeze processes, as the backscattering of radar waves is highly dependent on the dielectric properties of the surface. The backscattered intensity from frozen and unfrozen wet soils in Siberia differed by 3 to 4 dB using C-b...
| Main Authors: | , , , |
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| Format: | Conference Object |
| Language: | unknown |
| Published: |
2012
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| Subjects: | |
| Online Access: | https://epic.awi.de/id/eprint/25857/ https://hdl.handle.net/10013/epic.38788 |
| Summary: | Space-borne imaging radar is a suitable tool for the detection of thaw and freeze processes, as the backscattering of radar waves is highly dependent on the dielectric properties of the surface. The backscattered intensity from frozen and unfrozen wet soils in Siberia differed by 3 to 4 dB using C-band radar. The timing of ice formation and melt on lakes and rivers has successfully been determined from space-borne SAR data. The study site is located in the southern central part of the Lena River Delta, Northern Siberia, Russia, at 72°N, 126°E. The area is a polygonal arctic tundra landscape, located in a zone of continuous permafrost and covered by ponds, lakes (15 m2 to 1.3 km2) and river arms. A time series of twelve TerraSAR-X images (Stripmap mode) and six RADARSAT-2 (Fine quad-pol) images acquired during spring 2011 and nine RADARSAT-2 images recorded during fall 2011 were analyzed for this study. The dates of snow-melt, lake- and river-ice decay and onset, and soil thaw / refreeze obtained from the SAR-based study were compared to meteorological data from Samoylov Island, located in the investigation area, and Tiksi, located about 110 km southeast of the study site. Soil thaw and refreeze was investigated in regions with different soil properties and vegetation cover. Temporal variations of the mean backscattered radar intensity were analyzed for the different land units. The results show that snow-melt events are clearly displayed in the mean backscatter values of the ROIs within the time series. The thaw of the active layer could not be observed in the X-band data, in which the mean backscatter values are mainly the same for both, the frozen and the thawed landscape. The backscatter values of the C-band data are about 3 dB higher during the thaw period than during the freezing period, and vice versa for the refreeze of the soils. Lake- and river-ice decay and refreeze was monitored in the frame of this study as well. Ice-decay could be observed in both, the TerraSAR-X and the RADARSAT-2 data. ... |
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