Derivation of Environmental Parameters of Arctic Tundra Landscapes with SAR
Climate warming twice as large as the global average has been observed in the Arctic. In regions underlain by permafrost, the warming leads to changes in the timing of snowmelt and active layer thaw onset towards earlier dates in the year and later dates for the refreeze in fall. This results in lar...
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| Format: | Thesis |
| Language: | unknown |
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Westfälische Wilhelms-Universität Münster
2012
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| Online Access: | https://epic.awi.de/id/eprint/33332/ https://hdl.handle.net/10013/epic.42111 |
| Summary: | Climate warming twice as large as the global average has been observed in the Arctic. In regions underlain by permafrost, the warming leads to changes in the timing of snowmelt and active layer thaw onset towards earlier dates in the year and later dates for the refreeze in fall. This results in larger active layer depth, which in turn results in changes of the hydrology and vegetation cover. Lakes and rivers show earlier ice-off and later refreeze dates. Remote sensing is a valuable tool to observe the state of the surface in near real time. Sensors operating with microwaves are especially eligible, as the are - in contrast to optical sensors - able to penetrate clouds and to work independent of sunlight. Synthetic Aperture Radars (SAR) are active microwave systems, which send a pulse to the earth and then record the backscattered energy. SAR systems can operate at different frequencies and send and receive the pulses either in horizontal (H) or vertical (V) polarizations. The purpose of this work was to validate the potential of imaging radar to derive environmental parameters in Arctic tundra landscapes at the example of the Lena River Delta in northern Siberia. The area is composed of three different tundra ecosystems and characterized by a high amount of lakes and river channels. A time-series of 12 HH-polarized TerraSAR-X (9.65 GHz) and 20 quad-polarized RADARSAT-2 (5.405 GHz) images, acquired from April to November 2011, were available for this study. During an expedition to the Lena Delta in summer 2010, extensive mapping of the vegetation and the moisture of the top soil layer was performed. Four automatic weather stations (AWS) were set up to record the climate conditions in the Lena Delta all year round. This field data were used to support the analyses of the SAR images. With regard to the observed warming of the Arctic, the study concentrated on the detection of the shifts of the thermal state (thaw and refreeze) of the soils and the water bodies as well as the timing of the snowmelt and the ... |
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