Abramova, Ekateriana N.

Kutzbach, Lars

Schneider, Waldemar

OceanRep

The Expedition LENA 2002 3 Ecoloaical studies on permafrost soils and !andscapes 3.4 Seasonal progression of thaw depth dependent On mircrorelief Lars Kutzbach. Ekafarina N. Abramova and Waldemar Schneider 3.4.1 Background The topography of the Lena Delta is fairly flat, but well-structured by a prominent microrelief, caused by the development of ice-wedge polygons. Most common are low-centred polygons. The depressed centres of these polygons are surrounded by elevated rims, which are situated above the ice-wedges. The prominent microrelief causes a high spatial heterogeneity of soil properties on the small scale of decimeters to meters. In order to up-scale results of process studies to the landscape scale, it is necessary to describe and quantify the spatial hetorogeneity of soils. A major factor for all physical and biological processes in permafrost soils is the active layer depth (=thaw depth). 3.4.2 Projects A thaw depth monitoring Programm was conducted on Samoylov Island in the period June 10 - August 30. An investigation site of 28 m X 18 m was established close to the new soil survey station (Chapter 3.2, Figure 3.12). A grid of 150 measurement points in intervals of 2 m X 2 m were marked and mapped with a laser tachymeter (type Trimble 3300). At every measurement point, thaw depth was measured every 3 to 7 days by driving a steel rod into the unfrozen soil until the hard frozen sediments were encountered. 3.4.3 First results Contour maps of the microrelief at the thaw-depth monitoring site and the spatial variability of the mean thaw velocity during the study period are shown in Figures 3-31 and Figure 3-32. 3 Ecoloaical studies on oerrnafrost soils and iandscaoes The Exoedition LENA 2002 Figure 3-31. Contour map of the microrelief at the thaw-depth monitoring site, ~ Ã ¤ m o ~ l o  Island. Units of th'e coordinate system are meters. Figure 3-32. Mean thaw velocity during the study period June 10 - August 30 at the thaw depth monitoring site, Samoylov Island. The contour lines of the microrelief (Figure 3-31) are indicated for orientation. 

Seasonal progression of thaw depth depended on microrelief

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