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¹³⁷Cs has been used in soil science for many years but, to the author's knowledge, this thesis is the first attempt to use it in connection with soil deformation within patterned ground. The main objectives are to describe and analyze the morphometry, sedimentary structure and composition in non-sorted patterned ground in a sub-Arctic mountain permafrost environment. Second, the application of ¹³⁷Cs isotopes as a tracer of soil deformation patterns is tested, in order to discuss possible mechanisms responsible for soil deformation, internal structure and ¹³⁷Cs re-distribution. To achieve this, field work was conducted in the beginning of August 2005 on Mt. Låktatjåkka, situated north-west of the village of Abisko in northern Sweden, and was followed by laboratory analysis. The field work included non-sorted stripe width- and moisture measurements together with soil sampling and excavation of a soil cross- section. One-year ground temperature data from I-buttons were retrieved and frost heave and downslope displacement on the summit was measured. The laboratory analysis included soil moisture content calculations and sieving. The fraction <212μm was used for ¹³⁷Cs analysis.

The summit of Mt. Låktatjåkka is very sparsely vegetated, bare ground and blocky areas with rocky outcrops dominate the area. The non-sorted stripes consist of a bare, domed part and a lower lying, vegetated furrow. Surface cracking, steep furrow boundaries and bare domed surfaces indicate the stripes to be active landforms. The bare parts are generally wider and display a wider width range than the furrows. No changes in width or width ratios appear associated with changes in slope angle or orientation. The excavated stripe cross-section display a striking updoming, with the upward motion centred under the stripes bare sections. The ground temperature record indicates a thin snow cover on the Låktatjåkka summit during winter, and that the furrows respond slower to temperature changes than the bare domes. The difference in response time is due to higher water content and the accumulation of snow in the furrows. Conflicting non-sorted stripe soil moisture values result from different measuring techniques.

The results from the stratigraphic analysis and ¹³⁷Cs distribution show that a soil separation process is taking place within the non-sorted stripes. Coarser soil material is being moved upwards towards the ground surface and finer material is being forced downwards into the stripe profile. The ¹³⁷Cs distribution also indicates an additional mode of transport for the radionuclide, apart from the soil deformation responsible for the formation of the patterned ground. The bulk of the ¹³⁷Cs is concentrated at the groundwater table. This is a region with high rainfall and coarse-grained soils with low clay- and organic content, so the most likely transporting agent is percolating water. From the ¹³⁷Cs distribution is also indicated an upward mobility of ¹³⁷Cs from the groundwater table, roughly within each stripe dome. The lack of statistical correlation between ¹³⁷Cs and grain size and between ¹³⁷Cs and soil moisture for the non-sorted stripes suggests that the ¹³⁷Cs has been re-distributed independent of grain size and soil moisture.

Evidence supports the theory that the movement in the soil is caused by buoyancy induced soil convection. The fact that ¹³⁷Cs could give independent information about soil deformation patterns indicates that the radionuclide is a valuable tool in patterned ground studies.