A Physical Model of Permafrost Sorted Stripe Formation in the Canadian High Arctic

Hillslopes in the Canadian High Arctic can express curious quasi-linear sorted stripe patterns, physically resembling rills but with no obvious evidence of active particle transport via sustained surface water flows following rainfall or snowmelt. This motivates several questions which at present are little explored. First, how do the physical characteristics of the pattern vary down the hillslope in response to changing hillslope geomorphology (e.g. slope, elevation, etc.)? Second, what mechanism(s) causes sorted stripe patterns to initiate and develop, and what are the roles of freeze-thaw, granular, and fluid-flow-driven processes? Several attempts have been made to model the formation of sorted stripe patterns using rules-based approaches, or analytical models derived from these rules; however, a comprehensive physical model of sorted stripe formation has yet to be developed, and we currently lack even a characterization of how the pattern is distributed across a hillslope.

Here, we present a characterization of the sorted stripe patterning found on a hillslope on Tallurutit (Devon Island), Nunavut and examine topographic controls of hillslope track characteristics. By analyzing topographic lidar data, we find that there is not one preferred cross- or downslope spacing of the stripes; rather, the size and shape of stripes varies down the hillslope. This alludes to the idea that there are several processes at work to form hillslope sorted stripe patterns. We present a physical model of stripe formation involving initial fracturing of the hill due to thermal stresses, heaving from ice lens growth, and mobilization of stones due to the creation of critically-steep topographic gradients and ice needle formation. We motivate this model using the characterization of the sorted stripe pattern distribution, field observations, and an analysis of thermal and tensional stresses.