Topoclimatic influences on active-layer thickness, northern Alaska
Date
2011
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Publisher
University of Delaware
Abstract
Although many studies of active layer development address spatial variations in soil thermal properties and moisture conditions, few have attempted to isolate topoclimatic influences over thaw depth. The n-factor, the ratio of ground surface to air degree-day sums, is widely used in conjunction with analytic solutions for thaw depth in geotechnical work. In an analogous manner, the ratio of potential radiation received on a slope to that incident on a horizontal surface at the same latitude can be incorporated into formulations such as the Berggren or Stefan equations. Observed patterns of thaw depth on various facets of an anthropogenic thermokarst landform near Prudhoe Bay, Alaska show systematic variation with slope aspect. Use of the .r-factor. with the Berggren solution accurately reproduces these patterns, demonstrating the importance of differential radiation loading, even in high-latitude regions. Thaw depths measured on hillslopes facing the cardinal directions at Happy Valley, Alaska, did not strongly correlate with elevation, slope curvature, or soil moisture. Active-layer thickness varies as a function of the interactions of many environmental factors, and the complexity of the system may require testing of other contributing factors that were not included in this study, specifically, air and soil temperature, rainfall, snow cover, vegetation, and the influence of water tracks.
Description
Keywords
Permafrost, Topoclimate, Active-layer thickness