Analytic representation of the active layer thickness field, Kuparuk River Basin, Alaska

Abstract

The initial response of permafrost to global warming could be an increase in active-layer thickness. Given that such changes could have severe consequences for human infrastructure and ecosystem stability, it is important to obtain information about spatial variations of the active layer corresponding to current climatic conditions, and to determine the magnitude of possible near-surface permafrost degradation associated with climatic change. Simple analytical solutions for frost and thaw penetration depth have long been available, but were used primarily for practical applications at point locations in cold-region engineering. One of these methods, developed at Moscow State University by Kudryavtsev and co-workers, was used to develop a spatially distributed analytic model that estimates the maximum annual depth of thaw. Kudryavtsev’s procedures account for the effects of snow cover, vegetation, soil moisture, thermal properties, and regional climate, and provide estimates of surface temperature and active-layer thickness. GIS techniques were used to incorporate climate records, digital cartographic products, and field data into a spatially distributed estimate of active-layer thickness. Procedures were applied over a rectangular 22 300 km 2 area in north-central Alaska containing complex patterns of topography, vegetation, and soils. Validation procedures indicate that the Kudrayavtsev solution, adapted for spatial applications, yields accuracy and spatial resolution comparable to an existing semi-empirical method. The simplicity and low data requirements of the Kudryavtsev solution make it readily adaptable to different geographic scales and areas. The method has potential applications in climate-change studies.