Spatial variability of permafrost active-layer thickness under contemporary and projected climate in Northern Alaska

The active layer plays an important role in the functioning of environmental ecosystems and affects many human activities in the polar regions. Regional assessments and predictions of this parameter are critical for many physical and social applications. Large heterogeneityin near-surface permafrost characteristics, including the active layer, even over small distances, creates serious constraints to their evaluation across large geographic extents. Discrepancies between modeled climatic fields add to the uncertainties associated with predicting active-layer thickness (ALT) at regional scales. This study uses a stochastic approach, in combination with an equilibrium permafrost model, to map the geographic distribution of ALT and near-surface permafrost temperature on the North Slope of Alaska. GIS techniques are used to determine the spatial variability of ecosystem factors controlling the ground thermal regime within each grid cell of the permafrost model. To incorporate the uncertainty associated with the climate data, the model was forced by four sets of gridded air temperature fields used widelyin spatial modeling applications. A series of calculations created a spectrum of possible solutions for ALT and associated probability ranges for each grid cell. Results are presented as a series of maps depicting geographic patterns of contemporaryand future ALT for the North Slope of Alaska.