Practical limits to mapping the active layer: A geostatistical evaluation of frost table probe and remote sensing data

Detailed active layer measurements were made on Richards Island, Northwest Territories with two main objectives: (1) to understand relations between the active layer depth and surface temperature, surface cover, macro- and micro-topography, and snow depth; (2) to quantify the spatial variability of the active layer and related phenomena in order to assess the utility of various measuring approaches including frost table probe, ground probing radar, aerial photography, and satellite imagery. The depth of active layer exhibits very high spatial variability due to thermal properties of the ground materials, microtopography, and surface cover. According to the results, accurate mapping of the active layer in areas of continuous permafrost requires sampling intervals that make it impractical to map large areas. Geostatistics, and semivariograms in particular, are valuable for estimating the spatial variability of natural phenomena, and may be used to design efficient and effective sampling schemes.