Surficial characteristics associated with the occurrence of permafrost near Mayo, Central Yukon Territory, Canada

Key criteria have been isolated for predicting the location of discontinuous permafrost in central Yukon Territory. Eighteen soil, vegetation, and topographic variables were documented at 60 sites in a 2500 km2 area, and analysed to establish their association with the occurrence of permafrost. The singular features most associated with permafrost were a thick surface organic layer and a hummocky microtopography. In combination, soil moisture content and organic‐layer thickness were diagnostic of permafrost occurrence. The thickness of the organic layer, a horizon of low thermal diffusivity, governs attenuation of the summer temperature wave; soil moisture content supplies water for evapotranspiration, which reduces surface temperature. Variation in these indices accounted for 95% of variation in permafrost occurrence within the 60 sites. A diagnostic system to predict permafrost occurrence was constructed with these indices, and tested against field data from 60 different sites. The occurrence of permafrost in the second data set was predicted correctly at every site. The critical soil moisture content and organic‐layer thickness were 25% (gravimetric) and 11 cm, repectively. Permafrost is present where these values are exceeded. The results indicate that the occurrence of permafrost in this portion of the discontinuous zone can be determined from relatively few variables.