Environmental controls on ground temperature and permafrost in Labrador, northeast Canada

Field data from 83 environmental monitoring stations across Labrador, 17 with permafrost, were used to analyze the interrelationships of key variables considered in the temperature at the top of permafrost model. Snow depth, not mean annual air temperature, was the strongest climatic determinant of mean temperatures at the ground surface and at the base of the annual freeze-thaw layer, and its variability was most closely related to land cover class. A critical late-winter snow depth of 70 cm or more was inferred to be sufficient to prevent the formation of permafrost at the monitoring sites, which meant that permafrost was absent beneath forest but present in some tundra, peatland and bedrock locations. Analyses showed no statistically significant relations identified between topographic indices and various station parameters, challenging their utility for regional modeling. Testing of several different land cover datasets for model parameterization gave errors in ground surface temperature ranging from +/- 0.9 to 2.1 degrees C. These results highlight the importance of local field data and emphasize the necessity of high-quality national-scale land cover datasets suitable for permafrost modeling.