Permafrost Distribution in Central Canada: Applications of a Climate-Based Predictive Model

A revised permafrost index, computed from mean monthly air temperatures and snowcover data, produces an unambiguous latitudinal zonation of contemporary permafrost. Isarithmic mapping of this “surface frost number'’defines a latitudinal zonation that is in substantial agreement with a previous semi-empirical mapping of permafrost in the lowlands of central Canada. A related index, the “Stefan frost number,'’employs estimates of soil properties in an approximate engineering solution for the depths of freezing and thawing. Mapping of this index by unclassed choropleth methods provides an estimate of point-to-point variations in permafrost distribution under the assumptions of homogeneous topography and vegetation. The model successfully predicts the presence of permafrost in peatlands outside the zonal limits defined by climatic criteria alone. The frost number provides an easily computed, physically based method for predicting permafrost that lends itself to a variety of cartographic representations of permafrost distribution.