SOME OBSERVATIONS ON THE INFLUENCE OF CLIMATIC AND TERRAIN FEATURES ON PERMAFROST AT NORMAN WELLS, N.W.T., CANADA

Abstract

During the summers of 1959 and 1960, field observations of the influence of some climatic and terrain features on permafrost were carried out at Norman Wells, N.W.T. Five sites, all underlain by perennially frozen ground, were selected for investigation. One site was a Thornthwaite potential evapotranspiration site with a vegetation cover of Kentucky bluegrass growing on clayey silt. The four remaining sites included the various types of vegetation growing naturally in the Norman Wells region. The tree growth was predominantly spruce with some tamarack. Sphagnum and other mosses, lichen, and sedge comprised the ground cover. The peat layer varied in thickness from 7 in. to 2 ft and the mineral soil was predominantly clayey silt. At each site, measurements were taken of evaporation (including potential evapotranspiration), net radiation at the ground surface, depth of thaw, and ground temperatures in the thawed layer and the permafrost. Although field conditions dictated the use of crude measuring devices, some quantitative information was obtained on the relative importance of these climatic and terrain features in the permafrost environment. Potential evapotranspiration was higher in the Kentucky bluegrass at the Thornthwaite site than in Sphagnum and in other mosses, in lichen, and in sedge at the other sites. Net radiation values appeared to be slightly higher for moss than for lichen. The depth of thaw under moss and lichen was less than in areas supporting other types of plant growth. Ground temperatures in the thawed layer and in the permafrost showed the same characteristics, being lower in the moss and lichen areas.