Monitoring Ground Temperatures in Permafrost along the Dempster Highway, Yukon and NWT: Fid-Bau Portal

Monitoring Ground Temperatures in Permafrost along the Dempster Highway, Yukon and NWT

Stockton, E. J. / Burn, C. R. / Idrees, M. / Calmels, F. / Elmer, K.

The Dempster Highway is the only all-season road connecting Canada’s western Arctic to the national highway network. Completed in 1979 it is built almost entirely on permafrost. Climate changes and infrastructure effects are expected to increase the temperature of permafrost near and beneath the road, resulting in increased active-layer thickness (ALT), drainage disruptions, and embankment subsidence. Four monitoring sites were established in 2014 to study such effects. Ground temperatures have been recorded along the highway at km 124 and 421 in Yukon and km 8.5 and 51.5 in NWT. Three boreholes up to 10 m depth were drilled at each site, to measure permafrost conditions at the highway centerline, embankment toe, and in undisturbed ground. The annual mean temperature at the top of permafrost (T_p) has been lowest beneath the centerline at each site (-1.5°C to -4.2°C), with the index decreasing northward. The active layer has thickened at each site, with only the centerline at km 124 in equilibrium. Ground temperatures at the centerline have fluctuated in response to changing air temperatures throughout the year due to clearing of snow from the highway. Degradation of permafrost at the toe has been the result of increased snow cover from ploughing and additional drifting. Thaw depths at the centerline of the NWT sites indicate permafrost initially aggraded within the embankment. The difference between T_p at the centerline and annual mean air temperature has decreased northwards, from 4.5°C at km 124 to 1.0°C at km 51.5; due to shorter freezeback periods at the NWT sites. The four years of measurements provide a baseline against which future changes may be assessed.