Counting the cost of climate change along the Dempster Highway
Dr Chris Burn
Chancellor's Professor of Geography
The Dempster Highway is the only all-season road to Canada’s Arctic. It extends for 736 km from near Dawson, YK (64° 2’ N), to Inuvik, NWT (68° 18’ N). About 90% of the route is on continuous permafrost. The road crosses two glacial limits in the alpine terrain of southern Ogilvie Mountains and the Laurentide limit on the eastern side of Richardson Mountains. For 450 km the highway traverses unglaciated terrain. The route also traverses the tree line, passing through Arctic and alpine tundra. The climatic gradient from Dawson (MAAT -4.1 °C) to Inuvik (-8.2 °C) is complicated by effects of winter inversions in the dissected terrain of Oglivie Mountains and at the eastern approach to Richardson Mountains on Peel Plateau. Permafrost conditions are more consistent, with mean ground temperatures varying between -2 and -3 °C beneath forest/taiga or tundra.
Climate is changing relatively rapidly throughout the region. Since 1970, annual mean air temperatures have risen by 0.77 °C/decade at Inuvik, where eight of the last 15 years’ rainfall lie in the highest 15 totals recorded. The response of the highway embankment to increasing ground temperature is greatest in glaciated terrain, where relict glacier ice is preserved. When this thaws, remediation is continuous and expensive.
Much of the documented warming of ground near the highway is due to increases to the snow cover caused by the embankment obstructing surface air flow over tundra. The response to increasing precipitation is greatest in the unglaciated mountains, requiring repair of washouts in summer and more frequent management of icings in winter. The costs currently are approximately $1M per km in glaciated terrain and have been incrementally $400k/yr in the mountains since 2005. For the Yukon, the rising expense represents an annualized 5% increase in the cost of operating the road. Climate-related maintenance accounts now over 40% of highway maintenance expenses for the 465 km in Yukon. In the short term, it is possible to mitigate thaw of permafrost by managing snow accumulation, but it is difficult to manage changes in the precipitation regime without significant capital investment.
Dr Chris Burn has been studying permafrost in Yukon and the western Arctic since 1982. His work is principally concerned with the response of permafrost terrain to disturbances, either due to changes in surface conditions or to climate. He spent over 25 years working in the Mackenzie Delta area with J. Ross Mackay (1916-2014), Canada's leading authority on permafrost and ground ice. Ten of Chris's former graduate students work in the NWT, and three others in Yukon. His research program has been supported for many years by the Natural Sciences and Engineering Research Council, the Polar Continental Shelf Project, and the Aurora Research Institute. More recently he has been collaborating with the Transportation Engineering Branch, Yukon Government, on studies of permafrost conditions along the Dempster Highway. Chris has particularly enjoyed working with consulting engineers, especially Don Hayley, formerly of EBA, on the Dempster Highway and Wayne Savigny of BGC on the Mackenzie Gas Project.
Public Lecture Sponsored by Northwest Territories and Nunavut Association of Professional Engineers and Geoscientists (NAPEG).