Permafrost conditions along the Dempster Highway, Peel Plateau Region, Northwest Territories
The road wound steadily north as our SUV passed through snowy mountains under a cloudless March sky. Once again, my colleague Jeff Moore and I were driving the Dempster Highway to conduct snow surveys for my Ph.D. research on permafrost conditions west of Fort McPherson, NT.
The Dempster Highway is Canada’s only all-season road that crosses the Arctic Circle. The highway begins just east of Dawson City, Yukon and extends 736 km to Inuvik. Officially opened in 1979, the road is a critical transportation route accessing communities in the Mackenzie Delta region. Recently, the road has gained importance because Inuvik now relies on tanker loads of propane for power generation. In addition, construction of the Inuvik to Tuktoyaktuk Highway is extending the Dempster Highway corridor northward and will link southern Canada to the Beaufort Sea coast.
Most of my research sites are on Peel Plateau, a rolling landscape between Richardson Mountains and Peel River, NT. The plateau is just within the limit of the late-Wisconsinan glaciation. As a result, the ground in the region contains buried glacial ice, preserved in permafrost. In many locations, huge thaw slumps have developed where this massive ice has become exposed. Permafrost temperatures on Peel Plateau are relatively high, partly because of strong winter air temperature inversions. The combination of ice-rich and warm permafrost means that the region is susceptible to disturbances that affect the ground thermal regime.
The road on which we trundled was itself the focus of our field trip in March. Roads in permafrost are built on embankments, raised berms that protect the permafrost from thaw and prevent ground subsidence. However, the embankment also acts as a windbreak, causing snow to accumulate. Snow cover is an effective insulator, so an increase in snow depth serves to warm permafrost. The portion of the highway on Peel Plateau has required significant maintenance in response to permafrost-related problems, and has recently been rehabilitated at a cost of $65M. Part of my research aims to investigate the thermal disturbance to permafrost from the road embankment. To accomplish this, I installed numerous instruments that record ground temperatures at the embankment toe in 2012, and in undisturbed settings. I have also conducted detailed snow surveys at the sites each spring since their installation.
My results indicate that increased snow cover at the embankment toe is causing the active layer (the ground on top of permafrost that thaws each summer) to increase significantly in thickness, degrading permafrost. These findings help explain the recent maintenance challenges along the embankment on Peel Plateau associated with ground subsidence.
I find this research interesting because it is relevant to the lives of northerners and may be helpful in informing maintenance of this important highway. As a next step, I will explore the effects of reducing or removing snow on ground temperatures using numerical simulations. This August, I will again enjoy driving the scenic Dempster to collect additional data, and, if I’m lucky, taking in a show or two of the aurora borealis.
Brendan O’Neill is a Ph.D. student at Carleton University in the Department of Geography and Environmental Studies, currently studying permafrost science. His research project is a part of a broader Northwest Territories Cumulative Impacts Monitoring Program study, a community-guided research effort to understand changes to the terrestrial and aquatic ecosystems of the Peel Plateau region.
Views expressed in blog posts reflect those of the author, and not necessarily those of the CFES.