Researchers in Northwest Territories Geoscience Office, Natural Resources Canada, and others6,8 contribute significant data and information to the understanding of ground thermal regimes in the NWT.
Natural Resources Canada compiles ground temperature data from across the Canadian North; these and other data can be found on the National Snow and Ice Data Centre11. Ground temperature information from the Mackenzie Delta region is also available at the Northwest Territories Geoscience Office.
|Ground temperature: The monitoring program should determine the depth and frequency of ground temperature collection. Studies investigating the influence of snow, vegetation or disturbances on soil conditions may monitor temperaturs near the ground surface. Long-term tracking of changes in ground temperatures should focus on temperatures at a depth where there is no variation with seasons. A change in temperature at this depth indicates a shift in the ground thermal regime.|
Knowledge of ground temperatures in permafrost zones is required for the design of northern infrastructure, assessing environmental impacts of development, and planning mitigations. It is also important to understand how ongoing climate warming is impacting permafrost temperatures because the thermal state of frozen ground is closely linked to its physical stability and ecosystem integrity13.
Increasing air temperatures, changes in vegetation, or increased snow cover can cause permafrost temperatures to increase and, increasingly, to thaw. Since the relationships between air and ground temperature are influenced by other factors such as snow, vegetation and soil moisture, it is important to take a holistic monitoring approach. This requires collection of complementary field data so that factors driving changes in the thermal state of permafrost can be understood.
Current view: status and trend
In general, mean annual ground temperatures decrease and the thickness and aerial extent of permafrost increases poleward. Mean annual ground temperatures in tundra environments of northern NWT are below -6oC9, and permafrost may be several hundreds of metres thick4. The transition from continuous to discontinuous permafrost roughly coincides with the position of the subarctic boreal-tundra transition.
Permafrost temperatures across the NWT are increasing in response to current climate warming12. In the Mackenzie Delta region, ground temperatures have warmed in some areas by as much as 2oC since the early 1970s. Burn and Kokelj2 redraw a map of ground temperatures in the delta region by Mackay8 with data from over 60 contemporary sites.
Near-surface ground temperatures in the late 1960s and early 1970s in the Mackenzie Delta area after Mackay8.
Near-surface ground temperatures measured between 2003 and 2007, Mackenzie Delta area. Figure 11 from Burn and Kokelj2 (Reproduced with permission from John Wiley & sons, Ltd., Permafrost and Periglacial Processes).
Current research indicates that the cumulative impacts of disturbance or ecological change will compound the impacts of climate warming on the thermal stability of permafrost. Disturbance of the forest cover in the southern discontinuous permafrost zones of NWT can sufficiently alter the surface energy balance to stimulate the degradation of permafrost under contemporary climate conditions3. Thermal modelling has shown that the majority of permafrost warming at abandoned oil and gas infrastructure in the western Arctic can be attributed to the proliferation of tall shrubs and snow accumulation, rather than due to rising air temperatures10. This study also illustrates that shrubbier tundra and enhanced snow cover will likely accelerate the warming of permafrost anticipated with climate change.
It is anticipated that ground temperatures will continue to increase with future warming, but regional changes in vegetation or snow cover, or proximity of sites to water, may either enhance or slow the ground warming5. The rate of ground warming typically slows as temperatures approach 0oC because of the large amounts of heat that must be removed from the ground as the ice in soils is converted to water9 (Figure 3 above).
Planning and managing development of northern infrastructure and understanding environmental responses to climate warming require information on permafrost temperatures. As snow cover, vegetation and soil organic cover all influence the ground thermal regime in addition to air temperatures; measurement of these parameters should complement a thermal monitoring program.
Warming of permafrost is being reported in Alaska9. Some recent modelling projections of permafrost degradation7 probably overestimate the rates and magnitude of future thawing1, but both empirical and modeling evidence suggest that over the next several decades continued climate warming will cause permafrost to warm, and in some areas such as with the discontinuous permafrost zone, to thaw entirely14.
- Natural Resources Canada compiles ground temperature data from across the Canadian North.
Other focal points
- For more indicators related to landscape, see the Focal Point LANDSCAPE CHANGES.
Found an error or have a question? Contact the team at NWTSOER@gov.nt.ca.
Ref. 1. Burn, C.R., and F.E. Nelson. 2006. Comment on ''A projection of severe near-surface permafrost degradation during the 21st century'' by Lawrence, D.M. and Andrew G. Slater, A.G., Geophysical Research Letters 33: L21503.
Ref. 2. Burn C.R. and S.V. Kokelj. 2009. The environment and permafrost of the Mackenzie Delta area. Permafrost and Periglacial Processes 20: 83-105.
Ref. 3 Grosse, G., J. Harden, M. Turetsky, D. McGuire, P. Camil, C. Tarnocai, S. Frolking, E. Schuur, T. Jorgenson, S. Marchenko, V. Romanovsky K. Wickland, N. French, M. Waldrop, L. Bourgeau-Chavez, and R. Striegl. 2011. Vulnerability of high-latitude soil organic carbon in North America to disturbance Journal of Geophysical Research: Biogeosciences 116: 23 p.
Ref. 4. Heginbottom, J.A., M.A. Dubreuil, and P.T. Harker. 1995. Canada: Permafrost. National Atlas of Canada Fifth Edition. Natural Resources Canada, MCR 4177.
Ref. 5. Kanigan J.C.N., C.R. Burn, and S.V. Kokelj. 2008. Permafrost response to climate warming south of treeline, Mackenzie Delta, Northwest Territories, Canada. In: Proceedings of the Ninth International Conference on Permafrost (Vol 1). D.L. Kane and K.M. Hinkel, Eds. Institute of Northern Engineering, University of Alaska at Fairbanks: Fairbanks, Alaska, pp. 901-906.
Ref. 6. Karunaratne, K.C., S.V. Kokelj, and C.R. Burn. 2008. Near-Surface Permafrost Conditions near Yellowknife, Northwest Territories, Canada. In: Proceedings of the Ninth International Conference on Permafrost (Vol 1). D.L. Kane and K.M. Hinkel, Eds. Institute of Northern Engineering, University of Alaska at Fairbanks: Fairbanks, Alaska, pp. 907-912.
Ref. 7. Lawrence, D.M. and A.G. Slater. 2005. A projection of severe nearsurface permafrost degradation during the 21st century. Geophysical Research Letters 32: L24401.
Ref. 8. Mackay, J.R. 1974. Seismic shot holes and ground temperatures, Mackenzie Delta area, Northwest Territories. Report of activities, part A. Geological Survey of Canada, Paper 74-1A, pp. 389-390.
Ref. 9. Osterkamp, T.E. and V.E. Romanovsky. 1999. Evidence for warming and thawing of discontinuous permafrost in Alaska. Permafrost Periglacial Processes 10: 17-37.
Ref. 10. Short, N., C.W. Stevens, and S.A. Wolfe. 2011. Seasonal Surface Displacement Derived from InSAR, Yellowknife and Surrounding Area, Northwest Territories, Canada. GSC Open File 7030. 1 CD-ROM.
Ref. 11. Smith S.L., V.E. Romanovsky, A.G. Lewkowicz, C.R. Burn, M. Allard, G.D. Clow, K. Yoshikawa, and J. Throop. 2010. Thermal state of permafrost in North America - a contribution to the International Polar Year; Permafrost and Periglacial Processes 21: 117-135.
Ref. 12. Smith S.L., M.M. Burgess, D. Riseborough, and F.M. Nixon. 2005. Recent trends from Canadian Permafrost Thermal Monitoring Network Sites. Permafrost and Periglacial Processes 16: 19-30.
Ref. 13. Thompson, M.S., S.V. Kokelj, T.D. Prowse, and F.J. Wrona. 2008. The impact of sediments derived from thawing permafrost on tundra lake water chemistry: An experimental approach. 2008. In: Proceedings of the Ninth International Conference on Permafrost (Vol 1). D.L. Kane and K.M. Hinkel, Eds. Institute of Northern Engineering, University of Alaska at Fairbanks: Fairbanks, Alaska, pp. 1763-1768.
Ref. 14. Zhang, Y., I. Olthof, R. Fraser, and S.A. Wolfe. 2014. A new approach to mapping permafrost and change by incorporating uncertainties in ground conditions and climate projections. The Cryosphere 8: 1895-1935.