NWT State of the Environment Report

13. State Permafrost

Le rapport sur l’état de l’environnement 2022 est un document technique destiné à un usage interne. Il n’est disponible qu’en anglais.

Introduction 

Permafrost is the frozen ground that underlies terrain throughout the Northwest Territories' sub-Arctic, Arctic and mountainous regions (Figure 1). It is the cement that holds permafrost landscapes together, providing the foundation for northern ecosystems, communities and roads, and it is an important component of the northern environment. Permafrost is closely linked to climate, such that warming air temperatures have profound effects on its thermal and physical properties and its distribution (Ref 1; Ref 2; Ref 3). Climate-driven permafrost thaw is already having major consequences on northern infrastructure (Ref 4), geomorphology (Ref 5; Ref 6; Ref 7) biogeochemistry (Ref 8) and carbon cycling (Ref 9) and impacting terrestrial and aquatic systems (Ref 10). The following document explains permafrost and its relevance to the Northwest Territories environment and summarizes several indicators that describe the characteristics and state of permafrost, and which may be monitored through time.

The Northwest Territories reside within the zones of continuous, discontinuous, and sporadic discontinuous permafrost and the majority of NWT communities are affected by permafrost (Figure 1) (Ref 11). The extent of permafrost increases northward with a decrease in mean annual air temperatures. In Arctic tundra regions, permafrost underlies almost all of the land area. The Yellowknife region is within the extensive discontinuous permafrost zone, where 50 to 90% of the land is underlain by frozen ground. In contrast, Hay River on the southern side of Great Slave Lake is in the sporadic discontinuous zone where only 10 to 50% of the land is underlain by permafrost. Further south, permafrost persists in patches of organic soils to comprise less than 10% of the land area (Ref 12). An extensive area of subsea permafrost on the western Arctic continental shelf also developed during the middle to late Quaternary, when sea levels were lower, and sediments were exposed to frigid air temperatures (Ref 13). The current and future permafrost conditions are key considerations in the planning and management of virtually all infrastructure in the NWT.

The temperature and thickness of permafrost varies across the NWT with climate, vegetation cover and geology (Ref 14). The transition from continuous to discontinuous permafrost roughly coincides with the position of subarctic boreal-tundra transition, south of which permafrost generally occupies between 65 and 90 % of the landscape. In the southern NWT, permafrost is classified as sporadic discontinuous, where thin lenses of frozen ground persist in peatlands at temperatures just below 0 oC (Ref 15).

 

Permafrost: Rock or soil that remains below 0°C for at least two consecutive years. Surface conditions including vegetation, organic cover and snow thickness influence permafrost temperatures. Permafrost thickness is related to the air temperature, soil properties and the geothermal gradient as well as the environmental history of the area.

Active layer: Surface layer of earth materials within permafrost terrain that thaws and refreezes each year.

Ice-rich permafrost: Ground-ice content greater than the saturated moisture content of thawed soil is called “excess ice”. Types of excess ground ice include relict ice, segregated ice and wedge ice. Terrain features such as tundra polygons, thaw-slumps and pingos indicate ice-rich permafrost.

Thermokarst: Terrain that forms as ground subsides due to thawing of ice-rich permafrost. Thermokarst processes may cause lakes to enlarge, peatlands to collapse and landslides or thaw slumps to develop.

Retrogressive thaw slumps: Develop due to thawing of ice-rich permafrost on slopes. Thawing turns exposed ice-rich permafrost into a mud slurry which collapses to the base of the exposure and flows downslope. Warming has caused the abundance and size of slumps to increase in parts of NWT.

Figure 1. Map of permafrost distribution for Northwest Territories adapted from Heginbottom JA, Dubreuil MA, Harker PA. 1995. Canada — permafrost, National Atlas of Canada, 5th edition. National Atlas Information Service, Natural Resources Canada, Ottawa. MCR 4177

 

The type and amounts of ice within permafrost determine the environmental and geotechnical implications of thawing. Much of the permafrost across the NWT is regarded as thaw-sensitive due to the large volumes of ground ice it hosts (Figure 2) (Ref 16). The types and amounts of ground ice in permafrost reflect a complex interaction between geological legacy and the landscape's geomorphic, climatic, and ecologic history. Ground ice in permafrost gives rise to unique landforms such as pingos (Ref 18), polygonal ground (Ref 19), peat plateaus (Ref 20) and lithalsas (Ref 21). A zone of near-surface ice enrichment immediately beneath the base of the active layer is ubiquitous in fine-grained sediments throughout the western Arctic, Mackenzie Valley and parts of the North Slave region (Ref 22; Ref 23), and thus, the terrain is sensitive to disturbances that would cause the active layer to increase in thickness such as forest fire or climate warming (Ref 24). Ice-wedges underlie polygonal terrain and are another common form of ground ice in the tundra (Figure 3a) (Ref 19). Extensive bodies of massive ground ice several metres thickness occur in glacial deposits such as moraines and eskers (Figure 3b) (Ref 22; Ref: 25; Ref 26).

 

Figure 2. Ground ice abundance represents a first-order estimate of the combined volumetric percentage of excess ice in the top 5 m of permafrost from wedge, segregated and relict ice (Modified from Ref 17).

 

Some of the most abrupt changes to terrestrial and aquatic environments in the NWT have resulted from the degradation of ice-rich permafrost (Ref 10). Thawing of ice-rich permafrost results in a thermokarst landscape, which can modify drainage (Ref 6), cause lakes or wetlands to expand (Ref 27; Ref 28), or conversely to drain (Ref 29), and vegetation communities to change irreparably. Landsliding or slumping can contribute large volumes of sediment into lakes and streams, raising suspended sediment and geochemical concentrations and adversely impacting aquatic habitat (Ref 30; Ref 31;Ref 8). Thaw slumping and permafrost degradation can also influence lake or stream water chemistry by exposing previously frozen materials to leaching or increasing groundwater flow (Ref 32). Terrestrial ecosystems are also modified by the formation or degradation of ground ice. For example, heaving of the ground can cause hummocky terrain, and subsidence may produce “drunken forests” (Ref 33). Both thaw slumping and collapse of peatlands can change moisture and chemical conditions in soils (Ref 34; Ref 28). Permafrost disturbances can also expose mineral soils for colonization by disturbance-adapted species, which may contribute to changes in the composition of surrounding vegetation communities (Ref 35). Permafrost throughout large parts of the NWT has developed in organic deposits that sequester significant amounts of organic carbon so that their thawing has the potential to contribute to the global carbon-climate feedback (Ref 9).  

Figure 3. Ground ice examples in permafrost. A) Wedge ice exposed in an organic deposit, Mackenzie Delta region; and B) Sediment-rich ice exposed in late Wisconsinan end moraine sediments on the Peel Plateau, NWT (Photo courtesy H.B. O’Neill).

 

Determining areas with thaw-sensitive permafrost is also critical for planning sustainable infrastructure and predicting susceptibility to thaw-driven change (Ref 12). Since many NWT communities and linear infrastructure are built over ice-rich permafrost, its thaw can damage buildings, roads and other infrastructure facilities, leading to increased maintenance and mitigation costs (Ref 36).

Increasingly, multidisciplinary approaches are being implemented to investigate the sensitivity of permafrost environments and the consequences of thaw on northern environmental ecosystems and infrastructure. Tracking ground temperatures and active-layer monitoring in the NWT can give early-warning information on the degradation of permafrost and provide critical information to guide infrastructure design and modelling activities that project thaw. Delineating areas with ice-rich permafrost and mapping the distribution of features indicating landscape sensitivity to change provide a foundational knowledge base to inform environmental management, infrastructure planning and climate change adaptation. Together, monitoring these indicators offers important information to resource managers, planners, proponents of resource development projects and those charged with maintaining road, development and community infrastructure across the NWT. The strong links between permafrost and other components of the environment place the discipline of permafrost science in a unique position to serve a unifying role in investigating northern physical and biological processes and their responses to global change. The high priority of permafrost issues in the development and management of northern infrastructure highlights the importance of the discipline in engineering and northern geoscience.

This indicator was prepared by the Northwest Territories Geological Survey (GNWT, Dept. Industry, Tourism and Investment) and the Geological Survey of Canada (NRCan).

 

References

Ref 1: Lantz, T.C. and Kokelj, S.V. 2008. Increasing rates of retrogressive thaw slump activity in the Mackenzie Delta region, N.W.T. Canada. Geophysical Research Letters 35: L06502.

Ref: 2: Smith S.L., Romanovsky V.E., Lewkowicz A.G., Burn C.R., Allard M., Clow G.D., Yoshikawa, K., Throop J. 2010. Thermal state of permafrost in North America - a contribution to the International Polar Year; Permafrost and Periglacial Processes 21: 117-135.

Ref 3: Chadburn, S.E., Burke, E.J., Cox, P.M., Friedlingstein, P., Hugelius, G. & Westermann, S. 2017. An observation-based constraint on permafrost loss as a function of global warming. Nature Climate Change 7: 340–344. DOI: 10.1038/nclimate3262

Ref 4: Wolfe, S.A., Morse, P.D., Hoeve, T.E., Sladen, W.E., Kokelj, S.V. and Arenson, L.U. 2015. Disequilibrium conditions on NWT Highway 3. In Proceedings, 68th Canadian Geotechnical Conference and 7th Canadian Permafrost Conference, Quebec City, QC, September 20-23, 2015. Canadian Geotechnical Society: Richmond, BC paper 115; 8 pp.

Ref 5: Fraser, R.H., Kokelj, S. V., Lantz, T.C., McFarlane-Winchester, M., Olthof, I. & Lacelle, D. 2018. Climate sensitivity of high arctic permafrost terrain demonstrated by widespread ice-wedge thermokarst on banks Island. Remote Sensing 10: DOI: 10.3390/rs10060954

Ref 6: Farquharson, L.M., Romanovsky, V.E., Cable, W.L., Walker, D.A., Kokelj, S. V. & Nicolsky, D. 2019. Climate Change Drives Widespread and Rapid Thermokarst Development in Very Cold Permafrost in the Canadian High Arctic. Geophysical Research Letters 46: 6681–6689. DOI: 10.1029/2019GL082187

Ref 7: Lewkowicz, A.G. & Way, R.G. 2019. Extremes of summer climate trigger thousands of thermokarst landslides in a High Arctic environment. Nature Communications 10: 1–11. DOI: 10.1038/s41467-019-09314-7

Ref 8: Zolkos, S., Tank, S.E., Striegl, R.G., Kokelj, S.V., Kokoszka, J., Estop-Aragonés, C., & Olefeldt, D. 2020. Thermokarst amplifies fluvial inorganic carbon cycling and export across watershed scales on the Peel Plateau, Canada. Biogeosciences 17(20): 5163–5182. https://doi.org/10.5194/bg-2020-111

Ref 9: Turetsky, M.R., Abbott, B.W., Jones, M.C., Anthony, K.W., Olefeldt, D., Schuur, E.A.G., Grosse, G., Kuhry, P., Hugelius, G., Koven, C., Lawrence, D.M., Gibson, C., Sannel, A.B.K. & McGuire, A.D. 2020. Carbon release through abrupt permafrost thaw. Nature Geoscience 13: 138–143. DOI: 10.1038/s41561-019-0526-0

Ref 10: Kokelj, S.V., Kokoszka, J., van der Sluijs, J., Rudy, A.C.A., Tunnicliffe, J., Shakil, S., Tank, S., Zolkos, S. 2021. Permafrost thaw couples slopes with downstream systems and effects propagate through Arctic drainage networks. The Cryosphere. (In Press)

Ref 11: Heginbottom, J.A., Dubreuil, M.A., Harker, P.A. 1995. Canada — permafrost, National Atlas of Canada, 5th edition. National Atlas Information Service, Natural Resources Canada, Ottawa. MCR 4177

Ref 12: Wolfe, S.A., Kokelj, S.V. 2019. A history of water and ice: A field guide to permafrost and environmental change in the Yellowknife area, Northwest Territories: NWT Geological Survey, Open Report 2019-013; GSC, Open File 8530, 44 pgs. https://doi:10.4049/315145

Ref 13: Mackay, J.R. 1972. Offshore permafrost and ground ice, southern Beaufort Sea, Canada. Canadian Journal of Earth Sciences, 9(11): 1550-1561.

Ref 14: Throop, J., Lewkowicz, A.G. and Smith, S.L. 2012. Climate and ground temperature relations at sites across the continuous and discontinuous permafrost zones, northern Canada. Canadian Journal of Earth Sciences, 49(8): 865-876.

Ref 15: Zoltai, S.C. and Tarnocai, C. 1975. Perennially frozen peatlands in the Western Arctic and subarctic of Canada. Canadian Journal of Earth Science 12: 28-43.

Ref 16: O’Neill, H.B., Wolfe, S.A. & Duchesne, C. 2019. New ground ice maps for Canada using a paleogeographic modelling approach. Cryosphere 13 : 753–773. DOI: 10.5194/tc-13-753-2019

Ref 17: O’Neill, H.B., Wolfe, S.A., and Duchesne, C. 2020. Ground ice map of Canada; Geological Survey of Canada, Open File 8713, ver. 1, 1 .zip file. https://doi.org/10.4095/326885

Ref 18: Mackay, J. 1979. Pingos of the Tuktoyaktuk peninsula area, Northwest territories. Géographie physique et Quaternaire, 33(1): 3-61.

Ref 19: Kokelj, S.V., Lantz, T.C., Wolfe, S.A., Kanigan, J.C., Morse, P.D., Coutts, R., Molina‐Giraldo, N. and Burn, C.R. 2014. Distribution and activity of ice wedges across the forest‐tundra transition, western Arctic Canada. Journal of Geophysical Research: Earth Surface 119(9): 2032-2047.

Ref 20: Wright, N., Quinton, W.L. and Hayashi, M., 2008. Hillslope runoff from an ice‐cored peat plateau in a discontinuous permafrost basin, Northwest Territories, Canada. Hydrological Processes: An International Journal 22(15): 2816-2828.

Ref 21: Wolfe, S.A., Stevens, C.W., Gaanderse, A.J. and Oldenborger, G.A. 2014. Lithalsa distribution, morphology and landscape associations in the Great Slave Lowland, Northwest Territories, Canada. Geomorphology 204: 302-313.

Ref 22: Mackay, J.R. 1972. The world of underground ice. Annals of the Association of American Geographers 6: 1-22.

Ref 23: Paul, J.R., Kokelj, S.V. and Baltzer, J.L. 2021. Spatial and stratigraphic variation of near‐surface ground ice in discontinuous permafrost of the taiga shield. Permafrost and Periglacial Processes, 32(1): 3-18.

Ref 24: Mackay, J.R. 1970. Disturbances to the tundra and forest tundra environment of the western Arctic. Canadian Geotechnical Journal 7: 420-432.

Ref: 25: Wolfe, S.A., Kerr, D.E. and Morse, P.D. 2017. Slave Geological Province: An Archetype of Glaciated Shield Terrain. In: Landscapes and Landforms of Western Canada. Olav Slaymaker (Ed). Springer Verlag, 77-86.

Ref 26: Subedi, R., Kokelj, S.V. and Gruber, S. 2020. Ground ice, organic carbon and soluble cations in tundra permafrost soils and sediments near a Laurentide ice divide in the Slave Geological Province, Northwest Territories, Canada. The Cryosphere, 14(12): 4341-4364.

Ref 27: Kokelj, S.V., Lantz, T.C., Kanigan, J., Smith, S.L. and Coutts, R. 2009a. Origin and polycyclic behaviour of tundra thaw slumps, Mackenzie Delta region, Northwest Territories, Canada. Permafrost and Periglacial Processes, 20(2): 173-184.

Ref 28: Quinton, W.L., Hayashi, M. and Chasmer, L.E. 2011. Permafrost‐thaw‐induced land‐cover change in the Canadian subarctic: implications for water resources. Hydrological Processes, 25(1): 152-158.

Ref 29: Marsh, P., Russell, M., Pohl, S., Haywood, H. and Onclin, C. 2009. Changes in thaw lake drainage in the Western Canadian Arctic from 1950 to 2000. Hydrological Processes: An International Journal, 23(1): 45-158.

Ref 30: Kokelj, S.V., Lacelle, D., Lantz, T.C., Tunnicliffe, J., Malone, L., Clark, I.D. and Chin, K.S. 2013. Thawing of massive ground ice in mega slumps drives increases in stream sediment and solute flux across a range of watershed scales. Journal of Geophysical Research: Earth Surface, 118(2): 681-692.

Ref 31: Chin, K. S., Lento, J., Culp, J. M., Lacelle, D., and Kokelj, S. V.: Permafrost thaw and intense thermokarst activity decreases abundance of stream benthic macroinvertebrates. Glob. Change Biol., 22, 2715–2728. https://doi.org/10.1111/gcb.13225, 2016.

Ref 32: Malone, L., Lacelle, D., Kokelj, S. and Clark, I.D. 2013. Document Impacts of hillslope thaw slumps on the geochemistry of permafrost catchments (Stony Creek watershed, NWT, Canada). Chemical Geology 356: 38-49.

Ref 33: Kokelj, S.V., Burn, C.R., Tarnocai, C. 2007. The structure and dynamics of earth hummocks in the subarctic forest near Inuvik, Northwest Territories, Canada. Arctic, Antarctic and Alpine Research 39: 99-109.

Ref 34: Kokelj, S.V., Zajdlik, B. and Thompson, M.S., 2009b. The impacts of thawing permafrost on the chemistry of lakes across the subarctic boreal‐tundra transition, Mackenzie Delta region, Canada. Permafrost and Periglacial Processes, 20(2), pp.185-199.

Ref 35: Lantz, T.C., Kokelj, S.V., Gergel, S.E., and Henry, G.H.R. 2009. Relative impacts of disturbance and temperature: persistent changes in microenvironment and vegetation in retrogressive thaw slumps. Global Change Biology 15: 1664-1675.

Ref 36: Canadian Standards Association. 2021. Moderating the effects of permafrost degradation on existing building foundations. CAN/CSA-S501-21.

 

 

13.1 Status of Ground Temperature(s)

This indicator characterizes the ground thermal regime of permafrost. Monitoring permafrost temperatures provides planners, resource managers and engineers with valuable information on its thermal state across the NWT.

Researchers in the Northwest Territories Geological Survey (NTGS) and Geological Survey of Canada (GSC), academic researchers, infrastructure departments, and industry contribute significant data and information to the understanding of ground thermal regimes in the NWT.

GSC monitors ground temperatures throughout the Canadian North (Ref. 1. and Ref. 2.), and several monitoring sites in the Mackenzie Valley have been operating since the 1980s. Some ground temperature monitoring occurs collaboratively between government agencies, academic partners, and industry, including the North Slave (Ref. 3.), along the Inuvik to Tuktoyaktuk and Dempster Highway corridor (Ref. 4. and Ref. 5.). Ground temperature data is also collected by industry for infrastructure design (Ref. 6.) and through the regulatory process.

This indicator was prepared by the Government of the Northwest Territories, Department of Industry, Tourism and Investment, Northwest Territories Geological Survey and the Geological Survey of Canada.

 

Ground temperatures:

Monitoring programs should determine the depth and frequency of ground temperature collection. Studies investigating the influence of snow, vegetation or disturbances on soil conditions may monitor temperatures near the ground surface. Long-term tracking of changes in ground temperatures should focus on temperatures at depth where there is no variation with seasons. A change in temperature at this depth indicates a shift in the ground thermal regime.

 

NWT Focus

Knowledge of ground temperatures in permafrost environments is required to design northern infrastructure, assess environmental impacts of development, and plan mitigation. The physical stability of frozen ground is closely linked to its thermal state. Therefore, temperature increases causing permafrost thaw can affect the land and water, the integrity of ecosystems and release carbon sequestered in permafrost, further highlighting the importance of understanding how climate warming affects permafrost temperatures.

Increasing air temperature, changes in vegetation, and increasing snow cover and soil moisture can result in the warming and thawing of permafrost. The collection of complementary field data at monitoring sites is essential 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 northward. Mean annual ground temperatures in permafrost range from close to 0°C in the southern NWT to below -6 oC in tundra environments where permafrost may be several hundreds of metres thick (Ref. 1, Ref. 2, Ref. 3, Ref. 7, Ref. 8).

Permafrost temperatures across the NWT are increasing in response to climate warming. In the Mackenzie Delta region, ground temperatures have increased by up to 2°C since the early 1970s (Ref. 7). Figure 1A shows that the permafrost temperatures at several metres depth have steadily increased in the Tundra Plains ecozone or northern Mackenzie region since the mid-2000s, rising by at least 0.5°C per decade (Ref. 2). Rates of temperature increase have been lower in the warmer permafrost of the central and southern Mackenzie Valley in the Taiga Plain ecozone (Figure 1B). The mean annual ground temperature has increased by up to 0.3°C per decade at sites between Norman Wells and Fort Good Hope and just by 0.2°C per decade at sites located further south (Ref. 1, Ref. 2).

Figure 1A. Mean annual ground temperature in the continuous permafrost zone of the Northern Mackenzie region (Ref. 2). Temperature is measured near the depth where seasonal variation is negligible. KC-07 (69.31°N 135.25°W) is a tundra upland site, and NC-01 68.41°N 133.29°W) is located near treeline. Figure 1B. shows mean annual ground temperatures in the discontinuous permafrost zone (adapted from Ref. 2), in the central and southern Mackenzie Valley at a site near Norman Wells (84-2B, 65.23°N 126.52°W), near Wrigley (85-7A, 63.61°N 123.64°W) and between Wrigley and Fort Simpson (WLR-01 62.71°N 123.08°W). Seasonal variation at the shallow depth of measurement at WLR-01 and the response to year-to-year air temperature variation will be greater than at the deeper measurement depths at the other two sites.

 

Current research indicates that the cumulative impacts of disturbance or ecological change will compound the effects of climate warming on the thermal stability of permafrost. Disturbance of the forest cover resulting from human activity or fire can alter the surface energy balance and lead to warming and degradation of permafrost under contemporary climate conditions (Refs. 9-12). Thermal modelling has shown that most 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 rising air temperatures (Ref. 19). This study also illustrates that shrubbier tundra and enhanced snow cover will likely accelerate the warming of permafrost anticipated with climate change.

 

Looking around

Warming of permafrost has also been observed elsewhere in northern Canada, including in the Yukon and the eastern and high Arctic (Ref. 1, Ref. 15). Permafrost is also warming in Alaska (Ref. 16). Some recent modelling projections of permafrost degradation probably overestimate the rates and magnitude of future thawing. Still, both empirical and modelling evidence suggests that over the next several decades, continued climate warming will cause permafrost to warm, and in some areas, such as the discontinuous permafrost zone where permafrost is thinner, to thaw entirely (Ref. 14).

 

Looking forward

Ground temperatures are expected to increase with continued global warming. Still, the response of the ground thermal regime will depend on local site conditions, including vegetation, snow cover and the earth materials (Ref. 14). 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 water (Ref. 20) (Figure 1B).

Planning and managing the development of northern infrastructure and understanding environmental responses to climate change requires information on permafrost temperatures. Air temperature, snow cover, vegetation, and soil organic cover all influence the ground thermal regime, and measurement of these parameters should complement ground thermal monitoring programs.

 

Find out more

The GSC has published reports (Ref. 2, Ref. 3) that include ground temperature databases and data summaries accessible through GEOSCAN (https://geoscan.nrcan.gc.ca/). The NTGS is in the process of developing an NWT Permafrost Database that will host permafrost ground temperature and geotechnical datasets. The first phase of the NWT Permafrost Database is nearing completion, and Phase 2, the development of the website, will begin soon.

For more indicators related to landscape, see the focal point Landscape Changes.

 

References

Ref. 1.  Smith, S.L., Duchesne, C., Lewkowicz, A.G. 2019. Tracking changes in permafrost thermal state in Northern Canada. In: Bilodeau J-P, Nadeau DF, Fortier D, Conciatori D (eds) Cold Regions Engineering 2019, Proceedings of the 18th International Conference on Cold Regions Engineering and the 8th Canadian Permafrost Conference, Quebec, Quebec, Canada, August 18-22 2019 2019. American Society of Civil Engineers, pp 670-677. doi:10.1061/9780784482599

Ref. 2.  Duchesne, C., Chartrand, J., Smith, S.L. 2020. Report on 2018 field activities and collection of ground-thermal and active-layer data in the Mackenzie corridor, Northwest Territories. Geological Survey of Canada Open File 8707. doi:10.4095/321921

Ref. 3.  Duchesne, C., Morse, P.D., Wolfe, S.A., Kokelj, S.V. 2016. Report on 2010-2015 Permafrost thermal investigations in the Yellowknife Area, Northwest Territories. Geological Survey of Canada Open File 8093 and NWT Open Report 2016-019. doi:10.4095/299189

Ref. 4.  Cameron, E.A., Lantz, T.C., O’Neill, H.B., Gill, H.K., Kokelj, S.V., and Burn, C.R., 2019. Permafrost Ground Temperature Report: Ground temperature variability among terrain types in the Peel Plateau region of the Northwest Territories (2011-2015); Northwest Territories Geological Survey, NWT Open Report 2017-009, 8 pages and data.

Ref. 5.  Ensom, T., Kokelj, S.V., Morse, P.D., and Kamo McHugh, K., 2020. Permafrost Ground Temperature Data Synthesis: 2013 ̶ 2019 Inuvik‐Tuktoyaktuk Highway region, Northwest Territories; Northwest Territories Geological Survey, NWT Open Report 2019‐020; Geological Survey of Canada, Open File 8656, 13 pages and appendix. https://doi.org/10.4095/3218700

Ref. 6.  Canadian Standards Association. 2019. Plus 4011:19 Technical Guide: Infrastructure in permafrost: A guideline for climate change adaptation

Ref. 7.  Wolfe, S.A., Morse, P.D., Hoeve, T.E., Sladen, W.E., Kokelj, S.V. and Arenson, L.U. 2015. Disequilibrium conditions on NWT Highway 3. In Proceedings, 68th Canadian Geotechnical Conference and 7th Canadian Permafrost Conference, Quebec City, QC, September 20-23, 2015. Canadian Geotechnical Society: Richmond, BC paper 115; 8 pp.

Ref. 8.  Kokelj, S.V., Palmer, M.J., Lantz, T.C., Burn, C.R. 2017. Ground temperatures and permafrost warming from forest to tundra, Tuktoyaktuk Coastlands and Anderson Plain, NWT, Canada. Permafrost and Periglacial Processes 28: 543-551. DOI: 10.1002/ppp.1934

Ref. 9.  Smith, S.L., Riseborough, D.W., Bonnaventure, P.P. 2015. Eighteen year record of forest fire effects on ground thermal regimes and permafrost in the central Mackenzie Valley, NWT, Canada. Permafrost and Periglacial Processes 26 (4): 289-303. doi:10.1002/ppp.1849

Ref. 10. Smith, S.L., Riseborough, D.W. 2010. Modelling the thermal response of permafrost terrain to right-of-way disturbance and climate warming. Cold Regions Science and Technology 60: 92-103. doi:10.1016J.coldregions.200908.009

Ref. 11. Holloway, J.E., Lewkowicz, A.G. 2020. Half a century of discontinuous permafrost persistence and degradation in western Canada. Permafrost and Periglacial Processes 31: 85-96. doi:10.1002/ppp.2017

Ref. 12. Holloway, J.E., Lewkowicz, A.G., Douglas, T.A., Li, X., Turetsky, M.R., Baltzer, J.L. and Jin, H. 2020. Impact of wildfire on permafrost landscapes: A review of recent advances and future prospects. Permafrost and Periglacial Processes 31: 371-382. doi:10.1002/ppp.2048

Ref. 13. Zhang, Y., Olthof, I., Fraser, R., and Wolfe, S.A. 2014. A new approach to mapping permafrost and change by incorporating uncertainties in ground conditions and climate projections. The Cryosphere 8: 1895-1935.

Ref. 14. IPCC. 2019. IPCC Special Report on the Ocean and Cryosphere in a Changing Climate. https://www.ipcc.ch/srocc/

Ref. 15. Derksen, C., Burgess, D., Duguay, C., Howell, S., Mudryk, L., Smith, S., Thackeray, C., Kirchmeier-Young, M. 2019. Chapter 5, Changes in Snow, Ice and Permafrost Across Canada. In: Bush E, Lemmen DS (eds) Canada's Changing Climate Report. Government of Canada, Ottawa, pp 194-260

Ref. 16. Romanovsky, V.E., Smith, S.L., Isaksen, K., Nyland, K.E., Kholodov, A.L., Shiklomanov, N.I., Streletskiy, D.A., Farquharson, L.M., Drozdov, D.S., Malkova, G.V., Christiansen, H.H. 2020. [Arctic] Terrestrial Permafrost [in "State of the Climate in 2019"]. Bulletin of the American Meteorological Society (supplement) 101 (8):S265-S269. doi:10.1175/BAMS-D-20-0086.1

Ref. 17. Smith, S.L., Burgess, M.M., Riseborough, D.W. 2008. Ground temperature and thaw settlement in frozen peatlands along the Norman Wells pipeline corridor, NWT Canada: 22 years of monitoring. In: Kane DL, Hinkel KM (eds) Ninth International Conference on Permafrost, Fairbanks Alaska, 2008. Institute of Northern Engineering, University of Alaska Fairbanks, pp 1665-1670

Ref. 18. Smith, S.L., Burgess, M.M. 2002. A digital database of permafrost thickness in Canada. Geological Survey of Canada Open File 4173. doi:10.4095/213043

Ref. 19. Kokelj, S.V., Riseborough, D. Coutts, R., Kanigan, J.C.N. 2010. Permafrost and terrain conditions at northern drilling-mud sumps: Impacts of vegetation and climate change and the management implications. Cold Regions Science and Technology 64: 46-56. doi:10.1016/j.coldregions.2010.04.009

Ref. 20. Smith, S.L., Romanovsky, V.E., Lewkowicz, A.G., Burn, C.R., Allard, M., Clow, G.D., Yoshikawa, K., Throop, J. 2010. Thermal state of permafrost in North America - a contribution to the International Polar Year; Permafrost and Periglacial Processes 21: 117-135.

 

 

13.2 Trends in active-layer thickness in the NWT

This indicator tracks changes in the thickness of the active layer, which is the top layer of ground above the permafrost that thaws and refreezes each year.

Active-layer thickness can be measured by frost probing, and thaw penetration relative to a fixed datum which can be measured with a frost tube installation (Figures 1 and 2) (Ref. 1, Ref. 2, Ref. 3). Thaw penetration is currently monitored at several locations throughout the NWT (Figure 3). When read periodically, frost tubes provide information about the seasonal progression of thaw and maximum seasonal thaw, as well as the position of the ground surface (Ref. 3, Ref. 4). In addition, these instruments have been used successfully as part of Natural Resource Canada’s (NRCan) long-term active layer monitoring network in the Mackenzie Valley.

This indicator was prepared by the Government of the Northwest Territories, Department of Industry, Tourism and Investment, Northwest Territories Geological Survey and the Geological Survey of Canada.

 

Active layer: The layer above the permafrost that thaws and refreezes each year. Several important biological, hydrologic, pedologic, geomorphic and biogeochemical processes operate within this surface layer that overlies permafrost.

Frost probing: Measurement that involves pushing a small-diameter metal rod to depth of refusal to probe the depth of thaw.

Latent heat effects: The rate of ground warming or cooling typically slows as temperatures approach 0oC because of the large amounts of energy associated with changing water into ice, and vice versa.

Frost Tubes: This simple installation measures cumulative thaw depth (active-layer thickness and subsidence), which together reflects thaw penetration. This is particularly useful where near-surface permafrost has a high ice content.

Figure 1. Schematic of a frost tube for measuring active-layer thickness and surface heave or subsidence, required to determine thaw penetration (Ref. 24)..

 

Figure 2. Permafrost researchers frost probing to determine the depth of thaw.

 

NWT Focus

Measurements of active-layer thickness provide information to help characterize permafrost environments. Active-layer thicknesses are influenced by climate, vegetation, and soil conditions. As a result, thaw depths can vary significantly across local scales and between regions of the NWT. Monitoring thaw depths over several years can track any changes that may result from environmental disturbance, ecological succession or climate. Year-to-year variation in active-layer thickness is generally related to summer air temperature commonly represented by thawing degree days and inter-annual variations in soil moisture (Ref. 5, Ref. 6, Ref. 3, Ref. 7).

If near-surface permafrost is ice-rich, an increase in active-layer thickness will be accompanied by surface subsidence as ground ice melts. This can have significant impacts on buildings and roads, and in natural settings, terrain subsidence can affect micro-relief and drainage (Ref. 8).

Thawing can also release nutrients sequestered in permafrost and may affect biogeochemical cycling. Where active layers are thicker, there is more water storage capacity and greater amounts of soil for plant roots. With continued climate warming or disturbance, the active layer may not freeze back entirely in winter, contributing to permafrost degradation.

Slower freezing of the active layer can cause permafrost to warm (Ref. 9) and impact winter land access and the length of the winter operating season (Ref. 10, Ref. 11). An unfrozen layer of soil between permafrost and the frozen ground surface can convey water throughout the winter, influencing winter streamflow and chemistry and potentially contributing to the development of icings (Ref. 12, Ref. 13).

Figure 3. The NRCan thaw tube monitoring locations in the NWT.

 

Current view: status and trend

In the NWT, there is a general southward increase in active-layer thickness with increasing air temperatures. In tundra soils, mean maximum thaw depths are generally less than 80 cm, while in the southern NWT, thaw depths commonly exceed 100 cm (e.g., Ref. 7). However, in the boreal forests of the southern NWT, thicker organic ground cover inhibits frost penetration such that a greater number of thawing degree days are required to achieve similar active-layer thicknesses on the tundra (Ref. 14, Ref. 15). The heterogeneity in vegetation, soil and drainage can also cause active layer thicknesses to vary significantly at local scales.

Active-layer thickness has responded significantly to past (Ref. 16) and recent climate change (Ref. 17). Due to the high degree of spatial variability in thaw depths and a limited observational record at most sites, conclusions regarding observational trends related to climate warming can be difficult to make.

Long-term active layer monitoring by Dr. J.R. Mackay (Ref. 18) in the Mackenzie Delta region has shown that fire disturbance and subsequent ecological recovery can have a dominant effect on active-layer thicknesses. Thaw depths increased by up to 100 cm following the fire to depths of 140 cm. However, the burned active layer has progressively thinned over the past 20 years due to the establishment of organic ground cover and the shading effect of shrubs. Active-layer thicknesses in some unburned areas also decreased due to a proliferation of moss and shrub cover at those sites. Active-layer thinning on the bed of a lake drained in 1978 is also attributed mainly to ecological succession (Ref. 19). These studies show the benefits of collecting complementary data sets when implementing long-term monitoring programs.

Records for active layer thickness are over 20 years long in the Mackenzie Valley and Delta areas (Ref. 7). However, the significant differences between sites and inter-annual variability can obscure long-term trends. An analysis of data from 25 monitoring sites (Figure 3) (Ref. 7) indicates that, on average, the greatest active layer thickness occurred in 1998 (Figure 4), which was an extremely warm year associated with El Nino (Ref. 17, Ref. 20).

Active layer thickness generally declined over subsequent years but started increasing after 2008, coincident with higher air temperatures, until reaching a peak in 2012 that was still less than the 1998 peak. For some sites, very little change in active layer thickness over time is observed (Ref. 4). At sites with ice-rich permafrost, ground settlement accompanies the melting of ground ice. Observations from the thaw tubes, which record thaw penetration relative to the original ground surface position, indicate that since the 1990s, thaw has progressed deeper in the ground at several sites and surface subsidence (more than 15 cm at some sites) and permafrost degradation has occurred even though little change in active layer thickness is observed.

Figure 4. Mean active-layer thickness (ALT) departures (%) from 2003-2012 mean for 25 sites in the Mackenzie Valley (Ref. 7).

 

Looking forward

It is anticipated that active-layer thickness and thaw penetration will increase in this century with climate warming (Ref. 14, Ref. 21, Ref. 22). However, the rates of increase will be influenced by local conditions such as the thermal properties of the soils, ice content of the permafrost, presence and thickness of an organic layer, and also in association with feedbacks that involve changing vegetation cover and soil moisture (Ref. 18).

Areas outside of the Mackenzie Valley are under-represented in the monitoring network (Figure 3). The effects of warming on active-layer thickening are influenced by vegetation cover, and soil moisture and, therefore, monitoring should take place in various ecological terrain types within representative ecoregions throughout the NWT. Monitoring programs should also include collecting complementary data on other environmental parameters that may influence active-layer development.

 

Looking around

In areas of ice-rich permafrost, maintaining long-term datasets will be critical to detecting changes in thaw depths. Furthermore, since the thawing of ice-rich permafrost may cause surface subsidence rather than an increase in thaw depths, establishing stable reference points and assessing surface heave or subsidence is also essential. The Circumpolar Active Layer Monitoring (CALM) Network includes 168 active sites in both hemispheres and is a coordinated effort by 15 countries to observe and detect decadal changes in the active layer (Ref 5, 23). Identifying and monitoring changes to the active layer has important implications for sediment transport and hydrological processes, both of which affect terrestrial and aquatic systems.

 

Find out more

For information on the locations of active-layer monitoring in the NWT visit the CALM website at http://www.udel.edu/Geography/calm/. Additionally, the NRCan website may be visited for further information on NWT sites: http://www.GTNP.org

Ref. 1 also provides a table and maps of active-layer monitoring sites along the Mackenzie Valley.

Several papers written by Dr. J.R. Mackay provide examples of long-term active-layer monitoring, but these are limited primarily to the Mackenzie Delta region (Ref. 18, Ref. 19).

Selected Mackenzie Valley monitoring sites contribute to the Circumpolar Active-Layer Monitoring Program (CALM) https://www2.gwu.edu/~calm//.

For more indicators related to large scale changes in the NWT landscape and to vegetation, see the focal points Landscape Changes and Vegetation.

 

References

Ref. 1.  Nixon, F.M., Tarnocai, C., and Kutny, L. 2003. Long-term active layer monitoring: Mackenzie Valley, northwest Canada. In: Proceedings of the Eight international Conference on Permafrost (Vol 2)., M. Philips, S.M. Springman, and L.U. Arenson, Eds., A.A. Balkema, Swets & Zeitlinger, Lisse, The Netherlands, pp. 821-826.

Ref. 2.  Smith, S.L., Riseborough, D.W., Nixon, F.M., Chartrand, J., Duchesne, C., Ednie, M. 2009. Data for Geological Survey of Canada active layer monitoring sites in the Mackenzie valley, N.W.T. Geological Survey of Canada Open File 6287. doi:10.4095/248197.

Ref. 3.  Duchesne, C., Smith, S.L., Ednie, M., Bonnaventure, P.P. 2015. Active layer variability and change in the Mackenzie Valley, Northwest Territories. In: GEOQuébec 2015 (68th Canadian Geotechnical Conference and 7th Canadian Conference on Permafrost), Québec, 2015. GEOQuébec 2015 Organizing Committee, Paper 117.

Ref. 4.  O'Neill, H.B., Smith, S.L., Duchesne, C. 2019. Long-term permafrost degradation and thermokarst subsidence in the Mackenzie Delta area indicated by thaw tube measurements. In: Bilodeau J-P, Nadeau DF, Fortier D, Conciatori D (eds) Cold Regions Engineering 2019, Proceedings of the 18th International Conference on Cold Regions Engineering and the 8th Canadian Permafrost Conference, Quebec, Quebec, Canada, August 18-22 2019 2019. American Society of Civil Engineers, pp 643-651. doi:10.1061/9780784482599

Ref. 5.  Brown, J., Hinkel, K.M., Nelson, F.E. 2000. The Circumpolar Active Layer Monitoring (CALM) Program: research designs and initial results. Polar Geography 24 (3): 165-258.

Ref. 6.  Smith, S.L., Wolfe, S.A. Riseborough, D. and Nixon., F.M. 2009. Active-layer characteristics and correlations to recent summer air temperature climatic indices, Mackenzie Valley, Canada. Permafrost and Periglacial Processes 20: 201-220.

Ref. 7.  Duchesne, C., Chartrand, J., Smith, S.L. 2020. Report on 2018 field activities and collection of ground-thermal and active-layer data in the Mackenzie corridor, Northwest Territories. Geological Survey of Canada Open File 8707. doi:10.4095/321921.

Ref. 8.  Kokelj, S.V., Burn, C.R., Tarnocai, C. 2007. The structure and dynamics of earth hummocks in the subarctic forest near Inuvik, Northwest Territories, Canada. Arctic, Antarctic and Alpine Research 39: 99-109.

Ref. 9.  Kokelj, S.V., Palmer, M.J., Lantz, T.C., Burn, C.R. 2017. Ground temperatures and permafrost warming from forest to tundra, Tuktoyaktuk Coastlands and Anderson Plain, NWT, Canada. Permafrost and Periglacial Processes 28: 543-551. DOI: 10.1002/ppp.1934.

Ref. 10. Smith, S.L., Riseborough, D.W., Bonnaventure, P.P., Duchesne, C. 2016. An ecoregional assessment of freezing season air and ground surface temperature in the Mackenzie Valley corridor, NWT, Canada. Cold Regions Science and Technology 125: 152-161. doi:10.1016/j.coldregions.2016.02.007.

Ref. 11. Sladen, W.E. Wolfe, S.A., Morse, P.D. 2019. Evaluation of threshold freezing conditions for winter road construction over discontinuous permafrost peatlands, subarctic Canada. Cold Regions Science and Technology 170: 102930. https://doi.org/10.1016/j.coldregions.2019.102930.

Ref. 12. Walvoord, M.A. and Kurylyk, B.L. 2016. Hydrological impacts of thawing permafrost-A review, Journal of the Vadose Zone 15(6). //doi:10.2136/vzj2016.01.0010

Ref. 13. van der Sluijs, J., Kokelj, S.V., Fraser, R.H., Tunnicliffe, J. & Lacelle, D. 2018. Permafrost terrain dynamics and infrastructure impacts revealed by UAV photogrammetry and thermal imaging. Remote Sensing 10. DOI: 10.3390/rs10111734.

Ref. 14. Woo, M-k, Mollinga, M., Smith, S.L. 2007. Climate warming and active layer thaw in the boreal and tundra environments of the Mackenzie Valley. Canadian Journal Earth Sciences 44: 733-743.

Ref. 15. Morse, P.D., Wolfe, S.A., Kokelj, S.V. and Ganderse, A.J.R. 2016. The Occurrence and Thermal Disequilibrium State of Permafrost in Forest Ecotopes of the Great Slave Region, Northwest Territories, Canada. Permafrost and Periglacial Processes 27: 145-162 DOI: 10.1002/ppp.1858.

Ref. 16. Burn C.R. 1997. Cryostratigraphy, paleogeography, and climate change during the early Holocene warm interval, western Arctic coast, Canada. Canadian Journal of Earth Sciences 34: 912-925.

Ref. 17. Wolfe S.A., Kotler, E. and Nixon M.F. 2000. Recent warming impacts in the Mackenzie Delta, Northwest Territories, and northern Yukon Territory coastal areas. Current Research, Geological Survey of Canada Paper, 2000-B1, 11 p.

Ref. 18. Mackay, J.R. 1995. Active layer changes (1968 to 1993) following the forest-tundra fire near Inuvik, N.W.T., Canada. Arctic and Alpine Research 27: 323-336.

Ref. 19. Mackay, J.R. and Burn C.R. 2002. The first 20 years (1978-1979 to 1998-1999) of active-layer development, Illisarvik experimental drained lake site, western Arctic coast, Canada. Canadian Journal of Earth Sciences 39: 1657-1674.

Ref. 20. Atkinson, D.E., Brown, R., Alt, B., Agnew, T., Bourgeois, J., Burgess, M., Duguay, C., Henry, G., Jeffers, S., Koerner, R., Lewkowicz, A.G., McCourt, S., Melling, H., Sharp, M., Smith, S., Walker, A., Wilson, K., Wolfe, S., Woo, M-k, Young, K. 2006. Canadian cryospheric response to an anomalous warm summer: a synthesis of the Climate Change Action Fund Project "The state of the Arctic Cryosphere during the extreme warm summer of 1998". Atmosphere-Ocean 44 (4): 347-375.

Ref. 21. Duchesne, C., Wright J.F., and Ednie, M. 2008. High-resolution numerical modeling of climate change impacts to permafrost in the vicinities of Inuvik, Norman Wells, and Fort Simpson, NT, 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. 385-390.

Ref. 22. Zhang, Y., Olthof, I., Fraser, R., Wolfe, S.A. 2014. A new approach to mapping permafrost and change incorporating uncertainties in ground conditions and climate projections. The Cryosphere, 8: 2177–2194. doi:10.5194/tc-8-2177-2014.

Ref. 23. Biskaborn, B.K., Lanckman, J.-P., Lantuit, H., Elger, K., Streletskiy, D.A., Cable, W.L., Romanovsky, V.E. 2015. The new database of the Global Terrestrial Network for Permaforst (GTN-P). Earth Syst. Sci. Data 7:245-259. https://doi.org/10.5194/essd-7-245-2015

Ref. 24. Mackay, J.R. 1973. A frost tube for the determination of freezing in the active layer above permafrost. Canadian Geotechnical Journal 10: 392-396.

 

 

13.3 Trends in thermokarst in the NWT

This indicator tracks changes in thermokarst areal extent in selected areas of the NWT.

Increases in the areal extent of thermokarst are detected using various remote sensing techniques, including sequential analyses of aerial photographs (Ref. 1, Ref. 2), repeat unmanned aerial vehicle (UAV) surveys (Ref. 3), and manual or semi-automated analyses of satellite imagery (Ref. 4, Ref. 5). Remote sensing technology using interferometric satellite radar to track ground surface subsidence enables seasonal and annual vertical displacement of even a few centimetres to be resolved, so there is potential to utilize the tool to monitor the fine-scale stability of natural permafrost terrain (Ref. 6) or surface displacement in communities (Ref. 7).

Thawing of ice-rich permafrost in headwall of an active slump by Willow River, southest of Aklavik. Credit: Ashley Rudy

Thermokarst: A diverse range of landforms that develop as ground subsides due to thawing of ice-rich permafrost.

Thermokarst processes may cause lakes to enlarge, peatlands to collapse and landslides or retrogressive thaw slumps to develop.

 

Spatial data on this indicator are increasingly available due to scientific and public interest in the topic of permafrost thaw. Several Natural Resources Canada (NRCan) Open Files, Northwest Territories Geological Survey (NTGS) Open Reports, and other scientific publications provide spatial data describing the distribution of landsliding in the Mackenzie Valley (Ref. 8, Ref. 9) and Banks Island (Ref. 10, Ref. 11), and more generally, across western Arctic Canada (Ref. 12). New information on thaw sensitive peatlands in the Taiga Plains (Ref. 13) and lithalsa degradation and thermokarst pond expansion in the North Slave (Ref. 14, Ref. 15) have been generated, in addition to infrastructure corridor specific datasets describing a broad array of thermokarst indicators (Ref. 16) and highway embankment instabilities (Ref. 17). Thaw-driven terrain instability and interactions with infrastructure are being tracked by differencing high-resolution terrain surface models derived from UAV surveys and structure from motion techniques (Ref. 3).

This indicator was prepared by the Government of the Northwest Territories, Department of Industry, Tourism and Investment, Northwest Territories Geological Survey and the Geological Survey of Canada.

 

NWT Focus

Thermokarst disturbances can impact infrastructure and, therefore, determining sensitive environments and rates of thermokarst activity are critical to planning development and infrastructure monitoring. However, there are no systematic, broad-scale datasets that describe variation in thermokarst across the NWT.

In 2019, the NWT Thermokarst Mapping Collective (Ref. 18) was initiated to collaboratively develop theme-based methods to train mappers to inventory and attribute thermokarst features using satellite imagery. By implementing a grid-based mapping approach, the project has enabled developing observationally-based data around the themes of mass wasting, periglacial features, hydrological features, and organic terrain.

This project focuses on generating data for regions of key interest, including areas around all 33 NWT Communities (Figure 1).

Figure 1. Study area for the thermokarst collective mapping. Preliminary mapping is completed for the 33 NWT communities (blue boxes outlined in yellow) Ref. 28

 

Current view: status and trend

Recent studies of thermokarst landscape change show that in the southern part of the NWT, the rates and extent of peatland degradation have increased (Ref. 13, Ref. 19) and that in some regions, thaw lakes are expanding as ice-rich, forested lithalsas collapse (Ref. 15).

In the central Mackenzie Valley and the western Arctic, the size and abundance of thaw-driven landslides have increased, and impacts have the potential to cascade through aquatic systems (Ref. 20). In low and high Arctic environments, top-down thaw of ice-wedges (Ref. 21) is transforming upland terrain, causing high centred polygonal relief to increase and extensive areas of thaw ponding to develop (Figure 2) (Ref. 22, Ref. 23). Arctic environments underlain by large ice-wedges and lacking surface organic cover appear most sensitive to top-down thaw.

 

Looking forward

Climate-driven permafrost thaw can be anticipated to cause significant modification of terrestrial and aquatic ecosystems and cause impacts to infrastructure. Regions underlain by ice-rich permafrost will be the most sensitive to changes due to permafrost thaw (Ref. 20).

The realities of permafrost thaw raise several knowledge and capacity gaps that should be addressed in the coming decade. First, better characterization of thaw-sensitive landscapes is required (Ref. 18) to inform environmental and infrastructure management and community resilience. Integrating field-based programs that monitor permafrost conditions (ground temperatures, surface changes) with mapping initiatives are required to link site-specific knowledge with broad-scale depiction of change. Advances in remote sensing technology should be utilized to upscale observational results, but this should be complementary. Interdisciplinary projects that examine the effects of change on terrestrial and aquatic ecosystems or infrastructure should be guided to inform northern needs.

Figure 2. Top shows comparison of historical images of terrain on Banks Island and the result of top-down thaw of ice-wedges. The Map of Banks Island on the left shows where ice-wedge melt ponds have expanded since 1985 using a semi-automated remote sensing approach (Ref. 22).

 

Looking around

An increase in thermokarst research has been ongoing due to the environmental implications of permafrost degradation. Extensive research has been done to examine the interactions between thermokarst and hillslope processes (Ref. 10, Ref. 24), thaw lake processes (Ref. 25), wetland processes (Figure 3) (Ref. 13, Ref. 19, Ref. 26) and carbon feedbacks (Ref. 27). These studies show an increase in the rates and magnitude of thermokarst development in response to recent climate warming, although site-specific characteristics contribute to high variability.

Figure 3. The degree of thermokarst within permafrost peatland complexes in the Taiga Plains. Visually estimated as low (0-33%), moderate (34-67%), or high (67-100%). Source: Ref. 13.

 

Looking forward

Climate-driven permafrost thaw can be anticipated to cause significant modification of terrestrial and aquatic ecosystems and cause impacts to infrastructure. Regions underlain by ice-rich permafrost will be the most sensitive to changes due to permafrost thaw (Ref. 20).

The realities of permafrost thaw raise several knowledge and capacity gaps that should be addressed in the coming decade. First, better characterization of thaw-sensitive landscapes is required (see NWT Thermokarst Collective, https://www.nwtgeoscience.ca/services/northwest-territories-thermokarst-...) to inform environmental and infrastructure management and community resilience. Integrating field-based programs that monitor permafrost conditions (ground temperatures, surface changes) with mapping initiatives are required to link site-specific knowledge with broad-scale depiction of change. Advances in remote sensing technology should be utilized to upscale observational results, but this should be complementary. Interdisciplinary projects that examine the effects of change on terrestrial and aquatic ecosystems or infrastructure should be guided to inform northern needs.

 

Find out more

To learn more about the effects of thawing slopes on NWT environments, visit : https://www.nwtgeoscience.ca/services/permafrost-thaw-slumps#:~:text=Description,and%20a%20muddy%20slump%20floor

For more details on permafrost degradation along arctic coastlines, visit: https://coastalrra.grida.no/

 

 

References

Ref. 1.  Lantuit, H. and Pollard, W.H. 2005. Temporal stereophotogrammetric analysis of retrogressive thaw slumps on Herschel Island, Yukon Territory. Natural Hazards and Earth System Science 5: 413-423.

Ref. 2.  Lantz, T.C. and Kokelj, S.V. 2008. Increasing rates of retrogressive thaw slump activity in the Mackenzie Delta region, N.W.T. Canada. Geophysical Research Letters 35: L06502.

Ref. 3.  van der Sluijs, J., Kokelj, S.V., Fraser, R.H., Tunnicliffe, J. & Lacelle, D. 2018. Permafrost terrain dynamics and infrastructure impacts revealed by UAV photogrammetry and thermal imaging. Remote Sensing 10. DOI: 10.3390/rs10111734.

Ref. 4.  Brooker, A., Fraser, R.H., Olthof, I., Kokelj, S.V. and Lacelle, D. 2014. Tasseled Cap trend analysis of a Landsat satellite image stack (1985–2011): A method to track the life cycle of retrogressive thaw slumps at high temporal resolution. Permafrost and Periglacial Processes 25: 243–56, https://doi.org/10.1002/ppp.1819

Ref. 5.  Fraser, R.H., Olthof, I., Kokelj, S.V., Lantz, T.C., Lacelle, D., Brooker, A., Wolfe, S. and Schwarz, S. 2014. Detecting Landscape Changes in High Latitude Environments Using Landsat Trend Analysis. Remote Sensing 6: 11533-11557.

Ref. 6.  Samsonov, S.V., Lantz, T.C., Kokelj, S.V., and Zhang, Y. 2016. Growth of a young pingo in the Canadian Arctic observed by RADARSAT-2 interferometric satellite radar. The Cryosphere 10: 799-810, doi:10.5194/tc-10-799-2016

Ref. 7.  Wolfe, S.A., Short, N., Morse, P.D., Schwarz, S.H., and Stevens, C.W. 2014. Evaluation of RADARSAT-2 DInSAR Seasonal Surface Displacement in Discontinuous Permafrost Terrain, Yellowknife, Northwest Territories, Canada. Canadian Journal of Remote Sensing 40(6): 406-422. DOI: 10.1080/07038992.2014.1012836

Ref. 8.  Aylsworth J.M., Duk-Rodkin, A., Robertson, T., and Traynor, J.A. 2000. Landslides of the Mackenzie Valley and adjacent mountainous and coastal regions. In: The physical environment of the Mackenzie Valley, Northwest Territories: a baseline for the assessment of environmental change, L.D. Dyke and G.R. Brooks, Eds. Geological Survey of Canada, Bulletin 547: 167-176.

Ref. 9.  Couture, R. and Riopel, S. 2008. Landslide Inventory along a Proposed Gas Pipeline between Inuvik and Tulita, Mackenzie Valley, Northwest Territories Geological Survey of Canada, Open File 5740, 19 p.

Ref. 10. Lewkowicz, A.G. & Way, R.G. 2019. Extremes of summer climate trigger thousands of thermokarst landslides in a High Arctic environment. Nature Communications 10: 1–11. DOI: 10.1038/s41467-019-09314-7

Ref. 11. Rudy, A.C.A., Kokelj, S.V., and Kokozska, J. 2020. Inventory of retrogressive thaw slumps on the Peel Plateau and on southeastern Banks Island, Northwest Territories using 2017 Sentinel imagery, Northwest Territories Geological Survey, NWT Open Rep. 2020-012, https://doi.org/10.46887/2020-012, 2020.

Ref. 12. Segal, R.A., Kokelj, S.V., Lantz, T.C., Durkee, K., Gervais, S., Mahon, E., Snijders, M., Buysse, J., and Schwarz, S. 2016. Broad-scale mapping of terrain impacted by retrogressive thaw slumping in Northwestern Canada, Northwest Territories Geological Survey, NWT Open Rep. 2016-008, 17 pp.

Ref. 13. Gibson, C., Morse, P.D., Kelly, J.M., Turetsky, M.R., Baltzer, J.L., Gingras-Hill, T. and Kokelj S.V. 2020 Thermokarst Mapping Collective: Protocol for organic permafrost terrain and preliminary, inventory from the Taiga Plains test area, Northwest Territories (Yellowknife: Northwest Territories Geological Survey) NWT Open Report 2020-010, 24 pages, appendix, and digital data.

Ref. 14. Morse, P.D., McWade, T.L., and Wolfe, S.A. 2017. Thermokarst ponding, North Slave region, Northwest Territories; Geological Survey of Canada, Open File 8205, 1 .zip file. doi:10.4095/300531.

Ref. 15. Morse, P.D., Wolfe, S.A., Rudy, A.C.A. 2019. Lithalsa degradation and thermokarst distribution, subarctic Canadian Shield in, Cold Regions Engineering 2019: proceedings of the 18th International Conference on Cold Regions Engineering and the 8th Canadian Permafrost Conference; Bilodeau, J -P (ed.); Nadeau, D F (ed.); Fortier, D (ed.); Conciatori, D (ed.). p. 308-316, https://doi.org/10.1061/9780784482599.036 (NRCan Cont.# 20190038).

Ref. 16. Sladen, W.E., Morse, P.D., Kokelj, S.V., Parker, R.J.H., Smith, S.L. 2021. Geomorphologic feature mapping along the Dempster Highway and Inuvik to Tuktoyaktuk Highway corridor, Yukon and Northwest Territories, CanadaGeological Survey of Canada, Scientific Presentation 124, 1 sheet, https://doi.org/10.4095/328294

Ref. 17. Stevens, C.W., Short, N., and Wolfe, S.A. 2012. Seasonal Surface Displacement and Highway Embankment Grade Derived from InSAR and LiDAR, Highway 3 West of Yellowknife, Northwest Territories; Geological Survey of Canada, Open File 7087, 1 DVD. doi:10.4095/291383.

Ref. 18. Northwest Territories Geological Survey. Northwest Territories Thermokarst Mapping Collective. Accessed June 17, 2021 at https://www.nwtgeoscience.ca/services/northwest-territories-thermokarst-mapping-collective

Ref. 19. Quinton, W.L., Hayashi, M., and Chasmer, L.E. 2011. Permafrost-thaw-induced land-cover change in the Canadian subarctic: implications for water resources. Hydrol. Processes 25: 152–158. doi:10.1002/hyp.7894.

Ref. 20. Kokelj, S.V., Kokoszka, J., van der Sluijs, J., Rudy, A.C.A., Tunnicliffe, J., Shakil, S., et al. 2021. Permafrost thaw couples slopes with downstream systems and effects propagate through Arctic drainage networks, The Cryosphere Discuss. [in press], doi:10.5194/tc-2020-218.

Ref. 21. Burn, C.R., Lewkowicz, T., Wilson, A.M. 2021. Long-term field measurements of climate-induced thaw subsidence above ice wedges on hillslopes, western Arctic Canada. Permafrost and Periglacial Features 32(2): 261-276. https://doi.org/10.1002/ppp.2113

Ref. 22. Fraser, R.H., Kokelj, S. V., Lantz, T.C., McFarlane-Winchester, M., Olthof, I. & Lacelle, D. 2018. Climate sensitivity of high arctic permafrost terrain demonstrated by widespread ice-wedge thermokarst on banks Island. Remote Sensing 10 : DOI: 10.3390/rs10060954

Ref. 23. Farquharson, L.M., Romanovsky, V.E., Cable, W.L., Walker, D.A., Kokelj, S. V. & Nicolsky, D. 2019. Climate Change Drives Widespread and Rapid Thermokarst Development in Very Cold Permafrost in the Canadian High Arctic. Geophysical Research Letters 46: 6681–6689. DOI: 10.1029/2019GL082187

Ref. 24. Rudy, A.C.A., Lamoureux, S.F., Kokelj, S.V., Smith, I.R., England, J.H. 2017. Accelerating thermokarst transforms ice-cored terrain triggering a downstream cascade to the ocean. Geophysical Research Letters 44. https:// doi.org/10.1002/2017GL074912

Ref. 25. Bouchard, F., Fortier, D., Paquette, M., Boucher, V., Pienitz, R., Laurion, I. 2020. Thermokarst lake inception and development in syngenetic ice-wedge polygon terrain during a cooling climatic trend, Bylot Island (Nunavut), eastern Canadian Arctic. The Cryosphere 14:2607-2627. https://doi.org/10.5194/tc-14-2607-2020

Ref. 26. Connon, R.F., Quinton, W.L., Craig, J.R., and Hayashi, M. 2014. Changing hydrologic connectivity due to permafrost thaw in the lower Liard River valley, NWT, Canada. Hydrol. Processes 28: 4163–4178. doi:10.1002/hyp.10206.

Ref. 27. Turetsky, M.R., Abbott, B.W., Jones, M.C., Anthony, K.W., Olefeldt, D., Schuur, A.G. et al. 2020. Carbon release through abrupt permafrost thaw. Nature Geoscience 13: 138-143.

Ref. 28. Bouchard, F., Fortier, D., Paquette, M., Boucher, V., Pienitz, R., Laurion, I. 2020. Thermokarst lake inception and development in syngenetic ice-wedge polygon terrain during a cooling climatic trend, Bylot Island (Nunavut), eastern Canadian Arctic. The Cryosphere 14:2607-2627. https://doi.org/10.5194/tc-14-2607-2020

 

 

13.4 Status of NWT Water Resources Vulnerability to Permafrost Thaw

Permafrost thaw slumps near Aklavik, Northwest Territories. Over the past two decades the size and number of these landslides have increased more than tenfold in ice-rich areas of the western Arctic.

 

Northern Canadian water resources, here defined as the typical surface hydrological and aquatic chemistry regimes, characterized by their water budgets and water chemistry concentrations and loads (Ref. 1), are expected to be affected by climate change and permafrost thaw (Ref. 2). The Canadian Water Resources Vulnerability Index to Permafrost Thaw (CWRVIPT) is a pan-Canadian indicator of the vulnerability of water resources to change associated with potential permafrost thaw (Ref. 1), and it can aid in understanding the status of related environmental conditions in the NWT. The CWRIPT combines information on permafrost, terrain, disturbance, and climatic conditions and stressors that influence water budgets and aquatic chemistry, identifying areas of vulnerable water resources that merit more focused observation and research or that may require adjustments to land use and management policies. Such activities could include evaluating independent regional estimates of change in hydrological regimes, reducing uncertainty in identifying at-risk priority areas that may require more robust adaptation measures or on-site thaw-mitigation measures, or identifying areas where aquatic ecology and biodiversity are vulnerable to permafrost thaw.

The implications of permafrost thaw and landcover change have been researched across watershed scales for parts of the western Canadian Arctic and the discontinuous permafrost zone in the NWT. These investigations include changes in water quality due to permafrost degradation and thaw-driven mass wasting (Ref. 3), and changes in water quantity due to modification of snow accumulation, melt, flowpaths and runoff (Ref. 4). These observational and process-based studies support the development, interpretation and potential refinement of the CWRIPT.

It is important to note that the CWRIPT is a first-order indicator with caveats due to basic information gaps (some potentially essential factors could not be included or were represented by proxies) and limited availability of evaluation data, which must be considered whenever the CWRIPT is interpreted and applied (Ref. 1).

The CWRIPT is based on the application of a conceptual framework developed to assess the vulnerability of Northern Canadian water resources to permafrost thaw (Ref. 1). I The conceptual framework assumes that current landscape conditions (permafrost and terrain characteristics) and potential stressors (climate change and landscape disturbance) are the two categories of environmental factors that influence the vulnerability of water resources to permafrost thaw. The current conditions control the sensitivity of water resources to permafrost thaw, and potential stressors induce permafrost thaw at varying rates, over space and through time. Following this framework, the CWRIPT indicates vulnerability as the sum of four sub-indices for permafrost conditions (ground ice content, permafrost extent), terrain conditions (ice saturated soils, soil organic content, surficial geology, bedrock geology, ruggedness, land cover, sedimentary overburden), climate stressors (temperature, precipitation), and disturbance stressors (human presence, wildfire potential). The CWRIPT and its sub-indices are spatially distributed and plotted as maps or analyzed in a Geographic Information System (GIS).

Environment and Climate Change Canada developed the CWRIPT in collaboration with Natural Resources Canada, Carleton University, and the University of Waterloo. The CWRIPT is described in an Open Access article (Ref. 1), and the 24 influential indicators and factors that are included in the index are all Open Source. The spatial domain of the CWRIPT covers the entire NWT. Still, it excludes large lakes that are dominated by different processes than those represented using this approach (e.g., Great Bear and Great Slave) and several large rivers with headwaters outside of the CWRIPT domain (e.g., Mackenzie and Nelson) (Ref. 1). The CWRIPT is an indicator that can and should be modified with improved understanding and data quality, and availability.

This indicator was prepared by the Government of the Northwest Territories, Department of Industry, Tourism and Investment, Northwest Territories Geological Survey and the Geological Survey of Canada.

 

NWT Focus

The CWRIPT is the first attempt to develop and implement a conceptual framework to characterize water resource vulnerability due to permafrost thaw. The entire NWT is within the CWRIPT domain, thus it is directly relevant to assessing the state of water resources vulnerability in the territory. As a measure, the CWRIPT becomes critical as permafrost thaw is closely coupled to climate change and landscape disturbance, the temperature and precipitation regimes in northern Canada are changing rapidly (Ref. 5, Ref. 6), and disturbances are likely to increase in the future from human presence or potential wildfire (Ref. 7). Permafrost thaw can change water resources through at least 9 different mechanisms (Ref. 1), but the vulnerability of water resources to permafrost thaw varies considerably in space and time according to climate and disturbance stressors and permafrost and terrain conditions. The CWRIPT integrates all of these elements, which is important because it allows the CWRIPT to track the spatial change in water resource vulnerability with improvements in information and data and updates on permafrost conditions and climate and disturbance stressors as they change over time. Thus, the CWRIPT can be used to inform updates on the state of the environment.

 

Current View: status and trend

Figure 1. Spatial distribution in Canada of the CWRIPT sub-indices: (a) permafrost conditions; (b) terrain conditions; (c) climate stressors; and (d) landscape disturbance. Source: Ref. 1, Figure 2, (Open access publication).

 

To give context to the CWRIPT estimates, first the variation is reported for the four primary sub-indices (Ref. 1). Permafrost conditions (Figure 1a) vary considerably throughout the NWT, in large part due to the patterns of ground ice distribution. The sub-index values are generally greatest in the vicinity of the Peel Plateau and southeast toward Great Bear Lake, and low values in the Mackenzie Mountains reflect low ground ice conditions. Terrain conditions (Figure 1b) are highly variable as they incorporate the greatest number of indicators of all the sub-indices, with lower values occurring in the Mackenzie Mountains due to high relief and exposed bedrock, and high values in the Mackenzie Valley where there is thick overburden, low terrain ruggedness, and higher soil organic content. Climate stressors (Figure 1c), based on changes from current conditions (1986-2005) to the near future (2031-2050) (Ref. 1), are generally greater than 0.5 in NWT but are highest on Victoria Island and are also elevated throughout the islands of the Arctic Archipelago within the territory. Most of the climate stress is driven by higher winter temperatures and greater precipitation. Landscape disturbance stressors (Figure 1d) in NWT are relatively low overall and are predominantly due to wildfire potential, however in several arctic and tundra locations, the wildfire potential is zero, thus any landscape stressors are related to human presence disturbances that include all-season roads, pipelines, communities, DEW line sites, and mines.

The CWRIPT as has been applied, estimates the projected vulnerability of water resources to permafrost thaw to 2050 (Ref. 1). Though much of the water resources in the Canadian North are expected to develop enhanced vulnerability, there are several hotspots across large regions of NWT, summarized here according to the ecozones of Canada (Figure 3; Ref. 8). Some of the highest values in Canada are located within the Taiga Plains ecozone, an area extending northwest and south of Great Bear Lake. There are also relatively high values for Victoria and Banks islands within the Northern Arctic ecozone. Comparatively low values in the Taiga Shield and Southern Arctic ecozones, and in mountains of the Taiga Cordillera, Boreal Cordillera, and Tundra Cordillera ecozones, are due to relatively low values of sub-indices for permafrost and terrain characteristics and disturbance stressors.

Figure 2. Spatial distribution of the CWRIPT, which characterizes the vulnerability of water resources to permafrost thaw across northern Canada. Source: Ref. 1, Figure 3.

 

Figure 3. Ecozones of Canada. Source: Ref. 6.

 

Looking around

Compared to the entirety of the CWRIPT domain, NWT has among the highest vulnerability of water resources to permafrost thaw, along with the Hudson Plains ecozone south of Hudson Bay, and portions of the Southern Arctic and Northern Arctic ecozones in Nunavut (Figures 2 and 3). Whereas high CWRIPT values for Baffin Island are mainly attributed to nationally-high climate stressors (Figure 1), high values in NWT are predominantly due to high sub-index values of permafrost and terrain conditions and landscape disturbance (Figure 1), which is similar to the Taiga Shield ecoregion of northern Québec and Labrador (Figures 1, 2 and 3).

The CWRIPT is a first-order, informed estimate of water resource vulnerability to permafrost thaw. This exercise benefitted from the recent development of ground ice maps for Canada (Ref. 9), which significantly improves the estimate of the sensitivity of water resources to permafrost thaw. It is difficult to directly evaluate the model due to the scarcity of large-scale data for water resource change. However, within NWT, several recent studies have linked changes in water resources to permafrost thaw in locations with medium to high CWRIPT values. Areas with high permafrost sub-index values match up with areas of high retrogressive thaw slump density and changes in water chemistry in northern mainland Northwest Territories and portions of Banks and Victoria islands (Ref. 10). However, intensification of permafrost thaw on slopes, primarily by retrogressive thaw slumping, has been coupled with hydrological networks, and new mapping results show the potential propagation of water quality effects across NWT drainage networks (Ref. 3). There are documented water chemistry changes associated with catastrophic lake drainage in the Tuktoyaktuk Coastlands (Ref. 11, Ref. 12). In southern NWT, the Scotty Creek watershed has some of the highest CWRIPT values in the country and is dominated by high terrain characteristic sub-index values. Permafrost is associated with peat plateaus that are decreasing in extent (Ref. 13), which has resulted in increasing hydrological connectivity, regional runoff ratios, and annual streamflow (Ref. 4, Ref. 14). It has been hypothesized that increased winter baseflow observed throughout NWT may be linked to better-connected groundwater pathways with permafrost thaw (Ref. 15). This correlates well to the terrain characteristics sub-index (Ref. 1).

 

Looking forward

The general pattern shown in Figure 2 is the expected vulnerability of water resources via permafrost thaw into the middle of the 21st century. This informed estimate is likely to change as new data becomes available (e.g., climate model refinements, improved ground ice maps, updated maps of land cover fraction or human presence, more detailed data on soil organic carbon content, etc.) or as new field data are used to inform and improve the ranking scheme. Although there is great difficulty developing national-scale datasets, this challenge may be mitigated if new or improved input data sets were developed specifically for the territory alone as the CWRIPT scales to the input data. Regardless, in the medium term, it is most likely that the climate-related indictors will require adjustment as climate models are updated. Utilizing these updated climate stressors alone will keep the CWRIPT as a relevant, first-order estimate of changing water resource vulnerability to permafrost thaw in NWT.

 

Find out more

For a complete description of The Canadian Water Resource Vulnerability Index to Permafrost Thaw (CWRVIPT) please visit https://www.nrcresearchpress.com/doi/pdf/10.1139/as-2019-0028

A summary of how permafrost thaw is transforming watersheds in northern NWT is available here: https://www.ecc.gov.nt.ca/sites/ecc/files/resources/128-cimp_bulletin_37_en_proof.pdf based on Marsh, P., E. Wilcox, and N. Weiss. 2020. Collapsing permafrost is transforming Arctic lakes, ponds, and
streams. The Conversation. https://theconversation.com/collapsing-permafrost-is-transforming-arctic-
lakes-ponds-and-streams-128519

Please also see Focal Points Water, Landscape Changes, Vegetation, and Wildlife for more detailed information on these specific aspects of the environment of the NWT.

 

References

Ref. 1.  Spence, C., Norris, M., Bickerton, G., Bonsal, B.R., Brua, R., Culp, J.M., et al. 2020. The Canadian Water Resource Vulnerability Index to Permafrost Thaw (CWRVIPT). Arct. Sci. 6: 437-462. doi:10.1139/as-2019-0028.

Ref. 2.  White, D., Hinzman, L.D., Alessa, L., Cassano, J., Chambers, M., Falkner, K., et al. 2007. The arctic freshwater system: changes and impacts. J. Geophys. Res.: Biogeosci.112: G04S54. doi:10.1029/2006JG000353.

Ref. 3.  Kokelj, S.V., Kokoszka, J., van der Sluijs, J., Rudy, A.C.A., Tunnicliffe, J., Shakil, S., et al. 2021. Permafrost thaw couples slopes with downstream systems and effects propagate through Arctic drainage networks, The Cryosphere Discuss. [in press], doi:10.5194/tc-2020-218.

Ref. 4.  Connon, R.F., Quinton, W.L., Craig, J.R., and Hayashi, M. 2014. Changing hydrologic connectivity due to permafrost thaw in the lower Liard River valley, NWT, Canada. Hydrol. Processes 28: 4163–4178. doi:10.1002/hyp.10206.

Ref. 5.  Derksen, C., Burgess, D., Duguay, C., Howell, S., Mudryk, L., Smith, S., et al. 2019. Changes in snow, ice, and perma-frost across Canada. In Canada’s changing climate report. Edited by E. Bush and D.S. Lemmen. Government of Canada, Ottawa, Ont., Canada. Chapter 5, pp. 194–260.

Ref. 6.  Zhang, Y., Chen, W., and Riseborough, D.W. 2008. Transient projections of permafrost distribution in Canada during the 21st century under scenarios of climate change. Global Planet. Change 60: 443–456. doi:10.1016/j.gloplacha.2007.05.003

Ref. 7.  Bush, E., Gillett, N., Bonsal, B., Cohen, S., Derksen, C., Flato, G., et al. 2019. Executive summary: Canada’s climate change report. Environment and Climate Change Canada, Ottawa, Ont., Canada. 17 p.

Ref. 8.  Canadian Council on Ecological Areas (CCEA). 2014. Ecozones of Canada. https://ccea-ccae.org/ [Accessed 3 June 2021].

Ref. 9.  O'Neill, H.B., Wolfe, S.A., and Duchesne, C. 2019. New ground ice maps for Canada using a paleogeographic modelling approach, Cryosphere 13: 753–773. doi:10.5194/tc-13-753-2019.

Ref. 10. Kokelj, S.V., Lantz, T.C., Tunnicliffe, J., Segal, R., and Lacelle, D. 2017. Climate-driven thaw of permafrost preserved glacial landscapes, northwestern Canada. Geology 45: 371–374. doi:10.1130/G38626.1

Ref. 11. Marsh, P., Russell, M., Pohl, S., Haywood, H., and Onclin, C. 2009. Changes in thaw lake drainage in the Western Canadian Arctic from 1950 to 2000. Hydrol. Processes 23: 145–158.

Ref. 12. Deison, R., Smol, J.P., Kokelj, S.V., Pisaric, M.F., Kimpe, L.E., Poulain, A.J., et al. 2012. Spatial and temporal assessment of mercury and organic matter in thermokarst affected lakes of the Mackenzie Delta Uplands, NT, Canada. Environ. Sci. Technol. 46: 8748–8755. doi:10.1021/es300798w.

Ref. 13. Quinton, W.L., Hayashi, M., and Chasmer, L.E. 2011. Permafrost-thaw-induced land-cover change in the Canadian subarctic: implications for water resources. Hydrol. Processes 25: 152–158. doi:10.1002/hyp.7894.

Ref. 14. Connon, R.F., Quinton, W.L., Craig, J.R., Hanisch, J., and Sonnentag, O. 2015. The hydrology of interconnected bog complexes in discontinuous permafrost terrains. Hydrol. Processes 29: 3831–3847. doi:10.1002/hyp.10604

Ref. 15. St. Jacques, J.M., and Sauchyn, D.J. 2009. Increasing winter baseflow and mean annual streamflow from possible permafrost thawing in the Northwest Territories, Canada. Geophys. Res. Lett. 36: L01401. doi:10.1029/2008GL035822.