This indicator tracks changes in thermokarst aerial extent in selected areas of the NWT.
Increases in the aerial extent of thermokarst are detected using various remote sensing techniques including sequential analyses of aerial photographs13 or high resolution satellite imagery12. Remote sensing technology using interferometric satellite radar to track ground surface subsidence has been developed by Canada Centre for Remote Sensing at NRCan19. This technique, which can detect seasonal and annual vertical displacement of even a few centimetres, can be used to monitor natural permafrost environments or built infrastructure .
Information for this indicator can be obtained from an NRCan database with general information on the distribution of landsliding in the Mackenzie Valley1,5. Future changes in landsliding and thaw slumping can now be tracked using a recent baseline landslide inventory5,13. There are limited data on thermokarst in peatlands2, again with the focus primarily within the Mackenzie Valley.
|Thermokarst: Land surface 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 retrogressive thaw slumps to develop.|
Retrogressive thaw slump, Mackenzie Delta region. Photo by T. Lantz, UBC.
Thermokarst disturbances can impact infrastructure, and therefore determining sensitive environments and rates of thermokarst activity are critical to planning development and infrastructure monitoring.
Thermokarst can impact aquatic systems by modifying drainage pathways, causing lakes to rapidly drain or conversely to increase their size and depth (See photographs for 1950 and 2004 in figure below). Degrading permafrost can also change water quality conditions and impact the structure and functioning of both terrestrial and aquatic ecosystems in the NWT10,16,20.
Current view: status and trend
There are few longitudinal studies of thermokarst in the NWT2,8. These studies show that the rates and extent of collapsed peatlands and retrogressive thaw slumping has increased over the last half of the 20th century. Disturbance such as fire can have a dominant impact on thermokarst processes at a local scale .
It is reasonable to predict continued and larger scale modification of terrestrial and aquatic ecosystems as the result of permafrost degradation due to climate warming.
Map of the retrogressive thaw slumps in the upland tundra study region east of the Mackenzie River Delta (Lantz and Kokelj, 200813). Areas bounded by a single line represent study plots where disturbances were mapped on aerial photographs taken in 1950, 1973 and 2004. The study plots affected by the 1968 fire are marked by a border of two solid lines.
Data from satellites may be used to evaluate landscape change in the NWT3,7,17. There is potential to assess the distribution of thermokarst landscapes and select representative areas for longer-term change detection monitoring. Validation of results can be facilitated with targeted ground data collection. It is most ideal to establish keystone monitoring areas in sensitive terrain areas within various ecoregions, with focus on areas for which historical remotely sensed data exists.
Example trend images for three retrogressive thaw slumps within the Peel Plateau region (top) with recent SPOT imagery (bottom) and an air photo (top right) show for reference. From Fraser et al. 20147.
A number of investigations in Alaska and northern Alberta and Manitoba have examined the evolution of thermokarst landscapes. Results from these studies all indicate an increase in the aerial extent of thermokarst features. Studies mapping permafrost degradation in Alaska have focused on describing the impacts on forested landscapes18 and ice wedges11 and tundra polygons9 and elsewhere in the Canadian North on peatland degradation4, thaw slumping12 and stream drainage patterns6. Researchers are investigating the effects of slumping on tall shrub ecology14,15.
Find out more
- For a complete analysis on historical aerial photographs13 to examine rates of slump growth in the Mackenzie Delta region over the past 50 years.
- Aquatic impacts of slumping are described in this scientific presentation www.nwtgeoscience.ca10.
- Impacts of slumping on macrophyte and invertebrate abundance are described in this scientific presentation16.
Other focal points
- For more indicators related to landscape, see the Focal Point LANDSCAPE CHANGES.
- For more indicators related to plants, see the Focal Point VEGETATION.
Thawing of ice-rich permafrost in headwall of an active slump (photo by Stephen Wolfe, NRCan).
Found an error or have a question? Contact the team at NWTSOER@gov.nt.ca.
Ref. 1. Aylsworth J.M., A. Duk-Rodkin, T. Robertson, and J.A. Traynor. 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, pp. 167-176.
Ref. 2. Beilman, D., and S.D. Robinson. 2003. Peatland permafrost thaw and landform type along a climatic gradient. In: Proceedings of the Eight international Conference on Permafrost (Vol 1)., M. Philips, S.M. Springman, and L.U. Arenson, Eds., A.A. Balkema, Swets & Zeitlinger, Lisse, The Netherlands, pp. 61-66.
Ref. 3. Brooker, A., R.H. Fraser, I. Olthof, S.V. Kokelj, and D. Lacelle. 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. In Press.
Ref. 4. Camill, P. 2005. Permafrost thaw accelerates in boreal peatlands during late-20th Century climate warming. Climatic Change 68: 135-152.
Ref. 5. Couture, R. and S. Riopel. 2008. Landslide Inventory along a Proposed Gas Pipeline between Inuvik and Tulita, Mackenzie Valley, Northwest Territories Geological Survey of Canada, Open File 5740, 19pp.
Ref. 6. Fortier, D., M. Allard, and Y. Shur. 2007. Observation of rapid drainage system development by thermal erosion of ice wedges on Bylot Island, Canadian Arctic Archipelago. Permafrost and Periglacial Processes 18: 229-243.
Ref. 7. Fraser, R.H., I. Olthof, S.V. Kokelj, T.C. Lantz, D. Lacelle, A. Brooker, S. Wolfe, and S. Schwarz. 2014. Detecting Landscape Changes in High Latitude Environments Using Landsat Trend Analysis: 1. Visualization. Remote Sensing 6: 11533-11557.
Ref. 8. Hayley D.W., and B. Horne. 2008. Rationalizing climate change for design of structures on permafrost: a Canadian perspective. 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. 681-686.
Ref. 9. Jorgenson M.T., Y.L. Shur, and E.R. Pullman. 2006. Abrupt increase in permafrost degradation in Arctic Alaska. Geophysical Research Letters 33: L02503.
Ref. 10. Kokelj, S.V., R.E. Jenkins, D. Milburn, C.R. Burn, and N. Snow. 2005. The influence of thermokarst disturbance on the water quality of small upland lakes, Mackenzie Delta Region, Northwest Territories, Canada. Permafrost and Periglacial Processes 16: 343-353.
Ref. 11. Kokelj, S.V., T.C. Lantz, S.A. Wolfe, J.C. Kanigan, P. Morse, and C.R. Burn. 2014. Ice-wedge development and degradation across the tree line of western Arctic tree line, Canada. Journal of Geophysical Research: Earth Surface 119: 2032-2047.
Ref. 12. Lantuit, H. and W.H. Pollard. 2005. Temporal stereophotogrammetric analysis of retrogressive thaw slumps on Herschel Island, Yukon Territory. Natural Hazards and Earth System Science 5: 413-423.
Ref. 13. Lantz, T.C. and S.V. Kokelj. 2008. Increasing rates of retrogressive thaw slump activity in the Mackenzie Delta region, N.W.T. Canada. Geophysical Research Letters 35: L06502.
Ref. 14. Lantz, T.C., P. Marsh, and S.V. Kokelj. 2013. Recent shrub proliferation in the Mackenzie Delta uplands and microclimatic implications. Ecosystems 16: 47-59.
Ref. 15. Lantz, T.C., S.V. Kokelj, S.E. Gergel, and G.H.R. Henry. 2009. Relative impacts of disturbance and temperature: persistent changes in microenvironment and vegetation in retrogressive thaw slumps. Global Change Biology 15: 1664-1675.
Ref. 16. Mesquita, P.S., F.J. Wrona, and T.D. Prowse. 2008. Effects of retrogressive thaw slumps on sediment chemistry, submerged macrophyte biomass, and invertebrate abundance of upland tundra lakes. 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. 1185-1190.
Ref. 17. Olthof, I. and R.H. Fraser. 2014. Detecting Landscape Changes in High Latitude Environments Using Landsat Trend Analysis: 2. Classification. Remote Sensing 6: 11558-11578.
Ref. 18. Osterkamp, T.E., L. Viereck, Y. Shur, M.T. Jorgenson, C. Racine, A. Doyle, A. and R.D. Boone. 2000. Observations of thermokarst and its impact on boreal forests in Alaska, U.S.A. Arctic, Antarctic and Alpine Research 32: 303-315.
Ref. 19. Short, N., C.W. Stevens, 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. 20. 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.