Ninth International Conference on Permafrost ... - IARC Research

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Historic Change in Permafrost Distribution in Northern British Columbia andSouthern YukonMegan JamesDepartment of Geography, University of Ottawa, Ottawa, CanadaAntoni G. LewkowiczDepartment of Geography, University of Ottawa, Ottawa, CanadaSharon L. SmithGeological Survey of Canada, Natural Resources Canada, Ottawa, CanadaPanya LipovskyYukon Geological Survey, Whitehorse, CanadaIntroductionAs a largely climatically-controlled phenomenon,permafrost conditions are impacted by air temperature andprecipitation, as well as other local surface and subsurfacefactors (Smith & Riseborough 1996, 2002). Numerousstudies have shown that permafrost should diminish inextent with rising air and ground temperatures (ACIA 2004).However, most of these predictions are based on modeling,and there are very few field-based studies of long-termpermafrost change in Canada.The objective of this study is to directly evaluate the impactof recent climate change on permafrost distribution. We wereable to conduct it due to the availability of early baselinepermafrost data, which are rare in Canada. In August 2007,we repeated a 1964 permafrost survey undertaken by the lateRoger Brown along the Alaska Highway from Whitehorse,YT, to Fort St. John, BC (Brown 1967).Study AreaIt is difficult to demonstrate climate change impactson permafrost except in very cold permafrost, wheretemperatures can rise without much thaw, or in areas of verywarm and shallow permafrost, where it may thaw completely(Smith et al. 2005). Even warm, shallow permafrost, likethat found in the study area, can take several decades to thawbecause far more heat is required for phase change than forwarming (Smith et al. 2005).Brown’s sites traverse discontinuous permafrost designatedas sporadic (underlying 10–50% of the landscape) or isolatedpatches (underlying 0–10%) (Heginbottom et al. 1995),which can be expected to be the most sensitive to climatechange, because a small change in temperature can resultTable 1. MAATs of communities along the study transect.Community Latitude Longitude Normal MAAT(1971–2000)Whitehorse, YT 60°42′ N 135°04′ W -0.7°CWatson Lake, YT 60°72′ N 128°49′ W -2.9°CFort Nelson, BC 58°50′ N 122°36′ W -0.7°CFort St. John, BC 56°14′ N 120°44′ W 2.0°C(Environment Canada 2007b)in a transition from a cryotic to a thawed state (Kwong &Gan 1994). According to Smith and Riseborough (2002), thesouthern limit of discontinuous permafrost approximatelycoincides with a mean annual air temperature (MAAT) of-1ºC. Table 1 shows the MAATs of the principal communitiesalong the study transect east of Whitehorse.MethodsBrown described the 60 locations that exhibitedpermafrost in 1964, as well as some nonpermafrost sites, insuch sufficient detail that it was possible to relocate mostof them using milepost information, written descriptions,and photographs. This information was retrieved fromBrown’s 1967 publication, as well as from cartographic andphotographic material archived at the National ResearchCouncil of Canada. The research was conducted in themonth of August so that the depth of the thawed layer wouldbe near its maximum.Using UTM coordinates for Brown’s sites, derived fromarchived 1965 Alaska Highway maps, we drove along theroute until we were within 500 m of the coordinates for a siteand continued for 500 m past. We assessed the landscape oneither side of the highway until we could confidently matchBrown’s photographs and descriptions. At some locationswe had to examine an area several hundred metres aroundthe UTM coordinates and look for sites most likely to havepermafrost (based on vegetation and drainage), which wewould investigate. There were several sites that we wereunable to relocate due to inadequate descriptions or profoundchanges in land cover, such as conversion of spruce forestto farm fields. At each relocated site, 2 ground temperatureprofiles were measured to 1.5 m or until we encountered thefrost table. At sites where a frost table was found, 10 groundprobings, roughly 1 m apart, were performed to measureactive layer thickness.Further information on ground thermal conditions willbe obtained from six climate stations which were set up tomeasure air temperature, ground temperatures, and snowdepths in order to examine the conditions that have allowedpermafrost to endure. These data will be downloaded insummer 2008.115
Ni n t h In t e r n at i o n a l Co n f e r e n c e o n Pe r m a f r o s tResultsThe results of this survey demonstrate that significantchange has occurred in the last four decades. More thanhalf of the positively located sites which had permafrostin the upper 1.5 m in 1964 along the route as a whole nolonger exhibited perennially frozen ground in 2007, and thiswas true of almost three-quarters of the sites in the routesegment to the south of Fort Nelson, BC. In addition, wherepermafrost was still extant in the upper 1.5 m, active layerson average were deeper than in 1964, even though the surveywas undertaken one month earlier in the thaw season.Climate data show that Brown’s survey in 1964 followedroughly 20 years of cooling, especially at Whitehorse (Fig.1). This cooling continued for another decade, and there wasthen a rapid rise in temperatures. Changes in active layerthickness and permafrost extent observed during the 2007revisiting of Brown’s sites would have been the result of this1.5–2.0°C rise in temperature over the past 30 years, as wellas any change in precipitation quantities and patterns.Discussion and ConclusionPreliminary results suggest that the boundaries of thepermafrost zones may have moved substantially northwardssince Brown undertook his survey. These results fit withwhat would be expected given the concurrent air temperaturechange. However, precipitation is also an importantcomponent of climate, and snow depth and duration aresignificant local factors affecting the ground temperatureregime (Smith & Riseborough 1996, 2002). Little is currentlyknown about the snow conditions at the sites, but the climatestations installed in 2007 should reveal relationships betweenair temperatures, ground temperatures, and snow depths.Mean Annual Air Temperature (°C)5.04.03.02.01.00.0-1.0-2.0-3.0-4.01943y = 0.0007x 2 - 0.024x + 1.50R 2 = 0.17195319631973Yeary = 0.0013x 2 - 0.067x - 0.26R 2 = 0.18Figure 1. MAATs of Whitehorse, YT (the x line) and Fort St. John,BC (the “diamond” line) from 1943–2007 (Environment Canada2007a). The dashed lines are the long-term MAATs over the timeperiod, and the solid black lines are polynomial lines.198319932003In August 2008, data will be downloaded from the sixclimate stations and a combination of geophysical techniquesand direct drilling will be used to establish current permafrostthicknesses and to install ground temperature cables. Thisinformation will be combined with spatial analysis of ahighway borehole database on permafrost that is currentlybeing developed at the Yukon Geological Survey.This study is a step towards filling a research void toprovide evidence of loss of permafrost on a multidecadalscale. Careful archiving of information about the researchsites should allow repetition of the survey by futuregenerations of permafrost researchers, thus contributing tothe legacy of the <strong>International</strong> Polar Year.AcknowledgmentsSupport for this project has been provided by the FederalGovernment of Canada’s <strong>International</strong> Polar Year Program(Thermal State of Permafrost in Canada), the NSERCNorthern Internship Program, the Northern Student TrainingProgram, DIAND, and the Yukon Geological Survey.Catherine Henry provided field assistance.ReferencesArctic Climate Impact Assessment (ACIA). 2004. Impactsof a Warming Climate. New York: CambridgeUniversity Press, 139 pp.Brown, R.J.E. 1967. Permafrost Investigations in BritishColumbia and Yukon Territory. Division of BuildingResearch Technical Paper 253. Ottawa: NationalResearch Council of Canada.Environment Canada. 2007a. Canadian Climate Data.http://climate.weatheroffice.ec.gc.ca/climateData/canada_e.html.Environment Canada. 2007b. Canadian Climate Normalsor Averages 1971–2000. http://climate.weatheroffice.ec.gc.ca/climate_normals/index_e.html.Heginbottom, J.R., Dubreuil, M.A. & Harker, P.T. 1995.Canada Permafrost. (1:7,500,000 scale). In: TheNational Atlas of Canada, 5 th Edition, sheet MCR4177. Ottawa: National Resources Canada.Kwong, Y.T. & Gan, T.Y. 1994. Northward Migrationof Permafrost along the Mackenzie Highway andClimatic Warming. Climatic Change 26(4): 399-419.Smith, M.W. & Riseborough, D.W. 1996. Permafrostmonitoring and detection of climate change.Permafrost and Periglacial Processes 7: 301-309.Smith, M.W. & Riseborough, D.W. 2002. Climate and thelimits of permafrost: A zonal analysis. Permafrostand Periglacial Processes 13: 1-15.Smith, S.L., Burgess, M.M., Riseborough, D. & Nixon,F.M. 2005. Recent trends from Canadian permafrostThermal Monitoring Network sites. Permafrost andPeriglacial Processes 16: 19-30.116
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NICOP 2008 Ninth <
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ContentsPreface ...................
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Mapping and Modeling the Distributi
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Satellite Observations of Frozen Gr
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xiiIce Wedge Thermal Regime in Nort
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xivPermafrost Response to Dynamics
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NICOP SponsorsUniversitiesUniversit
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Deep Permafrost Studies at the Lupi
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Effect of Fire on Pond Dynamics in
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Cryological Status of Russian Soils
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Acoustical Surveys of Methane Plume
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Permafrost Delineation Near Fairban
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Preparatory Work for a Permanent Ge
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A Provisional Soil Map of the Trans
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Martian Permafrost Depths from Orbi
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Time Series Analyses of Active Micr
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Impact of Permafrost Degradation on
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DC Resistivity Soundings Across a P
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Modeling Thermal and Moisture Regim
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A Provisional Permafrost Map of the
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Alpine Permafrost Distribution at M
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Cryogenic Formations of the Caucasu
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Modeling Potential Climatic Change
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A Hypothesis: A Condition of Growth
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Modeled Continual Surface Water Sto
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Freeze/Thaw Properties of Tundra So
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Discontinuous Permafrost Distributi
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Thermal Regime Within an Arctic Was
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Seasonal and Interannual Variabilit
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Twelve-Year Thaw Progression Data f
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Continued Permafrost Warming in Nor
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Landsliding Following Forest Fire o
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A Permafrost Model Incorporating Dy
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Seasonal Sources of Soil Respiratio
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Greenland Permafrost Temperature Si
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The Importance of Snow Cover Evolut
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The Account of Long-Term Air Temper
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The Combined Isotopic Analysis of L
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Adaptating and Managing Nunavik’s
Page 86 and 87: Human Experience of Cryospheric Cha
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