Ninth International Conference on Permafrost ... - IARC Research

Potential Use of Rock Glaciers as Mountain Permafrost Indicators inYukon Territory, CanadaAmaris PageDepartment of Geography, University of Ottawa, Ottawa, CanadaAntoni LewkowiczDepartment of Geography, University of Ottawa, Ottawa, CanadaIntroductionPanya LipovskyYukon Geological Survey, Whitehorse, CanadaJeff BondYukon Geological Survey, Whitehorse, CanadaAnalysis of the distribution of active rock glaciers iswidely accepted as a way to establish the lower boundaryof mountain permafrost. Rock glaciers have been used inthis capacity for modeling probable permafrost distribution,mainly in Europe (e.g., Imhof 1996, Lambiel & Reynard2001, Frauenfelder 2005, Etzelmüller et al. 2007, Fukui etal. 2007, and others). All of these models have examinedpermafrost distribution over relatively small areas.We are beginning a similar project in Canada’s YukonTerritory. A key difference from previous research is thespatial extent over which the study is being conducted.Currently the distribution of rock glaciers and their activitystatus are being examined in the southern half of the territory,an area of approximately 250,000 km 2 .A second difference between this and the Europeanresearch is that in North America, rock glacier distributionmay represent only the lower limit of high elevationpermafrost. Permafrost also occurs in lower elevation valleybottoms due to a combination of temperature inversionsdue to cold air drainage (Lewkowicz & Ednie, 2004), andecological interactions associated with surface hydrology.This situation does not occur in Europe, where rock glacierdistribution can be used to model the full extent of permafrostin mountainous areas.Our broad goal is to use the distribution of rock glaciersas an independent means of testing mountain permafrostprobability models. This abstract focuses on potentialsources of information and current knowledge of rock glacierdistribution.MethodologyRock glacier location data for this research will be derivedmainly from the Yukon Geological Survey’s surficial geologymaps (see Fig. 1 for map coverage). Rock glacier origins andactivity status will be determined by examining their morphologyon aerial photographs and remotely sensed imagery.Rock glaciers will be classified as active, inactive, or relict.Their distribution will be assessed at various scales andthe usefulness of the rock glaciers for determining probablepermafrost distribution in southern Yukon will be evaluated.A sub-sample of the rock glacier population will be visitedand their origins and activity status verified in the field.Figure 1. Study area showing surficial geology map coverage (white)and distribution of known rock glaciers (black dots) in the YukonTerritory. According to Heginbottom et al. (1995) discontinuouspermafrost becomes continuous at about 64°45′N in this region.Approximately 1650 individual rock glaciers have beenidentified to date on maps at scales of 1:25,000 to 1:250,000,which cover roughly 75% of the Territory south of 65°N (thezones of discontinuous permafrost in the Yukon). Verificationthat the complete population has been mapped will beundertaken for selected areas using aerial photographs.An indication that the maps may not show all the features,possibly because of differences in scale, is that Sloan andDyke (1998) state that more than 1100 rock glaciers arepresent in the Selwyn Mountains alone.Rock glacier density, elevation, and aspect will be comparedin different parts of the Territory. Figure 1 shows that thereis considerable variation in density with most rock glaciersconcentrated in the NW- to SE-trending Selwyn Mountains,Pelly Mountains and Kluane Ranges. Densities in theseareas can reach 1 rock glacier per 4 km 2 . Extraction of other243