Ninth International Conference on Permafrost ... - IARC Research

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 t(Harris 2007). Along the Arctic coast, changes in surfacecover from snow to soil and water enhance the effects ofany warming.Almost all stations indicate a decrease in the SFI, thisbeing most marked at Summit Lake. This appears to indicatea weakening of the air pressure north of the 60 th parallel,resulting in warmer air and the associated jet stream movingfurther north as far as Summit Lake from its previous positionfurther south (see also Nkemdirim & Budikova 2001). ThecP air mass is thinner and moves further east rather thanswinging south along the mountain frontFigure 3. Ground temperature changes at 320 cm depth after thelowering of the adjacent water table, Tuchitua.Figure 4. Changes in maximum annual ground temperature a n dactive layer, as measured on a yearly basis (A) and on a daily basis(B).The Summit Lake site showed a spectacular increaseof 4.85°C in MAAT between 1982 and 1994 followed byrelative stability. The SFI decreased by 40% while the STIincreased by 50%. In about 1992, large thaw-flow slidesappeared on the hill slopes at 1200 m elevation, and thesestarted to appear up to 1400 m by 2004. The active laterthickness increased from 1.5 m in 1982 to >5 m in 2007.The warming decreases southwards to Jasper, where thereis only a minor increase in MAAT (0.6°C in 27 years). SFIhas decreased considerably as has the mean annual snowfall,but the STI has increased. South to Calgary, the MAAT hasremained unchanged with both STI and SFI decreasing (seealso Clark et al. 2000).Plateau Mountain exhibited a decrease in MAAT from1974 until 1990, but has been fairly stable since then. Boththe SFI and STI decreased. The active layer has decreased inthickness, and the upper part of the permafrost has cooled inresponse to these changes (Fig. 4).CausesThe first obvious result is that the climatic changes arelocal rather than global. In the main mass of the mountainsof Alaska and Yukon, inversions of air with their associatedcloud cover, steam fog in the fall when the air temperatureover lakes is lower than the water temperature, and cold airdrainage serves to buffer the valleys from climatic changesAcknowledgmentsRoger J.E. Brown of the Building Research Division,National Research Council of Canada funded the originalstudy. It has also been funded in some years by the GeologicalSurvey of Canada (Alan Heginbottom and Sharon Smith) andNSERC operating Grant A-7483. Parks Canada, Alberta, andBC Parks kindly provided the necessary collecting permits.ReferencesAES. 1993. CD-Rom of the climatic data collected by theAtmospheric Environment Service at CanadianWeather Stations.Anisomov, O.A. & Poliakov, V.Yu. 2003. GIS assessment ofclimatic change impacts in permafrost regions. ICOP2003, Permafrost (1): 9-14.Clarke, J.S., Yirode, E.K., Burns, N.D. & Astatkie, T.,2000. Regional climate change: trend analysisand precipitation series at selected Canadian sites.Canadian Journal of Agricultural Economics 48: 27-38Harris, S.A. 2007. Reaction of continental mountain climatesto the postulated “global warming,” evidence fromAlaska and the Yukon Territory. Earth Cryosphere11(3): 78-84 (in Russian).Kershaw, G.P. 2003. Permafrost landform degradation overmore than half a century, MacMillan/Caribou Passregion, NWT/Yukon, Canada. ICOP 2003, Permafrost(1): 543-548.Lewkowicz, A.G. 2003. Palsa dynamics in a subarcticmountainous environment, Wolf Creek, YukonTerritory, Canada. ICOP 2003, Permafrost (1): 163-168.Nkemdirim, L.C. & Budikova, D. 2001. Trends in sealevel pressure across western Canada. Journal ofGeophysical Research 106(D11): 11801-11812.Osterkamp, T.E. & Romanovsky, V.E. 1999. Evidence forwarming and thawing of discontinuous permafrostin Alaska. Permafrost and Periglacial Processes 10:17-37.94