DISEQUILIBRIUM RESPONSE OF PERMAFROST IN BOREAL CONTINENTAL WESTERN CANADA TO CLIMATE-CHANGE

In the boreal forest of continental western Canada, permafrost is rest ricted to Sphagnum-dominated peatlands on which air photo interpretati on reveals the occurrence of five types of surface physiography. Conce ntrated in the northern part of the boreal forest, permafrost is prese nt in peat plateaus with and without collapse scars. In the southern p art of the boreal forest, continental bogs dominate, representing ombr otrophic peatlands that have never contained permafrost. In the mid-bo real zone, internal lawns are present in bogs and in fens. These inter nal lawns do not presently contain permafrost but did in the recent pa st, representing degradation of permafrost since the Little Ice Age. E valuation of the distribution of these peat landforms indicates that t oday 30% of bogs contain permafrost at the -0.4 degrees C isotherm and 50% of bogs contain permafrost at the -1.2 degrees C isotherm, wherea s in the past, 30% of bogs contained permafrost at the -1.4 degrees C isotherm and 50% of bogs contained permafrost at the -2.3 degrees C is otherm. Although spatial degradation has occurred with a shifting of p ermafrost northwards in response to warming since the Little Ice Age, permafrost cover has increased in any given area where present-day tem peratures are between 0.5 and -3.5 degrees C.