Disequilibrium response of permafrost in boreal continental western Canada to climate change

Abstract

In the boreal forest of continental western Canada, permafrost is restricted toSphagnum-dominated peatlands on which air photo interpretation reveals the occurrence of five types of surface physiography. Concentrated in the northern part of the boreal forest, permafrost is present in peat plateaus with and without collapse scars. In the southern part of the boreal forest, continental bogs dominate, representing ombrotrophic peatlands that have never contained permafrost. In the midboreal zone, internal lawns are present in bogs and in fens. These internal lawns do not presently contain permafrost but did in the recent past, representing degradation of permafrost since the Little Ice Age. Evaluation of the distribution of these peat landforms indicates that today 30% of bogs contain permafrost at the −0.4 °C isotherm and 50% of bogs contain permafrost at the −1.2 °C isotherm, whereas in the past, 30% of bogs contained permafrost at the −1.4 °C isotherm and 50% of bogs contained permafrost at the −2.3 °C isotherm. Although spatial degradation has occurred with a shifting of permafrost northwards in response to warming since the Little Ice Age, permafrost cover has increased in any given area where present-day temperatures are between 0.5 and −3.5 °C.