ABSTRACT: Discontinuous permafrost thaw accelerates in boreal peatlands during late-20th Century climate warming.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Permafrost covers 25$%$ of the land surface in the northern hemisphere, where mean annual ground temperature (MAGT) is less than 0$\deg$C. A 1.4-5.8$\deg$C warming in mean annual air temperature (MAAT) by 2100 will likely change the sign of MAAT and MAGT over most of the zone of discontinuous permafrost in the northern hemisphere, causing widespread permafrost thaw. However, there is little direct evidence documenting the magnitude of high-latitude warming and its impact on permafrost thaw. In this study, I examine rates of discontinuous permafrost thaw in the boreal peatlands of northern Manitoba, Canada, using a combination of tree-ring analyses to document thaw rates from 1941-1991 and direct measurements of permanent benchmarks established in 1995 and resurveyed in 2002. I use instrumented records of MAAT, mean winter snow depth, and duration of continuous snow pack from climate stations across northern Manitoba to analyze temporal and spatial trends in these variables and their potential impacts on thaw. I show that permafrost thaw in central Canadian peatlands has accelerated significantly since 1950, concurrent with a significant, late-20$^{th}$-century average climate warming of +1.39$\deg$C in this region. Projecting current warming trends to year 2100, I show that trends for north-central Canada are in good agreement with general circulation models, which suggest a 4-8$\deg$C warming at high-latitudes. This magnitude of warming will likely eliminate most of the present range of discontinuous permafrost in central Canada by 2100.

Bibliography of Canadian Geomorphology