Soil temperature response to 21st century global warming: the role of and some implications for peat carbon in thawing permafrost soils in North America

Northern peatlands contain a large terrestrial car- bon pool that plays an important role in the Earth's carbon cy- cle. A considerable fraction of this carbon pool is currently in permafrost and is biogeochemically relatively inert; this will change with increasing soil temperatures as a result of climate warming in the 21st century. We use a geospatially explicit representation of peat areas and peat depth from a recently-compiled database and a geothermal model to esti- mate northern North America soil temperature responses to predicted changes in air temperature. We find that, despite a widespread decline in the areas classified as permafrost, soil temperatures in peatlands respond more slowly to increases in air temperature owing to the insulating properties of peat. We estimate that an additional 670 km 3 of peat soils in North America, containing 33 Pg C, could be seasonally thawed by the end of the century, representing 20 % of the total peat volume in Alaska and Canada. Warming conditions re- sult in a lengthening of the soil thaw period by 40 days, averaged over the model domain. These changes have poten- tially important implications for the carbon balance of peat soils.