ABSTRACT: 1 C scenario-based climate change modelling for a regional permafrost probability model of the southern Yukon and northern British Columbia, Canada.

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Abstract

recently created high-resolution (30 x 30 m) permafrost probability model for the southern Yukon and northern British Columbia covers an area of about 490 000 km^2 between 59 – $65\degN (Bonnaventure et al. In Review). The model was developed by utilizing seven individual empirical-statistical models created within the region using a combination of Basal Temperature of Snow (BTS) and ground truthing inputs (Bonnaventure and Lewkowicz Submitted) and expanded using a blended distance decay technique. The Regional Model shows that 52\% of the region is underlain by permafrost, existing at high elevations but often also within valley bottoms in forest terrain especially in the north of the study region where mountain and latitudinal permafrost begin to interfinger.A unique distinction of this region is the presence of inversions in Surface Lapse Rate (SLR). These inversions can produce gentle or inverted SLRs through the forest on an annual scale, whereas areas above treeline generally follow a normal SLR (-$6.5\degC/km). As a result, this greatly affects the distribution of permafrost, which does not follow a linear trend with elevation as seen in the European Alps. Due to this, one of the models main variables is equivalent elevation, which incorporates non-uniform temperature change with elevation (Lewkowicz and Bonnaventure 2011). By altering this variable within the Regional Model different Mean Annual Air Temperature (MAAT) scenarios can be run to see how permafrost distribution is affected. Because the equivalent elevation variable takes into account an area’s specific SLR below treeline, this perturbed model represents a significant improvement over others, which have used normal SLRs to examine potential climate change. Climate change scenarios for \pm $1\degC have been performed on the Regional Model to examine the effects under equilibrium conditions. Under a -$1\degC colder than present scenario, similar to what temperatures would have been during the little ice age, the area underlain by permafrost expands to 78\%. Under a MAAT scenario of +$1\degC the amount of permafrost area is reduced to 31\%. In areas where SLRs are normal, permafrost zones from isolated patches to continuous can be present in mountain areas over small horizontal distances. Warming of these areas results in the individual permafrost zones progressively moving upward in elevation, while continuous terrain is reduced. In areas however, that have close to zero or inverted SLRs, permafrost is much more sensitive to changes in MAAT. These areas show more uniform lowering of permafrost probabilities with much larger areas being affected and independent of elevation.

Bibliography of Canadian Geomorphology