ABSTRACT: Permafrost in a warming world: better soil modeling with class new land surface scheme from 1961 to 2100.

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Abstract

Short and mid term predictions at local and regional scales could be quite challenging for permafrost modelers. In the context of climate change, northern parts of Canada are already experiencing general permafrost degradation, affecting in particular local populations and infrastructures, but could also lead to a complete set of positive feedbacks related to vegetation distribution, snow cover, soil organic carbon and fresh water discharge for example. To better understand and predict the evolution of the thermal and moisture regimes of permafrost, it is necessary to use advance modeling tools such as the Canadian Land Surface Scheme (CLASS, Verseghy 1991, Verseghy et al. 1993) and the Canadian Regional Climate Model (CRCM, Laprise 2008). Compared to the operational version of CLASS actually in the CRCM, that has only three layers (0.1, 0.25 and 3.75m) and allows only sand and clay soil con?guration, the latest version of CLASS is now more optimized to realistically simulate permafrost dynamics. First, its ?exible layering scheme resolves the active-layer thickness and allows deep soil con?guration (e.g., 100m), the latest being more suitable for long simulations reaching the end of the 21st century. Second, its new organic matter soil parametrization can now re?ect typical thermal and hydraulic properties involved in organic soils present in northern latitudes. With these new available features, it is proposed, as ?rst step, to do 1-D of?ine tests on typical northern Quebec locations with CLASS forced by the A2 climate change scenario simulated by the CRCM from 1961 to 2100. The second step will involve online simulations on a grid covering North America. Preliminary results seem to con?rm that adding deeper layers and organic matter to CLASS brings a new thermal inertia that changes the active-layer and near-surface permafrost behavior, with the major effect of delaying the permafrost degradation compared to shallow soil model used in most operational climate models.

Bibliography of Canadian Geomorphology