CGRG Bibliography of Canadian Geomorphology
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Author : Blanchette, J-P.; Sushama, L.; and Laprise, R.
Date : 2008.
Title : Modelling the impact of climate change on thermal and moisture regimes of permafrost with the new deep soil configuration in class.
Publication : International Arctic Change 2008 Conference. December 9-12, 2008. Quebec City, Quebec.
Issue : Conference Programme and Abstracts
Page(s) : 185.
Abstract
Most of the climate models, including Regional Climate Models (RCMs), employ land-surface schemes that vary in depth between 3 and 10 meters; for example the current version of the Canadian Regional Climate Model (CRCM, Laprise 2006) has a physically based land surface scheme, CLASS (Canadian LAnd Surface Scheme; Verseghy et al., 1991, Verseghy, 1993), which is 4.1m deep, with three soil layers that are 0.1, 0.25 and 3.75m thick respectively. As shown by many recent studies (Smerdon and Stieglitz, 2006; Alexeev et al., 2007, Nicolsky et al., 2007, Stevens et al., 2007), such shallow soil models, though coupled, cannot simulate active-layer and near-surface permafrost realistically. For instance, those types of shallow soil models have inappropriate lower boundary condition, which gives rise to a null heat ground flux near the surface. In the context of climate changes, this could have an impact on many positive feedbacks related to the active layer thermo and hydrodynamics; for example, extended snow cover period, snowmelt hydrology, terrestrial albedo, greening period, etc. To simulate realistic soil thermal and moisture regimes in the CRCM, it is intended to use the latest version (v3.4) of CLASS, which is particularly suitable for permafrost studies due to its more flexible layering scheme and bottom boundary conditions. For example, with this new configuration, the soil model can now reach 100m deep and incorporate the geothermal flux at its bottom boundary. It is surely a step towards a greater realism of the energetic balance of permafrost, especially with long simulations reaching the end of the 21st century. Moreover, CLASS is also more realistic in its soil composition. It allows in its parametrization schemes not only clay and sand soil types, but also complete organic ones (Letts et al., 2000), which will contribute to decouple the atmosphere temperature with the ground surface temperature because of the traditionally low thermal conductivity of the organic matter. Sensitivity of the permafrost soil thermal and moisture regimes to organic matter and the soil model depth/configuration is assessed using offline simulations with this latest version of CLASS, which is presented in this study. Preliminary results seem to confirm that adding deeper layers and organic matter to CLASS brings a new thermal inertia that changes the active-layer and near-surface permafrost behavior.
Bibliography of Canadian Geomorphology