C6. Permafrost and high-latitude hydrology changes in future climate

One of the most important features of the Canadian high-latitudes is permafrost. Till recently, climate models, both global and regional, were not capable of simulating near-surface permafrost. This was mostly due to the limitation that GCMs and RCMs employ land-surface schemes that vary in depth between 3 and 10 meters. Such shallow model configurations, though coupled, cannot simulate active-layer and permafrost processes realistically due to the shallow depths and the zero flux lower boundary condition, which can degrade considerably the quality of the simulated soil thermal and moisture regimes. Offline studies, using simple heat-conduction models (Sushama et al., 2006) did show that significant degradation of permafrost can result from climate change and it is important to implement interactive permafrost in climate models, to capture the two-way interactions between land and atmosphere. By early 2009, the new version of CLASS (Verseghy, 2008) that is particularly suitable for permafrost studies due to its more flexible layering scheme and bottom boundary conditions became available. This version of CLASS is now implemented in CRCM5 and the RCM is now able to simulate near-surface permafrost interactively. Other important aspects of the high latitudes are the presence of lakes and wetlands, which controls many aspects of the land surface water balance in the region. The hydrologic effects of lakes and wetlands are still neglected in climate models. It is proposed here to improve representation of river-lake/wetland/permafrost connectivity in climate models. The improved model will further be used to study the influence of lakes/wetlands/permafrost on the spatial and temporal distribution of water and energy fluxes in current and future climates.

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