Modeled current and future soil thermal regime for northeast Canada

摘要

Deepening of the active layer (i.e., the seasonally thawed layer overlying permafrost) was noted since the beginning of the 1990s in northern Canada, which has already caused substantial environmental and socioeconomic consequences. There is a strong consensus among projections of climate models used to study anticipated climate changes on the rise of the global average temperatures over the next century, with maximal changes being projected for high-latitude cold regions such as the permafrost regions. Given these projections, an evaluation of changes in the soil thermal regime becomes desirable for a number of reasons including assessments of possible ecosystem responses and impacts on man-made infrastructures. Such an evaluation of changes in the soil thermal regime for northeastern Canada is presented in this paper using a one-dimensional heat conduction model. Projected changes are estimated as the difference between two simulations of the soil model corresponding to the IPCC IS92a future scenario (2041–2070), which has effective CO2 concentration increasing at 1% per year (2041–2070), and current (1961–1990) climates. The surface temperature and snow cover from time series of transient climate simulations with the Canadian Regional Climate Model (CRCM) are used to drive the soil model. Results suggest significant warming trends in the annual mean, maximal and minimal near-surface soil temperatures, with the mean annual soil surface temperature increasing by 3°–6°C for the continuous permafrost zone and by 2°–4°C for the rest of the permafrost zones in northeastern Canada. Results also suggest significant deepening of the active layer for the period 2041–2070, with its thickness increasing by more than 50% for most of the continuous permafrost region.