Permafrost

Permafrost is the term used to describe permanently frozen ground. It is said to underlie from one fifth to one quarter of the world's land. As the melting caused by a warmer climate could release some of the large amounts of methane now locked into the frozen soil, this might add substantially to the concentrations of greenhouse gases in the atmosphere.

The surface layer above the permanently frozen ground can become very mobile during the melt season, making an unstable base for construction. This layer is also vulnerable to melting when built on, driven over, or even walked on. Such traces of human activity remain visible for many years in this delicate environment. A warmer climate might increase the depth of the surface layer.

Mackenzie River Basin

Much of the Mackenzie Basin is underlain by permafrost. This is a particularly interesting part of Canada when we talk about climate change and water supply.

Geographically, it is large; it covers about one sixth of the area of the country. Its settlement pattern is unusual in that the majority of its population and development is located in the upstream part of the basin. Oil and gas and pulp and paper are the main industries. Because the aboriginal inhabitants downstream live almost entirely off the land, a clean and regular water supply is particularly important to them, both for drinking and for the animals they depend on. As well, the rivers are vital transportation links, as routes for boat travel in summer and as ice roads in winter.

Canadian scientists are monitoring the current situation in the Mackenzie Basin to discover possible effects of global warming on northern hydrology, including its impacts on permafrost. They are looking at possible changes in runoff patterns, snow and ice cover, ice jam flooding, water quality, and water levels. Although it is too early for predictions, they suspect that:

• drainage patterns in low-lying areas might change due to the melting of frost sills, which direct or impede water flow;
• water levels in some areas might drop in late summer and autumn due to increased evapotranspiration (with an impact on ecosystems in wetlands, small lakes, and deltas);
• runoff in other areas might increase due to the loss of permafrost;
• an increased sediment load might lead to erosion in some rivers;
• higher temperatures might make some water bodies more productive;
• certain slopes might become unstable and vulnerable to landslides (due to permafrost thaw).

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