Implications of climate change for northern Canada: the physical environment.

The physical environment of the Canadian North is particularly sensitive to changes in climate because of a large concentration of cryospheric elements including both seasonal and multiyear forms of freshwater and sea ice, permafrost, snow, glaciers, and small ice caps. Because the cryosphere responds directly to changes in air temperature and precipitation, it is a primary indicator of the effects of climate variability and change. This article reviews the major changes that have occurred in the recent historical record of these cryospheric components at high latitudes in Canada. Some changes have been less pronounced in the Canadian North than elsewhere, such as changes in sea-ice coverage, whereas others have been potentially more significant, such as ablation of the extensive alpine and high-Arctic small glaciers and ice caps. Projections of future changes are also reviewed for each cryospheric component. Discussion about two other physical components of the North intrinsically linked to the cryosphere is also included, specifically: i) freshwater discharge to the Arctic Ocean via major river networks that are fed primarily by various forms of snow and ice, and ii) the related rise in sea level, which is strongly influenced by ablation of the cryosphere, and coastal stability, which also depends on the thermal integrity of coastal permafrost.