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Vital Arctic Graphics

Introduction page 2

The Living Arctic – the last unexploited marine and land areas on Earth?

The world’s largest remaining intact ecosystems

Figure 1. Boundaries of the Arctic. Several definitions of the Arctic as a region exist and are all used extensively.

Definitions of the geographic boundaries of the Arctic vary, including such definitions as the area with a July isotherm below 10º C, vegetation distribution (tundra) or political boundaries, such as the definition by CAFF (CAFF, 2001). Nowhere else on Earth do we find such vast areas of relatively undisturbed marine and coastal ecosystems.

From drift ice and coastal plains to rugged mountains

Figure 2. Topography and bathymetry of the Arctic.

The Arctic is extremely diverse in terms of landscapes, varying from pack and drift ice to rugged shores, flat coastal plains, rolling hills and mountains surpassing 6000 metres above sea level (Denali, 6,194 m asl, in sub-arctic and boreal Alaska). The region has rivers and lakes, tundra and the largest forests in the world (the Russian Taiga).

Covered in ice and snow for most of the year

Figure 3. Permafrost distribution in the Arctic.

Most of the Arctic is covered by ice and snow for more than eight and even up to twelve months a year, but conditions are highly variable, ranging from snow several metres deep each winter to the polar deserts of northern Greenland with only 50- 100 mm of precipitation annually. A large portion of the Arctic is underlain by permafrost. Permafrost, defined as ground that does not thaw for two or more years, can reach a thickness of up to 1000 metres, as it does on the North Slope of Alaska. It extends through as much as 50% of Canada and 80% of Alaska (Clark, 1988). During summer, the top centimetres, sometimes down to several metres, thaw, resulting in unique geomorphological phenomena such as thermokarst, frost mounds, highand low-centred polygons, earth hummocks (thufur), palsas and pingos. The latter are mounds up to 45 metres high with slopes as steep as 45 degrees and massive ice cores covered by a thin layer of soil. Such frost phenomena create crucial topographic diversity in otherwise flat coastal plains and impact snow ablation, nutrient cycles, and vegetation characteristics. They are crucial to foraging and insect relief habitat for caribou (Nellemann and Thomsen, 1994), as well as nesting habitat for numerous bird species. In fact, since snow provides insulation against the severe cold of winter, even minor topographic relief has major implications for vegetation distribution and nutrient cycling, and therefore for both plants and wildlife.