Geographically and in terms of human occupations the Arctic is best defined as the area north of the tree line, which is also the southernmost limit of tundra. In the New World this huge region extends some 11,000 kilometers from the Aleutian Islands in the west to Greenland and Labrador in the east.
In terms of geomorphology the Arctic includes high mountains, sedimentary plain, exposed bedrock, and lowlands, most of it with little or no soil development. For humans the winter landscape also includes the frozen sea ice. In Alaska, Greenland, and Labrador this is often a wide strip of landfast ice along the coast. However, in the central portion of the Canadian Arctic Archipelago the channels between islands freeze completely for much of the year.
Some other attributes that characterize the Arctic environment include persistence of cold (long winters and short cool summers), tundra with permafrost (year-round frozen ground), large seasonal differences in amount of sunlight, and a very limited range of plant foods usable by humans.
The most important terrestrial species in this region include caribou, musk-ox, arctic fox and arctic hare, while the most important marine and lacustrine resources include seal, walrus, whale, polar bear, and arctic char.