Arctic, The

I

Introduction

Arctic, The, large, cold area around the North Pole. The Arctic is not a clearly defined area: it includes the Arctic Ocean, many islands, and parts of the mainlands of the continents of North America, Asia, and Europe.

Scientists define the Arctic in three major ways—firstly, as the area north of the Arctic Circle (latitude 66°33’ North); secondly, as the region north of the 10° C (50° F) summer isotherm—on a map a line drawn through locations with an average annual temperature of 0° C (32° F) or less and a mean temperature for the warmest summer month of 10° C (50° F); thirdly, as the region north of the tree line (on a map, a line connecting points beyond which trees do not grow). The second and third definitions enclose roughly the same territory, which is somewhat larger than the region bounded by the Arctic Circle; it is this larger region that is used as the basis for this article.

The largest Arctic land areas are in Canada, Russia, Greenland (Kalaallit-Nunaat), mainland Scandinavia, Iceland, Alaska in the United States, and the Svalbard archipelago and other islands.

II

The Natural Environment

Unlike Antarctica, an ice-covered continental plateau surrounded by oceans, the Arctic has a central ocean almost enclosed by land. One large gap exists between Greenland and Scandinavia, and there are much smaller breaks among the Canadian Arctic Islands and at the Bering Strait, which separates Alaska and Siberia.

The principal geological elements of the Arctic include parts of three ancient land masses, or shields, composed predominantly of granite and gneiss—the Baltic-Scandinavian-Russian Shield; the Angara Shield or Siberian Platform in north-central Siberia; and the Canadian Shield, including all the Canadian Arctic except for the Queen Elizabeth Islands. Several regions, including most of Greenland, are permanently ice covered. Extensive coastal plains edge much of northern Siberia, parts of the north-western mainland and islands of Canada, and the North Slope of Alaska. There are mountain ranges in the eastern Arctic region of Canada, notably on Baffin Island; in Canada's Yukon Territory; in northern Alaska; in coastal Greenland; in Iceland; and in north-eastern Siberia.

A

Rivers and Lakes

Low precipitation is characteristic of the Arctic, so large and elaborate river and lake systems are rare. In many places, however, permafrost (permanently frozen subsoil) restricts the downward drainage of meltwater from snow, and the water accumulates on the surface as shallow lakes, ponds, and marshes. In addition, rivers from more humid regions flow seaward across the dry Arctic terrain. There are several large rivers, including the Ob, the Yenisey, and the Lena, in the Russian Arctic; the Mackenzie and Yukon rivers are in North America.

B

Climate

Winter in the Arctic is long and cold; summer is short and cool. The Arctic Circle marks the border of a zone in which the Sun never rises above the horizon during at least one day in winter and never sets during at least one day in summer. The number of days of “midnight sun” or continuous night increases northwards. Latitude determines the length of daylight and also influences climate, although maritime and other influences mean that the climate of nearby areas can contrast sharply. For instance, on the Greenland ice cap average midwinter temperatures are -33° C (-27.4° F), while adjacent coastal settlements, where the climate is moderated by relatively warm ocean currents, typically have a mean temperature of -7° C (19.4° F) during the same period. The North Pole is not the coldest spot in the Arctic, because its climate is moderated by the ocean. Oymyakon, in north-eastern Siberia, holds the record low temperature of -68° C (-90.4° F). The coldest recorded temperature for North America is -65° C (-85° F), at Snag, in the Yukon Territory. The characteristically low precipitation averages less than 250 mm (10 in) a year, the moisture being received as snow or rain in almost all locations. Despite their distance from industrialized areas, the polar regions are sometimes blanketed by a smog-like haze. Another environmental effect, often associated with global warming, is an excessive glacier and ice melt (which in 2002 reached a record 685,000 sq km/265,000 sq mi).

See also Aurora; Polar Zone.