ARKTOS

TO THE ANCIENT GREEKS, the Arctic was the realm of Boreas, god of the north wind, and the region where the celestial sphere of northernmost stars was always visible. They called this place Arktos, meaning "bear," alluding to the Great Bear and Little Bear constellations, Ursa Major and Ursa Minor.

There are many myths and legends about these groups of stars. Greek mythology relates that the bear constellations are the spirits of the nymph Callisto, the reluctant concubine of the god Zeus, and their son, Arcas. Zeus changed the pair into stars and placed them in the heavens, where they are tended by Arcturus, the bear guard, who faithfully follows them around the night sky.

The brightest stars of the bear constellations form the Big and Little Dippers, so named for their resemblance to ladles. At the end of the Little Dipper's handle is the bright triple star Alpha Ursae Minoris, known to us as Polaris, the North Star. Polaris marks the point of due north and has a seemingly fixed position in the arctic sky. The Inuit call it Nuuttuittuq, the star that never moves, and the Finns call it the North Nail.

DEFINING THE ARCTIC

THE ARCTIC is the region of land and ocean that centers roughly on the North Pole and extends southward to and beyond the Arctic Circle. It is a place of exaggerated seasonality with brief, cool summers and long, dark, icy winters. This vast wilderness, also known as the Far North, encompasses the Arctic Ocean, the world's largest island (Greenland), and parts of eight countries: the United States (Alaska), Canada, Denmark (Greenland), Iceland, Norway, Sweden, Finland, and Russia.

The Ancient Greek astronomers were the first to define the Arctic's boundaries. They based their conclusions on observations of the celestial sphere, an imaginary shell surrounding the earth. They believed that the stars and other celestial bodies were fixed on the inside surface of the sphere, as if it were the underside of a dome. It is easy to understand how the early astronomers came to this belief, for if one steps outside on a clear, starry night and looks up, the constellations appear to be set on a dome that surrounds the earthbound observer, who is standing in the middle of it. The stars seem to slowly rotate from east to west — an illusion caused by the earth's rotation.

Aristotle (384–322 BC) noted in his treatise Meteorology that some stars were always visible to an observer at a particular location and that these always-visible stars could be used to mark standard reference circles on the celestial sphere and earth. A short time later, in his essay Phenomena, Euclid hinted that astronomers had used Aristotle's hypothesis to approximate the position of the North Celestial Pole (the imaginary point where earth's axis of rotation meets the celestial sphere) as well as the celestial equator, tropics, and Arctic Circle.

In the first century BC, Greek Stoic philosopher Posidonius applied his observations of solar phenomena to define a precise boundary for earth's northernmost region. He proposed that the Arctic be delimited by a circle of fixed size, located 24° south of the North Celestial Pole. This put Posidonius's circle at 66°N latitude, a location nearly identical to the position of the present- day Arctic Circle at 66°33'N.

Today, the Arctic Circle is commonly used by political administrators, geographers, and cartographers to mark the Arctic's southern boundary and it also provides travelers a point to celebrate their entry into the Arctic. More importantly, the Arctic Circle marks the northernmost point at which the sun is visible on the northern winter solstice, around December 21, and the southernmost point at which the midnight sun can be seen on the northern summer solstice, around June 21.

Scientists have many other words and ways to define the Arctic. Biologists often use the term Holarctic, which comprises the Palearctic (Old World) and Nearctic (New World) regions combined. The two regions have been linked intermittently by the Bering Land Bridge and their flora and fauna are closely related.

Climatologists and ecologists tend to use the Köppen climate classification system to delimit the arctic zone. The system, which is based on the concept that native vegetation is the best expression of climate, was first proposed in 1884 by Russian-German meteorologist, climatologist, and botanist Wladimir Köppen (1846–1940).

Köppen's system defines the arctic zone as the area enclosed by the 10°C July isotherm — a line connecting points where the average temperature for the warmest month of the year, usually July, does not exceed 10°C (50°F). The position of the 10°C July isotherm fluctuates between 62°N and 70°N latitudes and roughly parallels the boreal treeline, the northern limit of tree growth. The arctic tundra lies to the north of the 10°C July isotherm and the boreal forests and taiga lie to the south.

The map on pages 12–13 shows the approximate location of the 10°C July isotherm, the treeline, and the bioclimatic zones, including the Polar Desert, High Arctic, Low Arctic, Boreal Forest, and Taiga. Color-coded sidebars list some plant and animal species associated with each zone. Much of the information presented on the map was adapted from the Circumpolar Arctic Vegetation Map compiled by the Alaska Geobotany Center at the University of Alaska Fairbanks.

Polar Desert

Land is mostly barren and dry, with permanently frozen subsoil. Sites with more sun and moisture bear a thin cover of lichens, mosses, bryophytes, low grasses, and a few wildflowers such as saxifrages, poppies, and heaths.

Typical wildlife includes polar bears, arctic hares, lemmings, rock ptarmigans, snowy owls, and ivory gulls. Mean July temperature is 32°–37°F (0°–3°C).

High Arctic Tundra

Permafrost underlies the tundra, which bears a highly uneven cover of mosses, lichens, dwarf willows, scurvygrass, and wildflowers such as avens, saxifrage, and lousewort.

Typical wildlife includes muskoxen, arctic foxes, wolves, stoats, caribou, eiders, gyrfalcons, snow buntings, and red-throated loons. Mean July temperature is 37°–45°F (3°–7°C).

Low Arctic Tundra

Permafrost underlies the tundra, which bears a discontinuous cover of sedges, rushes, sphagnum moss, lichens, dwarf willow, dwarf birch, sorrel, crowberry, buttercups, and many other wildflowers.

Typical wildlife includes caribou, arctic ground squirrels, ravens, and a variety of nesting waders and waterfowl. Mean July temperature is 45–54°F (7–12°C).

Taiga/Boreal Forest

An irregular band of forest-tundra with groves of spruce, larch, pine, poplar, dwarf birch, willow, and tundra flowers occurs along the southern edge of the tundra. South of this is a parallel zone of...