Arctic and Subarctic Regions

The region encircling the North Pole is called the Arctic Circle, an invisible circle of latitude (imaginary line around the Earth parallel to the equator) at 66°33' North. The arctic region sits inside the Arctic Circle and the subarctic region lies just below it. Earth's arctic and subarctic regions are extremely cold, icy areas of land and sea that receive almost no sunlight during their long, dark winters. Temperatures rarely rise above freezing. This is true even during summer in the "land of the midnight sun." The Sun's rays hit the poles at a very shallow angle and the summer sunlight—while long-lasting—is too weak to provide much heat. Arctic and subarctic regions, however, support diverse groups of land and marine (ocean) plants and animals, including humans that have learned how to survive in their harsh climates.

Water, both frozen and liquid, plays a vital role in arctic and subarctic environments. Arctic ice cools warm ocean currents and generates cold deep ocean water. Deep, cold currents flowing south from the Arctic Ocean distribute nutrients and control temperatures in the Atlantic and Pacific Oceans. The permanent covering of ice over its large area is called the Arctic ice cap. The Arctic ice cap helps to regulate Earth's temperature by reflecting sunlight. Global sea level and ocean water chemistry change when the amount of glacial ice (large masses of moving ice) on the northern continents and islands changes. The North Pole lies under a zone of dry, sinking air in the atmosphere (mass of air surrounding Earth), and the Arctic and is a windblown, frozen desert that receives very little snow each year (it almost never rains there because it is too cold).

Geography of the Arctic

A ring of continental land masses and large islands surrounds the ice-covered Arctic Ocean over the North Pole. The far northern portions of Asia (Russia, Siberia), Europe (Scandinavia) and North America (Canada, Alaska) lie within the Arctic Circle. Large islands extend even farther north: Nova Zemlya (Russia), Spitsbergen (Norway), Iceland, Greenland (Denmark), and the Queen Elizabeth Islands (Canada). Treeless plains called tundra cover the arctic and subarctic zones between the edge of cool, snowy, northern forests (boreal forests) and the coastlines of the Arctic Ocean.

Arctic ice

Sea ice covers the entire Arctic Ocean in the winter. It surrounds many of the Arctic islands and merges with glaciers and ice shelves (thick ice tht extends out from the land over water) along the edges of the continents. Huge, floating slabs of ice called pack ice crack and buckle as they constantly readjust to winds and currents. In the spring, the ice begins to melt back toward the North Pole. It breaks into large chunks of ice called icebergs and fleets of icebergs float in the open ocean. (Some icebergs, including the infamous 1912 sinker of the cruise ship Titanic, float south into "iceberg alley" in the North Atlantic Ocean where they are a hazard to shipping.) In the summer, the Arctic ice cap melts toward the pole. Fish, whales, and other ocean species travel north to feed and mate in nutrient-rich open waters along the Arctic coastlines.

Sea ice makes up most of the Arctic ice cap. However, glacial ice covers many of the Arctic islands, including the almost continent-sized island of Greenland. The thick ice that covers about 80% of Greenland is the last remnant of massive ice sheets that covered much of North America, Europe, and Asia during the Ice Ages of the Pleistocene era (starting 1.6 million years before the present and ending about 10,000 years ago). Ironically, Greenland is very icy and not particularly green, while neighboring Iceland is green and not particularly icy. (Warmth from Iceland's volcanoes melts ice and supports grasslands).

Life on the tundra

In spite of its harsh climate, the subarctic tundra supports a wide range of biological species. No trees grow on the tundra because a layer of frozen soil beneath the top layer of soil, called permafrost, prevents them from taking root. The tundra is also relatively dry; it receives only a few inches (centimeters) of precipitation (rain, snow, and any other form of water) each year. Strong winds sweep away snow and dry the soil.

The tundra has only a few year-round residents. The birds (ptarmigan) and mammals (lemmings, hares, foxes, wolves, muskoxen, polar bears, and humans) there exhibit a number of traits that allow them to survive the cold, dark winter: thick, fluffy fur or feathers that turn white in winter and brown in summer offer camouflage that insulates them from the cold; hibernating to conserve energy; and strategies for finding shelter in the snow. Some species, including lemmings, drastically reduce their population by committing mass suicide during lean times. Polar bears and humans venture onto the pack ice in winter and early spring to hunt for seals, sea lions, whales, and fish.

The tundra comes to life in late spring when the pack ice begins to retreat and the permafrost thaws. Birds and mammals travel north to join those that stayed for the winter. They feed on insects, shallow-rooted grasses and shrubs, lichens (plants that grow on bare rock), bird eggs, other animals, and especially marine life. Birds nest on the tundra. Herd animals like caribou travel north from the boreal forests of Asia, Europe, and North America to graze and bear their young. Wolves, foxes, eagles, and humans hunt the plains. In fall, when the sea ice reforms and the ground freezes solid, most of the birds and animals fly, swim, or walk south while the permanent arctic residents stock up for the long, dark, cold winter.

Permafrost

Permafrost is a soil or rock layer that has remained below freezing (32°F or 0°C) for two or more years. Frozen groundwater in the open spaces of permafrost turns layers of loose silt or sand into solid rock. Permafrost beneath the tundra in the sub-arctic zone is hundreds of feet (meters) thick and has been frozen for thousands of years. There are thinner, less long-lived permafrost layers beneath the northern forests of Asia, Europe, and North America and in high mountain ranges. In total, permafrost underlies about one-quarter of the land surface in the Northern Hemisphere.

In spite of its name, permafrost is not always permanent. Even slight heating can thaw portions of the permafrost. Each summer, water in the upper few feet of arctic and subarctic permafrost melts for a few months. Shallow-rooted tundra shrubs and sedges grow quickly, and produce new seeds before the winter cold refreezes the ground. Permafrost is a problem for the engineers who build roads, buildings, and pipelines in the tundra. Permafrost melts when heat from engines or furnaces escapes into the ground, and structures sink or collapse when the ground turns to soupy mud or quicksand beneath them. Scientists are concerned that a small rise in Earth's average temperature could greatly affect the arctic and subarctic environment by melting the permafrost.

Humans in the Arctic

Arctic humans, like polar bears, survive the winter by insulating themselves. in warm fur and eating fatty seal meat. Eskimo tribes of Siberia, Arctic North America, and Greenland live in snow shelters, hunt the tundra, and use boats called kayaks to fish the icy Arctic waters. Native residents of Arctic Siberia and Alaska today prefer to be called Inuit, which means "the people." The term Eskimo has come to represent an over-simplified image of Eskimos as fur-clad hunters that live in igloos instead of a diverse group of loosely-related arctic cultures that have their far-northern latitude in common.

Laurie Duncan, Ph.D.

For More Information

Books

Arms, Myron. Riddle of the Ice: A Scientific Adventure into theArctic. New York: Anchor Books, 1999.

Pielou, E.C. A Naturalist's Guide to the Arctic. Chicago: University of Chicago Press, 1995.

Websites

"State of the Cryosphere." National Snow and Ice Data Center.http://nsidc.org/sotc (accessed on August 17, 2004).

"The Tundra." Radford College Virtual Geography Department. Introduction to Biomes by Susan L. Woodward.http://www.radford.edu/~swoodwar/CLASSES/GEOG235/biomes/tundra/tundra.html (accessed on August 17, 2004).