cold desert

cold desert, any large arid area of land that typically receives scant amounts of annual precipitation, which occurs mainly in the form of snow or fog. (The upper limit of mean annual precipitation is often considered to be fewer than 25 cm [9.8 inches]; however, sources vary.) Cold deserts are found typically in temperate regions at high elevations, on plateaus, or in mountainous areas; however, they also occur in polar regions. Shrubs and grasses are the main types of vegetation, and most plants and other organisms have adaptations that enable them to survive the dry, frigid conditions. Cold deserts are located at higher latitudes than deserts situated in tropical and subtropical climates, and thus they experience colder temperatures, especially in the winter. They are found in Central Asia, western North America, southeastern South America, Antarctica, and the Arctic.

Origin and environment

Some cold deserts are located far inland, distant from humid onshore winds, with some of the largest occurring deep within continental interiors. Others, however, are found on the leeward sides of mountain ranges, where they exist in rain shadows—i.e., regions that receive little or no precipitation because humid air driven upslope on the wind-facing (or windward) side of a mountain range releases most or all of its moisture before crossing over the top of the range (see also orographic precipitation). There is considerable overlap in some parts of the world between cold deserts and tundra environments, because both are characterized as typically receiving fewer than 25 cm (9.8 inches) of precipitation annually, both are dominated by longer cold winters whose average temperatures are below freezing, and both are characterized by sparse, scrubby, low-lying vegetation.

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Ecosystems

In contrast, a polar desert is a type of cold desert that is found at very high latitudes in the Arctic and the Antarctic. Like other cold deserts, polar deserts receive very little precipitation. They have short summers, with a mean temperature of less than 10 °C (50 °F) during the warmest month. Winters are long, with temperatures that can fall to −40 °C (−40 °F) or below. Most of the water is frozen in glaciers and ice sheets. Due to the lack of liquid water in polar deserts, few plants and animals can survive there.

Examples of temperate cold deserts

The Gobi Desert, which is located in northwestern China and southern Mongolia, is one of the coldest deserts in the world, with average temperatures ranging from −40 °C (−40 °F) in January to over 45 °C (113 °F) in July. The Gobi Desert occurs in the rain shadow of the Himalayas, so it is extremely dry. The amount of precipitation the desert receives varies from year to year. It ranges from less than 4 cm (about 1.6 inches) in some areas to more than 20 cm (about 7.9 inches) in the Altai Mountains. Some parts of the desert do not receive any precipitation for years. The topography of the Gobi includes many areas of bare rock with few sand dunes. Shrubs and grasses are the predominant vegetation. Animals adapted to live in these harsh conditions include wild Bactrian camels, jerboas, pit vipers, black-tailed gazelles, and snow leopards.

The high-elevation Great Basin Desert is a cold desert in the United States. It covers most of Nevada, the western half of Utah, and parts of other nearby states. The desert occurs within the rain shadow created by the Sierra Nevada mountain range of eastern California. Most of the precipitation in the Great Basin Desert falls as snow. One of the best-known plant species in this region is sagebrush, which has adapted to the dry conditions by using its extensive root system to collect water. Animals found in the Great Basin Desert include bighorn sheep, yellow-bellied marmots, bats, bullfrogs, red-winged blackbirds, and rattlesnakes.

Patagonia, which contains desert and dry steppe areas, is the largest arid region in Argentina, covering most of southern Argentina and a small part of Chile along the eastern side of the Andes Mountains. Its topography varies from valleys and canyons to tablelands and massifs. Snow is rare in the region, and frost often covers the ground during winter. Like the Gobi Desert and the Great Basin Desert, much of the region is located within a large rain shadow. Most of the vegetation here is made up of shrubs and low-lying plants, and the vertebrate fauna includes guanacos, rheas, burrowing owls, pumas, and gray foxes.

Examples of polar deserts

The Arctic polar desert covers the northernmost parts of Canada, the United States (Alaska), Greenland, Iceland, Finland, Sweden, Russia, and Norway (Svalbard) as well as the ice-covered Arctic Ocean. On land, permafrost and snow cover are prevalent. The Arctic hosts a surprising amount of biodiversity, including a variety of vegetation such as mosses, lichens, shrubs, grasses, and flowering plants. Animals that live in the Arctic include polar bears, walruses, Arctic foxes, and several species of seals.

The Antarctic polar desert covers the entire continent of Antarctica and ice-covered parts of the Southern Ocean that surrounds it. Its topography includes flat bedrock and gravel plains as well as mountains. Approximately 98 percent of Antarctica is covered with ice sheets. Bacteria, algae, mosses, lichens, and microorganisms manage to survive here—including psychrophiles, which are extremophile microorganisms that require temperatures below freezing in order to survive; psychrophiles thrive in temperatures as low as −20 °C (−4 °F). Cold-adapted mammals of the Antarctic region include elephant seals and several species of birds, including many types of penguins.