Polar desert

Polar deserts are areas with annual precipitation less than 250 mm (9.8 in) and a mean temperature of less than 10 °C (50 °F) during the warmest months. Polar deserts on Earth cover nearly 5,000,000 km² (1,900,000 sq mi) and consist primarily of hard bedrock or gravel plains.

Polar deserts are one of two polar biomes: polar deserts and Arctic tundra. These biomes are located at the poles of the earth, specifically, the Arctic, northernmost North America, Europe, and Asia, and Antarctica. Polar deserts are located in the Arctic and Antarctic. Unlike the tundra that can support plant and animal life in the summer, polar deserts are barren with permanent layers of ice. However, there is evidence of life in this seemingly inhospitable environment.The thick ice contains sediments of organic and inorganic substances which create a habitable environment for microbial organisms. These organisms are closely related to cyanobacteria which have a variety of functions, particularly, fixing carbon dioxide from the melting water.

Temperature changes in polar deserts frequently cross the freezing point of water. This "freeze-thaw" alternation forms patterned textures on the ground, as much as 5 m (16 ft) in diameter (as seen in the picture on the right).

Most of the interior of Antarctica is polar desert, despite the thick ice cover. Conversely, the McMurdo Dry Valleys of Antarctica, although they have had no ice for thousands of years due to katabatic wind, are not necessarily polar desert.

Polar deserts are relatively common during ice ages, as ice ages tend to be dry.

Climate scientists have voiced concerns about the effects of global warming to the ice poles in these polar biomes.