Antarctica is the coldest, highest, and windiest continent on Earth, largely covered by a massive, permanent ice sheet. Despite the ice and snow, the continent is scientifically classified as a polar desert. This designation is driven not by the lack of heat, but by an extreme lack of moisture, or aridity.
Defining Aridity and Desert Classification
The classification of a geographic area as a desert is primarily based on the amount of precipitation it receives annually, not its temperature. Aridity, the defining characteristic of a desert, is determined by a severe imbalance between precipitation and the potential for water loss through evaporation and transpiration (evapotranspiration). An area is classified as a desert if it receives less than 250 millimeters (about 10 inches) of precipitation per year.
Potential evapotranspiration refers to the amount of water that could evaporate if it were constantly available. In hot deserts, high temperatures cause extremely high potential evapotranspiration, rapidly drying the landscape. In cold deserts like the polar regions, low temperatures reduce potential evaporation, but the overall lack of moisture still meets the strict aridity criteria.
Applying the Desert Criteria to Antarctica
Antarctica overwhelmingly meets the precipitation criteria to be classified as a desert, even though moisture falls almost entirely as snow. The average annual precipitation across the continent is only about 150 millimeters (six inches) of water equivalent. This places it well below the 250-millimeter threshold required for desert classification.
Aridity is most pronounced in the vast interior, specifically the high Antarctic Plateau. This region receives the least moisture, with annual precipitation often measuring less than 50 millimeters (two inches) of water equivalent. Such extreme dryness places the interior in the “hyperarid” category, a designation shared with the driest parts of the Sahara Desert.
Coastal areas are generally wetter, with some sections receiving over 200 millimeters of precipitation annually. However, these totals remain low enough for the continent as a whole to be considered a desert. The low temperatures ensure that the small amount of snow that falls rarely melts, leading to the gradual buildup of the massive ice sheet.
Distinguishing Antarctica From Tundra Biomes
Confusion between Antarctica and a tundra biome arises because both are polar environments characterized by extreme cold. The fundamental distinction, however, lies in their capacity to support biological life and their underlying soil structure. Tundra biomes, primarily found in the Arctic, are defined by permafrost—soil that remains frozen year-round—but with a thin, active surface layer that thaws during the brief summer.
This seasonal thawing allows the Arctic tundra to support a continuous, low-growing layer of vegetation, including mosses, lichens, grasses, and dwarf shrubs. The short growing season is sufficient for these plants to anchor themselves and photosynthesize. Antarctica, by contrast, lacks this widespread biological activity and stable soil structure.
The entire Antarctic continent, apart from small, ice-free areas, is covered by a massive, permanent ice sheet. This means a thawing soil layer is nonexistent in most places. The combination of extreme cold and hyperaridity prevents the establishment of the continuous vegetation cover characteristic of a tundra, classifying the landmass as a polar desert.
Ecology of the Polar Desert
The ecology of the Antarctic polar desert is a direct consequence of its hyperarid and frigid climate, resulting in an extremely sparse terrestrial ecosystem. Most life is concentrated in coastal areas or in the few ice-free regions, such as the McMurdo Dry Valleys. Terrestrial plant life is limited exclusively to non-vascular organisms like mosses, liverworts, and lichens, which survive in a dehydrated state and only metabolize when moisture is available.
Microbes represent the most abundant life form, with certain species of cyanobacteria living endolithically within porous rocks. These organisms remain dormant for extended periods, becoming active only when melting snow provides the necessary liquid water. Larger, more visible animal life, such as seals and penguins, relies entirely on the biologically rich surrounding Southern Ocean, not the land, for food.