The term “polar desert” may seem paradoxical, but it describes the world’s largest cold biome, a vast region defined by its extreme aridity rather than its temperature. This environment represents a significant portion of the planet’s surface. Unlike the hot, sandy deserts near the equator, polar deserts are cold and often covered in ice, yet they share the defining characteristic of receiving extremely little moisture. This unique blend of freezing temperatures and profound dryness creates one of the most hostile environments on Earth.
Defining the Polar Desert
A polar desert is formally classified based on two main climatic parameters: extremely low annual precipitation and a mean temperature in the warmest month that remains below 50 degrees Fahrenheit (10 degrees Celsius). The annual precipitation in these regions is typically less than 10 inches (250 millimeters), classifying them as arid landscapes. The lack of moisture is exacerbated because the precipitation falls as snow or ice, which remains frozen and biologically unavailable for most of the year.
The vast reserves of ice and snow often conceal a state of severe drought. This phenomenon occurs because the frigid air cannot hold much water vapor, leading to minimal snowfall. Furthermore, the combination of low humidity and high winds causes the frozen moisture to bypass the liquid state entirely, turning directly into vapor through a process called sublimation. This rapid loss means that water is locked away in ice or quickly lost to the atmosphere.
This environment contrasts sharply with hot deserts. In polar deserts, the intense cold limits evaporation, but the aridity is primarily driven by the low capacity of cold air to hold moisture and the physical removal of frozen water by sublimation and wind. The interior of these biomes is characterized by dry, sinking air masses that have already shed their moisture, contributing to the perpetual dryness.
Geographical Distribution
The polar desert biome is distributed across the highest latitudes of the planet, encompassing the majority of the Antarctic continent and large parts of the Arctic. Antarctica is the largest desert globally, covering approximately 5.5 million square miles (14.25 million square kilometers) and is almost entirely classified as a polar desert. The continent holds the distinction of being the coldest, windiest, and driest landmass on Earth.
The Antarctic Polar Desert includes the massive ice sheets and the ice-free areas known as the McMurdo Dry Valleys. The interior plateau of Antarctica is particularly dry, receiving as little as 2 inches (5 centimeters) of water equivalent per year. This extreme dryness is partly due to katabatic winds, dense, dry air currents that sweep down from the high ice plateau, scouring the landscape and removing any surface moisture.
In the Northern Hemisphere, the Arctic Polar Desert covers large areas north of 75 degrees latitude, including most of Greenland and parts of the Canadian Arctic Archipelago, such as Devon Island. Central Greenland’s ice sheet is a notable example, receiving only about 3 inches (8 centimeters) of snow annually. While the Arctic includes the tundra biome, the true polar desert zones are characterized by permanent ice cover or barren gravel plains.
Surviving the Extremes: Life in Polar Deserts
Life in the polar desert is severely constrained by constant sub-zero temperatures, limited liquid water, and high ultraviolet radiation. Macroscopic life forms, such as vascular plants and large animals, are largely absent from the interior regions, which are dominated by bare rock, ice, and snow. The few plants that exist in less severe areas, like the High Arctic, have short growth seasons and adaptations such as a low, cushion-like growth habit to conserve heat and moisture.
The most successful life forms are microorganisms, particularly endoliths. These specialized microbes, including cyanobacteria, algae, and fungi, survive by colonizing the tiny pore spaces inside porous rocks like sandstone. Living beneath the rock surface provides a stable microclimate, offering protection from harsh winds, intense radiation, and temperature fluctuations. The rock interior also traps trace amounts of moisture, making it the only reliable source of liquid water for their metabolic needs.
Larger fauna, such as penguins, seals, and some seabirds, primarily inhabit the coastal fringes rather than the deep, arid interior. These animals are dependent on the nutrient-rich ocean for their food supply, using the land only for breeding or resting. Their survival depends on thick layers of insulating blubber and specialized circulatory systems that conserve core body heat, such as counter-current heat exchange. The scarcity of resources and extreme physical conditions underscore the biological uniqueness of the polar desert.