Antarctica is the largest desert in the world, a fact that often surprises people who picture a hot, sandy landscape. This misconception stems from conflating the defining characteristic of a desert with its temperature. The continent at the South Pole perfectly meets the scientific criteria for a desert due to its extreme lack of moisture. Recognizing Antarctica as the world’s largest desert requires focusing on the single most important factor in desert classification: aridity.
Defining the Desert Classification
The scientific classification of a desert is based almost entirely on the level of aridity, measured by annual precipitation, not temperature. A region is formally classified as a desert if it receives less than 250 millimeters (or 10 inches) of precipitation, measured as water equivalent, over the course of a year. This low threshold means the environment is so dry it can only support sparse vegetation and limited life.
This definition allows for both hot deserts, such as the Sahara, and cold deserts, which include the polar regions. Temperature is only used to sub-classify deserts, distinguishing between hot and cold types. The fundamental concept is that deserts are defined by a severe lack of moisture, regardless of whether that moisture is absent due to high evaporation or low precipitation.
In arid environments, the rate of potential evapotranspiration—the amount of water that could evaporate or be transpired by plants—greatly exceeds the actual precipitation received. This constant moisture deficit is the unifying factor that links all deserts. A desert is fundamentally an arid land, not necessarily a hot one.
Antarctica’s Extreme Aridity
Antarctica qualifies as a textbook example of a “Polar Desert” due to its profound aridity. The continent receives an average of only about 166 millimeters (6.5 inches) of water equivalent precipitation annually. This low figure is well below the 250-millimeter threshold required for desert classification.
The interior of the continent is dramatically drier than the coast. Central regions often record less than 50 millimeters (2 inches) of precipitation per year, placing them in the hyper-arid category, which rivals the driest hot deserts. The minimal precipitation that falls almost exclusively comes in the form of snow or ice crystals.
The extreme cold is the primary reason for this aridity, as cold air holds very little water vapor. This limits the moisture in the atmosphere above Antarctica, severely restricting the potential for snowfall. Furthermore, the continent is dominated by high-pressure systems and katabatic winds. These gravity-driven, cold, dense air masses flow downhill and suppress moisture influx.
The existence of an ice sheet covering 98% of the continent appears paradoxical given its desert status. However, the ice mass is a result of accumulation over millions of years, not high present-day precipitation. Temperatures are so consistently low that the small amount of snow that falls does not melt or evaporate, allowing it to slowly compress and build up over geologic time.
Comparing Global Deserts and Size
Antarctica’s classification as the largest desert is confirmed by its sheer scale and verified aridity. The continent covers approximately 14 million square kilometers (5.4 million square miles). This makes it the single most expansive arid region on the planet.
The second largest desert, the Arctic Polar Desert, spans about 13.7 to 13.9 million square kilometers, covering northern regions like Greenland, Canada, and Russia. Both are classified as cold deserts, defined by low temperatures and low precipitation.
In comparison, the largest hot desert, the Sahara, covers about 9.2 million square kilometers (3.5 million square miles) across North Africa. Antarctica is nearly twice the size of the Sahara, securing its place as the world’s largest desert.
Deserts are categorized into several types based on their geographic location and dominant climate features, including polar, subtropical, cool coastal, and cold winter deserts. Antarctica is a prime example of a polar desert. The continent’s vast size and extremely low precipitation rate solidify its position as the world’s largest and driest desert.