The phrase “snow desert” is a descriptive term commonly used to visualize vast, cold, and seemingly endless white landscapes. While evocative, this is not the formal scientific classification used by climatologists and biologists. These frigid biomes are not defined by their perpetually frozen state alone but by a fundamental lack of moisture, a characteristic they share with the world’s hottest, sand-filled deserts. The scientific classification focuses on the mechanism of dryness, making the presence of snow and ice a misleading visual feature of these extremely arid environments.
The Specific Term Polar Deserts
The correct classification for these cold, dry regions is the Polar Desert, a specific subtype of cold desert distinguished by its geography near the Earth’s poles and extremely low precipitation. To be formally classified, a region must receive less than 250 millimeters (about 10 inches) of precipitation annually. This metric aligns with the definition used for hot deserts, establishing that the classification is based strictly on aridity rather than temperature. Additionally, the mean temperature of the warmest summer month must remain below 10°C (50°F). The interior of Antarctica, for example, receives less than 40 millimeters of precipitation per year, making it the world’s driest desert despite being covered in ice.
Defining Aridity in Cold Climates
The primary mechanism driving the intense aridity in polar deserts is the relationship between temperature and the capacity of air to hold water vapor. Extremely cold air holds significantly less moisture than warm air, meaning there is very little water vapor available to form clouds and generate precipitation. Consequently, the snow that falls is often minimal, resembling a light dusting rather than a heavy storm.
The intense cold also promotes sublimation, where accumulated snow and ice convert directly into water vapor, bypassing the liquid phase. This constant loss of frozen moisture contributes to the overall dryness. The combination of minimal atmospheric water vapor and continuous surface ice loss results in a water budget deficit, which defines a desert environment.
Key Characteristics and Global Locations
Polar deserts represent the planet’s largest arid regions, covering approximately 5 million square kilometers globally. The two primary locations are the high Arctic and the vast continent of Antarctica. Antarctica is the single largest polar desert, covering over 14 million square kilometers, and is characterized by a massive continental ice sheet and extremely low biodiversity. In contrast, the Arctic polar desert extends across the northernmost parts of continents like North America, Europe, and Asia, where ice-free areas are often interspersed with tundra.
A distinguishing characteristic of these environments is the widespread presence of permafrost, which is ground that remains frozen for at least two consecutive years. The constant freeze-thaw cycles, often crossing the 0°C threshold, create unique surface features, including patterned textures that can measure up to five meters in diameter. Due to the lack of liquid water, vegetation is sparse, generally consisting of hardy species like mosses, lichens, and algae that cling to the few exposed rock and gravel plains.