The polar climate zone, designated as Group E in the Köppen climate classification system, is the coldest climate region on Earth. It is defined by persistently frigid conditions and a complete absence of warm summers. For a region to be classified as polar, the average temperature of its warmest month must remain below 10°C (50°F).
This low-temperature threshold means polar zones cannot support the growth of trees, marking the treeline boundary. Covering over 20% of the planet’s surface, these environments are characterized by long, dark winters and short, cool summers. The pervasive cold limits nearly all life forms in this high-latitude climate.
Defining Characteristics of Polar Climates
The defining feature of the polar climate is the low angle of solar radiation, which results in minimal energy input even during the sunniest months. Sunlight strikes the surface obliquely, spreading energy over a larger area. This requires the light to travel through more atmosphere, leading to greater absorption and scattering. This low solar angle ensures that average monthly temperatures never exceed the 10°C (50°F) benchmark.
The Earth’s axial tilt causes extreme variations in daylight hours, creating the phenomena of polar day and polar night. During the summer, the poles experience the “midnight sun,” where the sun remains above the horizon for 24 hours, though the indirect angle prevents significant warming. Conversely, winter brings the “polar night,” resulting in months of near or total darkness and the coldest temperatures.
Despite the large amount of ice and snow, polar climates are surprisingly dry and are often classified as polar deserts. The frigid air holds very little moisture, leading to extremely low annual precipitation, frequently less than 250 millimeters (10 inches). Precipitation typically falls as small ice crystals or snow, and the persistent cold prevents melting and evaporation, maintaining the icy landscape.
Global Distribution of Polar Regions
The vast majority of the polar climate is found in the high latitudes surrounding the North and South Poles, generally above 60° latitude. The Arctic Region encompasses the Arctic Ocean and the northern coastal areas of North America, Europe, and Asia. Large landmasses within the Arctic, such as most of Greenland, also fall under this climate designation.
The Antarctic Region, consisting of Antarctica, represents the largest continuous zone of polar climate on Earth. Unlike the Arctic, Antarctica is a landmass covered by a massive, miles-thick ice sheet, contributing to its status as the coldest place on the planet. Similar conditions are also found in high-altitude environments, known as alpine tundra, which experience the same low temperatures and treeless conditions due to elevation.
The Major Subtypes of Polar Climate
The Köppen system divides the polar climate group (E) into two primary subtypes based on the severity of the cool season. This distinction is based on whether summer temperatures rise above the freezing point of water, which profoundly affects the landscape and life it supports. The two subtypes are the Tundra Climate (ET) and the Ice Cap Climate (EF).
The Tundra Climate (ET) is defined by having at least one month with an average temperature above 0°C (32°F), but below the polar limit of 10°C (50°F). This brief summer thaw allows the top layer of soil, called the active layer, to melt. The underlying ground remains perpetually frozen in a layer known as permafrost.
The active layer and the short growing season support low-lying vegetation like mosses, lichens, grasses, and dwarf shrubs. Since water from melted snow and ice cannot drain through the permafrost, the terrain often becomes soggy and marshy during the summer. This climate is characteristic of the coastal fringes of the Arctic and many subantarctic islands.
The Ice Cap Climate (EF) represents the most severe climate type, characterized by perpetual winter. In this subtype, the average temperature of every month remains below 0°C (32°F). This means accumulated snow and ice never melt, leading to the formation of permanent ice sheets and glaciers that can be thousands of meters thick.
Ice cap climates are dominant over the interiors of Antarctica and Greenland. Due to the unrelenting cold and ice cover, these areas are completely devoid of vascular vegetation. The coldest recorded temperatures on Earth, such as the low of −89.2°C (−128.6°F) at Vostok Station, are found within this extreme climate zone.