Climate, Arctic and Subarctic

The earth's arctic and subarctic climates are located over the highest latitudes of the globe, typically poleward of 50 degrees latitude. Because these climates are located at high latitudes, they are mostly driven by a dramatic seasonal shift of incoming solar radiation. The summer season consists of long daylight hours, while the winter season has long nighttime hours. Locations poleward of 70 degrees have 24 hours of daylight during their respective summers and 24 hours of night during the winter.

Subarctic climates are largely continental and unique to the northern hemisphere, due to the existence of large land masses between 50–70 degrees. Most of Canada and the interior regions of Siberia have subarctic climates, which can be distinguished by the presence of extensive coniferous forests with hardy deciduous trees such as aspen and larch intermixed. A key characteristic of subarctic climates is an annual temperature range greater than any other climate zone on earth. Winters typically have minimum temperatures between −50 and −30 degrees C (−32 and −22 degrees F), while summer maximum temperatures are as warm as 15–25 degrees C (59–77 degrees F). Subarctic climates tend to be moderately dry with total annual precipitation between 30–50 centimeters (12 and 20 inches). Winter snowfall is heavy, ranging from 150–300 centimeters (59–118 inches), with higher amounts occurring over locations near coastal areas such as eastern Canada or eastern Siberia.

Ice cap climates have subfreezing temperatures yearround. Snow pack and ice are permanent features.

Polar climates occur over oceans and land masses typically poleward of 60 degrees latitude. They exist where the warmest month of the year has a mean temperature less than 10 degrees C (50 degrees F). Polar climates exist over the Arctic Ocean, Antarctica, and far northern areas of Asia and North America (including Greenland). Despite perpetual daylight hours during the summer season, the sun's low angle and significant cloudiness (60–90 percent) permits only moderate surface warming. Polar climates have two climate subtypes, tundra and ice cap.

Tundra climates are distinguished by landscapes lacking forests, but covered in flowering plants, moss, lichen, and some shrub species. An additional characteristic for tundra climates is the existence of permafrost, a permanent, impermeable layer of frozen earth below the surface. Summers are short (6–10 weeks) and are defined by daytime temperatures between 0–10 degrees C (32–50 degrees F) providing just a long enough period for snow to melt and the upper layers of soil to thaw. Winter temperatures are cold, but can vary significantly depending on the proximity to certain coasts. Tundra environments in northern Scandinavia have winter minimum temperatures between −10 and −5 degrees C (14–23 degrees F), while in northern Alaska they are between −33 and −28 degrees C (−28 and −18 degrees F). Total snowfall and annual precipitation is slightly lower in tundra climates than in subarctic climates.

Ice cap climates have persistent subfreezing temperatures year-round. Although less snowfall occurs here than in tundra or subarctic climates, snow pack and ice are permanent features of the landscape. The ice cap climates occur over the Arctic Ocean, interior portions of Greenland, and 97 percent of Antarctica. High atmospheric pressure dominates over these locations; however, the climate is made severe by year-round wind storms and surface blizzards. The Antarctic boasts the earth's coldest recorded temperature of minus 89 degrees C (minus 129 degrees F).

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