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The polar climate regions are characterized by a lack of warm but with varying . Every month a polar climate has an average temperature of less than . Regions with a polar climate cover more than 20% of the Earth's area. Most of these regions are far from the equator and near the poles, and in this case, winter days are extremely short and summer days are extremely long (they could last for the entirety of each season or longer). A polar climate consists of cool summers and very cold winters (or, in the case of ice cap climates, no real summer at all), which results in treeless , , or a permanent or semi-permanent layer of ice. It is identified with the letter E in the Köppen climate classification.
Subtypes
There are two types of polar climate:
ET, or
tundra climate; and
EF, or ice cap climate. A tundra climate is characterized by having at least one month whose average temperature is above , while an ice cap climate has no months averaging above .
In a tundra climate, even
coniferous trees cannot grow, but other specialized plants such as the arctic poppy can grow. In an ice cap climate, no plants can grow, and ice gradually accumulates until it flows or slides elsewhere. Many
high altitude locations on Earth have a climate where no month has an average temperature of or higher, but as this is due to elevation, this climate is referred to as
Alpine climate. Alpine climate can mimic either tundra or ice cap climate.
Locations
On Earth, the only continent where the ice cap polar climate is predominant is
Antarctica. All but a few isolated coastal areas on the island of
Greenland also have the ice cap climate. Summits of many high mountains also have ice cap climate due to their high elevation. Coastal regions of Greenland that do not have permanent ice sheets have the less extreme tundra climates. The northernmost part of the
land mass, from the extreme northeastern coast of
Scandinavia and eastwards to the
Bering Strait, large areas of northern
Siberia and northern
Iceland have tundra climate as well. Large areas in northern
Canada and northern
Alaska have tundra climate, changing to ice cap climate in the most northern parts of Canada. Southernmost
Argentina (Tierra del Fuego where it abuts the
Drake Passage) and such subantarctic islands such as the South Shetland Islands and the
Falkland Islands have
tundra climates of slight
temperature range in which no month is as warm as . These subantarctic lowlands are found closer to the
equator than the coastal tundras of the Arctic basin. Summits of many mountains of
Earth also have polar climates, due to their higher elevations.
Arctic
Some parts of the Arctic are covered by ice (
sea ice,
glacier, or
snow) year-round, especially at the most poleward parts; and nearly all parts of the Arctic experience long periods with some form of ice or snow on the surface. Average January temperatures range from about , and winter temperatures can drop below over large parts of the Arctic. Average July temperatures range from about , with some land areas occasionally exceeding in summer.
The Arctic consists of an Arctic Ocean that is almost surrounded by landmasses like Russia and Canada. As such, the climate of much of the Arctic is moderated by the ocean water, which can never have a temperature below . In winter, this relatively warm water, even though covered by the polar ice pack, keeps the North Pole from being the coldest place in the Northern Hemisphere, and it is also part of the reason that Antarctica is so much colder than the Arctic. In summer, the presence of the nearby water keeps coastal areas from warming as much as they might otherwise, just as it does in temperate regions with .
Antarctica
The
climate of
Antarctica is the coldest on
Earth. Antarctica has the lowest naturally occurring
temperature ever recorded: at Vostok Station in 1983.
It is also extremely dry (technically a
desert, or so called
polar desert), averaging of precipitation per year, as
rarely penetrate far into the continent.
Mountains
Summits of most mountains also have polar climates, despite being in lower latitudes, due to their high elevations. The highest mountains of the
Rocky Mountains,
Alps, and the
Caucasus have tundra climate. Some mountains of the
Andes, the Saint Elias Mountains, and most mountains of the
Himalayas, the
Karakoram, the Hindu Kush Range,
Pamir Mountains, the Tian Shan Mountains, and the
Alaska Range also have ice cap climates at extremely high elevations, in addition to tundra climates at relatively lower elevations. Only the summit of
Mount Rainier has an ice cap climate in the
Cascade Range.
Quantifying polar climate
There have been several attempts at quantifying what constitutes a polar climate.
Climatologist Wladimir Köppen demonstrated a relationship between the Arctic and Antarctic tree lines and the summer isotherm; i.e., places where the average temperature in the warmest calendar month of the year is below the fixed threshold of cannot support forests. See Köppen climate classification for more information.
Otto Nordenskjöld theorized that winter conditions also play a role: His formula is , where W is the average temperature in the warmest month and C the average of the coldest month, both in degrees Celsius. For example, if a particular location had an average temperature of in its coldest month, the warmest month would need to average or higher for trees to be able to survive there as . Nordenskiöld's line tends to run to the north of Köppen's near the west coasts of the Northern Hemisphere continents, south of it in the interior sections, and at about the same latitude along the east coasts of both Asia and North America. In the Southern Hemisphere, all of Tierra del Fuego lies outside the polar region in Nordenskiöld's system, but part of the island (including Ushuaia, Argentina) is reckoned as being within the Antarctic under Köppen's.
In 1947, Holdridge improved on these schemes, by defining biotemperature: the mean annual temperature, where all temperatures below (and above ) are treated as 0 °C (because it makes no difference to plant life, being dormant). If the mean biotemperature is between ,
See also
-
Arctic oscillation
-
Climate change in the Arctic
-
Global warming in Antarctica
External links
