Polar_climate

Solar radiation has a lower intensity in polar regions because it travels a longer distance through the atmosphere, and is spread across a larger surface area.

Regions with a polar climate are characterized by a lack of warm summers (specifically, no month having an average temperature of 10 °C or higher).

The tundra covers over 20% of the earth. The sun shines 24 hours in the summer, and barely ever shines at all in the winter (see midnight sun).

Quantifying the 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 10 °C summer isotherm; i.e., places where the average temperature in the warmest calendar month of the year is below 10 °C cannot support forests. See Köppen climate classification for more information.

Otto Nordenskiöld theorized that winter conditions also play a role: His formula is W = 9 − 0.1 C, where W is the average temperature in the warmest month and C the average of the coldest month, both in degrees Celsius (this would mean, for example, that if a particular location had an average temperature of −20 °C in its coldest month, the warmest month would need to average 11 °C or higher for trees to be able to survive there). 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 0 °C are treated as 0 °C (because it makes no difference to plant life, being dormant). If the mean biotemperature is between 1.5 °C and 3 °C,^[1] Holdridge quantifies the climate as subpolar (or alpine, if the low temperature is caused by altitude).

Effects

A polar bear with cub

Polar climates result in the absence of trees in such places, which may also be covered with glaciers or a permanent or semi-permanent layer of ice.

Examples

On Earth, the only continent where the extreme (EF -- ice cap) polar climate is predominant is Antarctica. All but a few isolated coastal areas on the island of Greenland also have the extreme EF polar climate. Coastal regions of Greenland that do not have permanent ice sheets have "only" the less extreme tundra (ET) climates. The northernmost part of the Eurasian 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 South America (Tierra del Fuego where it abuts the Drake Passage and such subantarctic islands such as the South Shetland Islands and the Falkland Islands have ET, or tundra climates of slight thermal range in which no month is as warm as 10°C. These subantarctic lowlands are to be found more equatorward than the coastal tundras of the Arctic basin.

In other parts of the world, many mountains have a climate where no month having an average temperature of 10 °C or higher, but as this is due to elevation, this climate is referred to as Alpine climate. Polar climates have also been observed on other planets, such as Mars, which has big and noticeable ice caps on both poles.

See also

• Arctic
• Arctic oscillation
• Antarctica
• Climate of the Arctic
• Climate of Antarctica
• High Alps
• Köppen climate classification

References

External links

• NOAA State of the Arctic Report 2006

Wikimedia Commons has media related to: Polar climate

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