Some parts of the Arctic are covered by ice ("sea ice, "glacial ice, or "snow) year-round, and nearly all parts of the Arctic experience long periods with some form of ice on the surface. Average January temperatures range from about −40 to 0 °C (−40 to 32 °F), and winter temperatures can drop below −50 °C (−58 °F) over large parts of the Arctic. Average July temperatures range from about −10 to 10 °C (14 to 50 °F), with some land areas occasionally exceeding 30 °C (86 °F) in summer.
The Arctic consists of ocean that is nearly surrounded by land. As such, the "climate of much of the "Arctic is moderated by the ocean water, which can never have a temperature below −2 °C (28 °F). 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 "maritime climates.
The "climate of "Antarctica is the coldest on the whole of Earth. Antarctica has the lowest "temperature ever recorded: −89.2 °C (−128.6 °F) at "Vostok Station. It is also extremely dry (technically a "desert), averaging 166 millimetres (6.5 in) of "precipitation per year. Even so, on most parts of the continent the snow rarely melts and is eventually compressed to become the "glacial ice that makes up the "ice sheet. "Weather fronts rarely penetrate far into the continent.
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 10 °C (50 °F) summer isotherm; i.e., places where the average temperature in the warmest calendar month of the year is below 10 °C (50 °F) cannot support forests. See "Köppen climate classification for more information.
"Otto Nordenskjöld 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 (−4 °F) in its coldest month, the warmest month would need to average 11 °C (52 °F) or higher for trees to be able to survive there as 9 - 0.1(-20) = 11). 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 (32 °F) (and above 30 °C (86 °F)) are treated as 0 °C (32 °F) (because it makes no difference to plant life, being dormant). If the mean biotemperature is between 1.5 and 3 °C (34.7 and 37.4 °F), Holdridge quantifies the climate as "subpolar (or alpine, if the low temperature is caused by altitude).
- Yung, Chung-hoi. "Why is the equator very hot and the poles very cold?". Hong Kong Observatory. Retrieved 2010-12-02.
- McKnight, Tom L; Hess, Darrel (2000). "Climate Zones and Types: The Köppen System". Physical Geography: A Landscape Appreciation. Upper Saddle River, NJ: Prentice Hall. pp. 235–7. "ISBN "0-13-020263-0.
- This article incorporates "public domain material from the "CIA World Factbook website https://web.archive.org/web/20070613024704/https://www.cia.gov/library/publications/the-world-factbook/reference_maps/pdf/arctic.pdf.
- Gavin Hudson (2008-12-14). "The Coldest Inhabited Places on Earth". Eco Worldly. Archived from the original on 2008-12-18. Retrieved 2009-02-08.
- Biodiversity lectures and practicals of Allan Jones
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