Portal:Arctic

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Arctic Circle
Arctic Circle.


The Arctic- The biodiversity of the tundras is low. Notable animals in the Arctic tundra include caribou (reindeer), musk ox, arctic hare, arctic fox, snowy owl, lemmings, and polar bears (only the extreme north).

Due to the harsh climate of the Arctic tundra, regions of this kind have seen little human activity, even though they are sometimes rich in natural resources such as oil and uranium. In recent times this has begun to change in Alaska, Russia, and some other parts of the world.

A severe threat to the tundras, specifically to the permafrost, is global warming. The melting of the permafrost in a given area on human time scales (decades or centuries) could radically change which species can survive there.

Another concern is that about one third of the world's soil-bound carbon is in taiga and tundra areas. When the permafrost melts, it releases carbon in the form of carbon dioxide, a greenhouse gas. The effect has been observed in Alaska. In the 1970s the tundra was a carbon sink, but today, it is a carbon source.

Almost completely surrounded by Eurasia and North America, the Arctic Ocean is largely covered by sea ice throughout the year. The Arctic Ocean's temperature and salinity vary seasonally as the ice cover melts and freezes[3]; its salinity is the lowest on average of the five major oceans, due to low evaporation, heavy freshwater inflow from rivers and streams, and limited connection and outflow to surrounding oceanic waters with higher salinities. The summer shrinking of the ice has been quoted at 50%.[1] The National Snow and Ice Data Center NSIDC use satellite data to provide a daily record of Arctic sea ice cover and the rate of melting compared to an average period and specific past years.

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The walrus (Odobenus rosmarus) is a large flippered marine mammal with a discontinuous circumpolar distribution in the Arctic Ocean and sub-Arctic seas of the Northern Hemisphere. The walrus is the only living species in the Odobenidae family and Odobenus genus. It is subdivided into three subspecies:[1] the Atlantic Walrus (O. rosmarus rosmarus) found in the Atlantic Ocean, the Pacific Walrus (O. rosmarus divergens) found in the Pacific Ocean, and O. rosmarus laptevi, found in the Laptev Sea.

The walrus is immediately recognizable due to its prominent tusks, whiskers and great bulk. Adult Pacific males can weigh up to 4,500 lb (2,000 kg),[2] and, among pinnipeds, are exceeded in size only by the two species of elephant seals.[3] It resides primarily in shallow oceanic shelf habitat, spending a significant proportion of its life on sea ice in pursuit of its preferred diet of benthic bivalve mollusks. It is a relatively long-lived, social animal and is considered a keystone species in Arctic marine ecosystems.

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Uriel Sebree
Uriel Sebree (February 20, 1848 – August 6, 1922) was a career officer in the United States Navy. He entered the Naval Academy during the Civil War and served until 1910, retiring as a rear admiral. He is best remembered for his two expeditions into the Arctic and for serving as the second acting governor of American Samoa. He was also commander-in-chief of the Pacific Fleet.

After graduating from the U.S. Naval Academy in 1867, Sebree was posted to a number of vessels before being assigned to a rescue mission to find the remaining crew of the missing Polaris in the Navy's first mission to the Arctic. This attempt was only a partial success—the Polaris crew was rescued by a Scottish ship rather than the US Navy—but this led to Sebree's selection eleven years later for a second expedition to the Arctic. That mission to rescue Adolphus Greely and the survivors of the Lady Franklin Bay expedition was a success. Sebree was subsequently appointed as the second acting governor of American Samoa.

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Naajaat
Panoramic view of Naajaat in North-West Greenland. The ice cap is seen to the upper left..

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References

  1. ^ Wozencraft, W. C. (2005). "Order Carnivora". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. pp. 532–628. ISBN 978-0-8018-8221-0. OCLC 62265494. 
  2. ^ Walruses - Walrus Facts and Types - walruses.net
  3. ^ Fay, F.H. (1985). "Odobenus rosmarus". Mammalian Species 238: 1–7. doi:10.2307/3503810.