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The ARCTIC OCEAN is the smallest and shallowest of the world's five major oceans . The International Hydrographic Organization
International Hydrographic Organization
(IHO) recognizes it as an ocean, although some oceanographers call it the ARCTIC MEDITERRANEAN SEA or simply the ARCTIC SEA, classifying it a mediterranean sea or an estuary of the Atlantic Ocean
Atlantic Ocean
. Alternatively, the Arctic
Arctic
Ocean
Ocean
can be seen as the northernmost part of the all-encompassing World Ocean
World Ocean
.

Located mostly in the Arctic
Arctic
north polar region in the middle of the Northern Hemisphere, the Arctic
Arctic
Ocean
Ocean
is almost completely surrounded by Eurasia
Eurasia
and North America
North America
. It is partly covered by sea ice throughout the year and almost completely in winter . The Arctic Ocean's surface temperature and salinity vary seasonally as the ice cover melts and freezes; its salinity is the lowest on average of the five major oceans, due to low evaporation , heavy fresh water 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%. The US National Snow and Ice Data Center (NSIDC) uses satellite data to provide a daily record of Arctic
Arctic
sea ice cover and the rate of melting compared to an average period and specific past years.

CONTENTS

* 1 History

* 2 Geography

* 2.1 Extent and major ports

* 2.1.1 United States
United States
* 2.1.2 Canada
Canada
* 2.1.3 Greenland
Greenland
* 2.1.4 Norway
Norway
* 2.1.5 Russia

* 2.2 Arctic
Arctic
shelves * 2.3 Underwater features

* 3 Oceanography
Oceanography

* 3.1 Water flow * 3.2 Sea ice
Sea ice

* 4 Climate
Climate
* 5 Animal and plant life * 6 Natural resources

* 7 Environmental concerns

* 7.1 Arctic
Arctic
ice melting * 7.2 Clathrate
Clathrate
breakdown * 7.3 Other concerns

* 8 See also * 9 References * 10 Further reading * 11 External links

HISTORY

For much of European history , the north polar regions remained largely unexplored and their geography conjectural. Pytheasof Massilia recorded an account of a journey northward in 325 BC, to a land he called "Eschate Thule
Thule
", where the Sun only set for three hours each day and the water was replaced by a congealed substance "on which one can neither walk nor sail". He was probably describing loose sea ice known today as "growlers " or "bergy bits"; his "Thule" was probably Norway
Norway
, though the Faroe Islands
Faroe Islands
or Shetland
Shetland
have also been suggested. Emanuel Bowen
Emanuel Bowen
's 1780s map of the Arctic
Arctic
features a "Northern Ocean".

Early cartographers were unsure whether to draw the region around the North Pole
North Pole
as land (as in Johannes Ruysch
Johannes Ruysch
's map of 1507 , or Gerardus Mercator 's map of 1595 ) or water (as with Martin Waldseemüller's world map of 1507 ). The fervent desire of European merchants for a northern passage, the Northern Sea Routeor the Northwest Passage
Northwest Passage
, to " Cathay
Cathay
" ( China
China
) caused water to win out, and by 1723 mapmakers such as Johann Homannfeatured an extensive "Oceanus Septentrionalis" at the northern edge of their charts.

The few expeditions to penetrate much beyond the Arctic
Arctic
Circle in this era added only small islands, such as Novaya Zemlya
Novaya Zemlya
(11th century) and Spitzbergen
Spitzbergen
(1596), though since these were often surrounded by pack-ice , their northern limits were not so clear. The makers of navigational charts , more conservative than some of the more fanciful cartographers, tended to leave the region blank, with only fragments of known coastline sketched in.

This lack of knowledge of what lay north of the shifting barrier of ice gave rise to a number of conjectures. In England and other European nations, the myth of an " Open Polar Sea" was persistent. John Barrow , longtime Second Secretary of the British Admiralty
Admiralty
, promoted exploration of the region from 1818 to 1845 in search of this.

In the United States
United States
in the 1850s and 1860s, the explorers Elisha Kane and Isaac Israel Hayesboth claimed to have seen part of this elusive body of water. Even quite late in the century, the eminent authority Matthew Fontaine Maury
Matthew Fontaine Maury
included a description of the Open Polar Sea in his textbook _The Physical Geography of the Sea_ (1883). Nevertheless, as all the explorers who travelled closer and closer to the pole reported, the polar ice cap is quite thick, and persists year-round.

Fridtjof Nansen
Fridtjof Nansen
was the first to make a nautical crossing of the Arctic
Arctic
Ocean, in 1896. The first surface crossing of the ocean was led by Wally Herbertin 1969, in a dog sled expedition from Alaska
Alaska
to Svalbard
Svalbard
, with air support. The first nautical transit of the north pole was made in 1958 by the submarine USS Nautilus , and the first surface nautical transit occurred in 1977 by the icebreaker NS Arktika .

Since 1937, Soviet and Russian manned drifting ice stations have extensively monitored the Arctic
Arctic
Ocean. Scientific settlements were established on the drift ice and carried thousands of kilometres by ice floes.

In World War II
World War II
, the European region of the Arctic
Arctic
Ocean
Ocean
was heavily contested : the Allied commitment to resupply the Soviet Union via its northern ports was opposed by German naval and air forces.

GEOGRAPHY

A bathymetric /topographic map of the Arctic
Arctic
Ocean
Ocean
and the surrounding lands. The Arctic
Arctic
region ; of note, the region's southerly border on this map is depicted by a red isotherm , with all territory to the north having an average temperature of less than 10 °C (50 °F) in July.

The Arctic
Arctic
Ocean
Ocean
occupies a roughly circular basin and covers an area of about 14,056,000 km2 (5,427,000 sq mi), almost the size of Antarctica
Antarctica
. The coastline is 45,390 km (28,200 mi) long. It is surrounded by the land masses of Eurasia, North America, Greenland
Greenland
, and by several islands .

It is generally taken to include Baffin Bay, Barents Sea
Barents Sea
, Beaufort Sea , Chukchi Sea
Chukchi Sea
, East Siberian Sea
East Siberian Sea
, Greenland
Greenland
Sea , Hudson Bay
Hudson Bay
, Hudson Strait, Kara Sea
Kara Sea
, Laptev Sea
Laptev Sea
, White Sea
White Sea
and other tributary bodies of water. It is connected to the Pacific Ocean
Pacific Ocean
by the Bering Strait and to the Atlantic Ocean
Atlantic Ocean
through the Greenland
Greenland
Sea and Labrador Sea
Labrador Sea
.

Countries bordering the Arctic
Arctic
Ocean
Ocean
are: Russia, Norway, Iceland, Greenland, Canada
Canada
and the United States.

EXTENT AND MAJOR PORTS

Main article: Borders of the oceans § Arctic
Arctic
Ocean
Ocean

There are several ports and harbours around the Arctic
Arctic
Ocean
Ocean

United States

In Alaska, the main ports are Barrow (71°17′44″N 156°45′59″W / 71.29556°N 156.76639°W / 71.29556; -156.76639 (Barrow) ) and Prudhoe Bay (70°19′32″N 148°42′41″W / 70.32556°N 148.71139°W / 70.32556; -148.71139 (Prudhoe) ).

Canada

In Canada
Canada
, ships may anchor at Churchill ( Port of Churchill) (58°46′28″N 094°11′37″W / 58.77444°N 94.19361°W / 58.77444; -94.19361 (Port of Churchill) ) in Manitoba
Manitoba
, Nanisivik ( NanisivikNaval Facility ) (73°04′08″N 084°32′57″W / 73.06889°N 84.54917°W / 73.06889; -84.54917 (Nanisivik Naval Facility) ) in Nunavut
Nunavut
, Tuktoyaktuk
Tuktoyaktuk
(69°26′34″N 133°01′52″W / 69.44278°N 133.03111°W / 69.44278; -133.03111 (Tuktoyaktuk) ) or Inuvik
Inuvik
(68°21′42″N 133°43′50″W / 68.36167°N 133.73056°W / 68.36167; -133.73056 (Inuvik) ) in the Northwest territories
Northwest territories
.

Greenland

In Greenland, the main port is at Nuuk
Nuuk
( Nuuk
Nuuk
Port and Harbour ) (64°10′15″N 051°43′15″W / 64.17083°N 51.72083°W / 64.17083; -51.72083 ( Nuuk
Nuuk
Port and Harbour) ).

Norway

In Norway
Norway
, Kirkenes
Kirkenes
(69°43′37″N 030°02′44″E / 69.72694°N 30.04556°E / 69.72694; 30.04556 (Kirkenes) ) and Vardø(70°22′14″N 031°06′27″E / 70.37056°N 31.10750°E / 70.37056; 31.10750 (Vardø) ) are ports on the mainland. Also, there is Longyearbyen
Longyearbyen
(78°13′12″N 15°39′00″E / 78.22000°N 15.65000°E / 78.22000; 15.65000 (Longyearbyen) ) on Svalbard
Svalbard
, a Norwegian archipelago, next to Fram Strait
Fram Strait
.

Russia

In Russia, major ports sorted by the different sea areas are:

* Murmansk
Murmansk
(68°58′N 033°05′E / 68.967°N 33.083°E / 68.967; 33.083 (Murmansk) ) in the Barents Sea * Arkhangelsk
Arkhangelsk
(64°32′N 040°32′E / 64.533°N 40.533°E / 64.533; 40.533 (Arkhangelsk) ) in the White Sea * Labytnangi
Labytnangi
(66°39′26″N 066°25′06″E / 66.65722°N 66.41833°E / 66.65722; 66.41833 (Labytnangi) ) Salekhard (66°32′N 066°36′E / 66.533°N 66.600°E / 66.533; 66.600 (Salekhard) ), Dudinka
Dudinka
(69°24′N 086°11′E / 69.400°N 86.183°E / 69.400; 86.183 (Dudinka) ), Igarka (67°28′N 86°35′E / 67.467°N 86.583°E / 67.467; 86.583 (Igarka) ) and Dikson (73°30′N 080°31′E / 73.500°N 80.517°E / 73.500; 80.517 (Dikson) ) in the Kara Sea * Tiksi
Tiksi
(71°38′N 128°52′E / 71.633°N 128.867°E / 71.633; 128.867 (Tiksi) ) in the Laptev Sea * Pevek(69°42′N 170°17′E / 69.700°N 170.283°E / 69.700; 170.283 (Pevek) ) in the East Siberian Sea

ARCTIC SHELVES

The ocean's Arctic
Arctic
shelf comprises a number of continental shelves , including the Canadian Arctic
Arctic
shelf, underlying the Canadian Arctic Archipelago , and the Russian continental shelf , which is sometimes simply called the " Arctic
Arctic
Shelf" because it is greater in extent. The Russian continental shelf consists of three separate, smaller shelves, the Barents Shelf , Chukchi Sea
Chukchi Sea
Shelf and Siberian Shelf. Of these three, the Siberian Shelfis the largest such shelf in the world. The Siberian Shelfholds large oil and gas reserves, and the Chukchi shelf forms the border between Russian and the United States
United States
as stated in the USSR–USA Maritime Boundary Agreement. The whole area is subject to international territorial claims .

UNDERWATER FEATURES

An underwater ridge , the Lomonosov Ridge, divides the deep sea North Polar Basin into two oceanic basins : the Eurasian Basin
Eurasian Basin
, which is between 4,000 and 4,500 m (13,100 and 14,800 ft) deep, and the Amerasian Basin(sometimes called the North American, or Hyperborean Basin), which is about 4,000 m (13,000 ft) deep. The bathymetry of the ocean bottom is marked by fault block ridges, abyssal plains , ocean deeps , and basins. The average depth of the Arctic
Arctic
Ocean
Ocean
is 1,038 m (3,406 ft). The deepest point is Litke Deep
Litke Deep
in the Eurasian
Eurasian
Basin, at 5,450 m (17,880 ft).

The two major basins are further subdivided by ridges into the Canada Basin (between Alaska/ Canada
Canada
and the Alpha Ridge), Makarov Basin (between the Alpha and Lomonosov Ridges), Amundsen Basin(between Lomonosov and Gakkel ridges), and Nansen Basin(between the Gakkel Ridge and the continental shelf that includes the Franz Josef Land
Franz Josef Land
).

OCEANOGRAPHY

WATER FLOW

Distribution of the major water mass in the Arctic
Arctic
Ocean. The section sketches the different water masses along a vertical section from Bering Straitover the geographic North Pole
North Pole
to Fram Strait
Fram Strait
. As the stratification is stable, deeper water masses are more dense than the layers above. Density
Density
structure of the upper 1,200 m (3,900 ft) in the Arctic
Arctic
Ocean. Profiles of temperature and salinity for the Amundsen Basin, the Canadian Basinand the Greenland
Greenland
Sea are sketched in this cartoon.

In large parts of the Arctic
Arctic
Ocean, the top layer (about 50 m (160 ft)) is of lower salinity and lower temperature than the rest. It remains relatively stable, because the salinity effect on density is bigger than the temperature effect. It is fed by the freshwater input of the big Siberian and Canadian streams (Ob , Yenisei , Lena , Mackenzie ), the water of which quasi floats on the saltier, denser, deeper ocean water. Between this lower salinity layer and the bulk of the ocean lies the so-called halocline , in which both salinity and temperature are rising with increasing depth. A Copepod
Copepod

Because of its relative isolation from other oceans, the Arctic
Arctic
Ocean has a uniquely complex system of water flow. It is classified as a mediterranean sea, which as “a part of the world ocean which has only limited communication with the major ocean basins (these being the Pacific, Atlantic, and Indian Oceans) and where the circulation is dominated by thermohaline forcing”. The Arctic
Arctic
Ocean
Ocean
has a total volume of 18.07×106 km3, equal to about 1.3% of the World Ocean. Mean surface circulation is predominately cyclonic on the Eurasian
Eurasian
side and anticyclonic in the Canadian Basin.

Water enters from both the Pacific and Atlantic Oceans and can be divided into three unique water masses. The deepest water mass is called Arctic
Arctic
Bottom Water and begins around 900 metres (3,000 feet) depth. It is composed of the densest water in the World Ocean
World Ocean
and has two main sources: Arctic
Arctic
shelf water and Greenland
Greenland
Sea Deep Water. Water in the shelf region that begins as inflow from the Pacific passes through the narrow Bering Straitat an average rate of 0.8 Sverdrups and reaches the Chukchi Sea
Chukchi Sea
. During the winter, cold Alaskan winds blow over the Chukchi Sea, freezing the surface water and pushing this newly formed ice out to the Pacific. The speed of the ice drift is roughly 1–4 cm/s. This process leaves dense, salty waters in the sea that sink over the continental shelf into the western Arctic
Arctic
Ocean
Ocean
and create a halocline . The Kennedy Channel .

This water is met by Greenland
Greenland
Sea Deep Water, which forms during the passage of winter storms. As temperatures cool dramatically in the winter, ice forms and intense vertical convection allows the water to become dense enough to sink below the warm saline water below. Arctic Bottom Water is critically important because of its outflow, which contributes to the formation of Atlantic Deep Water. The overturning of this water plays a key role in global circulation and the moderation of climate.

In the depth range of 150–900 metres (490–2,950 feet) is a water mass referred to as Atlantic Water. Inflow from the North Atlantic Current enters through the Fram Strait
Fram Strait
, cooling and sinking to form the deepest layer of the halocline, where it circles the Arctic
Arctic
Basin counter-clockwise. This is the highest volumetric inflow to the Arctic Ocean, equalling about 10 times that of the Pacific inflow, and it creates the Arctic
Arctic
Ocean
Ocean
Boundary Current. It flows slowly, at about 0.02 m/s. Atlantic Water has the same salinity as Arctic
Arctic
Bottom Water but is much warmer (up to 3 °C). In fact, this water mass is actually warmer than the surface water, and remains submerged only due to the role of salinity in density. When water reaches the basin it is pushed by strong winds into a large circular current called the Beaufort Gyre. Water in the Beaufort Gyreis far less saline than that of the Chukchi Sea
Chukchi Sea
due to inflow from large Canadian and Siberian rivers.

The final defined water mass in the Arctic
Arctic
Ocean
Ocean
is called Arctic Surface Water and is found from 150–200 metres (490–660 feet). The most important feature of this water mass is a section referred to as the sub-surface layer. It is a product of Atlantic water that enters through canyons and is subjected to intense mixing on the Siberian Shelf . As it is entrained, it cools and acts a heat shield for the surface layer. This insulation keeps the warm Atlantic Water from melting the surface ice. Additionally, this water forms the swiftest currents of the Arctic, with speed of around 0.3-0.6 m/s. Complementing the water from the canyons, some Pacific water that does not sink to the shelf region after passing through the Bering Strait also contributes to this water mass.

Waters originating in the Pacific and Atlantic both exit through the Fram Strait
Fram Strait
between Greenland
Greenland
and Svalbard
Svalbard
Island , which is about 2,700 metres (8,900 feet) deep and 350 kilometres (220 miles) wide. This outflow is about 9 Sv. The width of the Fram Strait
Fram Strait
is what allows for both inflow and outflow on the Atlantic side of the Arctic Ocean. Because of this, it is influenced by the Coriolis force
Coriolis force
, which concentrates outflow to the East Greenland
Greenland
Current on the western side and inflow to the Norwegian Currenton the eastern side. Pacific water also exits along the west coast of Greenland
Greenland
and the Hudson Strait (1-2 Sv), providing nutrients to the Canadian Archipelago.

As noted, the process of ice formation and movement is a key driver in Arctic
Arctic
Ocean
Ocean
circulation and the formation of water masses. With this dependence, the Arctic
Arctic
Ocean
Ocean
experiences variations due to seasonal changes in sea ice cover. Sea ice
Sea ice
movement is the result of wind forcing, which is related to a number of meteorological conditions that the Arctic
Arctic
experiences throughout the year. For example, the Beaufort High—an extension of the Siberian High system—is a pressure system that drives the anticyclonic motion of the Beaufort Gyre. During the summer, this area of high pressure is pushed out closer to its Siberian and Canadian sides. In addition, there is a sea level pressure (SLP) ridge over Greenland
Greenland
that drives strong northerly winds through the Fram
Fram
Strait, facilitating ice export. In the summer, the SLP contrast is smaller, producing weaker winds. A final example of seasonal pressure system movement is the low pressure system that exists over the Nordic and Barents Seas. It is an extension of the Icelandic Low
Icelandic Low
, which creates cyclonic ocean circulation in this area. The low shifts to centre over the North Pole in the summer. These variations in the Arctic
Arctic
all contribute to ice drift reaching its weakest point during the summer months. There is also evidence that the drift is associated with the phase of the Arctic
Arctic
Oscillation and Atlantic Multidecadal Oscillation
Atlantic Multidecadal Oscillation
.

SEA ICE

Sea cover in the Arctic
Arctic
Ocean, showing the median, 2005 and 2007 coverage Main article: Arctic
Arctic
ice pack

Much of the Arctic
Arctic
Ocean
Ocean
is covered by sea ice that varies in extent and thickness seasonally. The mean extent of the ice has been decreasing since 1980 from the average winter value of 15,600,000 km2 (6,023,200 sq mi) at a rate of 3% per decade. The seasonal variations are about 7,000,000 km2 (2,702,700 sq mi) with the maximum in April and minimum in September. The sea ice is affected by wind and ocean currents, which can move and rotate very large areas of ice. Zones of compression also arise, where the ice piles up to form pack ice.

Icebergs occasionally break away from northern Ellesmere Island
Ellesmere Island
, and icebergs are formed from glaciers in western Greenland
Greenland
and extreme northeastern Canada. These icebergs pose a hazard to ships, of which the _Titanic_ is one of the most famous. Permafrost
Permafrost
is found on most islands. The ocean is virtually icelocked from October to June, and the superstructure of ships are subject to icing from October to May. Before the advent of modern icebreakers , ships sailing the Arctic Ocean
Ocean
risked being trapped or crushed by sea ice (although the _Baychimo _ drifted through the Arctic
Arctic
Ocean
Ocean
untended for decades despite these hazards).

CLIMATE

See also: Climate
Climate
change in the Arctic
Arctic
Play media Changes in ice between 1990–1999

Under the influence of the Quaternary glaciation
Quaternary glaciation
, the Arctic
Arctic
Ocean is contained in a polar climate characterized by persistent cold and relatively narrow annual temperature ranges. Winters are characterized by the polar night , extreme cold, frequent low-level temperature inversions, and stable weather conditions. Cyclones are only common on the Atlantic side. Summers are characterized by continuous daylight (midnight sun ), and temperatures can rise above the melting point (0 °C (32 °F). Cyclones are more frequent in summer and may bring rain or snow. It is cloudy year-round, with mean cloud cover ranging from 60% in winter to over 80% in summer.

The temperature of the surface of the Arctic
Arctic
Ocean
Ocean
is fairly constant, near the freezing point of seawater . Because the Arctic Ocean
Ocean
consists of saltwater, the temperature must reach −1.8 °C (28.8 °F) before freezing occurs.

The density of sea water, in contrast to fresh water, increases as it nears the freezing point and thus it tends to sink. It is generally necessary that the upper 100–150 m (330–490 ft) of ocean water cools to the freezing point for sea ice to form. In the winter the relatively warm ocean water exerts a moderating influence, even when covered by ice. This is one reason why the Arctic
Arctic
does not experience the extreme temperatures seen on the Antarctic
Antarctic
continent .

There is considerable seasonal variation in how much pack ice of the Arctic
Arctic
ice pack covers the Arctic
Arctic
Ocean. Much of the Arctic
Arctic
ice pack is also covered in snow for about 10 months of the year. The maximum snow cover is in March or April — about 20 to 50 cm (7.9 to 19.7 in) over the frozen ocean.

The climate of the Arctic
Arctic
region has varied significantly in the past. As recently as 55 million years ago, during the Paleocene–Eocene Thermal Maximum, the region reached an average annual temperature of 10–20 °C (50–68 °F). The surface waters of the northernmost Arctic
Arctic
Ocean
Ocean
warmed, seasonally at least, enough to support tropical lifeforms requiring surface temperatures of over 22 °C (72 °F).

ANIMAL AND PLANT LIFE

_ Three polar bears approach USS Honolulu_ near the North Pole
North Pole
.

Endangered marine species in the Arctic
Arctic
Ocean
Ocean
include walruses and whales . The area has a fragile ecosystem which is slow to change and slow to recover from disruptions or damage. Lion\'s mane jellyfish are abundant in the waters of the Arctic, and the banded gunnel is the only species of gunnel that lives in the ocean.

The Arctic
Arctic
Ocean
Ocean
has relatively little plant life except for phytoplankton . Phytoplankton
Phytoplankton
are a crucial part of the ocean and there are massive amounts of them in the Arctic, where they feed on nutrients from rivers and the currents of the Atlantic and Pacific oceans. During summer, the sun is out day and night, thus enabling the phytoplankton to photosynthesize for long periods of time and reproduce quickly. However, the reverse is true in winter when they struggle to get enough light to survive.

NATURAL RESOURCES

See also: Natural resources of the Arctic
Arctic
, Territorial claims in the Arctic
Arctic
, and Marine mammal
Marine mammal

Petroleum
Petroleum
and natural gas fields , placer deposits , polymetallic nodules , sand and gravel aggregates , fish, seals and whales can all be found in abundance in the region.

The political dead zone near the centre of the sea is also the focus of a mounting dispute between the United States, Russia, Canada, Norway, and Denmark. It is significant for the global energy market because it may hold 25% or more of the world's undiscovered oil and gas resources.

ENVIRONMENTAL CONCERNS

Main articles: Climate
Climate
change in the Arctic
Arctic
, Ozone depletion
Ozone depletion
, and Pollution in the Arctic
Arctic
Ocean
Ocean

ARCTIC ICE MELTING

The Arctic
Arctic
ice pack is thinning, and in many years there is also a seasonal hole in the ozone layer . Reduction of the area of Arctic sea ice reduces the planet's average albedo , possibly resulting in global warming in a positive feedback mechanism. Research shows that the Arctic
Arctic
may become ice free for the first time in human history within a few years or by 2040. Estimates vary for when the last time the Arctic
Arctic
was ice free: 65 million years ago when fossils indicate that plants existed there to as few as 5,500 years ago; ice and ocean cores going back 8000 years to the last warm period or 125,000 during the last intraglacial period .

Warming temperatures in the Arctic
Arctic
may cause large amounts of fresh meltwater to enter the north Atlantic, possibly disrupting global ocean current patterns . Potentially severe changes in the Earth's climate might then ensue.

As the extent of sea ice diminishes and sea level rises, the effect of storms such as the Great Arctic
Arctic
Cyclone
Cyclone
of 2012 on open water increases, as does possible salt-water damage to vegetation on shore at locations such as the Mackenzie's river delta as stronger storm surges become more likely.

CLATHRATE BREAKDOWN

Main article: Clathrate gun hypothesis Marine extinction intensity during the Phanerozoic % Millions of years ago (H) K–Pg Tr–J P–Tr Cap Late D O–S The Permian– Triassic
Triassic
extinction event (the Great Dying) may have been caused by release of methane from clathrates . An estimated 52% of marine genus became extinct, representing 96% of all marine species .

Sea ice
Sea ice
, and the cold conditions it sustains, serves to stabilise methane deposits on and near the shoreline, preventing the clathrate breaking down and outgassing methane into the atmosphere, causing further warming. Melting of this ice may release large quantities of methane , a powerful greenhouse gas into the atmosphere , causing further warming in a strong positive feedback cycle and; marine genus and species to become extinct.

OTHER CONCERNS

Other environmental concerns relate to the radioactive contamination of the Arctic
Arctic
Ocean
Ocean
from, for example, Russian radioactive waste dump sites in the Kara Sea
Kara Sea
and Cold War
Cold War
nuclear test sites such as Novaya Zemlya. In addition, Shell planned to drill exploratory wells in the Chukchi and Beaufort seas during the summer of 2012, which environmental groups filed a lawsuit about in an attempt to protect native communities, endangered wildlife, and the Arctic
Arctic
Ocean
Ocean
in the event of a major oil spill.

On July 16, 2015, five nations ( United States
United States
of America, Russia, Canada, Norway, Denmark/Greenland) signed a declaration committing to keep their fishing vessels out of a 1.1 million square mile zone in the central Arctic
Arctic
Ocean
Ocean
near the North Pole. The agreement calls for those nations to refrain from fishing there until there is better scientific knowledge about the marine resources and until a regulatory system is in place to protect those resources.

SEE ALSO

* Arctic
Arctic
portal * Geography portal

* Arctic
Arctic
Bridge * Arctic
Arctic
cooperation and politics * Arctic
Arctic
sea ice ecology and history * Chukchi Cap * Explorers of the Arctic
Arctic
* Extreme points of the Arctic
Arctic
* Fauna of the Arctic
Arctic
* International Arctic
Arctic
Science Committee * Nordicity * North Atlantic Current
North Atlantic Current
* Seven Seas
Seven Seas
* Subarctic
Subarctic

REFERENCES

* ^ _A_ _B_ _C_ Michael Pidwirny (2006). "Introduction to the Oceans". _www.physicalgeography.net_. Archived from the original on 9 December 2006. Retrieved 2006-12-07. * ^ Tomczak, Matthias; Godfrey, J. Stuart (2003). _Regional Oceanography: an Introduction_ (2nd ed.). Delhi: Daya Publishing House. ISBN 81-7035-306-8 . * ^ "\' Arctic
Arctic
Ocean\' - Encyclopædia Britannica". Retrieved 2012-07-02. As an approximation, the Arctic
Arctic
Ocean
Ocean
may be regarded as an estuary of the Atlantic Ocean. * ^ Some Thoughts on the Freezing and Melting of Sea Ice and Their Effects on the Ocean
Ocean
K. Aagaard and R. A. Woodgate, Polar Science Center, Applied Physics Laboratory University of Washington, January 2001. Retrieved 7 December 2006. * ^ PytheasArchived September 18, 2008, at the Wayback Machine. Andre Engels. Retrieved 16 December 2006. * ^ Channel 4, "Sir Wally Herbertdies" 13 June 2007 * ^ North Pole
North Pole
drifting stations (1930s–1980s) * ^ _A_ _B_ Wright, John W., ed. (2006). _The New York Times Almanac_ (2007 ed.). New York, New York: Penguin Books. p. 455. ISBN 0-14-303820-6 . * ^ "Oceans of the World" (PDF). rst2.edu. Archived from the original (PDF) on 2011-07-19. Retrieved 2010-10-28. * ^ " Arctic
Arctic
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FURTHER READING

* Neatby, Leslie H., _Discovery in Russian and Siberian Waters_ 1973 ISBN 0-8214-0124-6 * Ray, L., and bacon, B., eds., _The Arctic
Arctic
Ocean_ 1982 ISBN 0-333-31017-9 * Thorén, Ragnar V. A., _Picture Atlas of the Arctic_ 1969 ISBN 0-8214-0124-6

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