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{{Short description|Oceanic division}}
{{Redirect|Arctic Sea|the cargo ship|MV Arctic Sea}}
{{Use dmy dates|date=September 2021}}
{{Use Canadian English|date=September 2016}}
[[File:Arctic Ocean - en.png|thumb|upright=1.3|The Arctic Ocean, with borders as delineated by the [[International Hydrographic Organization]] (IHO), including [[Hudson Bay]] (some of which is south of [[57th parallel north|57°N latitude]], off the map) and all other marginal seas.]]
{{Five oceans}}
The '''Arctic Ocean''' is the smallest and shallowest of the world's five [[Borders of the oceans|oceanic divisions]].<ref name=Pidwirny>{{cite web | title=Introduction to the Oceans | work=physicalgeography.net | 
url=http://www.physicalgeography.net/fundamentals/8o.html | author=Pidwirny, Michael | date=2006 | access-date=7 December 2006 | archive-url=https://web.archive.org/web/20061209125035/http://www.physicalgeography.net/fundamentals/8o.html | archive-date=9 December 2006 | url-status=dead }}</ref> It spans an area of approximately {{convert|14060000|km2|abbr=on}} and is the coldest of the world's oceans. The [[International Hydrographic Organization]] (IHO) recognizes it as an ocean, although some [[oceanography|oceanographers]] call it the '''Arctic Mediterranean Sea'''.<ref>{{Cite book |title=General oceanography: an introduction |date=1980 |publisher=Wiley |isbn=0471021024 |edition=2nd |location=New York |pages=501 |oclc=6200221}}</ref> It has also been described as an [[estuary]] of the [[Atlantic Ocean]].<ref>{{Cite book
| first1=Matthias
| last1=Tomczak
| first2=J. Stuart
| last2=Godfrey
| title=Regional Oceanography: an Introduction
| edition=2nd
| date=2003
| publisher=Daya Publishing House
| place=Delhi
| isbn=978-81-7035-306-5
| url=http://www.es.flinders.edu.au/~mattom/regoc/
| access-date=22 April 2006
| archive-url=https://web.archive.org/web/20070630202249/http://www.es.flinders.edu.au/~mattom/regoc/
| archive-date=30 June 2007
| url-status=dead
}}</ref><ref>{{Cite web|url=https://www.britannica.com/EBchecked/topic/33188/Arctic-Ocean/57838/Oceanography|title='Arctic Ocean' – Encyclopædia Britannica|newspaper=Encyclopedia Britannica |access-date=2 July 2012|quote=As an approximation, the Arctic Ocean may be regarded as an estuary of the Atlantic Ocean.}}</ref> It is also seen as the northernmost part of the all-encompassing [[world ocean]].

The Arctic Ocean includes the [[North Pole]] region in the middle of the [[Northern Hemisphere]] and extends south to about [[60th parallel north|60°N]]. The Arctic Ocean is surrounded by [[Eurasia]] and North America, and the borders follow topographic features: the [[Bering Strait]] on the [[Pacific Ocean|Pacific]] side and the Greenland Scotland Ridge on the Atlantic side. It is mostly covered by [[sea ice]] throughout the year and almost completely in [[winter]]. The Arctic Ocean's [[Sea surface temperature|surface temperature]] and [[salinity]] vary seasonally as the [[Arctic ice pack|ice cover]] melts and freezes;<ref>[http://psc.apl.washington.edu/HLD/Lomo/OM2001AagaardWoodgate.pdf Some Thoughts on the Freezing and Melting of Sea Ice and Their Effects on the Ocean] {{Webarchive|url=https://web.archive.org/web/20171108092457/http://psc.apl.washington.edu/HLD/Lomo/OM2001AagaardWoodgate.pdf |date=8 November 2017 }} K. Aagaard and R. A. Woodgate, Polar Science Center, Applied Physics Laboratory University of Washington, January 2001. Retrieved 7 December 2006.</ref> 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%.<ref name=Pidwirny /> The US [[National Snow and Ice Data Center]] (NSIDC) uses 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, showing a continuous [[Arctic sea ice decline|decline in sea ice]] extent.<ref>{{Cite web|title=Arctic Sea Ice News and Analysis {{!}} Sea ice data updated daily with one-day lag|url=https://nsidc.org/arcticseaicenews/|access-date=2020-09-01|language=en-US}}</ref> In September 2012, the Arctic ice extent reached a new record minimum. Compared to the average extent (1979–2000), the sea ice had diminished by 49%.<ref>{{Cite web|title=Understanding the Arctic sea ice: Polar Portal|url=http://polarportal.dk/en/sea-ice-and-icebergs/understanding-the-arctic-sea-ice/|access-date=2020-09-01|website=polarportal.dk}}</ref>

== History ==

=== North America ===
Human habitation in the North American polar region goes back at least 17,000–50,000 years, during the [[Wisconsin glaciation]]. Falling [[sea level]]s allowed people to move across the [[Bering land bridge]] that joined [[Siberia]] to northwestern North America (Alaska), leading to the [[Settlement of the Americas]].<ref name=Goebel>{{cite journal |title=The Late Pleistocene Dispersal of Modern Humans in the Americas |url=http://www.centerfirstamericans.com/cfsa-publications/Science2008.pdf |year=2008 |doi=10.1126/science.1153569 |pmid=18339930 |volume=319 |issue=5869 |journal=Science |pages=1497–502 |vauthors=Goebel T, Waters MR, O'Rourke DH|bibcode=2008Sci...319.1497G |citeseerx=10.1.1.398.9315 |s2cid=36149744 }}</ref>

[[File:Cambridge Bay Thule Site 1998-06-28.jpg|left|thumb|Thule archaeological site]]

[[Early Paleo-Eskimo]] groups included the [[Pre-Dorset]] ({{circa|3200–850 BC}}); the [[Saqqaq culture]] of Greenland (2500–800&nbsp;BC); the [[Independence I culture|Independence I]] and [[Independence II culture]]s of northeastern Canada and [[Greenland]] ({{circa|2400–1800 BC}} and {{circa|800–1 BC}}); and the [[Groswater]] of [[Labrador]] and [[Nunavik]]. The [[Dorset culture]] spread across Arctic North America between 500&nbsp;BC and AD&nbsp;1500. The Dorset were the last major [[Paleo-Eskimo]] culture in the Arctic before the migration east from present-day [[Alaska]] of the [[Thule people]], ancestors of the modern [[Inuit]].<ref>[http://www.natmus.dk/sw18630.asp "The Prehistory of Greenland"] {{webarchive|url=https://web.archive.org/web/20080516102219/http://www.natmus.dk/sw18630.asp |date=16 May 2008 }}, Greenland Research Centre, National Museum of Denmark, accessed 14 April 2010.</ref>

The Thule Tradition lasted from about 200&nbsp;BC to AD&nbsp;1600, arising around the Bering Strait and later encompassing almost the entire Arctic region of North America. The Thule people were the ancestors of the Inuit, who now live in Alaska, [[Northwest Territories]], [[Nunavut]], Nunavik (northern Quebec), Labrador and Greenland.<ref name="waterloo">{{cite web |last=Park |first=Robert W. |title=Thule Tradition |website=Arctic Archaeology |publisher=Department of Anthropology, University of Waterloo |url=http://anthropology.uwaterloo.ca/ArcticArchStuff/thule.html |access-date=1 June 2015}}</ref>

=== Europe ===
For much of [[History of Europe|European history]], the north [[polar region]]s remained largely unexplored and their geography conjectural. [[Pytheas]] of [[Marseille|Massilia]] recorded an account of a journey northward in 325&nbsp;BC, to a land he called "[[Thule|Eschate 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 "[[Iceberg|growlers]]" or "bergy bits"; his "Thule" was probably [[Norway]], though the [[Faroe Islands]] or [[Shetland]] have also been suggested.<ref>[http://www.win.tue.nl/~engels/discovery/pytheas.html Pytheas] {{webarchive |url=https://web.archive.org/web/20080918073035/http://www.win.tue.nl/~engels/discovery/pytheas.html |date=18 September 2008 }} Andre Engels. Retrieved 16 December 2006.</ref>
[[File:Map of the Arctic, 1780s - B&W.jpeg|thumb|left|[[Emanuel Bowen]]'s 1780s map of the Arctic features a "Northern Ocean".]]
Early [[Cartography|cartographers]] were unsure whether to draw the region around the North Pole as land (as in [[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 Route]] or the [[Northwest Passage]], to "[[Cathay]]" ([[China]]) caused water to win out, and by 1723 mapmakers such as [[Johann Homann]] featured an extensive "Oceanus Septentrionalis" at the northern edge of their charts.

The few expeditions to penetrate much beyond the [[Arctic Circle]] in that era added only small islands, such as [[Novaya Zemlya]] (11th century) and [[Spitzbergen]] (1596), though, since these were often surrounded by [[Drift ice|pack-ice]], their northern limits were not so clear. The makers of [[Nautical chart|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.

[[File:Map of the Arctic region showing the Northeast Passage, the Northern Sea Route and Northwest Passage, and bathymetry.png|thumb|upright=1.25|The Arctic region showing the [[Northeast Passage]], the [[Northern Sea Route]] within it, and the [[Northwest Passage]] via Canadian Inland Waters.]]

=== 19th century ===
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 [[Mythology|myth]] of an "[[Open Polar Sea]]" was persistent. [[Sir John Barrow, 1st Baronet|John Barrow]], longtime Second Secretary of the [[British Admiralty]], [[Arctic exploration|promoted exploration]] of the region from 1818 to 1845 in search of this.

In the United States in the 1850s and 1860s, the explorers [[Elisha Kane]] and [[Isaac Israel Hayes]] both claimed to have seen part of this elusive body of water. Even quite late in the century, the eminent authority [[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]] was the first to make a [[Seamanship|nautical]] crossing of the Arctic Ocean, in the [[Nansen's Fram expedition|Fram Expedition]] from 1893 to 1896.

=== 20th century ===
The first surface crossing of the ocean was led by [[Wally Herbert]] in 1969, in a [[dog sled]] expedition from Alaska to [[Svalbard]], with air support.<ref>{{Cite web|url=http://www.channel4.com/news/articles/uk/sir+wally+herbert+dies/558357|title=Channel 4, "Sir Wally Herbert dies" 13 June 2007}}</ref> The first nautical transit of the north pole was made in 1958 by the submarine [[USS Nautilus (SSN-571)|USS ''Nautilus'']], and the first surface nautical transit occurred in 1977 by the [[icebreaker]] [[Arktika (1972 nuclear icebreaker)|NS ''Arktika'']].

Since 1937, [[Soviet]] and Russian manned [[drifting ice station]]s have extensively monitored the Arctic Ocean. Scientific settlements were established on the drift ice and carried thousands of kilometres by [[ice floe]]s.<ref>[http://www.whoi.edu/beaufortgyre/history/history_drifting.html North Pole drifting stations (1930s–1980s)] {{Webarchive|url=https://web.archive.org/web/20171113023915/http://www.whoi.edu/beaufortgyre/history/history_drifting.html |date=13 November 2017 }}. [[Woods Hole Oceanographic Institution]]</ref>

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

Since 1954 commercial airlines have flown over the Arctic Ocean (see [[Polar route]]).

== Geography ==
[[File:IBCAO betamap.jpg|upright=1.5|thumb|A [[Bathymetry|bathymetric]]/[[Topography|topographic]] map of the Arctic Ocean and the surrounding lands.]]
[[File:Arctic.svg|thumb|upright=1.5|The [[Arctic]] region; of note, the region's southerly border on this map is depicted by a red [[Contour line#Temperature and related subjects|isotherm]], with all territory to the north having an average temperature of less than {{Convert|10|C}} in July.]]

===Size===
The Arctic Ocean occupies a roughly circular basin and covers an area of about {{convert|14056000|km2|abbr=on}}, almost the size of [[Antarctica]].<ref name=nyt>{{cite book |editor-first=John W. |editor-last=Wright | date=2006 | title=The New York Times Almanac |url=https://archive.org/details/newyorktimes200600wrig |url-access=registration | edition=2007 | publisher=Penguin Books | location=New York | isbn=978-0-14-303820-7|page=[https://archive.org/details/newyorktimes200600wrig/page/455 455]}}</ref><ref name="Oceans of the World">{{cite web|url=http://mset.rst2.edu/portfolios/d/drewes_c/Integrating%20Technologies/Oceans%20of%20the%20World.pdf |archive-url=https://web.archive.org/web/20110719035421/http://mset.rst2.edu/portfolios/d/drewes_c/Integrating%20Technologies/Oceans%20of%20the%20World.pdf |url-status=dead |archive-date=19 July 2011 |title=Oceans of the World |publisher=rst2.edu |access-date=28 October 2010 }}</ref> The coastline is {{convert|45390|km|abbr=on}} long.<ref name=nyt /><ref name="Arctic Ocean Fast Facts">{{cite web|url=http://wwf.panda.org/what_we_do/where_we_work/arctic/area/species/polarbear/habitat/|title=Arctic Ocean Fast Facts|publisher=wwf.pandora.org (World Wildlife Foundation)|access-date=28 October 2010| archive-url= https://web.archive.org/web/20101029234119/http://wwf.panda.org/what_we_do/where_we_work/arctic/area/species/polarbear/habitat/| archive-date= 29 October 2010 | url-status= live}}</ref> It is the only [[ocean]] smaller than [[Russia]], which has a land area of {{convert|16377742|km2|abbr=on}}.

=== Surrounding land and exclusive economic zones===
The Arctic Ocean is surrounded by the land masses of Eurasia (Russia and Norway), North America ([[Canada]] and the U.S. state of Alaska), Greenland, and [[Iceland]].

{| class="wikitable sortable" style="font-size:100%"
|-
!colspan=3|Arctic [[exclusive economic zone]]s<ref>{{Cite web|url=http://www.seaaroundus.org/data/#/eez|title=Sea Around Us &#124; Fisheries, Ecosystems and Biodiversity|website=seaaroundus.org}}</ref>
|-
!rowspan=2|Country segment
!colspan=2|Area
|-
!km<sup>2</sup>
!sq mi
|-
| [[Laptev Sea]] to [[Chukchi Sea]], Russia || {{convert|2,088,075|km2|sqmi|disp=table|sortable=on}}
|-
| [[Kara Sea]], Russia || {{convert|1,058,129|km2|sqmi|disp=table|sortable=on}}
|-
| [[Barents Sea]], Russia || {{convert|1,199,008|km2|sqmi|disp=table|sortable=on}}
|-
| Mainland Norway || {{convert|935,397|km2|sqmi|disp=table|sortable=on}}
|-
| [[Svalbard Island]], Norway || {{convert|804,907|km2|sqmi|disp=table|sortable=on}}
|-
| [[Jan Mayen Island]], Norway || {{convert|292,189|km2|sqmi|disp=table|sortable=on}}
|-
| Mainland Iceland || {{convert|756,112|km2|sqmi|disp=table|sortable=on}}
|-
| Mainland Greenland || {{convert|2,278,113|km2|sqmi|disp=table|sortable=on}}
|-
| [[Eastern Canada|East Coast]] || {{convert|2,276,594|km2|sqmi|disp=table|sortable=on}}
|-
| [[Arctic]] Canada || {{convert|3,021,355|km2|sqmi|disp=table|sortable=on}}
|-
| [[Arctic]] United States || {{convert|508,814|km2|sqmi|disp=table|sortable=on}}
|-
| Other || {{convert|1,500,000|km2|sqmi|disp=table|sortable=on}}
|- style="background:#9acdff;"
|Arctic Ocean total || {{convert|14,056,000|km2|sqmi|disp=table|sortable=on}}
|}
Note: Some parts of the areas listed in the table are located in the [[Atlantic Ocean]]. Other consists of [[Gulf]]s, [[Strait]]s, [[Channel (geography)|Channel]]s and other parts without specific names and excludes [[Exclusive Economic Zones]].

=== Subareas and connections ===
{{Main|Borders of the oceans#Arctic Ocean}}

The Arctic Ocean is connected to the [[Pacific Ocean]] by the [[Bering Strait]] and to the Atlantic Ocean through the [[Greenland Sea]] and [[Labrador Sea]].<ref name=Pidwirny /> (The [[Iceland Sea]] is sometimes considered part of the Greenland Sea, and sometimes separate.)

The largest seas in the Arctic Ocean:<ref>{{Cite web|url=https://www.livescience.com/29533-the-worlds-biggest-oceans-and-seas.html|title=The World's Biggest Oceans and Seas|first=Remy |last=Melina|website=livescience.com|date=4 June 2010}}</ref><ref>{{Cite web|url=https://www.worldatlas.com/|title=World Map / World Atlas / Atlas of the World Including Geography Facts and Flags - WorldAtlas.com|website=WorldAtlas}}</ref><ref>{{Cite web|url=http://listofseas.com/|title=List of seas|website=listofseas.com}}</ref>
{{div col|colwidth=28em}}
# [[Barents Sea]]—{{convert|1.4|e6km2|sqmi|abbr=unit}}
# [[Hudson Bay]]—{{convert|1.23|e6km2|sqmi|abbr=unit}}  (sometimes not included)
# [[Greenland Sea]]—{{convert|1.205|e6km2|sqmi|abbr=unit}}
# [[East Siberian Sea]]—{{convert|987,000|km2|sqmi|abbr=on}}
# [[Kara Sea]]—{{convert|926,000|km2|sqmi|abbr=on}}
# [[Laptev Sea]]—{{convert|662,000|km2|sqmi|abbr=on}}
# [[Chukchi Sea]]—{{convert|620,000|km2|sqmi|abbr=on}}
# [[Beaufort Sea]]—{{convert|476,000|km2|sqmi|abbr=on}}
# [[Amundsen Gulf]]—{{convert|93,000|km2|sqmi|abbr=on}}
# [[White Sea]]—{{convert|90,000|km2|sqmi|abbr=on}}
# [[Pechora Sea]]—{{convert|81,263|km2|sqmi|abbr=on}}
# [[Lincoln Sea]]—{{convert|64,000|km2|sqmi|abbr=on}}
# [[Prince Gustaf Adolf Sea]]
# [[Queen Victoria Sea]]
# [[Wandel Sea]]
{{div col end}}

Different authorities put various marginal seas in either the Arctic Ocean or the Atlantic Ocean, including: [[Hudson Bay]],<ref name="Wright2001">{{cite book |last=Wright |first=John |title=The New York Times Almanac 2002 |url=https://books.google.com/books?id=G81HonU81pAC&pg=PA459 |access-date=29 November 2010 |date=30 November 2001 |publisher=Psychology Press |isbn=978-1-57958-348-4 |page=459}}</ref><ref>{{cite web|url=https://www.iho.int/mtg_docs/com_wg/S-23WG/S-23WG_Misc/Draft_2002/Draft_2002.htm|title=IHO Publication S-23 Limits of Oceans and Seas; Chapter 9: Arctic Ocean|publisher=International Hydrographic Organization|date=2002|access-date=2017-07-01|archive-url=https://web.archive.org/web/20140202105534/http://www.iho.int/mtg_docs/com_wg/S-23WG/S-23WG_Misc/Draft_2002/Draft_2002.htm|archive-date=2014-02-02|url-status=dead}}</ref><ref name="Calow1999">{{cite book |last=Calow |first=Peter |title=Blackwell's concise encyclopedia of environmental management |url=https://books.google.com/books?id=0E0LP-pPCWwC&pg=PA7 |access-date=29 November 2010 |date=12 July 1999 |publisher=Wiley-Blackwell |isbn=978-0-632-04951-6 |page=7}}</ref><ref name="LewisJones2000">{{cite book |editor-last1=Lewis |editor-first1=Edward Lyn |editor-last2=Jones |editor-first2=E. Peter |display-editors=etal |title=The Freshwater Budget of the Arctic Ocean|url=https://books.google.com/books?id=sZX_p5IKAxUC&pg=PA282|access-date=26 November 2010|year=2000|publisher=Springer|isbn=978-0-7923-6439-9|pages=101, 282–283}}</ref><ref name="McColl2005">{{cite book |last=McColl |first=R.W. |title=Encyclopedia of World Geography |url=https://books.google.com/books?id=DJgnebGbAB8C&pg=PA57 |access-date=26 November 2010 |year=2005 |publisher=Infobase Publishing |isbn=978-0-8160-5786-3 |page=57}}</ref><ref name="EarleGlover2008">{{cite book |last1=Earle |first1=Sylvia A. |last2=Glover |first2=Linda K. |title=Ocean: An Illustrated Atlas |url=https://books.google.com/books?id=sluNhV-8pbwC&pg=PA112 |access-date=26 November 2010 |year=2008 |publisher=National Geographic Books |isbn=978-1-4262-0319-0 |page=112}}</ref><ref name="Reddy2001">{{cite book |last=Reddy |first=M. P. M. |title=Descriptive Physical Oceanography |url=https://books.google.com/books?id=2NC3JmKI7mYC&pg=PA8 |access-date=26 November 2010 |year=2001 |publisher=Taylor & Francis |isbn=978-90-5410-706-4 |page=8}}</ref><ref name="DayGarratt2006">{{cite book |last1=Day |first1=Trevor |last2=Garratt |first2=Richard |title=Oceans |url=https://books.google.com/books?id=VY9mCXOXIvQC&pg=PA21 |access-date=26 November 2010 |year=2006 |publisher=Infobase Publishing |isbn=978-0-8160-5327-8 |page=21}}</ref>
[[Baffin Bay]], the [[Norwegian Sea]], and [[Hudson Strait]].

=== Islands ===
{{main|List of islands in the Arctic Ocean}}
The main islands and archipelagos in the Arctic Ocean are, from the [[prime meridian]] west:
* [[Jan Mayen]] (Norway)
* [[Iceland]]
* [[Greenland]]
* [[Arctic Archipelago]] (Canada, includes the [[Queen Elizabeth Islands]] and [[Baffin Island]])
* [[Wrangel Island]] (Russia)
* [[New Siberian Islands]] (Russia)
* [[Severnaya Zemlya]] (Russia)
* [[Novaya Zemlya]] (Russia, includes [[Severny Island]] and [[Yuzhny Island]])
* [[Franz Josef Land]] (Russia)
* [[Svalbard]] (Norway, including [[Bear Island (Norway)|Bear Island]])

=== Ports ===
There are several ports and [[harbor|harbour]]s on the Arctic Ocean.<ref name=CIA>[https://www.cia.gov/the-world-factbook/oceans/arctic-ocean/ Arctic Ocean] {{Webarchive|url=https://web.archive.org/web/20221204191036/https://www.cia.gov/the-world-factbook/oceans/arctic-ocean/ |date=4 December 2022 }}. CIA World Fact Book</ref>

* Alaska
** [[Utqiaġvik]] (Barrow)
** [[Prudhoe Bay, Alaska|Prudhoe Bay]]
* [[Canada]]
** [[Manitoba]]: [[Churchill, Manitoba|Churchill]] ([[Port of Churchill]])
** [[Nunavut]]: [[Nanisivik]] ([[Nanisivik Naval Facility]])<ref>{{cite web
 |title=Backgrounder – Expanding Canadian Forces Operations in the Arctic
 |url=http://www.pm.gc.ca/eng/media.asp?id=1785 |date=10 August 2007|publisher=Canadian Armed Forces Arctic Training Centre
 |access-date=17 August 2007
 |url-status=dead
 |archive-url=https://web.archive.org/web/20080602062840/http://www.pm.gc.ca/eng/media.asp?id=1785
 |archive-date=2 June 2008
}}</ref>
** [[Tuktoyaktuk]] and [[Inuvik]] in the [[Northwest Territories]]
* Greenland: [[Nuuk]] ([[Nuuk Port and Harbour]])
* [[Norway]]
** Mainland: [[Kirkenes]] and [[Vardø (town)|Vardø]]
** [[Svalbard]]: [[Longyearbyen]]
* Iceland
** [[Akureyri]]
* Russia 
** Barents Sea: [[Murmansk]] 
** White Sea: [[Arkhangelsk]]
** Kara Sea: [[Labytnangi]], [[Salekhard]], [[Dudinka]], [[Igarka]] and [[Dikson (urban-type settlement)|Dikson]]
** Laptev Sea: [[Tiksi]] 
** East Siberian Sea: [[Pevek]]

=== {{anchor|Arctic_shelf}}Arctic shelves ===
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The ocean's Arctic shelf comprises a number of [[continental shelf|continental shelves]], including the Canadian Arctic shelf, underlying the [[Canadian Arctic Archipelago]], and the [[Continental shelf of Russia|Russian continental shelf]], which is sometimes called the "Arctic Shelf" because it is larger. The Russian continental shelf consists of three separate, smaller shelves: the Barents Shelf, [[Chukchi Sea Shelf]] and [[Siberian Shelf]]. Of these three, the Siberian Shelf is the largest such shelf in the world; it holds large oil and gas reserves. The Chukchi shelf forms the border between Russian and the United States as stated in the [[USSR–USA Maritime Boundary Agreement]]. The whole area is subject to international [[Territorial claims in the Arctic|territorial claims]].

The [[Chukchi Plateau]] extends from the Chukchi Sea Shelf.

=== Underwater features ===
An [[Mid-ocean ridge|underwater ridge]], the [[Lomonosov Ridge]], divides the deep sea [[Arctic Basin|North Polar Basin]] into two [[oceanic basin]]s: the [[Eurasian Basin]], which is {{convert|4000|–|4500|m|ft|abbr=on}} deep, and the [[Amerasian Basin]] (sometimes called the North American or Hyperborean Basin), which is about {{convert|4000|m|abbr=on}} deep. The [[bathymetry]] of the ocean bottom is marked by [[fault block]] ridges, [[abyssal plain]]s, [[Oceanic trench|ocean deeps]], and basins. The average depth of the Arctic Ocean is {{convert|1038|m|abbr=on}}.<ref>{{cite web | title=The Mariana Trench – Oceanography| work=marianatrench.com | url=http://www.marianatrench.com/mariana_trench-oceanography.htm | date=4 April 2003| access-date=2 December 2006 | archive-url= https://web.archive.org/web/20061207210451/http://www.marianatrench.com/mariana_trench-oceanography.htm| archive-date= 7 December 2006 | url-status= live}}</ref> The deepest point is [[Molloy Hole]] in the [[Fram Strait]], at about {{convert|5550|m|abbr=on|}}.<ref>{{Cite web|url=https://fivedeeps.com/wp-content/uploads/2019/09/Molloy-Press-Release-final.pdf|title=Five Deeps Expedition is complete after historic dive to the bottom of the Arctic Ocean}}</ref>

The two major basins are further subdivided by ridges into the [[Canada Basin]] (between Beaufort Shelf of North America and the [[Alpha Ridge]]), [[Makarov Basin]] (between the Alpha and Lomonosov Ridges), [[Amundsen Basin]] (between Lomonosov and [[Gakkel Ridge|Gakkel]] ridges), and [[Nansen Basin]] (between the Gakkel Ridge and the continental shelf that includes the [[Franz Josef Land]]).

==Geology==
{{See also|Petroleum exploration in the Arctic}}
The crystalline basement rocks of mountains around the Arctic Ocean were recrystallized or formed during the Ellesmerian orogeny, the regional phase of the larger [[Caledonian orogeny]] in the [[Paleozoic]] Era. Regional subsidence in the [[Jurassic]] and [[Triassic]] periods led to significant sediment deposition, creating many of the reservoirs for current day oil and gas deposits. During the [[Cretaceous]] period, the Canadian Basin opened, and tectonic activity due to the assembly of Alaska caused hydrocarbons to migrate toward what is now Prudhoe Bay. At the same time, sediments shed off the rising Canadian Rockies built out the large Mackenzie Delta.

The rifting apart of the [[supercontinent]] [[Pangea]], beginning in the Triassic period, opened the early Atlantic Ocean. Rifting then extended northward, opening the Arctic Ocean as [[mafic]] oceanic crust material erupted out of a branch of Mid-Atlantic Ridge. The Amerasia Basin may have opened first, with the [[Chukchi Plateau|Chukchi Borderland]] moved along to the northeast by transform faults. Additional spreading helped to create the "triple-junction" of the Alpha-Mendeleev Ridge in the [[Late Cretaceous]] [[Epoch (geology)|epoch]].

Throughout the [[Cenozoic]] Era, the subduction of the Pacific plate, the collision of India with Eurasia, and the continued opening of the North Atlantic created new hydrocarbon traps. The seafloor began spreading from the Gakkel Ridge in the [[Paleocene]] Epoch and the [[Eocene]] Epoch, causing the Lomonosov Ridge to move farther from land and subside.

Because of sea ice and remote conditions, the geology of the Arctic Ocean is still poorly explored. The Arctic Coring Expedition drilling shed some light on the Lomonosov Ridge, which appears to be continental crust separated from the Barents-Kara Shelf in the Paleocene and then starved of sediment. It may contain up to 10&nbsp;billion barrels of oil. The Gakkel Ridge rift is also poorly understand and may extend into the Laptev Sea.<ref>{{cite news|title=Geological History of the Arctic Ocean|year=2007|publisher=GEO ExPro|url=https://assets.geoexpro.com/legacy-files/articles/A%20Brief%20Geological%20History%20of%20the%20Arctic%20Ocean.pdf|author=Whaley, Jane|access-date=26 November 2019|archive-date=3 October 2022|archive-url=https://web.archive.org/web/20221003232453/https://assets.geoexpro.com/legacy-files/articles/A%20Brief%20Geological%20History%20of%20the%20Arctic%20Ocean.pdf|url-status=dead}}</ref><ref>{{cite book |url=https://books.google.com/books?id=-s1fDwAAQBAJ&q=geology+of+the+arctic+ocean |title=Geologic Structures of the Arctic Basin |publisher=Springer |year=2019 |isbn=9783319777429 |editor-last=Piskarev |editor-first=Alexey |editor-last2=Poselov |editor-first2=Victor |editor-last3=Kaminsky |editor-first3=Valery}}</ref>

== Oceanography ==

=== Water flow ===
[[File:BrnBld BeringToFram.svg|left|upright=2.15|thumb|Distribution of the major [[water mass]] in the Arctic Ocean. The section sketches the different water masses along a vertical section from [[Bering Strait]] over the geographic [[North Pole]] to [[Fram Strait]]. As the [[Ocean stratification|stratification]] is stable, deeper water masses are denser than the layers above.]]

[[File:Temperature and salinity profiles in the Arctic Ocean.svg|thumb|upright=1.5|Density structure of the upper {{convert|1200|m|abbr=on}} in the Arctic Ocean. Profiles of temperature and salinity for the Amundsen Basin, the Canadian Basin and the Greenland Sea are sketched.]]
In large parts of the Arctic Ocean, the top layer (about {{convert|50|m|abbr=on|disp=sqbr}}) 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 rivers ([[Ob River|Ob]], [[Yenisei River|Yenisei]], [[Lena River|Lena]], [[Mackenzie River|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 rise with increasing depth.
[[File:Copepodkils.jpg|thumb|A [[copepod]]]]

Because of its relative isolation from other oceans, the Arctic Ocean has a uniquely complex system of water flow. It resembles some hydrological features of the [[Mediterranean Sea]], referring to its deep waters having only limited communication through the Fram Strait with the [[Atlantic Basin]], "where the circulation is dominated by thermohaline forcing".<ref name=Tomczak>[Regional Oceanography: An Introduction. Tomczak, Godfrey. Retrieved 18 November 2013.]</ref> The Arctic Ocean has a total volume of 18.07 × 10<sup>6</sup> km<sup>3</sup>, equal to about 1.3% of the World Ocean. Mean surface circulation is predominantly cyclonic on the [[Eurasian]] side and anticyclonic in the [[Canadian Basin]].<ref name=Talley>{{cite book|title=Descriptive Physical Oceanography|author= Pickard, George L. |author2=Emery, William J. |publisher=Pergamon|isbn=978-1-4832-7877-3|year=1982 }}</ref>

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 Bottom Water and begins around {{convert|900|m|abbr=on}} depth.<ref name=Tomczak /> It is composed of the densest water in the World Ocean and has two main sources: Arctic shelf water and Greenland Sea Deep Water. Water in the shelf region that begins as inflow from the Pacific passes through the narrow Bering Strait at an average rate of 0.8 [[Sverdrup]]s and reaches the [[Chukchi Sea]].<ref name=Nature>{{Cite web |url=http://www.nature.com/scitable/knowledge/library/arctic-ocean-circulation-going-around-at-the-102811553 |title=Arctic Ocean Circulation: Going Around at the Top of the World. Retrieved 2 November 2013. |access-date=12 November 2013 |archive-date=12 November 2013 |archive-url=https://web.archive.org/web/20131112042040/http://www.nature.com/scitable/knowledge/library/arctic-ocean-circulation-going-around-at-the-102811553 |url-status=live }}</ref> 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&nbsp;cm/s.<ref name=Talley /> This process leaves dense, salty waters in the sea that sink over the continental shelf into the western Arctic Ocean and create a halocline.<ref name=Polar>[http://polardiscovery.whoi.edu/arctic/circulation.html Arctic Ocean Circulation] {{Webarchive|url=https://web.archive.org/web/20130115040516/http://polardiscovery.whoi.edu/arctic/circulation.html |date=15 January 2013 }}. Polar Discovery</ref>
[[File:Nares strait border (Kennedy channel).png|thumb|left| The [[Kennedy Channel]].]]
This water is met by 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.<ref name=Tomczak /> 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 {{convert|150|-|900|m|abbr=on}} is a water mass referred to as Atlantic Water. Inflow from the [[North Atlantic Current]] enters through the Fram Strait, cooling and sinking to form the deepest layer of the halocline, where it circles the [[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 Ocean Boundary Current.<ref name=Nature /> It flows slowly, at about 0.02&nbsp;m/s.<ref name=Tomczak /> Atlantic Water has the same salinity as Arctic Bottom Water but is much warmer (up to {{convert|3|°C|disp=sqbr}}). In fact, this water mass is actually warmer than the surface water and remains submerged only due to the role of salinity in density.<ref name=Tomczak /> When water reaches the basin, it is pushed by strong winds into a large circular current called the [[Beaufort Gyre]]. Water in the Beaufort Gyre is far less saline than that of the Chukchi Sea due to inflow from large Canadian and Siberian rivers.<ref name=Polar />
 
The final defined water mass in the Arctic Ocean is called Arctic Surface Water and is found in the depth range of {{convert|150|-|200|m|abbr=on}}. 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.<ref name=Tomczak /><ref>Lenn, Y., Rippeth, T. P., Old, C., Bacon, S., Polyakov, I., Ivanov, V. & Holemann, J (2011). Journal of Physical Oceanography. 41(3), 531–547</ref> As it is entrained, it cools and acts a heat shield for the surface layer on account of weak mixing between layers.<ref>Lenn, Y. D., Wiles, P. J., Torres-Valdes, S., Abrahamsen, E. P., Rippeth, T. P., Simpson, J. H., Bacon, S., Laxon, S. W., Polyakov, I., Ivanov, V. & Kirillov, S. (2009). Vertical mixing at intermediate depths in the Arctic boundary current. Geophysical Research Letters. 36, p. L05601</ref><ref>Fer, I. (2009). Weak vertical diffusion allows maintenance of cold halocline in the central Arctic. Atmospheric and Oceanic Science Letters 2(3):148–152.</ref>

However, over the past couple of decades a combination of the warming<ref>Barton, B., Lenn, Y-D. & Lique, C. (2018). Observed atlantification of the Barents Sea causes the Polar Front to limit the expansion of winter sea ice, Journal of Physical Oceanography, 28(8), 1849-1866</ref> and the shoaling of Atlantic water<ref>Igor V. Polyakov1, Andrey V. Pnyushkov, Matthew B. Alkire, Igor M. Ashik, Till M. Baumann, Eddy C. Carmack, Ilona Goszczko, John Guthrie, Vladimir V. Ivanov, Torsten Kanzow, Richard Krishfield, Ronald Kwok, Arild Sundfjord, James Morison, Robert Rember, Alexander Yulin (2017). Greater role for Atlantic inflows on sea-ice loss in the Eurasian Basin of the Arctic Ocean. Science, 356(6335), 285–291</ref> are leading to the increasing influence of Atlantic water heat in melting sea ice in the eastern Arctic. The most recent estimates, for 2016–2018, indicate the oceanic heat flux to the surface has now overtaken the atmospheric flux in the eastern Eurasian Basin.<ref>Polyakov, I., Rippeth, T., Fer, I., Alkire, M., Baumann, T., Carmack, E., Ivanov, V., Janout, M. A., Padman, L., Pnyushkov, A. & Rember, R (2020). Weakening of the cold halocline layer exposes sea ice to oceanic heat in the eastern Arctic Ocean. Journal of Climate, 33(18), 8107-8123</ref> Over the same period the weakening halocline stratification has coincided with increasing upper ocean currents thought to be associated with declining sea ice, indicate increasing mixing in this region.<ref>Polyakov, I., Rippeth, T., Fer, I., Baumann, T., Carmack, E., Ivanov, V., Janout, M. A., Padman, L., Pnyushkov, A. & Rember, R (2020). Intensification of Near-Surface Currents and Shear in the Eastern Arctic Ocean: A More Dynamic Eastern Arctic Ocean, Geophysical Research Letters, 47(16), e2020GL089469</ref> In contrast direct measurements of mixing in the western Arctic indicate the Atlantic water heat remains isolated at intermediate depths even under the 'perfect storm' conditions of the [[Great Arctic Cyclone of 2012]].<ref>Lincoln, B., Rippeth, T., Lenn, Y-D., [[Mary-Louise Timmermans|Timmermans, M-L.]], Williams, W. & Bacon, S (2016). Wind-driven mixing at intermediate depths in an ice-free Arctic Ocean. Geophysical Research Letters, 43(18), 9749-9756</ref>

Waters originating in the Pacific and Atlantic both exit through the Fram Strait between Greenland and Svalbard Island, which is about {{convert|2700|m|abbr=on}} deep and {{convert|350|km|abbr=on}} wide. This outflow is about 9 Sv.<ref name=Nature /> The width of the 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]], which concentrates outflow to the East Greenland Current on the western side and inflow to the [[Norwegian Current]] on the eastern side.<ref name=Tomczak /> Pacific water also exits along the west coast of Greenland and the Hudson Strait (1–2 Sv), providing nutrients to the Canadian Archipelago.<ref name=Nature />

As noted, the process of ice formation and movement is a key driver in Arctic Ocean circulation and the formation of water masses. With this dependence, the Arctic Ocean experiences variations due to seasonal changes in sea ice cover. Sea ice movement is the result of wind forcing, which is related to a number of meteorological conditions that the 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.<ref name=Talley /> 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 that drives strong northerly winds through the 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]], 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 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 Oscillation and [[Atlantic Multidecadal Oscillation]].<ref name=Talley />

=== Sea ice ===
[[File:2007 Arctic Sea Ice.jpg|thumb|Sea cover in the Arctic Ocean, showing the median, 2005 and 2007 coverage<ref>{{cite web|url=http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17047 |title=Continued Sea Ice Decline in 2005|url-status=dead|archive-url=https://web.archive.org/web/20061007164907/http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17047 |archive-date=7 October 2006 |others=Graph by Robert Simmon, [[Earth Observatory]], and Walt Meier, [[NSIDC]]; photo by Nathaniel B. Palmer, [[NOAA]] |access-date=7 December 2006}}</ref>]]
{{Main|Arctic ice pack}}
[[File:Refueling Twin Otter.jpg|thumb|On the sea ice of the Arctic Ocean temporary logistic stations may be installed, Here, a [[Twin Otter]] is refueled on the pack ice at 86°N, 76°43‘W.]]

Much of the Arctic Ocean is covered by sea ice that varies in extent and thickness seasonally. The mean extent of the Arctic sea ice has been continuously decreasing in the last decades, declining at a rate of currently 12.85% per decade since 1980 from the average winter value of {{convert|15600000|km2|mi2|-2|abbr=on}}.<ref>{{Cite web|last=Change|first=NASA Global Climate|title=Arctic Sea Ice Minimum {{!}} NASA Global Climate Change|url=https://climate.nasa.gov/vital-signs/arctic-sea-ice|access-date=2020-09-10|website=Climate Change: Vital Signs of the Planet}}</ref> The seasonal variations are about {{convert|7000000|km2|mi2|-2|abbr=on}}, 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.<ref>[http://nsidc.org/data/seaice_index/ Sea Ice Index] {{Webarchive|url=https://web.archive.org/web/20200202220337/http://nsidc.org/data/seaice_index/ |date=2 February 2020 }}. Nsidc.org. Retrieved on 6 March 2011.</ref><ref>[http://arctic.atmos.uiuc.edu/cryosphere/ Polar Sea Ice Cap and Snow – Cryosphere Today] {{Webarchive|url=https://web.archive.org/web/20110223161943/http://arctic.atmos.uiuc.edu/cryosphere/ |date=23 February 2011 }}. Arctic.atmos.uiuc.edu (23 September 2007). Retrieved on 2011-03-06.</ref><ref name="Buixade Farre 2014">{{cite journal|first1=Albert |last1=Buixadé Farré |first2=Scott R. |last2=Stephenson |first3=Linling |last3=Chen |first4=Michael |last4=Czub |first5=Ying |last5=Dai |first6=Denis |last6=Demchev |first7=Yaroslav |last7=Efimov |first8=Piotr |last8=Graczyk |first9=Henrik |last9=Grythe |first10=Kathrin |last10=Keil |first11=Niku |last11=Kivekäs |first12=Naresh |last12=Kumar |first13=Nengye |last13=Liu |first14=Igor |last14=Matelenok |first15=Mari |last15=Myksvoll |first16=Derek |last16=O'Leary |first17=Julia |last17=Olsen |first18=Sachin |last18=Pavithran .A.P. |first19=Edward |last19=Petersen |first20=Andreas |last20=Raspotnik |first21=Ivan |last21=Ryzhov |first22=Jan |last22=Solski |first23=Lingling |last23=Suo |first24=Caroline |last24=Troein |first25=Vilena |last25=Valeeva |first26=Jaap |last26=van Rijckevorsel |first27=Jonathan |last27=Wighting |date=16 October 2014 |title=Commercial Arctic shipping through the Northeast Passage: Routes, resources, governance, technology, and infrastructure |journal=[[Polar Geography]] |volume=37 |issue=4 |pages=298–324 |doi=10.1080/1088937X.2014.965769 |doi-access=free |hdl=2440/112024 |hdl-access=free }}</ref>

[[Iceberg]]s occasionally break away from northern [[Ellesmere Island]], and icebergs are formed from [[glacier]]s in western Greenland and extreme northeastern Canada. Icebergs are not sea ice but may become embedded in the pack ice. Icebergs pose a hazard to ships, of which the [[RMS Titanic|''Titanic'']] is one of the most famous. The ocean is virtually icelocked from October to June, and the [[superstructure]] of ships are subject to [[Icing (nautical)|icing]] from October to May.<ref name=CIA /> Before the advent of modern icebreakers, ships sailing the Arctic Ocean risked being trapped or crushed by sea ice (although the ''[[SS Baychimo|Baychimo]]'' drifted through the Arctic Ocean untended for decades despite these hazards).

== Climate ==
{{See also|Climate change in the Arctic}}
[[File:North Pole Sea Ice 1990-1999.ogv|thumb|Changes in ice between 1990 and 1999]]
The 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.<ref>{{cite book|last1=Serreze|first1=Mark C|last2=Barry|first2=Roger G|title=The Arctic Climate System|date=2014|publisher=Cambridge University Press|location=New York|isbn=978-1-107-03717-5|pages=168–172|edition=2nd}}</ref> [[Cyclone]]s are only common on the Atlantic side.<ref name="ReferenceA">{{cite journal|last1=Simmonds|first1=Ian|last2=Burke|first2=Craig|last3=Keay|first3=Kevin|title=Arctic climate change as manifest in cyclone behavior|journal=Journal of Climate|date=2008|volume=21|issue=22|pages=5777|doi=10.1175/2008JCLI2366.1|bibcode=2008JCli...21.5777S|doi-access=free}}</ref> Summers are characterized by continuous [[daylight]] ([[midnight sun]]), and air temperatures can rise slightly above {{convert|0|°C}}. Cyclones are more frequent in summer and may bring rain or snow.<ref name="ReferenceA" /> It is cloudy year-round, with mean cloud cover ranging from 60% in winter to over 80% in summer.<ref>{{cite book|last1=Serreze|first1=Mark C|last2=Barry|first2=Roger G|title=The Arctic Climate System|date=2014|publisher=Cambridge University Press|location=New York|isbn=978-1-107-03717-5|pages=56–59|edition=2nd}}</ref>

The temperature of the surface water of the Arctic Ocean is fairly constant at approximately {{Convert|−1.8|C}}, near the [[Melting point|freezing point]] of [[seawater]].

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 {{convert|100|–|150|m|abbr=on}} of ocean water cools to the freezing point for sea ice to form.<ref>{{cite web|url=http://nsidc.org/seaice/intro.html |title=NSIDC sea ice |access-date=10 February 2010 |archive-url=https://web.archive.org/web/20100117114629/http://nsidc.org/seaice/intro.html |archive-date=17 January 2010 |url-status=dead }}</ref> In the winter, the relatively warm ocean water exerts a moderating influence, even when covered by ice. This is one reason why the Arctic does not experience the extreme temperatures seen on the [[Antarctica|Antarctic continent]].

There is considerable seasonal variation in how much pack ice of the Arctic ice pack covers the Arctic Ocean. Much of the 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 {{convert|20|–|50|cm|in|abbr=on}} over the frozen ocean.

The climate of the Arctic region has varied significantly during the Earth's history. During the [[Paleocene–Eocene Thermal Maximum]] 55&nbsp;million years ago, when the global climate underwent a warming of approximately {{convert|5–8|C-change|0}}, the region reached an average annual temperature of {{convert|10|-|20|C|F}}.<ref>{{Cite journal|last1=McInerney|first1=Francesca A.|last2=Wing|first2=Scott L.|date=2011-04-25|title=The Paleocene-Eocene Thermal Maximum: A Perturbation of Carbon Cycle, Climate, and Biosphere with Implications for the Future|url=https://www.annualreviews.org/doi/10.1146/annurev-earth-040610-133431|journal=Annual Review of Earth and Planetary Sciences|volume=39|issue=1|pages=489–516|doi=10.1146/annurev-earth-040610-133431|bibcode=2011AREPS..39..489M|issn=0084-6597|url-access=subscription}}</ref><ref>{{Cite journal|last1=Nunes|first1=Flavia|last2=Norris|first2=Richard D.|date=2006-01-01|title=Abrupt reversal in ocean overturning during the Palaeocene/Eocene warm period|url=http://adsabs.harvard.edu/abs/2006Natur.439...60N|journal=Nature|volume=439|issue=7072|pages=60–63|doi=10.1038/nature04386|pmid=16397495|bibcode=2006Natur.439...60N|s2cid=4301227}}</ref><ref name=Shellito2003>{{cite journal
| author = Shellito, C.J.
|author2= Sloan, L.C.|author3= Huber, M.
| date = 2003
| title = Climate model sensitivity to atmospheric CO2 levels in the Early-Middle Paleogene
| journal = Palaeogeography, Palaeoclimatology, Palaeoecology
| volume = 193
| issue = 1
| pages = 113–123
| doi = 10.1016/S0031-0182(02)00718-6
| bibcode = 2003PPP...193..113S
}}</ref> The surface waters of the northernmost<ref>Drill cores were recovered from the [[Lomonosov Ridge]], presently at 87°N</ref> Arctic Ocean warmed, seasonally at least, enough to support tropical lifeforms (the [[dinoflagellate]]s ''Apectodinium augustum'') requiring surface temperatures of over {{convert|22|C|abbr=on}}.<ref name=Sluijs2006>{{cite journal
| author = Sluijs, A. |author2=Schouten, S. |author3=Pagani, M. |author4=Woltering, M. |author5=Brinkhuis, H. |author6=Damsté, J.S.S. |author7=Dickens, G.R. |author8=Huber, M. |author9=Reichart, G.J. |author10=Stein, R.
| date = 2006
| title = Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum
| journal = Nature
| volume = 441
| issue = 7093
| pages = 610–613
| doi = 10.1038/nature04668
| pmid = 16752441
|display-authors=etal|bibcode=2006Natur.441..610S|hdl=11250/174280 |s2cid=4412522 |url=https://brage.npolar.no/npolar-xmlui/bitstream/11250/174280/1/SluijsNature2006.pdf}}</ref>

Currently, the Arctic region is warming twice as fast as the rest of the planet.<ref>{{Cite news|last=Pierre-Louis|first=Kendra|date=2019-12-10|title=Climate Change Is Ravaging the Arctic, Report Finds|language=en-US|work=The New York Times|url=https://www.nytimes.com/2019/12/10/climate/climate-change-arctic-warming.html|access-date=2020-09-11|issn=0362-4331}}</ref><ref name="auto">{{Cite web|last=Crew|first=Bec|title=The Arctic Is Warming Twice as Fast as The Rest of The Planet|url=https://www.sciencealert.com/the-arctic-is-warming-twice-as-fast-as-the-rest-of-the-planet|access-date=2020-09-11|website=ScienceAlert|date=15 December 2016 |language=en-gb}}</ref>

== Biology ==
[[File:Polar bears near north pole.jpg|thumb|Three [[polar bear]]s approach [[USS Honolulu (SSN-718)|USS ''Honolulu'']] near the [[North Pole]].]]
Due to the pronounced seasonality of 2–6 months of [[midnight sun]] and [[polar night]]<ref>{{Cite journal|last1= Berge|first1= J.|last2= Renaud|first2= P. E.|display-authors= 1|date= 2015|title= In the dark: A review of ecosystem processes during the Arctic polar night|journal= Progress in Oceanography|volume= 139|pages= 258–271|doi= 10.1016/j.pocean.2015.08.005|bibcode= 2015PrOce.139..258B|doi-access= free|hdl= 10037/8602|hdl-access= free}}</ref> in the Arctic Ocean, the [[primary production]] of photosynthesizing organisms such as [[ice algae]] and [[phytoplankton]] is limited to the spring and summer months (March/April to September).<ref>{{Cite journal|last1= Leu|first1= E.|last2= Søreide|first2= J. E.|last3= Hessen|first3= D. O.|display-authors= 2|date= 2011|title= Consequences of changing sea-ice cover for primary and secondary producers in the European Arctic shelf seas: Timing, quantity, and quality|journal= Progress of Oceanography|volume= 90|issue= 1–4|pages= 18–32|doi= 10.1016/j.pocean.2011.02.004|bibcode= 2011PrOce..90...18L}}</ref> Important consumers of [[primary producers]] in the central Arctic Ocean and the adjacent [[Continental shelf|shelf seas]] include [[zooplankton]], especially [[copepod]]s (''[[Calanus finmarchicus]]'', ''[[Calanus glacialis]]'', and ''[[Calanus hyperboreus]]'')<ref name="Kosobokova-2011">{{Cite journal|last1= Kosobokova|first1= K. N.|last2= Hopcroft|first2= R. R.|date= 2011|title= Patterns of zooplankton diversity through the depths of the Arctic's central basins|journal= Marine Biodiversity|volume= 41|pages= 29–50|doi= 10.1007/s12526-010-0057-9|s2cid= 23452656}}</ref> and [[Krill|euphausiids]],<ref name="Dalpadado-2012">{{Cite journal|last1= Dalpadado|first1= P.|last2= Ingvaldsen|first2= R. B.|display-authors= 1|date= 2012|title= Climate effects on Barents Sea ecosystem dynamics|journal= ICES Journal of Marine Science|volume= 69|issue= 7|pages= 1303–1316|doi= 10.1093/icesjms/fss063|doi-access= free}}</ref> as well as ice-associated [[fauna]] (e.g., [[Amphipoda|amphipods]]).<ref name="Kosobokova-2011" /> These [[primary consumers]] form an important link between the primary producers and higher [[trophic level]]s. The composition of higher trophic levels in the Arctic Ocean varies with region (Atlantic side vs. Pacific side) and with the [[sea-ice]] cover. [[Secondary consumer]]s in the [[Barents Sea]], an Atlantic-influenced Arctic shelf sea, are mainly sub-Arctic species including [[herring]], young [[Atlantic cod|cod]], and [[capelin]].<ref name="Dalpadado-2012" /> In ice-covered regions of the central Arctic Ocean, [[Boreogadus saida|polar cod]] is a central predator of primary consumers. The [[apex predator]]s in the Arctic Ocean—[[marine mammal]]s such as [[Pinniped|seals]], [[whale]]s, and [[polar bear]]s—prey upon fish.

Endangered marine species in the Arctic Ocean include [[walrus]]es and [[whale]]s. The area has a fragile [[ecosystem]], and it is especially exposed to [[Global warming|climate change]], because it warms faster than the rest of the world. [[Lion's mane jellyfish]] are abundant in the waters of the Arctic, and the [[banded gunnel]] is the only species of [[Pholidae|gunnel]] that lives in the ocean.
[[File:Minke Whale (NOAA).jpg|thumb|[[Minke whale]]]]
[[File:Walruses on ice floes.jpg|thumb|Walruses on Arctic ice floe]]

== Natural resources ==
{{See also|Natural resources of the Arctic|Territorial claims in the Arctic|Marine mammal}}

[[Petroleum]] and [[natural gas]] [[Natural gas field|fields]], [[placer deposit]]s, [[Manganese nodule|polymetallic nodules]], sand and gravel [[Construction aggregate|aggregates]], fish, seals and whales can all be found in abundance in the region.<ref name=CIA /><ref name="Buixade Farre 2014" />

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.<ref>Reynolds, Paul (25 October 2005) [http://news.bbc.co.uk/2/hi/business/4354036.stm#map The Arctic's New Gold Rush] {{Webarchive|url=https://web.archive.org/web/20180405015017/http://news.bbc.co.uk/2/hi/business/4354036.stm#map |date=5 April 2018 }}. ''BBC''.</ref> It is significant for the global [[energy market]] because it may hold 25% or more of the world's undiscovered oil and gas resources.<ref>Yenikeyeff, Shamil and Krysiek, Timothy Fenton (August 2007) [http://www.oxfordenergy.org/wpcms/wp-content/uploads/2011/01/Aug2007-TheBattleforthenextenergyfrontier-ShamilYenikeyeff-and-TimothyFentonKrysiek.pdf The Battle for the Next Energy Frontier: The Russian Polar Expedition and the Future of Arctic Hydrocarbons] {{Webarchive|url=https://web.archive.org/web/20120407110248/http://www.oxfordenergy.org/wpcms/wp-content/uploads/2011/01/Aug2007-TheBattleforthenextenergyfrontier-ShamilYenikeyeff-and-TimothyFentonKrysiek.pdf |date=7 April 2012 }}. [[Oxford Institute for Energy Studies]].</ref>

== Environmental concerns ==
{{Main|Climate change in the Arctic|Ozone depletion|Pollution in the Arctic Ocean}}

=== Arctic ice melting ===
{{further|Atlantification of the Arctic}}
The [[Arctic ice pack]] is thinning, and a seasonal hole in the [[ozone layer]] frequently occurs.<ref>{{Cite web|url=http://www.ec.gc.ca/cleanair-airpur/Linking_Today_into_Tomorrow-WS4D339983-1_En.htm|title=Erreur HTTP 404 - Non trouvé|website=ec.gc.ca}}</ref> Reduction of the area of Arctic sea ice reduces the planet's average [[albedo]], possibly resulting in global warming in a positive feedback mechanism.<ref name="Buixade Farre 2014" /><ref name="R.Black">[http://news.bbc.co.uk/2/hi/science/nature/4315968.stm Earth – melting in the heat?] {{Webarchive|url=https://web.archive.org/web/20180630003659/http://news.bbc.co.uk/2/hi/science/nature/4315968.stm |date=30 June 2018 }} Richard Black, 7 October 2005. BBC News. Retrieved 7 December 2006.</ref> Research shows that the Arctic may become ice-free in the summer for the first time in human history by 2040.<ref>[http://www.theaustralian.com.au/archive/business-old/russia-the-next-climate-recalcitrant/story-e6frg976-1111118052004 Russia the next climate recalcitrant] Peter Wilson, 17 November 2008, [[The Australian]]. Retrieved 3 November 2016.</ref><ref name="nsidc2011">{{cite web | url=https://nsidc.org/cryosphere/icelights/2011/05/when-will-arctic-lose-its-sea-ice | title=When will the Arctic lose its sea ice? | publisher=National Snow & Ice Data Center | date=May 2011 | access-date=3 November 2016}}</ref> Estimates vary for when the last time the Arctic was ice-free: 65&nbsp;million years ago when fossils indicate that plants existed there to as recently as 5,500 years ago; ice and ocean cores going back 8,000 years to the [[Holocene thermal maximum|last warm period]] or 125,000 during the [[Eemian|last intraglacial period]].<ref name="Nsidc">{{cite web | url=http://nsidc.org/arcticseaicenews/faq/#summer_ice | title=Has the Arctic Ocean always had ice in summer? | publisher=National Snow & Ice Data Center | date=February 2012 | access-date=2 November 2016}}</ref>

Warming temperatures in the Arctic may cause large amounts of fresh [[meltwater|melt-water]] to enter the north Atlantic, possibly disrupting global [[thermohaline circulation|ocean current patterns]]. Potentially severe changes in the Earth's [[climate]] might then ensue.<ref name="R.Black" />

As the extent of sea ice diminishes and [[sea level rise]]s, the effect of storms such as the [[Great Arctic Cyclone of 2012]] on open water increases, as does possible salt-water damage to vegetation on shore at locations such as the Mackenzie [[river delta|Delta]] as stronger [[storm surge]]s become more likely.<ref name=CC03513>{{cite news|title=Warmer Arctic with Less Ice Increases Storm Surge|url=http://www.climatecentral.org/news/warmer-arctic-with-less-ice-increases-storm-surge-15689|access-date=8 March 2013|newspaper=Climate Central|date=5 March 2013|author=Lauren Morello}}</ref>

Global warming has increased encounters between polar bears and humans. Reduced sea ice due to melting is causing polar bears to search for new sources of food.<ref>{{cite web |last1=Brackett |first1=Ron |title=Arctic Russian Town Declares Polar Bear Invasion Emergency After 52 Wander In |url=https://weather.com/news/news/2019-02-11-russian-archipelago-invaded-polar-bears-emergency |website=weather.com |publisher=The Weather Company |access-date=3 March 2019 |date=11 February 2019 |ref=bearinvasion |archive-date=6 March 2019 |archive-url=https://web.archive.org/web/20190306043253/https://weather.com/news/news/2019-02-11-russian-archipelago-invaded-polar-bears-emergency |url-status=dead }}</ref> Beginning in December 2018 and coming to an apex in February 2019, [[2019 mass invasion of Russian polar bears|a mass invasion of polar bears]] into the archipelago of [[Novaya Zemlya]] caused local authorities to declare a state of emergency. Dozens of polar bears were seen entering homes, public buildings and inhabited areas.<ref name='A3'>{{cite news |last1=Abellan Matamoros |first1=Cristina |title=Watch: Polar bear in Russian archipelago peeks inside a house |url=https://www.euronews.com/2019/02/12/watch-polar-bear-in-russian-archipelago-peaks-inside-a-house |access-date=14 February 2019 |agency=Euronews |publisher=euronews.com |date=13 February 2019}}</ref><ref name='A4'>{{cite news |last1=Stambaugh |first1=Alex |title=Polar bear invasion: Parents scared to send children to school in remote Russian archipelago |url=https://edition.cnn.com/2019/02/11/asia/polar-bears-russia-intl/index.html |access-date=15 February 2019 |agency=CNN |publisher=CNN |date=12 February 2019}}</ref>

=== Clathrate breakdown ===
{{Main|Clathrate gun hypothesis}}
{{annotated image/Extinction|float=right|caption=The Permian–Triassic extinction event (the [[Great Dying]]) may have been caused by release of [[methane]] from [[clathrate]]s. An estimated 52% of marine [[genus|genera]] became extinct, representing 96% of all marine [[species]].}}

[[Sea ice]], and the cold conditions it sustains, serves to stabilize [[methane]] deposits on and near the shoreline,<ref name="independent2008">{{cite web|url=https://www.independent.co.uk/environment/climate-change/exclusive-the-methane-time-bomb-938932.html |title=Exclusive: The methane time bomb |author=Connor, Steve |date=23 September 2008 |access-date=14 May 2009 |work=The Independent |archive-url=https://web.archive.org/web/20090403201120/http://www.independent.co.uk/environment/climate-change/exclusive-the-methane-time-bomb-938932.html |archive-date=3 April 2009 |url-status=live }}</ref> 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 genera and species to become extinct.<ref name="independent2008" /><ref>{{cite news|url=http://www.spiegel.de/international/world/0,1518,547976,00.html |title=A Storehouse of Greenhouse Gases Is Opening in Siberia |author=Mrasek, Volker |newspaper=Spiegel Online |date=17 April 2008 |access-date=14 May 2009 |archive-url=https://web.archive.org/web/20090501174420/http://www.spiegel.de/international/world/0%2C1518%2C547976%2C00.html |archive-date=1 May 2009 |url-status=live }}</ref>

=== Other concerns ===
Other [[Environmentalism|environmental concerns]] relate to the [[radioactive contamination]] of the Arctic Ocean from, for example, Russian [[radioactive waste]] dump sites in the Kara Sea,<ref>[http://bellona.org/english_import_area/international/russia/nuke_industry/siberia/mayak/21636 400 million cubic meters of radioactive waste threaten the Arctic area] {{webarchive |url=https://web.archive.org/web/20071016195202/http://bellona.org/english_import_area/international/russia/nuke_industry/siberia/mayak/21636 |date=16 October 2007 }} [[Thomas Nilsen]], Bellona, 24 August 2001. Retrieved 7 December 2006.</ref> [[Cold War]] [[Nuclear weapons testing|nuclear test sites]] such as Novaya Zemlya,<ref>[http://www.gso.uri.edu/maritimes/Text_Only/00Summer/text/arctic.html Plutonium in the Russian Arctic, or How We Learned to Love the Bomb] {{Webarchive|url=https://web.archive.org/web/20170202051233/http://www.gso.uri.edu/maritimes/Text_Only/00Summer/text/arctic.html |date=2 February 2017 }} Bradley Moran, John N. Smith. Retrieved 7 December 2006.</ref> [[Camp Century]]'s contaminants in Greenland,<ref>{{cite news |title=A Top-Secret US Military Base Will Melt Out of the Greenland Ice Sheet |url=https://www.vice.com/en/article/cold-war-era-nuclear-base-camp-century-melting-climate-change-greenland/ |work=VICE Magazine |date=9 March 2019}}</ref> and radioactive contamination from the [[Fukushima Daiichi nuclear disaster]].<ref>{{cite news |title=Radioactive contamination from Fukushima found as far north as Alaska's Bering Strait |url=https://www.straitstimes.com/world/radioactive-contamination-from-fukushima-found-as-far-north-as-alaskas-bering-strait |work=The Straits Times |date=28 March 2019}}</ref>

On 16 July 2015, five nations (United States, Russia, Canada, Norway, Denmark/Greenland) signed a declaration committing to keep their fishing vessels out of a 1.1&nbsp;million square mile zone in the central Arctic 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.<ref>{{cite news|title=Arctic deal bans North Pole fishing|url=https://www.bbc.com/news/world-europe-33549606|access-date=16 July 2015|work=BBC News|date=16 July 2015}}</ref><ref>{{cite news|last1=Rosen|first1=Yereth|title=5 nations sign declaration to protect Arctic 'donut hole' from unregulated fishing|url=https://www.adn.com/article/20150716/5-nations-sign-declaration-protect-arctic-donut-hole-unregulated-fishing|access-date=16 July 2015|publisher=Alaska Dispatch News|date=16 July 2015}}</ref>

== See also ==
{{Portal|Oceans|Geography|Water}}
{{Div col|colwidth=22em}}
* [[Arctic Bridge]]
* [[Arctic cooperation and politics]]
* [[Extreme points of the Arctic]]
* [[International Arctic Science Committee]]
* [[List of rivers of the Americas by coastline]]
* [[Nordicity]]
* [[Seven Seas]]
* [[Subarctic]]

{{div col end}}

== References ==
{{Reflist}}

== Further reading ==
* Neatby, Leslie H., ''Discovery in Russian and Siberian Waters'' (1973), {{ISBN|0-8214-0124-6}}.
* Ray, L., and B. Bacon, eds., ''The Arctic Ocean'' (1982), {{ISBN|0-333-31017-9}}.
* Thorén, Ragnar V.A., ''Picture Atlas of the Arctic'' (1969), {{ISBN|0-8214-0124-6}}.

== External links ==
{{Commons category|Arctic Ocean}}
{{Wiktionary}}
{{Wikisource|CIA World Fact Book, 2004/Arctic Ocean}}
{{GeoGroup}}

* [http://www.arctic-council.org/ Arctic Council]
* [https://web.archive.org/web/20050616080806/http://vitalgraphics.grida.no/arcticmap/ Arctic Environmental Atlas] Interactive map
* [https://arcticgreatrivers.org/ Arctic Great Rivers Observatory (ArcticGRO)]
* [https://www.cia.gov/the-world-factbook/oceans/arctic-ocean/ Arctic Ocean]. ''[[The World Factbook]]''. [[Central Intelligence Agency]].
* [http://nsidc.org/data/nsidc-0060.html Daily Arctic Ocean Rawinsonde Data from Soviet Drifting Ice Stations (1954–1990)] {{Webarchive|url=https://web.archive.org/web/20140119003406/http://nsidc.org/data/nsidc-0060.html |date=19 January 2014 }} at NSIDC
* [https://www.pmel.noaa.gov/arctic-zone/gallery_np.html NOAA North Pole Web Cam] Images from Web Cams deployed in spring on an ice floe
* [https://www.pmel.noaa.gov/arctic-zone/gallery_np_weatherdata.html NOAA Near-realtime North Pole Weather Data] Data from instruments deployed on an ice floe
* [http://www.polarfoundation.org/ International Polar Foundation]
* {{cite web |url=http://nsidc.org/arcticseaicenews/ |title=Daily report of Arctic ice cover based on satellite data |author=<!--Staff writer(s); no by-line.-->|website=nsidc.org |publisher=[[National Snow and Ice Data Center]] }}

{{Arctic topics}}
{{Polar exploration|state=collapsed}}
{{Regions of the world}}

{{Authority control}}

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[[Category:Geography of Northeast Asia]]
[[Category:Geography of Europe]]
[[Category:Geography of North America]]
[[Category:Bodies of water of Alaska]]
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[[Category:Bodies of water of Greenland]]
[[Category:Bodies of water of Norway]]
[[Category:Bodies of water of Iceland]]
[[Category:Bodies of water of Russia]]