Arctic Ocean

Earth's oceans
Arctic Ocean Atlantic Ocean Indian Ocean Pacific Ocean Southern Ocean

The Arctic Ocean, with borders as delineated by the International Hydrographic Organization (IHO), including Hudson Bay (some of which is south of 57°N latitude, off the map) and all other marginal seas.

The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately 14,060,000 km² (5,430,000 sq mi) and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers call it the Arctic Mediterranean Sea. It is also the northernmost part of the all-encompassing World Ocean.

The Arctic Ocean lies entirely within the Arctic Circle and includes the North Pole region. Extending south to about 60°N, the ocean is surrounded by Eurasia and North America. Its borders follow topographic features: the Bering Strait on the 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. Climate change has resulted in a decline in sea ice extent, with considerable impacts both local and global.

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.

History

Thule archaeological site

During the Wisconsin glaciation, at least 17,000–50,000 years ago, falling sea levels allowed people to move across the Arctic Ocean by means of the Bering land bridge that joined Siberia to northwestern North America (Alaska).

For much of European history, the north polar regions remained largely unexplored and their geography conjectural. Pytheas of Massilia recorded an account of a journey northward in 325 B.C.E., to a land he called "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 "growlers" or "bergy bits"; his "Thule" was probably Norway, though the Faroe Islands or Shetland have also been suggested.

Emanuel Bowen's 1780s map of the Arctic features a "Northern Ocean".

Early 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 (eleventh century) and 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.

The Arctic region showing the Northeast Passage, the Northern Sea Route within it, and the Northwest Passage.

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, 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. Nevertheless, as all the explorers who traveled 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 nautical crossing of the Arctic Ocean, in 1896.

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

The first undisputed surface crossing of the ocean to the North Pole in 1969, on the 60th anniversary of Robert Peary’s famous, but disputed, expedition, was by British explorer Sir Walter William “Wally” Herbert in a dog sled expedition from Alaska to Svalbard, with air support. The first nautical transit to 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.

Geography

A bathymetric/topographic map of the Arctic Ocean and the surrounding lands.

The 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.

Size

The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It 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, with a coastline 45,390 km (28,200 mi) long. It is the only ocean smaller than Russia, which has a land area of 16,377,742 km² (6,323,482 sq mi).

Surrounding land

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.

Subareas and connections

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. (The Iceland Sea is sometimes considered part of the Greenland Sea, and sometimes separate.)

Different authorities put various marginal seas in either the Arctic Ocean or the Atlantic Ocean, including: Hudson Bay, Baffin Bay, the Norwegian Sea, and Hudson Strait.

Islands

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))

Ports

There are several ports and harbors on the Arctic Ocean.

• Alaska
  • Utqiaġvik (Barrow)
  • Prudhoe Bay
• Canada
  • Manitoba: Churchill (Port of Churchill)
  • Nunavut: Nanisivik (Nanisivik Naval Facility)
  • Tuktoyaktuk and Inuvik in the Northwest Territories
• Greenland: Nuuk (Nuuk Port and Harbour)
• Norway
  • Mainland: Kirkenes and Vardø
  • Svalbard: Longyearbyen
• Iceland
  • Akureyri
• Russia
  • Barents Sea: Murmansk in the Barents Sea
  • White Sea: Arkhangelsk
  • Kara Sea: Labytnangi, Salekhard, Dudinka, Igarka and Dikson
  • Laptev Sea: Tiksi in the
  • East Siberian Sea: Pevek in the East Siberian Sea

Arctic shelves

The ocean's Arctic shelf comprises a number of continental shelves, including the Canadian Arctic shelf, underlying the Canadian Arctic Archipelago, and the 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.

The Chukchi Plateau extends from the Chukchi Sea Shelf.

Underwater features

An underwater ridge, the Lomonosov Ridge, divides the deep sea North Polar Basin into two oceanic basins: the Eurasian Basin, which is 4,000–4,500 m (13,100–14,800 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 Ocean is 1,038 m (3,410 ft), and the deepest point is Molloy Hole in the Fram Strait, at about 5,550 m (18,200 ft).

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 ridges), and Nansen Basin (between the Gakkel Ridge and the continental shelf that includes the Franz Josef Land).

Geology

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 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.

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 billion barrels of oil. The Gakkel Ridge rift is also poorly understand and may extend into the Laptev Sea.

Oceanography

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.

Water flow

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 stratification is stable, deeper water masses are denser than the layers above.

Density structure of the upper 1,200 m (3,900 ft) 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 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 rivers (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 rise with increasing depth.

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." The Arctic Ocean has a total volume of 18.07 × 10⁶ km³, 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.

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 900 m (3,000 ft) depth. 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 Sverdrups and reaches the 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 Ocean and create a halocline.

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. 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 m (490–3,000 ft) 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, equaling about 10 times that of the Pacific inflow, and it creates the Arctic Ocean Boundary Current. It flows slowly, at about 0.02 m/s. Atlantic Water has the same salinity as Arctic Bottom Water but is much warmer (up to 3 °C [37 °F]). 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 Gyre is far less saline than that of the Chukchi Sea due to inflow from large Canadian and Siberian rivers.

The final defined water mass in the Arctic Ocean is called Arctic Surface Water and is found in the depth range of 150–200 m (490–660 ft). 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 on account of weak mixing between layers.

Waters originating in the Pacific and Atlantic both exit through the Fram Strait between Greenland and Svalbard Island, which is about 2,700 m (8,900 ft) deep and 350 km (220 mi) wide. This outflow is about 9 Sv. 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. Pacific water also exits along the west coast of Greenland and the Hudson Strait (1–2 Sv), providing nutrients to the Canadian Archipelago.

Sea ice

Sea cover in the Arctic Ocean, showing the median, 2005 and 2007 coverage

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 summer shrinking of the ice has been quoted at 50 percent. 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 pose a hazard to ships, of which the Titanic is one of the most famous. Icebergs are not sea ice but may become embedded in the pack ice. 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 risked being trapped or crushed by sea ice.

Climate

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. Summers are characterized by continuous daylight (midnight sun), and air temperatures can rise slightly above 0 °C (32 °F). It is cloudy year-round, with mean cloud cover ranging from 60 percent in winter to over 80 percent in summer.

The temperature of the surface water of the Arctic Ocean is fairly constant at approximately −1.8 °C (29 °F), near the freezing point of seawater. 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 Antarctic continent.

Biology

Three polar bears approach USS Honolulu near the North Pole.

Due to the pronounced seasonality of 2–6 months of midnight sun and polar night 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). Important consumers of primary producers in the central Arctic Ocean and the adjacent shelf seas include zooplankton, especially copepods (Calanus finmarchicus, Calanus glacialis, and Calanus hyperboreus) and euphausiids, as well as ice-associated fauna, such as amphipods. These primary consumers form an important link between the primary producers and higher trophic levels. 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 consumers in the Barents Sea, an Atlantic-influenced Arctic shelf sea, are mainly sub-Arctic species including herring, young cod, and capelin. In ice-covered regions of the central Arctic Ocean, polar cod is a central predator of primary consumers. The apex predators in the Arctic Ocean—marine mammals such as seals, whales, and polar bears—prey upon fish.

Endangered marine species in the Arctic Ocean include walruses and whales. 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.

Minke whale

Walruses on Arctic ice floe

Natural resources

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 center of the sea is significant for the global energy market because it may hold 25 percent or more of the world's undiscovered oil and gas resources.

Environmental concerns

Arctic ice melting

The mean extent of the Arctic sea ice has been continuously decreasing in the last decades, declining at a rate of currently 12.6 percent per decade since 1980 from the average winter value of 15,600,000 km² (6,023,200 sq mi).

Warming temperatures in the Arctic may cause large amounts of fresh melt-water to enter the north Atlantic, possibly disrupting global ocean current patterns.

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. Beginning in December 2018 and coming to an apex in February 2019, 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.

Clathrate breakdown

Sea ice, and the cold conditions it sustains, serves to stabilize methane deposits on and near the shoreline, preventing the clathrate breaking down and outgassing methane into the atmosphere. 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.

Other concerns

On July 16, 2015, five nations (United States, 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 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.

Other environmental concerns relate to the radioactive contamination of the Arctic Ocean from, for example, radioactive waste dump sites and Cold War nuclear test sites.

References

ISBN links support NWE through referral fees

• Affholder, M., and F. Valiron. Descriptive Physical Oceanography. CRC Press, 2001. ISBN 978-9054107064
• Maury, Matthew Fontaine. The Physical Geography of the Sea. Palala Press, 2015 (original 1883)., ISBN 978-1340857622
• Piskarev, Alexey, Victor Poselov, and Valery Kaminsky (eds.). Geologic Structures of the Arctic Basin. Springer, 2018. ISBN 3030085260
• Rudels, Bert. The Physical Oceanography of the Arctic Mediterranean Sea. Elsevier, 2021. ISBN 978-0128169308
• Serreze, Mark C., and Roger G. Barry. The Arctic Climate System. Cambridge University Press, 2014. ISBN 978-1107037175
• Talley, Lynne D., George L. Pickard, William J. Emery, and James H. Swift. Descriptive Physical Oceanography: An Introduction. Academic Press, 2011. ASIN B0058N4M62
• Tomczak, Matthias, and J. Stuart Godfrey. Regional Oceanography: An Introduction. Daya Publishing House, 2004. ISBN 978-8170353065
• Wright,John W. (ed.). The New York Times Almanac 2007. Penguin Books, 2006. ISBN 978-0143038207

External links

All links retrieved August 12, 2023.

• Arctic Council
• Arctic Great Rivers Observatory (ArcticGRO)
• Arctic Ocean The World Factbook
• North Pole Web Cam NOAA
• North Pole Weather Data and Instrumentation NOAA
• Arctic Sea Ice News & Analysis National Snow & Ice Data Center

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