The Norwegian Sea is a marginal sea, grouped with either the Atlantic Ocean or the Arctic Ocean, northwest of Norway between the North Sea and the Greenland Sea, adjoining the Barents Sea to the northeast. In the southwest, it is separated from the Atlantic Ocean by a submarine ridge running between Iceland and the Faroe Islands. To the north, the Jan Mayen Ridge separates it from the Greenland Sea.

Unlike many other seas, most of the bottom of the Norwegian Sea is not part of a continental shelf and therefore lies at a great depth of about on average. Rich deposits of oil and natural gas are found under the sea bottom and are being explored commercially, in the areas with sea depths of up to about . The coastal zones are rich in fish that visit the Norwegian Sea from the North Atlantic or Barents Sea (cod) for spawning. The warm North Atlantic Current ensures relatively stable and high water temperatures, so that unlike the Arctic seas, the Norwegian Sea is ice-free throughout the year. Recent research has concluded that the large volume of water in the Norwegian Sea with its large heat absorption capacity is more important as a source of Norway's mild winters than the Gulf Stream and its extensions.

Extent

The International Hydrographic Organization defines the limits of the Norwegian Sea as follows:

::On the Northeast. A line joining the southernmost point of West Spitzbergen to North Cape of Bjørnøya (Bear Island), through this island to Cape Bull and thence on to North Cape, Norway (25°45'E).

::On the Southeast. The West coast of Norway between North Cape and Cape Stadt ().

::On the South. From a point on the West coast of Norway in Latitude 61°00' North along this parallel to Longitude 0°53' West thence a line to the NE extreme of Fuglö () and on to the East extreme of Gerpir () in Iceland.

::On the West. The Southeastern limit of Greenland Sea [A line joining the southernmost point of West Spitzbergen to the Northern point of Jan Mayen Island, down the West coast of that island to its Southern extreme, thence a Line to the Eastern extreme of Gerpir () in Iceland].

Formation and geography

thumb|Norwegian Sea, surrounded by shallower seas to the south (North Sea) and northeast (Barents Sea). The white dot near the centre is Jan Mayen, and the dot between Spitsbergen (large island to the north) and Norway is [[Bear Island (Norway)|Bear Island.]]

thumb|left|Vedøya, Skumvær and Røst islands, [[Lofoten, Norway]]

The Norwegian Sea was formed about 250 million years ago, when the Eurasian Plate of Norway and the North American Plate, including Greenland, started to move apart. The existing narrow shelf sea between Norway and Greenland began to widen and deepen. The present continental slope in the Norwegian Sea marks the border between Norway and Greenland as it stood approximately 250 million years ago. In the north it extends east from Svalbard and on the southwest between Britain and the Faroes. This continental slope contains rich fishing grounds and numerous coral reefs. Settling of the shelf after the separation of the continents has resulted in landslides, such as the Storegga Slide about 8,000 years ago that induced a major tsunami. The flow shows strong seasonal variations and can be twice as high in winter as in summer. The temperature and salinity of this current show strong seasonal and annual fluctuations. Long-term measurements within the top near the coast show a maximum temperature of at the 63° N parallel in September and a minimum of at the North Cape in March. The salinity varies between 34.3 and 34.6‰ and is lowest in spring owing to the inflow of melted snow from rivers. Other surface water (~1 Sv) flows along the Norwegian coast in the direction of the Barents Sea. This water may cool enough in the Norwegian Sea to submerge into the deeper layers; there it displaces water that flows back into the North Atlantic.

Arctic water from the East Iceland Current is mostly found in the southwestern part of the sea, near Greenland. Its properties also show significant annual fluctuations, with long-term average temperature being below and salinity between 34.7 and 34.9‰.

Deep-sea currents

The Norwegian Sea is connected with the Greenland Sea and the Arctic Ocean by the deep Fram Strait. The Norwegian Sea Deep Water (NSDW) occurs at depths exceeding ; this homogeneous layer with a salinity of 34.91‰ experiences little exchange with the adjacent seas. Its temperature is below and drops to at the ocean floor.

The weak deep-water exchange with the Atlantic Ocean is due to the small depth of the relatively flat Greenland-Scotland Ridge between Scotland and Greenland, an offshoot of the Mid-Atlantic Ridge. Only four areas of the Greenland-Scotland Ridge are deeper than : the Faroe-Bank Channel (about ), some parts of the Iceland-Faroe Ridge (about ), the Wyville-Thomson Ridge (), and areas between Greenland and the Denmark Strait () – this is much shallower than the Norwegian Sea. The turbulence that occurs when the deep water falls behind the Greenland-Scotland Ridge into the deep Atlantic basin mixes the adjacent water layers and forms the North Atlantic Deep Water, one of two major deep-sea currents providing the deep ocean with oxygen.

Climate

The thermohaline circulation affects the climate in the Norwegian Sea, and the regional climate can significantly deviate from average. There is also a difference of about between the sea and the coastline. Temperatures rose between 1920 and 1960, and the frequency of storms decreased in this period. The storminess was relatively high between 1880 and 1910, decreased significantly between 1910 and 1960, and then recovered to the original level.

In contrast to the Greenland Sea and Arctic seas, the Norwegian Sea is ice-free year round, owing to its warm currents. The July isotherm (air temperature line) runs through the northern boundary of the Norwegian Sea and is often taken as the southern boundary of the Arctic. In winter, the Norwegian Sea generally has the lowest air pressure in the entire Arctic and where most Icelandic Low depressions form. The water temperature in most parts of the sea is in February and in August. The southern limit of many Arctic species runs through the North Cape, Iceland, and the center of the Norwegian Sea, while the northern limit of boreal species lies near the borders of the Greenland Sea with the Norwegian Sea and Barents Sea; that is, these areas overlap. Some species like the scallop Chlamys islandica and capelin tend to occupy this area between the Atlantic and Arctic oceans.

Plankton and sea bottom organisms

Most of the aquatic life in the Norwegian Sea is concentrated in the upper layers. Estimates for the entire North Atlantic are that only 2% of biomass is produced at depths below and only 1.2% occurs near the sea floor.

The blooming of the phytoplankton is dominated by chlorophyll and peaks around 20 May. The major phytoplankton forms are diatoms, in particular the genus Thalassiosira and Chaetoceros. After the spring bloom the haptophytes of the genus Phaecocystis pouchetti become dominant.

<gallery class="center" widths="160px" heights="130px">

File:Hyperia.jpg|Hyperiidea

File:Pandborealisind.jpg|Shrimp Pandalus borealis

File:Lophelia pertusa.jpg|Lophelia pertusa

File:Meganyctiphanes norvegica.jpg|Meganyctiphanes norvegica

</gallery>

Zooplankton is mostly represented by the copepods Calanus finmarchicus and Calanus hyperboreus, where the former occurs about four times more often than the latter and is mostly found in the Atlantic streams, whereas C. hyperboreus dominates the Arctic waters; The herring stock varies greatly between years. It increased in the 1920s owing to the milder climate and then collapsed in the following decades until 1970; the decrease was, however, at least partly caused by overfishing.

thumb|[[Capelin is a common fish of the Atlantic-arctic transitional waters]]

Enforcement of environmental and fishing regulations has resulted in partial recovery of the herring populations since 1987. Meanwhile, the elderly capelin population was quickly fished out. This also reduced the population of cod – a major predator of capelin – as the herring was still too small in numbers to replace the capelin in the cod's diet.

thumb|Blue whiting

Blue whiting (Micromesistius poutassou) has benefited from the decline of the herring and capelin stocks as it assumed the role of major predator of plankton. The blue whiting spawns near the British Isles. The sea currents carry their eggs to the Norwegian Sea, and the adults also swim there to benefit from the food supply. The young spend the summer and the winter until February in Norwegian coastal waters and then return to the warmer waters west of Scotland. and white-beaked dolphins occur in the coastal waters. Orcas and some other whales visit the sea in the summer months for feeding; their population is closely related to the herring stocks, and they follow the herring schools within the sea.

The bowhead whale used to be a major plankton predator, but it almost disappeared from the Norwegian Sea after intense whaling in the 19th century, Observations of northern bottlenose whales in the Norwegian Sea are rare. Other large animals of the sea are hooded and harp seals and squid.

Human activities

Norway, Iceland, and Denmark/Faroe Islands share the territorial waters of the Norwegian Sea, with the largest part belonging to the first. Norway has claimed twelve-mile limit as territorial waters since 2004 and an exclusive economic zone of since 1976. Consequently, due to the Norwegian islands of Svalbard and Jan Mayen, the southeast, northeast and northwest edge of the sea fall within Norway. The southwest border is shared between Iceland and Denmark/Faroe Islands.

The largest damage to the Norwegian Sea was caused by extensive fishing, whaling, and pollution. Other contamination is mostly by oil and toxic substances, but also from the great number of ships sunk during the two world wars. The environmental protection of the Norwegian Sea is mainly regulated by the OSPAR Convention.

Over the last century, the Norwegian Sea has been suffering from overfishing. In 2018, 41% of stocks were excessively harvested. Two out of sixteen of the Total Allowed Catches (TACs) agreed upon by the European Union (EU) and Norway follow scientific advice. Nine of those TACs are at least 25% above scientific advice. While the other five are set above scientific evidence when excluding landing obligation. Under the Common Fisheries Policy (CFP), the EU committed to phase out overfishing by 2015, 2020 at the absolute latest. As of 2019, the EU was reported to not be on path to achieving that goal.

Whaling was also important for the Norwegian Sea. In the early 1600s, the Englishman Stephen Bennet started hunting walrus at Bear Island. In May 1607 the Muscovy Company, while looking for the Northwest Passage and exploring the sea, discovered the large populations of walrus and whales in the Norwegian Sea and started hunting them in 1610 near Spitsbergen. Later in the 17th century, Dutch ships started hunting bowhead whales near Jan Mayen; the bowhead population between Svalbard and Jan Mayen was then about 25,000 individuals. Britons and Dutch were then joined by Germans, Danes, and Norwegians. Many legends might be based on the work Historia de gentibus septentrionalibus of 1539 by Olaus Magnus, which described the kraken and maelstroms of the Norwegian Sea. The kraken also appears in Alfred Tennyson's poem of the same name, in Herman Melville's Moby Dick, and in Twenty Thousand Leagues Under the Seas by Jules Verne.

Between the Lofoten islands of Moskenesøya and Værøya, at the tiny Mosken island, lies the Moskenstraumen – a system of tidal eddies and a whirlpool called a maelstrom. With a speed on the order of (the value strongly varies between sources), it is one of the strongest maelstroms in the world. It was described in the 13th century in the Old Norse Poetic Edda and remained an attractive subject for painters and writers, including Edgar Allan Poe, Walter Moers, and Jules Verne. The word was introduced into the English language by Poe in his story "A Descent into the Maelström" (1841) describing the Moskenstraumen. The Moskenstraumen is created as a result of a combination of several factors, including the tides, the position of the Lofoten, and the underwater topography; unlike most other whirlpools, it is located in the open sea rather than in a channel or bay. With a diameter of , it can be dangerous even in modern times to small fishing vessels that might be attracted by the abundant cod feeding on the microorganisms sucked in by the whirlpool.

Exploration

thumb|In the late 19th century, [[Henrik Mohn developed the first dynamic flow model of the North Atlantic. This map of 1904 shows surface and underwater currents.]]

The fish-rich coastal waters of northern Norway have long been known and attracted skilled sailors from Iceland and Greenland. Thus most settlements in Iceland and Greenland were on the west coasts of the islands, which were also warmer due to the Atlantic currents. The first reasonably reliable map of northern Europe, the Carta marina of 1539, represents the Norwegian Sea as coastal waters and shows nothing north of the North Cape. The Norwegian Sea off the coast regions appeared on the maps in the 17th century as an important part of the then sought Northern Sea Route and a rich whaling ground.

Jan Mayen island was discovered in 1607 and become an important base of Dutch whalers. The Dutchman Willem Barents discovered Bear Island and Svalbard, Systematic oceanographic research in the Norwegian Sea started in the late 19th century, when declines in the yields of cod and herring off the Lofoten prompted the Norwegian government to investigate the matter. The zoologist Georg Ossian Sars and meteorologist Henrik Mohn persuaded the government in 1874 to send out a scientific expedition, and between 1876 and 1878 they explored much of the sea aboard Vøringen. The data obtained allowed Mohn to establish the first dynamic model of ocean currents, which incorporated winds, pressure differences, sea water temperature, and salinity and agreed well with later measurements. In 2019, deposits of iron, copper, zink and cobalt were found on the Mohn Ridge, likely from hydrothermal vents.

thumb| during the winter convoy through the Norwegian Sea to Russia in 1941

thumb|The Soviet nuclear submarine [[Soviet submarine K-278 Komsomolets|K-278 Komsomolets in&nbsp;1986.]]

Until the 20th century, the coasts of the Norwegian Sea were sparsely populated and therefore shipping in the sea was mostly focused on fishing, whaling, and occasional coastal transportation. Since the late 19th century, the Norwegian Coastal Express sea line has been established, connecting the more densely populated south with the north of Norway by at least one trip a day. The importance of shipping in the Norwegian Sea also increased with the expansion of the Russian and Soviet navies in the Barents Sea and development of international routes to the Atlantic through the Baltic Sea, Kattegat, Skagerrak, and North Sea.

The Norwegian Sea is ice-free and provides a direct route from the Atlantic to the Russian ports in the Arctic (Murmansk, Arkhangelsk, and Kandalaksha), which are directly linked to central Russia. This route was extensively used for supplies during World War II – of 811 U.S. ships, 720 reached Russian ports, bringing some of cargo that included about 5,000 tanks and 7,000 aircraft. The Allies lost 18 convoys and 89 merchant ships on this route. The major operations of the Kriegsmarine (German Navy) against the convoys included PQ 17 in July 1942, the Battle of the Barents Sea in December 1942, and the Battle of the North Cape in December 1943 and were carried out around the border between the Norwegian Sea and Barents Sea, near the North Cape. The countermeasures by the North Atlantic Treay Organization (NATO) countries resulted in a significant naval presence in the Norwegian Sea and intense cat-and-mouse games between Soviet and NATO aircraft, ships, and especially submarines. A relic of the Cold War in the Norwegian Sea, the Soviet nuclear submarine K-278 Komsomolets, sank in 1989 southwest of Bear Island, at the border of the Norwegian and Barents seas, with radioactive material onboard that poses potential danger to flora and fauna.

The Norwegian Sea is part of the Northern Sea Route for ships making voyages between European ports and Asia. The travel distance from Rotterdam to Tokyo is via the Suez Canal but only through the Norwegian Sea. Sea ice is a common problem in the Arctic seas, but ice-free conditions along the entire northern route were observed at the end of August 2008. Russia is planning to expand its offshore oil production in the Arctic, which should increase the traffic of tankers through the Norwegian Sea to markets in Europe and North America; it is expected that the number of oil shipments through the northern Norwegian Sea will increase from 166 in 2002 to 615 in 2015.

thumb|Map of the [[Langeled pipeline]]

Oil and gas

The most important products of the Norwegian Sea are no longer fish, but oil and especially gas found under the ocean floor. Norway started undersea oil production in 1993, followed by development of the Huldra gas field in 2001. The large depth and harsh waters of the Norwegian Sea pose significant technical challenges for offshore drilling. Several other gas fields are being developed. As of 2019, there was an estimated of crude oil in the Norwegian Sea, with an expectation to increase oil production in the region up until 2025. A particular challenge is the Kristin field, where the temperature is as high as and the gas pressure exceeds 900 bar (900 times the normal pressure). Further north are Norne and Snøhvit.

In the fishing simulation game Russian Fishing 4, the Norwegian Sea is a popular map, especially for recreational boat fishing.

See also

  • List of seas

References

Bibliography