The Norwegian Sea is a marginal sea in the North Atlantic Ocean, northwest of Norway. It is located between the North Sea (i.e. north of Scotland) and the Greenland Sea and adjoins the North Atlantic Ocean to the west and 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 two kilometres 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 one kilometre. The coastal zones are rich in fish that visit the Norwegian Sea from the North Atlantic 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.
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 10 °C 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 in 1910–1960, 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 convection between the relatively warm water and cold air in the winter plays an important role in the Arctic climate. The 10-degree 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 2–7 °C in February and 8–12 °C in August.
Flora and fauna :
The Norwegian Sea is a transition zone between boreal and Arctic conditions, and thus contains flora and fauna characteristic of both climatic regions. 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 1,000 metres 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.
The Norwegian coastal waters are the most important spawning ground of the herring populations of the North Atlantic, and the hatching occurs in March. The eggs float to the surface and are washed off the coast by the northward current. Whereas a small herring population remains in the fjords and along the northern Norwegian coast, the majority spends the summer in the Barents Sea, where it feeds on the rich plankton. Upon reaching puberty, herring returns to the Norwegian Sea.
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. The biomass of young hatched herring declined from 11 million tonnes in 1956 to almost zero in 1970; that affected the ecosystem not only of the Norwegian Sea but also of the Barents Sea.
Enforcement of environmental and fishing regulations has resulted in partial recovery of the herring populations since 1987. This recovery was accompanied by a decline of capelin and cod stocks. While the capelin benefited from the reduced fishing, the temperature rise in the 1980s and competition for food with the herring resulted in a near disappearance of young capelin from the Norwegian Sea. 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.
Mammals and birds :
Significant numbers of minke, humpback, sei, and orca whales are present in the Norwegian Sea, 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. With a total population of about 110,000, minke whales are by far the most common whales in the sea. They are hunted by Norway and Iceland, with a quota of about 1,000 per year in Norway. In contrast to the past, nowadays primarily their meat is consumed, rather than fat and oil.
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, and was temporarily extinct in the entire North Atlantic. Similarly, the blue whale used to form large groups between Jan Mayen and Spitsbergen, but is hardly present nowadays. 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 200 miles 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. The British nuclear complex of Sellafield is one of the greatest polluters, discharging radioactive waste into the sea. 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.
Fishing and whaling :
Fishing has been practised near the Lofoten archipelago for hundreds of years. The coastal waters of the remote Lofoten islands are one of the richest fishing areas in Europe, as most of the Atlantic cod swims to the coastal waters of Lofoten in the winter to spawn. So in the 19th century, dried cod was one of Norway's main exports and by far the most important industry in northern Norway. Strong sea currents, maelstroms, and especially frequent storms made fishing a dangerous occupation: several hundred men died on the "Fatal Monday" in March 1821, 300 of them from a single parish, and about a hundred boats with their crews were lost within a short time in April 1875.