Norwegian Sea

• 1. Introduction

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  The Norwegian Sea sits northwest of Norway in a geographic limbo, claimed by neither the Atlantic nor the Arctic Ocean but counted as part of both. Below its surface, two deep basins plunge to depths of 3,500-4,000 metres in the south and 3,200-3,300 metres in the north. A cold nuclear submarine named K-278 Komsomolets rests on that floor, southwest of Bear Island, radioactive material still onboard. What kind of sea produces this layering of the geological, the biological, and the geopolitical? It formed roughly 250 million years ago when two continents began pulling apart. Its waters shape Norway's winters more than the Gulf Stream does. Its herring once fed empires and nearly vanished by 1970. And its floor now holds some of Europe's most important gas reserves. This is the Norwegian Sea.

• 2. A Sea Born From Separation

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  About 250 million years ago, the Eurasian Plate and the North American Plate, which then included Greenland, began moving apart. The narrow shelf sea between Norway and Greenland widened and deepened into what is now the Norwegian Sea. The present continental slope marks the ancient boundary where the two landmasses once met.

  The last ice age left its own mark. Glaciers several kilometres high carved fjords into the Norwegian coast and pushed crustal material into the sea, extending the continental slopes. This effect is especially visible along the coast from Helgeland north to the Lofoten Islands.

  The Norwegian continental shelf that resulted is between 40 and 200 kilometres wide. It is irregular in a distinctive way, filled with trenches and peaks that typically vary by less than 100 metres in height but can rise to 400 metres. Fish use those trenches as spawning grounds. The shelf's continental slope, which also marks the historical boundary between Norway and Greenland, hosts rich fishing grounds and extensive coral reefs.

  A major geological event from a more recent era adds a dramatic footnote. About 8,000 years ago, a landslide known as the Storegga Slide occurred as the shelf settled after the original continental separation, triggering a major tsunami.

• 3. Water in Motion

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  Four major water masses from the Atlantic and Arctic oceans converge in the Norwegian Sea, and the currents they generate are considered fundamental to global climate. The warm, salty North Atlantic Current flows in from the Atlantic; the Norwegian Current originates in the North Sea, tracing drainage from across northern Europe through the Baltic. The East Iceland Current carries cold water southward from the Norwegian Sea toward Iceland, moving through the sea's middle water layer. And deep water arrives from the Greenland Sea.

  The tides in the Norwegian Sea are semi-diurnal, meaning they rise twice each day, reaching heights of about 3.3 metres.

  The North Atlantic Current's flow reaches a speed of 10 Sv (one Sv equals one million cubic metres per second) and penetrates to a maximum depth of 700 metres at the Lofoten Islands. At the Faroe-Shetland Channel it carries a salinity of 35.3 parts per thousand, elevated by the evaporation of the warm European climate over which it passes. By the time this current reaches Svalbard, it has cooled from about 9.5 degrees Celsius to about 5 degrees, releasing roughly 250 terawatts of energy to the surrounding environment.

  The Norwegian Current shows dramatic seasonal swings: the three largest rivers feeding it, the Namsen, Ranelva, and Vefsna, are steep and short, producing high discharge rates. That input means salinity dips to its lowest each spring, when snowmelt floods in from inland rivers.

  Deep below, Norwegian Sea Deep Water occupies depths greater than 2,000 metres with a measured salinity of 34.91 parts per thousand. Its temperature falls below zero Celsius and drops further at the ocean floor. It is relatively old water, rich in nutrients but low in oxygen. The exchange of this deep layer with the Atlantic is restricted by the Scotland-Greenland Ridge, which averages only 500 metres in depth. Cold deep water does escape through four passages, including the Faroe Bank Channel at about 850 metres deep and the Iceland-Faroe channel. When that cold water tumbles behind the ridge into the deep Atlantic basin, the turbulence mixes surrounding layers and produces the North Atlantic Deep Water, one of two deep-sea currents that supply the open ocean with oxygen.

• 4. Life From Top to Floor

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  Most living things in the Norwegian Sea concentrate in its upper layers. Estimates for the entire North Atlantic suggest only 2 percent of biomass is produced at depths below 1,000 metres, and only 1.2 percent occurs near the seafloor.

  Near the surface, the spring phytoplankton bloom peaks around the 20th of May, driven by diatoms of the genera Thalassiosira and Chaetoceros. After that bloom, haptophytes of the genus Phaecocystis pouchetti take dominance. Zooplankton is largely the copepod Calanus finmarchicus, which outnumbers its Arctic cousin Calanus hyperboreus by about four to one and is the main food of most marine predators. Production varies sharply by year: C. finmarchicus yield was 28 grams per square metre in 1995 but only 8 grams per square metre in 1997, a drop that rippled through the populations of every species that feeds on it.

  The Norwegian Sea's most ecologically distinctive feature may be its extensive coral reefs of Lophelia pertusa along the continental slopes. Although this coral appears across the peripheral North Atlantic, it reaches concentrations in the Norwegian Sea that have no parallel elsewhere. Those reefs shelter numerous fish species but face ongoing damage from trawling, which physically destroys them.

  Shrimp of the species Pandalus borealis, found mostly at depths between 200 and 300 metres, serve as a critical link: they are a primary food source for cod and blue whiting alike.

  Higher up the food chain, the Norwegian Sea holds a total minke whale population of about 110,000, making them by far the most numerous whales in these waters. Norway and Iceland together hunt them under a quota of about 1,000 per year in Norway alone. Orcas and other whale species arrive in summer to follow herring schools, their population closely tracking the abundance of that one fish.

• 5. The Herring Collapse

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  The Norwegian coastal waters are the most important spawning ground for herring across the entire North Atlantic. Hatching occurs in March, and the eggs drift to the surface before northward currents carry them offshore. The majority of the population then migrates to the Barents Sea for summer feeding.

  For centuries this cycle sustained fishing communities. Herring stocks grew through the 1920s as the climate briefly warmed, then steadily declined. The biomass of young herring fell from 11,000,000 tonnes in 1956 to nearly zero by 1970. Overfishing drove much of the collapse, though the stock's decline fed a cascade. Puffins on the Lofoten Islands, unable to switch to an alternative prey, had their population roughly halved between 1969 and 1987.

  When herring began recovering after 1987, a new imbalance appeared. Capelin and cod populations fell as a consequence. The temperature rise of the 1980s, combined with food competition from herring, caused young capelin to nearly vanish from the Norwegian Sea. Elderly capelin were fished out quickly. Cod, which depend heavily on capelin, declined too, since herring numbers were still too low to fill the gap in the cod's diet.

  Blue whiting, Micromesistius poutassou, filled the vacuum. Spawning near the British Isles and carried by currents to Norwegian waters, blue whiting assumed the role of primary plankton predator that had belonged to capelin.

  As of 2018-41 percent of stocks in the Norwegian Sea were excessively harvested. Of sixteen Total Allowed Catches agreed upon by the EU and Norway, only two follow scientific advice, and nine sit at least 25 percent above what scientists recommend. The EU committed under the Common Fisheries Policy to phase out overfishing by 2015 and absolutely no later than 2020; as of 2019, it was not on track to meet that goal.

• 6. Kraken, Maelstrom, and Myth

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  For many centuries European sailors treated the Norwegian Sea as the edge of the known world. Ships vanished there in storms and disasters, and those disappearances generated legends of creatures capable of dragging vessels under.

  As late as 1845, the Encyclopaedia metropolitana published a multi-page review by Erik Pontoppidan, who lived from 1698 to 1764, on sea monsters half a mile in size that sank ships. That tradition traces partly to the Historia de gentibus septentrionalibus, written by Olaus Magnus in 1539, which described both the kraken and the maelstroms of the Norwegian Sea. The kraken subsequently appeared in Alfred Tennyson's poem of the same name, in Herman Melville's Moby Dick, and in Jules Verne's Twenty Thousand Leagues Under the Seas.

  The physical phenomenon behind the most enduring maelstrom legends is real. Between the Lofoten islands of Moskenesoya and Vaeroya, near the small island of Mosken, lies the Moskenstraumen: a system of tidal eddies and a whirlpool reaching speeds on the order of 15 kilometres per hour. It was described in the 13th century in the Old Norse Poetic Edda. Unlike most whirlpools, the Moskenstraumen sits in open sea rather than in a channel or bay, the result of a combination of tidal forces, the positioning of the Lofoten Islands, and the underwater topography. It carries a diameter of 40 to 50 metres and remains a genuine hazard to small fishing boats, which are sometimes drawn in by the cod that feed on microorganisms sucked into the vortex.

  Edgar Allan Poe introduced the word maelstrom into English through his 1841 story "A Descent into the Maelstrom," which described the Moskenstraumen directly.

• 7. Whaling, War, and Oil

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  Systematic commercial exploitation of the Norwegian Sea began in earnest in the early 17th century. Stephen Bennet, an Englishman, started hunting walrus at Bear Island in the early 1600s. In May 1607 the Muscovy Company, searching for the Northwest Passage, discovered large populations of walrus and whales in the sea and began hunting near Spitsbergen by 1610. Dutch ships soon joined, targeting bowhead whales near Jan Mayen, where the bowhead population then numbered about 25,000 individuals. Germans, Danes, and Norwegians followed. Between 1615 and 1820, the waters between Jan Mayen, Svalbard, Bear Island, and Greenland constituted the most productive whaling area in the world. Extensive hunting had wiped out the whales in that region by the early 20th century.

  During World War II the Norwegian Sea became a strategic artery. Of 811 U.S. ships dispatched to Russian Arctic ports, 720 arrived, delivering roughly 4,000,000 tonnes of cargo including about 5,000 tanks and 7,000 aircraft. The Allies lost 89 merchant ships on the route. German naval operations against those convoys included the attack on convoy PQ 17 in July 1942, the Battle of the Barents Sea in December 1942, and the Battle of the North Cape in December 1943, all fought near the boundary between the Norwegian and Barents Seas.

  After the war, the sea became a Cold War flashpoint, with the Soviet Northern Fleet treating it as its gateway to the Atlantic. That contest ended with the Cold War, but it left behind the K-278 Komsomolets, which sank in 1989 with radioactive material still onboard.

  The most economically important discovery came in 1993, when Norway began undersea oil production. The Ormen Lange gas field, at depths of 800 to 1,100 metres, began producing gas in 2007 and is connected to the Langeled pipeline, at the time the world's longest underwater pipeline. In 2019 an estimated 6.5 cubic hectometres of crude oil remained in the Norwegian Sea. At the Kristin field, conditions are extreme: temperatures reach 170 degrees Celsius and gas pressure exceeds 900 bar, or 900 times normal atmospheric pressure.

• 8. Mapping an Unmapped Sea

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  The first reasonably reliable map of northern Europe, the Carta marina of 1539, showed the Norwegian Sea only as coastal waters and depicted nothing north of the North Cape. The open Norwegian Sea appeared on maps in the 17th century, framed as part of the then-sought Northern Sea Route and as a rich whaling ground.

  Jan Mayen island was discovered in 1607 and became an important base for Dutch whalers. The first depth measurements of the Norwegian Sea were taken in 1773 by Constantine Phipps aboard HMS Racehorse during a North Pole expedition.

  Scientific oceanography came later. Declining yields of cod and herring off the Lofoten in the late 19th century prompted the Norwegian government to investigate. The zoologist Georg Ossian Sars and the meteorologist Henrik Mohn persuaded the government in 1874 to fund a scientific expedition. Between 1876 and 1878 they explored much of the sea aboard the vessel Vøringen. The data Mohn gathered allowed him to build the first dynamic model of ocean currents, one that incorporated winds, pressure differences, water temperature, and salinity and held up well against later measurements.

  In 2019, deposits of iron, copper, zinc, and cobalt were found on the Mohn Ridge, most likely from hydrothermal vents, opening a new chapter in the sea's long history of resource extraction.