North Sea

The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. It is a sea on the European continental shelf. It connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Sea in the north. It is more than 970 kilometres (600 mi) long and 580 kilometres (360 mi) wide, covering 570,000 square kilometres (220,000 sq mi).

The sea is important to people in many ways. It carries ships along key shipping lanes in northern Europe and is a major fishery. Its coasts are popular places for visitors and holidays in the countries that border it. The sea is also a rich source of energy, including wind and wave power.

The North Sea has played a big part in the politics and military history of Northern Europe, from the Middle Ages to modern times. The sea was the centre of the Vikings' rise. The Hanseatic League, the Dutch Republic, and Britain all wanted control of the North Sea so they could reach the world's markets and resources. Because it is Germany's only outlet to the ocean, the North Sea was strategically important during both world wars.

The coast has many different landscapes. In the north, deep fjords and steep cliffs mark much of the Norwegian and Scottish coastlines. In the south, the coast is mainly sandy beaches, the mouths of long rivers, and wide mudflats. Because many people live nearby, many factories are built there, and the sea and the land around it are used heavily. This causes environmental problems that affect the sea's ecosystems. These problems, which commonly include overfishing, runoff from industry and farming, dredging, and dumping, have led to many efforts to prevent damage and to protect the sea's long-term economic benefits.

For other uses, see North Sea (disambiguation).

Geography

Main article: Geography of the North Sea

See also: List of rivers discharging into the North Sea

Main article: Coastline of the North Sea

Further information: Afsluitdijk, Delta Works, Flood control in the Netherlands, Thames Barrier, and Zuiderzee Works

Main article: Storm tides of the North Sea

The North Sea lies between Great Britain and the central European mainland, including Norway, Denmark, Germany, the Netherlands, Belgium, and France. It is bounded by the Orkney Islands and the east coast of Great Britain to the west, and by the Shetland Islands to the north. In the southwest, beyond the Straits of Dover, it becomes the English Channel, which connects to the Atlantic Ocean. In the east, it connects to the Baltic Sea through the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden. In the north, it connects with the Norwegian Sea, which is a marginal sea in the Arctic Ocean. The sea is more than 970 kilometres (600 mi) long and 580 kilometres (360 mi) wide, with an area of 750,000 square kilometres (290,000 sq mi). Around its edges are sizeable islands and archipelagos, including Shetland, Orkney, and the Frisian Islands. Water flows in from many European drainage basins and the British Isles, with the Elbe, Rhine, and Meuse among the largest rivers. About 185 million people live in the catchment area of the rivers that flow into the sea. For the most part, the sea lies on the European continental shelf, with a mean depth of 90 metres (300 ft). The Norwegian trench is the only exception, running along the Norwegian coast from Oslo to an area north of Bergen. The Dogger Bank, a moraine of glacial debris, rises close to the surface and has produced the finest fishing location in the North Sea. Its many banks, including the Long Forties, the Broad Fourteens, Cleaver Bank, Fisher Bank, and Noordhinder Bank, make navigation hazardous, a problem that has been eased by satellite navigation systems. The Devil's Hole, east of Dundee, Scotland, is a series of deep trenches.

The International Hydrographic Organization defines the limits of the North Sea. On the southwest, the line joins the Walde Lighthouse in France and Leathercoat Point in England. On the northwest, it runs from Dunnet Head in Scotland through Hoy, Mainland, Costa Head, Papa Westray, North Ronaldsay, and on to Horse Island. On the north, it runs past Mainland, Yell, Unst, Herma Ness, and Muckle Flugga, then along the parallel of 61°00' North. On the east, the limit is the western edge of the Skagerrak, a line between Hanstholm and Lindesnes. Average temperatures are 17 °C (63 °F) in summer and 6 °C (43 °F) in winter, and they have been rising since 1988, which has been attributed to climate change. Winters bring frequent gales and storms. The salinity averages 34 to 35 grams per litre of water, and it varies most near fresh water inflows. The main pattern of water flow is an anti-clockwise rotation along the edges, and the sea receives ocean currents from the Atlantic. Tides in the North Sea form two amphidromic systems and a third incomplete one. The Kelvin wave, a semidiurnal wave, enters the North Sea from the Atlantic.

The eastern and western coasts are jagged, shaped by glaciers during the ice ages. Norway's mountains plunge into the sea, creating deep fjords and archipelagos. Moving south from the north-east of England, the cliffs become lower and erode more easily. The coasts of the Netherlands, Belgium, and East Anglia are low and marshy, while the Wadden Sea coast is mainly sandy and straight because of longshore drift. Originally, the southern coastal areas were flood plains and swampy land. People built artificial dwelling hills as early as 500 BC, and the High Middle Ages brought dikes along the whole coast. Today, 27% of the Netherlands is below sea level, protected by dikes, dunes, and beach flats, and the dikes have been repeatedly raised. Storm surges threaten the coasts of the Netherlands, Belgium, Germany, and Denmark, as well as low-lying parts of eastern England near The Wash and the Fens. The first recorded storm tide flood was on 17 February 1164. A storm tide in 1228 is recorded to have killed more than 100,000 people. In 1362, the Second Marcellus Flood hit the southern coast, and the lost city of Rungholt was among the land lost to the sea. The North Sea flood of 1953 cost more than 2,000 lives, and 315 citizens of Hamburg died in the North Sea flood of 1962. Though rare, the North Sea has had several documented tsunamis, including those caused by the Storegga Slides and the Dover Straits earthquake of 1580. In 1995, the 25.6 m (84 ft) tall Draupner wave was the first rogue wave observed using scientific instruments.

Geology

Main articles: Geology of the North Sea and Geology of southern North Sea

Shallow epicontinental seas like the current North Sea have existed on the European continental shelf for a very long time. The rifting that formed the northern part of the Atlantic Ocean during the Jurassic and Cretaceous periods caused tectonic uplift in the British Isles. Since then, a shallow sea has almost always existed between the uplands of the Fennoscandian Shield and the British Isles. This early version of the North Sea grew and shrank as the eustatic sea level rose and fell over geologic time. At times it was connected to other shallow seas, such as the sea above the Paris Basin to the south-west, the Paratethys Sea to the south-east, or the Tethys Ocean to the south.

Over millions of years, the land changed greatly. By the Early Oligocene, Western and Central Europe had almost completely separated the North Sea from the Tethys Ocean, which slowly shrank into the Mediterranean. The North Sea was cut off from the English Channel by a narrow land bridge until at least two huge floods broke through it between 450,000 and 180,000 years ago. Since the start of the Quaternary period, the sea level has fallen during each cold period and risen again afterward. When the ice sheet was at its largest, the North Sea became almost completely dry, and the dry land was known as Doggerland. The coastline we see today formed after the Last Glacial Maximum, when the sea began to flood the European continental shelf. In 2006, a bone fragment was found while drilling for oil in the North Sea. Analysis showed it was from a Plateosaurus that lived 199 to 216 million years ago.

Nature

See also: List of fish of the North Sea

Copepods and other zooplankton are plentiful in the North Sea. These tiny organisms are important parts of the food chain that supports many kinds of fish. More than 230 species of fish live there. Cod, haddock, whiting, saithe, plaice, sole, mackerel, herring, pouting, sprat, and sandeel are very common and are caught for sale. Because the depths, saltiness, temperature, and water movement vary across the sea, some fish, such as blue-mouth redfish and rabbitfish, live only in small areas. Crustaceans are also common throughout the sea. Norway lobster, deep-water prawns, and brown shrimp are caught for sale, and other lobsters, shrimps, oysters, mussels, and clams also live there. Recently, some non-native species have settled in, including the Pacific oyster and the Atlantic jackknife clam.

The coasts of the North Sea have nature reserves, including the Ythan Estuary, Fowlsheugh Nature Preserve, and Farne Islands in the UK, and the Wadden Sea National Parks in Denmark, Germany, and the Netherlands. These places give breeding habitat to dozens of bird species. Tens of millions of birds use the North Sea every year for breeding, feeding, or resting during migration. Many birds, including black-legged kittiwakes, Atlantic puffins, northern gannets, northern fulmars, petrels, seaducks, loons (divers), cormorants, gulls, auks, and terns, along with many other seabirds, make these coasts popular for birdwatching.

Common seals, grey seals, and harbour porpoises can be found along the coasts, near marine installations, and on islands. The far northern islands, such as the Shetland Islands, are sometimes home to more kinds of pinnipeds, including bearded, harp, hooded, and ringed seals, and even walrus. North Sea cetaceans include several kinds of porpoises, dolphins, and whales.

Plants in the North Sea include types of wrack, such as bladder wrack, knotted wrack, and serrated wrack. Algae, macroalgae, kelp (such as oarweed and laminaria hyperboria), and maerl are also found there. Eelgrass was once common throughout the Wadden Sea, but a disease nearly wiped it out in the 20th century. Sea grass once covered large areas of the ocean floor, but damage from trawling and dredging has reduced its habitat and stopped it from returning. The invasive Japanese seaweed has spread along the shores, clogging harbours and inlets and becoming a nuisance.

Because many people live along its shores and industry is strong there, the North Sea's wildlife has suffered from pollution, overhunting, and overfishing. Flamingos and pelicans were once found along the southern shores but died out during the second millennium. Walruses visited the Orkney Islands until the mid-16th century, which was within their normal range. Grey whales also lived in the North Sea but were wiped out in the Atlantic in the 17th century. Other species, such as North Atlantic right whales, sturgeon, shad, rays, skates, and salmon, were common until the 20th century, when their numbers fell because of overfishing. Many of these species are still found but in much smaller numbers. Other causes of decline include non-indigenous species, industrial and agricultural pollution, trawling and dredging, human-caused eutrophication, building on coastal breeding and feeding grounds, sand and gravel digging, offshore construction, and heavy ship traffic. For example, a local orca group was lost in the 1960s, probably because of a peak in PCB pollution at that time.

The OSPAR commission runs the OSPAR convention, which works to reduce the harm human activity causes to wildlife in the North Sea, protect endangered species, and provide environmental protection. All of the countries bordering the North Sea have agreed to the MARPOL 73/78 rules, which protect the sea by preventing pollution from ships. Germany, Denmark, and the Netherlands also have a three-way agreement to protect the Wadden Sea, or mudflats, which run along the coasts of those three countries on the southern edge of the North Sea.

Names

The North Sea has had various names throughout history. One of the earliest recorded names was Septentrionalis Oceanus, meaning "Northern Ocean", which was mentioned by Pliny. He also wrote that the Cimbri called it Morimarusa, meaning "Dead Sea". The English name "North Sea" probably came from the Dutch Noordzee. The Dutch may have chosen it to contrast with the Zuiderzee ("South Sea"), which lay south of Frisia, or because the sea is generally north of the Netherlands.

Before "North Sea" was adopted, English speakers used "German Sea" or "German Ocean", from the Latin names Mare Germanicum and Oceanus Germanicus. These names were used until the First World War. Other names used for long periods were the Latin Mare Frisicum and the English "Frisian Sea". Today, the sea has these names in other local languages: Danish: Vesterhavet (meaning "West Sea") or Nordsøen; Dutch: Noordzee; Dutch Low Saxon: Noordzee; French: Mer du Nord; West Frisian: Noardsee; German: Nordsee; Low German: Noordsee; North Frisian: Weestsiie (meaning "West Sea"); Swedish: Nordsjön; Norwegian: Nordsjøen; Scots: North Sea; and Scottish Gaelic: An Cuan a Tuath.

History

Main article: History of the North Sea

The North Sea has long provided waterways for trade and conquest, since many areas border it and European rivers flow into it. Little written evidence exists from before the Roman conquest of Britain in 43 CE, but archaeology shows that cultures and technologies spread across the sea, and some early peoples relied on fishing, whaling, and sea trade. When the Romans abandoned Britain in 410, the Angles, Frisians, Saxons, and Jutes crossed the sea during the Migration Period. The Viking Age began in 793 with an attack on Lindisfarne, and for about 250 years the Vikings ruled the North Sea from their longships. In the 13th century the Hanseatic League, which was centred on the Baltic Sea, came to control most of the trade on the North Sea, but it lost its power in the 16th century. New trade routes then brought Asian, American, and African goods to Europe.

In the 17th century, the Dutch Golden Age made the Netherlands the strongest maritime power in the North Sea, until England challenged it. The first three Anglo-Dutch Wars were fought between 1652 and 1673 and ended with Dutch victories, but after the Glorious Revolution in 1688, the Dutch prince William became king of England, and power shifted to London. In 1904, tensions rose again after the Dogger Bank incident, when Russian ships on their way to the Far East during the Russo-Japanese War fired on British fishing boats. During the First World War, Britain's Grand Fleet and Germany's Kaiserliche Marine faced each other in the North Sea, which became the main theatre of the war for surface action. Britain's larger fleet and the North Sea Mine Barrage blocked the Central Powers from many key resources for most of the war. Major battles included the Battle of Heligoland Bight, the Battle of the Dogger Bank, and the Battle of Jutland, and the war also saw the first large-scale use of submarine warfare. The Second World War also brought action to the North Sea, mostly through aircraft, submarines, and smaller ships such as minesweepers and torpedo boats. After the war, large amounts of chemical weapons were dumped in the sea. Because only NATO member states border it, the North Sea lost much of its military importance, but in the 1960s it became economically important as nearby countries began using its oil and gas resources. It remains an active trade route today.

Economy

Countries that border the North Sea claim 12 nautical miles (22 km; 14 mi) of territorial waters, where they have exclusive fishing rights. The Common Fisheries Policy of the European Union (EU) helps coordinate fishing rights and settle disputes with Norway, an EU border state. After minerals were found in the early 1960s, the Convention on the Continental Shelf set country rights largely along the median line. The ocean floor border between Germany, the Netherlands, and Denmark was only settled in 1969, after long talks and a ruling by the International Court of Justice.

Oil was found on land around the North Sea as early as 1859, and natural gas as early as 1910. Land fields such as K12-B in the Netherlands are still used today. Offshore drilling began in 1966, and in 1969 Phillips Petroleum Company found the Ekofisk oil field, known for its valuable, low-sulphur oil. Oil was first moved by tankers in 1971 and, after 1975, by pipeline to Teesside in England and, after 1977, also to Emden in Germany. Production began just before the 1973 oil crisis, when rising oil prices made the large investments for extracting oil reserves more worthwhile. The Brae field was another major discovery. Although production costs are fairly high, the quality of the oil, the region's political stability, and nearby markets in western Europe have made the North Sea an important oil-producing area. The Statfjord oil field led to the first pipeline across the Norwegian trench. The largest natural gas field in the North Sea, Troll gas field, lies in that trench, and reaching it required the huge Troll A platform. Brent Crude, one of the first oils taken from the North Sea, is still used as a standard price for comparing crude oil from around the world. The region holds western Europe's largest oil and gas reserves. Industry body Oil & Gas UK said that spending in the UK sector fell because of rising costs, lower production, high tax rates, and less exploration. In January 2018, the North Sea had 184 offshore rigs, more than any other region in the world at that time. The British North Sea's oil and gas production peaked in 2000 and had declined by 2024, while offshore wind projects such as Dogger Bank grew to support renewable energy goals.

Main article: Fishing in the North Sea

The North Sea is Europe's main fishery, providing over 5% of international commercial fish catches. Most fishing takes place in the southern coastal waters, mainly by trawling. In 1995, about 3.5 million tonnes of fish and shellfish were caught, and it is estimated that one million tonnes of unwanted by-catch are caught and thrown back dead each year. Overfishing has left many fisheries unproductive, disturbing the food chain and costing jobs in the fishing industry. Mackerel fishing ended in the 1970s because of overfishing, and herring, cod and plaice may face the same fate. The goal of the Common Fisheries Policy is to reduce waste, improve fishery productivity, keep markets stable, and supply fish at fair prices.

Whaling was important from the 9th to the 13th century for Flemish whalers. Later, Dutch, English, Danish, and German whalers took huge numbers of whales and nearly depleted the right whales. This likely led to the loss of the Atlantic grey whale population. Whaling had ended by 1902. In 2010, a single grey whale returned after 300 years, probably the first of many to pass through the now ice-free Northwest Passage.

Besides oil, gas, and fish, the states along the North Sea take millions of cubic metres of sand and gravel from the ocean floor each year. These are used for beach nourishment, land reclamation, and construction. Pieces of amber may be found on England's east coast.

Further information: Renewable energy in the European Union and List of offshore wind farms in the North Sea

Strong prevailing winds and shallow water have made the North Sea a good place for wind power, especially in Germany and Denmark, since the 1990s. Horns Rev 1, completed in 2002, was one of the first large offshore wind farms in the world. As of 2013, the 630 megawatt (MW) London Array was the largest offshore wind farm, followed by Greater Gabbard wind farm (504 MW) and Walney Wind Farm (367 MW), all off the UK coast. Larger projects are planned, including Dogger Bank (4,800 MW), Norfolk Bank (7,200 MW), and the Irish Sea (4,200 MW). Some people have raised concerns about environmental effects, shipping collisions, reliability, and costs. However, studies in Denmark and the UK found the environmental concerns to be small. Plans for more wind farms continue, and there have been proposals for a transnational power grid in the North Sea to connect new offshore wind farms. Energy from tidal power is still at a pre-commercial stage. The European Marine Energy Centre has test sites at Billia Croo on the Orkney mainland and on the nearby island of Eday. A prototype Wave Dragon energy converter has operated in northern Denmark since 2003.

The beaches and coastal waters of the North Sea attract tourists, and the English, Belgian, Dutch, German, and Danish coasts are developed for tourism. The UK coast has beach resorts and links golf courses. The Scottish town of St. Andrews is famous as the home of golf. The North Sea Trail, a long-distance trail, links seven countries around the sea. Windsurfing and sailing are popular because of the strong winds, and mudflat hiking, recreational fishing, and birdwatching are also enjoyed. The Wadden Sea in Denmark, Germany, and the Netherlands is a UNESCO World Heritage Site.

See also: List of North Sea ports

The North Sea is important for shipping, and its shipping lanes are among the busiest in the world. Major ports along its coasts include Rotterdam, the busiest port in Europe, Antwerp, Hamburg, Bremen/Bremerhaven, Felixstowe, and the Port of Bruges-Zeebrugge, Europe's leading ro-ro port. Fishing boats, offshore service boats, pleasure craft, and merchant ships using North Sea ports and Baltic ports all share these routes. Because traffic is so heavy, ports use vessel traffic services to guide ships. Many canals link rivers, harbours, and the sea. The Kiel Canal, which connects the North Sea with the Baltic Sea, is the busiest artificial seaway in the world, and it saves about 250 nautical miles (460 km; 290 mi) compared with sailing around the Jutland peninsula. The North Sea Canal connects Amsterdam with the North Sea.

Critical Maritime Infrastructure

The North Sea has many important systems at sea and under the seabed. These include offshore oil and gas platforms, wind farms, pipelines, and cables that carry energy, electricity, and internet communications. Together they are called critical maritime infrastructure (CMI). Infrastructure is called "critical" when its disruption could have major effects on society and the economy. The North Sea is fairly shallow compared with deep oceans, which has made large offshore oil, gas, and wind projects possible. One regional assessment estimates that the North Sea has around 71,000 km of active subsea cables, about 5% of the global network, along with many pipelines. These systems depend on ports, ships, and onshore support, and they are changing as countries invest in cleaner energy.

Protecting these systems is difficult because they are spread across large sea areas, and many lie on or beneath the seabed, where they are hard to watch. Risks include accidents, storms, technical failures, criminal activity, and deliberate interference, such as damage to cables or attacks on digital control systems. Protection measures include monitoring, mapping cables and pipelines, backup systems, and better repair capacity. They also require cooperation between governments and private companies. Because many assets lie beyond territorial waters, international law also plays a role, though it does not give coastal states clear power to stop foreign vessels from gathering information about these systems.