The North Sea is a marginal, epeiric sea on the European continental shelf. The Dover Strait and the English Channel in the south and the Norwegian Sea in the north connect it to the Atlantic Ocean. It is more than long and wide, with an area of around . A large part of the European drainage basin empties into the North Sea including water from the Baltic Sea.

Much of the sea's coastal features are the result of glacial movements. Deep fjords and sheer cliffs mark the Norwegian and parts of the Scottish coastline, whereas the southern coasts consist of sandy beaches and mudflats. These flatter areas are particularly susceptible to flooding, especially as a result of storm tides. Elaborate systems of dikes have been constructed to protect coastal areas.

The Romans and the Vikings extended their territory across the sea. The Hanseatic League, the Netherlands, and finally the British sought to dominate commerce on the North Sea and through it to access the markets and resources of the world. Commercial enterprises, growing populations and limited resources gave the nations on the North Sea the desire to control or access it for their own commercial, military, and colonial ends.

In recent decades, its importance has shifted from the military and geopolitical to the purely economic. While traditional activities such as fishing and shipping have continued to grow, newer resources such as fossil fuels and wind and wave energy have also been discovered or developed.

Geography

The North Sea is bounded by the Orkney Islands and east coasts of England and Scotland to the west and the northern and central European mainland to the east and south, including Norway, Denmark, Germany, the Netherlands, Belgium, and France. In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively. In the north it is bordered by the Shetland Islands, and connects with the Norwegian Sea, which lies in the very north-eastern part of the Atlantic.

It is more than long and wide, with an area of and a volume of . Around the edges of the North Sea are sizeable islands and archipelagos, including Shetland, Orkney, and the Frisian Islands. The North Sea receives freshwater from a number of European continental watersheds, as well as the British Isles island watersheds. A large part of the European drainage basin empties into the North Sea including water from the Baltic Sea. The largest and most important affecting the North Sea are the Elbe and the Rhine - Meuse watershed. Around 184 million people live in the catchment area of the rivers that flow into the North Sea encompassing some highly industrialized areas.

Major features

For the most part, the sea lies on the European continental shelf with a mean depth of . The only exception is the Norwegian trench which extends parallel to the Norwegian shoreline from Oslo to an area north of Bergen. It is between wide and has a maximum depth of . The Dogger Bank, a vast moraine, or accumulation of unconsolidated glacial debris, rises to a mere 15 to 30 metres (50–100 ft) below the surface. This feature has produced the finest fishing location of the North Sea.

The Long Forties and the Broad Fourteens are large areas with roughly uniform depth in fathoms, (forty fathoms and fourteen fathoms or 73 and 26 m deep respectively). These great banks and others make the North Sea particularly hazardous to navigate, which has been alleviated by the implementation of satellite navigation systems.

Hydrology

Temperature and salinity

The average temperature in summer is and in the winter. Climate change has been attributed to a rise in the average temperature of the North Sea. Air temperatures in January range on average between and in July between . The winter months see frequent gales and storms.

The salinity averages between 34 to 35 grams of salt per litre of water. The salinity has the highest variability where there is fresh water inflow, such as at the Rhine and Elbe estuaries, the Baltic Sea exit and along the coast of Norway.

Water circulation and tides

The main pattern to the flow of water in the North Sea is an anti-clockwise rotation along the edges.

The North Sea is an arm of the Atlantic Ocean receiving the majority of ocean current from the northwest opening, and a lesser portion of warm current from the smaller opening at the English Channel. These tidal currents leave along the Norwegian coast. Surface and deep water currents may move in different directions. Low salinity surface coastal waters move offshore, and deeper, denser high salinity waters move in shore.

The North Sea located on the continental shelf has different waves than those in deep ocean water. The wave speeds are diminished and the wave amplitudes are increased. In the North Sea there are two amphidromic systems and a third incomplete amphidromic system. In the North Sea the average tide difference in wave amplitude is between .

The Kelvin tide of the Atlantic ocean is a semidiurnal wave which travels northward. Some of the energy from this wave travels through the English Channel into the North Sea. The wave still travels northward in the Atlantic Ocean, and once past the British Isles, the Kelvin wave turns east and south and once again enters into the North Sea.

Coasts

The eastern and western coasts of the North Sea are jagged, formed by glaciers during the ice ages. The coastlines along the southernmost part are covered with the remains of deposited glacial sediment. The Norwegian mountains plunge into the sea creating deep fjords and archipelagos. South of Stavanger, the coast softens, the islands become fewer. The eastern Scottish coast is similar, though less severe than Norway. From north east of England, the cliffs become lower and are composed of less resistant moraine, which erodes more easily, so that the coasts have more rounded contours. In Holland, Belgium and in the east of England (East Anglia) the littoral is low and marshy. The east coast and south-east of the North Sea (Wadden Sea) have coastlines that are mainly sandy and straight owing to longshore drift, particularly along Belgium and Denmark.

Coastal management

The southern coastal areas were originally amphibious flood plains and swampy land. In areas especially vulnerable to storm tides, people settled behind elevated levees and on natural areas of high ground such as spits and Geestland. As early as 500 BC, people were constructing artificial dwelling hills higher than the prevailing flood levels. It was only around the beginning of the High Middle Ages, in 1200 AD, that inhabitants began to connect single ring dikes into a dike line along the entire coast, thereby turning amphibious regions between the land and the sea into permanent solid ground.

The modern form of the dikes supplemented by overflow and lateral diversion channels, began to appear in the 17th and 18th centuries, built in the Netherlands. The North Sea Floods of 1953 and 1962 were impetus for further raising of the dikes as well as the shortening of the coast line so as to present as little surface area as possible to the punishment of the sea and the storms. Currently, 27% of the Netherlands is below sea level protected by dikes, dunes, and beach flats.

Coastal management today consists of several levels. The dike slope reduces the energy of the incoming sea, so that the dike itself does not receive the full impact. Dikes that lie directly on the sea are especially reinforced. The dikes have, over the years, been repeatedly raised, sometimes up to and have become flatter in order to better reduce the erosion of the waves. Where the dunes are sufficient to protect the land behind them from the sea, these dunes are planted with beach grass to protect them from erosion by wind, water, and foot traffic.

Storm tides

Storm tides threaten, in particular, the coasts of the Netherlands, Belgium, Germany, and Denmark and low lying areas of eastern England particularly around The Wash and Fens.Storm surges are caused by changes in barometric pressure combined with strong wind created wave action.

The first recorded storm tide flood was the Julianenflut, on 17 February 1164. In its wake the Jadebusen, (a bay on the coast of Germany), began to form.A storm tide in 1228 is recorded to have killed more than 100,000 people. In 1362, the Second Marcellus Flood, also known as the Grote Manndränke, hit the entire southern coast of the North Sea. Chronicles of the time again record more than 100,000 deaths as large parts of the coast were lost permanently to the sea, including the now legendary lost city of Rungholt.In the twentieth century, the North Sea flood of 1953 flooded several nations' coasts and cost more than 2,000 lives.315 citizens of Hamburg died in the North Sea flood of 1962.

Tsunamis

The Storegga Slides were a series of underwater landslides, in which a piece of the Norwegian continental shelf slid into the Norwegian Sea. The immense landslips occurred between 8150 BC and 6000 BC, and caused a tsunami up to high that swept through the North Sea, having the greatest effect on Scotland and the Faeroe Islands.The Dover Straits earthquake of 1580 is among the first recorded earthquakes in the North Sea measuring between 5.3 and 5.9 on the Richter Scale. This event caused extensive damage in Calais both through its tremors and two tsunamis The largest earthquake ever recorded in the United Kingdom was the 1931 Dogger Bank earthquake, which measured 6.1 on the Richter Scale and caused a tsunami that flooded parts of the British coast.

Geology

Shallow epicontinental seas like the current North Sea have since long existed on the European continental shelf. The rifting that formed the northern part of the Atlantic Ocean during the Jurassic and Cretaceous periods, from about , caused tectonic uplift in the British Isles. Since then, a shallow sea has almost continuously existed between the highs of the Fennoscandian Shield and the British Isles. This precursor of the current North Sea has grown and shrunk with the rise and fall of the eustatic sea level during geologic time. Sometimes it was connected with 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.

During the Late Cretaceous, about , all of modern mainland Europe except for Scandinavia was a scattering of islands. By the Early Oligocene, , the emergence of Western and Central Europe had almost completely separated the North Sea from the Tethys Ocean, which gradually shrank to become the Mediterranean Sea as Southern Europe and South West Asia became dry land. The North Sea was cut off from the English Channel by a narrow land bridge until that was breached by at least two catastrophic floods between 450,000 and 180,000 years ago. Since the start of the Quarternary period about , the eustatic sea level has fallen during each glacial period and then risen again. Every time the ice sheet reached its greatest extent, the North Sea became almost completely dry. The present-day North Sea coastline formed when, after the Last Glacial Maximum (the peak of the glaciation during the last ice age) 20,000 years ago, the sea began to flood the European continental shelf. The North Sea coastline still undergoes changes following changes in the worldwide sea level, tectonic movements, storm surges, erosion, the rise and fall of sea levels, shingle drifts as well as the deposition of sands and clastics in paralic environments.

Natural history

Fish and shellfish

Copepods and other zooplankton are plentiful in the North Sea. These tiny organisms are crucial elements of the food chain supporting many species of fish. Over 230 species of fish live in the North Sea. Cod, haddock, whiting, saithe, plaice, sole, mackerel, herring, pouting, sprat, and sandeel are all very common and are those which are fished commercially. Due to the various depths of the North Sea trenches and differences in salinity, temperature, and water movement, some fish such as blue-mouth redfish and rabbitfish reside only in small areas of the North Sea.

Crustaceans are also commonly found throughout the sea. Norway lobster, deep-water prawns, and brown shrimp are all commercially fished, but other species of lobster, shrimp, oyster, mussels and clams all live in the North Sea. Recently non-indigenous species have become established including the Pacific oyster and Atlantic jackknife clam.

Birds

The coasts of the North Sea are home to nature reserves including the Ythan Estuary, Fowlsheugh Nature Preserve, and Farne Islands in the UK and The Wadden Sea National Parks in Germany. These locations provide breeding habitat for dozens of bird species. Tens of millions of birds make use of the North Sea for breeding, feeding, or migratory stopovers every year. Populations of Black legged Kittiwakes, Atlantic Puffins, Northern fulmars, and species of petrels, gannets, seaducks, loons (divers), cormorants, gulls, auks, and terns, and many other seabirds make these coasts popular for birdwatching.

Marine mammals

The North Sea is also home to marine mammals. Common seals, and Harbour porpoises can be found along the coasts, at marine installations, and on islands. The very northern North Sea islands like the Shetlands are occasionally home to a larger variety of pinnipeds including bearded, harp, hooded and ringed seals, and even walrus. North Sea cetaceans include various porpoise, dolphin and whale species.

Flora

Plant species in the North Sea include species of wrack, among them bladder wrack, knotted wrack, and serrated wrack. Algae, macroalgal, and kelp, such as oarweed and laminaria hyperboria, and species of maerl are found as well. Eelgrass, formerly common in the entirety of the Wadden Sea, was nearly wiped out in the 20th century by a disease. Similarly, sea grass used to coat huge tracts of ocean floor, but have been damaged by trawling and dredging have diminished its habitat and prevented its return. Invasive Japanese seaweed has spread along the shores of the sea clogging harbours and inlets and has become a nuisance.

Biodiversity and conservation

Flamingos, pelicans, and Great Auk were once found along the southern shores of the North Sea, but went extinct over the 2nd millennium. Gray whale also resided in the North Sea but were driven to extinction in the Atlantic in the 1600s Other species have seen dramatic declines in population, though they are still to be found; right whales, sturgeon, shad, rays, skates and salmon among other species were common in the North Sea into the 20th century, when numbers declined due to overfishing.Other factors like the introduction of non-indigenous species, industrial and agricultural pollution, trawling and dredging, human-induced eutrophication, construction on coastal breeding and feeding grounds, sand and gravel extraction, offshore construction, and heavy shipping traffic have also contributed to the decline.The OSPAR commission manages the OSPAR convention to counteract the harmful effects of human activity on wildlife in the North Sea, preserve endangered species, and provide environmental protection. All North Sea border states are signatories of the MARPOL 73/78 Accords which preserves the marine environment by preventing pollution from ships.Germany, Denmark, and the Netherlands also have a trilateral agreement for the protection of the Wadden Sea, or mudflats, which run along the coasts of the three countries on the southern edge of the North Sea.

History

Name

One of the earliest recorded names was Septentrionalis Oceanus, or "Northern Ocean" which was cited by Pliny. However, the Celts who lived along its coast referred to it as the Morimaru, the "dead sea", which was also taken up by the Germanic peoples, giving Morimarusa. This name refers to the "dead water" patches resulting from a layer of fresh water sitting on top of a layer of salt water making it quite still. Names referring to the same phenomenon lasted into the Middle Ages, e.g., Old High German mere giliberōt and Middle Dutch lebermer or libersee. Other common names in use for long periods were the Latin terms Mare Frisicum, Oceanum- or Mare Germanicum as well as their English equivalents, "Frisian Sea", "German Ocean", "German Sea" and "Germanic Sea" (from the Latin Mare Germanicum).

Early history

The North Sea has provided waterway access for commerce and conquest. Many areas have access to the North Sea with its long coastline and European rivers which empty into it. The British Isles had been protected from invasion by the North Sea waters until the Roman conquest of Britain in 43 AD. The Romans established organised ports, shipping increased and sustained trade began. When the Romans abandoned Britain in 410 the Germanic Angles, Saxons, and Jutes began the next great migration across the North Sea during the Migration Period invading England.

The Viking Age began in 793 with the attack on Lindisfarne and for the next quarter-millennium the Vikings ruled the North Sea. In their superior longships, they raided, traded, and established colonies and outposts on the Sea's coasts. From the Middle Ages through the 15th century, the north European coastal ports exported domestic goods, dyes, linen, salt, metal goods and wine. The Scandinavian and Baltic areas shipped grain, fish, naval necessities, and timber. In turn the north Sea countries imported high grade cloths, spices, and fruits from the Mediterranean region Commerce during this era was mainly undertaken by maritime trade due to underdeveloped roadways.

In the 13th century the Hanseatic League, though centred on the Baltic Sea, started to control most of the trade through important members and outposts on the North Sea. The League lost its dominance in the 16th century, as neighbouring states took control of former Hanseatic cities and outposts and internal conflict prevented effective cooperation and defence. Furthermore, as the League lost control of its maritime cities new trade routes emerged which provided Europe with Asian, American, and African goods.

Age of sail

The 17th century Dutch Golden Age during which Dutch herring, cod and whale fisheries reached an all time high saw Dutch power at its zenith. Important overseas colonies, a vast merchant marine, powerful navy and large profits made the Dutch the main challengers to an ambitious England. This rivalry led to the first three Anglo-Dutch Wars between 1652 and 1673 which ended with Dutch victories. After the Glorious Revolution the Dutch prince William ascended to the English throne. With both countries united, commercial, military, and political power shifted from Amsterdam to London. The Great Northern War(1700–21) and the War of the Spanish Succession (1701–1714) were fought concurrently.The British did not face a challenge to their dominance of the North Sea until the twentieth century.

Modern era

Tensions in the North Sea were again heightened in 1904 by the Dogger Bank incident, in which Russian naval vessels mistook British fishing boats for Japanese ships and fired on them, and then upon each other.

During the First World War, Great Britain's Grand Fleet and Germany's Kaiserliche Marine faced each other on the North Sea, which became the main theatre of the war for surface action. Britain's larger fleet was able to establish an effective blockade for most of the war that restricted the Central Powers' access to many crucial resources. Major battles included the Battle of Heligoland Bight, the Battle of the Dogger Bank, and the Battle of Jutland.World War One was also the first in which submarine warfare was used extensively and a number of submarine actions occurred in the North Sea.

The Second World War also saw action in the North Sea, though it was restricted more to aircraft reconnaissances, aircraft fighter/bombers, submarines and smaller vessels such as minesweepers, and torpedo boats and similar vessels.

In the last years of the war and the first years thereafter, hundreds of thousands of tons of weapons were disposed of by being sunk in the North Sea.

After the war, the North Sea lost much of its military significance because it is bordered only by NATO member-states. However, it gained significant economic importance in the 1960s as the states on the North Sea began full-scale exploitation of its oil and gas resources. The North Sea continues to be an active trade route.

Economy

Political status

The countries bordering the North Sea all claim the of territorial waters within which they have exclusive fishing rights. The Common Fisheries Policy of the European Union (EU) exists to coordinate fishing rights and assist with disputes between EU states and the EU border state of Norway.

After the discovery of mineral resources in the North Sea, Convention on the Continental Shelf established country rights which are largely divided along the median line. The median line is defined as the line "every point of which is equidistant from the nearest points of the baselines from which the breadth of the territorial sea of each State is measured."The ocean floor border between Germany, the Netherlands, and Denmark was only reapportioned after protracted negotiations and a judgement of the International Court of Justice.

Oil and gas

As early as 1859, oil was discovered in onshore areas around the North Sea and natural gas as early as 1910.



Test drilling began in 1966 and then, in 1969, Phillips Petroleum Company discovered the Ekofisk oil field distinguished by valuable, low-sulphur oil. Commercial exploitation began in 1971 with tankers and, after 1975, by a pipeline, first to Teesside, England and then, after 1977, also to Emden, Germany.

The exploitation of the North Sea oil reserves began just before the 1973 oil crisis, and the climb of international oil prices made the large investments needed for extraction much more attractive.

Although the production costs are relatively high, the quality of the oil, the political stability of the region, and the nearness of important markets in western Europe has made the North Sea an important oil producing region. The largest single humanitarian catastrophe in the North Sea oil industry was the destruction of the offshore oil platform Piper Alpha in 1988 in which 167 people lost their lives.

Besides the Ekofisk oil field, the Statfjord oil field is also notable as it was the cause of the first pipeline to span the Norwegian trench. The largest natural gas field in the North Sea, Troll gas field, lies in the Norwegian trench dropping over requiring the construction of the enormous Troll A platform to access it.

The price of Brent Crude, one of the first types of oil extracted from the North Sea, is used today as a standard price for comparison for crude oil from the rest of the world. The North Sea contains western Europe's largest oil and natural gas reserves and is one of the world's key non-OPEC producing regions.

Fishing

The North Sea is Europe's main fishery accounting for over five percent of international commercial fish caught. Fishing in the North Sea is concentrated in the southern part of the coastal waters. The main method of fishing is trawling. In 1995, the total volume of fish and shellfish caught in the North Sea was approximately 3.5 million tonnes. Besides fish, it is estimated that one million tonnes (907 thousand long tons or 1.15 million short tons) of unmarketable by-catch and Cetacean bycatch is caught and discarded each year, including 250,000 sea turtles and 7,000 harbour porpoises.

In recent decades, overfishing has left many fisheries unproductive, disturbing marine food chain dynamics and costing jobs in the fishing industry. Herring, cod and plaice fisheries may soon face the same plight as mackerel fishing which ceased in the 1970s due to overfishing.The objective of the European Union Common Fisheries Policy is to minimize the environmental impact associated with resource use by reducing fish discards, increasing productivity of fisheries, stabilising markets of fisheries and fish processing, and supplying fish at reasonable prices for the consumer.

Mineral resources

In addition to oil, gas, and fish, the states along the North Sea also take millions of cubic metres per year of sand and gravel from the ocean floor. These are used for beach nourishment, land reclamationand construction.Rolled pieces of amber, usually small but occasionally of very large size, may be picked up on the east coast of England. It is also found at various localities along the amber belt of the Danish, Swedish and Frisian Island shorelines.

Renewable energy

Due to the strong prevailing winds, countries on the North Sea, particularly Germany and Denmark, have used the areas near the coast for wind power since the 1990s. Other wind farms have been commissioned, including Windpark Egmond aan Zee and Scroby Sands.However, the usage of offshore wind farms has met some resistance. Concerns include shipping collisions, reliability, environmental effects on ocean ecology and wildlife such as fish and migratory birds, and the rising costs of constructing wind farms.Nonetheless, development of North Sea wind power is continuing, with plans for additional wind farms off the coasts of Germany, the Netherlands, and the UK. There have also been proposals for a transnational power grid in the North Sea to connect new offshore wind farms.

Energy production from tidal power is still in a pre-commercial stage. The European Marine Energy Centre has installed a wave testing system at Billia Croo on the Orkney mainland and a tidal power testing station on the nearby island of Eday. Since 2003, a prototype Wave Dragon energy converter has been in operation at Nissum Bredning fjord of northern Denmark.

Tourism

The beaches and coastal waters of the North Sea are popular destinations for tourists. The Belgian, Dutch, German and Danish coasts are especially developed for tourism.The North Sea Trail is a long-distance trail linking seven countries around the North Sea. Windsurfing and sailing are popular sports because of the strong winds. Mudflat hiking, recreational fishing and birdwatching are among other popular activities.

The climatic conditions on the North Sea coast are often claimed to be especially healthful. As early as the 19th century, travellers used their stays on the North Sea coast as curative and restorative vacations. The sea air, temperature, wind, water, and sunshine are counted among the beneficial conditions that are said to activate the body's defences, improve circulation, strengthen the immune system, and have healing effects on the skin and the respiratory system.

Marine traffic

The North Sea is important for marine traffic and its shipping lanes are among the busiest in the world. Major ports are located along its coasts: Rotterdam, the third busiest port in the world, Antwerp and Hamburg, both in the top 25, Bremen/Bremerhaven and Felixstowe, both in the top 30 busiest container seaports, as well as the Port of Bruges-Zeebrugge, Europe's leading RoRo port.



Traffic in the North Sea can be difficult in high density traffic zones so ports regulate traffic and monitor vessels in the North Sea lanes. Fishing boats, oil and gas platforms as well as merchant traffic from Baltic ports share routes on the North Sea. The Dover Strait sees more than 400 vessels a day.

The North Sea coasts are home to numerous canals and canal systems to facilitate traffic between and among rivers, artificial harbours, and the sea. The Kiel Canal, connecting the North Sea with the Baltic Sea, is the most heavily used artificial seaway in the world. It saves an average of , instead of the voyage around the Jutland Peninsula. The North Sea Canal connects Amsterdam with the North Sea.

See also

• Doggerland
• List of languages of the North Sea
• North Sea Commission
• Principality of Sealand

Notes

References

Further reading

External links

• The North Sea in brief
• See Interactive Map over Oil and Gas Resources in the North Sea
• Etymology and History of Names
• Old map: Manuscript chart of the North Sea, VOC, ca.1690 (high resolution zoomable scan)
• Atlas of Palaeogeography and Lithofacies - Hydrodynamic Environment page 150
• Sea temperature and salinity trends
• Silver Pit chart
• OSPAR Commission Homepage an international commission designed to protect and conserve the North-East Atlantic and its resources
• The Physical Geography of Western Europe By Eduard A. Koster
• North Sea Region Programme 2007-2013 transnational cooperation programme under the European Regional Development Fund