Sea to the east of Britain and bounded by the coasts of Belgium, The Netherlands, Germany, Denmark, and Norway; part of the Atlantic Ocean; area 523,000 sq km/202,000 sq mi; average depth 55 m/180 ft, greatest depth 660 m/2,165 ft. The Dogger Bank extends east to west with shallows of as little as 11 m/36 ft, forming a traditionally well-stocked fishing ground. A deep channel follows the coast of Scandinavia reaching as far as the Skagerrak arm. In the northeast the North Sea joins the Norwegian Sea, and in the south it meets the Strait of Dover. It has several hundred oil platforms, 10,000 km/6,200 mi of gas pipeline (gas was discovered in 1965), and fisheries (especially mackerel and herring).
Physical characteristics The surface water temperature ranges from 2–16°C off the Danish coast, and from 7–13°C in the northwest where it is influenced by the West Wind Drift Current. Currents are generally in a slow anticlockwise direction, influenced by the prevailing winds. Salinity is highest along the German coast. Eastern shores are usually ice-bound in winter due to fresh water coming from the Baltic Sea. The major rivers entering the North Sea are the Rhine, Meuse, Elbe, Forth, Humber, and Thames. The tidal range varies from about 6 m/20 ft along the English coast to about 1 m/3.2 ft along the Scandinavian coast.
Human activity In 1995 there were 164 million people living around the North Sea, with a further 50 million visiting each year.
Overfishing Overfishing is an increasing threat to both marine biodiversity and the fishing industry. The spawning stock of cod in the North Sea, for example, had fallen from 277,000 tonnes in 1971 to 59,000 tonnes at the beginning of 2001, leading to the closure of more than 103,600 sq km/40,000 sq mi of sea to fishing for ten weeks. Environmentalists argue that overfishing is a major threat to marine biodiversity in the North Sea.
Pollution In 1987 Britain dumped more than 4,700 tonnes of sewage sludge into the North Sea; in 1998 Britain stopped the dumping of sewage sludge (5% of sewage released was untreated). Solid industrial waste dumping ceased after 1995. The North Sea is heavily polluted with oil and toxic metals (such as cadmium) and chemicals (such as tributyl tin and polychlorinated biphenyl), and many fish are deformed or diseased. Fertilizer run-off has been known to cause algal blooms that starve fish of oxygen.
Oil and gas production In 1998 the UK was responsible for 4% of the world's natural gas production and 3.8% of its oil production, most of which derived from North Sea rigs. UK reserves of oil currently stood at around two billion tonnes – as much as was produced in the previous 25 years. Some oil fields, in particular those to the west of the Shetland Islands, have been discovered relatively recently and are at an early stage of their productive life. Recent and future fields are expected to remain productive at least until 2020. 204 offshore fields were in production at the beginning of 1999. 109 of these were producing oil, 79 gas, and 16 condensate. About 30,000 people work offshore, and it is estimated that a further 300,000 jobs in the UK are directly or indirectly supported by the industry.
Rising sea level A gradual lowering of the southeastern British coastline since the Ice Age has meant a gradual rise in the sea level, producing ever-increasing floods. It is believed that the melting of the polar ice cap as a result of rising air temperatures will add to this rise in sea level.
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