North Sea

The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. 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 long and wide, covering.
It hosts key north European shipping lanes and is a major fishery. The coast is a popular destination for recreation and tourism in bordering countries, and a rich source of energy resources, including wind and wave power.
The North Sea has featured prominently in geopolitical and military affairs, particularly in Northern Europe, from the Middle Ages to the modern era. It was also important globally through the power northern Europeans projected worldwide during much of the Middle Ages and into the modern era. The North Sea was the centre of the Vikings' rise. The Hanseatic League, the Dutch Republic, and Britain all sought to gain command of the North Sea and access to the world's markets and resources. As Germany's only outlet to the ocean, the North Sea was strategically important through both world wars.
The coast has diverse geology and geography. In the north, deep fjords and sheer cliffs mark much of its Norwegian and Scottish coastlines respectively, whereas in the south, the coast consists mainly of sandy beaches, estuaries of long rivers and wide mudflats. Due to the dense population, heavy industrialisation, and intense use of the sea and the area surrounding it, various environmental issues affect the sea's ecosystems. Adverse environmental issuescommonly including overfishing, industrial and agricultural runoff, dredging, and dumping, among others have led to several efforts to prevent degradation and to safeguard long-term economic benefits.

Geography

The North Sea is bounded by the Orkney Islands and east coast of Great Britain 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 is a marginal sea in the Arctic Ocean.
The North Sea 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. A large part of the European drainage basin empties into the North Sea, including water from the Baltic Sea. The largest and most important rivers flowing into the North Sea are the Elbe and the Rhine – Meuse. Around 185 million people live in the catchment area of the rivers discharging 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 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. These great banks and others make the North Sea particularly hazardous to navigate, which has been alleviated by the implementation of satellite navigation systems. The Devil's Hole lies east of Dundee, Scotland. The feature is a series of asymmetrical trenches between long, wide and up to deep.
Other areas which are less deep are Cleaver Bank, Fisher Bank and Noordhinder Bank.

Extent

The International Hydrographic Organization defines the limits of the North Sea as follows:

On the Southwest. A line joining the Phare de Walde and Leathercoat Point. northeast of Dover.
On the Northwest. From Dunnet Head in Scotland to Tor Ness in the Island of Hoy, thence through this island to the Kame of Hoy on to Breck Ness on Mainland through this island to Costa Head and Inga Ness in Westray through Westray, to Bow Head, across to Mull Head and on to Seal Skerry and thence to Horse Island.
On the North. From the North point of the Mainland of the Shetland Islands, across to Graveland Ness in the Island of Yell, through Yell to Gloup Ness and across to Spoo Ness in Unst island, through Unst to Herma Ness, on to the SW point of the Rumblings and to Muckle Flugga all these being included in the North Sea area; thence up the meridian of 0°53' West to the parallel of 61°00' North and eastward along this parallel to the coast of Norway, the whole of Viking Bank is thus included in the North Sea.
On the East. The Western limit of the Skagerrak .

Hydrology

Temperature and salinity

The average temperature is in the summer and in the winter. The average temperatures have been trending higher since 1988, which has been attributed to climate change. Air temperatures in January range on average between and in July between. The winter months see frequent gales and storms.
The salinity averages between 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 inshore.
The North Sea located on the continental shelf has different waves from 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 zero and.
The Kelvin tide of the Atlantic Ocean is a semidiurnal wave that travels northward. Some of the energy from this wave travels through the English Channel into the North Sea. The wave continues to travel northward in the Atlantic Ocean, and once past the northern tip of Great Britain, the Kelvin wave turns east and south and once again enters the North Sea.

Tidal range	Maximum tidal range	Tide-gauge	Geographical and historical features
0.79–1.82	2.39	Lerwick	Shetland Islands
2.01–3.76	4.69	Aberdeen	Mouth of River Dee in Scotland
2.38–4.61	5.65	North Shields	Mouth of Tyne estuary
2.31–6.04	8.20	Kingston upon Hull	Northern side of Humber estuary
1.75–4.33	7.14	Grimsby	Southern side of Humber estuary farther seaward
1.98–6.84	6.90	Skegness	Lincolnshire coast north of the Wash
1.92–6.47	7.26	King's Lynn	Mouth of Great Ouse into the Wash
2.54–7.23		Hunstanton	Eastern edge of the Wash
2.34–3.70	4.47	Harwich	East Anglian coast north of Thames Estuary
4.05–6.62	7.99	London Bridge	Inner end of Thames Estuary
2.38–6.85	6.92	Dunkirk	Dune coast east of the Strait of Dover
2.02–5.53	5.59	Zeebrugge	Dune coast west of Rhine–Meuse–Scheldt delta
3.24–4.96	6.09	Antwerp	Inner end of the southernmost estuary of Rhine–Meuse–Scheldt delta
1.48–1.90	2.35	Rotterdam	Borderline of estuary delta and sedimentation delta of the Rhine
1.10–2.03	2.52	Katwijk	Mouth of the Uitwateringskanaal of the Oude Rijn into the sea
1.15–1.72	2.15	Den Helder	Northeastern end of Holland dune coast west of IJsselmeer
1.67–2.20	2.65	Harlingen	East of IJsselmeer, outlet of IJssel river, the eastern branch of the Rhine
1.80–2.69	3.54	Borkum	Island in front of Ems river estuary
2.96–3.71		Emden	East side of Ems river estuary
2.60–3.76	4.90	Wilhelmshaven	Jade Bight
2.66–4.01	4.74	Bremerhaven	Seaward end of Weser estuary
3.59–4.62		Bremen-Oslebshausen	Bremer Industriehäfen, inner Weser estuary
3.3–4.0		Bremen Weser barrage	Artificial tide limit of river Weser, 4 km upstream of the city centre
2.6–4.0		Bremerhaven 1879	Before start of Weser Correction
0–0.3		Bremen city centre 1879	Before start of Weser Correction
1.45		Bremen city centre 1900	Große Weserbrücke, 5 years after completion of Weser Correction works
2.54–3.48	4.63	Cuxhaven	Seaward end of Elbe estuary
3.4–3.9	4.63	Hamburg St. Pauli	St. Pauli Piers, inner part of Elbe estuary
1.39–2.03	2.74	Westerland	Sylt island, off the Nordfriesland coast
2.8–3.4		Dagebüll	Coast of Wadden Sea in Nordfriesland
1.1–2.1	2.17	Esbjerg	Northern end of Wadden Sea in Denmark
0.5–1.1		Hvide Sande	Danish dune coast, entrance of Ringkøbing Fjord lagoon
0.3–0.5		Thyborøn	Danish dune coast, entrance of Nissum Bredning lagoon, part of Limfjord
0.2–04		Hirtshals	Skagerrak. Hanstholm and Skagen have the same values.
0.14–0.30	0.26	Tregde	Skagerrak, southern end of Norway, east of an amphidromic point
0.25–0.60	0.65	Stavanger	North of that amphidromic point, tidal rhythm irregular
0.64–1.20	1.61	Bergen	Tidal rhythm regular