A shallow shelf sea that shaped Europe's trade, wars and dikes
The North Sea washes Britain’s east coast and the shores of Norway, Denmark, Germany, the Netherlands, Belgium, and France across more than 970 by 580 kilometres. About 750,000 square kilometres of mostly shallow water hold some 54,000 cubic kilometres—busy with shipping, fisheries, and offshore energy.
Most of the sea sits on the continental shelf at an average depth of about 90 metres. The exception is the Norwegian Trench, 20 to 30 kilometres wide, which follows the Norwegian coast from Oslo to beyond Bergen and plunges to 725 metres. Elsewhere glacial debris builds shoals: the Dogger Bank, a huge moraine only 15 to 30 metres below the surface, became the sea's best fishing ground, while banks such as the Long Forties and Broad Fourteens made navigation treacherous until satellite positioning arrived. The Elbe and the Rhine–Meuse are the largest rivers feeding it, and about 185 million people live in the catchments that drain here.
Water circulates anticlockwise around the edges, entering mainly through the northern opening with a smaller warm inflow via the English Channel. Summer water averages 17 °C and winter 6 °C, and temperatures have risen since 1988. Glaciers carved fjords and cliffs into Norway and Scotland, while the southern shores are low sand, estuaries and mudflats shaped by longshore drift.
Storm surges have long defined life on the southern coast. By 500 BC people raised dwelling mounds above flood level, and around 1200 AD separate ring dikes began to be joined into a continuous line. A surge in 1228 reportedly killed more than 100,000 people, and the Grote Manndrenke of 1362 claimed a similar toll and swallowed the town of Rungholt. The 1953 flood killed over 2,000, and today dikes, dunes and beach flats protect the 27 percent of the Netherlands lying below sea level. Between 8150 and 6000 BCE the Storegga slides off Norway sent a tsunami up to 20 metres high across the sea.
The sea nurtured the Vikings' rise, and the Hanseatic League, the Dutch Republic and Britain each fought for command of it; as Germany's only ocean outlet it mattered in both world wars.
Source: North Sea
