The North Sea is a shallow, marginal sea of the North Atlantic Ocean. It sits between the UK, Scandinavia and several countries on the European continent. In the north, it opens up into the Norwegian Sea between the Shetland Islands and Norway, in the south through the English Channel, and it flows east towards the Baltic Sea through Skagerrak and Kattegat straits.
The topography of the North Sea’s coastlines varies enormously. Fjords, inlets, cliffs and rocky islands typify the northern areas in Scotland and Norway, a defining feature of the coastal routes that Hurtigruten sails. In the south, sandy beaches and low-lying tidal flood plains dominate. The salt marshes and wetlands of the Wadden Sea and Frisian Islands, along the Dutch, German and Danish coast, create a unique ecosystem rich in biodiversity that is an important area for bird migration.
Since the Middle Ages, the North Sea has been historically and strategically important for its bordering countries, both for defence and trade. Whoever ruled the North Sea controlled access to its shipping lanes, and the routes to global trade markets. The North Sea was central to the rise of the Vikings as they used their superior sea power to conquer territory along its shores, leaving behind their historical and cultural imprint which can be seen in some places to this day.
After the Viking Age came the Hanseatic period (13th to 17th century), where a league of North German merchant towns grew to dominate the maritime trade of the Baltic Sea and the North Sea. The Dutch Golden Age followed as their navies took control of the North Sea leading to the Anglo-Dutch Wars (1652 and 1673). Between 1700 and 1815, the North Sea saw just 45 years of peace, as nations competed for ownership of this all-important trade channel. Today, the southern part of the North Sea, together with the English Channel, remains one of the world’s busiest waterways.
With a mean depth of less than 100m, the North Sea is relatively shallow. Its deepest point is the 750m Norwegian Trench, and with its shallow depth, tidal patterns and strong storms, its waters are notoriously choppy. A benefit of this churn is that it brings nutrients up from the bottom of the sea to the surface where algae can bloom and thrive -- forming the basis of the North Sea’s food chain and resulting in abundant fish resources.
The North Sea is rich in biodversity for sealife and birdlife. In the northern part of the North Sea and along the Norwegian coast, millions of seabirds such as guillemots, kittiwakes, fulmars and gannets breed on the steep cliffs. In the south, other species such as gulls and terns take advantage of the low-lying sandy shores for breeding. Herring and sandeel attract larger predatory species to the North Sea. The Greenland shark is common in Norwegian waters, and grey and harbour seals can be found along many coastlines. The second largest fish in the world, the basking shark, can be found in the Channel close to the White cliffs of Dover, drawn by the zooplankton.
For centuries, the North Sea has provided a livelihood for fishermen, with its rich stocks of cod, mackerel and herring. However, these fisheries have suffered boom-and-bust periods due to over-fishing and more recently from climate change, as the North Sea has warmed up significantly in the last 50 years. Numbers of the once super-abundant copepod crustacean - the diet of many fish - has significantly declined, leading to a reduction in volumes of commercial fish.