The North Sea and Skagerrak can be divided into two main parts. The northern part is close to the "Norskerenna", a deep ocean trench 800 metres deep. The southern part is bordered to Great Britain, Denmark, Germany and the Netherlands. The average depht is 50 metres. The temperature rises southwards throughout the Norwegian Sea and towards the North Sea. This makes the North Sea a temperate area.
The Nordic Seas are strongly affected by the inflow of warm and salty Atlantic water from the south. This warm Atlantic water origines from the Gulf of Mexico and is transported with the Gulf Stream through the North Atlantic and into the Nordic Seas entering inbetween Shetland and Iceland.
The Norwegian Atlantic current then ramifes into the North Sea, The Norwegian Sea, The Barents Sea and all the way up to the North Pole Sea. Thanks to this warm current Norway enjoys a mild climate and richer fish resources than any other place this far north.