North Sea - Environment

The North Sea is influenced by the Atlantic Ocean, mainly by input from the north where the Atlantic current flows north along the edge of the continental shelf, but also, to a lesser extent, from the south via the English Channel (Figure 2). Although a number of classifications for the North Sea have been developed, the dominant physical division is between the north and the south (Figure 3). The northern part is comparatively deep, subject to strong oceanic influences, and characterised by seasonal stratification of the water column, whereby a thermocline develops resulting in a mixed layer depth of around 40 m during May and June. The southern North Sea is shallower (20-50 m) and remains mixed for most of the year, only developing a thermocline over deeper regions and where there are significant freshwater inputs such as from the River Thames (ICONA 1992). The southern region is influenced by inflowing waters from the English Channel, which generate strong tidal currents and an increased sediment load. The seafloor consists of mostly mixed sediments comprised of mud, sand, gravel and rock (Figure 4). In the north the areas close to the Scottish and Norwegian coasts are rocky, with mud predominant in the other northerly areas. Coarser sands are dominant in the shallow tidally active south.