Editing North Sea (section)

== Hydrology and climate ==

Most Atlantic water enters through the wide northern opening between Scotland and Norway. A smaller inflow passes through the English Channel. Water generally circulates anticlockwise around the basin before leaving along the Norwegian coast through the Norwegian Trench. Lower-salinity water from the Baltic Sea joins this movement through the Kattegat and Skagerrak.

Salinity in the open North Sea is usually between 34 and 35 parts per thousand. It decreases near large river mouths and within the Norwegian Coastal Current. The shallow southern basin is mixed by tides and wind through most of the year. Deeper central and northern waters can separate into a warmer surface layer and a colder bottom layer during spring and summer.

The tides are mainly semidiurnal, producing two high tides and two low tides each day. Tidal range is relatively small in parts of the northern basin but can exceed six metres in southern estuaries. Strong currents move large quantities of sand and maintain channels through shallow coastal waters.

The surrounding region has a temperate maritime climate. Winters bring frequent low-pressure systems and strong westerly winds. Storms can force water into the shallow southern basin, where the narrowing coastline raises water levels further. The low coasts of eastern England and mainland Europe therefore depend on dunes, dikes, movable barriers, and managed floodplains for protection.