The Barents Sea is a shallow continental shelf sea. Generally, the physical conditions are determined by three main water masses: Coastal Water, (North) Atlantic Water, and Arctic Water. These three water masses are linked to three different current systems: the Norwegian Coastal Current, the Atlantic Current,and the Arctic Current. This paper gives a brief description of these current systems and their related water masses. Vertical stratification of the different water masses is emphasised since this is important for primary production.

Climatic variability is determined by the properties and the activity of the inflowing Atlantic Water. Current activity variations may be explained by external forcing, but may also be a result of processes taking place in the Barents Sea itself. The climatic fluctuations have a significant effect on the ice conditions, which in turn influence the biological production in the northern Barents Sea.