Modelling the primary production in the North Sea using a coupled three-dimensional physical-chemical-biological ocean model

A coupled three-dimensional physical-chemical-biological model system has been implemented, and applied to study mass and volume transports and primary production throughout the North Sea. The model was run twice for the year 1985 with specified (for the North Sea Task Force) time series of riverine and atmospheric inputs of nutrients, and also with these nutrient inputs reduced by 40 and 50%, respectively. In particular, the evolution of the chemical and biological variables in the two situations was studied. The model output agreed quite well with the general quantitative and qualitative knowledge of the total yearly production. The intercomparison with some salinity profiles also indicated that the model handles the large-scale circulation and vertical mixing fairly well. Estimates for the transport of excess nutrients to Skagerrak and Kattegat in the highly pulsating Jutland coastal current are given. The estimates demonstrate the need for such models for calculating transport of matter from one area to another. Significant reductions in both primary production and transport of matter were seen from comparisons between the two runs.