Carbon and nutrient mixed layer dynamics in the Norwegian Sea

A coupled carbon-ecosystem model is compared to recent data from Ocean Weather Station M (66 degrees N, 02 degrees E) and used as a tool to investigate nutrient and carbon processes within the Norwegian Sea. Nitrate is consumed by phytoplankton in the surface layers over the summer; however the data show that silicate does not become rapidly limiting for diatoms, in contrast to the model prediction and in contrast to data from other temperate locations. The model estimates atmosphere-ocean CO2 flux to be 37 g C m(-2) yr(-1). The seasonal cycle of the carbonate system at OWS M resembles the cycles suggested by data from other high-latitude ocean locations. The seasonal cycles of calcite saturation state and [CO32-] are similar in the model and in data at OWS M: values range from similar to 3 and similar to 120 mu mol kg(-1) respectively in winter, to similar to 4 and similar to 170 mu mol kg(-1) respectively in summer. The model and data provide further evidence (supporting previous modelling work) that the summer is a time of high saturation state within the annual cycle at high-latitude locations. This is also the time of year that coccolithophore blooms occur at high latitudes.