Shiptime: The continental shelf pump: a pilot study in the North Sea.

Bijdrage scheepstijd RV Pelagia 4 cruises in 2001 en 2002 tbv project 810.33.004 uit de Open Competitie. Doel van het onderzoek: The role of coastal seas in the global carbon cycle will be assessed in a pilot study in the North Sea. The hypothesis of a "continental shelf pump" for uptake of CO2 from the atmosphere with subsequent transport to the open ocean will be tested for the North Sea as a nutrient-rich sea with high biological productivity. Interactions of the pools of C,N,P, and O2 will be assessed also to describe the "biological CO2 pump". State of the art, well-calibrated, accurate methods will be used for the first ever quantification of the pools of dissolved inorganic and organic carbon (DIC, DOC) in the North Sea during the four seasons at 90 stations being prescribed by the needs of the ecosystem model ERSEM II. The synoptic, top quality field data set will comprise data of DIC and DOC together with pCO2, pH, hydrography, dissolved oxygen (O2), particulate carbon (POC and PIC) and of pools of nitrogen (NO3, NO2, NH4, , DON, PON), phosphate (PO4), silicate (SiO4) and Chlorophyll a. The results will be evaluated by property-property relations and other methods to determine seasonality of river inputs, of C/N/P/O2 inventories, and of CO2 exchanges with the atmosphere. Upon extension with a C-budget module, the existing ecosystem model ERSEM II, which already well describes nutrient and plankton dynamics in context of hydrography, will be used to simulate the carbon cycle processes including verification against the four seasons field data base. Attention will be given to exchanges in the Kattegat and with the North Atlantic Ocean, and notably the annual air-sea CO2 exchange budget, finally testing the continental shelf pump hypothesis. Scientific objectives: 1. For carbon a completely new field database will be established. The North Sea will be covered during four seasons by an adapted 1° by 1° grid corresponding to 90 stations. 2. The data set will be used to assess the physical and biological processes affecting carbon storage and release. Attention will be given to the interaction between hydrography and the carbon, nitrogen and phosphorus pools, and to transport processes of carbon into and out of the North Sea. Sources and sinks to be taken into account are rivers, the North Atlantic Ocean, the atmosphere, as well as the Baltic Sea. 3. Full descriptions of the carbon cycle are to be implemented into the ERSEM II ecosystem model with an eye to establishing the annual budgets for carbon and related elements N, P and O. Upon verification against the field data the ERSEM II simulations will indicate whether these coastal seas are a net source or sink for atmospheric CO2 and for carbon in general, i.e., the "continental shelf pump" hypothesis will be tested.