Modeling the nutrient and carbon cycles of the North Atlantic: 2. New production, particle fluxes, CO2 gas exchange, and the role of organic nutrients

The nutrient and carbon cycles in the North Atlantic are studied by combining mapped nutrient station data with the annual mean hydrographic data of Levitus (1982) in the context of an inverse model. New production rates, Corg, CaCO3 and opal fluxes, and CO2 air‐sea gas exchange rates consistent with the nutrient distributions and with the circulation pattern evolving from the Levitus data are calculated. In a first model only the inorganic components phosphate, nitrate, and ΣCO2 are considered in the budgets for the nutrients. Model calculations show that the distributions of the inorganic nutrients are consistent with the Levitus circulation field and that model new production, particle fluxes, and CO2 gas exchange rates are compatible with independent estimates. The influence of dissolved organic nutrients on the oceanic nutrient and carbon cycles has been investigated with a series of models which include traditionally accepted values for the dissolved organic nutrients or recently reported data by Sugimura and Suzuki (1988). The model with traditionally accepted values for dissolved organic nutrients is feasible, and the results differ only slightly from the model with inorganic nutrients only. Models with data from Sugimura and Suzuki (1988) are infeasible. When concentrations of dissolved organic nutrients are derived from the correlation with apparent oxygen utilization (AOU), violations of model constraints are relatively small. Nevertheless, the correlation between dissolved organic nutrients and AOU found by Sugimura and Suzuki (1988) for the northwest Pacific seems not to hold in the North Atlantic because it would imply unreasonably small new production rates. More data for the dissolved organic nutrients must be collected before conclusive answers concerning their role in the oceanic nutrient cycles can be given.