Chemical characterisation and modelling of water masses in the Northeast Atlantic

We develop a simple model to provide information about the thermohaline and biological control of nutrients and inorganic carbon in the Northeast Atla ntic (39-48 degrees N, 11-27 degrees W). Using data collected during the Vi valdi survey (Charles Darwin cruise 58) in May, 1991 together with publishe d thermohaline characteristics for the source waters of the Northeast Atlan tic, we have deduced triangular mixing percentages for every sample collect ed during the Vivaldi survey. Subsequently, we devised an inverse method co rrelated to the mixing percentages to model nutrient, oxygen and inorganic carbon concentrations. This enables us to explain more than 95% of the nutr ient variability on the basis of correlation with thermohaline properties. The difference between 'real' nutrient and 'modelled' nutrient represents, in part, the biological activity not correlated to the thermohaline propert ies. From the modelled nutrient it is possible to gain information about pr eformed nutrient and an idea of the biological aging undergone by water mas ses. There is a covariance between oxygen consumption and nutrient and inor ganic carbon anomalies which is related to areas of greater remineralizatio n and ventilation. Such areas have been identified. The subsequent applicat ion of our model to TTO data explained about 90% of the nutrient variabilit y. (C) 1998 Elsevier Science Ltd. All rights reserved.