Coupling between the Iberian basin — scale circulation and the Portugal boundary current system: a chemical study

The role played by the Portugal Current System in the ventilation of the different modes of Eastern North Atlantic Central Water (ENACW) is evaluated with data from a series of cruises carried out along the western coast of the Iberian Peninsula. Results show the Portugal Current, located west of 10.3°W, conveying fresh modes of recently ventilated ENACW of subpolar origin to the south. Within 70 km of the slope, the Portugal Coastal Countercurrent transports northwards low oxygen/high nutrient ENACW of subtropical origin. Downstream ventilation of ENACW of subtropical origin occurs by mixing or entrainment with offshore ventilated ENACW. We point to mesoscale eddies as the main mechanism for this downstream indirect ventilation, which reconciles opposing views from direct current measurements and hydrographic studies.