Cordeiro Pires, A., Nolasco, R. and Dubert, J., 2013. On the origin of summer upwelled waters in Western Iberian Peninsula

As in most eastern boundary systems, on the Western Iberian Margin there is coastal upwelling during summer due to the alongshore northerly winds and the consequent offshore displacement of surface waters. This work addresses the origin of these upwelled waters. Using a regional ocean model, a climatological configuration and a lagrangian particle module that is run backward in time, we trace the trajectory of particles arriving at four coastal areas, delimited by the 200-m isobath, approximately, and at three depths: 20 m, 40 m and 60 m. Each point is traced backward for one month, with arrival dates of June 30, July 30 and August 30, the typical upwelling months. We find out where the particles were on June 1, July 1 and August 1, respectively, how deep they have reached and what distance they have traveled. In general, the points of origin were shallower (in the upper 100 m) for the particles that traveled the greatest distances (up to 500 km). These particles come mostly from the north and trace alongshore pathways at 20–40 km from the coast, i.e., within isobaths 100–200 m, the preferential path of the upwelling-associated equatorward jet. Conversely, particles that originate from deeper levels, down to 600 m, come from shorter distances, approximately 100 km. Some particles originate to the west of their point of upwelling, giving evidence of being dependent on meandering and other mesoscale features, such as offshore eddies and upwelling filaments.