A subtropical water intrusion spring-event in the shelf-slope of the south-western Bay of Biscay after strong wind-forcing pulses

Abstract

Two consecutive multidisciplinary surveys, covering the north and north-western part of the Iberian shelf and slope during spring 2000, showed a dramatic change in the oceanographic conditions as a result of a southern water intrusion that replaced shelf and slope waters down to 300 m depth. The intrusion covered an alongshore distance of ∼400 km from the north of Cape Finisterre to the centre of the Cantabrian Sea, and was developed in less than a month between the two occupations of the same area. The analysis of surface currents from several buoys moored over the slope allow us to associate the emerging oceanographic configuration after the event with a strong and well-defined slope current, although during winter 1999–2000 the entrance of the Iberian Poleward Current (IPC) in the Bay of Biscay was very weak. The rapid development of the intrusion is discussed in relation with the unusual strong wind forcing pulse that occurred between the cruises. Our results highlight the importance of variability scales below seasonal (event-scale) in the Iberian margin.