Different remote sensing data were combined to characterise a winter anticyclonic eddy in the southeastern Bay of Biscay and to infer its effects on cross-shelf exchanges, in a period when typical along shelf-slope currents depict a cyclonic pattern. While the joint analysis of available satellite data (infrared, visible and altimetry) permitted the characterisation and tracking of the anticyclone properties and path, data from a coastal high-frequency radar system enabled a quantitative analysis of the surface cross-shelf transports associated with this anticyclone. The warm core anticyclone had a diameter of around 50km, maximum azimuthal velocities near 50cms−1 and a relative vorticity of up to −0.45f. The eddy generation occurred after the relaxation of a cyclonic wind-driven current regime over the shelf-slope; then, the eddy remained stationary for several weeks until it started to drift northwards along the shelf break. The surface signature of this eddy was observed by means of high-frequency radar data for 20 consecutive days, providing a unique opportunity to characterise and quantify, from a Lagrangian perspective, the associated transport and its effect on the Chl-a surface distribution. We observed the presence of mesoscale structures with similar characteristics in the area during different winters within the period 2011–2014. Our results suggest that the eddy-induced recurrent cross-shelf export is an effective mechanism for the expansion of coastal productive waters into the adjacent oligotrophic ocean basin.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This research has received funding from the European Union's Horizon 2020 - Research and Innovation Framework Programme under grant agreement no. 654410. The work of A. Rubio, J. Mader and L. Ferrer was partially supported by the LIFE-LEMA project (LIFE15 ENV/ES/000252) and the Directorate of Emergency Attention and Meteorology of the Basque Government. The research has also been undertaken with the financial support of the Spanish Ministry of Economy and Competitiveness (National Plan for Scientific and Technical Research and Innovation), under projects CTM2013-45423-R and CTM2015-66225-C2-2-P, and the Department of Environment, Regional Planning, Agriculture and Fisheries of the Basque Government (Marco Programme). The along-track altimetry data used in this study were developed, validated and distributed by CTOH/LEGOS, and the geostrophic current fields from altimetry were provided by SSALTO/DUACS (distributed by Aviso, with support from CNES, http://www.aviso.oceanobs.com/duacs/). The SST and Level 2 Chl-a images were produced and distributed by the NERC Earth Observation Data Acquisition and Analysis Service (NEODAAS, http://www.neodaas.ac.uk/data). While, the Level 4 Chl-a images were obtained from COPERNICUS (http://marine.copernicus.eu/). I. Hernández-Carrasco acknowledges the Juan de la Cierva contract funded by the Spanish Government. This paper is contribution no. 832 of AZTI-Marine Research.