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Ocean Science An interactive open-access journal of the European Geosciences Union

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Ocean Sci., 9, 655-679, 2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
19 Jul 2013
Daily scale wintertime sea surface temperature and IPC-Navidad variability in the southern Bay of Biscay from 1981 to 2010
G. Esnaola1, J. Sáenz2,3, E. Zorita4, A. Fontán1, V. Valencia1, and P. Lazure5 1AZTI-Tecnalia, Marine Research Division, Herrera Kaia Portualdea z/g, 20110 Pasaia, Gipuzkoa, Spain
2Department of Applied Physics II, Fac. of Science and Technology, University of the Basque Country (UPV/EHU), Barrio Sarriena s/n, 48940 Leioa, Spain
3Research Center for Experimental Marine Biology and BioTechnology (PIE-UPV/EHU), Areatza Pasealekua, 48620 Plentzia, Spain
4Institute for Coastal Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Straß e 1, 21502 Geesthacht, Germany
5Department DYNECO, IFREMER, Centre de Brest, BP 70, 29280 Plouzané, France
Abstract. The combination of remotely sensed gappy Sea surface temperature (SST) images with the missing data filling DINEOF (data interpolating empirical orthogonal functions) technique, followed by a principal component analysis of the reconstructed data, has been used to identify the time evolution and the daily scale variability of the wintertime surface signal of the Iberian Poleward Current (IPC), or Navidad, during the 1981–2010 period. An exhaustive comparison with the existing bibliography, and the vertical temperature and salinity profiles related to its extremes over the Bay of Biscay area, show that the obtained time series accurately reflect the IPC-Navidad variability. Once a time series for the evolution of the SST signal of the current over the last decades is well established, this time series is used to propose a physical mechanism in relation to the variability of the IPC-Navidad, involving both atmospheric and oceanic variables. According to the proposed mechanism, an atmospheric circulation anomaly observed in both the 500 hPa and the surface levels generates atmospheric surface level pressure, wind-stress and heat-flux anomalies. In turn, those surface level atmospheric anomalies induce mutually coherent SST and sea level anomalies over the North Atlantic area, and locally, in the Bay of Biscay area. These anomalies, both locally over the Bay of Biscay area and over the North Atlantic, are in agreement with several mechanisms that have separately been related to the variability of the IPC-Navidad, i.e. the south-westerly winds, the joint effect of baroclinicity and relief (JEBAR) effect, the topographic β effect and a weakened North Atlantic gyre.

Citation: Esnaola, G., Sáenz, J., Zorita, E., Fontán, A., Valencia, V., and Lazure, P.: Daily scale wintertime sea surface temperature and IPC-Navidad variability in the southern Bay of Biscay from 1981 to 2010, Ocean Sci., 9, 655-679, doi:10.5194/os-9-655-2013, 2013.
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