Daily scale winter-time sea surface temperature variability and the Iberian Poleward Current in the southern Bay of Biscay from 1981 to 2010

Abstract

The combination of remotely sensed gappy sea surface temperature (SST) images with the missing data filling Data Interpolating EOFs (DINEOF) 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 winter-time surface signal of the Iberian Poleward Current (IPC) 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 variability of the IPC. A physical mechanism involving both atmospheric and oceanic variables is proposed in relation to the variability of the IPC. It jointly takes into account several mechanisms that have separately been related to the variability of the IPC, 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. This mechanism emerges from an atmospheric 500 hPa circulation anomaly that has not a simple relationship with any of the most common North Atlantic teleconnection patterns. It then generates mutually coherent SST and sea level anomaly patterns in the North Atlantic area due to the action of anomalous wind-stress and heat-fluxes, and locally, it also generates the conditions for the mentioned mechanisms in the Bay of Biscay area.