Operational ROMS in the Bay of Biscay

Luis Ferrer, Manuel González, Adolfo Uriarte, Victor Valencia, Julien Mader, Almudena Fontán

Azti-Tecnalia, Marine Research Division, Gipuzkoa, Spain


The Bay of Biscay, in the Atlantic Ocean, with a total area of approximately 250,000 km2, is limited by the northern Spanish and western French coasts. The hydro-climatic regime in the bay corresponds to that of a mid-latitude temperate zone. The currents in the upper layers of the water column are directly related to the wind fields, being their effects more important than the ones induced by circulation systems of higher scales, which are more relevant at deeper water depths off the continental shelf. Close to the shore, the orientation of the coastline (east-west and north-south along the Spanish and French coasts, respectively) together with the seasonal distribution of the prevailing winds explain (to a large extent) the general drift of the surface water masses in the Bay of Biscay. Hence, the winds blow predominantly from the southwest in autumn and winter, generating marine currents that, on an average, cause predominant eastward and northward drift. The wind regime changes towards the north-northwest during spring, causing currents to move in a southerly direction and towards the west-southwest along the French and Spanish coasts, respectively. The summer situation is similar to that of the spring, although the presence of weak winds of high variability results in a more indeterminate general drift direction of the currents (Lazure, 1997). This work shows the ROMS working in the Bay of Biscay in an operational way. Results show that the accuracy of the input data required by the model play a fundamental role in the prediction of the spatial and temporal hydrodynamic evolution. At the upper layers of the water column, the winds confirm their importance on the current forecast, as is shown by the data recovered by drifting surface buoys. This is relevant for the analysis of specific phenomena such as oil spills drifting on the sea surface waters, fish eggs and larvae dispersion, algal blooms, etc.