Physical processes governing water circulation in the southeastern limit of the Bay of Biscay

• Main Author: Gómez, Almudena Fontán
• Format: Thesis
• Language: English
• Published: University of Southampton 2008
• Subjects: North Atlantic
• Online Access: https://eprints.soton.ac.uk/466598/; https://eprints.soton.ac.uk/466598/1/1228035.pdf

The Basque coast and continental shelf, southeastern Bay of Biscay, can be characterised as being more influenced by land climate, than typical 'open sea' areas. The influence of coastal processes and the presence of irregular topography, appear to complicate greatly the water circulation patterns. The surface water circulation is governed by wind forcing, with tidal and density currents being weak. However, there is a lack of knowledge on the marine currents and on the main time-scales involved in circulation, within the lower water column. The main purposes of this investigation are to identify major physical processes, controlling the spatial and temporal variability in the circulation; and to investigate difference in the controlling processes, throughout the water column. The meteorological conditions differ between the coastal and continental shelf waters. The prevailing wind pattern over the Basque coast is representative of the complex (coastal) wind variability. In contrast, over the Basque continental shelf, the wind regime is influenced less by land climate, responding to the seasonal synoptic regime over the mid- latitudes of the eastern North Atlantic Ocean. The breezes are more pronounced at the coastal waters, than over the continental shelf. Indeed, they introduce harmonics of the diurnal wind over the Basque coastal area. Their influence decreases with increasing distance offshore, but they can be detected even at a distance of 200 km from the coast. This investigation confirms that the main contribution to the wind-induced flow comes from synoptic variability, in the lower water circulation. However, the air-sea interaction patterns are more complex within the surface coastal waters, with wind-driven flows being affected over a broad set of meteorological frequencies: breezes; inertial motions; and synoptic, intra-seasonal and seasonal variability. The meteorological forcing frequencies cannot be determined for the surface continental shelf waters, in relation to an absence of appropriate ...