| Summary: | There is a wide consensus among climatologist and oceanographers that the climate system has undergone rapid changes during the last decades of the 20th century and the beginning of the 21st. The most remarkable variation is the increase in temperature both in oceans and atmosphere. Ocean plays a key role to mitigate global warming since it absorbs the vast majority of the heat gained by the Earth. So, small changes in ocean`s properties can lead to unforeseeable consequences. Numerous studies showed that these variations are highly dependent on temporal and spatial scales, in such a way that changes are more marked at regional scale. The Bay of Biscay is a semi-enclosed sea located in the North Atlantic Ocean, off the north coast of Spain and the west coast of France. Its bathymetry is characterized by a wide continental shelf along the French coast, especially in its northern part (more than 100 km), and a narrower one along the Spanish coast. The Biscay Abyssal plain, with depths around 4000 m, occupies the central part of the bay. This area is influenced by the general circulation in the North Atlantic following an anticyclonic gyre. In the rest of the bay, bathymetric conditions together with local forcings (wind pattern, river discharges…) give as result a circulation pattern that changes depending on the season. So, the scientific interest of the Bay of Biscay resides in that it is a semi-enclosed sea representing a complex merger between ocean features and local processes that show their influence at different temporal and spatial scales. The main aim of this thesis is to analyze oceanic physical changes occurred in the Bay of Biscay during the last decades. To carry out this purpose the newest databases were selected in order to ensure appropriate spatial and temporal resolutions. Thus, insitu databases (Argo floats), satellite data (MODIS sensor) and reanalysis databases (SODA, OISST1/4 and CFSR) were combined to analyze changes in salinity and temperature, as well as, variations in other physical ...
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