Mesoscale circulation in the surface layer off the southern and western Sardinia Island in 2000–2002

Abstract

Abstract Five oceanographic cruises were organized in the Sardinian Sea and Channel in May 2000, March 2001, September 2001, May 2002, and November 2002 to study the characterization of the water masses, Atlantic Water (AW) and Winter Intermediate Water (WIW), and their mesoscale variability. In the Sardinian Channel, an Algerian anticyclonic Eddy (AE) was observed in May 2000, along the Tunisian coast. This induced a greater minimum salinity in a wider and deeper layer than in November 2002, when no AE was observed. Some WIW was observed below it; nevertheless, no link could be established between AEs and WIW occurrences. In the Sardinian Sea, two AEs were observed during spring 2000, and a further two during spring 2002. One AE strongly influenced shelf circulation, in contrast to the other three that were off the continental slope. In the same area, during the end of September 2001, a vertical salinity inversion occurred in the first 30–50 m of depth over the whole sampling field, and a W–NW wind induced a coastal upwelling over the western Sardinian coast (south of 41° N). This upwelling increased the salinity from ∼20 to 30 m below the surface to the surface and, thereby led to a lower salinity close to the coast than offshore. This was in contrast to a classical upwelling. Consequently, in the Sardinian Sea, the general circulation, mainly driven by AEs, can meet the coastal wind-driven circulation. Keywords: SardiniaAWWIWAnticyclonic eddymesoscale Acknowledgements The authors would especially like to thank all the people who sailed on the R/V Urania for their great contribution during the five MedGOOS cruises, the German Aerospace Centre DLR (http://eoweb.dlr.de) for the infrared images and Elena Mauri and Pierre-Marie Poulain from the Remote Sensing Group (SIRE) of OGS (Trieste, Italy) for providing the processed satellite images. This work was financially supported by: the Italian MIUR in the frame of the project SIMBIOS (SIstema per lo studio del Mare con Boa Integrata OffShore—Operative Programme of the Marine Environment Plan, Cluster C10, Project n. 13—D.n. 778.RIC) and the EU Marie Curie Host Fellowship of the Human Potential programme, project ODASS (contract n. HPMD-CT-2001-00075). This work was developed in the framework of the EuroGOOS and MedGOOS strategies and in synergy with the EU project MAMA (contract no. EVR1-CT-2001-20010 MAMA).