Hydrology of the seas around the Sardinia, western Mediterranean

Abstract. The presence and interannual variability of water masses on the continental shelf surrounding the island of Sardinia are described from three multidisciplinary cruises carried out in September 2019, late August 2020 and September 2021 in the framework of the IDMAR project. A multiparametric probe acquired CTD data along vertical profiles at a total of 166 casts located from the near-shore to the continental slope, between the surface and 300 m depth. The analyses of these observations are for the first time identifying the water mass phenomenology on the Sardinia shelf characterized by the presence of the Atlantic Water at the surface. It shows an unusually low salinity < 37.0 at 35 m on the south-western approaches, detected during the cruises in 2019 and 2021, and driven by the Algerian eddies. On the southern and eastern shelf, the presence of the Atlantic Water is marked by a salinity of about 38.0, and the water column is affected by the temporal and spatial variability of the South East Sardinia Gyre. These observations are opening new aspects to understand the long-term evolution of the hydrology around Sardinia in the context of the general circulation of the Western Mediterranean basin.