Surface connection between the Ionian Sea and different areas of the Mediterranean derived from drifter data

The surface connection between the Ionian Sea (central Mediterranean Sea) and the surrounding areas is studied by looking at the statistical properties of 1632 near-surface Lagrangian trajectories. The choice of the area is due to the key role in the dynamics of the Mediterranean Sea and to the geographical distribution of data. The Lagrangian drifter data were taken from the OGS Mediterranean drifter database, which gathers drifter data collected in the Mediterranean Sea from various institutions and countries between 1986 and 2016. The database has proved to be sufficiently complete, but the spatial and temporal data coverage are less satisfactory in the case of selection of a specific study area and temporal range. The strategy used in this work aims to limiting the problem of data coverage by choosing many target boxes around the study area, choice based on drifter trajectories, current patterns and areas of interest. The pseudo-eulerian analysis obtained from all trajectories passing through the Ionian Sea show the main dynamic structure present in the central Mediterranean Sea (e.g. Atlantic Ionian Stream, Mid Ionian Jet, etc.).On the other hand, the data density decreases progressively toward the eastern and western sectors of the Mediterranean. The highest connection was observed with the Strait of Sicily, Eastern Ionian and Adriatic Sea, with connection percentages 30%, 25% and 16% respectively. The transit times between the Ionian Sea and these target boxes are about 20-50 days. The Ionian Sea is characterized by phenomena of inversion of the basin surface circulation, from cyclonic to anti-cyclonic, over a ten-year timescale, the so-called Adriatic-Ionian Bimodal Oscillating System (BiOS, e.g. Ga?i? et al., 2010; Ga?i? et al., 2011). An application of the "target box methodology" has been used to describe how the cyclic variability of the dynamic surface currents generates an equally cyclical fluctuation of the connectivity between the Ionian Sea and the surrounding areas during the BiOS phases.