The sense of rotation of the sub-basin-wide upper circulation in the Northern Ionian Sea (Northern Ionian Gyre) is a possible driver for deviating fresh surface Atlantic waters on their way toward the Cretan Passage to the east and toward the Adriatic Sea to the north. The reversals of this circulation on a decadal time scale (named BiOS mechanism) influence therefore the salt content of the adjacent basins, the Adriatic Sea, and Levantine basin. The salt content in turn, influences the density of the intermediate and deep waters.
The BiOS mechanism acts out-of-phase in the Adriatic and in the Levantine basin : when the Northern Ionian Gyre is anticyclonic, the flow of the Atlantic Waters towards the Levantine is deviated northward, and mixes with adjacent waters. So, it dilutes more the upper Adriatic Waters, and less the Levantine basin. When the Northern Ionian Gyre is cyclonic, the Atlantic Waters flow directly eastward toward the Cretan Passage and dilutes more the Levantine basin and less the Adriatic basin. At the same time, the Levantine and Cretan Intermediate Waters flow westward in the intermediate layer.
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The physical modeling of the inversions of the Northern Ionian Gyre circulation in an idealized Adriatic-Ionian/Eastern Mediterranean circulation system at the Coriolis Rotating Platform is aimed at verifying the assumption that internal processes are crucial in driving the mechanism for the inversion of circulation of the Northern Ionian Sea, rather than the wind. In addition, the role of the turbulent eddy field in possible enforcement of the mean flow (Mid Mediterranean Jet) will be addressed and tested for the negative viscosity effect.
The experiments include measurements of the the initial dynamics of the gravity current (e.g. the Adriatic and Aegean sources of deep and intermediate waters, respectively) using Acoustic Doppler Velocimetry profilers and Conductivity probes along with measurements of the entire tank at several horizontal sections using a PIV measurement technique for the velocities and conductivity probes for the density evolution to capture the BiOS mechanism at larger time scales (>60 rotation periods).
Project Leader :
Miroslav GACIC - Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, Trieste Italia
Member :
- Angelo RUBINO - Università Ca’ Foscari Venezia, Italia
- Ricardo VIANA BARRETO - Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Italia
- Eletta NEGRETTI - LEGI, France
European project Hydralab+
