DATE2018-05-12 12:20:00
AUTHORSM Reale (1,2), S Salon (2), A Crise (2), R Farneti (1), R Mosetti (2), G Sannino (3)
  1. ICTP, Trieste, Italy
  2. OGS, Trieste, Italy
  3. ENEA, Roma, Italy
ABSTRACTThe observed decadal reversal of the upper layer circulation of the northern Ionian has been suggested to be driven either by variation in wind stress curl over the basin or by baroclinic mechanisms acting within or outside the Adriatic-Ionian System. To discriminate among these hypotheses we use a two-phase approach in analyzing different numerical simulation outputs . We firstly assess the relative role of the forcing and the dominant processes in the reversal of the northern Ionian circulation by running a set of numerical experiments (AISexp experiments) simulating the dynamics of Adriatic-Ionian System and characterized by an increasing complexity in the forcing and domain. The second step is based on a multi-model experiment considering advanced hindcast/reanalysis (MedMIT12, NemoMed8 and Copernicus reanalysis) and on the definition of a simplified sea surface height index. In this first case the major outcomes of the numerical experiments are that the wind stress role appears to be marginal in the vorticity/energy budget of the Ionian Sea: it is able to reinforce/weaken the circulation but not to induce changes in sign in the circulation. On the other hand changes in the upper layer circulation of the Ionian Sea take place only in presence of an active boundary in the Ionian Sea, on the Aegean Sea side so that Adriatic, Ionian and Aegean Sea behave like a coupled system. This is confirmed by the second phase analysis where we found in all the simulations considered the existence of a covariant behavior between Ionian Sea and Aegean Sea associated with a mutual zonal exchange of water masses with different salinity characteristics. These two different approaches support the idea that a complete characterization of observed variability in the northern Ionian needs to take into account a fully coupled Adriatic-Ionian-Aegean System and that BiOS-like observations during the period 1987–2008 reflect the switching between the two possible deep water sources of the Eastern Mediterranean , Adriatic and Aegean Sea.