Rossby waves driven by the Mid Mediterranean Jet impact the Eastern Mediterranean mesoscale dynamics

The most prominent and persistent feature of the eastern Mediterranean Levantine Basin (LB) is the warm anticyclonic Cyprus Eddy (CE) located above the Eratosthenes Seamount (ESM). This eddy periodically couples with two smaller cyclonic and anticyclonic eddies, the South Shikmona Eddy (SSE) and North Shikmona Eddy (NSE), which form downstream. The reason for the zonal drift of the CE center and the formation mechanism of the CE, SSE and NSE is largely debated today, yet the upwelling and biological productivity of the LB can be strongly impacted by the local dynamics. Using a variety of research methods-theory, models, laboratory and field experiments-we demonstrate that the CE is an anticyclonic Taylor column generated by the eastward Mid Mediterranean Jet (MMJ) impinging over the ESM. When the center of the CE is west of 32.7° E, a Rossby wave with embedded cyclonic and anticyclonic vortices corresponding to the SSE and NSE, respectively, forms downstream. The position of the CE center reveals to be dependent on the intensity of the MMJ and thus on the cyclonic/anticyclonic mode of the North Ionian Gyre. Our results highlight the key role the central Mediterranean Sea plays on LB, and can be used to predict the Easter Mediterranean Sea mesoscale dynamics up to about three years in advance. They also show how Rossby waves can trigger the transport of nutrient-rich coastal waters offshore, a mechanism that is of paramount importance for the oligotrophic environment of the LB. The coherent results from our multi-approach research underscore the uniqueness and reliability of our findings.