Abstract

The circulation of the Eastern Mediterranean Sea is characterized by numerous recurrent or permanent anticyclonic structures, which modulate the pathway of the main currents and the exchange of the water masses in the basin. This work aims to describe the main circulation structures and thermohaline properties of the Eastern Mediterranean with particular focus on two anticyclones, the Pelops and the Cyprus gyres, using in-situ (drifters and Argo floats) and satellite (altimetry) data. The Pelops gyre is involved in the circulation and exchange of Levantine origin surface and intermediate waters and in their flow toward the Ionian and the Adriatic Sea. The Cyprus Gyre presents a marked interannual variability related to the presence/absence of waters of Atlantic origin in its interior. These anticyclones are characterized by double diffusive instability and winter mixing phenomena driven by salty surface waters of Levantine origin. Conditions for the salt finger regime occur steadily and dominantly within the Eastern Mediterranean anticyclones. The winter mixing is usually observed in December–January, characterized by instability conditions in the water column, a gradual deepening of the mixed layer depth and the consequent downward doming of the isohalines. The mixing generally involves the first 200 m of the water column (but occasionally can affect also the intermediate layer) forming a water mass with well-defined thermohaline characteristics. Conditions for salt fingers also occur during mixing events in the layer below the mixed layer.

Highlights

  • The surface circulation of the Eastern Mediterranean Sea (EMS) is characterized by a cyclonic coastal circuit and by numerous multi-scale structures that interact in the interior of the basin (Figure 1)

  • The main pathways of the Mid-Ionian Jet (MIJ) and the Mid-Mediterranean Jet (MMJ) divide the EMS in two regions (Figure 1B): the southern part marked by anticyclonic features and the northern part mainly characterized by cyclones (Menna et al, 2020) and quasi-decadal reversals of the surface circulation in the northern Ionian, interpreted in terms of internal processes (Gacicet al., 2010, 2011, 2014; the AdriaticIonian Bimodal Oscillation System thoroughly described in Civitarese et al, 2010; Menna et al, 2019b; Rubino et al, 2020)

  • The AW flows into the Ionian Sea through the Sicily Channel and bifurcates in two branches: the first branch transports the AW toward the north of the Ionian and southern Adriatic seas; the second branch transports the AW toward the Levantine Basin following the cyclonic circuit of coastal currents (LEC, CC, and AMC; acronyms are defined in the caption of Figure 1B) and the MIJ –MMJ path in the interior of the basin (Robinson et al, 2001; Hamad et al, 2005, 2006; Millot and Taupier-Letage, 2005; Schroeder et al, 2012)

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Summary

Introduction

The surface circulation of the Eastern Mediterranean Sea (EMS) is characterized by a cyclonic coastal circuit and by numerous multi-scale structures that interact in the interior of the basin (Figure 1). The AW flows into the Ionian Sea through the Sicily Channel and bifurcates in two branches: the first branch transports the AW toward the north of the Ionian and southern Adriatic seas; the second branch transports the AW toward the Levantine Basin following the cyclonic circuit of coastal currents (LEC, CC, and AMC; acronyms are defined in the caption of Figure 1B) and the MIJ –MMJ path in the interior of the basin (Robinson et al, 2001; Hamad et al, 2005, 2006; Millot and Taupier-Letage, 2005; Schroeder et al, 2012). It can eventually interact with the sub-basin scale and mesoscale structures located along its path (Millot and Taupier-Letage, 2005)

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