Abstract:

The East Mediterranean Sea (EMS) circulation variability has previously been characterized as dominated by transient and recurrent mesoscale eddies. We develop nested high resolution EMS numerical simulations to study the circulation pattern and dynamics, particularly for the yet unexplored EMS submesoscale circulation. The EMS cyclonic boundary current is identified as a principle element of the EMS circulation. It generates and advects eddy chains downstream, and sheds mesoscale eddies at several boundary and island wake locations, as well as submesoscale mixed layer spirals and deep submesoscale coherent vortices. During the seasonal fall to winter mixed layer deepening, energetic submesoscale (O(10 km)) eddies, fronts, and filaments emerge, characterized by O(1) Rossby numbers. Mooring data confirms the EMS winter energization of motions with submesoscale times scales. The model-based seasonal submesoscale energization is associated with a k^-2 kinetic energy (KE) wavenumber (k) spectral slope, shallower than the quasigeostrophic-like k^-3 slope diagnosed at summer, and indicative of local control of material dispersion. We diagnose a seasonal inverse (forward) KE cascade above (below) 30 km scales due to rotational (divergent) motions, and show that these commence after completion of the fall submesosacle energization. Additionally, the mooring data and model solutions show intense internal gravity waves (IGWs) activity, dominated by near-inertial waves. Beneath the pycnocline, Helmholtz decomposition demonstrates that the circulation variability is dominated by IGWs, and the associated model KE spectrum also exhibits k^-2 slope. These rich circulation components coexist in the semi-enclosed and topographically-complex EMS, providing ideal environments for studying multi-scale interactions.