Internal wave energetics and interactions with mesoscale structures in the Sicily Channel area

Abstract

The Sicily Channel plays a crucial role in the general circulation of the Mediterranean Sea. However, the internal wave dynamics is still sparsely characterized in this area which is a hotspot for internal tides. Here, we benefit from a high-resolution model of the Mediterranean Sea with and without tidal forcings to study the synoptic internal wave dynamics in the Sicily Channel area as well as their interactions with the (sub)mesoscale field. We found strong semi-diurnal internal tide generation in the Sicily Channel and the Messina Strait. Diurnal internal tides are generated in the Sicily Channel, Pelagie Islands and the Malta Plateau, and are bottom-trapped because of their sub-inertial frequency. In contrast near-inertial waves are mainly generated in winter in the Tyrrhenian Sea and the northern Ionian Sea. We show that the geometry of the Sicily Channel prevents near-inertial wave to propagate through it. Near-inertial waves are trapped in anticyclonic eddies. In summer, we show that diurnal-inertial internal waves generated by the intense thermal breeze near coastal areas are trapped in anticyclonic eddies with an effective inertial frequency close to the diurnal frequency even far from 30°N of latitude. Implications for turbulence and mixing are discussed. We present indirect evidence of an enhanced forward energy cascade in the presence of tidal motions. Future work will focus on the impact of tidal motions on the energy cascade using a nested non-hydrostatic numerical simulation.