Pascale Bouruet-Aubertot (Sorbonne université, France); Yannis Cuypers (Sorbonne université, France); Anne Petrenko (Mediterranean Institute of Oceanography, France); Léo Berline (Mediterranean Institute of Oceanography, France); Anthony Bosse (Mediterranean Institute of Oceanography, France); Robin Rolland (Sorbonne université, France); Louise Rousselet (Sorbonne université, France); Ananda Pascual (IMEDEA, Spain); Francesco D'Ovidio (Sorbonne université, France); Andrea Doglioli (Mediterranean Institute of Oceanography, France)

The considerable refinement of SWOT measurements compared to classical altimetry, extending the spatial resolution to the finescale range (including meso and submesoscales 1-100km) has raised the question of the contribution of ageostrophic motions to the SSH signature. These fine-scales which include frontal structures, vortices and filaments are conducive of various instabilities feeding the direct energy cascade to small-scale turbulence, but also a reverse cascade to large-scale turbulence. The question of the transition scale between direct and reverse cascades is fundamental as a virtual boundary between “balanced” and “unbalanced” movements. This transition scale is highly dependent on fine-scale dynamics and the eddy kinetic energy level. In addition, the interaction of sub-mesoscale structures with internal waves acts as a catalyst for the energy cascade, whether internal tidal waves or wind-generated near-inertial frequency waves.
Our study area is that of the BIOSWOT-MED cruise, near the North Balearic front. The dynamics, characterized by a moderate eddy kinetic energy level and an insignificant tidal signal. These features make it a specific case study for characterizing wind generated near inertial waves and vorticity structures interactions and how they impact the transition scale and reinforce the energy cascade. The analysis is based upon vertical section of currents (acoustic Dopler current profiler) and density measurements (Moving Vessel Profiler). The energy partition between internal waves (IW) and quasi-geostrophic (QG) motions in 2D wavenumber space is inferred from two methods : the Helmoltz decomposition and a Burger decomposition (Vladoiu et al, 2024). The energy partition between QG motions and IW is contrasted and depends upon the wind forcing events and the sign of the background vorticity field. The largest IW total energy is observed along vertical section crossing anticyclonic structures which is consistent with the inertial chimneys evidenced by Rolland et al (2025). Implications regarding the interpretation of SWOT measurements are under present investigation and will be discussed.