Vertical pathways associated with a submesoscale density front in the Balearic Sea

The CALYPSO research program, funded by the Office of Naval Research, aims to understand the coherent pathways from the surface ocean to the interior. In February and March 2022, the CALYPSO campaign surveyed the upper layers of the Balearic Sea (Western Mediterranean), providing high-resolution observations of mesoscale and submesoscale structures. This included submesoscale density fronts, stretching regions and small coherent eddies. In this work, we analyze the formation, evolution, and impact of these submesoscale structures in the development of vertical velocities and in the determination of three-dimensional pathways from the surface to the ocean interior. We combine multi-platform in-situ observations with high-resolution numerical simulations both in free-run and data-assimilative modes. In particular, the WMOP reanalysis  assimilates remote sensing observations of temperature and sea level anomaly as well as vertical profiles of temperature and salinity from floats, underway CTD and gliders obtained during the CALYPSO campaign. The simulations are shown to realistically reproduce the main characteristics of the Balearic front and some of the associated submesoscale patterns, providing an appropriate tool to analyze the processes responsible for vertical velocities development. Particle tracking analyses indicate pathways for vertical exchange of water between the surface and the ocean interior in the frontal region. Finally, the process of frontogenesis and the submesoscale structures play an important role in the development of the vertical velocities and the energy transfers.