Lagrangian Analysis and Prediction of Coastal and Ocean Dynamics
LAPCOD VII :: Venice 2019 :: 17-21 June 2019
Venice 2019
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Coastal submesoscale structures and variability from drifters and HF radar in the Ligurian Sea (Mediterranean)

Maristella Berta, Lorenzo Corgnati, Marcello G. Magaldi, Annalisa Griffa, Carlo Mantovani, Pierre-Marie Poulain, Paolo Oddo
CNR (Consiglio Nazionale Ricerche) ISMAR
(Abstract received 04/16/2019 for session A)

The presence and variability of coastal submesoscale structures, such as eddies and jets of the order of 1-10 km, is studied using drifters and HF radar data in the coastal Ligurian Sea. The presence of strong convergent areas and jets of a few kilometers are first investigated using drifter data, collected in the framework of the LOGMEC-17 experiment (September 2017). The time evolution of the structures is then studied using surface current velocity data from HF radar over a period of two months in October-November 2018. We focus in particular on the response to the wind during an extreme event occurred at the end of October, that caused extensive damage along the Ligurian coast. The submesoscale structures are characterized in terms of kinematic properties (KPs) such as vorticity and divergence. During the event, the current root mean square (rms) velocity is found to increase of approximately four times during the event, while vorticity and divergence are almost doubled. The deformation of the spatial structures suggests nonlinear interactions with the wind forcing, with local values of divergence greater than the Coriolis parameters f. This indicates significant submesoscale vertical velocity and consequent potential impact on the ecosystem in terms of transport of biological quantities, nutrients and pollutants in the water column.