A Turbulence Survey in the Gulf of Naples, Mediterranean Sea, during the Seasonal Destratification

The seasonality of the vertical mixing at coastal sites is not well characterized yet. Here, a time series of the dissipation rate of turbulent kinetic energy (ε) was obtained from weekly morning microstructure observations covering the destratification period (July 2015, February 2016) at a coastal site in the western Mediterranean Sea, influenced by freshwater runoffs. Estimated with bulk parameters from the public re-analyzed dataset ERA5, the Ekman layer, and the convective penetration depth scale with the mixed layer depth (MLD) with a good agreement. Below the MLD, peaks of ε are observed in the baroclinic layers that progressively overlap with the bottom layer, where repeated near-bottom turbidity peaks provide evidence of sediment resuspension, suggesting energetic processes within the bottom boundary layer. In the subsurface, moderate values ( to) are observed, following a Burr type XII distribution. Significant correlation with ε at MLD is obtained with a model combining the effects of wind, wind–wave, and convection, highlighting a calm sea bias in our data, plus a sunrise bias when morning buoyancy fluxes are stabilizing. Another correlation, obtained from a pure-wind estimation 18 h before, suggests the role of wind in generating internal waves in the stratified layers, thus, impacting mixing intensity.

Keyword(s)

turbulence, Gulf of Naples, Mediterranean Sea, coastal boundaries, seasonal destratification, vertical mixing, dissipation rate, turbulent kinetic energy, mixed layer depth, microstructure observations

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Kokoszka Florian, Conversano Fabio, Ludicone Daniele, Ferron Bruno, Bouruet-Aubertot Pascale (2023). A Turbulence Survey in the Gulf of Naples, Mediterranean Sea, during the Seasonal Destratification. Journal Of Marine Science And Engineering. 11 (3). 499 (24p.). https://doi.org/10.3390/jmse11030499, https://archimer.ifremer.fr/doc/00822/93393/

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