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

Abstract

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.

The Spatial Distribution of Copepod Functional Traits in a Highly Anthropized Mediterranean Coastal Marine Region

“…The Sarno River is considered the most polluted river in Europe due to heavy metal contamination from industrial activities along its course [52]. From a physical point of view, the Gulf of Naples [53,54] shows a period of stratification in July-August and a period when the water column is close to completely mixing from December to January, followed by surface re-stratification in February. Similar detailed knowledge about the water stratification processes is not available for the Gulfs of Gaeta or Salerno.…”