Observation and analysis of mixing in a tidal and wind-mixed coastal region

In this article, the authors first present oceanic observations collected in a coastal area in May 2007. The evolution of temperature profiles exhibits a very clear atmospheric heating signal and is used to study mixing. Modelled atmospheric fluxes are evaluated using the oceanic measurements. The K-profile parameterisation (KPP) is chosen to identify the most important mixing processes and its parameters are tuned to minimise differences with respect to the observations.It is found that:
• the tuned KPP is able to accurately represent the effect of mixing in this case;
• surface and bottom boundary layers, as well as interior shear instability mixing processes all play an important role in the observed evolution of the temperature profile, the bottom boundary being the source of the most intense mixing;
• the nonlocal effects in KPP (activated during nocturnal cooling periods) have to be switched off for a better agreement.

Research highlights
► Oceanic coastal observations are used to study mixing processes.
► The atmospheric heating signal and its downward propagation can be isolated in those.
► Sensitivity studies are conducted using the K-profile parameterisation (KPP).
► The bottom boundary layer is responsible for the most important part of mixing.
► Here, the nonlocal effects in KPP have to be switched off for a better agreement.