The turbulence model

To close the differential equations for momentum, heat, and salt, parameterisations of the turbulent fluxes of momentum, ${\langle u' w' \rangle}$, heat ${\langle w'\theta' \rangle}$, and salinity ${\langle w's' \rangle}$ are required. Since turbulence `feels' the effects of temperature and salinity fluctuations essentially through buoyancy fluctuations, only the buoyancy flux, ${\langle w'b' \rangle}$, is discussed in the following. The assumptions under which one can infer the fluxes of heat and salinity from the buoyancy flux are addressed below.