The use of ocean microstructure to quantify both turbulent mixing and salt-fingering

Abstract

A method is developed whereby the vertical fluxes of heat and salt can be deduced from oceanic microstructure measurements of temperature and shear variance. This method is appropriate when both turbulent mixing and double-diffusive convection contribute to the vertical property fluxes. Previous methods that deduce property fluxes from microstructure measurements have assumed that either turbulent mixing or double-diffusive convection is the cause of the observed microstructure; here we present a method suitable for the more general situation where both mixing processes contribute to the property fluxes in the region of interest. The key assumptions are that the mixing efficiency of the turbulence and the flux ratio of the salt fingers are unchanged by the presence of the other process. It is found that sufficiently accurate total heat and salt fluxes can be deduced from the microstructure data, but our present imprecise knowledge of the salt-finger buoyancy flux ratio places large error bars on the total buoyancy flux.