Interaction of salt finger convection with intermittent turbulence

The diapycnal buoyancy fluxes due to the combined presence of salt finger convection and intermittent turbulent events are discussed. In a series of experiments, salt fingers, which were periodically stirred by a comb of vertical rods, were created in a continuous density gradient using the laboratory sugar/salt analog. Measurements of the buoyancy flux were made by measuring the rate of change of the density gradient. Particular attention was paid to how the time-averaged buoyancy flux varied as the frequency of stirring was increased relative to the characteristic timescale for growth of the salt fingers. We found that the mean buoyancy flux was up gradient when the time between stirring events was longer than several e-folding periods of the salt finger growth rate. When stirring was more frequent, the salt fingers were continuously disrupted, resulting in a mean down-gradient buoyancy flux, characteristic of stratified turbulence. Using data for salt finger convection and intermittent turbulence in the oceanic thermocline and extrapolation of the laboratory results, we examine the sensitivity of salt finger buoyancy fluxes to intermittent turbulence in the oceans.