Layered double diffusive convection of heat and salt

Heat and salt transport through a system consisting of a layer of cool fresh water resting on top of a layer of warm salt water were studied in two, quasi-steady experiments. Although the overall density difference due to salinity was always greater than that due to temperature, two convecting regions persisted separated by a thermocline, a region of large temperature and concentration gradients. Molecular diffusion was found to be the dominant transport mechanism in the central portion of the thermocline. As the overall stability number ((density difference due to salinity)/(density difference due to temperature)) increased the thermocline became thicker and the ratio of salt to heat flux decreased. These two characteristics of the thermohaline system are shown to be consistent with a conduction-convection model which views the thermocline as a conduction region separating two convective boundary layers.