The formation of a layered structure when a stable salinity gradient is heated from below

Abstract

It is well known that heating a stable salinity gradient from below leads to the formation of a series of turbulently convecting layers separated by stable diffusive interfaces. It is argued theoretically and demonstrated experimentally that the first mixed layer grows to a critical height δc, which is determined by a balance between the vertical kinetic and potential energies of the turbulent eddies, before a growing second layer separated from the first layer by a quasi-stationary stable density interface can be formed. Although the thermal boundary layer that develops over the propagating turbulent front can become unstable and form a second mixed region before the first layer grows to δc, the density interface formed between these two layers is not sufficiently stable to resist quick entrainment of the second layer into the lower layer. Some aspects of the growth of the first turbulent layer and possible application of the results to oceanic situations are also discussed.