Double-Diffusive Convection and its Implications for the Temperature and Salinity Structure of the Ocean and Lake Vanda

Abstract

Recently, Fedorov has attempted to interpret some temperature and salinity profiles in the northeast Atlantic, as reported by Zenk, in terms of the results of laboratory experiments in double-diffusive convection. We argue here that the laboratory experiments do not adequately cover all the oceanographic phenomena contained in these records and that Fedorov's interpretation is inappropriate. Before laboratory results can he used at all in interpreting oceanographic data, however, confirmation that the results of small-scale experiments can be transferred quantitatively to large-scale motions is needed. Such a confirmation is attempted here using the observed profiles in Lake Vanda. A steady-state model of Lake Vanda is considered which determines that heat flux through each double-diffusive interface which is necessary to maintain the lake in a steady state. Using an empirical formula connecting the heat flux and the temperature jump across an interface, we calculate a temperature profile for that part of the lake which is in a state of double-diffusive convection. The agreement between the temperature profile so calculated and the one observed is a test of the derived steady-state heat flux formula. The agreement is surprisingly good and we conclude that, under the assumptions incorporated in the model, this particular experimental result can be used in describing large-scale motions.