Haline Convection in Polynyas and Leads

Abstract

A theoretical analysis of haline convection induced by the freezing of sea water is made for a turbulent ocean. The nonlinear equations for two-dimensional flow are solved using the mean field approximation and expanding the variables in Fourier series. It is found that, when the depth of the mixed layer is sufficiently large, the convective process is independent of depth. Expressions for the horizontal spacing of convection cells, maximum vertical velocity, and time required for manifest convection to develop are derived for a range of Schmidt numbers appropriate for the ocean. The analysis is applied to conditions that may be typical of freshly frozen polynyas or leads in the Weddell Sea, and it is concluded that haline convection is probably an effective process as a precursor to Antarctic Bottom Water formation.