Penetrative convection in a horizontal layer of seawater near its freezing point

摘要

a series of numerical experiments are performed to investigate steady thermosolutal Confucian induced by the partial freezing of a horizontal pool of seawater from the top. This study is aimed at achieving a better understanding of the role of convection in transporting oceanic heat into the atmosphere during the formation of a Pollyanna. The mathematical model considered accounts for he density anomaly of seawater and for he dependence of he freezing point on salinity. A new solutal regime is isolated wherein solutal convecion is present even through the solutal expansion coefficient is set to zero. This convecion process arises as a results of the coupling between the fluctuations of tensionless groups characterizing the problem, namely the thermal Rayleigh number, the density ratio and an extremum parameter which quantifies he effect of he nonlinear equation of state. Several indicators of he convection process, su9ch as the Nusselt and Sherwood numbers, the kinetic energy in the fluid layer and the buoyancy are calculated. It is found that a two-layer convecion regime generally predominates for relatively large Rayleigh numbers. These results imply that the penetrative convection which results from the coupling between the nonlinear equation of state and the freezing process acts in such a way as to delay the release of heat to the atmosphere during the formation of a polynya.