A NUMERICAL STUDY OF HALINE CONVECTION BENEATH LEADS IN SEA-ICE

Leads are openings in sea ice in polar oceans which result from diverg ence in ice drift. Although they represent a small percentage of the t otal ice cover, they are important sites for large air-sea heat flux. Cooling of the upper ocean results in the refreezing of the lead and a ssociated brine rejection in the upper water column. Depending on the ice-water velocity difference, the brine is mixed away by convective s inking or by turbulent mixing associated with ice-water momentum flux. In this study, a two-dimensional numerical model is used to examine t he upper ocean response to buoyancy and momentum flux associated with leads in sea ice. The results indicate that the ocean response can be quantified in terms of the ratio of these two forcing factors. For typ ical buoyancy forcing and ice-water velocities it is found that both o f these regimes should be typically operative in the Arctic Ocean. The results also illustrate that geostrophic adjustment produces along-le ad surface and subsurface jets. Comparison with laboratory results, ho wever, suggests that rotation does not play a major role in the turbul ent adjustment.