A numerical study of haline convection beneath leads in sea ice

Leads are openings in sea ice in polar oceans which result from divergence in ice drift. Although they represent a small percentage of the total 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 associated brine rejection in the upper water column. Depending on the ice‐water velocity difference, the brine is mixed away by convective sinking or by turbulent mixing associated with ice‐water momentum flux. In this study, a two‐dimensional numerical model is used to examine the 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 typical buoyancy forcing and ice‐water velocities it is found that both of these regimes should be typically operative in the Arctic Ocean. The results also illustrate that geostrophic adjustment produces along‐lead surface and subsurface jets. Comparison with laboratory results, however, suggests that rotation does not play a major role in the turbulent adjustment.