IMPORTANCE OF CONVECTIVE MIXING IN SEASONAL ICE MARGIN SIMULATIONS

A two-dimensional ice-ocean model applicable to the Greenland Sea is constructed and used to examine the role of penetrative convection in the seasonal advance and retreat of the sea ice margin. The standard version of the model is based on the full dynamic and thermodynamic equations of sea ice and on the primitive equations discretized on a vertical slab for the ocean. It includes a special treatment of upper ocean vertical mixing based on a parameterization of entrainment at the bottom of the ocean mixed layer. The simulation results with this standard version of the model show that when ice advection is included with ice moving outward over open water, penetrative convection delays and greatly reduces the ice edge advance. The resulting seasonal ice distribution yields better agreement with observation than a simulation that does not allow mixed layer entrainment. When lateral heat transport is neglected in the ocean, the ice margin again moves too a great extent outward. This result demonstrates that in addition to vertical mixing, a heat source must exist in the ocean mixed layer in order to resist and ultimately stop the advection of ice. Finally, in the absence of ice motion, penetrative convection has a less pronounced effect on the ice edge location.