Simulation of the mixed‐layer circulation in the Arctic Ocean

A numerical simulation of the mixed‐layer circulation of the Arctic Ocean is presented using Oberhuber 's [1993a] coupled sea ice‐mixed layer‐isopycnal ocean general circulation model. The model domain includes the Arctic Ocean and the Greenland‐Iceland‐Norwegian (GIN) Sea. The horizontal resolution is 2°. The vertical is resolved using five isopycnal layers, of which the uppermost layer is a turbulent mixed layer. The sea ice is modeled using a thermodynamic‐dynamic model which includes a viscous‐plastic rheology. Monthly climatological atmospheric forcing is used to spin up the model into a cyclostationary equilibrium. Model results are presented and discussed with respect to observational and previous modeling studies. The mixed layer shows a circulation pattern similar to that inferred from indirect observations and other modeling studies. In an attempt to determine the main driving mechanism for the mixed‐layer circulation as produced by the Oberhuber model, a set of sensitivity experiments is carried out. In particular, the relative importance of (1) ice cover, (2) atmospheric winds, (3) surface freshwater fluxes, and (4) initialization with Levitus [1982] data is examined to determine the contribution each makes to the modeled circulation. The key conclusion is that buoyancy forcing is critical to maintaining the mixed‐layer circulation.