SIMULATION OF THE MIXED-LAYER CIRCULATION IN THE ARCTIC-OCEAN

A numerical simulation of the mixed-layer circulation of the Arctic Oc ean is presented using Oberhuher'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 ho rizontal resolution is 2 degrees. The vertical is resolved using five isopycnal layers, of which the uppermost layer is a turbulent mixed la yer. The sea ice is modeled using a thermodynamic-dynamic model which includes a viscous-plastic theology. Monthly climatological atmospheri c forcing is used to spin up the model into a cyclostationary equilibr ium. Model results are presented and discussed with respect to observa tional and previous modeling studies. The mixed layer shows a circulat ion pattern similar to that inferred from indirect observations and ot her modeling studies. In an attempt to determine the main driving mech anism for the mixed-layer circulation as produced by the Oberhuber mod el, a set of sensitivity experiments is carried out. Tn particular, th e relative importance of (1) ice cover, (2) atmospheric winds, (3) sur face freshwater fluxes, and (4) initialization with Levitus [1982] dat a is examined to determine the contribution each makes to the modeled circulation. The key conclusion is that buoyancy forcing is critical t o maintaining the mixed-layer circulation.