Figure 4: Time-averaged layer thicknesses and velocity fields when wind stress in the northern hemisphere wind stress is changed, for (a) α=0.00, (b) α=0.50, (c) α=1.00, (d) α=1.50.
Figure 4 shows the time-averaged (over 1 year) layer thicknesses and the time-averaged velocity fields of cases a=0.00, 0.50, 1.50, and 2.00.
In the α=0.00 case (Fig. 4 (a)), the wind stress curl in the northern hemisphere is zero. Therefore, the Sverdrup transport is zero. The zonal pressure gradient (Fig. 4 (a)) just balances to the zonal wind stress. MC does not exist in this case. On the other hand, there is strong direct inflow from the New Guinea Coastal Current to the Banda Sea and the Makassar Strait. The current circulates around Australasia only within the southern hemispher.
When α=0.50 (Figs. 4(b)), the MC appears. As the MC becomes strong (Figs. 4 (b)〜(d)), the more IT comes from the MC. On the other hand, the direct inflow into the Indonesian Seas from the New Guinea Coastal Current becomes weak with the increase of the northern hemisphere wind (Fig. 4). Instead of it, the Halmahera eddy and the associated return flow within the Pacific Ocean becomes strong.
Another feature is the overshoot of MC goes further southward offshore of the Mindanao island with the increase of MC strength. From the α=1.50 case (Figs. 4(d)), the MC finally hits the modeled Celebes island.
We also test the linear runs which exclude the nonlinear terms from the model equations (Fig.5). Figure 5 shows time-averaged layer thicknesses and velocity fields for the linear cases. The linear cases also show that the inflow from the MC increases with the wind strength in the northern hemisphere. Notable difference is that that the MC does not overshoot like the nonlinear cases. In the linear cases, the most of the MC once enters the Celebes Sea as the boundary current. Then the MC bifurcates to the North Equatorial Current and the current in the modeled Makassar Strait (section B).
