twelveth layer is northward from April to November with maximum value of about 5 cm/sec (Figure 10a).
Figures 9a and 9b show the July layer velocities in the 11th layer and in the 12th layer, respectively. In the 11th layer bounded between 1000m and 2000m, the flow is northward in the north-east Indian Ocean and is reflected back to the Indian Ocean. It is shown that in the Indonesian sea the southern hemispher water and deep equatorial water in this layer move northward to the east of Mindanao island and there bifulcates into eastward and into northward under Kuroshi current at 12 N (Figure 9a). Along the Mindanao island and Pacific western boundary area these northward flow situated in these two layers (between 1000m to 3000m) is barotropic, while the flow in the Indian Ocean in these two layers is baroclinic.
Since the model resoltion is too coase to resolve small gappy islands chain in the Indonesain seas, it is not appropreate to concluded that the exact quantitive estimate of the northward flow through the Indonesian sea. However, the mechanism of the deep layer flow in this coase resolution model may be examined in finer resolution model. We feel that the annual cycle of inter-basin pressure anomaly may be responsible for inter-basin scale deep layer circulation and that this mechanism will also be excuted in finer resolution ocen model.
3c Sensitivity experiments to thermal and wind forcing.
The mixed layer circulation pattern and seasonal variation of flow through Indonesian seas is investigated with respect to its sensitivity to (i) atmospheric winds, and (ii) atmospheric thermal forcing. Although each experiemt generally presents a physically unrealistic situation, it does allow one to clearly identify the contribution that each of the components (i) and (ii) makes to the maintenance of the mixed layer circulation and flows in the deeper layers. In particular, we wish to determine whether the flows in the mixed layer and deep layer in the Indonesian seas are mainly wind driven or buyancy driven. The goal of this sensitivity studies presented below is to identify the dominant mechanism driving the mixed-layer circulation and subsurface and mid-depth circulation in the Indonesian seas.
In each experiment, only a single change has been made with respect to the controle run setup, and that each experiment was integrated for 20 years after 130 years of controle run. Figure 10a is the meridional velocity in each layer of the controle run. It is shown that the mixed layer and the second layer velocities are in pahse and represent wind driven surface flow corresponding to the local monsoonal wind variation. However, the summer time strong northward flow is dominant in the 12th layer and the remnant of the northward flow can be seen at all the depth from the 3rd layer to the 12th layer. This indicates that the flows in the Indonesian seas consist of two flow regimes: one flow regime for the mixed layer and the 2nd layers that balance with local monsoonal wind stress forcing and the other flow regime from the 3rd layer to the 13th layer that is essentally driven by inter-basin
