Figure 5: Same as Fig. 4 except for linear cases.
Time-averaged transports across the 3 sections in Fig. 2(b) are summarized in Fig. 6 for (a) the nonlinear cases and (b) the linear cases. The total IT southward volume transport (across the section A) changed from 12.9 Sv in the α=0.00 case to 11.4 Sv in the α=2.00 case. The total transport decreases with the increase of wind stress curl in the North Pacific Ocean. However, this decrease (1.5 Sv) is very small. The transport of the IT is insensitive to the North Pacific wind stress. This is exactly anticipated from Godfrey (1989)'s Island Rule. In addition, the difference of the total IT transport between the nonlinear case (Fig. 6(a)) and the nonlinear cases (Fig. 6(b)) is very small. This shows that the Godfrey (1989)'s linear model is applicable to the total IT volume transport even if strong nonlinearity exists around the Mindanao eddy and the Halmahera eddy.
Although the transport of the total IT has little thing to do with the North Pacific wind stress, the transport through each strait has another story. The transport through the Makassar strait (across section B) increases from 10.3 Sv to 16.1 Sv. Conversely, the transport through the Banda Sea (across the section C) decreases from 2.6 Sv to -5.4 Sv. In other words, the counterclockwise around Celebes island is intensified. These changes are not small. Roughly speaking, this means that the the water from the North Pacific Ocean (the South Pacific Ocean) increases (decreases) in composition of the IT with the wind stress in the northern hemisphere. In the linear cases, the variations of the transport through section B and C are much smaller than in nonlinear cases. Therefore, it can be concluded that the increase of the transport through the Makassar Strait is enhanced by nonlinearity.
