Choked Flows from the Pacific to the Indian Ocean

Abstract

The author considers two oceanic basins separated by a meridional wall. The wall contains a gap that is initially blocked by a gate; westward winds are allowed to blow over the two-layered oceans creating western boundary currents and a sea level difference between the basins. The conceptual gate is then removed and the resulting nonlinear flow is computed. The analytical calculations are based on a simple wind-driven general circulation model and a nonlinear integrated momentum constraint. Two classes of nonlinear solutions are constructed. One corresponds to a situation where the flow through the gap originates from the right-hand side (looking upstream) of the inner Pacific basin and the other to a situation where the flow originates from the left-hand side. It is suggested that the actual Indonesian Throughflow is composed of both of these classes of flows; that is, the throughflow corresponds to an exchange via two adjacent gaps. Computations suggest that approximately 6 Sv (Sv ≡ 106 m3 s?1) enter the passages from the North Pacific and 1 Sv from the South Pacific giving a total of 7 Sv. This may resolve the apparent difficulty associated with existing linear theories (and nonlinear theories that neglect western boundary currents), which predict that without strong turbulent diffusion only South Pacific water can enter the passages.