The Role of the Mindoro-Sibutu Pathway on the South China Sea Multilayer Circulation

The role of the Mindoro Strait-Sibutu Passage pathway in influencing the Luzon Strait inflow to the South China Sea (SCS) and the SCS multilayer circulation is investigated with a high-resolution (0.1 degrees 8x0.1 degrees) regional ocean model. Significant changes are evident in the SCS upper-layer circulation (250-900 m) by closing the Mindoro-Sibutu pathway in sensitivity experiments, as Luzon Strait transport is reduced by 75%, from -4.4 to -1.2 Sv (1 Sv = 10(6) m(3) s(-1)). Because of the vertical coupling between the upper and middle layers, closing the Mindoro-Sibutu pathway also weakens clockwise circulation in the middle layer (900-2150 m), but there is no significant change in the deep layer (below 2150 m). The Mindoro-Sibutu pathway is an important branch of the SCS throughflow into the Indonesian Seas. It is also the gateway for oceanic waves propagating clockwise around the Philippines Archipelago from the western Pacific Ocean into the eastern SCS, projecting El Nino-Southern Oscillation sea level signals to the SCS, impacting its interannual variations and multilayer circulation. The results provide insights into the dynamics of how upstream and downstream passage throughflows are coupled to affect the general circulation in marginal seas.