资源环境科技发展态势分析平台

Ten ocean state estimate products are analyzed to quantify the multidecadal change of the Mindanao Current (MC). These data sets suggest multidecadal trends of the MC transport since 1961, 1980, and 1993 are weak (-0.3 Sv, +0.7 Sv, and +2.1 Sv, respectively; 1 Sv equivalent to 10(6) m(3)/s) and not robust with respect to the large spread of different data sets. The primary cause is the discrepancies in different wind data sets, and change of the North Equatorial Current's bifurcation latitude also acts to attenuate the MC change. The bifurcation latitude shifts southward (northward) under enhanced (weakened) northeasterly trade winds and feeds less (more) water to the MC. Experimental simulations of a reduced-gravity model forced by reanalysis and model-projected wind trends suggest an asymmetry of the MC's response to wind forcing. Anomalous westerly winds in the western Pacific can dramatically enhance the MC through spinning up the cyclonic local recirculation.

Plain Language Summary Here we attempt to estimate how much the Mindanao Current (MC) has changed over the past decades using 10 ocean state estimate products. The multidecadal trends of the MC volume transport since 1961, 1980, and 1993 were rather weak. We found large discrepancies in the MC's long-term change among different data sets, which are primarily due to uncertainties in surface wind data. The bifurcation point of the North Equatorial Current shifts to the south when the northeasterly trade winds are strengthened and shifts to the north under weakened northeasterly trade winds, which is a process attenuating the MC's change. Spatial structure of the surface wind trend over the Pacific basin is critical in determining the MC's long-term change. We performed simple model experiments and demonstrated that strong westerly wind trends in the western Pacific are particularly favorable for enhancing the MC. Under such condition, a strong cyclonic recirculation with strong mesoscale eddy activity emerges near the western boundary and enhances the MC in a nonlinear manner.