Gap‐leaping Kuroshio and blocking westward‐propagating Rossby wave and eddy in the Luzon Strait

Abstract

AbstractBased on analysis of both observational data and data‐assimilation model product, it is shown that there exists a gap‐leaping path of the Kuroshio in the Luzon Strait. Numerical results of two sets of Hybrid Coordinate Ocean Model twin experiments indicate that bottom topography and islands in Luzon Strait exert control of Kuroshio's gap‐leaping behavior, especially existence of sharp northeast cape of Philippine Island is one of the most important factors for the gap‐leaping Kuroshio path in model simulation. Corresponding to the gap‐leaping Kuroshio, there is steep westward shoaling of thermocline in Luzon Strait. The enhanced upper‐layer stratification in South China Sea due to westward shoaling thermocline results in strong zonal potential vorticity (PV) gradient (one order higher than ß‐induced planetary PV gradient), and PV isolines are always parallel to the gap‐leaping path of the Kuroshio. This PV front acts as a dynamic barrier in the Luzon Strait, blocking the westward propagating Rossby waves and eddies from Pacific. This blocking effect is verified through sea‐surface height anomaly spectrum analysis, Radon Transform based Feature‐Tracking method, and eddy identification and tracking method. Numerical twin experiments demonstrate from another point of view that the gap‐leaping Kuroshio can efficiently block the westward propagating Rossby wave and eddy energy, while the fluctuating Kuroshio is less efficient for blocking.