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  • Eddy‐Kuroshio Interactions:...
    Jan, Sen; Mensah, Vigan; Andres, Magdalena; Chang, Ming‐Huei; Yang, Yiing Jang

    Journal of geophysical research. Oceans, December 2017, 2017-12-00, 20171201, Letnik: 122, Številka: 12
    Journal Article

    Quasi‐geostrophic mesoscale eddies regularly impinge on the Kuroshio in the western North Pacific, but the processes underlying the evolution of these eddy‐Kuroshio interactions have not yet been thoroughly investigated in the literature. Here this interaction is examined with results from a semi‐idealized three‐dimensional numerical model and observations from four pressure‐sensor equipped inverted echo sounders (PIESs) in a zonal section east of Taiwan and satellite altimeters. Both the observations and numerical simulations suggest that, during the interaction of a cyclonic eddy with the Kuroshio, the circular eddy is deformed into an elliptic shape with the major axis in the northwest‐southeast direction, before being dissipated; the poleward velocity and associated Kuroshio transport decrease and the sea level and pycnocline slopes across the Kuroshio weaken. In contrast, for an anticyclonic eddy during the eddy‐Kuroshio interaction, variations in the velocity, sea level, and isopycnal depth are reversed; the circular eddy is also deformed to an ellipse but with the major axis parallel to the Kuroshio. The model results also demonstrate that the velocity field is modified first and consequently the SSH and isopycnal depth evolve during the interaction. Furthermore, due to the combined effect of impingement latitude and realistic topography, some eddy‐Kuroshio interactions east of Taiwan are found to have remote effects, both in the Luzon Strait and on the East China Sea shelf northeast of Taiwan. Plain Language Summary Mesoscale eddies are everywhere in the ocean. These ocean swirls of either clockwise or counterclockwise spinning with diameter of about 100‐300 km and rounding current speed of about 0.5 m/s, carrying energy and certain type of water mass, move westward and eventually reach the western boundary of each ocean. The evolution of these eddies and the interaction which occurs when they encounter the western boundary current, e.g. the Kuroshio in the western North Pacific, is important in redistributing ocean energy and, in turn, shaping the large scale ocean circulation. This study focuses on the processes underlying the interaction of nonlinear mesoscale eddies with the Kuroshio, which have not yet been thoroughly investigated in the literature. Using pressure‐sensor equipped echo sounder and satellite observations interpreted in the context of semi‐idealized numerical simulations, this study find (1) locally, eddy arrivals modify velocity structure in the Kuroshio first, followed by changes in sea level and isopycnal depths leading to seesaw‐like variations of the sea level and density slopes across the Kuroshio, and (2) modeled remote effects, i.e., Kuroshio intrusions, manifest in the Luzon Strait and on the East China Sea shelf and depend on the eddies' impingement latitude, strength, and polarity. Key Points Observations of eddy‐Kuroshio interactions are interpreted through numerical simulations with varying eddy strength and impinging latitude Locally, eddy arrivals change sea level and isopycnal depths leading to seesaw‐like patterns across the Kuroshio Modeled remote effects manifest at the Luzon Strait and East China Sea shelf and depend on the eddies' impingement latitude and polarity