Mechanisms governing the winter Kuroshio path destabilization Phenomenon in the East China Sea and its interannual amplitude modulation

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The present study investigated the mechanism responsible for the winter Kuroshio path destabilization phenomenon in the northern Okinawa Trough. Theoretical consideration and a numerical model revealed the following mechanism : The winter northerly wind over the Okinawa Trough blows against the Kuroshio, generating upwelling within the inshore side of the Kuroshio. This winter upwelling makes the mean Kuroshio path separate from the continental slope in the northern Okinawa Trough so that baroclinic instability destabilizes the Kuroshio path. Furthermore, a new time series of satellite-derived geostrophic velocity distribution was developed in a section across the Kuroshio in the period 1992-2010. This dataset indicated that the interannual amplitude modulation of the seasonality is mainly caused by interannual variation in the winter northerly wind over the northern Okinawa Trough.