Study on the variability of the Kuroshio at the entrance into the East China Sea

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The variability of the Kuroshio at the entrance into the East China Sea (ECS) is studied mainly using the OKITAI submarine cable voltage data along with satellite altimetry data and drifter-derived surface current data etc. The cable voltage data of about 9 years can monitor the variability of the Kuroshio transport downstream side near the entrance. Other data show wide spatial distributions of surface currents etc. The following results are obtained. (1) The Kuroshio transport varies according to the presence of mesoscale ocean eddies off east coast of Taiwan upstream side. Warm (anti-cyclonic) eddies can increase the transport and cold (cyclonic) eddies decrease the transport. Cold eddies make larger variation than warm eddies. Mesoscale eddies propagating from the east appear rather randomly ; several numbers (2～3) per year. Since the lifetime of each eddy is about several months (1～3), the transport is under the influence of mesoscale eddies almost half of a year. (2) Seasonal var … More iations of the transport and flow field around the entrance are examined using monthly means of these data. There are two typical modes in the variations ; "winter mode" and "summer mode". In winter mode (Dec.-Mar.), the Kuroshio transport upstream side off Luzon increases and some of it flows into the South China Sea (SCS) through the Luzon strait bringing the transport decrease off Taiwan. The variation of the transport in ECS is not so large as that of the upstream side, and shows somewhat regional variation. There is some outflow from ECS to the Pacific Ocean through Ryukyu Islands, which contributes the recirculation to the Kurosho. In summer mode (Jun.last half-Aug.), the transport off Luzon decreases with no flow into SCS. In ECS, there is no special outflow for the recirculation. These seasonal variations seem to be consistent with wind fields. (3) Several studies related to the above are additionally tried ; Sea surface temperature observation using a ferry service connecting Okinawa to Taiwan in ECS crossing the Kuroshio, Data and model analysis of surface Ekman currents in ECS, Climatology of sea surface heat flux, clouds and rain fall under the influence of the Kuroshio in ECS. Less