May/2/2017: Prof. Ming-Huei, Chang’s Speech:
Title: Zonal migration and transport variations of Kuroshio off Taiwan induced by eddy impingement
Abstract: Variability of the Kuroshio off Taiwan was observed at a cross-stream transect ~50 km south of PCM1 line by an array of three moored ADCPs measuring for ~23 months, supplemented with eleven repeated shipboard surveys. Observations of the Kuroshio’s velocity structure revealed the absence of seasonality but significant variability at 70-200 day period for both maximum velocity axis migration and transport due primarily to interactions of the Kuroshio and mesoscale eddies.
Empirical orthogonal function (EOF) analysis shows the migration and transport modes explain 46% and 29% of the total variance, respectively, which is in contrast to the findings at the PCM1 line where the transport mode explained more variance than did the migration mode. The Kuroshio transport in the upper 500 m was 17.2 Sv with a standard deviation of 5 Sv caused by Kuroshio-eddy interactions. When single anticyclonic (cyclonic) eddies encountered the Kuroshio, they enhanced (reduced) poleward transport presumably by increasing (decreasing) the sea level anomaly (SLA) along the eastern flank of the Kuroshio (correlation=0.82). When a pair of eddies impinged on the Kuroshio, the upstream confluence and diffluence caused by the dipole eddies increase and decrease the Kuroshio transport, respectively. Furthermore, The eastward (westward) currents as a result of either the single eddy or the dipole eddy produce flow divergence (convergence) adjacent to the Kuroshio’s eastern edge, favoring the offshore (onshore) migration of the Kuroshio axis.