Interannual variability of the Kuroshio Extension and its relation to the Southern Oscillation/El Niño

The interannual variability of the temperature structure of the Kuroshio Extension is studied by establishing time series for the period 1950 to 1970 and then comparing it with the time series of sea level differences across the North Equatorial Current obtained by Wyrtki (1975). First, the present analysis shows a significant correlation between the interannual fluctuation of the Kuroshio Extension and the eddy activity south of the Kuroshio axis, suggesting the importance of the eddy-driven mechanism. Secondly, spectral analysis shows close connections between the Kuroshio Extension and the North Equatorial Current with a reasonable time lag of about 1.5 years. This time lag of the mid-latitude variability is also supported by other independent data. In particular, the present preliminary study strongly suggests that the bimodal behavior of the Kuroshio path south of Japan and the intensity of the Kuroshio Countercurrent are closely connected with the Southern Oscillation/El Niño.