TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 54 (No. 5), pp. 465-478, 1998

Unusual Behavior of the Kuroshio Current System from Winter 1996 to Summer 1997 Revealed by ADEOS-OCTS and Other Data--Suggestion of Topographically Forced Alternating-Jet Instability

Yoshiaki Toba1,2 and Hiroshi Murakami1

1Earth Observation Research Center, National Space Development Agency of Japan (EORC, NASDA), 1-9-9 Roppongi, Minato-ku, Tokyo 106-0032, Japan
2Japan Marine Science and Technology Center (JAMSTEC), Natsushima-cho, Yokosuka 237-0061, Japan

(Received 31 March 1998; in revised form 18 June 1998; accepted 19 June 1998)

Abstract: While the Advanced Earth Observing Satellite (ADEOS) was operating, the Kuroshio and the Kuroshio Extension, or the Kuroshio Current System, exhibited unusual behavior from the winter of 1996 to the summer of 1997. This behavior of the Kuroshio Current System has been closely studied using a time series of satellite observation images of SST and ocean color obtained by ADEOS-OCTS, reinforced by SST images obtained by NOAA-AVHRR. Our findings include (i) a long lasting, very southerly path of the Kuroshio Extension; (ii) a Kuroshio path very distant from Japan with the following alternating-jet-like north-south flow pattern of the Kuroshio Extension, which occurred twice, once in February and once in April 1997, as independent events and which was observed to be affected by the bottom topography of the Izu-Ogasawara Ridge and Trench, and of the Japan Trench; (iii) cutting off of a cold water mass after the February event; and (iv) the formation of a vortex pair after the April event. A new mechanism is suggested for the formation of the alternating-jet flow pattern: a topographically forced alternating-jet instability (AJI). An SST-Chlorophyll Diagram (T-Chl Diagram) generated using simultaneous data from a single satellite is useful for analyzing the water mass structure of this region, including biological processes.

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