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Monitoring of the Kuroshio over the Izu Ridge

 

Yasushi Yoshikawa (Ocean Research Department, Japan Marine Science and Technology Center, 2-15 Natsushima, Yokosuka 237-0061, Japan) E-mail: yoshikaway@jamstec.go.jp

Takeshi Taneda (Seikai National Fisheries Research Institute, 49 Kokubun-cho, Nagasaki 850-0951, Japan) E-mail: taneda@snf.affrc.go.jp

Kimio Hanawa (Department of Geophysics, Graduate School of Science, Tohoku University, Aoba-Ku, Sendai 980-8578, Japan) E-mail: hanawa@pol.geophys.tohoku.ac.jp

 

ABSTRACT

 

The monitoring of the Kuroshio Current System over the Izu Ridge, south of Japan, using the hull mounted ADCP on a ferry Ogasawara Maru has been conducted by the Physical Oceanography Group of Tohoku University. This ADCP monitoring is one of the TOLEX (Tokyo-Ogasawara Line Experiment) programs. In this paper we will present the several aspects of the current fields using the data obtained from February 1991 to January 1996.

During the period, the Kuroshio took the bimodal paths of 34°00'N and 32°30'N as mean position on the ship course. In the sea south of the Kuroshio, many cyclonic and anti-cyclonic eddies with a scale of 200-400km in diameter were observed with passing time of two-four months.

The Kuroshio variability is studied by using the time series of the current speed at 47m depth in theKuroshio core. Mean speed of the Kuroshio was 106cm/s and its standard deviation was 28cm/s. We found a signal linked the bimodal path. That is, the Kuroshio speed was high, 112cm/s on average, when it took around the southern path (33°00'N-32°30'N). On the other hand it was low, 101cm/s, when it took around the northern path (34° 20'N-33° 50'N). The difference is about 10% of the mean Kuroshio speed. The time series does not show the significant seasonal signal of the Kuroshio.

The structure of the Kuroshio and its volume transport will be presented in our talk.

 

 

 

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