Monitoring of the Kuroshio over the Izu Ridge
Yasushi Yoshikawa*1, Takeshi Taneda*2, and Kimio Hanawa
Tohoku University
*1 Present affiliation: Japan Marine Science and Technology Center
*2 Present affiliation: Hokkaido National Fisheries Research Institute
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 carried out 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 467 cross section 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 anticyclonic 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 the Kuroshio core. Mean speed ofthe 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 also presented in our talk.
Furthermore, recent JAMSTEC activity related to the TOLEX-ADCP will be presented.
