Surface velocity time series derived from satellite altimetry data in a section across the Kuroshio southwest of Kyushu |
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| Authors: | Hirohiko Nakamura Ayako Nishina Kotaro Tabata Masataka Higashi Akimasa Habano Toru Yamashiro |
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| Institution: | (1) Faculty of Fisheries, Kagoshima University, 4-50-20 Shimoarata, Kagoshima 890-0056, Japan;(2) Sanyo Techno Marine Inc., Tokyo, Japan;(3) Faculty of Engineering, Kagoshima University, Kagoshima, Japan |
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| Abstract: | A time series of surface geostrophic velocity is developed using satellite altimetry data during 1992–2010 for a track across
the Kuroshio southeast of Kyushu, Japan. The temporal mean geostrophic velocity is estimated by combining the along-track
sea level anomaly and shipboard ADCP data. This approximately 6-km resolution dataset is successful in representing the Kuroshio
cross-current structure and temporal variation of the Kuroshio current-axis position during 2000–2010. The authors use this
dataset to examine the winter Kuroshio path destabilization phenomenon. Its seasonal features are characterized as follows:
the velocity shear on the inshore side of the Kuroshio becomes stronger and the Kuroshio path state becomes unstable from
the summer to winter. This evidence is consistent with the hypothetical mechanism governing the destabilization phenomenon
discussed in a previous study. Furthermore, the interannual amplitude modulation of the seasonality is examined in relation
to interannual variations in the winter northerly wind over the northern Okinawa Trough and the Pacific Decadal Oscillation
(PDO) index. The destabilization phenomenon appears 15 times in the period 2000–2010. Ten cases are related to local wind
effects, and 7 of these are also connected with the PDO index. This is probably because the winter northerly wind over the
northern Okinawa Trough is regulated by the PDO signal in interannual time-scales. Only 4 cases are related to the PDO index,
but their driving mechanism remains uncertain. |
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