Abstract
This study examined the statistical features of eddies approaching the Kuroshio east of Taiwan Island and Luzon Island. In total, 315 eddies (138 anticyclonic and 177 cyclonic eddies) were detected from 19.5 years of satellite altimeter sea-level data, with more than 95% of these eddies being generated in the ocean west of the Mariana Islands. Eddy trajectory statistics indicated that eddies frequently intrude into the Kuroshio regime at two latitude bands, namely 18°N–19°N and 22°N–23°N, with periods of 146 ± 62 and 165 ± 46 days, respectively. The interaction time is longer within the two active bands (33 ± 10 days at 18°N–19°N and 45 ± 17 days at 22°N–23°N) than at other latitudes. These two eddy-intrusion bands are associated with the northern and southern Subtropical Countercurrents (STCCs). These STCCs have a vertically reversed sign of the meridional potential vorticity gradient, thus providing a key energy source for eddy generation. In addition, when westward-propagating eddies approach the Ryukyu Islands, the southwestward recirculation flow east of the island chain as well as topographic effects cause some eddies to head southwestward to the east of Taiwan and intrude into the Kuroshio at 22°N–23°N, rather than to dissipate directly. Therefore, we suggest that the STCCs play a key role in inducing the eddies to frequently intrude into the Kuroshio at 18°N–19°N and 22°N–23°N. In addition, the Ryukyu Islands are responsible for concentrating the eddies within 22°N–23°N.
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Acknowledgements
The authors appreciate all of the constructive comments from reviewers. The altimeter products used in this study were produced by Ssalto/Duacs and distributed by AVISO, with support from CNES (http://www.aviso.oceanobs.com/duacs/). The eddy data set was produced by Dudley B. Chelton and Michael G. Schlax (http://cioss.coas.oregonstate.edu/eddies/). Cheng and Ho were supported by the National Science Council of Taiwan (NSC 101-2611-M-019-003 and NSC 102-2611-M-019-011). Cheng and Hu were supported by the National Natural Science Foundation of China (U1405233).
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Cheng, YH., Ho, CR., Zheng, Q. et al. Statistical features of eddies approaching the Kuroshio east of Taiwan Island and Luzon Island. J Oceanogr 73, 427–438 (2017). https://doi.org/10.1007/s10872-017-0411-7
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DOI: https://doi.org/10.1007/s10872-017-0411-7