Journal of the korean society of oceanography

The Korean Society of Oceanography (한국해양학회)
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Eddy Formation Near the Izu-Ogasawara Ridge and its Link with Seasonal Adjustment of the Subtropical Gyre in the Pacific

  • Ihara, Chie (Dapartment of Earth and Planetary Science, Graduate School of Science, The University of Tokyo) ;
  • Kagimoto, Takashi (IGCR, Frontier Research System for Global Change) ;
  • Masumoto, Yukio (Dapartment of Earth and Planetary Science, Graduate School of Science, The University of Tokyo) ;
  • Yamagata, Toshio (Dapartment of Earth and Planetary Science, Graduate School of Science, The University of Tokyo)
  • Published : 2002.09.01
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Abstract

Using OGCM results, we have shown that the ring-like cold baroclinic eddies associated with cyclonic circulation are shed from late summer to early fall near the Izu-Ogasawara Ridge from the Kuroshio Extension owing to baroclinic instability. On the other hand, warm baroclinic eddies are generated by the intensified western boundary current associated with the warm anomaly accumulated near the Ridge in winter, which corresponds to the basin-wide barotropic intensification of the wind-driven gyre in winter. We are successful in reproducing the behavior of those meso-scale eddies using a simple two-layer primitive equation model driven by seasonal winds associated with the positive curl. Those eddies carry barotropic seasonal signals originated in the Pacific Basin quite slowly west of the ridge; this process introduces a phase lag in the timing of the seasonal maximum transport in the Philippine Basin west of the ridge. It Is demonstrated that the existence of bottom topography, baroclinicity, and nonlinearity due to advection are three necessary elements for the generation of these eddies south of Japan.

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