TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 61 (No. 6), pp. 1089-1099, 2005

Variability of Current Structure Due to Meso-Scale Eddies on the Bottom Slope Southeast of Okinawa Island

Masanori Konda1,2*, Hiroshi Ichikawa1,3, In-Seong Han1, Xiao-Hua Zhu1 and Kaoru Ichikawa1,4

1Institute of Observational Research for Global Change, Japan Agency for Marine-Earth Science and Technology, Natsushima, Yokosuka 237-0061, Japan
2Department of Geophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
3Faculty of Fisheries, Kagoshima University, Kagoshima 890-0056, Japan
4Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580, Japan

(Received 16 June 2004; in revised form 2 February 2005; accepted 21 April 2005)

Abstract: The relationship between the vertical profile of current on the bottom slope southeast of Okinawa Island and the offshore meso-scale eddy propagated from the east was examined by combined use of the data obtained by a moored upward-looking ADCP (Acoustic Doppler Current Profiler), PIES (Inverted Echo Sounder with Pressure gauge), hydrographic surveys and satellite altimetry during a period from November 2000 to August 2001. The variability of current component parallel to the isobath in the layer over 600 m is found to be markedly different from that in the layer below 600 m. The current variability in the upper and the lower layer can be well explained by the first and second modes of the EOF (Empirical Orthogonal Function) decomposition. The PIES and the sea surface height anomaly data suggest that the first mode represents the surface-trapped current associated with the approach of the offshore meso-scale eddy from the east, whereas the second mode has a bottom-intensified structure. The second mode velocity tends to delay to the first mode. The hydrographic data derived from CTD (Conductivity-Temperature-Depth meter) and PIES data along the line across the isobath suggest that the second mode component is generated by the interaction between the meso-scale eddy and the bottom topography.

*Corresponding author E-mail: konda@kugi.kyoto-u.ac.jp

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