Vertical structure of low-frequency currents in the southwestern East Sea (Sea of Japan) |
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| Authors: | Yun-Bae Kim Kyung-Il Chang Kuh Kim Jae-Hun Park Jae-Hak Lee |
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| Institution: | (1) Research Institute of Oceanography/School of Earth and Environmental Sciences, Seoul National University, Seoul, 151-742, Korea;(2) Graduate School of Oceanography, University of Rhode Island, Narragansset, RI, 02882-1197, U.S.A.;(3) Climate Change and Coastal Disaster Research Department, Korea Ocean Research and Development Institute, Ansan, 425-600, Korea |
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| Abstract: | The vertical structure of low-frequency flows in the central Ulleung Interplain Gap of the southwestern East Sea (Sea of Japan)
is analyzed based on full-depth current measurement during November 2002–April 2004. Record-length mean flows are directed
toward the Ulleung Basin (Tsushima Basin) throughout the entire water column. Upper current variability above the permanent
thermocline with a dominant period of about 50–60 days is shown to be closely related to the displacement of an anticyclonic
warm eddy associated with the westward meander of the Offshore Branch. Fluctuations of deep currents below the permanent thermocline
have a dominant period of about 40 days. Coherence between the current near the seabed and shallower depths is statistically
significant up to 360 m for a period range between 15 and 100 days, but less significantly correlated with currents in the
upper 200 m. Data from the densely equipped mooring line reveal that mean and eddy kinetic energies are minima at 1000 m,
where isotherm slopes are also relatively flat. Empirical orthogonal function (EOF) analyses suggest that more than 79% of
total variances of upper and deep currents can be explained by their respective first EOF mode characterized by nearly depth-independent
eigenvectors. Spectral and EOF analyses of observed currents suggest that most of the deep current variability is not directly
related to local upper current variability during the observation period. |
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| Keywords: | Sea of Japan moored current observation low-frequency current variability vertical structure of current |
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