Physical environment of the northern part in the Ariake Sea [Japan]: Variations of tidal currents, turbidity and dissolved oxygen caused by heavy rain and the secondary oscillation of the sea
2005
Yasuda, H.(National Fisheries Univ., Shimonoseki, Yamaguchi (Japan)) | Matsunaga, N. | Tokunaga, T. | Abe, J. | Takashima, S. | Kohno, S. | Uto, T. | Onitsuka, G. | Izawa, M. | Kawano, S.
Field experiments were carried out using a mooring system to elucidate the physical process concerning the environmental variation in the northern area of Ariake Sea. The duration of the experiment was about 19 days from the 12th to the 3lst of July, 2003 when we had both spring and neap tides and heavy rain inducing severe flood in some cities around the sea. We have got the following data from this mooring system; vertical profiles of both of tidal currents and turbidity, dissolved oxygen at the level of two meters from the basin floor and tidal level at the station. It has been revealed from this experiment that the residual current, playing an important role in matter distribution in tidal basins, was rather changeable with the behavior of fresh water discharge. The variation of the residual current has been recognized to be related to the concentration of dissolved oxygen in the lower layer. Harmonic analysis of tidal level, currents, dissolved oxygen and turbidity has suggested some interesting phenomena, especially the existence of a secondary oscillation in Ariake Sea. The result of harmonic analysis using Fourier expansion can show that the period of the secondary oscillation is about 8.37 hours. This oscillation period has a concern in the largest tidal difference of this sea in Japan.
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