Abstract
Temporal variation of the anoxic water mass in Hiuchi-Nada was investigated. Vertical diffusivities at the thermoclines and oxygen consumption rates in the middle and lower layers were estimated by box model analysis using the results of field observations. On the basis of the obtained diffusivities and consumption rates, the time scale for anoxia and the degree of anoxia were examined for various conditions. It was revealed that the time scale for anoxia is about a week in the case where serious anoxia occurs and the degree of anoxia is sensitive to the diffusivity at ‘the second thermocline’. The anoxia which occurred frequently in the 1960's and 1970's is deduced to be caused by oxygen consumption rates a few times larger than the average at present and by diffusivities a few tens of per cent smaller than those under normal conditions.
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Ochi, T. and H. Takeoka (1986): The anoxic water mass in Hiuchi-Nada, Part 1. Distribution of the anoxic water mass. J. Oceanogr. Soc. Japan,42, 1–11.
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Takeoka, H., Ochi, T. & Takatani, K. The anoxic water mass in Hiuchi-Nada. Journal of the Oceanographical Society of Japan 42, 12–21 (1986). https://doi.org/10.1007/BF02109188
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DOI: https://doi.org/10.1007/BF02109188