Study on the occurrence mechanism of hypoxic water in the western interior parts of the Ariake sea [Japan] using a two-layer box model
2009
Koriyama, M.(Saga Univ. (Japan)) | Seguchi, M. | Ishitani, T. | Thien, N.D.
In this study, the physical and biochemical parameters concerned with the occurrence of hypoxic water in the western interior parts of the Ariake Sea are analyzed by a two-layer box model using the Saga Prefecture research data in 1972-2004, and the occurrence mechanism of hypoxic water is investigated based on the above analytical results. As a result, the monthly variations of an average year value over 1972-2004 for advection velocity, vertical diffusion coefficient (Kz) and biochemical oxygen consumption rate (R) are clarified, and Kz and R contribute greatly to the temporal variation of DO concentration in lower layer box in summer. Next, the monthly variations of an average value for density stratification degree (P), Kz and R in the 1970s (1972-1980), the 1980s (1981-1990) and the 1990s-early 2000s (1991-2004) are analyzed. As a result, in summer, P and Kz do not have precise change among the calculated periods, but R between the 1970s and from the 1980s on is clearly different. It is considered that one factor which changes R in summer since the 1980s is an increase of organic matter amount and the change of decomposition process of organic matter in the study area.
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