This paper describes the numerical simulation results of tidal current and water exchange in the Seto Inland Sea. Two kinds of computational conditions were prescribed at the open boundary. One is the simple sinusoidal waves of M2 component for Case-1, and another is the composite waves by 28 tidal components for Case-2. Then water exchange computations between the Seto Inland Sea water and Pacific Ocean water were carried out by using the computed flow field of Case-1. In this study, following conclusions are obtained. The computed tidal harmonic constants of M2 component for both cases agree with the observed harmonic constants of M2 component. Around narrow strait, tidal residual flow of Case-2 is larger than that of Case-1 because of the non-linearity of tidal current. The particles thrown into the computed flow field of Case-2 are more dispersed and transported than those of Case-1 by the influence of the non-linearity of tidal current and tidal residual flow. Comparing the computed salinity distribution with the observed salinity distribution, the case of the diffusion coefficient of 500 m2/s gives the most appropriate result. Using these computed flow field and substance dispersion result, the residence time of the Seto Inland Sea is estimated about 200 days.
Among countermeasures against the global warming, attention has been given to the so-called ocean sequestration technique of carbon dioxide, in which CO2 produced and accumulated in plants is introduced into the middle or deeper layers of the ocean, in order to prevent further increase of atmospheric CO2. The subarctic region of the northern Pacific Ocean has recent1y been recognized as a sea area which has the potential to absorb CO2 although oceanographical data of this region are comparatively scarce except for sea areas adjacent to Japan, the Aleutian Islands and the Canadian coast. As this sea region is thought to play decisive roles in the climate fluctuations of the world in the time-scale of decades years, it is indispensable to correctly evaluate effects of the ocean sequestration of CO2 when this technique would actually be undertaken. Based on the flow fields of the whole Pacific Ocean, which were calculated by the data assimilation system, the authors examined changes in CO2 concentration of the ocean which may result from CO2 introduction into the subarctic zone of the northern Pacific Ocean.