Water quality in the Tokyo Bay is controlled by the load input from rivers, seawater currents, temperature variation, photosynthetic processes and others. On the other hand, 23.5 GJ/s of heat, as of 1995, is discharged into the Bay as cooling water effluent from thermal power plants along the coast. Low temperature water of bottom layers is pumped up and utilized as cooling water in thermal power plants. Although the intake and discharge of cooling water may influence water quality of coastal and inner bay areas where power plants are sited, few quantitative evaluations of the effects of cooling water on the water quality have been made yet.
In the present study, we report a result of computations to predict the effects of cooling water discharge on the water quality of the Tokyo Bay in the summer, based on a "primary ecological model" for two thermal conditions: the current heat discharge of 23.5 GJ/s, and a heat discharge of 28.9 GJ/s which is expected in the future. Flow and water temperature distribution data, computed by Kitahara et al.(2003), were used to run the model. It was concluded that except in the vicinities of outlet points, water quality of the Tokyo Bay in the summer might be little changed by the future increase of 5.4 GJ/s of heat discharge.

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Accurate ocean current measurements near the magnetic dip pole have been carried out in the multi-year ice area of the central Arctic Ocean using ice-drifting buoy, J -CAD (JAMSTEC Compact Arctic Drifter). Because of weakness of the magnetic direction reference near the magnetic dip pole, we need to look more carefully into the compass malfunction in order to obtain accurate ocean current. Using the observational data from J-CAD 6 in 2003, we attempted heading data comparisons of attached compasses with azimuthal data calculated from GPS buoys. Results show that Watson Compass, which is 3-dimensional magneto-metric compass attached on the same cage of WorkHorse 300 kHz ADCP (WH-ADCP), can measure the correct heading with an accuracy of 4 degree over the entire J-CAD 6 trajectory. On the other hand, we found that WH-ADCP compass illustrated good results of heading measurements under the condition which the horizontal magnetic intensity is higher than 3000 nT. Also, we investigated a non-linear response of WH-ADCP compass from a comparison with Watson Compass, which are attached on J-CAD 4 in 2002. A non-linearity response of WH-ADCP compass was found with amplitude of ~20 degrees under the condition which the horizontal magnetic intensity is higher than 3000 nT. However, we can conclude that the heading data from WH-ADCP would be useful with an accuracy of 5 degrees after understanding the non-linear response of each compass.

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