Estuary water quality is greatly influenced by the ocean, particularly the influences from ocean currents. Ocean currents have a very large thermal capacity, especially the Kuroshio and Oyashio. Thus, anomalous ocean currents generated anomalous estuarine water quality. This means that to consider the local bay's water quality needs to consider the global water currents (and quality). The change of sea level distribution is considered to be mainly controlled by distributions of high and low pressure systems. The water temperature around the Japanese coast is well controlled with the North West Pacific sea level Oscillation (NWPO) strongly influenced by the Aleutian Low pattern. The variation of sea level at most west Japan (Okinawa), which. is southwest part of NWPO is considered to be well correlated with movement of ocean current.