Increase in water exchange ratio due to a decrease in tidal amplitude in Ariake Bay, Japan

The year-to-year variations in the water exchange ratio and the tidal amplitude in Ariake Bay, Japan, were investigated using observed river discharge, salinity and tide gauge data. The water exchange ratio between Ariake Bay and the open ocean has increased from the early to the late 1990s due to the intensification of the estuarine circulation in the bay. The intensification of the estuarine circulation in Ariake Bay has resulted from a decrease in the tidal amplitude there.