Seasonal Behavior of the Internal Tide and Associated Water Temperature in Genka Bay, Okinawa, Japan.

Sustainability of coastal aquatic resources is deeply associated with several hydrophysical processes, where internal tide is one of the key processes. Seasonal variation in the characteristics of the internal tidal currents and their associated change in water temperature was observed to take part in managing the coastal aquatic systems in Genka Bay, Okinawa, Japan. Profiling and mooring measurements were carried out in three sites of the study area during summer and winter. The study results show that the depth-averaged current flows nearly parallel to the coastline during summer and winter. There is also an existence of a cross-shore internal tidal current according to the vertical structure of the horizontal current in both seasons. This current influences the bottom water temperature transmission from offshore to nearshore bottom water and changes the vertical temperature profile even of nearshore regions and thereby establishes a unique cooling system. This influence is stronger in summer than in winter due to the seasonal variations in the intensity of the propagated internal tidal currents. Spectra of the baroclinic and bottom water temperature confirm the existence of the semidiurnal constituent-dominated internal tides as well as their seasonal and shoreward variations in Genka Bay. [ABSTRACT FROM AUTHOR]