抄録
Characteristics about seawater exchange of Ago Bay were investigated by field measurements. The measurements were carried out 3 times from August 2003 to March 2004. The flow velocity distribution in transverse cross sections of the Bay was measured by the ADCP (Acoustic Doppler Current Profiler), which was equipped with an observation vessel. The statistical analysis based on the least square method was utilized to decompose the measured velocity to tidal and non-tidal components. The non-tidal parts were decomposed further to extract the density current and the tidal residual current components. The forms of seawater exchange differed for every measurements. On the 1st measurement on August, the seawater exchange due to the normal estuarine circulation prevailed, while on the 2nd measurement on the end of September, the increment of salinity at the bay mouth, which was caused by cooling of sea surface and vertical mixing, generated the vertical circulation and played the principal role of the seawater exchange. On the 3rd measurement on March, another mechanism of seawater exchange due to density front worked at the bay mouth. It was found that the volume flow rates of the seawater exchange took almost the same magnitudes, although the phenomena were different each other.
