Tidal current measurement in the Kurushima Strait by the reciprocal sound transmission method

Abstract

The tidal current in the Kurushima Strait of the Seto Inland Sea, Japan was successfully measured during July–August 2009 (36 days) among the three acoustic stations (KR4, KR5 and KR6), located on both sides of the strait. The travel time differences for the two sound transmission lines KR4–KR5 and KR4–KR6 are converted into the range-averaged currents along the transmission lines. The hourly mean of the range-averaged currents varied in the range from −31.1 to 53.8 cm/s for the KR4–KR5 and in the range from −45.4 to 48.7 cm/s for the KR4–KR6 with the error bars of 5.0 cm/s and 6.6 cm/s, respectively. The hourly mean along-line currents are further transformed into the geophysical coordinates with the variation range from −99.1 to 91.6 cm/s and the mean current of −6.6 cm/s for the eastward component VE, and that of (−54.2–31.5) cm/s and the mean current of −7.6 cm/s for the northward component VN. The cross-line volume transport varied in the range of (−17.928 to +17.569) × 104 m3/s, resulting in the mean westward transport of 0.727×104 m3/s. This mean transport reaches a significant level over the error bar of 0.474×104 m3/s.