Tidal interaction of stratified flow in a drowned valley on the Sanriku ria coast

The mooring observations were conducted at two points of the north and south mouth in a drowned valley on the Sanriku ria coast, Japan, from 2012 through May 2014. Two current systems were deployed at the bottom, comprising an Acoustic Doppler Current Profiler and a temperature-salinity-depth sensor at the surface and the bottom. Observations have revealed a broad variety of different interactions depending upon the strength of tidal forcing. Tidal and shorter waves strengths with non-periodic frequencies. The astronomical tide explained these non-periodic frequencies. The semi-diurnal and the shorter periods were detected to occur simultaneously. The result probably implies that semi-diurnal phenomena would generate the shorter one. Diurnal fluctuations were well reproduced by predicted tidal waves but semi-diurnal one was not. The tidal flow likely slackens, subsequently evolving into travelling internal bores or surges. On-going numerical experiment supported our observational results. Related analyses will show the detail phenomena above using the observation and numerical modeling, with a discussion of a propagating system of barotropic and baroclinic tidal waves and vertical propagations of internal waves.