Tidal interactions with local topography above a sponge reef
Date
2011-05-27
Authors
Bedard, Jeannette
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Abstract
The interaction of tidal currents with Fraser Ridge in the Strait of Georgia, B.C., generates an internal lee-wave on each strong flood but, due to the ridge's asymmetry, not during ebbs. Just prior to lee-wave formation, a strong accelerated bottom jet forms with magnitudes up to 0.7 m s^-1 forms during barotropic tidal flows reaching 0.2 m s^-1. On the steepest slope, this jet forms directly above a rare glass sponge reef, and may prevent the sponges from being smothered in sediment by periodically resuspending and carrying it away. Both the accelerated jet and lee-wave remove tidal energy. At peak flood tide, the lee-wave has energy dissipation rates reaching 10^-5 W kg^-1 that removes energy at a rate of ~611 W m^-1, while the bottom boundary layer at the time of the accelerated jet has energy dissipation rates reaching 10^-4 W kg^-1 that removes energy at a rate of ~525 W m^-1.
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Keywords
Fraser Ridge, Tide/topography Interactions, Lee Waves