Tidal influence on high frequency harbor oscillations in a narrow entrance bay
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High frequency sea level oscillations at Wells Harbor (Maine, Northeastern US), with periods in the range of several tens of minutes, display a tidally modulated response. During low tides, these sea level oscillations reach amplitudes of 10–20 cm, while during high tides they are significantly smaller. Wells Harbor is located in a low lying area with a tidal range of about 2 m and is connected to the open ocean through a narrow channel. Thus, the extent and depth of the bay significantly vary over a tidal cycle. This changing geometry determines both the resonant periods and the amplification factor of the bay. Numerical results confirm the link between observed variability and these specific topographic features. Results imply that when exceptionally energetic long waves reach the Wells Harbor entrance (as in the case of a tsunami or meteotsunami) the expected response will be significantly stronger during low tide than during high tide. Although mean sea level would be lower in the former case, the currents inside the bay would be stronger and potentially more dangerous. This tidally modulated response could be extrapolated to other sites with similar topographic characteristics.
KeywordsSeiche Meteotsunami Wells harbor Tides
We would like to thank the NOAA and the Gulf of Maine Research Institute, in particular John Jensenius and Linda Mangum, for their help in the acquisition of the data. Tide gauge data were obtained from the NOAA CO-OPS website at http://opendap.co-ops.nos.noaa.gov/axis/webservices. This work was partially performed within the NOAA/NWS project “Toward a meteotsunami warning system along the U.S. coastline (TMEWS),” Award No. NA11NWS4670005. The work of A. Amores has been funded by a JAE-PreDoc Grant from Consejo Superior de Investigaciones Científicas (CSIC) and co-funded by Programa Operativo FSE 2007–2013. M. Marcos acknowledges a “Ramon y Cajal” contract funded by the Spanish Ministry of Economy.
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