Resonance and sea level variability in Chesapeake Bay |
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| Institution: | 1. Horn Point Laboratory, University of Maryland Center for Environmental Science, P.O. Box 775, Cambridge, MD 21613, USA;2. Institute of Ocean Sciences, Fisheries and Oceans Canada, P.O. Box 6000, Sidney, British Columbia, Canada V8L 4B2;1. State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China;2. Sino-Australian Research Centre for Coastal Management, The University of New South Wales, Canberra, ACT 2610, Australia;3. Key Laboratory of Physical Oceanography, Ministry of Education, at Ocean University of China, Qingdao 266100, China |
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| Abstract: | A numerical model is used to determine the resonant period and quality factor Q of Chesapeake Bay and explore physical mechanisms controlling the resonance response in semi-enclosed seas. At the resonant period of 2 days, the mouth-to-head amplitude gain is 1.42 and Q is 0.9, indicating that Chesapeake Bay is a highly dissipative system. The modest amplitude gain results from strong frictional dissipation in shallow water. It is found that the spatial distribution of energy dissipation varies with forcing frequency. While energy at tidal frequencies is dissipated around topographic hotspots distributed throughout the Bay, energy dissipation at subtidal frequencies is mainly concentrated in the shallow-water lower Bay. An analytic calculation shows that the bottom friction parameter is much larger in Chesapeake Bay than in other coastal systems with strong resonance response. The model-predicted amplitude gains and phase changes agree well with the observations at semidiurnal and diurnal tidal frequencies. However, the predicted amplitude gain in the resonant frequency band (34–54 h period) falls below that inferred from band-passed sea level observations. This discrepancy can be attributed to the local wind forcing which amplifies the sea level response in the upper Bay. The model is also used to show that rising sea levels associated with global warming will shift the resonance period of Chesapeake Bay closer to the diurnal tides and thus exacerbate flooding problems by causing an increase in tidal ranges. |
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