Date of Award

Summer 2006

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Ocean and Earth Sciences

Committee Director

Larry P. Atkinson

Committee Member

Chester E. Grosch

Committee Member

Arnoldo Valle-Levinson

Call Number for Print

Special Collections LD4331.O35 P56 2006

Abstract

Time series of current velocity from 6 stations at the Chesapeake Bay entrance were used to study the variability of tidal currents. Particular emphasis was placed on the semidiurnal tidal currents, which explains ~ 70% of the variability of tidal currents. Four different deployments that spanned more than one year showed that the vertical structure of the semidiurnal tidal currents vary seasonally in response to changes in water column stratification. Under destratified conditions favored by wind forcing, the semidiurnal tidal currents rotated cyclonically throughout the water column, thus emulating a Kelvin wave. In contrast, during stratified conditions the tidal currents rotated anticyclonically in the upper water column and cyclonically in the lower water column, within the bottom layer influenced by friction. Therefore, it is postulated that wind forcing plays a crucial influence in the semidiurnal tidal current properties at the Chesapeake Bay entrance. The measurements also showed that the generation of overtides namely fourthdiurnal tides, appeared more markedly over shallow (<10 >m) areas. The overtides distribution was consistent with larger tidal amplitude to total depth ratios and was a consequence of larger distortions of the tidal signal. The role of tides as a forcing mechanism for the exchange between the estuary and the adjacent continental shelf was also evaluated. In this sense, tidal currents were used to determine temporally integrated volume fluxes at the entrance to the bay. The tidal volume fluxes were of order 105 m3s-1 and were comparable to those obtained from tidal prism estimates. In addition, the volume fluxes generated by overtides were of the same order of magnitude as subtidal volume fluxes. This points to the importance of overtidal volume fluxes in this estuary.

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DOI

10.25777/vfa7-4467

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