Abstract

Water velocity data from acoustic Doppler current profilers and electromagnetic current meters deployed at six separate locations across the entrance of the Chesapeake Bay from mid-April to early July of 1999 and from early September to mid-November of 1999 were used in conjunction with wind velocity and sea level records to describe the characteristics of the wind-induced subtidal volume exchange between the bay and the adjacent continental shelf. The current measurements were used to estimate volume fluxes associated with the local and remote wind-induced bay-shelf exchange over time scales of 2–3 days. The results show that at these relatively short subtidal time scales (1) the net flux integrated over the entrance to the estuary adequately describes the unidirectional (either inflow or outflow over the entire cross-section) barotropic volume flux associated with the coastally forced remote wind effect, (2) during the first deployment there is always a bi-directional exchange pattern (inflow and outflow existing simultaneously over different parts of the cross-section) superimposed on the sectionally integrated unidirectional exchange, (3) the magnitude of the bi-directional transport associated with the local wind effect may be a significant fraction of the unidirectional transport associated with the remote wind effect, and (4) the relative importance of the local wind effect in producing estuary-shelf exchange changes appreciably with season, depending on the characteristic frequency of the wind events and the degree of stratification in the estuary.

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