THE EFFECTS OF CHANNELS AND SHOALS ON EXCHANGE BETWEEN THE CHESAPEAKEBAY AND THE ADJACENT OCEAN

Citation
A. Vallelevinson et Kmm. Lwiza, THE EFFECTS OF CHANNELS AND SHOALS ON EXCHANGE BETWEEN THE CHESAPEAKEBAY AND THE ADJACENT OCEAN, J GEO RES-O, 100(C9), 1995, pp. 18551-18563
Citations number
42
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Oceanografhy
Journal title
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
ISSN journal
2169-9275 → ACNP
Volume
100
Issue
C9
Year of publication
1995
Pages
18551 - 18563
Database
ISI
SICI code
2169-9275(1995)100:C9<18551:TEOCAS>2.0.ZU;2-G
Abstract
The role of bathymetric changes in determining the transport of water and salt in the lower Chesapeake Bay (LCB) was investigated using high -resolution acoustic Doppler current profiler (ADCP) and conductivity- temperature-depth profiles. A cross-channel transect was repeated eigh t times during neap tides on October 6-7, 1993, which illustrated the lateral structure of the longitudinal and transverse flow fields and t he intratidal variations in the flow structure across the LCB. Amplitu de and phase of the M(2) tidal component, as well as the mean flow vel ocity, were calculated using least squares fitting at every point of a uniform grid obtained from the ADCP data. The results differ from the classical two-layer pattern of estuarine circulation modified by Cori olis effects but are consistent with recent hydrographic observations. Semidiurnal flow was highest over the navigational channels, and late ral gradients were strongest in regions of sharp bathymetric changes. The phase lag of the semidiurnal flow also showed lateral and vertical gradients that represented advances at the bottom with respect to the surface and over the shoals in relation to the channels. The section of the water column measured indicated a mean outflow of 0.7x10(4) m(3 )/s and a mean inflow of 1.3x10(4) m(3)/s. The apparent gain of water by the estuary during the period of observation can be explained by me teorologically forced net barotropic inflow. The depth-averaged mean l ongitudinal flow consisted of inflow in the navigational channels and outflow over the shoals. The mean transverse flow showed near-surface convergence over the channels. We propose a possible explanation for t he observed flow and density structure as follows: the barotropic and baroclinic forcing interact with the bathymetry to extend the inflow f rom the bottom to the surface, thereby inducing a transverse circulati on that yields near-surface convergence over the channels.