Secondary circulation in a region of flow curvature: Relationship with tidal forcing and river discharge

Chant, Robert J.

doi:10.1029/2001jc001082

Cited by 102 publications

(77 citation statements)

References 25 publications

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“…4, lower panel). Under a mere interaction of tidal flows with curvature, centrifugal accelerations should have been stronger at spring tides and would have produced surface flow away from the cape and bottom flow toward the cape (Chant 2002). This was not the case in our observations (Fig.…”

Section: Station Acontrasting

confidence: 67%

“…This response developed, however, over a shallow (<7 m) location at the Chesapeake Bay entrance where the mean and subtidal along-estuary flows were also unidirectional. In order to examine whether this response also holds for a deeper location, we applied the same analysis to the Chesapeake Channel location (station B), where along-estuary mean and subtidal flows exhibited bidirectional structure (ValleLevinson et al 1998;2002;Fig. 3, lower panel).…”

Section: Station Amentioning

confidence: 98%

“…Chant (2002) found that it strengthens during spring relative to neap tides because of increased centrifugal accelerations. He also found that secondary circulations are weakened during periods of increased river discharge and stratification.…”

Section: Introductionmentioning

confidence: 96%

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Subtidal variability of transverse flow off a cape

Valle‐Levinson¹,

Brown²

2003

Ocean Dynamics

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Time series of velocity profiles at two Chesapeake Bay entrance sites were used to characterize the subtidal variability of transverse flows off a cape. A shallow sampling site was located near Cape Henry over 6 m of water and separated from a deep site, 20 m deep, by a distance of $4 km. The velocity profiles showed that wind-induced subtidal variations in general masked curvature effects (centrifugal accelerations) that may produce secondary circulation associated with tidal flow around a cape. Such secondary circulation, consisting of flow away from the cape at surface and toward the cape at depth, was observed only during periods of weak winds. Most of the time, transverse flows were unidirectional throughout the water column and moved in opposite directions at the two sites examined. This caused convergence of transverse flow between the two sites under the influence of northerly winds and divergence of transverse flow with southwesterly winds. In addition to unidirectional and curvature-induced secondary flows, other modes of subtidal variability consisted of (1) two-layered responses with surface flow toward the cape, and (2) three-layered responses. These two-and three-layered structures were observed more frequently at the deep site, where greater stratification is expected, than at the shallow site.

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Section: Station Acontrasting

confidence: 67%

Section: Station Amentioning

confidence: 98%

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Subtidal variability of transverse flow off a cape

Valle‐Levinson¹,

Brown²

2003

Ocean Dynamics

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“…This transverse shear creates a lateral salinity gradient as well as lateral shear in along-channel velocity, with faster ebb velocities and lower salinities on the south side of the channel. The opposing lateral baroclinic pressure gradient might be expected to shut down the curvature-induced lateral circulation [Seim and Gregg, 1997;Chant, 2002]. Curvature-induced lateral circulation depends on deviations from the depth-averaged velocity [Kalkwijk and Booij, 1986;Geyer, 1993].…”

Section: Lateral Structurementioning

confidence: 99%

Structure, variability, and salt flux in a strongly forced salt wedge estuary

Ralston¹,

Geyer²,

Lerczak³

2010

J. Geophys. Res.

130

138

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[1] The tidally varying circulation, stratification, and salt flux mechanisms are investigated in a shallow salt wedge estuary where fluvial and tidal velocities are large and the steady baroclinic circulation is comparatively weak. The study integrates field observations and numerical simulations of the Merrimack River estuary. At moderate to high discharge the estuary is short and highly stratified, while at lower discharges it shifts to a longer, more weakly stratified estuary; the transition occurs when the length of the salinity intrusion is similar to the tidal excursion. The Merrimack is highly variable at tidal time scales owing to the advection and mixing of a bottom salinity front. Salt flux is predominantly due to tidal processes rather than steady baroclinic or bathymetric shear. Tidal pumping is important near the mouth, but inside the estuary salt flux is due to tidal asymmetries in the elevation and thickness of the halocline that depend on the tidal amplitude and river discharge. Conditions in the Merrimack, including the salinity intrusion length and stratification, vary more with event to seasonal shifts in river discharge than with spring-neap changes in tidal amplitude. An unstructured grid hydrodynamic model is used to simulate conditions in the Merrimack and model results are compared quantitatively against field observations. The model achieves a high skill against time series of water level, salinity, and velocity and captures the spatial structures of salinity, velocity, and salt flux observed in along-and across-estuary transects. High model skills depend on accurate and well-resolved grid bathymetry and low background vertical and horizontal diffusivities.

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“…Further possible contributions to the estuarine circulation arise from channel convergence (e.g., Ianniello 1979;Burchard et al 2014), curvature (Geyer 1993;Chant 2002;Becherer et al 2015), wind (Scully et al 2005;Waterhouse et al 2013), and trapping due to complex geometry (Lacy et al 2003;Giddings et al 2012). The reviews by MacCready and Geyer (2010) and Geyer and MacCready (2014) contain comprehensive summaries of estuarine circulation processes.…”

Section: Introduction a Estuarine Circulationmentioning

confidence: 99%

Impact of the Depth-to-Width Ratio of Periodically Stratified Tidal Channels on the Estuarine Circulation

Schulz

Schuttelaars

Gräwe

et al. 2015

Journal of Physical Oceanography

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The dependency of the estuarine circulation on the depth-to-width ratio of a periodically, weakly stratified tidal estuary is systematically investigated here for the first time. Currents, salinity, and other properties are simulated by means of the General Estuarine Transport Model (GETM) in cross-sectional slice mode, applying a symmetric Gaussian-shaped depth profile. The width is varied over four orders of magnitude. The individual along-channel circulation contributions from tidal straining, gravitation, advection, etc., are calculated and the impact of the depth-to-width ratio on their intensity is presented and elucidated. It is found that the estuarine circulation exhibits a distinct maximum in medium-wide channels (intermediate depth-towidth ratio depending on various parameters), which is caused by a maximum of the tidal straining contribution. This maximum is related to a strong tidal asymmetry of eddy viscosity and shear created by secondary strain-induced periodic stratification (2SIPS): in medium channels, transverse circulation generated by lateral density gradients due to laterally differential longitudinal advection induces stable stratification at the end of the flood phase, which is further increased during ebb by longitudinal straining (SIPS). Thus, eddy viscosity is low and shear is strong in the entire ebb phase. During flood, SIPS decreases the stratification so that eddy viscosity is high and shear is weak. The circulation resulting from this viscosity-shear correlation, the tidal straining circulation, is oriented like the classical, gravitational circulation, with riverine outflow at the surface and oceanic inflow close to the bottom. In medium channels, it is about 5 times as strong as in wide (quasi onedimensional) channels, in which 2SIPS is negligible.

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Secondary circulation in a region of flow curvature: Relationship with tidal forcing and river discharge

Cited by 102 publications

References 25 publications

Subtidal variability of transverse flow off a cape

Subtidal variability of transverse flow off a cape

Structure, variability, and salt flux in a strongly forced salt wedge estuary

Impact of the Depth-to-Width Ratio of Periodically Stratified Tidal Channels on the Estuarine Circulation

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