Mechanisms and variability of salt transport in partially-stratified estuaries

Bowen, Melissa

doi:10.1575/1912/2130

Cited by 14 publications

(8 citation statements)

References 53 publications

(191 reference statements)

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“…The exchange of salt advances the phase of the salinity in regions with slower tidal flows and retards it in region with higher flows, leading to an up‐gradient salt transport in regions of slower flows and down‐gradient in regions of faster flows. The appearance of up‐gradient tracer transport has been documented in bottom boundary layers [ Larsen , 1977; Ou et al , 2000] and similar principles apply to the transverse dimension [ Bowen , 2000].…”

Section: Resultsmentioning

confidence: 99%

Salt transport and the time‐dependent salt balance of a partially stratified estuary

2003

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[1] The transport of salt along the channel of an estuary determines the length of the saline intrusion and provides bounds on the transfer of other substances. Observations of salt transport have been hampered by a lack of long time series measurements and complexities of the sampling situation (e.g., local topography and simultaneous variations of tides, freshwater, and winds). Here we estimate salt transport at a relatively uniform section of the Hudson Estuary over a 70-day period during drought conditions. The salt balance of the estuary is also assessed by comparing salt transport at the section with surveys of total salt content in the estuary. Most salt enters the estuary in monthly pulses of estuarine salt transport (i.e., spatial variations of tidally-averaged velocity and salinity) during apogean neap tides when vertical stratification is greatest. Oscillatory salt transport (i.e., the covariance of tidally-varying velocity and salinity) is a more minor player in the salt balance and shows a surprising lack of spring-neap variation. Integrated salt transport at the section is consistent with estimates of total salt content of the estuary; however, the mismatch in magnitude of the variations indicates that the salinity intrusion is not in equilibrium within the spring-neap cycle. In contrast, the salt balance adjusts rapidly to an increase in freshwater flow at the end of the deployment. A scaling argument is derived to illustrate the adjustment of the salinity intrusion to the tides and freshwater flow. The results suggest that time dependence is an intrinsic part of the estuarine salt balance.INDEX TERMS: 4235 Oceanography: General: Estuarine processes; 4546 Oceanography: Physical: Nearshore processes; 5799 Planetology: Fluid Planets: General or miscellaneous; KEYWORDS: salt transport, salt balance, estuarine circulation, spring-neap tidal cycle Citation: Bowen, M. M., and W. Rockwell Geyer, Salt transport and the time-dependent salt balance of a partially stratified estuary,

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Section: Resultsmentioning

confidence: 99%

Salt transport and the time‐dependent salt balance of a partially stratified estuary

2003

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“…Bowen (2000) showed that this quantity is proportional to Ri e 1/3 for partially mixed estuaries in dynamical equilibrium (based on the analytical framework of Chatwin (1976)). This provides a more precise means of defining the ratio of potential energy input to mixing, taking into account the horizontal scale of salinity variation (or, in essence, the length of the estuary).…”

Section: Parameters Controlling Estuarine Stratificationmentioning

confidence: 99%

The Dynamics of Strongly Stratified Estuaries

Geyer

Ralston

2011

Treatise on Estuarine and Coastal Science

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“…The dynamics of the bottom-mixed layer and the associated stratification and shear were captured effectively by Monismith and Fong [1996], and significant shear was created at the interface due to the barotropic forcing acting on the stratified water column. A more complete model of the dynamics being examined was developed by Bowen [2000], who found that tidal asymmetry is the primary contribution to the tidally averaged shear.…”

Section: Barotropic and Baroclinic Residual Creationmentioning

confidence: 99%

Creation of residual flows in a partially stratified estuary

Stacey¹,

Burau²,

Monismith³

2001

J. Geophys. Res.

173

134

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Abstract. The creation of residual flows in estuaries is examined using acoustic Doppler current profiler data sets from northern San Francisco Bay. The data sets are analyzed using principal component analysis to examine the temporal variability of the flows which create the residual circulation. It is seen that in this periodically and partially stratified estuary the residual flows are created through a series of pulses with strong variability at the 24-hour timescale, through the interaction of shear, stratification and mixing. This interaction is captured through the use of a dimensionless number, the horizontal Richardson number (Ri•), which is developed to examine the local balance between the stratifying and destratifying forces at the tidal timescale. It is seen that Ri• is a valuable parameter in predicting the onset of the residual-creating events, with a threshold value of • 3 on ebb tides. This critical value is argued to be a threshold, above which the stratification and shear flow create a feedback effect, each further intensifying the other. This feedback results in a highly variable exchange flow which creates the estuarine residual in intermittent pulses rather than as a steady flow. Although typically attributed to baroclinic forcing, an argument is made that these pulses of residual-creating exchange flow could be created by barotropic forcing in the presence of variable stratification which is asymmetric between flood and ebb tides. This result poses a great challenge for turbulence modeling, as the timing and magnitude of stratification and shear must be correctly simulated on the tidal timescale in order to reproduce the effects seen in the data sets presented.

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Mechanisms and variability of salt transport in partially-stratified estuaries

Cited by 14 publications

References 53 publications

Salt transport and the time‐dependent salt balance of a partially stratified estuary

Salt transport and the time‐dependent salt balance of a partially stratified estuary

The Dynamics of Strongly Stratified Estuaries

Creation of residual flows in a partially stratified estuary

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