A simple model of estuarine subtidal fluctuations forced by local and remote wind stress

Garvine, Richard W.

doi:10.1029/jc090ic06p11945

Cited by 131 publications

(115 citation statements)

References 7 publications

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“…In a model study of estuary-shelf interaction driven by wind forcing, Janzen found that the vertically averaged estuarine current responded to the remote action of the wind field over the shelf in forcing sea level change in accordance with the simple, barotropic model of Garvine [1985]. Nevertheless, the depth-dependent current responded strongly to the local wind along the estuary's longitudinal axis with the upper level currents following the wind and the lower level flowing counter to the wind.…”

Section: Delivery Of Fresh Water To the Shelfmentioning

confidence: 99%

Fresh water delivery to the continental shelf and subsequent mixing: An observational study

Sanders¹,

Garvine²

2001

J. Geophys. Res.

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Abstract. We address two questions related to buoyant coastal discharge: (1) What agents control the delivery of estuarine fresh water to the shelf?. (2) How is this fresh water mixed with shelf water? Our subject was the Delaware Coastal Current, the buoyancy driven current originating in the Delaware estuary. The delivery of freshwater to the shelf at subtidal frequencies is controlled by two forcing agents: upland freshwater discharge into the estuary and the component of the wind parallel to the estuarine axis. The mean current we observed in the source region showed a strong decline in speed and large counterclockwise veering with increased depth. These variations in the mean current are best explained by thermal wind shear. From the moored instrument records we found evidence that in the source region mixing events of several hours duration are common at tidal frequencies when the local Richardson number Ri drops to a minimum level below 1/4. Furthermore, there is a pronounced modulation of this minimum level for Ri controlled by the action of coastal Ekman circulation. Data from the satellitetracked drifters show the striking difference between the coastal current configuration during downwelling and upwelling events. During downwelling the flow is downshelf and weakly onshore with particle trajectories orthogonal to the mean horizontal salinity gradient. In contrast, during upwelling the flow is strongly offshore and somewhat upshelf with particle trajectories down the mean salinity gradient, implying rapid mixing of plume water with shelf water. Corresponding values for horizontal dispersion of plume water showed modest values for both the along-shelf and across-shelf directions under downwelling but a very large value for the across-shelf dispersion under upwelling. We conclude that wind stress, acting through the mediation of the strain field produced by coastal upwelling circulation, is the primary means for completing the mixing of fresh water within the plume with shelf water.

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Section: Delivery Of Fresh Water To the Shelfmentioning

confidence: 99%

Fresh water delivery to the continental shelf and subsequent mixing: An observational study

Sanders¹,

Garvine²

2001

J. Geophys. Res.

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“…Many studies appear to suggest that the answer may be different depending on the particular estuaries involved. However, Garvine [1985] has used an analytical model to show by scaling arguments that the shormess of most estuaries relative to the subtidal estuarine wavelengths should result in the dominance of the remote effect for both sea level and sectionally averaged current fluctuations in the estuaries. Does this mean that the remote effect is the dominant factor for determining the subtidal fluctuations in the transport and distribution of suspended or dissolved matters in the estuaries?…”

Section: Paper Number 98jc01476mentioning

confidence: 99%

On the relative importance of the remote and local wind effects to the subtidal variability in a coastal plain estuary

Wong¹,

Moses-Hall²

1998

J. Geophys. Res.

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Abstract. A set of month-long sea level and current measurements is used to examine the subtidal variability in the Delaware estuary and assess the relative importance of remote and local wind effects on the observed subtidal variability. The evidence indicates that the remote wind effect, through the impingement of coastal sea level at the mouth of the estuary, is more importam than the local wind effect in producing the subtidal sea level fluctuations in the interior of the estuary. On the other hand, the local wind effect dominates over the remote wind effect in producing the observed subtidal current fluctuations at the mooring site. It appears that the remote wind effect is important to the sectionally averaged subtidal transport into or out of the estuary. However, the local wind effect may be more important than the remote wind effect in producing the subtidal currents at any given point along the estuary's cross section. The spatial structure associated with the local wind-induced circulation is very important to the long term transport and distribution of waterborne material.

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“…Boicourt et al (1999) cite a quarter-wave seiche that causes the oscillations in the 2-day band as the dominant subtidal variation in bay circulation, evident during all times of year. Field data (Wang and Elliot, 1978) and computer models (Garvine, 1985) independently show that the relative impact of local winds on water level increases linearly with distance from the bay mouth.…”

Section: Introductionmentioning

confidence: 99%

“…Weekly to seasonal net nontidal estuarine circulation in Chesapeake Bay is due to buoyancy differences between freshwater input from the basin and saltwater input from the sea (Schubel and Prichard, 1986). Hourly to weekly variations in circulation are caused by astronomical tides coupled with subtidal water level variations caused by barometric pressure gradients and local wind forcing in the estuary as well as remote wind forcing out on the coastal ocean (Blumberg, 1977;Wang and Elliot, 1978;Garvine, 1985;Paraso and Valle-Levinson, 1996;Boicourt et al, 1999). Several field monitoring campaigns ranging in duration from 1-13 months have revealed that winds blowing along the longitudinal axis (south-north) of the bay generate free oscillations in water level with periods of 2-4 days (Wang, 1979a, Wang, 1979bHamilton and Boicourt, 1983;Olson, 1986;Vieira, 1986;Chuang and Boicourt, 1989).…”

Section: Introductionmentioning

confidence: 99%

Hydrometeorological controls on water level in a vegetated Chesapeake Bay tidal freshwater delta

Pasternack

Hinnov

2003

Estuarine, Coastal and Shelf Science

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ABSTRACT.Wind vectors, watershed discharge, and subestuarine water levels were monitored in a vegetated delta at the head of the Bush River, an upper Chesapeake Bay tributary in Maryland, during an El Niño/La Niña cycle 1995-1996 to investigate hydrometeorological processes that affect the tidal freshwater ecosystem located there. Time series of these processes were analyzed in both the time and frequency domains using such methods as flood frequency analysis, harmonic analysis, averaged and evolutionary power spectral analysis, and coherency spectral analysis. Wind speed variations with periods of 3-4 and 7 days were found to have both high spectral power and high statistical significance. The frequencies of these variations fluctuated over weeks to months and the amplitudes modulated seasonally, but the variations persisted interannually. Significantly greater subtidal wind speed variations in the prinicipal wind direction occurred during the cold and stormy La Niña winter of 1996 relative to the warm and dry El Niño winter of 1995. Data from 5 hurricanes occurring in the region during the study provided high-resolution snapshots of the mechanisms revealed by the time series analyses.Water level quickly responded to S-N directed wind speed fluctuations during the aperiodic hurricanes, illustrating the strong coupling between wind and water levels in this system. The magnitude of the response was large enough to determine the extent and duration of flooding over tens of hectares in important intertidal marsh habitats. Subtidal water level variations were greater during the La Niña period. During El Niño conditions, the E-W wind component played a larger role than during the La Niña period. Variations in local watershed discharge as well as Susquehanna River outflow had no measurable impact on water levels in the upper reaches of the Bush River tributary during the study.

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A simple model of estuarine subtidal fluctuations forced by local and remote wind stress

Cited by 131 publications

References 7 publications

Fresh water delivery to the continental shelf and subsequent mixing: An observational study

Fresh water delivery to the continental shelf and subsequent mixing: An observational study

On the relative importance of the remote and local wind effects to the subtidal variability in a coastal plain estuary

Hydrometeorological controls on water level in a vegetated Chesapeake Bay tidal freshwater delta

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