A Comparison of Bulk Estuarine Turnover Timescales to Particle Tracking Timescales Using a Model of the Yaquina Bay Estuary

Lemagie, Emily; Lerczak, James A.

doi:10.1007/s12237-014-9915-1

Cited by 45 publications

(37 citation statements)

References 49 publications

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“…The e ‐folding time for particles to leave the surf zone also yields a flushing time and, with , an exchange velocity. This velocity is well correlated with

U_{ex}^{normalr} (L_{sz})

( r 2 =0.76) with a regression slope of 5 due to particle recirculation typically accounted for by an exchange factor [ Lemagie and Lerczak , ]. Thus,

U_{ex}^{normalr} (L_{sz})

is representative of the surf zone flushing rate and the scalings allow the surf zone flushing time to be quantified via .…”

Section: Discussionmentioning

confidence: 96%

“…Analogous to estuarine flushing time [ MacCready , ; Lemagie and Lerczak , ], a bulk surf zone flushing time is useful in understanding surf zone to inner shelf material exchange. Here the transient rip current surf zone flushing time

T_{f}^{r}

is defined as the time required to replace the surf zone area ( A sz = h b L sz /2),

T_{f}^{r} = \frac{A_{sz}}{h_{normalb} U_{ex}^{normalr} (L_{sz})} = \frac{1}{2} \frac{L_{sz}}{U_{ex}^{normalr} (L_{sz})} .

…”

Section: Discussionmentioning

confidence: 99%

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A self‐similar scaling for cross‐shelf exchange driven by transient rip currents

Suanda

Feddersen

2015

Geophysical Research Letters

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Transient rip currents, episodic offshore flows from the surf zone to the inner shelf, present a recreational beach hazard and exchange material across the nearshore ocean. The magnitude and offshore extent of transient rip‐current‐induced exchange and its relative importance to other inner shelf exchange processes are poorly understood. Here 120 model simulations with random, normally incident, directionally spread waves spanning a range of beach slopes and wave conditions show that the transient rip current exchange velocity is self‐similar. The nondimensional exchange velocity, surf zone flushing time, and cross‐shore decay length scale are scaled by beach slope and wave properties, depending strongly on wave directional spread. Transient rip‐current‐driven exchange can be compared to other cross‐shelf exchange processes. For example, transient rip‐current‐driven exchange is stronger than wave‐induced Stokes‐drift‐driven exchange up to six surf zone widths from shore.

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“…The e ‐folding time for particles to leave the surf zone also yields a flushing time and, with , an exchange velocity. This velocity is well correlated with

U_{ex}^{normalr} (L_{sz})

( r 2 =0.76) with a regression slope of 5 due to particle recirculation typically accounted for by an exchange factor [ Lemagie and Lerczak , ]. Thus,

U_{ex}^{normalr} (L_{sz})

is representative of the surf zone flushing rate and the scalings allow the surf zone flushing time to be quantified via .…”

Section: Discussionmentioning

confidence: 96%

T_{f}^{r}

is defined as the time required to replace the surf zone area ( A sz = h b L sz /2),

T_{f}^{r} = \frac{A_{sz}}{h_{normalb} U_{ex}^{normalr} (L_{sz})} = \frac{1}{2} \frac{L_{sz}}{U_{ex}^{normalr} (L_{sz})} .

…”

Section: Discussionmentioning

confidence: 99%

A self‐similar scaling for cross‐shelf exchange driven by transient rip currents

Suanda

Feddersen

2015

Geophysical Research Letters

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“…This implies a greater sensitivity of s e to river flow than the mean age and residence time. Journal of Geophysical Research: Oceans 10.1002/2015JC011181 Lemagie and Lerczak [2014] investigated the sensitivity of the tracer turnover time and particle flushing time using idealized hydrodynamic scenarios of Yaquina Bay, Oregon. Using a slightly different methodology than that described here, they showed that particle flushing time was more sensitive to river flow than the tracer turnover time and concluded that the tracer turnover time was not representative of transport in that particular system.…”

Section: Relationship With Freshwater Advective Timementioning

confidence: 99%

Time scales in Galveston Bay: An unsteady estuary

et al. 2016

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Estuarine time scales including the turnover, particle e‐folding time, the age (calculated with a passive tracer), and residence time (calculated with Lagrangian particles) were computed using a three‐dimensional hydrodynamic model of Galveston Bay, a low‐flow, partially stratified estuary. Time scales were computed during a time period when river flow varied by several orders of magnitude and all time scales therefore exhibited significant temporal variability because of the unsteadiness of the system. The spatial distributions of age and residence time were qualitatively similar and increased from 15 days in a shipping channel to >45 days in the upper estuary. Volume‐averaged age and residence time decreased during high‐flow conditions. Bulk time scales, including the freshwater and salinity turnover times, were far more variable due to the changing river discharge and salt flux through the estuary mouth. A criterion for calculating a suitable averaging time is discussed to satisfy a steady state assumption and to estimate a more representative bulk time scale. When scaled with a freshwater advective time, all time scales were approximately equal to the advective time scale during high‐flow conditions and many times higher during low‐flow conditions. The mean age, Lagrangian residence, and flushing times exhibited a relationship that was weakly dependent on the freshwater advective time scale demonstrating predictability even in an unsteady, realistic estuary.

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“…The TEF may hold promise for better understanding the exchange process in estuaries, for instance by comparing the TEF with a Lagrangian residual framework (Zimmerman 1979;Feng et al 2008;Feng 2011, 2014;Lemagie and Lerczak 2014).…”

Section: B Isohaline Frameworkmentioning

confidence: 99%

Mechanisms of Tidal Oscillatory Salt Transport in a Partially Stratified Estuary

Wang

Geyer

Engel

et al. 2015

Journal of Physical Oceanography

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Tidal oscillatory salt transport, induced by the correlation between tidal variations in salinity and velocity, is an important term for the subtidal salt balance under the commonly used Eulerian method of salt transport decomposition. In this paper, its mechanisms in a partially stratified estuary are investigated with a numerical model of the Hudson estuary. During neap tides, when the estuary is strongly stratified, the tidal oscillatory salt transport is mainly due to the hydraulic response of the halocline to the longitudinal variation of topography. This mechanism does not involve vertical mixing, so it should not be regarded as oscillatory shear dispersion, but instead it should be regarded as advective transport of salt, which results from the vertical distortion of exchange flow obtained in the Eulerian decomposition by vertical fluctuations of the halocline. During spring tides, the estuary is weakly stratified, and vertical mixing plays a significant role in the tidal variation of salinity. In the spring tide regime, the tidal oscillatory salt transport is mainly due to oscillatory shear dispersion. In addition, the transient lateral circulation near large channel curvature causes the transverse tilt of the halocline. This mechanism has little effect on the cross-sectionally integrated tidal oscillatory salt transport, but it results in an apparent left-right cross-channel asymmetry of tidal oscillatory salt transport. With the isohaline framework, tidal oscillatory salt transport can be regarded as a part of the net estuarine salt transport, and the Lagrangian advective mechanism and dispersive mechanism can be distinguished.

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A Comparison of Bulk Estuarine Turnover Timescales to Particle Tracking Timescales Using a Model of the Yaquina Bay Estuary

Cited by 45 publications

References 49 publications

A self‐similar scaling for cross‐shelf exchange driven by transient rip currents

A self‐similar scaling for cross‐shelf exchange driven by transient rip currents

Time scales in Galveston Bay: An unsteady estuary

Mechanisms of Tidal Oscillatory Salt Transport in a Partially Stratified Estuary

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