scholarly journals Decomposition of Residual Circulation in Estuaries

2014 ◽  
Vol 31 (3) ◽  
pp. 698-713 ◽  
Author(s):  
Peng Cheng
Keyword(s):  
River Discharge ◽  
Residual Circulation ◽  
Residual Currents ◽  
Physical Mechanisms ◽  
Stokes Transport ◽  
Residual Flows ◽  
Forcing Mechanisms ◽  
Horizontal Density Gradient ◽  
Stratified Estuaries ◽  
Internal Tidal Asymmetry

Abstract The residual currents in estuaries are produced by a variety of physical mechanisms. To understand the contribution of each individual mechanism to the creation of residual circulation, it is necessary to separate the effect of one particular mechanism from the others. In this study, a method based on dynamics is developed to decompose the residual circulation into individual components corresponding to different forcing mechanisms. Specifically, residual flows are partitioned based on the separate contributions by river discharge, horizontal density gradient, internal tidal asymmetry, advection, semi–Stokes transport, and wind. The method includes the effects of the earth’s rotation and can be applied for general conditions. Under the precondition that the ratio between width and length of the estuary is small, the continuity equation can be simplified such that the method only requires the data at a cross-estuary section to decompose residual currents. This makes the method practicable for real estuaries. Results from a generic numerical model are used to illustrate the decomposition method and to demonstrate its validity for weakly stratified estuaries.

The role of tides, river discharge and wind on the residual circulation of Maputo Bay

2020 ◽  
pp. 101604
Author(s):  
Paulo J. Sigaúque ◽  
Carlos A.F. Schettini ◽  
Samuel S. Valentim ◽  
Eduardo Siegle
Keyword(s):  
River Discharge ◽  
Residual Circulation

scholarly journals The nonlinMIP intercomparison project: physical basis, experimental design and analysis principles

2016 ◽  
Author(s):  
P. Good ◽  
T. Andrews ◽  
R. Chadwick ◽  
J. L. Dufresne ◽  
J. M. Gregory ◽  
...  
Keyword(s):  
Experimental Design ◽  
Model Studies ◽  
Physical Mechanisms ◽  
Non Linear ◽  
Scaling Methods ◽  
Small Set ◽  
Intercomparison Project ◽  
Forcing Mechanisms ◽  
Good Signal ◽  
Co2 Forcing

Abstract. nonlinMIP aims to quantify and understand, at regional scales, climate responses that are non-linear under CO2 forcing (mechanisms for which doubling the CO2 forcing does not double the response). Non-linear responses can be large at regional scales, with important implications for understanding mechanisms and for GCM emulation techniques (e.g. energy balance models and pattern-scaling methods). However, these processes are hard to explore using traditional experiments, explaining why they have had little attention in previous studies. Some single model studies have established novel analysis principles and some physical mechanisms. There is now a need to explore robustness and uncertainty in such mechanisms across a range of models. nonlinMIP addresses this using a simple, small set of CO2-forced experiments that are able to separate linear and non-linear mechanisms cleanly, with a good signal/noise ratio – while being demonstrably traceable to realistic transient scenarios. The design builds on the CMIP5 and CMIP6 DECK protocols, and is centred around a suite of instantaneous atmospheric CO2 change experiments, with a ramp-up-ramp-down experiment to test traceability to gradual forcing scenarios. In all cases the models are intended to be used with CO2 concentrations rather than CO2 emissions as the input. The understanding gained will help interpret the spread in policy-relevant scenario projections. Here we outline the basic physical principles behind nonlinMIP, and the method of establishing traceability from abruptCO2 to gradual forcing experiments, before detailing the experimental design and finally some analysis principles. The test of traceability from abruptCO2 to transient experiments is recommended as a standard analysis within the CMIP5 and CMIP6 DECK protocols.

Residual Circulation in and Classification of Shallow, Stratified Estuaries

1988 ◽  
pp. 21-41 ◽  
Author(s):  
D. A. Jay ◽  
J. D. Smith
Keyword(s):  
Residual Circulation ◽  
Stratified Estuaries

scholarly journals Unraveling Interactions between Asymmetric Tidal Turbulence, Residual Circulation, and Salinity Dynamics in Short, Periodically Weakly Stratified Estuaries

2021 ◽  
Vol 51 (5) ◽  
pp. 1395-1416
Author(s):  
Xiaoyan Wei ◽  
Henk M. Schuttelaars ◽  
Megan E. Williams ◽  
Jennifer M. Brown ◽  
Peter D. Thorne ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Estuarine Circulation ◽  
Salt Transport ◽  
Residual Circulation ◽  
Salinity Gradients ◽  
Model Combining ◽  
Periodic Stratification ◽  
Salt Distribution ◽  
Stratified Estuaries ◽  
First Time

AbstractAsymmetric tidal turbulence (ATT) strongly influences estuarine health and functioning. However, its impact on the three-dimensional estuarine dynamics and the feedback of water motion and salinity distribution on ATT remain poorly understood, especially for short estuaries (estuarine length ≪ tidal wavelength). This study systematically investigates the abovementioned interactions in a short estuary for the first time, considering periodically weakly stratified conditions. This is done by developing a three-dimensional semi-analytical model (combining perturbation method with finite element method) that allows a dissection of the contributions of different processes to ATT, estuarine circulation, and salt transport. The generation of ATT is dominated by (i) strain-induced periodic stratification and (ii) asymmetric bottom-shear-generated turbulence, and their contributions to ATT are different both in amplitude and phase. The magnitude of the residual circulation related to ATT and the eddy viscosity–shear covariance (ESCO) is about half of that of the gravitational circulation (GC) and shows a “reversed” pattern as compared to GC. ATT generated by strain-induced periodic stratification contributes to an ESCO circulation with a spatial structure similar to GC. This circulation reduces the longitudinal salinity gradients and thus weakens GC. Contrastingly, the ESCO circulation due to asymmetric bottom-shear-generated turbulence shows patterns opposite to GC and acts to enhance GC. Concerning the salinity dynamics at steady state, GC and tidal pumping are equally important to salt import, whereas ESCO circulation yields a significant seaward salt transport. These findings highlight the importance of identifying the sources of ATT to understand its impact on estuarine circulation and salt distribution.

scholarly journals Brief communication: The role of using precipitation or river discharge data when assessing global coastal compound flooding

2020 ◽  
Vol 20 (6) ◽  
pp. 1765-1782 ◽  
Author(s):  
Emanuele Bevacqua ◽  
Michalis I. Vousdoukas ◽  
Theodore G. Shepherd ◽  
Mathieu Vrac
Keyword(s):  
River Discharge ◽  
Large Scale ◽  
Storm Surges ◽  
High Water ◽  
Small Rivers ◽  
Water Runoff ◽  
Discharge Data ◽  
Physical Mechanisms ◽  
Catchment Size ◽  
The Impact

Abstract. Interacting storm surges and high water runoff can cause compound flooding (CF) in low-lying coasts and river estuaries. The large-scale CF hazard has been typically studied using proxies such as the concurrence of storm surge extremes either with precipitation or with river discharge extremes. Here the impact of the choice of such proxies is addressed employing state-of-the-art global datasets. Although they are proxies of diverse physical mechanisms, we find that the two approaches show similar CF spatial patterns. On average, deviations are smaller in regions where assessing the actual CF is more relevant, i.e. where the CF potential is high. Differences between the two assessments increase with the catchment size, and our findings indicate that CF in long rivers (catchment ≳5–10×103 km2) should be analysed using river discharge data. The precipitation-based assessment allows for considering local-rainfall-driven CF and CF in small rivers not resolved by large-scale datasets.

scholarly journals Intratidal and Subtidal Circulation in a Tropical Estuary during Wet Season: The Maroni, French Guiana

2019 ◽  
Vol 7 (12) ◽  
pp. 433 ◽  
Author(s):  
Lauren Ross ◽  
Aldo Sottolichio ◽  
Tanguy Maury ◽  
Sandric Lesourd ◽  
Antoine Gardel
Keyword(s):  
Pressure Gradient ◽  
River Discharge ◽  
French Guiana ◽  
Circulation Pattern ◽  
Channel Flows ◽  
Analytical Models ◽  
Wet Season ◽  
Subtidal Circulation ◽  
Channel Curvature ◽  
Forcing Mechanisms

Observations of water level, current velocity, river discharge, wind and salinity were collected in the Maroni estuary, on the border of French Guiana and Suriname during the wet season of 2018 to explore subtidal circulation patterns. Measurements are complimented by the application of analytical models with an aim to diagnose forcing mechanisms responsible for producing subtidal flows during the day of data collection and to extrapolate these findings to other time periods with variable wind and river forcing. Subtidal along-channel flows were found to be dominated by river discharge, with seaward directed velocities found throughout the channel section reaching 40 cm s − 1 . This pattern was altered with strong southwesterly winds, which produced and inverse gravitational circulation pattern despite the elevated river discharge. Secondary, or cross-channel flows, displayed a three-layer vertical structure in the main channel due to a combination of channel curvature and tidal asymmetry in the lateral baroclinic pressure gradient. The pressure gradient was produced by a salinity intrusion front that only manifested in the channel during flood tide. This is the first comprehensive study of tidal and subtidal flow dynamics in the Maroni estuary.

scholarly journals Lateral Circulation in Well-Mixed and Stratified Estuarine Flows with Curvature

2009 ◽  
Vol 39 (4) ◽  
pp. 831-851 ◽  
Author(s):  
Nicholas J. Nidzieko ◽  
James L. Hench ◽  
Stephen G. Monismith
Keyword(s):  
Pressure Gradient ◽  
Tidal Flow ◽  
Centrifugal Acceleration ◽  
Residual Currents ◽  
Momentum Budget ◽  
Current Profiler ◽  
Lateral Circulation ◽  
Layer Flow ◽  
Forcing Mechanisms ◽  
Temperature Depth

Abstract A field experiment was conducted to examine stratified and unstratified curvature-generated lateral circulation and momentum balances in an estuarine tidal channel. Conductivity, temperature, depth, and current profiler data were collected vertically and laterally across the channel at a sharp bend over a fortnightly period to measure the terms of the lateral momentum budget. Well-mixed conditions allow the development of classic two-layer helical flow around a bend. Stratification strengthens curvature-induced lateral circulation, but the development of a lateral baroclinic pressure gradient opposes the resultant motions. The spatial and temporal response of this baroclinic pressure gradient is different than centrifugal acceleration, producing a three-layer profile. As the baroclinic term becomes stronger (or as centrifugal acceleration disappears as the flow exits the bend), two-layer flow with the opposite direction from curvature occurs. In both stratified and well-mixed conditions, downstream adjustment of lateral circulation (nonlinear advective acceleration) is of leading order in the lateral momentum budget; the depth-averaged term adjusts the streamline direction, while vertical deviations from the depth average account for changes in lateral circulation. The asymmetry of forcing mechanisms on flood and ebb, because of variations in stratification and strength of tidal flow, can strongly affect net lateral transport and generation of residual currents in regions of curvature.

scholarly journals A modeling study on tides in the Port of Vancouver

2019 ◽  
Vol 2 (1) ◽  
pp. 101-125 ◽  
Author(s):  
Yongsheng Wu ◽  
Charles Hannah ◽  
Mitchell O’Flaherty-Sproul ◽  
Phillip MacAulay ◽  
Shiliang Shan
Keyword(s):  
Three Dimensional ◽  
Ocean Model ◽  
Tidal Currents ◽  
Momentum Balance ◽  
Tidal Asymmetry ◽  
Residual Circulation ◽  
Dynamic Mechanisms ◽  
Tidal Flows ◽  
Residual Flows ◽  
Good Agreement

In the present paper, tides in the port of Vancouver Harbour have been investigated with a high-resolution three-dimensional hydrodynamic model based on FVCOM (Finite Volume Community Ocean Model). The model was evaluated against field observations including tidal elevations and tidal currents, and the evaluation showed that the model was in good agreement with the observational data. Using the model, we first investigated the horizontal distributions of tides, tidal currents, and tidally induced residual circulation, and then investigated the tidal asymmetry and dynamic mechanisms of tidal flows in the harbour. The tidal residual circulation shows a strong spatial pattern, which is associated with the local coastlines and variation of topography. The tidal asymmetry in the harbour is caused by different mechanisms, not only including the traditional factors, such as residual flows, the interaction between M2 and its overtide M4, but also the interaction of principal astronomical tides of O1, K1, and M2. The momentum balance is dominated by terms of the advection and the pressure gradient in First Narrows and Second Narrows, whereas terms of the local acceleration and the Coriolis are also important in the central harbour. The spatial variations of the momentum terms are strongly associated with the local changes in coastline and topography.

scholarly journals Investigations Exploring the Use of an Unstructured-Grid, Finite-Volume Modelling Approach to Simulate Coastal Circulation in Remote Island Settings—Case Study Region, Vanuatu/New Caledonia

2021 ◽  
Vol 8 ◽  
Author(s):  
Serena Blyth Lee ◽  
Fan Zhang ◽  
Charles James Lemckert ◽  
Rodger Tomlinson
Keyword(s):  
Finite Volume ◽  
New Caledonia ◽  
Ocean Model ◽  
Water Levels ◽  
Coastal Processes ◽  
Coastal Circulation ◽  
Residual Circulation ◽  
Sea Levels ◽  
Residual Currents ◽  
Modelling Approach

Understanding coastal circulation and how it may alter in the future is important in island settings, especially in the South West Pacific, where communities rely heavily upon marine resources, and where sea level rise (SLR) is higher than the global average. In this study we explore the use of an unstructured-mesh finite-volume modelling approach to assist in filling the knowledge gaps with respect to coastal circulation in remote island locations—selecting the Vanuatu and New Caledonia archipelagos as our example study site. Past limited observations and modelling studies are leveraged to construct and verify a regional/coastal ocean model based on the Finite-Volume Community Ocean Model (FVCOM). Following verification with respect to tidal behaviour, we investigate how changes in wind speed and direction, and SLR, alter coastal water levels and coastal currents. Results showed tidal residual circulation was typically associated with flow separation at headlands and islands. Trade winds had negligible effect on water levels at the coast, however, wind-residual circulation was sensitive to both wind speed and direction. Wind-residual currents were typically strongest close to coastlines. Wind residual circulation patterns were strongly influenced by Ekman flow, while island blocking, topographic steering and geostrophic currents also appear to influence current patterns. Tidal amplitudes and phases were unchanged due to SLR of up to 2 m, while maximum current speeds altered by as much as 20 cm/s within some coastal embayments. Non-linear relationships between SLR and maximum current speeds were seen at some coastal reef platform sites. Under higher sea levels, tidal residual currents altered by less than ±2 cm/s which is relatively significant given maximum tidal residual current speeds are typically below 10 cm/s. Our findings indicate that under higher sea levels, coastal processes governing sediment transport, pollutant dispersal and larval transport are likely to alter, which may have implications for coastal environments and ecosystems. Given winds influence coastal circulation and subsequent coastal processes, changes in trade winds due to climate change may act to further alter coastal processes. It is felt that the current modelling approach can be applied to other regions to help fill critical knowledge gaps.

scholarly journals The circulation of the lower Capibaribe Estuary (Brazil) and its implications for the transport of scalars

2016 ◽  
Vol 64 (3) ◽  
pp. 263-276 ◽  
Author(s):  
Carlos Augusto França Schettini ◽  
Josineide B. de Miranda ◽  
Arnoldo Valle-Levinson ◽  
Eliane C. Truccolo ◽  
Ernesto C. Domingues
Keyword(s):  
Water Quality ◽  
Particulate Matter ◽  
Metropolitan Area ◽  
River Discharge ◽  
Spring Tide ◽  
Circulation Pattern ◽  
Residual Circulation ◽  
Suspended Particulate ◽  
Poor Water Quality ◽  
Residual Transport

Abstract The Capibaribe Estuary is a water body that crosses the Recife Metropolitan Area (RMA), one of the largest population centers in Brazil, and causes large pollutant loads and poor water quality. The fresh water inflow of wastewater from the RMA can account for three times the volume of the river discharge during the low discharge period. This article assesses the hydrodynamics and potential transport of particulate and dissolved scalars in this estuary. A field experiment was conducted to record the water level, current velocity, salinity, temperature and suspended particulate matter (SPM) contents during a full semi-diurnal tidal cycle. This experiment was performed during low river discharge and spring tide conditions. The estuary showed a partially mixed circulation pattern. The residual transport of water and salt were up estuary, while the SPM residual transport was down estuary. The former were understood as the effect of the residual circulation around the islands, while the latter was interpreted as a morphological factor inducing greater resuspension during the ebb, despite the symmetrical ebb and flood currents. This mechanism may transport SPM to the inner shelf, even under tide-dominated conditions when the opposite would be expected.

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