Advances in Estuarine Physics

MacCready, Parker; Geyer, W. Rockwell

doi:10.1146/annurev-marine-120308-081015

Cited by 334 publications

(227 citation statements)

References 61 publications

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“…According to the classic theory for an idealized estuary [25], the magnitude of the two-layer exchange flow (u E ) is related to the water depth (H), the longitudinal salinity gradient (s x ), and the effective eddy viscosity (K M ) as:…”

Section: Non-tidal Circulationmentioning

confidence: 99%

“…Since the effective eddy viscosity can be viewed as a modification on the traditional eddy viscosity by incorporating the contributions from tidal averaging [25], both the mixing patterns and the tidal currents need to be examined. The overall mixing patterns are barely changed because the dredged area is relatively small and the artificially maintained channel bed is fairly smooth before and after the project (Figure 13).…”

Section: Non-tidal Circulationmentioning

confidence: 99%

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Cross-Scale Baroclinic Simulation of the Effect of Channel Dredging in an Estuarine Setting

Zhang

Wang

et al. 2018

Water

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Holistic simulation approaches are often required to assess human impacts on a river-estuary-coastal system, due to the intrinsically linked processes of contrasting spatial scales. In this paper, a Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM) is applied in quantifying the impact of a proposed hydraulic engineering project on the estuarine hydrodynamics. The project involves channel dredging and land expansion that traverse several spatial scales on an ocean-estuary-river-tributary axis. SCHISM is suitable for this undertaking due to its flexible horizontal and vertical grid design and, more importantly, its efficient high-order implicit schemes applied in both the momentum and transport calculations. These techniques and their advantages are briefly described along with the model setup. The model features a mixed horizontal grid with quadrangles following the shipping channels and triangles resolving complex geometries elsewhere. The grid resolution ranges from~6.3 km in the coastal ocean to 15 m in the project area. Even with this kind of extreme scale contrast, the baroclinic model still runs stably and accurately at a time step of 2 min, courtesy of the implicit schemes. We highlight that the implicit transport solver alone reduces the total computational cost by 82%, as compared to its explicit counterpart. The base model is shown to be well calibrated, then it is applied in simulating the proposed project scenario. The project-induced modifications on salinity intrusion, gravitational circulation, and transient events are quantified and analyzed.

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Section: Non-tidal Circulationmentioning

confidence: 99%

Section: Non-tidal Circulationmentioning

confidence: 99%

Cross-Scale Baroclinic Simulation of the Effect of Channel Dredging in an Estuarine Setting

Zhang

Wang

et al. 2018

Water

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“…In the estuarine literature, 0 is typically called the river salt flux, 1 the exchange flux, and 2 the tidal flux (e.g., MacCready and Geyer, 2010). We generalize these terms to 'mean barotropic' ( 0 , 0 ), 'mean exchange' ( 1 , 1 ) and 'fluctuating' ( 2 , 2 ) fluxes, since the freshwater inputs are not from a river, and tides are not necessarily the dominant mode of variability.…”

Section: Time-averaging Budgets and Decomposing Transportsmentioning

confidence: 99%

“…Dispersion from an oscillatory flow field has been studied extensively for tides in typical estuaries (e.g. Fischer, 1976;Geyer and Signell, 1992;MacCready and Geyer, 2010). Tidal dispersion can result in significant down-gradient salt fluxes in some estuaries but only limited fluxes in others.…”

Section: Net Exchange and Fjord Renewalmentioning

confidence: 99%

Dynamics of Greenland�s glacial fjords

Jackson¹

2016

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Glacial fjords form conduits between glaciers of the Greenland Ice Sheet and the North Atlantic. They are the gateways for importing oceanic heat to melt ice and for exporting meltwater into the ocean. Submarine melting in fjords has been implicated as a driver of recent glacier acceleration; however, there are no direct measurements of this melting, and little is known about the fjord processes that modulate melt rates. Combining observations, theory, and modeling, this thesis investigates the circulation, heat transport, and meltwater export in glacial fjords.While most recent studies focus on glacial buoyancy forcing, there are other drivers -e.g. tides, local wind, shelf variability -that can be important for fjord circulation. Using moored records from two major Greenlandic fjords, shelf forcing (from shelf density fluctuations) is found to dominate the fjord circulation, driving rapid exchange with the shelf and large heat content variability near the glacier. Contrary to the conventional paradigm, these flows mask any glacier-driven circulation in the non-summer months. During the summer, when shelf forcing is reduced and freshwater forcing peaks, a mean exchange flow transports warm Atlantic-origin water towards the glacier and exports glacial meltwater.Many recent studies have inferred submarine melt rates from oceanic heat transport, but the fjord budgets that underlie this method have been overlooked. Building on estuarine studies of salt fluxes, this thesis presents a new framework for assessing glacial fjord budgets and revised equations for inferring meltwater fluxes. Two different seasonal regimes are found in the heat/salt budgets for Sermilik Fjord, and the results provide the first time-series of submarine meltwater and subglacial discharge fluxes into a glacial fjord.Finally, building on the observations, ROMS numerical simulations and two analytical models are used to investigate the dynamics of shelf-driven flows and their importance relative to local wind forcing across the parameter space of Greenland's fjords. The fjord response is found to vary primarily with the width relative to the deformation radius and the fjord adjustment timescale relative to the forcing timescale. Understanding these modes of circulation is a step towards accurate modeling of ocean-glacier interactions.

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“…The time-variation in the vertical stratification and remixing is important as it modifies the residual circulation that would occur under the barotropic conditions alone . The resulting residual circulation is a consequence of nonlinear tidal advection, lateral gradients in both density and sea surface elevation, frictional forces, the Coriolis effect and mixing processes (Fischer, 1976;MacCready and Geyer, 2010).…”

Section: Introductionmentioning

confidence: 99%

Impact of operational model nesting approaches and inherent errors for coastal simulations

et al. 2016

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A region of freshwater influence (ROFI) under hypertidal conditions is used to demonstrate inherent problems for nested operational modelling systems. Such problems can impact the accurate simulation of freshwater export within shelf seas, so must be considered in coastal ocean modelling studies. In Liverpool Bay (our UK study site), freshwater inflow from 3 large estuaries forms a coastal front that moves in response to tides and winds. The cyclic occurrence of stratification and remixing is important for the biogeochemical cycles, as nutrient and pollutant loaded freshwater is introduced into the coastal system. Validation methods, using coastal observations from fixed moorings and cruise transects, are used to assess the simulation of the ROFI, through improved spatial structure and temporal variability of the front, as guidance for best practise model setup. A structured modelling system using a 180 m grid nested within a 1.8 km grid demonstrates how compensation for error at the coarser resolution can have an adverse impact on the nested, high resolution application. Using 2008, a year of typical calm and stormy periods with variable river influence, the sensitivities of the ROFI dynamics to initial and boundary conditions are investigated. It is shown that accurate representation of the initial water column structure is important at the regional scale and that the boundary conditions are most important at the coastal scale. Although increased grid resolution captures the frontal structure, the accuracy in frontal position is determined by the offshore boundary conditions and therefore the accuracy of the coarser regional model.

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Advances in Estuarine Physics

Cited by 334 publications

References 61 publications

Cross-Scale Baroclinic Simulation of the Effect of Channel Dredging in an Estuarine Setting

Cross-Scale Baroclinic Simulation of the Effect of Channel Dredging in an Estuarine Setting

Dynamics of Greenland�s glacial fjords

Impact of operational model nesting approaches and inherent errors for coastal simulations

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