Greg Ivey

Cyanobacterial and microcystins dynamics following the application of hydrogen peroxide to waste stabilisation ponds

Publisher: Copernicus GmbH

Date: 05-06-2013

DOI: 10.5194/HESS-17-2097-2013

Abstract: Abstract. Cyanobacteria and cyanotoxins are a risk to human and ecological health, and a hindrance to biological wastewater treatment. This study investigated the use of hydrogen peroxide (H2O2) for the removal of cyanobacteria and cyanotoxins from within waste stabilization ponds (WSPs). The daily dynamics of cyanobacteria and microcystins (commonly occurring cyanotoxins) were examined following the addition of H2O2 to wastewater within both the laboratory and at the full scale within a maturation WSP, the final pond in a wastewater treatment plant. Hydrogen peroxide treatment at concentrations ≥ 0.1 mg H2O2 μg−1 total phytoplankton chlorophyll a led to the lysis of cyanobacteria, in turn releasing intracellular microcystins to the dissolved state. In the full-scale trial, dissolved microcystins were then degraded to negligible concentrations by H2O2 and environmental processes within five days. A shift in the phytoplankton assemblage towards beneficial Chlorophyta species was also observed within days of H2O2 addition. However, within weeks, the Chlorophyta population was significantly reduced by the re-establishment of toxic cyanobacterial species. This re-establishment was likely due to the inflow of cyanobacteria from ponds earlier in the treatment train, suggesting that whilst H2O2 may be a suitable short-term management technique, it must be coupled with control over inflows if it is to improve WSP performance in the longer term.

Axisymmetric withdrawal and inflow in a density-stratified container

Publisher: Cambridge University Press (CUP)

Date: 12-1985

DOI: 10.1017/S0022112085002841

Steady convective exchange flows down slopes

Publisher: Springer Science and Business Media LLC

Date: 1999

DOI: 10.1007/S000270050065

Atmospheric forcing intensifies the effects of regional ocean warming on reef-scale temperature anomalies during a coral bleaching event

Publisher: American Geophysical Union (AGU)

Date: 09-2013

DOI: 10.1002/JGRC.20338

Wave-current interactions in the continental shelf bottom boundary layer of the Australian North West Shelf during tropical cyclone conditions

Publisher: Elsevier BV

Date: 08-2018

DOI: 10.1016/J.CSR.2018.07.006

Internal tide dynamics in a topographically complex region: Browse Basin, Australian North West Shelf

Publisher: American Geophysical Union (AGU)

Date: 26-01-2011

DOI: 10.1029/2009JC005881

Nutrient fluxes into an isolated coral reef atoll by tidally driven internal bores

Publisher: Wiley

Date: 26-10-2018

DOI: 10.1002/LNO.11051

A dissolved oxygen budget model for Lake Erie in summer

Publisher: Wiley

Date: 12-1985

DOI: 10.1111/J.1365-2427.1985.TB00242.X

Particle capture and low-Reynolds-number flow around a circular cylinder

Publisher: Cambridge University Press (CUP)

Date: 07-09-2012

DOI: 10.1017/JFM.2012.367

Abstract: Particle capture, whereby suspended particles contact and adhere to a solid surface (a ‘collector’), is an important mechanism in a range of environmental processes. In aquatic systems, typically characterized by low collector Reynolds numbers ( $\\mathit{Re}$ ), the rate of particle capture determines the efficiencies of a range of processes such as seagrass pollination, suspension feeding by corals and larval settlement. In this paper, we use direct numerical simulation (DNS) of a two-dimensional laminar flow to accurately quantify the rate of capture of low-inertia particles by a cylindrical collector for $\\mathit{Re}\\leq 47$ (i.e. a range where there is no vortex shedding). We investigate the dependence of both the capture rate and maximum capture angle on both the collector Reynolds number and the ratio of particle size to collector size. The inner asymptotic expansion of Skinner ( Q. J. Mech. Appl. Maths , vol. 28, 1975, pp. 333–340) for flow around a cylinder is extended and shown to provide an excellent framework for the prediction of particle capture and flow close to the leading face of a cylinder up to $\\mathit{Re}= 10$ . Our results fill a gap between theory and experiment by providing, for the first time, predictive capability for particle capture by aquatic collectors in a wide (and relevant) Reynolds number and particle size range.

Observations of Enhanced Sediment Transport by Nonlinear Internal Waves

Publisher: American Geophysical Union (AGU)

Date: 06-10-2020

DOI: 10.1029/2020GL088499

Turbulent mixing efficiency at an energetic ocean site

Publisher: American Geophysical Union (AGU)

Date: 09-2013

DOI: 10.1002/JGRC.20292

Convectively driven exchange in a shallow coastal embayment

Publisher: Elsevier BV

Date: 09-1999

DOI: 10.1016/S0278-4343(99)00034-5

Density Stratification, Turbulence, but How Much Mixing?

Publisher: Annual Reviews

Date: 2008

DOI: 10.1146/ANNUREV.FLUID.39.050905.110314

Abstract: We examine observations of turbulence in the geophysical environment, primarily from oceans but also from lakes, in light of theory and experimental studies undertaken in the laboratory and with numerical simulation. Our focus is on turbulence in density-stratified environments and on the irreversible fluxes of tracers that actively contribute to the density field. Our understanding to date has come from focusing on physical problems characterized by high Reynolds number flows with no spatial or temporal variability, and we examine the applicability of these results to the natural or geophysical-scale problems. We conclude that our s ling and interpretation of the results remain a first-order issue, and despite decades of ship-based observations we do not begin to approach a reliable s ling of the overall turbulent structure of the ocean interior.

Shoaling internal solitary waves

Publisher: American Geophysical Union (AGU)

Date: 09-2013

DOI: 10.1002/JGRC.20291

Simple mixing criteria for the growth of negatively buoyant phytoplankton

Publisher: Wiley

Date: 05-2003

DOI: 10.4319/LO.2003.48.3.1326

Ocean Transport Pathways to a World Heritage Fringing Coral Reef: Ningaloo Reef, Western Australia

Publisher: Public Library of Science (PLoS)

Date: 20-01-2016

DOI: 10.1371/JOURNAL.PONE.0145822

Helium accumulation in groundwater. II: A model for the accumulation of the crustal 4He degassing flux

Publisher: Elsevier BV

Date: 11-1985

DOI: 10.1016/0016-7037(85)90244-3

The tidal regime of Shark Bay, Western Australia

Publisher: Elsevier BV

Date: 08-2003

DOI: 10.1016/S0272-7714(02)00343-8

A numerical model of wave- and current-driven nutrient uptake by coral reef communities

Publisher: Elsevier BV

Date: 04-2011

DOI: 10.1016/J.ECOLMODEL.2011.01.014

Convection in a long box driven by heating and cooling on the horizontal boundaries

Publisher: Cambridge University Press (CUP)

Date: 10-03-1996

DOI: 10.1017/S0022112096001735

Abstract: Convection driven by spatially variable heat transfer across the water surface is an important transport mechanism in many geophysical applications. This flow is modelled in a rectangular tank with an aspect ratio, H/L , of 0.1 (where H and L are the tank height and length, respectively). Heat fluxes are applied through horizontal copper plates of length 0.1 L located at the top of one end of the tank and at the bottom of the other end. Experimental flows have been forced with heating at the bottom of the tank and cooling at the top, which gives rise to unstable convection in the end regions. Using water and a glycerol/water mix as the experimental fluids, flow visualization studies and measurements of temperature, velocity and heat flux have been made. Flow visualization studies revealed that complex unsteady turbulent flows occupied the end regions, while cubic velocity profiles characterized the horizontal laminar flow in the interior of the tank. Simple scaling arguments were developed for steady-state velocity and temperature fields, which are in good agreement with the experimental data. In the current experiments the portion of the plates closest to the tank interior (and to the tank endwall in the case of the glycerol/water experiments) were occupied by laminar boundary layers, while the remainder of the plates were occupied by turbulent flow. An effective Rayleigh number Ra * was defined, based upon the portion of the plate occupied by turbulent flow, as was a corresponding modified Nusselt number Nu *. The heat transfer was well predicted by classical Rayleigh-Bénard scaling with the Nusselt number Nu * ∼ Ra *1/3 . The range of Ra * was 4.3 × 10 5 ≤ Ra * ≤ 1.7 × 10 8 . Scaling arguments predicted the triple occupancy of the plates by differing boundary layer regimes within the range of 10 5 ≤ Ra * ≤ 10 14 .

Oxidative stress causes a decline in lysosomal integrity during hypothermic incubation of rat hepatocytes

Publisher: American Geophysical Union (AGU)

Date: 10-2008

DOI: 10.1029/2007WR005959

Calibrated Suspended Sediment Observations Beneath Large Amplitude Non‐Linear Internal Waves

Publisher: American Geophysical Union (AGU)

Date: 12-2021

DOI: 10.1029/2021JC017538

Abstract: While it has been recognized for some time that large litude non‐linear internal waves (NLIW) can mobilize and transport sediment, quantitative observations of this process are rare. Rarer still are accompanying estimates of suspended sediment mass concentration (SSC) during the passage of NLIW. Here, we present high resolution observations of NLIW and the SSC response within the bottom boundary layer. The observations were made in 250 m of water in a mildly sloping region of the Browse Basin on Australia’s Northwest Shelf. We compare two independent but direct calibration methods, and employ Bayesian methods to estimate the uncertainty in SSC. During a large NLIW event, the peak mean SSC estimate at 0.49 m above the sea bed was 161 mg L −1 , with a maximum time‐rate‐of‐change of 0.14 mg L −1 s −1 . The unsteady boundary layer forcing under NLIW resulted in a variable time‐height dependent relationship between bed stress and SSC with increasing height above the sea bed. Suspended sediment was restricted to the bottom mixing layer, with sharp vertical gradients of up to 40 mg L −1 m −1 observed at the edge of the layer. The observations presented here are intended to offer guidance to numerical sediment modelers about likely SSC under strong NLIW.

On predicting particle capture rates in aquatic ecosystems

Publisher: Public Library of Science (PLoS)

Date: 22-12-2021

DOI: 10.1371/JOURNAL.PONE.0261400

Abstract: Recent advances in understanding the capture of moving suspended particles in aquatic ecosystems have opened up new possibilities for predicting rates of suspension feeding, larval settlement, seagrass pollination and sediment removal. Drawing on results from both highly-resolved computational fluid dynamics (CFD) simulations and existing experimental data, we quantify the controlling influence of flow velocity, particle size and collector size on rates of contact between suspended particles and biological collectors over the parameter space characterising a erse range of aquatic ecosystems. As distinct from assumptions in previous modeling studies, the functional relationships describing capture are highly variable. Contact rates can vary in opposing directions in response to changes in collector size, an organism’s size, the size of particles being intercepted (related to diet in the case of suspension feeders), and the flow strength. Contact rates shift from decreasing to increasing with collector diameter when particles become relatively large and there is vortex shedding in the collector wake. And in some ranges of the ecologically relevant parameter space, contact rates do not increase strongly with velocity or particle size. The understanding of these complex dependencies allows us to reformulate some hypotheses of selection pressure on the physiology and ecology of aquatic organisms. We discuss the benefits and limitations of CFD tools in predicting rates of particle capture in aquatic ecosystems. Finally, across the complete parameter space relevant to real aquatic ecosystems, all quantitative estimates of particle capture from our model are provided here.

A weakly nonlinear model of long internal waves in closed basins

Publisher: Cambridge University Press (CUP)

Date: 24-09-2002

DOI: 10.1017/S0022112002001362

Abstract: A simple model is developed, based on an approximation of the Boussinesq equation, that considers the weakly nonlinear evolution of an initial interface disturbance in a closed basin. The solution consists of the sum of the solutions of two independent Korteweg–de Vries (KdV) equations (one along each characteristic) and a second-order wave–wave interaction term. It is demonstrated that the solutions of the two independent KdV equations over the basin length [0, L ] can be obtained by the integration of a single KdV equation over the extended reflected domain [0, 2 L ]. The main effect of the second-order correction is to introduce a phase shift to the sum of the KdV solutions where they overlap. The results of model simulations are shown to compare qualitatively well with laboratory experiments. It is shown that, provided the d ing timescale is slower than the steepening timescale, any initial displacement of the interface in a closed basin will generate three types of internal waves: a packet of solitary waves, a dispersive long wave and a train of dispersive oscillatory waves.

Roles of Shear and Convection in Driving Mixing in the Ocean

Publisher: American Geophysical Union (AGU)

Date: 09-02-2021

DOI: 10.1029/2020GL089455

Abstract: Using field, numerical, and laboratory studies, we consider the roles of both shear and convection in driving mixing in the interior of the density‐stratified ocean. Shear mixing dominates when the Richardson number Ri 0.25, convective mixing dominates when Ri 1.0, and in the intermediate regime when 0.25 Ri 1.0 both shear and convection can contribute to mixing. For pure shear mixing the mixing efficiency Ri f approaches 0.5, while for pure convective mixing the mixing efficiency Ri f approaches 0.75. The diapycnal diffusivities for the two mechanisms are given by very different expressions. Despite these complexities, a simple mixing length model using the mean flow shear S provides robust estimates of diffusivity across the range 0 Ri 2. To account for the roles of both shear and convection over this range of Ri , we also formulate a modified version of the empirical KPP model for parameterizing ocean mixing in numerical models.

Unsteady, Turbulent Convection into a Rotating, Linearly Stratified Fluid: Modeling Deep Ocean Convection

Publisher: American Meteorological Society

Date: 12-1995

DOI: 10.1175/1520-0485(1995)025<3032:UTCIAR>2.0.CO;2

Experiments on transient natural convection in a cavity

Publisher: Cambridge University Press (CUP)

Date: 07-1984

DOI: 10.1017/S0022112084001658

Abstract: A laboratory experiment is used to study the transient flow in an initially isothermal cavity at temperature T 0 following the rapid change of the two vertical endwalls to temperatures T 0 ± Δ T respectively. In idual temperature records are taken and the transient flow in the entire cavity is visualized with the aid of a tracer technique. It is shown that an oscillatory approach to final steady-state conditions exists for certain flow regimes, although the form of the oscillatory response is different to that suggested by previous work. It is argued that this oscillatory behaviour is due to the inertia of the flow entering the interior of the cavity from the sidewall boundary layers, which may lead to a form of internal hydraulic jump if the Rayleigh number is sufficiently large.

Modeling bed shear-stress fluctuations in a shallow tidal channel

Publisher: American Geophysical Union (AGU)

Date: 05-2014

DOI: 10.1002/2013JC009718

In-situ estimation of erosion model parameters using an advection-diffusion model and Bayesian inversion

Publisher: Wiley

Date: 16-11-2022

DOI: 10.1002/ESSOAR.10512841.1

The combined influence of hydrodynamic forcing and calcification on the spatial distribution of alkalinity in a coral reef system

Publisher: American Geophysical Union (AGU)

Date: 04-2012

DOI: 10.1029/2011JC007603

Directional decomposition of internal tides propagating from multiple generation sites

Publisher: Elsevier BV

Date: 06-2021

DOI: 10.1016/J.OCEMOD.2021.101801

Environmental Factors and the Application of Hydrogen Peroxide for the Removal of Toxic Cyanobacteria from Waste Stabilization Ponds

Publisher: American Society of Civil Engineers (ASCE)

Date: 10-2011

DOI: 10.1061/(ASCE)EE.1943-7870.0000401

The Effects of Remote Internal Tides on Continental Slope Internal Tide Generation

Publisher: American Meteorological Society

Date: 06-2019

DOI: 10.1175/JPO-D-18-0180.1

Abstract: Internal tide generation at sloping topography is nominally determined by the local slope geometry, density stratification, and tidal forcing. Recent global ocean models have revealed that remotely generated internal tides (RITs) can also influence locally generated internal tides (LITs). Field measurements with through-the-water column moorings on the southern portion of the Australian North West Shelf (NWS) suggested that RITs led to local regions with either positive or negative barotropic to baroclinic energy conversion. Three-dimensional numerical simulations were used to examine the role of RITs on local internal tide climatology on the inner slope and shelf portion of the NWS. The model demonstrated the principle remote generation site was the western portion of the offshore Exmouth Plateau. Extending the model domain to include this offshore plateau region increased the local net energy conversion on the inner shelf by 13.5% and on the slope by 8%. Simulations using an idealized 2D model configuration aligned along the principal direction of RIT propagation demonstrated that the sign and magnitude of the local energy conversion was dependent on the distance between the remote and local generation sites, the phase difference between the local barotropic tide and the RIT, and the litude of both the local barotropic tide and the RIT. For RITs with a low-wave Froude number (Fr 0.05), where Fr is the ratio of the internal wave baroclinic velocity to the linear wave speed, the conversion rates were consistent with kinematic predictions based on the phase difference only. For stronger flows with Fr 0.05, the conversion rates showed a nonlinear dependence on Fr.

Numerical simulation of the summer wake of Rottnest Island, Western Australia

Publisher: Elsevier BV

Date: 08-2007

DOI: 10.1016/J.DYNATMOCE.2007.01.001

Parameterization of turbulent fluxes and scales using homogeneous sheared stably stratified turbulence simulations

Publisher: Cambridge University Press (CUP)

Date: 25-02-2005

DOI: 10.1017/S0022112004002587

The variation of flow and turbulence across the sediment–water interface

Publisher: Cambridge University Press (CUP)

Date: 06-07-2017

DOI: 10.1017/JFM.2017.345

Abstract: A basic framework characterising the interaction between aquatic flows and permeable sediment beds is presented here. Through the permeability Reynolds number ( $Re_{K}=\\sqrt{K}u_{\\ast }/\\unicode[STIX]{x1D708}$ , where $K$ is the sediment permeability, $u_{\\ast }$ is the shear velocity and $\\unicode[STIX]{x1D708}$ is the fluid viscosity), the framework unifies two classical flow typologies, namely impermeable boundary layer flows ( $Re_{K}\\ll 1$ ) and highly permeable canopy flows ( $Re_{K}\\gg 1$ ). Within this range, the sediment–water interface (SWI) is identified as a transitional region, with $Re_{K}$ in aquatic systems typically $O(0.001{-}10)$ . As the sediments obstruct conventional measurement techniques, experimental observations of interfacial hydrodynamics remain extremely rare. The use of refractive index matching here allows measurement of the mean and turbulent flow across the SWI and thus direct validation of the proposed framework. This study demonstrates a strong relationship between the structure of the mean and turbulent flow at the SWI and $Re_{K}$ . Hydrodynamic characteristics, such as the interfacial turbulent shear stress, velocity, turbulence intensities and turbulence anisotropy tend towards those observed in flows over impermeable boundaries as $Re_{K}\\rightarrow 0$ and towards those seen in flows over highly permeable boundaries as $Re_{K}\\rightarrow \\infty$ . A value of $Re_{K}\\approx 1{-}2$ is seen to be an important threshold, above which the turbulent stress starts to dominate the fluid shear stress at the SWI, the penetration depths of turbulence and the mean flow into the sediment bed are comparable and similarity relationships developed for highly permeable boundaries hold. These results are used to provide a new perspective on the development of interfacial transport models at the SWI.

Examining shifts in zooplankton community variability following biological invasion

Publisher: Wiley

Date: 2013

DOI: 10.4319/LO.2013.58.1.0399

Boundary mixing in a rotating, stratified fluid

Publisher: Cambridge University Press (CUP)

Date: 10-1987

DOI: 10.1017/S0022112087002507

Abstract: An earlier laboratory experiment of Ivey & Corcos (1982) on boundary mixing in a stratified fluid was extended by including the effects of rotation. An axisymmetric version of the original laboratory experiments was constructed and a series of experiments conducted on a rotating table with the tank filled with salt-stratified solution. The combination of vertical mixing at the boundary and horizontal mixing by mesoscale eddies lead to the weakening of the interior density gradient. While the mechanisms were thus complex, the experiments demonstrated that the boundary-mixing process may be parameterized by a relatively simple formulation dependent upon the turbulence properties at the boundary and the tank dimensions.

The temporal evolution of baroclinic basin-scale waves in a rotating circular basin

Publisher: Cambridge University Press (CUP)

Date: 25-01-2005

DOI: 10.1017/S0022112004002344

Density-ratio effects on the capture of suspended particles in aquatic systems

Publisher: Cambridge University Press (CUP)

Date: 15-10-2015

DOI: 10.1017/JFM.2015.557

Abstract: Particle capture, whereby suspended particles contact and adhere to a solid surface (a ‘collector’), is important in a range of environmental processes, including suspension feeding by corals and ‘filtering’ by aquatic vegetation. Although aquatic particles are often considered as perfect tracers when estimating capture efficiency, the particle density ratio ( ${\\it\\rho}^{+}$ ) – the ratio of the particle density to the fluid density – can significantly affect capture. In this paper, we use a numerical analysis of particle trajectories to quantify the influence of ${\\it\\rho}^{+}$ on particle capture by circular collectors in a parameter space relevant to aquatic systems. As it is generally believed that inertia augments the capture efficiency when the Stokes number ( $\\mathit{St}$ ) of the particles exceeds a critical value, we first estimate the critical Stokes number for aquatic-type particles and demonstrate its dependence on both ${\\it\\rho}^{+}$ and the Reynolds number ( $\\mathit{Re}$ ). Second, we analyse how efficiently circular collectors can capture neutrally buoyant ( ${\\it\\rho}^{+}=1$ ), sediment-type ( ${\\it\\rho}^{+}=2.6$ ) and weakly buoyant ( ${\\it\\rho}^{+}=0.9$ ) aquatic particles. Our analysis shows that, for ${\\it\\rho}^{+} $ , inertia can either augment or diminish capture efficiency, and inertial effects appear well before the critical Stokes number is reached. The role of particle inertia is maximised at Stokes numbers above the critical value and, for sediment-type particles, can result in as much as a fourfold increase in the rate of capture relative to perfect tracers of the same size. Similar but opposite effects are observed for weakly buoyant particles, where capture efficiency can decrease by 60 % relative to the capture of perfect tracers.

Quantifying Diapycnal Mixing in an Energetic Ocean

Publisher: American Geophysical Union (AGU)

Date: 2018

DOI: 10.1002/2017JC013242

Reconstruction of Wall Shear-Stress Fluctuations in a Shallow Tidal River

Publisher: Springer International Publishing

Date: 18-08-2015

DOI: 10.1007/978-3-319-20388-1_22

The effects of tropical cyclone characteristics on the surface wave fields in Australia's North West region

Publisher: Elsevier BV

Date: 05-2017

DOI: 10.1016/J.CSR.2017.03.006

Magma-mixing and the dynamics of withdrawal from stratified reservoirs

Publisher: Elsevier BV

Date: 1986

DOI: 10.1016/0377-0273(86)90084-3

Estimation of a characteristic friction velocity in stirred benthic chambers

Publisher: Inter-Research Science Center

Date: 2004

DOI: 10.3354/MEPS279291

Hydraulics and mixing in controlled exchange flows

Publisher: American Geophysical Union (AGU)

Date: 15-01-2001

DOI: 10.1029/2000JC000266

Local winds and encroaching currents drive summertime subsurface blooms over a narrow shelf

Publisher: Wiley

Date: 24-02-2022

DOI: 10.1002/LNO.12043

Abstract: The ability to forecast the biological productivity of the coastal ocean relies on the quantification of the physical processes that deliver nutrients to the euphotic zone. Here we explore these pathways using observations of the coupled biological and physical variability of waters offshore of the east coast of Tasmania in the summertime. The observations include an array of moored autonomous profilers deployed over an 18‐d period—providing continuous, full‐depth measurements of turbulent microstructure, temperature, velocity, and chlorophyll a (Chl a ) fluorescence, complemented by shipboard nutrient measurements. Local upwelling was driven by the encroaching East Australian Current (EAC) extension onto the shelf and to a lesser extent the local winds. The interaction of the local winds and the encroaching boundary current was reflected in the shelf nutrient budget and led to a rapid increase in subsurface Chl a . Diffusive vertical fluxes had minimal impact on subsurface Chl a in the mid‐shelf and outer‐shelf. Upwelling‐favorable winds were too weak to drive significant vertical mixing, and mixing associated with the current‐driven Ekman transport was too deep compared to the euphotic zone depth. The observed subsurface Chl a did not reflect the satellite estimates of productivity. Since the EAC extension transports warm, low‐nutrient surface waters from the subtropics, satellite chlorophyll measurements decreased during the same period the depth‐averaged Chl a increased. This seeming paradox illustrated how long duration, full water column s ling can elucidate the coupled biological and physical processes that aid our ongoing effort to forecast the biological state of the coastal ocean.

Estimation of the rate of dissipation of turbulent kinetic energy and turbulent lengthscales in grid-generated turbulence

Publisher: Springer Science and Business Media LLC

Date: 05-2003

DOI: 10.1007/S00348-003-0597-X

Dynamics of a tidally‐forced stratified shear flow on the continental slope

Publisher: American Geophysical Union (AGU)

Date: 11-2011

DOI: 10.1029/2011JC007214

Abstract: The near seabed mean and turbulent processes on the continental slope were measured for a three week period using an array of acoustic‐Doppler velocimeters and thermistors over the bottom 30 m at the 400 m isobath. Baroclinic motions with characteristics similar to internal bores or boluses propagated onshore during the flood phase of both spring and neap tides. The arrival time of these internal bores at our measurement site varied amongst tidal cycles and their characteristics were not highly correlated with the litude of the barotropic tidal forcing. The passage of the internal bores was associated with large turbulent overturns, enhanced turbulent kinetic energy dissipation (ε 10 −6 W kg −1 ) and intensified currents ( times the barotropic forcing) within meters of the seabed. During the deployment, stratification and shear competed to govern our observed overturning length scale (≲4 m) that were characterized by the Ellison length scale L E . Only measurements closest to the seabed (1.7 m) were described by the log law‐of‐the‐wall generally both buoyancy and the presence of the bottom boundary influenced L E , while sometimes flow‐induced shear determined L E . As the distance of our measurements from the seabed increased, the influence of buoyancy became more pronounced. These results highlight that a more general descriptor of the overturning length scale is necessary for complex stratified shear flows.

The effects of a surface stress-driven ambient circulation on open ocean convection

Publisher: Informa UK Limited

Date: 12-1999

DOI: 10.1080/03091929908203704

Submaximal exchange between a convectively forced basin and a large reservoir

Publisher: Cambridge University Press (CUP)

Date: 10-01-1999

DOI: 10.1017/S0022112098003437

Abstract: If a sill-enclosed basin, connected to a large reservoir, is suddenly subjected to a de-stabilizing surface buoyancy flux, it will first mix vertically by turbulent convection before the resulting lateral buoyancy gradient generates a horizontal exchange flow across the sill. We present a study which examines the unsteady adjustment of such a basin under continued steady forcing. It is shown, through theoretical development and laboratory experimentation, that two consecutive unsteady regimes characterized by different dynamic balances are traversed as the flow approaches a steady state. Once established the exchange flow is controlled at the sill crest where it is hydraulically critical. In the absence of a lateral contraction, the single control at the sill crest allows a range of submaximal exchange states with the flow at the sill being dependent not only on the forcing and geometrical parameters but also on mixing conditions within the basin which are, in turn, dependent on the sill exchange. The sill–basin system is therefore strongly coupled although it remains isolated from the external reservoir conditions by a region of internally supercritical flow. Results from the laboratory experiments are used to demonstrate the link between the forcing and the exchange flow at the sill. Steady-state measurements of the interior mean velocity and buoyancy fields are also compared with previous analytical models.

Experiments on mixing due to internal solitary waves breaking on uniform slopes

Publisher: American Geophysical Union (AGU)

Date: 15-06-1999

DOI: 10.1029/1999JC900037

Cylinder wakes in shallow oscillatory flow: the coastal island wake problem

Publisher: Cambridge University Press (CUP)

Date: 04-07-2019

DOI: 10.1017/JFM.2019.441

Abstract: Topographic complexity on continental shelves is the catalyst that transforms the barotropic tide into the secondary and residual circulations that dominate vertical and cross-shelf mixing processes. Island wakes are one such ex le that are observed to significantly influence the transport and distribution of biological and physical scalars. Despite the importance of island wakes, to date, no sufficient, mechanistic description of the physical processes governing their development exists for the general case of unsteady tidal forcing. Controlled laboratory experiments are necessary for the understanding of this complex flow phenomenon. Here, three-dimensional velocity field measurements of cylinder wakes in shallow-water oscillatory flow are conducted across a parameter space that is typical of tidal flow around shallow islands. The wake form in steady flows is typically described in terms of the stability parameter $S=c_{f}D/h$ (where $D$ is the island diameter, $h$ is the water depth and $c_{f}$ is the bottom boundary friction coefficient) in tidal flows, there is an additional dependence on the Keulegan–Carpenter number $KC=U_{0}T/D$ (where $U_{0}$ is the tidal velocity litude and $T$ is the tidal period). In this study we demonstrate that when the influence of bottom friction is confined to a Stokes boundary layer the stability parameter is given by $S=\\unicode[STIX]{x1D6FF}^{+}/KC$ where $\\unicode[STIX]{x1D6FF}^{+}$ is the ratio of the wavelength of the Stokes bottom boundary layer to the depth. Three classes of wake form are observed with decreasing wake stability: (i) steady bubble for $S\\gtrsim 0.1$ (ii) unsteady bubble for $0.06\\lesssim S\\lesssim 0.1$ and (iii) vortex shedding for $S\\lesssim 0.06$ . Transitions in wake form and wake stability are shown to depend on the magnitude and temporal evolution of the wake return flow. Scaling laws are developed to allow upscaling of the laboratory results to island wakes. Vertical and lateral transport depend on three parameters: (i) the flow aspect ratio $h/D$ (ii) the litude of tidal motion relative to the island size, given by $KC$ and (iii) the relative influence of bottom friction to the flow depth, given by $\\unicode[STIX]{x1D6FF}^{+}$ . A model of wake upwelling based on Ekman pumping from the bottom boundary layer demonstrates that upwelling in the near-wake region of an island scales with $U_{0}(h/D)KC^{1/6}$ and is independent of the wake form. Finally, we demonstrate an intrinsic link between the dynamical eddy scales, predicted by the Ekman pumping model, and the island wake form and stability.

A non-stationary harmonic model for seasonal internal tide amplitude prediction

Publisher: Wiley

Date: 20-11-2020

DOI: 10.1002/ESSOAR.10504834.1

In Situ Estimation of Erosion Model Parameters Using an Advection‐Diffusion Model and Bayesian Inversion

Publisher: American Geophysical Union (AGU)

Date: 06-2023

DOI: 10.1029/2022MS003500

Abstract: We describe a framework for the simultaneous estimation of model parameters in a partial differential equation using sparse observations. Markov Chain Monte Carlo s ling is used in a Bayesian framework to estimate posterior probability distributions for each parameter. We describe the necessary components of this approach and its broad potential for application in models of unsteady processes. The framework is applied to three case studies, of increasing complexity, from the field of cohesive sediment transport. We demonstrate that the framework can be used to recover posterior distributions for all parameters of interest and the results agree well with independent estimates (where available). We also demonstrate how the framework can be used to compare different model parameterizations and provide information on the covariance between model parameters.

Localized mixing due to a breaking internal wave ray at a sloping bottom

Publisher: Cambridge University Press (CUP)

Date: 10-11-1997

DOI: 10.1017/S0022112097006939

Abstract: A laboratory experiment was conducted to investigate the characteristics of turbulence generated by an internal wave ray breaking on a sloping bed. The width of the incident wave ray was small compared to the bed length, so that an isolated turbulent patch was generated by the breaking process, a configuration unique to the present study. The parameter range covered subcritical, critical and supercritical frequencies. Flow visualization and velocity measurements revealed that near critical conditions the flow was confined to a narrow region above the bed and, contrary to expectations, critical waves showed a weak turbulence field. Subcritical and supercritical reflection resembled wave–wave interaction between the incident and the reflected waves and showed comparable centred displacement lengthscales. As the incident waves became progressively supercritical instabilities were first initiated away from the bed. For supercritical waves the centred displacement lengthscale and the turbulent Reynolds number both increased steadily up to about γ≈2, after which they started to decrease (γ=ω/ω c , where ω is the frequency of the incident wave and ω c = N sinβ is the critical frequency for an ambient uniform stratification of magnitude N and a bed angle of β). For subcritical waves an increase in the centred displacement lengthscale and the turbulent Reynolds number was also observed. The mixed fluid generated at the boundary collapsed into the fluid interior in the form of a horizontal two-dimensional viscous–buoyancy intrusion: the efficiency of mixing was, however, very small and no measurable change in the mean density gradient was observed over the duration of the experiments.

Turbulent mixing in a sloping benthic boundary layer energized by internal waves

Publisher: Cambridge University Press (CUP)

Date: 10-09-2000

DOI: 10.1017/S0022112000008788

Abstract: A laboratory study was carried out to directly measure the turbulence properties in a benthic boundary layer (BBL) above a uniformly sloping bottom where the BBL is energized by internal waves. The ambient fluid was continuously stratified and the steadily forced incoming wave field consisted of a confined beam, restricting the turbulent activity to a finite region along the bottom slope. Measurements of dissipation showed some variation over the wave phase, but cycle-averaged values indicated that the dissipation was nearly constant with height within the BBL. Dissipation levels were up to three orders of magnitude larger than background laminar values and the thickness of the BBL could be defined in terms of the observed dissipation variation with height. Assuming that most of the incoming wave energy was dissipated within the BBL, predicted levels of dissipation were in good agreement with the observations. Measurements were also made of density and two orthogonal components of the velocity fluctuations at discrete heights above the bottom. Cospectral estimates of density and velocity fluctuations showed that the major contributions to both the vertical density flux and the momentum flux resulted from frequencies near the wave forcing frequency, rather than super-buoyancy frequencies, suggesting a strong nonlinear interaction between the incident and reflected waves close to the bottom. Within the turbulent BBL, time-averaged density fluxes were significant and negative near the wave frequencies but negligible at frequencies greater than the buoyancy frequency N . While dissipation rates were high compared to background laminar values, they were low compared to the value of ε tr ≈ 15 vN 2 , the transition value often used to assess the capacity of a stratified flow to produce mixing. Existing models relating mixing to dissipation rate rely on the existence of a positive-definite density flux at frequencies greater than N as a signature of fluid mixing and therefore cannot apply to these experiments. We therefore introduce a simple model, based on the concept of diascalar fluxes, to interpret the mixing in the stratified fluid in the BBL and suggest that this may have wider application than to the particular configuration studied here.

Hydrodynamic modelling of snapper Pagrus auratus egg and larval dispersal in Shark Bay, Western Australia: reproductive isolation at a fine spatial scale

Publisher: Inter-Research Science Center

Date: 2003

DOI: 10.3354/MEPS265213

Baroclinic geostrophic adjustment in a rotating circular basin

Publisher: Cambridge University Press (CUP)

Date: 25-09-2004

DOI: 10.1017/S0022112004000230

Determining Near‐Bottom Fluxes of Passive Tracers in Aquatic Environments

Publisher: American Geophysical Union (AGU)

Date: 23-03-2018

DOI: 10.1002/2017GL076789

Processes controlling the position of frontal systems in Shark Bay, Western Australia

Publisher: Elsevier BV

Date: 11-2005

DOI: 10.1016/J.ECSS.2005.06.017

The dynamics of internal wave resonance in periodically forced narrow basins

Publisher: American Geophysical Union (AGU)

Date: 11-2012

DOI: 10.1029/2012JC008134

Estimating turbulent kinetic energy dissipation using the inertial subrange method in environmental flows

Publisher: Wiley

Date: 07-2011

DOI: 10.4319/LOM.2011.9.302

Vertical mixing due to the breaking of critical internal waves on sloping boundaries

Publisher: Cambridge University Press (CUP)

Date: 07-1989

DOI: 10.1017/S0022112089001849

Acquiring Long-Term Turbulence Measurements from Moored Platforms Impacted by Motion

Publisher: American Meteorological Society

Date: 11-2016

DOI: 10.1175/JTECH-D-16-0041.1

Abstract: For measurements from either profiling or moored instruments, several processing techniques exist to estimate the dissipation rate of turbulent kinetic energy ϵ , a core quantity used to determine oceanic mixing rates. Moored velocimeters can provide long-term measurements of ϵ , but they can be plagued by motion-induced contamination. To remove this contamination, two methodologies are presented that use independent measurements of the instrument’s acceleration and rotation in space. The first is derived from the relationship between the spectra (cospectra) and the variance (covariance) of a time series. The cospectral technique recovers the environmental (or true) velocity spectrum by summing the measured spectrum, the motion-induced spectrum, and the cospectrum between the motion-induced and measured velocities. The second technique recovers the environmental spectrum by correcting the measured spectrum with the squared coherency, essentially assuming that the measured signal shares variance with either the environmental signal or the motion signal. Both techniques are applied to moored velocimeters at 7.5 and 20.5 m above the seabed in 105 m of water. By estimating the orbital velocities from their respective spectra and comparing them against those obtained from nearby wave measurements, the study shows that the surface wave signature is recovered with the cospectral technique, while it is underpredicted with the squared coherency technique. The latter technique is particularly problematic when the instrument’s motion is in phase with the orbital (environmental) velocities, as it removes variance that should have been added to the measured spectrum. The estimated ϵ from the cospectral technique compares well with estimates from nearby microstructure velocity shear vertical profiles.

Estimating net transport and mixing using a time‐dependent inverse method

Publisher: American Geophysical Union (AGU)

Date: 07-2008

DOI: 10.1029/2006JC003705

Impact of windage on ocean surface Lagrangian coherent structures

Publisher: Springer Science and Business Media LLC

Date: 16-12-2016

DOI: 10.1007/S10652-016-9499-3

Nearshore circulation in a tropical fringing reef system

Publisher: American Geophysical Union (AGU)

Date: 12-02-2011

DOI: 10.1029/2010JC006439

Convectively driven coastal currents in a rotating basin

Publisher: Journal of Marine Research/Yale

Date: 08-1988

DOI: 10.1357/002224088785113478

Unsteady convective exchange flows in cavities

Publisher: Cambridge University Press (CUP)

Date: 10-08-1998

DOI: 10.1017/S002211209800175X

Abstract: Horizontal exchange flows driven by spatial variation of buoyancy fluxes through the water surface are found in a variety of geophysical situations. In all ex les of such flows the timescale characterizing the variability of the buoyancy fluxes is important and it can vary greatly in magnitude. In this laboratory study we focus on the effects of this unsteadiness of the buoyancy forcing and its influence on the resulting flushing and circulation processes in a cavity. The experiments described all start with destabilizing forcing of the flows, but the buoyancy fluxes are switched to stabilizing forcing at three different times spanning the major timescales characterizing the resulting cavity-scale flows. For destabilizing forcing, these timescales are the flushing time of the region of forcing, and the filling-box timescale, the time for the cavity-scale flow to reach steady state. When the forcing is stabilizing, the major timescale is the time for the fluid in the exchange flow to pass once through the forcing boundary layer. This too is a measure of the time to reach steady state, but it is generally distinct from the filling-box time. When a switch is made from destabilizing to stabilizing buoyancy flux, inertia is important and affects the approach to steady state of the subsequent flow. Velocities of the discharges from the end regions, whether forced in destabilizing or stabilizing ways, scaled as u ∼( Bl ) 1/3 (where B is the forcing buoyancy flux and l is the length of the forcing region) in accordance with Phillips' (1966) results. Discharges with destabilizing and stabilizing forcing were, respectively, Q − ∼( Bl ) 1/3 H and Q + ∼( Bl ) 1/3 δ (where H is the depth below or above the forcing plate and δ is the boundary layer thickness). Thus Q − / Q + O (1) provided H O (δ), as was certainly the case in the experiments reported, demonstrating the overall importance of the flushing processes occurring during periods of cooling or destabilizing forcing.

Biophysical characteristics of a morphologically-complex macrotidal tropical coastal system during a dry season

Publisher: Elsevier BV

Date: 08-2014

DOI: 10.1016/J.ECSS.2014.07.018

Quantifying Lake Water Quality Evolution: Coupled Geochemistry, Hydrodynamics, and Aquatic Ecology in an Acidic Pit Lake

Publisher: American Chemical Society (ACS)

Date: 16-08-2017

DOI: 10.1021/ACS.EST.7B01432

Abstract: Assessment of water quality evolution in the thousands of existing and future mine pit lakes worldwide requires new numerical tools that integrate geochemical, hydrological, and biological processes. A coupled model was used to test alternative hypothesized controls on water quality in a pit lake over ∼8 years. The evolution of pH, Al, and Fe were closely linked field observations were reproduced with generic solubility equilibrium controls on Fe(III) and Al and a commonly reported acceleration of the abiotic Fe(II) oxidation rate by 2-3 orders of magnitude. Simulations indicated an ongoing acidity loading at the site, and the depletion of Al mineral buffering capacity after ∼5 years. Simulations also supported the existence of pH limitation on nitrification, and a limitation on phytoplankton growth other than the commonly postulated P and DIC limitations. Furthermore, the model reproduced the general patterns of salinity, pH, Al, and Fe during an uncontrolled river breach in 2011, however, incorporating sediment biogeochemical feedbacks is required to reproduce the observed postbreach internal alkalinity generation in the lake. The modeling approach is applicable to the study of hydrological, geochemical, and biological interactions for a range of lake and reservoir management challenges.

High-frequency internal waves in large stratified lakes

Publisher: Wiley

Date: 03-2003

DOI: 10.4319/LO.2003.48.2.0895

Resolving high-frequency internal waves generated at an isolated coral atoll using an unstructured grid ocean model

Publisher: Elsevier BV

Date: 02-2018

DOI: 10.1016/J.OCEMOD.2017.12.007

Uncovering Fine-Scale Wave-Driven Transport Features in a Fringing Coral Reef System via Lagrangian Coherent Structures

Publisher: MDPI AG

Date: 24-10-2020

DOI: 10.3390/FLUIDS5040190

Abstract: Understanding the transport and exchange of water masses both within a reef and between a reef and the surrounding ocean is needed to describe a wide-range of ecosystem processes that are shaped by the movement of material and heat. We show how novel Lagrangian data processing methods, specifically developed to reveal key and often hidden transport structures, can help visualize flow transport patterns within and around morphologically complex reef systems. As an ex le case study, we consider the wave-driven flow transport within the Ningaloo Reef in Western Australia. We show that a network of attracting, repelling, and trapping flow transport structures organizes the flow transport into, around, and out of the reef. This approach is broadly applicable to coral reef systems, since the combination of well-defined bathymetry and persistent flow-forcing mechanisms (e.g., by wave breaking or tides) is conducive to the existence of persistent Lagrangian transport structures that organize material transport.

The potential role of turbulence in modulating the migration of demersal zooplankton

Publisher: Wiley

Date: 20-11-2020

DOI: 10.1002/LNO.11646

Abstract: Despite suggestions that turbulence can affect the migration of zooplankton, field observations of such effects are scarce. This is especially the case for bottom‐associated (demersal) zooplankton that reside in the typically turbulent near‐bottom environment. Using moored sensors deployed at two coastal sites in the North Pacific and the Red Sea, we present observations of the effects of turbulence on the nocturnal emergence of demersal zooplankton. A cabled observatory consisting of a plankton camera, an acoustic current profiler and environmental sensors, was deployed near bottom in 20 m of water near Oshima Island, Japan. Observations were also obtained from a second site near a coral reef in 16 m of water in the Red Sea. Acoustic backscatter data obtained from current profilers at both sites provided a proxy for zooplankton density. Combined with simultaneous estimates of turbulence intensity, the observations suggest that the nocturnal emergence of demersal zooplankton was hindered by elevated levels of turbulence. While our findings are inferred from acoustic data, agreement between the two different sites supports our hypothesis that demersal zooplankton may remain near the bed during times of strong turbulence.

The temporal evolution of a geostrophic flow in a rotating stratified basin

Publisher: Elsevier BV

Date: 05-2005

DOI: 10.1016/J.DYNATMOCE.2004.12.002

Particle capture by a circular cylinder in the vortex-shedding regime

Publisher: Cambridge University Press (CUP)

Date: 19-09-2013

DOI: 10.1017/JFM.2013.407

Abstract: Particle capture, whereby suspended particles contact and adhere to a solid surface (a ‘collector’), is an important mechanism for a range of environmental processes including suspension feeding by corals and ‘filtering’ by aquatic vegetation. In this paper, we use two- and three-dimensional direct numerical simulations to quantify the capture efficiency ( $\\eta $ ) of low-inertia particles by a circular cylindrical collector at intermediate Reynolds numbers in the vortex-shedding regime (i.e. for $47\\lt \\mathit{Re}\\leq 1000$ , where $\\mathit{Re}$ is the collector Reynolds number). We demonstrate that vortex shedding induces oscillations near the leading face of the collector which greatly affect the quantity and distribution of captured particles. Unlike in steady, low- $\\mathit{Re}$ flow, particles directly upstream of the collector are not the most likely to be captured. Our results demonstrate the dependence of the time-averaged capture efficiency on $\\mathit{Re}$ and particle size, improving the predictive capability for the capture of particles by aquatic collectors. The transition to theoretical high-Reynolds-number behaviour (i.e. $\\eta \\sim {\\mathit{Re}}^{1/ 2} $ ) is complex due to comparatively rapid changes in wake conditions in this Reynolds number range.

Dynamics of the summer shelf circulation and transient upwelling off Ningaloo Reef, Western Australia

Publisher: American Geophysical Union (AGU)

Date: 03-2013

DOI: 10.1002/JGRC.20098

Effect of Long Internal Waves on the Quality of Water Withdrawn from a Stratified Reservoir

Publisher: American Society of Civil Engineers (ASCE)

Date: 11-2006

DOI: 10.1061/(ASCE)0733-9429(2006)132:11(1134)

Observations of Diurnal Coastal-Trapped Waves with a Thermocline-Intensified Velocity Field

Publisher: American Meteorological Society

Date: 07-2019

DOI: 10.1175/JPO-D-18-0194.1

Abstract: Using 18 days of field observations, we investigate the diurnal (D1) frequency wave dynamics on the Tasmanian eastern continental shelf. At this latitude, the D1 frequency is subinertial and separable from the highly energetic near-inertial motion. We use a linear coastal-trapped wave (CTW) solution with the observed background current, stratification, and shelf bathymetry to determine the modal structure of the first three resonant CTWs. We associate the observed D1 velocity with a superimposed mode-zero and mode-one CTW, with mode one dominating mode zero. Both the observed and mode-one D1 velocity was intensified near the thermocline, with stronger velocities occurring when the thermocline stratification was stronger and/or the thermocline was deeper (up to the shelfbreak depth). The CTW modal structure and litude varied with the background stratification and alongshore current, with no spring–neap relationship evident for the observed 18 days. Within the surface and bottom Ekman layers on the shelf, the observed velocity phase changed in the cross-shelf and/or vertical directions, inconsistent with an alongshore propagating CTW. In the near-surface and near-bottom regions, the linear CTW solution also did not match the observed velocity, particularly within the bottom Ekman layer. Boundary layer processes were likely causing this observed inconsistency with linear CTW theory. As linear CTW solutions have an idealized representation of boundary dynamics, they should be cautiously applied on the shelf.

A Model for Mass Transport Across the Sediment‐Water Interface

Publisher: American Geophysical Union (AGU)

Date: 04-2018

DOI: 10.1002/2017WR022418

Experiments on the generation of internal waves over continental shelf topography

Publisher: Cambridge University Press (CUP)

Date: 08-09-2010

DOI: 10.1017/S002211201000354X

Abstract: Experiments were performed to examine the generation of internal waves by a barotropic tide forcing a continuously stratified fluid over idealized continental shelf/slope topography. A range of responses was observed, including the generation of both internal wave beams and boundary layer boluses, primarily dependent on the values of both the Reynolds number and the topographic steepness parameter. The formation of beams required a critical bottom slope, whilst for bolus formation a large vertical fluid excursion was necessary. A bolus formed when the non-dimensional vertical excursion parameter Δ hN / W 0 3.2. Here Δ h is the vertical excursion, N is the buoyancy frequency and W 0 is the near-bottom vertical velocity associated with the local depth-averaged velocity. We simplified the classification of the observed flow regimes using a generation parameter G , defined as the ratio of a Reynolds number to the topographic steepness parameter. The estimated flow regime boundaries were: for G 3 only a beam was observed, for 3 G 50 there was a transitional regime with both a beam and a bolus observed, for 50 G 400 there was another transitional regime with no beam but a bolus observed, and finally for the regime with G 400 there was no bolus observed. We estimated that approximately 4% of the barotropic energy was converted to baroclinic energy when beams were generated.

Convectively driven exchange flow in a stratified sill-enclosed basin

Publisher: Cambridge University Press (CUP)

Date: 10-09-2000

DOI: 10.1017/S0022112000001130

Abstract: Laboratory experiments are used to investigate the processes governing steady convectively driven circulation in a basin that communicates with a large external reservoir over a shallow sill. The motion is maintained by a steady loss of buoyancy distributed over the surface of the basin. Turbulent convection associated with the forcing produces a horizontal buoyancy gradient across the sill and the resulting mean flow consists of a layer directed into the basin near the surface with a dense counter flow below. To first order, the magnitude of the exchange flow over the sill is determined by the horizontal momentum balance within the basin. Measurements of the mean and turbulent flow fields are used to show that inertia, buoyancy and friction may each contribute significantly to the balance. The interior flow produces a horizontal pressure gradient near the surface which must also contribute to the momentum balance. The density of the lower layer at the sill reflects the cumulative effect of interior processes, such as mixing, and these in turn influence the hydraulically controlled exchange flow over the sill. The basin dynamics are therefore coupled in a nonlinear fashion with the submaximal sill exchange. This coupling is investigated first by showing how interior processes are affected by changes in the magnitude of the forcing, and then by observing the associated variation of the flow state at the sill. The flow state is defined in terms of its relative proximity to the theoretical maximal exchange limit. Results show that the exchange flows are submaximal with flow rate approximately 85% of the maximal limit. This state appears to change very little in response to increasing forcing. For a stratified basin, which exhibits a deep stagnant layer under the convectively driven near-surface exchange flow, the possibility of basin ventilation or erosion of deep fluid exists in the long term. This process and its dependence on external parameters is also explored.

Investigating transport in a tidally driven coral atoll flow using Lagrangian coherent structures

Publisher: Wiley

Date: 05-10-2021

DOI: 10.1002/LNO.11939

Abstract: A field experiment study of flow transport around a coral reef was conducted at Scott Reef, an offshore atoll in the Timor Sea. A drifter deployment was designed based on the insight derived from two Lagrangian data analysis approaches, the finite‐time Lyapunov exponent method and the optimized‐parameter spectral clustering method, which were used to analyze the predictions of a numerical model. This analysis predicted the formation of a key transport barrier during a critical time of the tidal cycle that separated two bodies of water, one remaining trapped within the lagoon, and one advected offshore this transport structure had no clear signature upon inspection of the velocity fields and thus the use of Lagrangian methods was crucial. The observed drifter trajectories confirmed the predictions, with the drifters separating into two clusters, one on each side of the transport barrier. The results demonstrate how Lagrangian approaches elucidate the processes governing connectivity and water exchanges between atolls and the surrounding ocean.

Rossby number regimes for isolated convection in a homogeneous, rotating fluid

Publisher: Elsevier BV

Date: 12-1999

DOI: 10.1016/S0377-0265(99)00024-X

A laboratory investigation into shear-generated mixing in a salt wedge estuary

Publisher: Informa UK Limited

Date: 05-1997

DOI: 10.1080/03091929708208985

Ocean mixing in a shelf sea driven by energetic internal waves

Publisher: Authorea, Inc.

Date: 09-02-2023

DOI: 10.22541/ESSOAR.167591065.55629421/V1

Abstract: We collected observations of ocean mixing from three moorings placed at the 330m, 200m, and 150m isobaths on a pelagic ridge on the Australian North West Shelf (NWS). The region is subject to energetic surface and internal tides, non-linear internal waves, flow-topography interactions, and episodic intense wind events (i.e., tropical cyclones) that collectively drive energetic diapycnal mixing. We identified five dominant internal wave categories: both low (time scales from double the buoyancy period to 4 hours) and high-frequency (time scales between buoyancy period and double the buoyancy period) mode-1 waves, mode-2 waves, internal bores, and internal hydraulic jumps. A small number of turbulent mixing events dominated the total vertical heat flux at each mooring, with 15% of estimates accounting for as much as 90% of the total observed heat flux. These turbulent mixing events often occurred during the passage of internal wave events, with the internal wave events accounting for as much as 60% of the total heat flux in some locations. High-frequency mode-1 waves were the most significant contributors to the total vertical heat flux (∼ 20%). Internal bores made significant but localized contributions to mixing, accounting for up to ∼ 50% of the total vertical heat flux in some regions but with a negligible influence elsewhere. The contributions of the different internal wave categories to the total flux became more heterogeneous at shallower sites, indicating an increasingly complicated relationship between the forcing internal wave field and the mixing.

Coexistence of order and chaos in C major

Publisher: American Physical Society (APS)

Date: 17-10-2018

DOI: 10.1103/PHYSREVFLUIDS.3.100510

On the Nature of Turbulence in a Stratified Fluid. Part I: The Energetics of Mixing

Publisher: American Meteorological Society

Date: 05-1991

DOI: 10.1175/1520-0485(1991)021<0650:OTNOTI>2.0.CO;2

Three-dimensionality of shallow island wakes

Publisher: Springer Science and Business Media LLC

Date: 04-02-2019

DOI: 10.1007/S10652-019-09661-5

A seasonal harmonic model for internal tide amplitude prediction

Publisher: Wiley

Date: 26-05-2021

DOI: 10.1002/ESSOAR.10507151.1

Determining Mixing Rates from Concurrent Temperature and Velocity Measurements

Publisher: American Meteorological Society

Date: 10-2017

DOI: 10.1175/JTECH-D-16-0250.1

Abstract: Ocean mixing has historically been estimated using Osborn’s model by measuring the rate of dissipation of turbulent kinetic energy ϵ and the background density stratification N while assuming a value of the flux Richardson number . A constant is typically assumed, despite mounting field, laboratory, and modeling evidence that varies. This challenge can be overcome by estimating the turbulent diffusivity of heat using the Osborn–Cox model. This model, however, requires measuring the rate of dissipation of thermal variance χ , which has historically been challenging, particularly in energetic flows because the high wavenumbers of the temperature gradient spectra are unresolved with current technology. To overcome this difficulty, a method is described that determines χ by spectral fitting to the inertial-convective (IC) subrange of the temperature gradient spectra. While this concept has been exploited for moored time series, particularly near the bottom boundary, it has yet to be adapted to vertical microstructure profilers such as gliders, and autonomous and ship-based vertical profilers from which there are the most measurements. By using the IC subrange, χ , and hence , can be estimated even in very energetic events—precisely the conditions requiring more field observations. During less energetic periods, the temperature gradient spectra can also be integrated to obtain χ . By combining these two techniques, microstrucure profiles at a field site known for its very energetic internal waves are analyzed. This study demonstrates that the spectral fitting approach resolves intense mixing events with . By equating the Osborn and Osborn–Cox models, indirect estimates for can also be obtained.

Observations of Large-Amplitude Mode-2 Nonlinear Internal Waves on the Australian North West Shelf

Publisher: American Meteorological Society

Date: 2019

DOI: 10.1175/JPO-D-18-0097.1

Abstract: Large- litude mode-2 nonlinear internal waves were observed in 250-m-deep water on the Australian North West shelf. Wave litudes were derived from temperature measurements using three through-the-water-column moorings spaced 600 m apart in a triangular configuration. The moorings were deployed for 2 months during the transition period between the tropical monsoon and the dry season. The site had a 25–30-m- litude mode-1 internal tide that essentially followed the spring–neap tidal cycle. Regular mode-2 nonlinear wave trains with litudes exceeding 25 m, with the largest event exceeding 50 m, were also observed at the site. Overturning was observed during several mode-2 events, and the relatively high wave Froude number and steepness (0.15) suggested kinematic (convective) instability was likely to be the driving mechanism. The presence of the mode-2 waves was not correlated with the tidal forcing but rather occurred when the nonlinear steepening length scale was smaller than the distance from the generation region to the observation site. This steepening length scale is inversely proportional to the nonlinear parameter in the Korteweg–de Vries equation, and it varied by at least one order of magnitude under the evolving background thermal stratification over the observation period. Despite the complexity of the internal waves in the region, the nonlinear steepening length was shown to be a reliable indicator for the formation of large- litude mode-2 waves and the rarer occurrence of mode-1 large- litude waves. A local mode-2 generation mechanism caused by a beam interacting with a pycnocline is demonstrated using a fully nonlinear numerical solution.

Disaggregation of Microcystis aeruginosa colonies under turbulent mixing: Laboratory experiments in a grid-stirred tank

Publisher: Springer Science and Business Media LLC

Date: 05-2004

DOI: 10.1023/B:HYDR.0000026501.02125.CF

A Seasonal Harmonic Model for Internal Tide Amplitude Prediction

Publisher: American Geophysical Union (AGU)

Date: 10-2021

DOI: 10.1029/2021JC017570

Abstract: We present an empirical model of the seasonal variability of the internal tide using seasonal harmonics to modulate the litude of the fundamental tidal constituents. Internal tide data, from both long‐term, in‐situ moorings and a mesoscale‐resolving and internal tide‐resolving ocean model, are used to demonstrate the performance of the seasonal harmonic model for the Indo‐Australian Basin region. The seasonal model describes up to 15% more of the observed (baroclinic) sea surface height variance than a fixed‐ litude harmonic model at the mooring sites. The ocean model results demonstrate that the study region, which includes the Australian North West Shelf (NWS), Timor Sea, and southern Indonesian Islands, is dominated by standing wave interference patterns due to the presence of multiple generation sites. The seasonal harmonic model reveals that temporal shifts in the standing wave patterns coincide with seasonal variations in density stratification. This shift is particularly evident within distances of 2–3 internal wave lengths from strong generation sites. The fraction of the variance of the internal tide signal explained by seasonal modulations is largest in standing wave node regions, contributing to differences in predictive skill of the seasonal harmonic model at two moorings separated by only 38 km. Output of the harmonic model also demonstrates that the seasonally evolving internal tide propagating southward from Lombok Strait had a small litude in October when shear from the Indonesian Throughflow was strongest.

Temporal variability of the standing internal tide in the Browse Basin, Western Australia

Publisher: American Geophysical Union (AGU)

Date: 06-2012

DOI: 10.1029/2011JC007523

Response Characteristics of a Buoyancy-Driven Sea

Publisher: American Meteorological Society

Date: 09-2001

DOI: 10.1175/1520-0485(2001)031<2721:RCOABD>2.0.CO;2

On convective turbulence and the influence of rotation

Publisher: Elsevier BV

Date: 05-1997

DOI: 10.1016/S0377-0265(96)00479-4

Near-Surface Wind-Induced Mixing in a Mine Lake

Publisher: American Society of Civil Engineers (ASCE)

Date: 10-2008

DOI: 10.1061/(ASCE)0733-9429(2008)134:10(1464)

Video: The Coexistence of Order and Chaos in C-major

Publisher: American Physical Society

Date: 19-11-2017

DOI: 10.1103/APS.DFD.2017.GFM.V0053

Numerical modelling of the mean flow characteristics of the Leeuwin Current system

Publisher: Elsevier BV

Date: 04-2007

DOI: 10.1016/J.DSR2.2007.02.003

Contrasting Heat Budget Dynamics During Two La Niña Marine Heat Wave Events Along Northwestern Australia

Publisher: American Geophysical Union (AGU)

Date: 02-2018

DOI: 10.1002/2017JC013426

Generation and Propagation of Near-Inertial Waves in a Baroclinic Current on the Tasmanian Shelf

Publisher: American Meteorological Society

Date: 10-2019

DOI: 10.1175/JPO-D-18-0208.1

Abstract: Near-inertial waves (NIWs) are often an energetic component of the internal wave field on windy continental shelves. The effect of baroclinic geostrophic currents, which introduce both relative vorticity and baroclinicity, on NIWs is not well understood. Relative vorticity affects the resonant frequency f eff , while both relative vorticity and baroclinicity modify the minimum wave frequency of freely propagating waves ω min . On a windy and narrow shelf, we observed wind-forced oscillations that generated NIWs where f eff was less than the Coriolis frequency f . If everywhere f eff f then NIWs were generated where ω min f and f eff was smallest. The background current not only affected the location of generation, but also the NIWs’ propagation direction. The estimated NIW energy fluxes show that NIWs propagated predominantly toward the equator because ω min f on the continental slope for the entire s le period. In addition to being laterally trapped on the shelf, we observed vertically trapped and intensified NIWs that had a frequency ω within the anomalously low-frequency band (i.e., ω min ω f eff ), which only exists if the baroclinicity is nonzero. We observed two periods when ω min f on the shelf, but the relative vorticity was positive (i.e., f eff f ) for one of these periods. The process of NIW propagation remained consistent with the local ω min , and not f eff , emphasizing the importance of baroclinicity on the NIW dynamics. We conclude that windy shelves with baroclinic background currents are likely to have energetic NIWs, but the current and seabed will adjust the spatial distribution and energetics of these NIWs.

Seasonal circulation and temperature variability near the North West Cape of Australia

Publisher: American Geophysical Union (AGU)

Date: 04-2012

DOI: 10.1029/2011JC007653

Confronting Grand Challenges in environmental fluid mechanics

Publisher: American Physical Society (APS)

Date: 08-02-2021

DOI: 10.1103/PHYSREVFLUIDS.6.020501

Stratification and mixing in sea straits

Publisher: Elsevier BV

Date: 02-2004

DOI: 10.1016/J.DSR2.2003.07.020

Flow separation and resuspension beneath shoaling nonlinear internal waves

Publisher: American Geophysical Union (AGU)

Date: 02-2009

DOI: 10.1029/2007JC004411

Uncertainty Quantification of Density and Stratification Estimates with Implications for Predicting Ocean Dynamics

Publisher: American Meteorological Society

Date: 07-2019

DOI: 10.1175/JTECH-D-18-0200.1

Abstract: We present a statistical method for reconstructing continuous background density profiles that embeds incomplete measurements and a physically intuitive density stratification model within a Bayesian hierarchal framework. A double hyperbolic tangent function is used as a parametric density stratification model that captures various pycnocline structures in the upper ocean and offers insight into several density profile characteristics (e.g., pycnocline depth). The posterior distribution is used to quantify uncertainty and is estimated using recent advances in Markov chain Monte Carlo s ling. Temporally evolving posterior distributions of density profile characteristics, isopycnal heights, and nonlinear ocean process models for internal gravity waves are presented as ex les of how uncertainty propagates through models dependent on the density stratification. The results show 0.95 posterior interval widths that ranged from 2.5% to 4% of the expected values for the linear internal wave phase speed and 15%–40% for the nonlinear internal wave steepening parameter. The data, collected over a year from a through-the-column mooring, and code, implemented in the software package Stan, accompany the article.

The Kelvin–Helmholtz to Holmboe instability transition in stratified exchange flows

Publisher: Cambridge University Press (CUP)

Date: 02-2003

DOI: 10.1017/S0022112002003397

Convectively driven mixed layer growth in a rotating, stratified fluid

Publisher: Elsevier BV

Date: 03-1995

DOI: 10.1016/0967-0637(94)00039-U

Dying to find the source – the use of rhodamine WT as a proxy for soluble point source pollutants in closed pipe surface drainage networks

Publisher: Copernicus GmbH

Date: 12-11-2009

DOI: 10.5194/HESS-13-2169-2009

Abstract: Abstract. Rhodamine WT (RWT), a xanthene dye, may serve as a proxy for soluble pollutants within quantitative tracing studies investigating point source contaminant transport. This study quantified the effects of altering the concentration, pH, temperature and salinity of a RWT solution on the detected fluorescence of RWT within the laboratory prior to a field release of RWT within a closed pipe urban drainage network. All RWT solutions exhibited stability and % variation from the expected concentration over a thirteen hour laboratory study period pH related quenching of RWT fluorescence of up to 14.9% was observed for solutions with pH .9 and increasing salinity of RWT solution was found to have a negligible quenching effect. In direct contrast to previous studies RWT fluorescence was found to directly correlate with temperature of solution, and a temperature correction factor was determined and tested. The field release study succeeded in detecting RWT at concentrations two orders of magnitude greater than background fluorescence. Based on longitudinal dispersion theory, observed RWT peak concentrations were within 10% of predicted peaks.

A numerical study of the dynamics of the wave-driven circulation within a fringing reef system

Publisher: Springer Science and Business Media LLC

Date: 22-01-2012

DOI: 10.1007/S10236-011-0514-4

Secondary circulation induced by flow curvature and Coriolis effects around headlands and islands

Publisher: Springer Science and Business Media LLC

Date: 02-2004

DOI: 10.1007/S10236-003-0058-3

On continental shelf convection: The influence of an ideal coast

Publisher: American Geophysical Union (AGU)

Date: 15-07-1998

DOI: 10.1029/98JC01110

The combined effect of transient wind‐driven upwelling and eddies on vertical nutrient fluxes and phytoplankton dynamics along Ningaloo Reef, Western Australia

Publisher: American Geophysical Union (AGU)

Date: 07-2016

DOI: 10.1002/2016JC011791

Experimental study on resonantly forced interfacial waves in a stratified circular cylindrical basin

Publisher: Cambridge University Press (CUP)

Date: 14-06-2007

DOI: 10.1017/S002211200700585X

Abstract: Laboratory experiments have been performed on resonantly forced interfacial waves in a circular cylindrical basin containing a two-layer stratified fluid. The results of this shallow-water study exhibit a number of similarities to previous shallow-water studies performed in single-layer fluids, such as the generation of a large- litude response over a frequency bandwidth offset from the primary resonance, generation of a swirling mode at the observed resonant condition, and the significant contribution of higher harmonics. The two-layer experiments also produce results that are unique to stratified domains. In particular, the observed negative nonlinearity of the resonant condition at shallow water depth, mixing of the density interface resulting in detuning the forced response from the resonant condition, the enhanced role of viscous dissipation, and an alternative pathway for the nonlinear generation of higher-frequency waves when the layer depths are disparate. The results of this study are considered with regard to their implications for enclosed basins at the geophysical scale that are subject to near resonant forcing.

On the Nature of Turbulence in a Stratified Fluid. Part II: Application to Lakes

Publisher: American Meteorological Society

Date: 05-1991

DOI: 10.1175/1520-0485(1991)021<0659:OTNOTI>2.0.CO;2

Near‐inertial ocean response to tropical cyclone forcing on the Australian North‐West Shelf

Publisher: American Geophysical Union (AGU)

Date: 12-2015

DOI: 10.1002/2015JC010868

The generation of internal waves by tidal flow over continental shelf/slope topography

Publisher: Springer Science and Business Media LLC

Date: 23-08-2008

DOI: 10.1007/S10652-008-9085-4

Observations of bottom intensification of temperature and velocity fluctuations induced by oblique tidal interactions with a slope

Publisher: CSIRO Publishing

Date: 2006

DOI: 10.1071/MF05054

Abstract: Long-term measurements of temperature and velocity collected at six depths in 302 m of water off the North West Cape of Western Australia (21°37′35″S, 113°56′11″E) revealed several periods of extreme near-bed currents. The dominant forcing at the site is the M2 tide, with energy levels generally decreasing as the bottom is approached. There is, however, a dramatic change in the energy distribution for all frequencies in excess of the M4 tidal frequency between 80 and 10 m above the seabed. Waves in this frequency bandwidth are critical to the local bottom slope and show a strong linear internal wave signature however, they do not appear to conform with linear internal wave reflection theory. Dissipation estimates reveal energetic motions with dissipation rates of ~10−5 m2 s−3. Superimposed on this ambient state, three energetic events with duration varying between 8 and 24 h can also be detected. These are characterised by large increases in energy levels in the high-frequency range, and peak speeds varying from 0.59 m s−1 to 1.87 m s−1. These events appear to be driven by direct local energy inputs at high frequencies.

Laboratory study of the interaction between two internal wave rays

Publisher: Cambridge University Press (CUP)

Date: 10-04-1997

DOI: 10.1017/S0022112096004508

Abstract: Laboratory experiments were conducted to study the interaction between two downward propagating internal wave rays with identical properties but opposite horizontal phase velocities. The intersection of the rays produced a velocity field with stagnation points, and these points propagated vertically upwards within the intersection region. Nonlinear non-resonant interactions between the two rays produced evanescent modes, with frequencies greater than the ambient buoyancy frequency, trapped within the intersection region. These evanescent modes provided a mechanism whereby energy could accumulate locally and, even though the vertical wavelength of the primary resultant wave remained the same, the local isopycnal displacements increased in time. Eventually, the isopycnals were forced to overturn in the region just above the stagnation points by the variation with depth in the local horizontal strain rate. The gravitationally unstable overturning ultimately broke down releasing its available potential energy and generating turbulence within the intersection region. The results showed that the release of available potential energy was disrupted by the wave motions and even the dissipative scales were directly affected by the ambient stratification and the background wave motion. The distribution of the centred displacement scales was highly skewed towards the Kolmogorov scale and the turbulent Reynolds number Re t was low. Thus, the net buoyancy flux was very small and almost all turbulent kinetic energy was dissipated over the parameter range investigated. The results also showed that for such dissipative events the square of the strain Froude number (ε/ν N 2 0 ) and the turbulent Reynolds number Re t can be less than one.

The degeneration of internal waves in lakes with sloping topography

Publisher: Wiley

Date: 09-2005

DOI: 10.4319/LO.2005.50.5.1620

Estimating Turbulent Dissipation from Microstructure Shear Measurements Using Maximum Likelihood Spectral Fitting over the Inertial and Viscous Subranges

Publisher: American Meteorological Society

Date: 04-2016

DOI: 10.1175/JTECH-D-15-0218.1

Abstract: A technique is presented to derive the dissipation of turbulent kinetic energy ϵ by using the maximum likelihood estimator (MLE) to fit a theoretical or known empirical model to turbulence shear spectral observations. The commonly used integration method relies on integrating the shear spectra in the viscous range, thus requiring the resolution of the highest wavenumbers of the turbulence shear spectrum. With current technology, the viscous range is not resolved at sufficiently large wavenumbers to estimate high ϵ however, long inertial subranges can be resolved, making spectral fitting over both this subrange and the resolved portion of the viscous range an attractive method for deriving ϵ . The MLE takes into account the chi-distributed properties of the spectral observations, and so it does not rely on the log-transformed spectral observations. This fitting technique can thus take advantage of both the inertial and viscous subranges, a portion of both, or simply one of the subranges. This flexibility allows a broad range of ϵ to be resolved. The estimated ϵ is insensitive to the range of wavenumbers fitted with the model, provided the noise-dominated portion of the spectra and the low wavenumbers impacted by the mean flow are avoided. For W kg −1 , the MLE fitting estimates agree with those obtained by integrating the spectral observations. However, with increasing ϵ the viscous subrange is not fully resolved and the integration method progressively starts to underestimate ϵ compared with the values obtained from fitting the spectral observations.

Mixing Driven by Breaking Nonlinear Internal Waves

Publisher: American Geophysical Union (AGU)

Date: 25-09-2020

DOI: 10.1029/2020GL089591

Development of a new risk-based framework to guide investment in water quality monitoring

Publisher: Springer Science and Business Media LLC

Date: 06-12-2013

DOI: 10.1007/S10661-013-3552-1

Abstract: An innovative framework for optimising investments in water quality monitoring has been developed for use by water and environmental agencies. By utilising historical data, investigating the accuracy of monitoring methods and considering the risk tolerance of the management agency, this new methodology calculates optimum water quality monitoring frequencies for in idual water bodies. Such information can be applied to water quality constituents of concern in both engineered and natural water bodies and will guide the investment of monitoring resources. Here we present both the development of the framework itself and a proof of concept by applying it to the occurrence of hazardous cyanobacterial blooms in freshwater lakes. This application to existing data demonstrates the robustness of the approach and the capacity of the framework to optimise the allocation of both monitoring and mitigation resources. When applied to cyanobacterial blooms in the Swan Coastal Plain of Western Australia, we determined that optimising the monitoring regime at in idual lakes could greatly alter the overall monitoring schedule for the region, rendering it more risk averse without increasing the amount of monitoring resources required. For water resources with high-density temporal data related to constituents of concern, a similar reduction in risk may be observed by applying the framework.

Observations of the shelf circulation dynamics along Ningaloo Reef, Western Australia during the austral spring and summer

Publisher: Elsevier BV

Date: 03-2015

DOI: 10.1016/J.CSR.2014.12.013

The energetics of large-scale internal wave degeneration in lakes

Publisher: Cambridge University Press (CUP)

Date: 25-05-2005

DOI: 10.1017/S0022112005003915

Internal-Tide Spectroscopy and Prediction in the Timor Sea

Publisher: American Meteorological Society

Date: 2015

DOI: 10.1175/JPO-D-14-0007.1

Abstract: Spectral analyses of two 3.5-yr mooring records from the Timor Sea quantified the coherence of mode-0 (surface) and mode-1 (internal) tides with the astronomical tidal potential. The noncoherent tides had well-defined variance and were most accurately quantified for tidal species (as opposed to constituents) in long records ( months). On the continental slope (465 m), the semidiurnal mode-0 and mode-1 velocity and mode-1 pressure variance were 95%, 68%, and 56% coherent, respectively. On the continental shelf (145 m), the semidiurnal mode-0 and mode-1 velocity and mode-1 pressure variance were 98%, 34%, and 42% coherent, respectively. The response method produced time series of the semidiurnal coherent and noncoherent tides. The spectra and decorrelation time scales of the semidiurnal tidal litudes were similar to those of the barotropic mean flow and mode-1 eigenspeed (~4 days), suggesting local mesoscale variability shapes noncoherent tidal variability. Over long time scales ( days), mode-1 sea surface displacement litudes were positively correlated with mode-1 eigenspeed on the shelf. At both moorings, internal tides were likely modulated during both generation and propagation. Self-prediction using the response method enabled about 75% of semidiurnal mode-1 sea surface displacement to be predicted 2.5 days in advance. Improved prediction models will require realistic tide–topography coupling and background variability with both short and long time scales.

A numerical study of the eddying characteristics of the Leeuwin Current System

Publisher: Elsevier BV

Date: 03-2008

DOI: 10.1016/J.DSR.2007.12.004

Operational Oceanography in the 21st Century

Publisher: Springer Netherlands

Date: 2011

DOI: 10.1007/978-94-007-0332-2

Mean and Turbulent Characteristics of a Bottom Mixing‐Layer Forced by a Strong Surface Tide and Large Amplitude Internal Waves

Publisher: American Geophysical Union (AGU)

Date: 2022

DOI: 10.1029/2020JC017055

Abstract: We present 15 days of both mean and turbulent field observations bottom mixing‐layer at a gently sloping 250 m deep continental shelf site, energized by tides and nonlinear internal waves (NLIWs). The tidal frequency forcing was due to the combined effects of the barotropic tide and a mode‐1 internal tide (IT), while the NLIWs were predominantly mode‐1 waves of depression. The bottom mixing‐layer thickness varied at both semidiurnal and sub‐tidal ∼O(10)d frequencies, with an average thickness of around 10 m. Compression and expansion of the mixing‐layer by both the IT and NLIWs affected the mean velocity profiles in the mixing‐layer, while the phasing between the barotropic and baroclinic flows led to an asymmetry in mean velocity profiles between periods of rising and falling isotherms. With the exception of periods of flow reversal, the turbulent kinetic energy balance and turbulent stress observations were consistent with the existence of an inertial‐sublayer with thickness of approximately 10%–15% of the mixing‐layer thickness ( ∼1 m), even beneath NLIWs. In the outer portion of the mixing‐layer—that is, above the inertial‐sublayer—NLIWs modulated the local turbulence spectra. We discuss the observations in the context of a predictive model for mixing‐layer thickness. The analysis suggests that the high‐frequency variability in mixing‐layer thickness was dominated by internal wave pumping, though strength of the ambient stratification and the frequency of the forcing were important controls on the time‐averaged (sub‐tidal) variation.

Internal wave evolution in a space–time varying field

Publisher: Cambridge University Press (CUP)

Date: 16-11-2000

DOI: 10.1017/S0022112000001841

Abstract: An extended Korteweg–de Vries (KdV) equation is derived that describes the evolution and propagation of long interfacial gravity waves in the presence of a strong, space–time varying background. Provision is made in the derivation for a spatially varying lower depth so that some topographic effects can also be included. The extended KdV model is applied to some simple scenarios in basins of constant and varying depths, using approximate expressions for the variable coefficients derived for the case when the background field is composed of a moderate- litude ultra-long wave. The model shows that energy can be transferred either to or from the evolving wave packet depending on the relative phases of the evolving waves and the background variation. Comparison of the model with laboratory experiments confirms its applicability and usefulness in examining the evolution of weakly nonlinear waves in natural systems where the background state is rarely uniform or steady.

The role of boundary mixing in the deep ocean

Publisher: American Geophysical Union (AGU)

Date: 15-10-1987

DOI: 10.1029/JC092IC11P11873

Boundary mixing in a stratified fluid

Publisher: Cambridge University Press (CUP)

Date: 08-1982

DOI: 10.1017/S0022112082001773

Evaporation induced convection enhances mixing in the upper ocean

Publisher: Frontiers Media SA

Date: 16-05-2023

DOI: 10.3389/FMARS.2023.1176226

Abstract: The upper ocean surface layer is directly affected by the air-sea fluxes. The diurnal variations in these fluxes also cause the upper ocean mixed layer turbulence and mixing to diurnally vary. The underlying thermohaline structure also varies accordingly throughout the day. Here we use large-eddy simulation to quantify the role of surface evaporation in modulating the diurnal mixed layer turbulence and mixing in the presence of wind forcing. During daytime, the upper ocean boundary layer becomes thermally stratified, and a salinity inversion layer is formed in the upper 10m, leading to double diffusive salt-fingering instability. During nighttime, the mixed layer undergoes convective deepening due to surface buoyancy loss redfrom both surface cooling and evaporation. We find that salinity makes a major contribution to the convective instability during both transitions between day and night. Overall surface evaporation increases the mixed layer depth and irreversible mixing through convection, both during nighttime and daytime, and leads to better prediction of the dynamical variables as sea surface salinity (SSS) and sea surface temperature (SST). Our findings can help improve the ocean parameterizations to improve the forecasts on a diurnal timescale.

The Hydrodynamic Response of the Sediment‐Water Interface to Coherent Turbulent Motions

Publisher: American Geophysical Union (AGU)

Date: 04-10-2018

DOI: 10.1029/2018GL079850

Abstract: Unique observations of the hydrodynamics across the sediment‐water interface are used to quantify the instantaneous response of the interstitial fluid to the passage of coherent turbulent motions in the overlying flow. Over a range of permeability Reynolds numbers (where K is the sediment permeability, u ∗ is the shear velocity, and ν is the fluid viscosity), the passage of these turbulent motions create velocity fluctuations and momentum fluxes at the sediment‐water interface to greatly exceed their mean values. Sweep motions are observed to penetrate into the sediment bed and induce instantaneous momentum fluxes that can be an order of magnitude larger than the mean bed shear stress. By penetrating into the sediment bed, the turbulent motions increase the effective roughness experienced by the flow and therefore the flow resistance. The properties of the mean flow alone are thus insufficient to describe the interaction of the overlying flow with the sediments.

Density and viscosity gradients in zoned magma chambers, and their influence withdrawal dynamics

Publisher: Elsevier BV

Date: 12-1986

DOI: 10.1016/0377-0273(86)90055-7

Tides and Internal Waves on the Continental Shelf

Publisher: Springer Netherlands

Date: 2011

DOI: 10.1007/978-94-007-0332-2_9

Boundary mixing in stratified reservoirs

Publisher: Cambridge University Press (CUP)

Date: 03-1993

DOI: 10.1017/S0022112093000850

Abstract: We consider the steady flow driven by turbulent mixing in a benthic boundary layer along a sloping boundary in the general case of a non-uniform background density gradient. The velocity and density fields are decomposed into barotropic and baroclinic components, and a solution is obtained by taking an expansion in the small parameter A , the aspect ratio of the boundary layer defined as the thickness ided by the alongslope length. The flow in the boundary layer is governed by a balance between alongslope baroclinic and barotropic density fluxes. A number of flow regimes can exist, and we show that in the regimes relevant to lakes and reservoirs, the barotropic flow is ergent and drives an exchange flow between the boundary layer and the interior. This leads to changes in the interior density gradient which are significant when compared to field observations.

The variability of the large-amplitude internal wave field on the Australian North West Shelf

Publisher: Elsevier BV

Date: 06-2009

DOI: 10.1016/J.CSR.2009.02.006

University Of Western Australia

Location: Australia

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University Of California, Berkeley

Location: United States of America

View Organisation

Linkage Projects - Grant ID: LP0776571

Start Date: 10-2007

End Date: 10-2011

Amount: $400,356.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP180101736

Start Date: 2018

End Date: 12-2022

Amount: $387,152.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0985221

Start Date: 2009

End Date: 04-2012

Amount: $360,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP1095294

Start Date: 2010

End Date: 12-2013

Amount: $430,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP150102638

Start Date: 2015

End Date: 12-2017

Amount: $286,100.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP210103131

Start Date: 2022

End Date: 12-2024

Amount: $370,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP120103036

Start Date: 2012

End Date: 03-2016

Amount: $520,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0663334

Start Date: 02-2006

End Date: 12-2008

Amount: $355,000.00

Funder: Australian Research Council

Industrial Transformation Research Hubs - Grant ID: IH140100012

Start Date: 04-2016

End Date: 12-2021

Amount: $4,997,672.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP130100856

Start Date: 07-2013

End Date: 03-2017

Amount: $412,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP110100017

Start Date: 10-2011

End Date: 11-2014

Amount: $559,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP210102745

Start Date: 2021

End Date: 12-2023

Amount: $772,031.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0346282

Start Date: 01-2003

End Date: 12-2006

Amount: $510,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP140101322

Start Date: 2014

End Date: 06-2017

Amount: $466,600.00

Funder: Australian Research Council

Super Science Fellowships - Grant ID: FS110200021

Start Date: 07-2011

End Date: 12-2014

Amount: $556,800.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE0561219

Start Date: 01-2005

End Date: 09-2006

Amount: $1,362,295.00

Funder: Australian Research Council

Industrial Transformation Research Hubs - Grant ID: IH200100009

Start Date: 07-2021

End Date: 06-2026

Amount: $5,000,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0664751

Start Date: 05-2006

End Date: 12-2009

Amount: $140,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP0454252

Start Date: 08-2004

End Date: 06-2009

Amount: $435,000.00

Funder: Australian Research Council