Download or read book Structure and Dynamics of Plumes Generated by Small Rivers written by Alexander Osadchiev and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The total share of small rivers in the influxes of fluvial water and suspended matter to the world ocean is estimated at between 25 and 40%. On a regional scale, this contribution can be even more significant for many coastal regions. In this chapter, we show that dynamics of small river plumes is significantly different from that of plumes generated by large rivers. Spatial structure of small plumes is generally characterized by sharper horizontal and vertical gradients. As a result, small plumes exhibit more energetic temporal variability in response to external forcing. In this chapter, we address several dynamical features typical for small plumes. We describe and discuss the response of small plumes to wind forcing and river discharge variability, the interaction between neighboring small plumes, and the generation of high-frequency internal waves in coastal ocean by small rivers. We also substantiate the Lagrangian approach to numerical modeling of small river plumes.

Download or read book River Plumes and Estuaries written by Alexander Osadchiev and published by Frontiers Media SA. This book was released on 2022-09-01 with total page 289 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Estuaries and Coastal Zones written by Jiayi Pan and published by BoD – Books on Demand. This book was released on 2020-03-25 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: Estuaries and their surrounding wetland regions are among the most productive ecosystems in the world, with more than half of humanity inhabiting their shores. Anthropogenic factors make estuaries highly susceptible to ecosystem degradation. Coastal waters are closely connected with human activity, and their dynamic processes may greatly affect coastal environments. This book provides a compendium of studies on estuarine dynamics, river plumes, and coastal water dynamics, studies that have investigated the changes in estuarine and coastal zones in response to sea-level rise and other environmental factors, and policy and management strategies to ensure the health and economy of coastal zones. This book aims to display novel frontiers in these fields and may help to inspire in-depth studies in the future.

Download or read book Impacts of Lateral Spreading and Upstream Conditions on Buoyant River Plumes written by Yeping Yuan and published by . This book was released on 2012 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation investigates the nature of physical processes associated with buoyant river plumes under the impacts of rotation, lateral spreading and upstream conditions. Two sets of laboratory experiments, one focused on the whole rotating buoyant plume, and the other zoomed into the near field plume, are studied. When lighter fluid is released into denser water, buoyancy causes the lighter intruding flow to run on top of the ambient water. This baroclinic flow propagates both in the offshore direction due to strong momentum from the inflow source and laterally in the alongshore direction because of the horizontal pressure gradient. This energetic region is the so-called near-field region where the plume behaves like a buoyant jet and is characterized by high momentum and strong stratification. Under the influence of the Coriolis force, the density driven flow is then guided along the coast, forming an anti-cyclonic bulge (in northern hemisphere). In this large scale region, called far-field region, the flow is more geophysical and less energetic. The transition between the two regions is the mid-field region in which the fluid transfers from an energetic flow into a geophysical current. The first laboratory experiment is designed to simulate the dynamics of two adjacent coastal river plumes in a rotating reference frame. The plumes are generated on a rotating table using two identical fresh water inlets, with blue and red dye indicating upstream and downstream river flows, respectively. We successfully calculate the depth field for the combined two-plume system and differentiate between the two plumes using a two-dimensional calibration map. With the upstream coastal current acting as the ambient condition, the downstream plume bulge does not reach a steady condition. The downstream bulge is pulled into the upstream bulge, forming a larger re-circulating bulge which then becomes unstable. The coastal current transport can be calculated by assuming a geostrophic cross-balance balance with an empirical coefficient & alpha = 0.6. The impact of lateral spreading on mixing was investigated for laboratory scale non-rotating stratified-shear plumes. The experiment is begun with the release of a vertical wall of freshwater and the simultaneous activation of a pump which supplies freshwater to the filling basin. Velocity and density fields are obtained using the combined particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) method, while the lateral spreading rate is determined using the optical thickness method (OTM). The vertical mixing is parameterized by the turbulent buoyancy flux, which is calculated using a control volume approach. Both the lateral spreading rate and mixing are related to inflow Fr, where the lateral spreading rate decreases with Fri while mixing increases with Fri. By comparing the mixing in the laterally confined and unconfined cases, we observe that although the lateral spreading significantly modifies the plume vertical structure, it does not change the local turbulent buoyancy flux. On the other hand, the lateral spreading increases the horizontal area over which mixing occurs and as a result it increases the net dilution of river water at a fixed distance from the river mouth. Unlike the local mixing process, we observe that the plume structure is significantly different in the laterally confined and unconfined plumes. Hypothesize is that the laterally spreading river plume might be a source of non-linear internal solitary waves with trapped cores. Such waves are commonly observed in fjords, straits and coastal ocean, where a strong shear-stratified flow meets dramatical topography changes. A series of small scale Kelvin-Helmholtz instability billows are generated along the edge of the large-scale waves, propagating downstream and finally breaking at the wave trough. This phenomenon highly increases the mixing and entrainment at the edge and trailing edges of the wave while it inhibits the mixing at the frontal side of the wave.

Download or read book Island Dynamical Systems Atmosphere Ocean and Biogeochemical Processes written by Rui Caldeira and published by Frontiers Media SA. This book was released on 2022-03-17 with total page 239 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Biogeochemical Dynamics at Major River Coastal Interfaces written by Thomas Bianchi and published by Cambridge University Press. This book was released on 2014 with total page 673 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive, state-of-the-art synthesis of biogeochemical dynamics and the impact of human alterations at major river-coastal interfaces for advanced students and researchers.

Download or read book Structure Dynamics and Mixing Processes in a Buoyant River Plume Entering a Fjord written by Rebecca Adam McPherson and published by . This book was released on 2018 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Fate and Dynamics of a River Plume in the Surf Zone written by Sam Kastner and published by . This book was released on 2020 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt: Small river outflows that directly enter the surf zone,where waves break near the shore, are a common feature of the world's coastlines. Rivers transport sediment, nutrients, and pollutants from the terrestrial to the marine environment, and the fate of this material is important for coastal morphology, ecology, and public health. Breaking waves release their energy and momentum in the surf zone, causing it to be energetic and turbulent, yet retentive, as surf zone cross-shore exchange is small on average. Thus, river water and river-borne material may become trapped in the surf zone. Trapped fresh river water is subject to energetic alongshore circulation and turbulence, and may be transported away from the river mouth, undergoing wave-driven mixing. Using observations from the Quinault River, which flows into an energetic surf zone on Quinault Indian Nation land north of Grays Harbor, WA, I investigate the interaction between river and wave forcing in the surf zone. By synthesizing data from moorings, drifters, and Unmanned Aerial System (UAS) video, I develop a conceptual model of this interaction based on river forcing, wave forcing, and the bathymetry near the river mouth. The relationships between these show how tides and bathymetry change the balance of wave and river momentum. Most frequently, wave forcing dominates over river forcing. Under these conditions the surf zone traps the outflowing river plume and the river water0́9s initial propagation into the surf zone is set by a plume length scale. When the river velocity is highest during low tide, and when wave forcing is low, river forcing dominates over wave forcing and river water escapes the surf zone. At high tide during low wave forcing, bathymetric effects can allow the river water to bypass wave forcing. In this case minimal wave breaking occurs in the channel and river water escapes onto the shelf. Estimates of entrainment velocity based on the drifter propagation distance indicate that mixing may be elevated above theoretical values in the near field plume by surf zone wave breaking. Based on the discharge, wave, and tidal conditions, I use the conceptual model to predict the fate of river water from the Quinault over a year, showing that approximately 70% of the river discharge is trapped in the surf zone upon exiting the river mouth. Drifter observations from the surf zone near the Quinault River mouth further indicate that the trapping of freshwater in the surf zone can result in high near-surface stratification. I investigate the rate that river water mixes with ocean water using two metrics: the rate of change of salinity in a Lagrangian reference frame, or material derivative of salinity, and the along track salinity variance. High mixing rates are observed concurrently with high near-surface stratification, as salinity gradients are collocated with wave breaking turbulence, which is unaffected by stratification. I observe a transition from low stratification and low mixing rate at low tidal stage to high stratification and high material derivative of salinity at high tidal stage as river discharge decreases. This decrease in surf zone freshwater content is driven by decreased river volume flux and increased wave-driven alongshore transport combining to export freshwater from the river mouth, and is well described by an analytical framework based on a continuously stirred reactor. In contrast with more commonly studied large river plume systems, lateral exchange and mixing could be significant, especially during periods of low stratification and at the surf zone edge. The results of this study may be applied to find the freshwater fraction of the surf zone as well as the alongshore propagation length scale of trapped river water, and to predict when such water would rapidly mix. Lastly, I synthesize these findings and offer a view of the surf zone from the perspective of trapped river water. Freshwater that is trapped in the surf zone interacts with surf zone features such as rip currents, alongshore currents, and the Stokes' drift-undertow circulation, as well as potentially altering cross-shore surf zone dynamics by introducing a baroclinic pressure gradient. As plume water propagates in the surf zone, it may undergo increased wave-driven mixing as near-surface stratification increases due to the surface intensification of wave breaking turbulence. These observations fall in line with previous work showing that wave driven mixing is greatest when the plume depth is shallow. Thus, the quantity of river water trapped in the surf zone is related to mixing, as the more river water is trapped, the less stratified the surf zone becomes, and less mixing occurs.

Download or read book Dynamics and Numerical Modeling of River Plumes in Lakes written by Navid Nekouee and published by . This book was released on 2010 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Models of the fate and transport of river plumes and the bacteria they carry into lakes are developed. They are needed to enable informed decisions about beach closures to avoid economic losses, and to help design water intakes and operate combined sewer overflow schemes to obviate exposure of the public to potential pathogens. This study advances our understanding of river plumes dynamics in coastal waters by means of field studies and numerical techniques. Extensive field measurements were carried out in the swimming seasons of 2006 and 2007 on the Grand River plume as it enters Lake Michigan. They included simultaneous aerial photography, measurements of lake physical properties, the addition of artificial tracers to track the plume, and bacterial sampling. Our observed results show more flow classes than included in previous studies (e.g. CORMIX). Onshore wind can have a significant effect on the plume and whether it impacts the shoreline. A new classification scheme based on the relative magnitude of plume-crossflow length scale and Richardson number based on the wind speed is devised. Previous studies on lateral spreading are complemented with a new relationship in the near field. The plume thickness decreased rapidly with distance from the river mouth and a new non-dimensional relationship to predict thickness is developed. Empirical near field models for surface buoyant plumes are reviewed and a near field trajectory and dilution model for large aspect ratio surface discharge channels is devised. Bacterial reductions due to dilution were generally small (less than 10:1) up to 4.5 km from the river mouth. E. coli decay rates were significantly affected by solar radiation and ranged from 0.2 to 2.2 day-1 which were within the range of previous studies in Lake Michigan. Total coliform survived longer than E. coli suggesting different die-off mechanisms. Mathematical models of the bacterial transport are developed that employ a nested modeling scheme to represent the 3D hydrodynamic processes of surface river discharges in the Great Lakes. A particle tracking model is used that provides the capability to track a decaying tracer and better quantify mixing due to turbulent diffusion. Particle tracking models have considerable advantages over gradient diffusion models in simulating bacterial behavior nearshore that results in an improved representation of bacteria diffusion, decay and transport. Due to the complexity and wide variation of the time and length scale of the hydrodynamic and turbulent processes in the near field (where plume mixing is dominated by initial momentum and buoyancy) and far field (where plume mixing is dominated by ambient turbulence), a coupling technique is adapted. The far field random walk particle tracking model incorporates the empirical near field model. It simulates the transport, diffusion and decay of bacteria as discrete particles and employs the near field output as the source and transports the particles based on ambient currents predicted by the 3D hydrodynamic model. The coupled model improves dilution predictions in the near field. The new techniques advance our knowledge of the nearshore fate and transport of bacteria in the Great Lakes and can be ultimately applied to the NOAA Great Lakes Coastal Forecasting System to provide a reliable prediction tool for bacterial transport in recreational waters."--Summary.

Download or read book Contemporary Issues in Estuarine Physics written by Arnoldo Valle-Levinson and published by Cambridge University Press. This book was released on 2010-01-28 with total page 327 pages. Available in PDF, EPUB and Kindle. Book excerpt: Estuaries are of high socioeconomic importance with twenty-two of the thirty-two largest cities in the world located on river estuaries. Estuaries bring together fluxes of fresh and saline water, as well as fluvial and marine sediments, and contain high biological diversity. Increasingly sophisticated field observation technology and numerical modeling have produced significant advances in our understanding of the physical properties of estuaries over the last decade. This book introduces a classification for estuaries before presenting the basic physics and hydrodynamics of estuarine circulation and the various factors that modify it in time and space. It then covers special topics at the forefront of research such as turbulence, fronts in estuaries and continental shelves, low inflow estuaries, and implications of estuarine transport for water quality. Written by leading authorities on estuarine and lagoon hydrodynamics, this volume provides a concise foundation for academic researchers, advanced students and coastal resource managers.

Download or read book The Dynamics of Buoyant Rotational River Plumes written by Alexander R. Horner-Devine and published by . This book was released on 2003 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Treatise on Estuarine and Coastal Science written by and published by Academic Press. This book was released on 2012-03-06 with total page 4604 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of estuaries and coasts has seen enormous growth in recent years, since changes in these areas have a large effect on the food chain, as well as on the physics and chemistry of the ocean. As the coasts and river banks around the world become more densely populated, the pressure on these ecosystems intensifies, putting a new focus on environmental, socio-economic and policy issues. Written by a team of international expert scientists, under the guidance of Chief Editors Eric Wolanski and Donald McClusky, the Treatise on Estuarine and Coastal Science, Ten Volume Set examines topics in depth, and aims to provide a comprehensive scientific resource for all professionals and students in the area of estuarine and coastal science Most up-to-date reference for system-based coastal and estuarine science and management, from the inland watershed to the ocean shelf Chief editors have assembled a world-class team of volume editors and contributing authors Approach focuses on the physical, biological, chemistry, ecosystem, human, ecological and economics processes, to show how to best use multidisciplinary science to ensure earth's sustainability Provides a comprehensive scientific resource for all professionals and students in the area of estuarine and coastal science Features up-to-date chapters covering a full range of topics

Download or read book Turbulent Jets and Plumes written by Joseph Hun-wei Lee and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 391 pages. Available in PDF, EPUB and Kindle. Book excerpt: Jets and plumes are shear flows produced by momentum and buoyancy forces. Examples include smokestack emissions, fires and volcano eruptions, deep sea vents, thermals, sewage discharges, thermal effluents from power stations, and ocean dumping of sludge. Knowledge of turbulent mixing by jets and plumes is important for environmental control, impact and risk assessment. Turbulent Jets and Plumes introduces the fundamental concepts and develops a Lagrangian approach to model these shear flows. This theme persists throughout the text, starting from simple cases and building towards the practically important case of a turbulent buoyant jet in a density-stratified crossflow. Basic ideas are illustrated by ample use of flow visualization using the laser-induced fluorescence technique. The text includes many illustrative worked examples, comparisons of model predictions with laboratory and field data, and classroom tested problems. An interactive PC-based virtual-reality modelling software (VISJET) is also provided. Engineering and science students, researchers and practitioners may use the book both as an introduction to the subject and as a reference in hydraulics and environmental fluid mechanics.

Download or read book Dynamics of the Columbia River Tidal Plume written by Levi F. Kilcher and published by . This book was released on 2011 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation investigates the dynamics of the tidally modulated outflow from the Columbia River mouth using high resolution measurements of velocity, density and turbulent microstructure. At high tide, flow through the river mouth reverses from flood (onshore) to ebb (offshore). During ebb, buoyant fluid issues from the river mouth and spreads offshore across the ocean surface. This is the Columbia River tidal plume. The fluid velocity of the tidal plume is super-critical (greater than the wavespeed of coastal stratification), which creates a zone of sharp surface velocity convergence at its leading edge, causing a front to form. From early ebb to peak ebb, constant front propagation speed and plume expansion rate are controlled by a linearly increasing volume-flux through the river mouth. Within the plume, turbulence at the plume base is strongly related to the difference between the shear-squared, S2, and four times the buoyancy frequency squared, 4N2. A parameterization based on the excess shear-squared, S2 - 4N2, represents Reynolds stress well, indicating that it is driven by Kelvin-Helmholtz instability. During peak ebb of large tides, high volume-flux through the mouth drives high S2 - 4N2, causing high plume-base stress, which forces significant deceleration of the plume. During smaller tides the volume-flux is smaller, S2 - 4N2 lower, and the stress too weak to significantly decelerate the plume. During mid-ebb of both small and large ebbs, increasing buoyancy flux from the river mouth raises plume stratification, which suppresses S2 - 4N2 and stress. As ebb ends, decreasing volume flux and deflection by the Coriolis effect limit plume expansion. This weakens surface velocity convergence, causing the front to diffuse. On longer timescales, plume N2 is modulated by changes in river flow; higher river flow causes higher N2. During peak ebb of large tides this increase in N2 supports higher S2, resulting in higher S2 - 4N2, which causes larger internal stress. These results describe the primary dynamics of the Columbia River tidal plume from front formation to late-ebb, and relate variability in those dynamics to tidal and river-flow forcing.

Download or read book Dynamics of Freshwater Plumes Observations and Numerical Modeling of the Wind Forced Response and Alongshore Freshwater Transport written by and published by . This book was released on 1998 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: A plume often results when a river discharges fresh water into the nearshore waters. This thesis combines both hydrographic data and idealized numerical simulations to examine how ambient currents and winds influence the transport and mixing of plume waters. The alongshore transport of freshwater is studied using a numerical model. In the absence of ambient currents, the downstream coastal current only carries a fraction of the discharged fresh water; the remaining fraction recirculates in a continually growing "bulge" in the vicinity of the river mouth. The presence of an ambient current augments the freshwater transport in the coastal current so that it matches the freshwater source. The thesis also studies the wind-induced advection and mixing of a river plume, using data collected in the western Gulf of Maine (GOM) and idealized numerical modeling experiments. The cross-shore structure of the GOM plume varies as a function of fluctuations in alongshore wind forcing. Estimates of the alongshore momentum balance indicate an approximate Ekman balance. The model simulations of a plume forced by upwelling winds demonstrate that the plume thins and is advected offshore by the cross-shore Ekman transport. The thinned plume is susceptible to significant mixing because of the sheared horizontal currents.

Download or read book Wind and Wave influenced Mixing and Dynamics in the Fraser River Plume written by Samuel Kastner and published by . This book was released on 2018 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rivers play a large role in the transport of matter between ecosystems by connecting interior regions with lakes and oceans. River outflows, or plumes, constitute a significant delivery mechanism of pollutants, sediment, and nutrients to the coastal environment. Such plumes are common along the worlds coastlines, but are poorly understood and difficult to sample due to their complexity. The effects of external forcing (such as winds and waves) on river plumes is particularly understudied, but has been shown to play a role in the behavior of the plume. The Fraser River (the site of proposed and existing oil infrastructure) is a key system to understand, as its mouth is near both a major population center (Vancouver, BC) and unique coastal ecosystems. This study presents observations of plume mixing and stream-normal momentum balances in the Fraser river plume using Lagrangian surface drifters. The Strait of Georgia commonly experiences calm to moderate winds from the Southeast and strong storm winds from the Northwest in the winter, and there are differences in plume behavior between these conditions. Under SE winds, the plume thins, spreads, and turns to the right (North) upon exiting the river mouth, mixing intensely for a short period of time. This process is dominated by a balance between stream-normal pressure gradient, Coriolis, and rotational acceleration, as previous studies have shown. Under NW winds, the plume stays thicker, narrower, and flows directly across the Strait while forming a lateral front on its northern side, mixing at a slower rate for longer. Different momentum terms dominate under this wind condition: the stream- normal balance pits Coriolis and rotational acceleration pressure gradient against interfacial shear stress, wind stress, wave radiation stress gradient, and ambient current body force. The two configurations of the plume show that variable winds can have a substantial impact on the shape of the plume, which can lead to changes in the sea surface anomaly associated with the dome of freshwater exiting the river mouth. Additionally, while spreading causes the plume to mix intensely under SE winds, the net mixing under NW winds is larger due to the longer extent of the plume. This indicates that large spreading is not always necessary for substantial plume mixing. Understanding the conditions that change plume mixing and behavior is a critical step in describing the pathways of pollutants, sediment, and nutrients as they enter the coastal ecosystem through a river plume.

Download or read book Meteorology of the Southern Hemisphere written by David Karoly and published by Springer. This book was released on 2015-04-03 with total page 413 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book looks at the circulation features of the Southern Hemisphere, both for the atmosphere and oceans. It includes observational techniques based on satellites, anchored and drifting buoys, and the research carried out at research stations in the Southern Hemisphere. The book was originally published in 1972 by the American Meteorological Society. It has been revised and updated in 1999, following the expansion of research bases and the development of research in the region at the time.