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Author: Laur Ferris
Publisher:
ISBN:
Category : Internal waves
Languages : en
Pages : 0
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Book Description
Numerous physics are responsible for forward energy cascade at oceanic fronts but their roles are not fully clear. This dissertation investigates wind-sheared turbulence in the ocean surface boundary layer (OSBL), internal wave interactions in the ocean interior, and instability-driven turbulence in energetic jets; with attention paid to the parameterizations used to quantify them. At the OSBL, meteorological forcing injects turbulent kinetic energy (TKE), mixing the upper ocean and rapidly transforming its density structure. In the absence of direct observations or capability to resolve sub-grid scale turbulence in ocean models, the community relies on boundary layer scalings (BLS) of shear and convective turbulence to represent this mixing. Despite the importance of near-surface mixing, ubiquitous BLS representations of these processes have been underassessed in high energy forcing regimes such as the Southern Ocean. Glider microstructure from AUSSOM (Autonomous Sampling of Southern Ocean Mixing), a long-duration glider mission, is leveraged to show BLS of shear turbulence exhibits a consistent bias in estimating TKE dissipation rates in the OSBL. In the interior, finescale strain parameterization (FSP) of the TKE dissipation rate has become a widely used method for observing mixing, solving a coverage problem where only CTD profiles are available. However there are limitations in its application to intense frontal regions where adjacent warm/salty and cold/fresh waters create double diffusive instability. Direct turbulence measurements from DIMES (Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean) and AUSSOM are used to show FSP can have biases of up to 8 orders of magnitude below the mixed layer when physics associated with T/S fronts are present. FSP often fails to produce reliable results in frontal zones where temperature-salinity (T/S) intrusive features contaminate the CTD strain spectrum, as well as where the aspect ratio of the internal wave spectrum is known to vary greatly with depth (as in the Southern Ocean). We propose that the FSP methodology be modified to include a density ratio-based data exclusion rule to avoid contamination by double diffusive instabilities in frontal zones. At energetic frontal jets, symmetric instability (SI) has gained momentum for explaining enhanced turbulence. Submesoscale frontal instabilities are well-established by idealized analytical and numerical studies to be a significant source of TKE in the global ocean. However, observations of TKE dissipation enhanced by SI are few, and it is unknown to what order in the real ocean this process is active. AUSSOM measured elevated TKE dissipation rates throughout the core of the Polar Front (PF). Motivated by this finding, we use a 1-km Regional Ocean Modeling System hindcast to investigate the role of SI in energy cascade and Southern Ocean mixing. We extend popular overturning instability criteria for application to ageostrophic flows. SI of the centrifugal/inertial variety is widespread along the northern continental margins of the Antarctic Circumpolar Current due to topographic shearing of the anticyclonic side of PF-associated jets but is notably limited (above 1-km scale) to the mixed layer at open-ocean fronts. Contrarily, modeled velocity fields are strongly indicative of critical layers and other internal wave interactions dominating the open-ocean elevated TKE budget even at energetic fronts.
Author: Laur Ferris
Publisher:
ISBN:
Category : Internal waves
Languages : en
Pages : 0
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Book Description
Numerous physics are responsible for forward energy cascade at oceanic fronts but their roles are not fully clear. This dissertation investigates wind-sheared turbulence in the ocean surface boundary layer (OSBL), internal wave interactions in the ocean interior, and instability-driven turbulence in energetic jets; with attention paid to the parameterizations used to quantify them. At the OSBL, meteorological forcing injects turbulent kinetic energy (TKE), mixing the upper ocean and rapidly transforming its density structure. In the absence of direct observations or capability to resolve sub-grid scale turbulence in ocean models, the community relies on boundary layer scalings (BLS) of shear and convective turbulence to represent this mixing. Despite the importance of near-surface mixing, ubiquitous BLS representations of these processes have been underassessed in high energy forcing regimes such as the Southern Ocean. Glider microstructure from AUSSOM (Autonomous Sampling of Southern Ocean Mixing), a long-duration glider mission, is leveraged to show BLS of shear turbulence exhibits a consistent bias in estimating TKE dissipation rates in the OSBL. In the interior, finescale strain parameterization (FSP) of the TKE dissipation rate has become a widely used method for observing mixing, solving a coverage problem where only CTD profiles are available. However there are limitations in its application to intense frontal regions where adjacent warm/salty and cold/fresh waters create double diffusive instability. Direct turbulence measurements from DIMES (Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean) and AUSSOM are used to show FSP can have biases of up to 8 orders of magnitude below the mixed layer when physics associated with T/S fronts are present. FSP often fails to produce reliable results in frontal zones where temperature-salinity (T/S) intrusive features contaminate the CTD strain spectrum, as well as where the aspect ratio of the internal wave spectrum is known to vary greatly with depth (as in the Southern Ocean). We propose that the FSP methodology be modified to include a density ratio-based data exclusion rule to avoid contamination by double diffusive instabilities in frontal zones. At energetic frontal jets, symmetric instability (SI) has gained momentum for explaining enhanced turbulence. Submesoscale frontal instabilities are well-established by idealized analytical and numerical studies to be a significant source of TKE in the global ocean. However, observations of TKE dissipation enhanced by SI are few, and it is unknown to what order in the real ocean this process is active. AUSSOM measured elevated TKE dissipation rates throughout the core of the Polar Front (PF). Motivated by this finding, we use a 1-km Regional Ocean Modeling System hindcast to investigate the role of SI in energy cascade and Southern Ocean mixing. We extend popular overturning instability criteria for application to ageostrophic flows. SI of the centrifugal/inertial variety is widespread along the northern continental margins of the Antarctic Circumpolar Current due to topographic shearing of the anticyclonic side of PF-associated jets but is notably limited (above 1-km scale) to the mixed layer at open-ocean fronts. Contrarily, modeled velocity fields are strongly indicative of critical layers and other internal wave interactions dominating the open-ocean elevated TKE budget even at energetic fronts.
Author: Michael Meredith
Publisher: Elsevier
ISBN: 0128215135
Category : Science
Languages : en
Pages : 386
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Book Description
Ocean Mixing: Drivers, Mechanisms and Impacts presents a broad panorama of one of the most rapidly-developing areas of marine science. It highlights the state-of-the-art concerning knowledge of the causes of ocean mixing, and a perspective on the implications for ocean circulation, climate, biogeochemistry and the marine ecosystem. This edited volume places a particular emphasis on elucidating the key future questions relating to ocean mixing, and emerging ideas and activities to address them, including innovative technology developments and advances in methodology. Ocean Mixing is a key reference for those entering the field, and for those seeking a comprehensive overview of how the key current issues are being addressed and what the priorities for future research are. Each chapter is written by established leaders in ocean mixing research; the volume is thus suitable for those seeking specific detailed information on sub-topics, as well as those seeking a broad synopsis of current understanding. It provides useful ammunition for those pursuing funding for specific future research campaigns, by being an authoritative source concerning key scientific goals in the short, medium and long term. Additionally, the chapters contain bespoke and informative graphics that can be used in teaching and science communication to convey the complex concepts and phenomena in easily accessible ways. - Presents a coherent overview of the state-of-the-art research concerning ocean mixing - Provides an in-depth discussion of how ocean mixing impacts all scales of the planetary system - Includes elucidation of the grand challenges in ocean mixing, and how they might be addressed
Author: Carsten Eden
Publisher: Springer
ISBN: 3030057046
Category : Computers
Languages : en
Pages : 312
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Book Description
This book describes a recent effort combining interdisciplinary expertise within the Collaborative Research Centre “Energy transfers in atmosphere and ocean” (TRR-181), which was funded by the German Research Foundation (DFG). Energy transfers between the three dynamical regimes – small-scale turbulence, internal gravity waves and geostrophically balanced motion – are fundamental to the energy cycle of both the atmosphere and the ocean. Nonetheless, they remain poorly understood and quantified, and have yet to be adequately represented in today’s climate models. Since interactions between the dynamical regimes ultimately link the smallest scales to the largest ones through a range of complex processes, understanding these interactions is essential to constructing atmosphere and ocean models and to predicting the future climate. To this end, TRR 181 combines expertise in applied mathematics, meteorology, and physical oceanography. This book provides an overview of representative specific topics addressed by TRR 181, ranging from - a review of a coherent hierarchy of models using consistent scaling and approximations, and revealing the underlying Hamiltonian structure - a systematic derivation and implementation of stochastic and backscatter parameterisations - an exploration of the dissipation of large-scale mean or eddying balanced flow and ocean eddy parameterisations; and - a study on gravity wave breaking and mixing, the interaction of waves with the mean flow and stratification, wave-wave interactions and gravity wave parameterisations to topics of a more numerical nature such as the spurious mixing and dissipation of advection schemes, and direct numerical simulations of surface waves at the air-sea interface. In TRR 181, the process-oriented topics presented here are complemented by an operationally oriented synthesis focusing on two climate models currently being developed in Germany. In this way, the goal of TRR 181 is to help reduce the biases in and increase the accuracy of atmosphere and ocean models, and ultimately to improve climate models and climate predictions.
Author: Matthew W. Hecht
Publisher: John Wiley & Sons
ISBN: 1118671996
Category : Science
Languages : en
Pages : 654
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Book Description
Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 177. This monograph is the first to survey progress in realistic simulation in a strongly eddying regime made possible by recent increases in computational capability. Its contributors comprise the leading researchers in this important and constantly evolving field. Divided into three parts Oceanographic Processes and Regimes: Fundamental Questions Ocean Dynamics and State: From Regional to Global Scale, and Modeling at the Mesoscale: State of the Art and Future Directions The volume details important advances in physical oceanography based on eddy resolving ocean modeling. It captures the state of the art and discusses issues that ocean modelers must consider in order to effectively contribute to advancing current knowledge, from subtleties of the underlying fluid dynamical equations to meaningful comparison with oceanographic observations and leading-edge model development. It summarizes many of the important results which have emerged from ocean modeling in an eddying regime, for those interested broadly in the physical science. More technical topics are intended to address the concerns of those actively working in the field.
Author: Manuel Othon Gutierrez Villanueva
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The Antarctic Circumpolar Current (ACC) and the Southern Ocean meridional overturning circulation are dynamically linked through interactions between the mean flow, eddies, and mixing by breaking internal lee waves over rough topography. However, quantifying the time-mean and the spatio-temporal variability of the ACC transport, eddy fluxes, and small-scale mixing remains challenging as observations are scarce. This thesis work analyzes the mean eddy heat flux, finescale internal-wave-driven turbulence, and transport of the ACC in Drake Passage, and it examines the possible physical processes driving the spatial and temporal variability of these quantities. First, the eddy heat flux as a function of ACC streamlines is quantified using a unique 20-year time series of upper ocean temperature and velocity transects with unprecedented horizontal resolution. Using the time-varying streamlines, the across-ACC eddy heat flux is maximum poleward in the south flank of the Subantarctic Front and it reduces towards the south, becoming statistically insignificant in the Polar Front. These results indicate heat convergence south of the Subantarctic Front. Second, a unique four-year time series of stratification and near-bottom currents, and finestructure density and velocity profiles were employed to estimate the expected linear lee-wave energy and infer turbulent dissipation due to breaking internal waves. In contrast to idealized numerical predictions of 50% local dissipation of lee-wave energy, less than 10% dissipated locally regardless of the abyssal hill topographic representation. Third, the high-spatial-resolution time series of temperature, salinity, and velocity are used to identify trends in the Drake Passage total and geostrophic transport in the upper kilometer. We uniquely found that the Subantarctic Front and Polar Front, the two major ACC fronts, have significantly accelerated during the last decade whereas the area between these fronts and between the Polar Front and the Southern ACC Front has decelerated. These opposite trends compensate such that no significant trend is discernible in the total and geostrophic transport integrated across Drake Passage. We suggest the acceleration of the fronts is driven by an increase in the eddy activity in between the fronts.
Author: International Southern Ocean Studies. Working Group on Theoretical and Special Process Studies. Summer Session
Publisher:
ISBN:
Category : International Decade of Ocean Exploration, 1970-1980
Languages : en
Pages : 546
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Book Description
Author: Peter S. Liss
Publisher: Springer
ISBN: 3642256430
Category : Science
Languages : en
Pages : 366
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Book Description
The oceans and atmosphere interact through various processes, including the transfer of momentum, heat, gases and particles. In this book leading international experts come together to provide a state-of-the-art account of these exchanges and their role in the Earth-system, with particular focus on gases and particles. Chapters in the book cover: i) the ocean-atmosphere exchange of short-lived trace gases; ii) mechanisms and models of interfacial exchange (including transfer velocity parameterisations); iii) ocean-atmosphere exchange of the greenhouse gases carbon dioxide, methane and nitrous oxide; iv) ocean atmosphere exchange of particles and v) current and future data collection and synthesis efforts. The scope of the book extends to the biogeochemical responses to emitted / deposited material and interactions and feedbacks in the wider Earth-system context. This work constitutes a highly detailed synthesis and reference; of interest to higher-level university students (Masters, PhD) and researchers in ocean-atmosphere interactions and related fields (Earth-system science, marine / atmospheric biogeochemistry / climate). Production of this book was supported and funded by the EU COST Action 735 and coordinated by the International SOLAS (Surface Ocean- Lower Atmosphere Study) project office.
Author: Godae GODAE OceanView
Publisher: Createspace Independent Publishing Platform
ISBN: 9781720549970
Category :
Languages : en
Pages : 812
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Book Description
The implementation of operational oceanography in the past 15 years has provided many societal benefits and has led to many countries adopting a formal roadmap for providing ocean forecasts. Continuing the tradition of two very successful international summer schools held in France in 2004 (Chassignet and Verron, 2006) and in Australia in 2010 (Schiller and Brassington, 2011), a third international school that focused on frontier research in operational oceanography was held in Majorca in 2017. In the coming years, graduate students and young scientists will be challenged by many new observations (SWOT, Sentinel, AUVs, floats, etc.), complex high resolution numerical models and data assimilation (high resolution, predictability, uncertainty, changing computing platforms, etc.), and the need to work on many scales (open ocean-shelf interactions, coupled ocean-ice-atmosphere, biogeochemistry, etc.). The latter school brought together senior experts and young researchers (pre- and post-doctorate) from across the world and exposed them to the latest research in oceanography, specifically how it will impact operational oceanography. This book is a compilation of the lectures presented at the school and presents a summary of the current state-of-the-art in operational oceanography research. About the Editors: Eric P. Chassignet is a professor of Physical Oceanography in the Department of Earth, Ocean and Atmospheric Science and director of the Center for Ocean-Atmospheric Prediction Studies at Florida State University (Tallahassee, FL, USA). Ananda Pascual is a research scientist at the Instituto Mediterráneo de Estudios Avanzados, IMEDEA(CSIC-UIB) in Esporles (Majorca, Spain). Joaquin Tintore is professor of Physical Oceanography at IMEDEA and director of SOCIB (Sistema d'Observacio iPredictio Coastaner de les Iles Balears) in Palma (Majorca, Spain). Jacques Verron is a senior research scientist emeritus at the Institut des Geosciences de l'Environnement (IGE) (Grenoble, France). About GODAE OceanView: GODAE OceanView provides coordination and leadership in consolidating and improving global and regional ocean analysis and forecasting systems on an international level. It encourages international collaboration to address the scientific and technical challenges associated with operational oceanography. It also fosters research that will lead to the enhancement of existing systems and the development of next generation of ocean prediction systems.
Author: Dirk Olbers
Publisher: Springer Science & Business Media
ISBN: 364223450X
Category : Science
Languages : en
Pages : 717
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Book Description
Ocean Dynamics’ is a concise introduction to the fundamentals of fluid mechanics, non-equilibrium thermodynamics and the common approximations for geophysical fluid dynamics, presenting a comprehensive approach to large-scale ocean circulation theory. The book is written on the physical and mathematical level of graduate students in theoretical courses of physical oceanography, meteorology and environmental physics. An extensive bibliography and index, extensive side notes and recommendations for further reading, and a comparison with the specific atmospheric physics where applicable, makes this volume also a useful reading for researchers. Each of the four parts of the book – fundamental laws, common approximations, ocean waves, oceanic turbulence and eddies, and selected aspects of ocean dynamics – starts with elementary considerations, blending then classical topics with more advanced developments of fluid mechanics and theoretical oceanography. The last part covers the theory of the global wind-driven circulation in homogeneous and stratified regimes, the circulation and overturning in the Southern Ocean, and the global meridional overturning and thermohaline-driven circulation. Emphasis is placed on simple physical models rather than access to extensive numerical results, enabling students to understand and reproduce the complex theory mostly by analytical means. All equations and models are derived in detail and illustrated by numerous figures. The appendix provides short excursions into the mathematical background, such as vector analysis, statistics, and differential equations
Author: Vittorio Barale
Publisher: Springer Science & Business Media
ISBN: 9048186811
Category : Technology & Engineering
Languages : en
Pages : 378
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Book Description
To all those sailors / Who dreamed before us / Of another way to sail the oceans. The dedication of this Volume is meant to recall, and honour, the bold pioneers of ocean exploration, ancient as well as modern. As a marine scientist, dealing with the oceans through the complex tools, ?lters and mechanisms of contemporary research, I have always wondered what it was like, in centuries past, to look at that vast ho- zon with the naked eye, not knowing what was ahead, and yet to sail on. I have tried to imagine what ancient sailors felt, when “the unknown swirls around and engulfs the mind”, as a forgotten author simply described the brave, perhaps reckless, act of facing such a hostile, menacing and yet fascinating adventure. Innovation has always been the key element, I think, for their success: another way, a better way, a more effective, safer and worthier way was the proper answer to the challenge. The map of our world has been changed time and again, from the geographical as well as the social, economic and scienti?c points of view, by the new discoveries of those sailors. One of the positive qualities of human beings is without doubt the inborn desire to expand their horizons, to see what lies beyond, to learn and understand.
