The Effects of Ice and Currents on Wave-breaking Turbulence at the Ocean Surface

The Effects of Ice and Currents on Wave-breaking Turbulence at the Ocean Surface
Author: Seth Zippel
Publisher:
Total Pages: 131
Release: 2017
Genre:
ISBN:

Breaking waves are critical to the exchange of momentum, gasses, and heat between the atmosphere and ocean. In open water, these exchanges control the growth and decay of waves, and have implications for global heat and gas budgets. However, local geophysical properties can significantly alter these exchanges. At river inlets, strong currents influence swell that has grown over a long ocean fetch, dramatically increasing surface fluxes. The reverse effect is seen in the presence of ice, where ocean wave properties are decoupled from atmospheric forcing, decreasing exchanges across the air/sea interface. Here, measurements of ocean waves and near surface turbulence are presented to show the modification of surface boundary processes from ice and currents. Measurements from free drifting buoys at the Mouth of the Columbia River are used to evaluate wave breaking parameterizations, where breaking occurs in intermediate depths and in the presence of vertically sheared currents. Breaking waves were identified using images collected with cameras onboard the buoys, and the breaking activity is well-correlated with wave steepness. Vertical shear in the currents produces a frequency-dependent effective current that modifies the linear dispersion relation. Accounting for these sheared currents in the wavenumber spectrum is essential in calculating the correct wave steepness; without this, wave steepness can be over (under) estimated on opposing (following) currents by up to 20%. The observed bulk wave steepness values suggest a limiting value of 0.4. The observed fraction of breaking waves is in good agreement with several existing models, each based on wave steepness. Further, a semi-spectral model designed for all depth regimes also compares favorably with measured breaking fractions. In this model, the majority of wave breaking is predicted to occur in the higher frequency bands (i.e., short waves). There is a residual dependance on directional spreading, in which wave breaking decreases with increasing directional spread. Observations at the Columbia River Mouth are also used to investigate the source and vertical structure of turbulence in the surface boundary layer. Turbulent velocity data collected onboard SWIFT buoys were corrected for platform motions to estimate turbulent kinetic energy (TKE) and TKE dissipation rates. Both of these quantities are correlated with wave steepness, which has been previously shown to determine wave breaking within the same dataset. Estimates of the turbulent length scale increase linearly with distance from the free surface, and roughness lengths estimated from velocity statistics scale with significant wave height. The vertical decay of turbulence is consistent with a balance between vertical diffusion and dissipation. Below a critical depth, a power law scaling commonly applied in the literature works well to fit the data. Above this depth, an exponential scaling fits the data well. These results, which are in a surface-following reference frame, are reconciled with results from the literature in a fixed reference frame. A mapping between free-surface referenced and mean-surface reference coordinates suggests 30% of the TKE is dissipated above the mean sea surface. Lastly, wind, wave, turbulence, and ice measurements from the Arctic Marginal Ice Zone are used to evaluate the response of the ocean surface to a given wind stress, with a focus on the local wind input to waves and subsequent ocean surface turbulence. Observations are from the Beaufort Sea in the summer and early fall of 2014, with fractional ice cover of up to 50%. Observations showed strong damping and directional modification of short waves, which, in turn, decreased the wind energy input to waves. Near-surface turbulent dissipation rates were also greatly reduced in partial ice cover. The reductions in waves and turbulence were balanced, suggesting that a wind-wave equilibrium is maintained in the marginal ice zone, though at levels much less than in open water. These results suggest that air-sea interactions are suppressed in the marginal ice zone relative to open ocean conditions at a given wind forcing, and this may act as a feedback mechanism in expanding a persistent marginal ice zone throughout the Arctic.

Turbulence in the Ocean

Turbulence in the Ocean
Author: Monin
Publisher: Springer Science & Business Media
Total Pages: 260
Release: 2012-12-06
Genre: Science
ISBN: 9400952171

Four years have elapsed since the preparation of the original Russian version of this book. This is a long time when dealing with such actively expanding fields of oceanography as research into small-scale structures and the investigation of hydro physical processes. Over this period new quick-response devices have been developed and successfully used for measurements taken in various ocean areas. Improvements in high-frequency meters used to measure hydrophysical parameters has enabled workers to obtain more accurate absolute values of the fluctuations measured by such devices. In view of this scientific progress, some of the ideas presented in this book now require additional explanation. Great care should be used in dealing with the absolute fluctuation values of hydro physical fields, since the methods used for the determination of the accuracy of the high-frequency measuring devices have been imperfect in the past. Never theless, it would appear that the results of the investigations summarized in this book have not lost their importance, and that the established laws governing small-scale pro cesses in the ocean are of a sufficiently universal nature and, as such, have not been shattered with the qualitative and quantitative advances in devices used for measurements taken in oceans. The authors feel that their work is of interest to English-speaking readers. The appearance of the English translation of the book is, to a very large extent, due to the tremendous amount of editing work brilliantly done by Prof. H. Tennekes.

The Interaction of Ocean Waves and Wind

The Interaction of Ocean Waves and Wind
Author: Peter Janssen
Publisher: Cambridge University Press
Total Pages: 310
Release: 2004-10-28
Genre: Science
ISBN: 0521465400

This book was published in 2004. The Interaction of Ocean Waves and Wind describes in detail the two-way interaction between wind and ocean waves and shows how ocean waves affect weather forecasting on timescales of 5 to 90 days. Winds generate ocean waves, but at the same time airflow is modified due to the loss of energy and momentum to the waves; thus, momentum loss from the atmosphere to the ocean depends on the state of the waves. This volume discusses ocean wave evolution according to the energy balance equation. An extensive overview of nonlinear transfer is given, and as a by-product the role of four-wave interactions in the generation of extreme events, such as freak waves, is discussed. Effects on ocean circulation are described. Coupled ocean-wave, atmosphere modelling gives improved weather and wave forecasts. This volume will interest ocean wave modellers, physicists and applied mathematicians, and engineers interested in shipping and coastal protection.

Elements of Physical Oceanography

Elements of Physical Oceanography
Author:
Publisher: Academic Press
Total Pages: 658
Release: 2009-08-26
Genre: Science
ISBN: 0123757215

Elements of Physical Oceanography is a derivative of the Encyclopedia of Ocean Sciences, Second Edition and serves as an important reference on current physical oceanography knowledge and expertise in one convenient and accessible source. Its selection of articles—all written by experts in their field—focuses on ocean physics, air-sea transfers, waves, mixing, ice, and the processes of transfer of properties such as heat, salinity, momentum and dissolved gases, within and into the ocean. Elements of Physical Oceanography serves as an ideal reference for topical research. References related articles in physical oceanography to facilitate further research Richly illustrated with figures and tables that aid in understanding key concepts Includes an introductory overview and then explores each topic in detail, making it useful to experts and graduate-level researchers Topical arrangement makes it the perfect desk reference

Oceanobs'19: An Ocean of Opportunity. Volume II

Oceanobs'19: An Ocean of Opportunity. Volume II
Author: Tong Lee
Publisher: Frontiers Media SA
Total Pages: 629
Release: 2020-12-31
Genre: Science
ISBN: 2889631192

This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact.

Ocean Circulation and Climate

Ocean Circulation and Climate
Author:
Publisher: Academic Press
Total Pages: 893
Release: 2013-10-22
Genre: Science
ISBN: 0123918537

The book represents all the knowledge we currently have on ocean circulation. It presents an up-to-date summary of the state of the science relating to the role of the oceans in the physical climate system. The book is structured to guide the reader through the wide range of world ocean circulation experiment (WOCE) science in a consistent way. Cross-references between contributors have been added, and the book has a comprehensive index and unified reference list. The book is simple to read, at the undergraduate level. It was written by the best scientists in the world who have collaborated to carry out years of experiments to better understand ocean circulation. - Presents in situ and remote observations with worldwide coverage - Provides theoretical understanding of processes within the ocean and at its boundaries to other Earth System components - Allows for simulating ocean and climate processes in the past, present and future using a hierarchy of physical-biogeochemical models

Air-Ice-Ocean Interaction

Air-Ice-Ocean Interaction
Author: Miles McPhee
Publisher: Springer
Total Pages: 0
Release: 2008-09-10
Genre: Science
ISBN: 9780387783345

At a time when the polar regions are undergoing rapid and unprecedented change, understanding exchanges of momentum, heat and salt at the ice-ocean interface is critical for realistically predicting the future state of sea ice. By offering a measurement platform largely unaffected by surface waves, drifting sea ice provides a unique laboratory for studying aspects of geophysical boundary layer flows that are extremely difficult to measure elsewhere. This book draws on both extensive observations and theoretical principles to develop a concise description of the impact of stress, rotation, and buoyancy on the turbulence scales that control exchanges between the atmosphere and underlying ocean when sea ice is present. Several interesting and unique observational data sets are used to illustrate different aspects of ice-ocean interaction ranging from the impact of salt on melting in the Greenland Sea marginal ice zone, to how nonlinearities in the equation of state for seawater affect mixing in the Weddell Sea. The book’s content, developed from a series of lectures, may be appropriate additional material for upper-level undergraduates and first-year graduate students studying the geophysics of sea ice and planetary boundary layers.

Ocean Mixing

Ocean Mixing
Author: Michael Meredith
Publisher: Elsevier
Total Pages: 386
Release: 2021-09-16
Genre: Science
ISBN: 0128215135

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

The Turbulent Ocean

The Turbulent Ocean
Author: S. A. Thorpe
Publisher: Cambridge University Press
Total Pages: 496
Release: 2005-10-27
Genre: Science
ISBN: 9781139445795

The subject of ocean turbulence is in a state of discovery and development with many intellectual challenges. This book describes the principal dynamic processes that control the distribution of turbulence, its dissipation of kinetic energy and its effects on the dispersion of properties such as heat, salinity, and dissolved or suspended matter in the deep ocean, the shallow coastal and the continental shelf seas. It focuses on the measurement of turbulence, and the consequences of turbulent motion in the oceanic boundary layers at the sea surface and near the seabed. Processes are illustrated by examples of laboratory experiments and field observations. The Turbulent Ocean provides an excellent resource for senior undergraduate and graduate courses, as well as an introduction and general overview for researchers. It will be of interest to all those involved in the study of fluid motion, in particular geophysical fluid mechanics, meteorology and the dynamics of lakes.