1. Introduction 2. Observation techniques 3. Description of ocean waves 4. Statistics 5. Linear wave theory (oceanic waters) 6. Waves in oceanic waters 7. Linear wave theory (coastal waters) 8. Waves in coastal waters 9. The SWAN wave model Appendices References Index.

/pdf/waves-in-oceanic-and-coastal-waters-6ofdu4icqi.pdf

Waves in Oceanic and Coastal Waters

The most recent IPCC assessment has shown an important role for negative emissions technologies (NETs) in limiting global warming to 2 °C cost-effectively. However, a bottom-up, systematic, reproducible, and transparent literature assessment of the different options to remove CO2 from the atmosphere is currently missing. In part 1 of this three-part review on NETs, we assemble a comprehensive set of the relevant literature so far published, focusing on seven technologies: bioenergy with carbon capture and storage (BECCS), afforestation and reforestation, direct air carbon capture and storage (DACCS), enhanced weathering, ocean fertilisation, biochar, and soil carbon sequestration. In this part, part 2 of the review, we present estimates of costs, potentials, and side-effects for these technologies, and qualify them with the authors' assessment. Part 3 reviews the innovation and scaling challenges that must be addressed to realise NETs deployment as a viable climate mitigation strategy. Based on a systematic review of the literature, our best estimates for sustainable global NET potentials in 2050 are 0.5–3.6 GtCO₂ yr⁻¹ for afforestation and reforestation, 0.5–5 GtCO₂ yr⁻¹ for BECCS, 0.5–2 GtCO₂ yr⁻¹ for biochar, 2–4 GtCO₂ yr⁻¹ for enhanced weathering, 0.5–5 GtCO₂ yr⁻¹ for DACCS, and up to 5 GtCO2 yr⁻¹ for soil carbon sequestration. Costs vary widely across the technologies, as do their permanency and cumulative potentials beyond 2050. It is unlikely that a single NET will be able to sustainably meet the rates of carbon uptake described in integrated assessment pathways consistent with 1.5 °C of global warming.

https://iopscience.iop.org/article/10.1088/1748-9326/aabf9f/pdf

Negative emissions-Part 2 : Costs, potentials and side effects

The ocean circulation is a cause and consequence of fluid scale interactions ranging from millimeters to more than 10,000 km. Although the wind field produces a large energy input to the ocean, all but approximately 10% appears to be dissipated within about 100 m of the sea surface, rendering observations of the energy divergence necessary to maintain the full water-column flow difficult. Attention thus shifts to the physically different kinetic energy (KE) reservoirs of the circulation and their maintenance, dissipation, and possible influence on the very small scales representing irreversible molecular mixing. Oceanic KE is dominated by the geostrophic eddy field, and depending on the vertical structure (barotropic versus low-mode baroclinic), direct and inverse energy cascades are possible. The pathways toward dissipation of the dominant geostrophic eddy KE depend crucially on the direction of the cascade but are difficult to quantify because of serious observational difficulties for wavelengths shorte...

Ocean Circulation Kinetic Energy: Reservoirs, Sources, and Sinks

According to small subunit ribosomal RNA (ss rRNA) sequence comparisons all known Archaea belong to the phyla Crenarchaeota, Euryarchaeota, and--indicated only by environmental DNA sequences--to the 'Korarchaeota'. Here we report the cultivation of a new nanosized hyperthermophilic archaeon from a submarine hot vent. This archaeon cannot be attached to one of these groups and therefore must represent an unknown phylum which we name 'Nanoarchaeota' and species, which we name 'Nanoarchaeum equitans'. Cells of 'N. equitans' are spherical, and only about 400 nm in diameter. They grow attached to the surface of a specific archaeal host, a new member of the genus Ignicoccus. The distribution of the 'Nanoarchaeota' is so far unknown. Owing to their unusual ss rRNA sequence, members remained undetectable by commonly used ecological studies based on the polymerase chain reaction. 'N. equitans' harbours the smallest archaeal genome; it is only 0.5 megabases in size. This organism will provide insight into the evolution of thermophily, of tiny genomes and of interspecies communication.

A new phylum of Archaea represented by a nanosized hyperthermophilic symbiont

New parameterizations for the spectral dissipation of wind-generated waves are proposed. The rates of dissipation have no predetermined spectral shapes and are functions of the wave spectrum and wind speed and direction, in a way consistent with observations of wave breaking and swell dissipation properties. Namely, the swell dissipation is nonlinear and proportional to the swell steepness, and dissipation due to wave breaking is nonzero only when a nondimensional spectrum exceeds the threshold at which waves are observed to start breaking. An additional source of short-wave dissipation is introduced to represent the dissipation of short waves due to longer breaking waves. A reduction of the wind-wave generation of short waves is meant to account for the momentum flux absorbed by longer waves. These parameterizations are combined and calibrated with the discrete interaction approximation for the nonlinear interactions. Parameters are adjusted to reproduce observed shapes of directional wave spect...

/pdf/semiempirical-dissipation-source-functions-for-ocean-waves-37ztodek8d.pdf

Semiempirical Dissipation Source Functions for Ocean Waves. Part I: Definition, Calibration, and Validation

The spectral balances involved in shaping the short gravity wave region of the ocean wave-height spectrum have been the subject of recent physical models. In terms of the wind friction velocity u*, gravitational acceleration g and local wavenumber k, these models predict a wavenumber dependence of , where k = |k|, and a linear dependence on u* for the equilibrium range of gravity waves above the spectral peak. In this paper we present the results of an experimental determination of the wavenumber spectrum for the wavelength range of 0.2−1.6 m, based on stereophotogrammetric determinations from an oil platform under open ocean conditions.From our observations, for this wavenumber range, the one-dimensional equilibrium wavenumber spectrum was determined as
 \[
 \phi (k_i) \sim \left(\frac{u^2_*k}{g}\right)^{\gamma} k^{-3}_{i}\;\;\;\;\;\;\;(i=1,2 \;\;\; K = (k_1,k_2))
 \]
 where γ = 0.09±0.09 at the 95% confidence level. These limits embrace wind-independent approximations to the observed one-dimensional and two-dimensional wavenumber spectra of the form
 \[
 \phi (k_i) \sim B k^{-3}_i \;\;\; (i = 1,2),
 \]
 and
 \[
 \psi(k_i) \sim A k^{-4},
 \]
 respectively, with B ∼ 10−4 and A ∼ 0.3 × 10−4 for and k = |k| is expressed in cycles/metre.The present findings do not support the wavenumber dependence predicted by the recent models in this wavenumber range and are at variance with their predicted dependence on the friction velocity. However, our observations are generally consistent with the radar reflectivity dependence on wind direction and wind speed under Bragg scattering conditions within our wavenumber range. The experimental observations also point out the potentially important role of wave-breaking of longer wave components in influencing the spectral levels of short gravity wave components.

Wavenumber spectra of short gravity waves

Distribution of the wind stress over the oceans is usually estimated by using a bulk formula. It contains the squared 10-m wind speed multiplied by the drag coefficient, which has been assumed in many cases to be a weak function of the 10-m wind speed. Over land the important role of thermal stratification has been clearly recognized, but over the sea the influence of wind waves is less well documented. This paper presents evidence showing the likelihood that the influence of the wind waves can also be large. Charnock proposed an expression for the marine atmospheric boundary layer roughness parameter, z0, which depended only on the wind friction velocity, u☆ and the acceleration of gravity, g. Toba and Koga have recently proposed an alternative expression for flow over growing wind waves, which are in local equilibrium with the wind, given by a form including the wind-wave spectral peak frequency explicity. The criterion for local equilibrium of the wave field with the wind is its consistency wi...

Wave Dependence of Sea-Surface Wind Stress

Preface 1. Overview Part I: 2. Historical drag expression 3. Atmospheric and oceanic boundary layer physics 4. Ocean wave spectra and integral properties 5. Drag generation mechanisms 6. Coupling mechanisms 7. The measurement of surface stress Part II: 8. The influence of swell on the drag 9. The influence of unsteadiness 10. The dependence on wave age 11. The influence on mesoscale atmospheric processes 12. Wind, stress and wave directions 13. The influence of surface tension 14. The influence of spatial inhomogeneity 15. Basin boundaries References Index.

/pdf/wind-stress-over-the-ocean-2bi2mb29uo.pdf

Wind Stress over the Ocean

Multispectral information from the ocean color sensors of remote sensing satellites can be used to classify the ocean surface waters into a number of classes. Nine areas distributed over the Pacific Ocean have been used to demonstrate this approach. Unsupervised neural networks were used to separate water pixels from land and cloud pixels and classify water into a variety of ocean colors. Self-organizing feature maps chose radiance spectra by minimizing least square differences amongst multichannel pixels. Pixels with similar radiance spectra were coded with similar colors. It has been shown that radiance spectra, after correction for the atmospheric absorption of a "standard atmosphere" for varying Sun and satellite viewing angles, could be classified into a single set of radiance spectra that apply over the whole ocean. No ground truth data were required to make this classification. Examinations of the classified images showed that the method could extract a large number of ocean color categories and provide a basis to separate case 1 waters from the case 2 and ocean radiances with a high influence of the atmosphere. Also, areas of high pigment, inappropriately masked out by the conventional routine, were correctly classified. This opens the possibility that in the future a robust global algorithm for chlorophyll estimation might be constructed.

Radiance spectra classification from the Ocean Color and Temperature Scanner on ADEOS

Turbulent velocity fluctuations in the upper portions of the wind-driven mixed layer of oceans or lakes appear to have a velocity scale proportional to the friction velocity and a length scale proportional to the distance below the free surface, as is usual in shear flows near a boundary. A number of one-dimensional velocity spectra have been measured in aquatic mixed layers, and these spectra, when they are scaled with the surface stress and the distance from the free surface, have been compared with turbulent boundary layer measurements. The good agreement suggests that the surface wave orbital velocities act merely as ‘inactive’ motions and do not interfere with the lower-frequency stress-carrying eddies.

Ian S. F. Jones

Papers

Wavenumber spectra of short gravity waves

Wave Dependence of Sea-Surface Wind Stress

Wind Stress over the Ocean

Radiance spectra classification from the Ocean Color and Temperature Scanner on ADEOS

The scaling of velocity fluctuations in the surface mixed layer