Abstract Upper-ocean velocity and shear data were obtained from Doppler sonars operated at the Surface Heat Budget of the Arctic Ocean (SHEBA) ice camp during the camp’s year-long drift across the western Arctic Ocean. These are used to estimate wavenumber–frequency spectra of shear E(κz, σ) during three selected time intervals. The Arctic shear spectra are similar in form to typical oceanic spectra, except that they have roughly an order-of-magnitude less variance. The slope of the frequency dependence is also steeper (σ−3–σ−4 for σ < −f, where f is the Coriolis frequency) in the internal-wave band, and the vertical wavenumber dependence is centered at higher wavenumber. Given the small vertical scales and low velocities of Arctic signals, a careful assessment of sonar precision is performed. Fluctuations at vertical scales > 10 m and time scales > 1 h are deemed significant. At subinertial frequencies, a vortical (quasigeostrophic) contribution to the shear spectrum is seen. The vertical wavenumber dependence of the shear spectrum in this frequency range is distinctly red, in contrast to the band-limited form of the superinertial spectrum; that is, E(κz, σ) ∼ κ−1z for |σ| < f. A fundamental characteristic of both the internal-wave and vortical spectral contributions is that the observed frequency bandwidth increases linearly with increasing vertical wavenumber magnitude. This is interpreted as the signature of the Doppler shifting of the observations by random “background” currents and by ice motion and is responsible for the distinctly “nonseparable” nature of the shear spectrum. As a consequence, the vertical wavenumber spectrum of the subinertial motion field is white: Evort(κz) = ∫Evort(κz, σ) dσ ∼ κ0z.

apply to any sort of wave motion such as acoustic dispersion in the case of sound and seismic waves, in gravity waves (ocean waves), and for telecommunication This glossary of engineering terms is a list of definitions about the major concepts of engineering. Please see the bottom of the page for glossaries of specific fields of engineering. ν ( x ) = ∫ θ ( x ) d … In mathematics, the gravitational potential is also known as the Newtonian potential and is fundamental in the study of potential theory. It may also be used for solving the electrostatic and magnetostatic fields generated by uniformly charged or polarized ellipsoidal bodies. Gravitational waveGravitational waves are disturbances in the curvature of spacetime, generated by accelerated masses, that propagate as waves outward from their source at the speed of light. They were proposed by Henri Poincaré in 1905 and subsequently predicted in 1916 by Albert Einstein on the basis of his general theory of relativity. Gravitational waves transport energy as gravitational radiation, a form of radiant energy similar to electromagnetic radiation. Newton's law of universal gravitation, part of classical mechanics, does not provide for their existence, since that law is predicated on the assumption that physical interactions propagate instantaneously (at infinite speed) – showing one of the ways the methods of classical physics are unable to explain phenomena associated with relativity. GravityOr gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light—are brought toward (or gravitate toward) one another. On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the ocean tides. The gravitational attraction of the original gaseous matter present in the Universe caused it to begin coalescing and forming stars and caused the stars to group together into galaxies, so gravity is responsible for many of the large-scale structures in the Universe. Gravity has an infinite range, although its effects become increasingly weaker as objects get further away. Ground stateThe ground state of a quantum-mechanical system is its lowest-energy state; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state. In quantum field theory, the ground state is usually called the vacuum state or the vacuum.

A space‐time spectral analysis is applied to the 900‐mbar meridional wind component over the equatorial Pacific Ocean. Cloud drift vectors, in the form of movie loops derived manually from cloud‐tracking satellites, constitute the data base for this investigation. The major conclusions are as follows: (1) The maximum energy density levels of the wind occur at low wave numbers over a broad range of frequencies. These disturbances appear to manifest themselves as fluctuations occurring simultaneously over a large span of longitude. (2) Investigation of the high frequency‐high wave number structure is difficult because of the general shortage of reliable data and the uneven satellite sampling intervals. Selection of spectral parameters becomes a compromise between the problems of high aliasing and low reliability. A high frequency‐low wave number (time lag of 5 hours and space separation of 2.1° longitude) study was selected. (3) There was no indication of a distinct 4‐day signal in our spectra. (4) There appears to be less high‐frequency energy in the equatorial band (1.05°S to 1.05°N) than in the other two more southerly bands (5.25°S to 3.15°S and 3.15°S to 1.05°S).

There has been a significant increase of studies on wave-ice interactions in the past decades. Through a close look at a representative set of theories, this paper investigates different physical processes that have produced different wave dispersion and attenuation. The existing theories have considered four major processes: scattering, flexural damping, viscoelastic damping and basal friction. Each theory looked into one of these processes and used a different mathematical formulation to model these processes. The low-frequency behaviours of the resulting spectral attenuation in these theories are fundamentally different from each other. Recent field observations have produced a large amount of data to calibrate and validate these theories. The uncertainties in using field measurements to determine attenuation due to ice covers are discussed. Both observational data and applications of these theories in field conditions suggest a multi-physics approach. A number of studies to further the theoretical development are recommended. It will take time for wave-in-ice models to reach the same level of performance as wave models for the open ocean, relying on the combined effort of theoretical, modelling and observational studies. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'.