Internal Wave Induced Fluctuations in the Oceanic Density and Sound Speed Fields

1991 ◽  
pp. 103-118
Author(s):  
Robert Pinkel ◽  
Jeffrey T. Sherman
Keyword(s):  
Internal Wave ◽  
Sound Speed ◽  
Wave Induced

scholarly journals Abyssal plain hills and internal wave turbulence

2018 ◽  
Vol 15 (14) ◽  
pp. 4387-4403 ◽  
Author(s):  
Hans van Haren
Keyword(s):  
Internal Wave ◽  
Wave Breaking ◽  
Large Scale ◽  
Abyssal Plain ◽  
Marginal Stability ◽  
Eddy Diffusivities ◽  
North East ◽  
Mid Atlantic Ridge ◽  
Ocean Topography ◽  
Wave Induced

Abstract. A 400 m long array with 201 high-resolution NIOZ temperature sensors was deployed above a north-east equatorial Pacific hilly abyssal plain for 2.5 months. The sensors sampled at a rate of 1 Hz. The lowest sensor was at 7 m above the bottom (m a.b.). The aim was to study internal waves and turbulent overturning away from large-scale ocean topography. Topography consisted of moderately elevated hills (a few hundred metres), providing a mean bottom slope of one-third of that found at the Mid-Atlantic Ridge (on 2 km horizontal scales). In contrast with observations over large-scale topography like guyots, ridges and continental slopes, the present data showed a well-defined near-homogeneous “bottom boundary layer”. However, its thickness varied strongly with time between < 7 and 100 m a.b. with a mean around 65 m a.b. The average thickness exceeded tidal current bottom-frictional heights so that internal wave breaking dominated over bottom friction. Near-bottom fronts also varied in time (and thus space). Occasional coupling was observed between the interior internal wave breaking and the near-bottom overturning, with varying up- and down- phase propagation. In contrast with currents that were dominated by the semidiurnal tide, 200 m shear was dominant at (sub-)inertial frequencies. The shear was so large that it provided a background of marginal stability for the straining high-frequency internal wave field in the interior. Daily averaged turbulence dissipation rate estimates were between 10−10 and 10−9 m2 s−3, increasing with depth, while eddy diffusivities were of the order of 10−4 m2 s−1. This most intense “near-bottom” internal-wave-induced turbulence will affect the resuspension of sediments.

Influence of mean sound speed on acoustic transmission through an internal wave

1976 ◽  
Vol 59 (3) ◽  
pp. 536-544
Author(s):  
G. A. Lieberman ◽  
M. J. Jacobson ◽  
W. L. Siegmann
Keyword(s):  
Internal Wave ◽  
Sound Speed ◽  
Acoustic Transmission

The effects of near-bottom stratification on internal wave induced instabilities in the boundary layer

2017 ◽  
Vol 29 (1) ◽  
pp. 016602 ◽  
Author(s):  
Sandhya Harnanan ◽  
Marek Stastna ◽  
Nancy Soontiens
Keyword(s):  
Boundary Layer ◽  
Internal Wave ◽  
Wave Induced

scholarly journals Unpredictability of internal M<sub>2</sub>

2007 ◽  
Vol 4 (2) ◽  
pp. 303-323
Author(s):  
H. van Haren
Keyword(s):  
Internal Wave ◽  
Tidal Energy ◽  
Short Wave ◽  
Small Scale ◽  
Tidal Waves ◽  
North East ◽  
Background Density ◽  
Continental Slopes ◽  
Shelf Sea ◽  
Wave Induced

Abstract. Current observations from a shelf sea, continental slopes and the abyssal North-East Atlantic Ocean are all dominated by the semidiurnal lunar (M2) tide. It is shown that motions at M2 vary at usually large barotropic and coherent baroclinic scales, >50 km horizontally and >0.5 H vertically. H represents the waterdepth. Such M2-scales are observed even close to topography, the potential source of baroclinic, "internal" tidal waves. In contrast, incoherent small-scale, ~10 km horizontally and ~0.1 H vertically, baroclinic motions are dominated around f, the local inertial frequency, and/or near 2Ω≈S2, the semidiurnal solar tidal frequency. Ω represents the Earth's rotational vector. This confirms earlier suggestions that small-scale baroclinic M2-motions generally do not exist in the ocean in any predictable manner, except in beams very near (<10 km horizontally) to their source. As a result, M2-motions are not directly important for generating shear and internal wave induced mixing in the ocean. Indirectly however, they may contribute to ocean mixing if transfer to small-scale motions at f and/or S2 can be proven. Also far from topography, small-scale motions are found at either or both of the latter frequencies. Different suggestions for the scales at these particular frequencies are discussed, ranging from the variability of "background" density gradients and associated divergence and focusing of internal wave rays to the removal of the internal tidal energy by non-linear interactions. It is noted that near f and S2 the short-wave inertio-gravity wave bounds are found in the limit of very weak stratification, which are often observed in small-scale near-homogeneous layers.

scholarly journals Seismic imaging of a thermohaline staircase in the western tropical North Atlantic

2010 ◽  
Vol 7 (1) ◽  
pp. 361-389
Author(s):  
I. Fer ◽  
P. Nandi ◽  
W. S. Holbrook ◽  
R. W. Schmitt ◽  
P. Páramo
Keyword(s):  
Internal Wave ◽  
North Atlantic ◽  
Vertical Mixing ◽  
Global Ocean ◽  
Turbulent Dissipation ◽  
Tropical North Atlantic ◽  
Seismic Reflection Method ◽  
Order Of Magnitude ◽  
Salt Fingering ◽  
Wave Induced

Abstract. Multichannel seismic data acquired in the Lesser Antilles in the western tropical North Atlantic indicate that the seismic reflection method has imaged an oceanic thermohaline staircase. Synthetic modeling of observed density and sound speed profiles corroborates inferences from the seismic imagery. Laterally coherent, uniform layers are present at depths ranging from 550–700 m and have a separation of ~20 m, with thicknesses increasing with depth. Reflection coefficient, a measure of the acoustic impedance contrasts, associated with the interfaces is one order of magnitude greater than the background levels. Hydrography sampled in previous surveys puts a constraint on the longevity of these layers in this area to within a maximum of three years. Spectral analysis of layer horizons in the thermohaline staircase indicates that internal wave activity is anomalously low, suggesting weak internal wave-induced turbulence and mixing. Results from two independent measurements, the application of a finescale parameterization to observed high-resolution velocity profiles and direct measurements of turbulent dissipation rate, confirm the low levels of turbulence and mixing. The lack of internal wave-induced mixing allows for the maintenance of the staircase. Our observations show the potential that seismic oceanography can contribute to an improved understanding of temporal occurrence rates, and the geographical distribution of thermohaline staircases and can improve current estimates of vertical mixing rates ascribable to salt fingering in the global ocean.

A novel method for internal wave monitoring based on expansion of the sound speed profile

2019 ◽  
Vol 38 (4) ◽  
pp. 183-189 ◽  
Author(s):  
Ke Qu ◽  
Fengqin Zhu ◽  
Wenhua Song
Keyword(s):  
Internal Wave ◽  
Sound Speed ◽  
Speed Profile ◽  
Sound Speed Profile ◽  
Novel Method
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