Energy Release Through Internal Wave Breaking

Haren, Hans van; Gostiaux, Louis

doi:10.5670/oceanog.2012.47

Cited by 31 publications

(18 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We generate waves with amplitudes up to 3.5 times the shallow layer depth, well beyond the KdV regime. So that the results can be readily applied to interpret ocean observations, we classify the wave breaking regimes in terms of incident solitary wave characteristics that can be measured by surface observations and vertical time series constructed, for example, from traversing conductivity‐temperature‐depth (CTD) probes or moored thermistor chains [e.g., van Haren and Gostiaux , ]. Our analyses focus on predicting the maximum breaking depth and the consequent upslope propagation of the lower layer as a bolus.…”

Section: Introductionmentioning

confidence: 99%

Shoaling internal solitary waves

2013

View full text Add to dashboard Cite

[1] The evolution and breaking of internal solitary waves in a shallow upper layer as they approach a constant bottom slope is examined through laboratory experiments. The waves are launched in a two-layer fluid through the standard lock-release method. In most experiments, the wave amplitude is significantly larger than the depth of the shallow upper layer so that they are not well described by Korteweg-de Vries theory. The dynamics of the shoaling waves are characterized by the Iribarren number, Ir, which measures the ratio of the topographic slope to the square root of the characteristic wave slope. This is used to classify breaking regimes as collapsing, plunging, surging, and nonbreaking for increasing values of Ir. For breaking waves, the maximum interface descent, H i ? , is predicted to depend upon the topographic slope, s, and the incident wave's amplitude and width, A sw and L sw , respectively, asThis prediction is corroborated by our experiments. Likewise, we apply simple heuristics to estimate the speed of interface descent, and we characterize the speed and range of the consequent upslope flow of the lower layer after breaking has occurred.

show abstract

Section: Introductionmentioning

confidence: 99%

Shoaling internal solitary waves

2013

View full text Add to dashboard Cite

show abstract

“…During most tidal periods, the "background" dissipation rate rises prior to the start of the downslope phase (see also data from a different area in Ref. 30; not resolved ∼100 m high tidal wave).…”

Section: Observationsmentioning

confidence: 99%

Stratified turbulence and small-scale internal waves above deep-ocean topography

Haren

2013

Physics of Fluids

Self Cite

View full text Add to dashboard Cite

When ocean's internal tidal waves "beach" at underwater topography, they transform from more or less linear into highly nonlinear waves that can break with generation of vigorous turbulent mixing. Although most mixing occurs in the half hour around a steep (bottom-)front leading the upslope moving internal tide phase, relatively large mixing also occurs some distance of several tens of meters off the bottom, just prior to the downslope moving internal tide phase and initiated by highfrequency "small-scale" internal waves. Details of this off-bottom small-scale mixing in a stratified natural environment and some of its variability per tidal period are presented here in two case studies using high-resolution temperature observations (61 sensors at 1 m intervals; <10 −3 • C precision) at a 969 m deep site south of New Zealand. The observations shed some light on stratified turbulence that is generated in a relatively thick (∼30 m) weakly stratified layer and in the strongly stratified interfaces above and below. The interfacial internal waves generate turbulence with largest dissipation rate and temperature variance at the edge of the upper interface and the weakly stratified layer. When these waves steep nonlinearly, immediate moderate turbulence generation is observed below, throughout the weakly stratified layer. Largest turbulence is generated by 25 m high asymmetric Holmboe overturns. C 2013 AIP Publishing LLC. [http://dx

show abstract

“…The 3 min bore passage comprises about 20 % of the total dissipation rate in a tidal period (van Haren & Gostiaux 2012b). However, turbulence is generated not only by shear stress at the bottom, but also by convection in the interior.…”

Section: Discussionmentioning

confidence: 99%

“…However, turbulence is generated not only by shear stress at the bottom, but also by convection in the interior. The total amount of turbulence kinetic energy dissipated in the lower 50 m above the sloping bottom amounts to about a quarter of the total internal tidal energy conversion by Great Meteor Seamount (van Haren & Gostiaux 2012b). It remains to be established whether this is mainly due to (breaking) internal waves returning to their source.…”

Section: Discussionmentioning

confidence: 99%

Bottom-pressure observations of deep-sea internal hydrostatic and non-hydrostatic motions

Haren

2013

J. Fluid Mech.

Self Cite

View full text Add to dashboard Cite

In the ocean, sloping bottom topography is important for the generation and dissipation of internal waves. Here, the transition of such waves to turbulence is demonstrated using an accurate bottom-pressure sensor that was moored with an acoustic Doppler current profiler and high-resolution thermistor string on the sloping side of the ocean guyot 'Great Meteor Seamount' (water depth 549 m). The site is dominated by the passage of strong frontal bores, moving upslope once or twice every tidal period, with a trail of high-frequency internal waves. The bore amplitude and precise timing of bore passage vary every tide. A bore induces mainly non-hydrostatic pressure, while the trailing waves induce mainly internal hydrostatic pressure. These separate (internal wave) pressure terms are independently estimated using current and temperature data, respectively. In the bottom-pressure time series, the passage of a bore is barely visible, but the trailing high-frequency internal waves are. A bore is obscured by higher-frequency pressure variations up to ∼ 4 × 10 3 cpd ≈ 80N (cpd, cycles per day; N, the large-scale buoyancy frequency). These motions dominate the turbulent state of internal tides above a sloping bottom. In contrast with previous bottom-pressure observations in other areas, infra-gravity surface waves contribute little to these pressure variations in the same frequency range. Here, such waves do not incur observed pressure. This is verified in a consistency test for large-Reynoldsnumber turbulence using high-resolution temperature data. The high-frequency quasiturbulent internal motions are visible in detailed temperature and acoustic echo images, revealing a nearly permanently wave-turbulent tide going up and down the bottom slope. Over the entire observational period, the spectral slope and variance of bottom pressure are equivalent to internal hydrostatic pressure due to internal waves in the lower 100 m above the bottom, by non-hydrostatic pressure due to high-frequency internal waves and large-scale overturning. The observations suggest a transition between large-scale internal waves, small-scale internal tidal waves residing on thin (∼1 m) stratified layers and turbulence.

show abstract

Energy Release Through Internal Wave Breaking

Cited by 31 publications

References 22 publications

Shoaling internal solitary waves

Shoaling internal solitary waves

Stratified turbulence and small-scale internal waves above deep-ocean topography

Bottom-pressure observations of deep-sea internal hydrostatic and non-hydrostatic motions

Contact Info

Product

Resources

About