Soliton generation by internal tidal beams impinging on a pycnocline: laboratory experiments

Mercier, Matthieu; Mathur, Manikandan; Gostiaux, Louis; Gerkema, Theo; Magalhaes, J.M.; Silva, José C. B. da; Dauxois, Thierry

doi:10.1017/jfm.2012.191

Cited by 49 publications

(51 citation statements)

References 27 publications

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“…Osborne and Burch, 1980;Alpers and Salusti, 1983;Apel et al, 1985;New and da Silva, 2002;Sherwin et al, 2002;Ramp et al, 2004;Grisouard et al, 2011;Guo et al, 2012;Jackson et al, 2012;Mercier et al, 2012;Kozlov et al, 2014). Both new and unidentified IW hotspots, as well as previously studied regions, have benefited from satellite views, frequently providing new and deeper insights into their generation, propagation and dissipation mechanisms (e.g.…”

Section: Introductionmentioning

confidence: 99%

Effect of the North Equatorial Counter Current on the generation and propagation of internal solitary waves off the Amazon shelf (SAR observations)

et al. 2016

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Abstract. Synthetic aperture radar (SAR) imagery from the Amazon shelf break region in the tropical west Atlantic reveals for the first time the two-dimensional horizontal structure of an intense Internal Solitary Wave (ISW) field, whose first surface manifestations are detected several hundred kilometres away from the nearest forcing bathymetry. Composite maps and an energy budget analysis (provided from the Hybrid Coordinate Ocean Model -HYCOM) help to identify two major ISW pathways emanating from the steep slopes of a small promontory (or headland) near 44 • W and 0 • N, which are seen to extend for over 500 km into the open ocean. Further analysis in the SAR reveals propagation speeds above 3 m s −1 , which are amongst the fastest ever recorded. The main characteristics of the ISWs are further discussed based on a statistical analysis, and seasonal variability is found for one of the ISW sources. This seasonal variability is discussed in light of the North Equatorial Counter Current. The remote appearance of the ISW sea surface manifestations is explained by a late disintegration of the internal tide (IT), which is further investigated based on the SAR data and climatological monthly means (for stratification and currents). Acknowledging the possibility of a late disintegration of the IT may help explain the remote-sensing views of other ISWs in the world's oceans.

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Section: Introductionmentioning

confidence: 99%

Effect of the North Equatorial Counter Current on the generation and propagation of internal solitary waves off the Amazon shelf (SAR observations)

et al. 2016

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“…Some recent laboratory experiments have focused on such waves in a two layer flow, but they lack instantaneous 3D interface elevation measurements, the interface height being retrieved either from local probes [17,20] or from a vertical plane intersecting the interface [18]. In the present study, an optical stereoscopic technique is deployed to measure an instantaneous field of the elevation of an interface located between two layer of fluid.…”

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confidence: 99%

Wave patterns generated by an axisymmetric obstacle in a two-layer flow

et al. 2013

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“…The constant of proportionality is a function of the parameter γ , which gives the dimensionless strength of the pycnocline in terms of the incident wave number and the underlying buoyancy frequency. A similar parameter was proposed to govern the coupling between incident internal waves and interfacial waves in Akylas et al (2007) and Mercier et al (2012). The amplitude B 2 is infinite (a singularity) at γ = 2 (1+α) sin 2 θ, where the denominator of Eq.…”

Section: Weakly Nonlinear Internal Wave Refractionmentioning

confidence: 85%

“…Recently, the nonlinear generation of harmonic modes by an internal wave beam incident on a pycnocline was demonstrated experimentally (Mercier et al, 2012;Wunsch and Brandt, 2012). Both experiments reported a series of harmonic modes, while Wunsch and Brandt also confirmed the approximate doubling of the incident wave number predicted by Thorpe (1998).…”

Section: Introductionmentioning

confidence: 85%

“…The harmonics were unable to propagate into the lower stratified layer and were therefore trapped within the pycnocline. The exception is a single experiment reported by Mercier et al (2012) showing a radiated harmonic wave for an incidence angle of 15 degrees. Recent numerical simulations (Diamessis et al, 2014) with thicker pycnoclines also suggested that the harmonics formed due to nonlinear refraction through the rapidly increasing stratification at the pycnocline base, rather than due to overlap of incident and reflecting beams at the top of the pycnocline.…”

Section: Introductionmentioning

confidence: 99%

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Simulations of nonlinear harmonic generation by an internal wave beam incident on a pycnocline

Wunsch

Delwiche

et al. 2014

Nonlin. Processes Geophys.

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Abstract. Internal wave beams generated by oceanic tidal flows propagate upward and interact with the increasing stratification found at the pycnocline. The nonlinear generation of harmonic modes by internal wave beams incident on a pycnocline has recently been demonstrated by laboratory experiments and numerical simulations. In these previous studies, the harmonic modes were trapped within the pycnocline because their frequencies exceeded that of the stratified fluid below. Here, two-dimensional numerical simulations are used to explore the effect of incidence angle on harmonic generation at a thin pycnocline. At incidence angles less than 30 degrees (typical of oceanic beams), the lowest harmonic mode freely radiates in the form of an internal wave beam rather than being trapped within the pycnocline. The results indicate that nonlinear refraction is the primary mechanism for harmonic generation at incidence angles exceeding 30 degrees, but that interaction of the incident and reflected beams is more important at smaller incidence angles. The simulations are compared to weakly nonlinear theory based on refraction at the pycnocline. The results yield good agreement for trapped harmonics, but weakly nonlinear theory substantially underpredicts the amplitude of the radiated harmonics.

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Soliton generation by internal tidal beams impinging on a pycnocline: laboratory experiments

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Cited by 49 publications

References 27 publications

Effect of the North Equatorial Counter Current on the generation and propagation of internal solitary waves off the Amazon shelf (SAR observations)

Effect of the North Equatorial Counter Current on the generation and propagation of internal solitary waves off the Amazon shelf (SAR observations)

Wave patterns generated by an axisymmetric obstacle in a two-layer flow

Simulations of nonlinear harmonic generation by an internal wave beam incident on a pycnocline

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