Generation of internal solitary waves by frontally forced intrusions in geophysical flows

Bourgault, D.; Galbraith, Peter S.; Chavanne, Cédric

doi:10.1038/ncomms13606

Cited by 36 publications

(30 citation statements)

References 54 publications

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“…Instead their generation may be related to the Fraser River plume. Internal waves generated from intrusion of gravity currents have been reported in some field observations (Bourgault et al, 2016;Nash & Moum, 2005). By analogy to flow over topography (Baines, 1984), White and Helfrich (2012) described the intrusion of gravity current front into a two-layer stratified fluid under different regimes using numerical modeling.…”

Section: Relationships To Tidal Phase and Generation Mechanismsmentioning

confidence: 99%

Seasonal Variability and Generation Mechanisms of Nonlinear Internal Waves in the Strait of Georgia

Pawlowicz

Wang

2018

JGR Oceans

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Seasonal variability and generation mechanisms of large nonlinear internal waves are reported, based on an analysis of 9 years of continuous observational data collected at nodes of the Ocean Networks Canada coastal observatory in the Strait of Georgia, Canada. About one thousand large nonlinear internal wave packets were identified. The timing of these packets suggests a very strong correlation with daily tides and fortnightly cycles. More waves are seen during the stronger tides of the fortnightly cycle but overall waves are seen in less than 40% of all days. Other wave characteristics show seasonal variations. In winter, when the pycnocline is weaker, both the spatial and temporal scales of internal waves are several times larger than summertime waves and wave amplitudes can approach 30 m. These waves are large enough vertically but small enough horizontally that standard acoustic Doppler current profiler (ADCP) processing algorithms present a strongly distorted view of wave shape and features. A specialized reprocessing of the beam velocities is used to correctly measure the wave velocity field and to determine wave propagation speed and direction. In addition to the previously known northward‐propagating waves in the Strait, we also found waves propagating in other directions and a noticeable correlation with winds, which may be a proxy for spatial variations in density and/or velocity shear. By considering wave propagation direction, relationship with tidal phase, and relationship with wind, three generation mechanisms were found. Two particularly interesting generation mechanisms involve waves radiating from the Sand Heads area.

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Section: Relationships To Tidal Phase and Generation Mechanismsmentioning

confidence: 99%

Seasonal Variability and Generation Mechanisms of Nonlinear Internal Waves in the Strait of Georgia

Pawlowicz

Wang

2018

JGR Oceans

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“…Internal solitary waves (ISWs) continue to attract burgeoning interest, not least because of their pervasiveness in many marine and freshwater environments (Horn et al 2001;Nash & Moum 2005;Helfrich & Melville 2006;Groeskamp et al 2011;Lamb 2014;Bourgault et al 2016;Boegman & Stastna 2019). They propagate on density interfaces in stably-stratified fluid systems and may be characterised generally as nonlinear, dispersive waves of quasi-permanent form with an amplitude comparable with the thickness of the interface on which they travel and also, in many cases of interest, the overall depth of the fluid system in question (see e.g.…”

Section: Introductionmentioning

confidence: 99%

Shoaling mode-2 internal solitary-like waves

et al. 2019

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The propagation of a train of mode-2 internal solitary-like waves (ISWs) over a uniformly sloping, solid topographic boundary, has been studied by means of a combined laboratory and numerical investigation. The waves are generated by a lock-release method. Features of their shoaling include (i) formation of an oscillatory tail, (ii) degeneration of the wave form, (iii) wave run up, (iv) boundary layer separation, (v) vortex formation and re-suspension at the bed and (vi) a reflected wave signal. Slope steepness, $s$, is defined to be the height of the slope divided by the slope base length. In shallow slope cases ($s\leqslant 0.07$), the wave form is destroyed by the shoaling process; the leading mode-2 ISW degenerates into a train of mode-1 waves of elevation and little boundary layer activity is seen. For steeper slopes ($s\geqslant 0.13$), boundary layer separation, vortex formation and re-suspension at the bed are observed. The boundary layer dynamics is shown (numerically) to be dependent on the Reynolds number of the flow. A reflected mode-2 wave signal and wave run up are seen for slopes of steepness $s\geqslant 0.20$. The wave run up distance is shown to be proportional to the length scale $ac^{2}/g^{\prime }h_{2}\sin \unicode[STIX]{x1D703}$ where $a,c,g^{\prime },h_{2}$ and $\unicode[STIX]{x1D703}$ are wave amplitude, wave speed, reduced gravity, pycnocline thickness and slope angle respectively.

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“…In the atmosphere, fronts such as thunderstorm outflows are known to excite undular bores (e.g., the Morning Glory in northern Australia) which steepen to produce large‐amplitude internal solitary waves (ISWs) [ Clarke et al ., ; Doviak et al ., ]. In the ocean, the ISWs have been shown to be generated by the spreading of a river plume over the continental shelf [ Nash and Moum , ; Orton and Jay , ; Pan et al ., ; Pan and Jay , ] and by the intrusion of an interfacial gravity current in a fjord [ Bourgault et al ., ].…”

Section: Introductionmentioning

confidence: 99%

“…In the atmosphere, fronts such as thunderstorm outflows are known to excite undular bores (e.g., the Morning Glory in northern Australia) which steepen to produce large-amplitude internal solitary waves (ISWs) [Clarke et al, 1981;Doviak et al, 1991]. In the ocean, the ISWs have been shown to be generated by the spreading of a river plume over the continental shelf [Nash and Moum, 2005;Orton and Jay, 2005;Pan et al, 2007;Pan and Jay, 2009] and by the intrusion of an interfacial gravity current in a fjord [Bourgault et al, 2016]. Rottman and Simpson [1989] conducted laboratory experiments and found that gravity currents moving into a two-layer fluid can generate upstream propagating internal bores or waves under certain conditions.…”

Section: Introductionmentioning

confidence: 99%

Breaking of internal solitary waves generated by an estuarine gravity current

Xie

Boicourt

2017

Geophysical Research Letters

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Mooring and ship‐based data collected in a stratified estuary showed the generation of internal solitary waves by a bottom gravity current. Down‐estuary winds drove a counterclockwise lateral circulation over channel‐shoal bathymetry. When the lateral flows became supercritical, the pycnocline was sharply raised at the edge of the deep channel, leading to flow convergences and formation of a bottom gravity current. As the lateral circulation weakened during wind relaxation, the gravity current propagated onto the shoal and excited internal disturbances around its head. These disturbances evolved into a train of large‐amplitude internal solitary waves that subsequently propagated ahead of the gravity current. The waves moving out of the gravity current broke, generating overturning and turbulence with energy dissipation rate reaching ~1 × 10−4 m2 s−3, 3 orders of magnitude larger than the background value. Our observations suggest that breaking internal waves may be an important source of turbulent mixing in stratified estuaries.

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Generation of internal solitary waves by frontally forced intrusions in geophysical flows

Cited by 36 publications

References 54 publications

Seasonal Variability and Generation Mechanisms of Nonlinear Internal Waves in the Strait of Georgia

Seasonal Variability and Generation Mechanisms of Nonlinear Internal Waves in the Strait of Georgia

Shoaling mode-2 internal solitary-like waves

Breaking of internal solitary waves generated by an estuarine gravity current

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