Observation of internal wave polarity conversion generated by a rising tide

Li, Lan; Wang, Caixia; Grimshaw, Roger

doi:10.1002/2015gl063870

Cited by 16 publications

(13 citation statements)

References 21 publications

(54 reference statements)

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“…where c is the phase speed of linear long waves, U(z) is the background current in the wave propagation direction, and f(z) is the mode-1 eigenfunction (e.g., Shroyer et al 2009;Li et al 2015;Grimshaw et al 2016). Our discussion will be limited to the case where c is everywhere greater than U.…”

Section: Theoretical Considerations a Weakly Nonlinear Theorymentioning

confidence: 99%

“…The end result of an initial ISW of depression passing through a critical point is the transformation of the wave into a mix of waves of elevation and depression, a process which starts well before the critical point is reached unless the bathymetry is very steep. On the shallow side of the critical point ISWs of elevation often emerge, a process that is sometimes referred to as polarity conversion or polarity reversal (Aghsaee et al 2010;Grimshaw et al 2010;Li et al 2015;Liu et al 1998;Orr and Mignerey 2003;Shroyer et al 2009;Zhao et al 2003Zhao et al , 2004. The formation of ISWs of elevation has been observed from variations of isothermal and isopycnal as well as acoustic backscatter (Fu et al 2012;Orr and Mignerey 2003;Ramp et al 2004;Shroyer et al 2009; X. , and in numerical simulations (Grimshaw et al 2004;Lamb and Xiao 2014;Liu et al 1998).…”

Section: Introductionmentioning

confidence: 97%

“…Moreover, our knowledge on the spatial-temporal variations of the critical point due to tides remains rather limited. Recent studies in Laoshan Bay (Li et al 2015;Grimshaw et al 2016) reporting tide-induced ISW polarity conversion are important exceptions. There, the observations were from a shallow site with a mean depth of 9 m, where the pycnocline depth relative to the total water depth is significantly modulated by tidal variations of the water depth.…”

Section: Introductionmentioning

confidence: 99%

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On Tidal Modulation of the Evolution of Internal Solitary-Like Waves Passing Through a Critical Point

Bai

Lamb

et al. 2021

Journal of Physical Oceanography

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Internal solitary-like waves (ISWs) evolve considerably when passing through a critical point separating the deep water where ISWs are waves of depression and shallower water where they are waves of elevation. The location of the critical point is determined by the background current and stratification. In this study, we investigate the influence of tidal currents on the cross-shelf movement of the critical point and elucidate the underlying processes via fully nonlinear numerical simulations. Our simulations reveal phase-locked tidal variations of the critical point, which are mainly attributed to stratification fluctuations that are modulated by the combined effects of cross-shelf barotropic tidal currents and locally generated baroclinic tides. The barotropic tidal currents drive isopycnal displacements as they flow over the slope, and as this occurs baroclinic tides are generated, modulating the stratification and inducing sheared currents. This results in a cross-shelf movement of the critical point, which moves onshore (offshore) when the pycnocline is elevated (depressed) by the flood (ebb) tide. Our idealized numerical simulations for the study region in the South China Sea suggest that the cross-shelf movement of the critical point reaches to O(10) km within a tidal cycle. This distance depends on the strength of tidal currents, stratification, and bathymetry. Because of tidal currents, ISWs of depression may undergo a complex evolution even in a stratification with a shallow pycnocline. For the stratification with a deep pycnocline, the critical point may be at a location deep enough so that its tidal movement becomes insignificant.

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Section: Theoretical Considerations a Weakly Nonlinear Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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On Tidal Modulation of the Evolution of Internal Solitary-Like Waves Passing Through a Critical Point

Bai

Lamb

et al. 2021

Journal of Physical Oceanography

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“…During the shoaling process, the internal wave of depression normally involves polarity change when it propagates from the deep-sea region to the coastal area [34][35][36]. This polarity conversion can be well-explained by the KdV theory which stated that the polarity changes for the wave solutions is based on the change of sign of coefficient in the quadratic nonlinear term, α [37][38].…”

Section: Transformation Of Internal Undular Bore Involves Polarity Chmentioning

confidence: 99%

Simulation of Internal Undular Bores of Depression Propagating over a Slowly Varying Region

Hooi¹,

Tiong²,

Tay³

et al. 2020

ARFMTS

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“…The appropriate model to describe the nonlinear internal waves in a fluid system with stratification is the extended Korteweg-de Vries (eKdV) equation [12], [13]. This model is extended from the well-known Korteweg-de Vries (KdV) equation, which is widely used to describe the nonlinear shallow water waves.…”

Section: Introductionmentioning

confidence: 99%

Simulation of Internal Undular Bores Propagating over a Slowly Varying Region

Hooi¹,

Tiong²,

Tay³

et al. 2019

Int. J. Adv. Sci. Eng. Inf. Technol.

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Internal undular bores have been observed in many parts of the world. Studies have shown that many marine structures face danger and risk of destruction caused by internal undular bores due to the amount of energy it carries. This paper looks at the transformation of internal undular bore in two-layer fluid flow under the influence of variable topography. Thus, the surface of the bottom is considered to be slowly varying. The appropriate mathematical model is the variable-coefficient extended Korteweg-de Vries equation. We are particularly interested in looking at the transformation of KdV-type and table-top undular bore over the variable topography region. The governing equation is solved numerically using the method of lines, where the spatial derivatives are first discretised using finite difference approximation so that the partial differential equation becomes a system of ordinary differential equations which is then solved by 4 th order Runge-Kutta method. Our numerical results show that the evolution of internal undular bore over different types of varying depths regions leads to a number of adiabatic and non-adiabatic effects. When the depth decreases slowly, a solitary wavetrain is observed at the front of the transformed internal undular bore. On the other hand, when the depth increases slowly, we observe the generation of step-like wave and weakly nonlinear trailing wavetrain, the occurrence of multi-phase behaviour, the generation of transformed undular bore of negative polarity and diminishing transformed undular bore depending on the nature of the topography after the variable topography.

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Observation of internal wave polarity conversion generated by a rising tide

Cited by 16 publications

References 21 publications

On Tidal Modulation of the Evolution of Internal Solitary-Like Waves Passing Through a Critical Point

On Tidal Modulation of the Evolution of Internal Solitary-Like Waves Passing Through a Critical Point

Simulation of Internal Undular Bores of Depression Propagating over a Slowly Varying Region

Simulation of Internal Undular Bores Propagating over a Slowly Varying Region

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