The Boussinesq approximation provides a convenient framework to describe the dynamics of stably-stratified fluids. A fundamental motion in these fluids consists of internal gravity waves, whatever the strength of the stratification. These waves may be unstable through parametric instability, which results in turbulence and mixing. After a brief review of the main properties of internal gravity waves, we show how the parametric instability of a monochromatic internal gravity wave organizes itself in space and time, using energetics arguments and a simple kinematic model. We provide an example, in the deep ocean, where such instability is likely to occur, as estimates of mixing from in situ measurements suggest. We eventually discuss the fundamental role of internal gravity wave mixing in the maintenance of the abyssal thermal stratification.
L'approximation de Boussinesq constitue un cadre bien adapté à l'étude des fluides stablement stratifiés. Des ondes de gravité internes s'y développent, quel que soit le niveau de stratification, qui peuvent être instables par instabilité paramétrique. Turbulence et mélange en résultent. Après un bref rappel sur les propriétés des ondes de gravité internes, nous montrons comment s'organisent les transferts d'énergie, dans l'espace et dans le temps, lorsqu'une onde interne est paramétriquement instable. Un modèle cinématique simple est employé pour cela. Puis nous illustrons ce processus et ses conséquences par un exemple océanique : l'instabilité paramétique se produit très certainement dans l'océan profond, comme le suggèrent les mesures in situ. Nous discutons finalement du rôle fondamental des ondes de gravité internes dans l'entretien de la stratification abyssale, par le mélange qu'elles induisent.
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Mot clés : Mécanique des fluides, Fluide stratifié, Ondes de gravité internes, Mélange océanique
Chantal Staquet 1
@article{CRMECA_2007__335_9-10_665_0, author = {Chantal Staquet}, title = {Internal gravity waves: parametric instability and deep ocean mixing}, journal = {Comptes Rendus. M\'ecanique}, pages = {665--678}, publisher = {Elsevier}, volume = {335}, number = {9-10}, year = {2007}, doi = {10.1016/j.crme.2007.08.009}, language = {en}, }
Chantal Staquet. Internal gravity waves: parametric instability and deep ocean mixing. Comptes Rendus. Mécanique, Volume 335 (2007) no. 9-10, pp. 665-678. doi : 10.1016/j.crme.2007.08.009. https://comptes-rendus.academie-sciences.fr/mecanique/articles/10.1016/j.crme.2007.08.009/
[1] Waves in Fluids, Cambridge University Press, 1978
[2] Atmosphere–Ocean Dynamics, Academic Press, 1987
[3] E. Danioux, P. Klein, P. Rivière, Propagation of wind energy into the deep ocean through mesoscale eddies, J. Phys. Oceanogr., submitted for publication
[4] Wave interactions—the evolution of an idea, J. Fluid Mech., Volume 106 (1981), pp. 215-227
[5] On the parametric instability of an internal gravity wave, Proc. R. Soc. Lond. A, Volume 356 (1977), p. 411
[6] The occurrence of parametric instabilities in finite-amplitude internal gravity waves, J. Fluid Mech., Volume 78 (1976), pp. 763-784
[7] Two and three-dimensional parametric instabilities in finite amplitude internal gravity waves, Geophys. Astrophys. Fluid Dynam., Volume 61 (2006), p. 1
[8] Mixing by breaking internal gravity waves: from instabilities to turbulence, Annu. Rev. Fluid Mech., Volume 34 (2002), pp. 559-593
[9] Vertical mixing, energy and the general circulation of the oceans, Annu. Rev. Fluid Mech., Volume 36 (2004), pp. 281-314
[10] Internal gravity waves in geophysical fluids, CISM Lecture Notes, vol. 479, Springer-Verlag, 2005, pp. 75-131
[11] A theoretical and experimental investigation of the phase configuration of internal waves of small amplitude in a density stratified liquid, J. Fluid Mech., Volume 28 (1967), pp. 1-16
[12] Excitation and breaking of internal gravity waves by parametric instability, J. Fluid Mech., Volume 374 (1998), pp. 117-144
[13] The effect of rotation on conical wave beams in a stratified fluid, Exp. Fluids, Volume 39 (2005), pp. 32-37
[14] A similarity solution for viscous internal waves, J. Fluid Mech., Volume 54 (1972), pp. 495-506
[15] The generation of internal waves by vibrating elliptic cylinders. Part 2. Approximate viscous solution, J. Fluid Mech., Volume 351 (1997), pp. 119-138
[16] L. Gostiaux, Etude expérimentale des ondes de gravité internes en présence de topographie. Emission, propagation, réflexion, Thèse de Doctorat de l'Ecole Normale Supérieure de Lyon, 2006
[17] B. Voisin, Internal waves from oscillating objects, in: Sixth International Symposium on Stratified Flows, Perth, Australia, 11–14 December 2006
[18] B. Voisin, Added mass effects on internal wave generation, in: Fifth International Symposium on Environmental Hydraulics, Tempe, AZ, USA, 4–7 December 2007
[19] Instability mechanisms of a two-dimensional progressive internal gravity wave, J. Fluid Mech., Volume 548 (2006), pp. 165-195
[20] Instability and breakdown of internal gravity waves. I. Linear stability analysis, Phys. Fluids, Volume 8 (1996) no. 12, p. 3271
[21] Turbulence in Fluids, Kluwer Academic Publishers, 1997
[22] Theories of internal wave interaction and stably stratified turbulence: testing against numerical simulations (J.C. Nihoul; B.M. Jamard, eds.), Small-Scale Turbulence and Mixing in the Ocean, Aha Huliko'a Hawaiian Winter Workshop, Elsevier, New York, 1988, pp. 363-377
[23] A survey of internal waves and small scale processes (B.A. Warren; C. Wunsch, eds.), Evolution of Physical Oceanography, MIT Press, Cambridge, MA, 1981, pp. 264-291
[24] Gravity wave dynamics and effects in the middle atmosphere, Rev. Geophys., Volume 41 (2003) no. 1 (Art. No. 1003)
[25] Stratified turbulence generated by internal gravity waves, J. Fluid Mech., Volume 546 (2006), pp. 313-339
[26] On the velocity field associated with potential vorticity, Dynam. Atmos. Oceans, Volume 14 (1989), pp. 93-123
[27] Fluid motions in the presence of strong stable stratification, Annu. Rev. Fluid Mech., Volume 32 (2000), pp. 613-657
[28] Turbulence and vortex structures in rotating and stratified flows, Eur. J. Mech. B/Fluids, Volume 20 (2001), pp. 489-510
[29] Gravity and inertia–gravity internal waves: breaking processes and induced mixing, Surv. Geophys., Volume 25 (2004) no. 3–4, pp. 281-314
[30] Dynamics of turbulence strongly influenced by buoyancy, Phys. Fluids, Volume 15 (2003), pp. 2047-2059
[31] Energy dissipation and vortex structure in freely-decaying stratified grid-turbulence, Dynam. Atmos. Oceans, Volume 23 (1996), pp. 155-169
[32] Decaying grid turbulence in a rotating stratified fluid, J. Fluid Mech., Volume 547 (2006), pp. 389-412
[33] Diapycnal mixing in the thermocline: a review, J. Geophys. Res., Volume 92 (1987) no. C5, pp. 5249-5286
[34] Turbulent mixing at a shear-free density interface, J. Fluid Mech., Volume 189 (1988), pp. 211-234
[35] Stratified turbulence produced by internal wave breaking: two-dimensional numerical experiments, Dynam. Atmos. Oceans, Volume 23 (1996), p. 357
[36] Nonlinear internal gravity wave beams, J. Fluid Mech., Volume 482 (2003), pp. 141-161
[37] Abyssal recipes II: energetics of tidal mixing and wind mixing, Deep Sea Res. I, Volume 45 (1998), pp. 1977-2010
[38] Nonlinear interaction among internal wave beams generated by tidal flow over supercritical topography, Geophys. Res. Lett., Volume 31 (2004), p. L09313
[39] Preliminary simulations of internal waves and mixing generated by finite amplitude tidal flow over isolated topography, Deep Sea Res. II, Volume 53 (2006), pp. 140-156
[40] Nonlinear effects in internal tide beams and mixing, Ocean Modelling, Volume 12 (2006), pp. 302-318
[41] Decay of semi-diurnal internal-tide beams due to subharmonic resonance, Geophys. Res. Lett., Volume 33 (2006), p. L08604
[42] Nonlinear energy transfer within the oceanic internal wave spectrum at mid and high latitudes, J. Geophys. Res., Volume 107 (2002) no. C11, p. 3207
[43] Global mapping of diapycnal diffusivity in the deep ocean based on the results of expendable current profiler (XCP) surveys, Geophys. Res. Lett., Volume 33 (2006) no. 3, p. L03611
[44] Internal and interfacial tides: beam scattering and local generation of solitary waves, J. Mar. Res., Volume 59 (2006) no. 2, pp. 227-255
[45] Local generation of internal soliton packets in the central Bay of Biscay, Deep-Sea Res., Volume 39 (1992), pp. 1521-1534
[46] Joseph Boussinesq and his approximation: a contemporary view, C. R. Mécanique, Volume 331 (2003), pp. 575-586
[47] Energy transfer between external and internal gravity waves, J. Fluid Mech., Volume 19 (1964), pp. 465-478
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