Oceanography > Issues > Archive > Volume 25, Issue 2

2012, Oceanography 25(2):96–107, http://dx.doi.org/10.5670/oceanog.2012.45

Internal Solitary Waves in the Red Sea: An Unfolding Mystery

Authors | Abstract | Full Article | Citation | References







Authors

José C.B. da Silva | Department of Geosciences, Environment and Spatial Planning and Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR), University of Porto, Portugal, and Guest Investigator, Woods Hole Oceanographic Institution, Woods Hole, MA, USA

Jorge M. Magalhães | Department of Geosciences, Environment and Spatial Planning, University of Porto, Portugal

Theo Gerkema | Royal Netherlands Institute for Sea Research (NIOZ), Texel, the Netherlands

Leo R.M. Maas | NIOZ, Texel, the Netherlands, and Institute for Marine and Atmospheric Research Utrecht, Utrecht University, the Netherlands

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Abstract

The off-shelf region between 16.0° and 16.5°N in the southern Red Sea is identified as a new hotspot for the occurrence of oceanic internal solitary waves. Satellite observations reveal trains of solitons that, surprisingly, appear to propagate from the center of the Red Sea, where it is deepest, toward the continental shelf, but they do not survive as coherent structures over the shelf. These solitons are characterized by coherent crest lengths exceeding 80 km and crest-to-crest distances of more than 2 km, compatible with signatures of large-amplitude solitary waves. Despite the fact that these Red Sea solitons have large amplitudes, they appear to be generated by very weak surface tides. Tidal current velocity is only about 5 cm s–1 over the shelf, much weaker than over other ocean shelves where similar solitary waves have been reported. The appearance of these waves over this particular geographical stretch suggests generation by a locally amplified internal tide on the main pycnocline. We consider three possible explanations for soliton generation in the Red Sea: interfacial tide resonance, local generation by internal tidal beams generated at the shelf breaks, and local generation by internal tidal beams generated at the shelf breaks but first amplified by repeated focusing reflections.

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Full Article

2.86 MB pdf

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Citation

da Silva, J.C.B., J.M. Magalhães, T. Gerkema, and L.R.M. Maas. 2012. Internal solitary waves in the Red Sea: An unfolding mystery. Oceanography 25(2):96–107, http://dx.doi.org/10.5670/oceanog.2012.45.

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References

Akylas, T.R., R.H.J. Grimshaw, S.R. Clark, and A. Tabaei. 2007. Reflecting tidal wave beams and local generation of solitary waves in the ocean thermocline. Journal of Fluid Mechanics 593:297–313, http://dx.doi.org/10.1017/S0022112007008786.

Alford, M.H., R. Lien, H. Simmons, J.M. Klymak, S. Ramp, Y.J. Yang, D. Tang, and M.-H. Chang. 2010. Speed and evolution of nonlinear internal waves transiting the South China Sea. Journal of Physical Oceanography 40:1,338–1,355, http://dx.doi.org/10.1175/2010JPO4388.1.

Alford, M.H., J.A. MacKinnon, J.D. Nash, H. Simmons, A. Pickering, J.M. Klymak, R. Pinkel, O. Sun, L. Rainville, R. Musgrave, and others. 2011. Energy flux and dissipation in Luzon Strait: Two tales of two ridges. Journal of Physical Oceanography 41:2,211–2,222, http://dx.doi.org/10.1175/JPO-D-11-073.1.

Alpers, W. 1985. Theory of radar imaging of internal waves. Nature 314:245–247, http://dx.doi.org/10.1038/314245a0.

Azevedo, A., J.C.B. da Silva, and A.L. New. 2006. On the generation and propagation of internal solitary waves in the southern Bay of Biscay. Deep-Sea Research Part I 53:927–941, http://dx.doi.org/10.1016/j.dsr.2006.01.013.

Buijsman, M.C., J.C. McWilliams, and C.R. Jackson. 2010. East‐west asymmetry in nonlinear internal waves from Luzon Strait. Journal of Geophysical Research 115, C10057, http://dx.doi.org/10.1029/2009JC006004.

da Silva, J.C.B., S.A. Ermakov, I.S. Robinson, D.R.G. Jeans, and S.V. Kijashko. 1998. Role of surface films in ERS SAR signatures of internal waves on the shelf: Part 1. Short-period of internal waves. Journal of Geophysical Research 103(C4):8,009–8,031, http://dx.doi.org/10.1029/97JC02725.

da Silva, J.C.B, A.L. New, and A. Azevedo. 2007. On the role of SAR for observing “local generation” of internal solitary waves off the Iberian Peninsula. Canadian Journal of Remote Sensing 33:388–403, http://dx.doi.org/10.5589/m07-041.

da Silva, J.C.B., A.L. New, and J.M. Magalhães. 2009. Internal solitary waves in the Mozambique Channel: Observations and interpretation. Journal of Geophysical Research 114, C05001, http://dx.doi.org/10.1029/2008JC005125.

da Silva, J.C.B., A.L. New, and J.M. Magalhães. 2011. On the structure and propagation of internal solitary waves generated at the Mascarene Plateau in the Indian Ocean. Deep-Sea Research Part I 58:229–240, http://dx.doi.org/10.1016/j.dsr.2010.12.003.

Egbert, G.D., and S.Y. Erofeeva. 2002. Efficient inverse modeling of barotropic ocean tides. Journal of Atmospheric and Oceanic Technology 19:183–204, http://dx.doi.org/10.1175/1520-0426(2002)019<0183:EIMOBO>2.0.CO;2.

Farmer, D., Q. Li, and J.‐H. Park. 2009. Internal wave observations in the South China Sea: The role of rotation and non‐linearity. Atmosphere-Ocean 47:267–280, http://dx.doi.org/10.3137/OC313.2009.

Gerkema, T. 1996. A unified model for the generation and fission of internal tides in a rotating ocean. Journal of Marine Research 54:421–450, http://dx.doi.org/10.1357/0022240963213574.

Gerkema, T. 2001. Internal and interfacial tides: Beam scattering and local generation of solitary waves. Journal of Marine Research 59:227–255, http://dx.doi.org/10.1357/002224001762882646.

Gerkema, T., J.T.F. Zimmerman, L.R.M. Maas, and H. van Haren. 2008. Geophysical and astrophysical fluid dynamics beyond the traditional approximation. Reviews of Geophysics 46, RG2004, http://dx.doi.org/10.1029/2006RG000220.

Grisouard, N., C. Staquet, and T. Gerkema. 2011. Generation of internal solitary waves in a pycnocline by an internal wave beam: A numerical study. Journal of Fluid Mechanics 676:491–513, http://dx.doi.org/10.1017/jfm.2011.61.

Hazewinkel, J., P. van Breevoort, S.B. Dalziel, and L.R.M. Maas. 2008. Observations on the wavenumber spectrum and decay of an internal wave attractor. Journal of Fluid Mechanics 598:373–382, http://dx.doi.org/10.1017/S0022112007000031.

Hazewinkel, J., C. Tsimitri, L.R.M. Maas, and S.B. Dalziel. 2010. Observations on the robustness of internal wave attractors to perturbations. Physics of Fluids 22, 107102, http://dx.doi.org/10.1063/1.3489008.

Jackson, C.R. 2007. Internal wave detection using the Moderate Resolution Imaging Spectroradiometer (MODIS). Journal of Geophysical Research 112, C11012, http://dx.doi.org/10.1029/2007JC004220.

Jackson, C.R., and W. Alpers. 2010. The role of the critical angle in brightness reversals on sunglint images of the sea surface. Journal of Geophysical Research 115, C09019, http://dx.doi.org/10.1029/2009JC006037.

Jackson, C.R., J.C.B. da Silva, and G. Jeans. 2012. The generation of nonlinear internal waves. Oceanography 25(2):108–123, http://dx.doi.org/10.5670/oceanog.2012.46.

Kitade, Y., Y. Igeta, R. Fujii, and M. Ishii. 2011. Amplification of semidiurnal internal tide observed in the outer part of Tokyo Bay. Journal of Oceanography 67:613–625, http://dx.doi.org/10.1007/s10872-011-0061-0.

Konyaev, K.V., K.D. Sabinin, and A.N. Serebryany. 1995. Large-amplitude internal waves at the Mascarene Ridge in the Indian Ocean. Deep-Sea Research Part I 42:2,075–2,091, http://dx.doi.org/10.1016/0967-0637(95)00067-4.

Maas, L.R.M. 2005. Wave attractors: Linear yet nonlinear. International Journal of Bifurcation and Chaos 15:2,757–2,782.

Maas, L.R.M., and F.P.A. Lam. 1995. Geometric focusing of internal waves. Journal of Fluid Mechanics 300:1–41, http://dx.doi.org/10.1017/S0022112095003582.

Magalhães, J.M., I.B. Araujo, J.C.B. da Silva, R.H.J. Grimshaw, K. Davis, and J. Pineda, 2011. Atmospheric gravity waves in the Red Sea: A new hotspot. Nonlinear Processes in Geophysics 18:71–79, http://dx.doi.org/10.5194/npg-18-71-2011.

Mercier, M.J., M. Mathur, L. Gostiaux, T. Gerkema, J.M. Magalhães, J.C.B da Silva, and T. Dauxois. In press. Soliton generation by internal tidal beams impinging on a pycnocline: Laboratory experiments. Journal of Fluid Mechanics.

New, A.L., and J.C.B. da Silva. 2002. Remote-sensing evidence for the local generation of internal soliton packets in the central Bay of Biscay. Deep-Sea Research Part I 49:915–934, http://dx.doi.org/10.1016/S0967-0637(01)00082-6.

New, A.L., and R.D. Pingree. 1992. Local generation of internal soliton packets in the central Bay of Biscay. Deep-Sea Research Part A 39:1,521–1,534, http://dx.doi.org/10.1016/0198-0149(92)90045-U.

Pingree, R.D., G.T. Mardell, and A.L. New. 1986. Propagation of internal tides from the upper slopes of the Bay of Biscay. Nature 312:154–158, http://dx.doi.org/10.1038/321154a0.

Sofianos, S.S., and W.E. Johns. 2007. Observations of the summer Red Sea circulation. Journal of Geophysical Research 112, C06025, http://dx.doi.org/10.1029/2006JC003886.

Vlasenko, V., N. Stashchuk, and K. Hutter. 2005. Baroclinic Tides: Theoretical Modeling and Observational Evidence. Cambridge University Press, Cambridge, UK, 351 pp.

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