Abstract
Internal waves with high vertical wavenumber structures on the northern part of the eastern ridge in Luzon Strait were investigated using shipboard observations and a wave propagation model. Detailed repeat observations across the ridge revealed complex undulations of isopycnals near the ridge that were characterized by vertically alternating concave and convex structures. In addition, strong eastward and westward flow areas with horizontal and vertical scales of 3–5 km and 150–250 m, respectively, occurred alternately on the downstream side of the ridge. These high-wavenumber structures in flow and density fields were associated with internal waves generated by interactions between diurnal tidal flow and the meridional submarine ridge in the strait; an acoustic Doppler current profiler recorded no signals of the Kuroshio Current and semi-diurnal tides in the zonal flow on the western slope of the eastern ridge. Many temperature inversions around the ridge exhibited vertical scales of predominantly ~ 30 m. Simple calculations of internal wave motion reveal that each internal wave mode tends to stagnate near the summits of the ridge depending on the direction and strength of the background tidal flow. This suggests that the observed high-wavenumber structure in the flow profiles near the ridge is ascribed to the superposition of transient internal wave modes, although this is not the main cause of the temperature inversions. As a possible mechanism to explain the temperature inversions, we propose that higher-mode internal waves emanating from the unresolved topographic undulations are trapped by the observed high-wavenumber structures, resulting in turbulent mixing.
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References
Alford MH, MacKinnon JA, Nash JD, Simmons H, Pickering A, Klymak M, Pinkel R, Sun L, Rainville L, Musgrave R, Beitzel T, Fu KH, Lu CW (2011) Energy flux and dissipation in Luzon Strait: Two tales of two ridges. J Phys Oceanogr 41:2211–2222
Alford MH, Peacock T, Mackinnon JA, Nash JD, Buijsman MC, Centurioni LR, Chao SY, Chang MH, Farmer DM, Fringer OB, Fu KH, Gallacher PC, Graber HC, Helfrich KR, Jachec SM, Jackson CR, Klymak JM, Ko DS, Jan S, Johnston TMS, Legg S, Lee IH, Lien RC, Mercier MJ, Moum JN, Musgrave R, Park JH, Pickering AI, Pinkel R, Rainville L, Ramp SR, Rudnick DL, Sarkar S, Scotti A, Simmons HL, St Laurent LC, Venayagamoorthy SK, Wang YH, Wang J, Yang YJ, Paluszkiewicz T, Tang TY (2015) The formation and fate of internal waves in the South China Sea. Nature 521(7550):65–69
Buijsman MC, Legg S, Klymak J (2012) Double-ridge internal tide interference and its effect on dissipation in Luzon Strait. J Phys Oceanogr 42:1337–1356
Buijsman MC, Klymak JM, Legg S, Alford MH, Farmer D, MacKinnon JA, Nash JD, Park JH, Pickering A, Simmons H (2014) Three-dimensional double-ridge internal tide resonance in Luzon Strait. J Phys Oceanogr 44:850–869
Centurioni LR, Niiler PP, Lee DK (2004) Observations of inflow of Philippine sea surface water into the South China Sea through the Luzon Strait. J Phys Oceanogr 34:113–121
Chang MH, Jheng SY, Lien RC (2016) Trains of large Kelvin-Helmholtz billows observed in the Kuroshio above a seamount. Geophys Res Lett 43:8654–8661
Cushman-Roisin B, Beckers JM (2011) Introduction to geophysical fluid dynamics: physical and numerical aspects, 2nd edn. Academic Press, Waltham, p 828
Egbert GD, Erofeeva SY (2002) Efficient inverse modeling of barotropic ocean tides. J Atmos Ocean Technol 19:183–204
Gill A (1982) Atmosphere–ocean dynamics. Academic Press, Orlando, p 662
Guo C, Chen X (2014) A review of internal solitary wave dynamics in the northern South China Sea. Prog Oceanogr 121:7–23
Hibiya T (1986) Generation mechanism of internal waves by tidal flow over a sill. J Geophys Res 91(C6):7697–7708
Hibiya T (1988) The generation of internal waves by tidal flow over Stellwagen Bank. J Geophys Res 93(C1):533–542
Hibiya T (2004) Internal wave generation by tidal flow over a continental shelf slope. J Oceanogr 60:637–643
Hibiya T, Nagasawa M, Niwa Y (2002) Nonlinear energy transfer within the oceanic internal wave spectrum at mid and high latitudes. J Geophys Res Ocean 107(C11):3207. https://doi.org/10.1029/2001JC001210
Hibiya T, Ijichi T, Robertson R (2017) The impacts of ocean bottom roughness and tidal flow amplitude on abyssal mixing. J Geophys Res Ocean 122:5645–5651. https://doi.org/10.1002/2016JC012564
Jalali M, Sarkar S (2017) Large eddy simulation of flow and turbulence at the steep topography of Luzon Strait. Geophys Res Lett 44:9440–9448
Jan S, Chern CS, Wang J, Chao SY (2007) Generation of diurnal K1 internal tide in the Luzon Strait and its influence on surface tide in the South China Sea. J Geophys Res 112:C06019. https://doi.org/10.1029/2006JC004003
Jan S, Lien RC, Ting CH (2008) Numerical study of baroclinic tides in Luzon Strait. J Oceanogr 64:789–802
Jan S, Chern CS, Wang J, Chiou MD (2012) Generation and propagation of baroclinic tides modified by the Kuroshio in the Luzon Strait. J Geophys Res 117:C02019. https://doi.org/10.1029/2011JC007229
Liang WD, Yang YJ, Tang TY, Chuang WS (2008) Kuroshio in the Luzon Strait. J Geophys Res 113:C08047. https://doi.org/10.1029/2007JC004609
Nagai T, Hasegawa D, Tanaka T, Nakamura H, Tsutsumi E, Inoue R, Yamashiro T (2017) First evidence of coherent bands of strong turbulent layers associated with high-wavenumber internal-wave shear in the upstream Kuroshio. Sci Rep 7:14555. https://doi.org/10.1038/s41598-017-15167-1
Nikurashin M, Ferrari R (2010) Radiation and dissipation of internal waves generated by geostrophic motions impinging on small-scale topography: theory. J Phys Oceanogr 40:1055–1074
Niwa Y, Hibiya T (2001) Numerical study on the spatial distribution of the M2 internal tide in the Pacific Ocean. J Geophys Res 106(C10):22441–22449
Niwa Y, Hibiya T (2004) Three-dimensional numerical simulation of M2 internal tides in the East China Sea. J Geophys Res 109:C04027. https://doi.org/10.1029/2003JC001923
Pickering A, Alford M, Nash J, Rainville L, Buijsman M, Ko DS, Lim B (2015) Structure and variability of internal tides in Luzon Strait. J Phys Oceanogr 45:1574–1594
Pinkel R, Buijsman M, Klymak JM (2012) Breaking topographic lee waves in a tidal channel in Luzon Strait. Oceanography 25:160–165. https://doi.org/10.5670/oceanog.2012.51
Rainville L, Pinkel R (2004) Observations of energetic high-wavenumber internal waves in the Kuroshio. J Phys Oceanogr 34:1495–1505
Rainville L, Lee CM, Rudnick DL, Yang KC (2013) Propagation of internal tides generated near Luzon Strait: Observations from autonomous gliders. J Geophys Res Ocean 118:4125–4138. https://doi.org/10.1002/jgrc.20293
Simmons HL, Hallberg RW, Arbic BK (2004) Internal wave generation in a global baroclinic tide model. Deep Sea Res II 51:3043–3068
Tsutsumi E, Matsuno T, Lien RC, Nakamura H, Senjyu T, Guo X (2017) Turbulent mixing within the Kuroshio in the Tokara Strait. J Geophys Res Ocean. https://doi.org/10.1002/2017JC013049
Tsutsumi E, Matsuno T, Itoh S, Zhang J, Senjyu T, Sakai A, Lee K, Yanagimoto D, Yasuda I, Ogawa H, Villanoy C (2020) Vertical fluxes of nutrients enhanced by strong turbulence and phytoplankton bloom around the ocean ridge in the Luzon Strait. Sci Rep. https://doi.org/10.1038/s41598-020-74938-5
Wang YH, Dai CF, Chen YY (2007) Physical and ecological processes of internal waves on an isolated reef ecosystem in the South China Sea. Geophys Res Lett 34:L18609. https://doi.org/10.1029/2007GL030658
Yasuda I, Masuda S, Nishioka J, Guo X, Harada N, Ito S, Hibiya T, Hasumi H (2020) Ocean mixing processes (OMIX): impact on biogeochemistry, climate and ecosystems. J Oceanogr. https://doi.org/10.1007/s10872-020-00578-y
Zhao Z (2014) Internal tide radiation from the Luzon Strait. J Geophys Res Ocean 119:5434–5448. https://doi.org/10.1002/2014JC010014
Acknowledgements
We thank the captain and crew of the R/V Hakuho Maru of the JAMSTEC and all the participants of leg 2 of the KH17-5 cruise. Part of the instrumentation used in the study was provided by D. Hasegawa and X. Guo. Thanks are also due to Y. Niwa and T. Nagai for their useful suggestions on numerical calculations. The original manuscript has been greatly improved by insightful comments from T. Hibiya and an anonymous reviewer. This study was supported by MEXT KAKENHI Grant Number JP15H05821.
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Sakai, A., Senjyu, T., Matsuno, T. et al. Internal waves with high vertical wavenumber structure generated by diurnal tidal flow over the eastern ridge of Luzon Strait. J Oceanogr 77, 703–718 (2021). https://doi.org/10.1007/s10872-021-00615-4
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DOI: https://doi.org/10.1007/s10872-021-00615-4