An acoustic image of an internal wave field from seismic reflection profiles across the shelf break of northern South China Sea (top), reveals the generation of internal (wave) bores, hydraulic jumps, billows and wave-breaking (bottom). Credit: Tang et al., 2018, Figure 10
Source: Journal of Geophysical Research: Oceans

Internal gravity waves affect and determine ocean processes in many ways, such as ocean mixing that is crucial for a more complete understanding of the climate system, or for supply of nutrients for photosynthesis to support biological production. Yet because of their relatively short time scales (minutes to hours), small spatial scales (tens to hundreds of meters), and vast travel distances (hundreds to thousands of kilometers), internal gravity waves in the ocean are difficult to observe and measure in a comprehensive way. Tang et al. [2018] use seismic measurements to resolve fine-scale internal wave structures in northern South China Sea. The technique of using seismic data to reveal ocean fine scales was developed more than 10 years ago [Holbrook et al., 2003]. But this paper demonstrates how the technique helps reveal hydraulic jumps, wave breaking and shear instability, potentially providing much greater insight to mixing in the ocean interior. At the high resolution of tens of meters, the data in fact now even pose a challenge to modelers!

Citation: Tang, Q., Xu, M., Zheng, C., Xu, X., & Xu, J. [2018]. A locally generated high-mode nonlinear internal wave detected on the shelf of the northern South China Sea from marine seismic observations. Journal of Geophysical Research: Oceans, 123

 —Lie-Yauw Oey, Editor, JGR: Oceans

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