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<p>Internal solitary waves can generate intense bottom currents and turbulent mixing over continental slopes, influencing the redistribution of sediments and pollutants, as well as driving changes in marine geomorphology and ecosystems. However, owing to the lack of detailed quantitative measurements of the bottom boundary layer, the mechanisms and impacts of internal solitary waves in resuspending and transporting seafloor sediments remain poorly understood. In this study, we present high-resolution <i>in situ</i> observations of hydrodynamics in the upper layer (14–265 m) and the bottom boundary layer (&lt;1 m) in the continental shelf slope break zone. Our results reveal that strongly nonlinear internal solitary waves, which occur at the peak of semidiurnal tidal currents, trigger benthic storms at the seafloor. Unlike previously proposed global instability mechanisms, the suspended sediment concentration caused by these strongly nonlinear internal solitary waves reaches 60 times higher than the background value and exhibits sudden, transient peaks. The bottom shear stress (<i>τ</i>) is an order of magnitude greater than that in laboratory measurements, and the observed fluctuating pressure is approximately 2.3 to 7 times greater than that in previous coastal observations. The sediments stirred by benthic storms are transported vertically to more than 100 m above the seabed, with lateral transport extending tens of kilometres beyond the study area. This process is driven by the dynamic mechanism of “strongly nonlinear internal solitary waves lifting sediments, weakly nonlinear internal solitary waves assisted by internal tides, and contour currents transporting sediments.” The suspended sediment flux induced by internal solitary waves in the South China Sea is on the same order of magnitude as that of global dust storm emissions, 21.9 times the volume of Asian dust storms entering the sea, and approximately 21 times the fluvial sediment flux entering the northern South China Sea. These findings are significant for evaluating sedimentary processes and ecological–geochemical impacts in the northern South China Sea, offering a novel perspective on marine ecological environments and carbon sequestration processes.</p>

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Internal solitary waves in the Shenhu continental shelf slope break zone of the northern South China Sea generate benthic storms

  • 期刊论文

  • 发表日期：

    2025年2月17日

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  • Yonggang Jia,
  • Xuezhi Feng,
  • Chaoqi Zhu,
  • Linsen Wang,
  • Xiaolei Liu,
  • Cong Hu,
  • Hongwei Wang

摘要

Internal solitary waves can generate intense bottom currents and turbulent mixing over continental slopes, influencing the redistribution of sediments and pollutants, as well as driving changes in marine geomorphology and ecosystems. However, owing to the lack of detailed quantitative measurements of the bottom boundary layer, the mechanisms and impacts of internal solitary waves in resuspending and transporting seafloor sediments remain poorly understood. In this study, we present high-resolution in situ observations of hydrodynamics in the upper layer (14–265 m) and the bottom boundary layer (<1 m) in the continental shelf slope break zone. Our results reveal that strongly nonlinear internal solitary waves, which occur at the peak of semidiurnal tidal currents, trigger benthic storms at the seafloor. Unlike previously proposed global instability mechanisms, the suspended sediment concentration caused by these strongly nonlinear internal solitary waves reaches 60 times higher than the background value and exhibits sudden, transient peaks. The bottom shear stress (τ) is an order of magnitude greater than that in laboratory measurements, and the observed fluctuating pressure is approximately 2.3 to 7 times greater than that in previous coastal observations. The sediments stirred by benthic storms are transported vertically to more than 100 m above the seabed, with lateral transport extending tens of kilometres beyond the study area. This process is driven by the dynamic mechanism of “strongly nonlinear internal solitary waves lifting sediments, weakly nonlinear internal solitary waves assisted by internal tides, and contour currents transporting sediments.” The suspended sediment flux induced by internal solitary waves in the South China Sea is on the same order of magnitude as that of global dust storm emissions, 21.9 times the volume of Asian dust storms entering the sea, and approximately 21 times the fluvial sediment flux entering the northern South China Sea. These findings are significant for evaluating sedimentary processes and ecological–geochemical impacts in the northern South China Sea, offering a novel perspective on marine ecological environments and carbon sequestration processes.