Observations of Internal Structure Changes in Shoaling Internal Solitary Waves Based on Seismic Oceanography Method

Abstract

High spatial resolution and deep detection depths of seismic reflection surveying are conducive to studying the fine structure of the internal solitary wave. However, seismic images are instantaneous, which are not conducive to observing kinematic processes of the internal solitary waves. We improved the scheme of seismic data processing and used common-offset gathers to continuously image the same location. In this way, we can observe internal fine structure changes during the movement of the internal solitary waves, especially the part in contact with the seafloor. We observed a first-mode depression internal solitary wave on the continental slope near the Dongsha Atoll of the South China Sea and short-term shoaling processes of the internal solitary wave by using our improved method. We found that the change in shape of waveform varies at different depths. We separately analyzed the evolution of the six waveforms at different depths. The results showed that the waveform in deep water deforms before that in shallow water and the waveform in shallow water deforms to a greater degree. We measured four parameters of the six waveforms during the shoaling including phase velocity, amplitude, wavelength, and slopes of leading and trailing edge. The phase velocity and amplitudes of waveforms in shallow water increase, the wavelengths decrease, and the slopes of trailing edge gradually become larger than that of the leading edge, while the amplitudes of the deep water waveforms do not change significantly and the phase velocities decrease. Our results are consistent with previous studies made by numerical simulations, which suggest the effectiveness of the new processing scheme. This improved scheme cannot only study the internal solitary waves shoaling, but also has great potential in the study of other ocean dynamics.

Experimental and observational analysis of vertical characteristics of internal solitary waves

“…Generally, ISWs in the SCS are excited by the Luzon Strait and propagate westward. When ISWs pass by the Dongsha Atoll, the polarity inversion and breaking of the ISWs occur easily due to the changes of ocean stratification and topography [3]. Large shear forces in the vertical direction of ISWs can cause damage to marine platforms or submarines [4][5][6].…”

Research on the fluid dynamics interaction between submarine sand waves and seawater by seismic oceanography

“…Compared with traditional geophysical methods of seafloor survey, seismic oceanography can image not only oceanographic phenomena in seawater, but also the important marine processes happening near the seafloor (Song et al, 2021a). Seismic oceanography (Holbrook et al, 2003) has been applied to study various oceanographic phenomena, including fronts (Holbrook et al, 2003;Tsuji et al, 2005), water mass boundaries (Nandi et al, 2004), mesoscale eddies (Biescas et al, 2008;Meńesguen et al, 2009;Song et al, 2009;Pinheiro et al, 2010;Quentel et al, 2010;Tang et al, 2014), internal waves (Holbrook and Fer, 2005;Krahmann et al, 2008;Song et al, 2009;Song et al, 2021b), submesoscale processes (Sallares et al, 2016;Tang et al, 2020;Yang et al, 2021), and seafloor processes (Vsemironva et al, 2012;Chen et al, 2016;Chen et al, 2017;Chen et al, 2018;Geng et al, 2019;Yin et al, 2021). More recently, seismic reflection studies have now been used to look at the evolution of marine processes over time (Dickinson et al, 2020;Gunn et al, 2020;Zou et al, 2021;Dickinson and Gunn, 2022).…”