Abstract
In this paper, a regional study of the mode-2 internal solitary waves (ISWs) in the Pacific coast of Central America is carried out by using seismic reflection method. The observed relationship between the dimensionless phase velocity and the dimensionless amplitude (DA) of the mode-2 ISWs was analysed. When DA < 1, the dimensionless phase velocity increases with the increasing dimensionless amplitude, divided into two parts with different growth rates. When DA > 1, the dimensionless phase velocity increases with the increasing dimensionless amplitude at a relatively small growth rate. We suggest that the influences of seawater depth (submarine topography), pycnocline depth, and pycnocline thickness on the phase velocity of the mode-2 ISWs in the study area, cause the relationship between the dimensionless phase velocity and the dimensionless amplitude diversified. The observed relationship between the dimensionless wavelength and the dimensionless amplitude of the mode-2 ISWs was also analysed. When DA < 1 and DA > 2, the dimensionless wavelength decreases and increases with the increasing dimensionless amplitude, respectively. Additionally, the seawater depth has a great influence on the wavelength of the mode-2 ISWs in the study area, and overall the wavelength increases with the increasing seawater depth. As for the vertical structure of the amplitude of the mode-2 ISWs in the study area, we find that it is affected by the nonlinearity of the ISWs and the pycnocline deviation (especially the downward pycnocline deviation).
Highlights
State Key laboratory of Marine Geology, School of Ocean and Earth Science, Tongji University, Shanghai, 200092, ChinaThe amplitude and propagation velocity of the mode-1 internal solitary waves (ISWs) are larger than those in the mode-2 ISWs
We suggest that the influences of seawater depth, pycnocline depth, and pycnocline thickness on the phase velocity of the mode-2 ISWs in the study area, cause the relationship between the dimensionless phase velocity and the dimensionless amplitude diversified
In addition to the survey lines L88 and L76 with mode-2 ISWs observed by Fan et al (2021a, 2021b), we found mode-2 ISWs on many other survey lines in the study area
Summary
State Key laboratory of Marine Geology, School of Ocean and Earth Science, Tongji University, Shanghai, 200092, ChinaThe amplitude and propagation velocity of the mode-1 ISWs are larger than those in the mode-2 ISWs. ISWs are more common in the ocean. With the advancement of observation instruments, the mode-2 ISWs in the ocean have been gradually observed, such as on the New Jersey shelf (Shroyer et al, 2010), in the South China Sea (Liu et al, 2013; Ramp et al, 2015; Yang et al, 2009), at Georges Bank (Bogucki et al, 2005), over Mascarene Ridge in Indian. Conventional physical oceanography observation and remote sensing observation have spatial resolution limitations. The horizontal resolution of conventional physical oceanography observation methods (such as mooring) is low, and the vertical resolution of remote sensing observations is low. Seismic oceanography (Holbrook et al, 2003; Ruddick et al, 2009), as a new oceanography survey method, has high spatial resolution
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