Regional study of mode-2 internal solitary waves in the Pacific coast of Central America using marine seismic survey data

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).