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

Abstract. In this paper, a regional study of mode-2 internal solitary waves (ISWs) at the Pacific coast of Central America is carried out using the seismic reflection method. The observed relationship between the dimensionless propagation speed and the dimensionless amplitude (DA) of the mode-2 ISW is analyzed. When DA < 1.18, the dimensionless propagation speed seems to increase with increasing DA, divided into two parts with different growth rates. When DA > 1.18, the dimensionless propagation speed increases with increasing DA at a relatively small growth rate. We suggest that the influences of seawater depth (submarine topography), pycnocline depth, and pycnocline thickness on the propagation speed of the mode-2 ISW in the study area cause the relationship between dimensionless propagation speed and DA to diversify. The observed relationship between the dimensionless wavelength and the DA of the mode-2 ISW is also analyzed. When DA < 1, the nondimensional wavelengths seem to change from 2.5 to 7 for a fixed nondimensional amplitude. When DA > 1.87, the dimensionless wavelength increases with increasing DA. Additionally, the seawater depth has a great influence on the wavelength of the mode-2 ISW in the study area. Overall, the wavelength increases with increasing seawater depth. As for the vertical structure of the amplitude of the mode-2 ISW in the study area, we find that it is affected by the nonlinearity of the ISW and the pycnocline deviation (especially the downward pycnocline deviation).