On the Generation and Evolution of Internal Solitary Waves in the Andaman Sea

Internal solitary waves (ISWs) are ubiquitous in the Andaman Sea, as revealed by synthetic aperture radar images; however, their generation mechanisms and corresponding influencing factors remain unknown. Based on a nonhydrostatic two-dimensional model, the generation of ISW packets along the transect of a channel lying between Batti Malv Island and Car Nicobar Island is investigated. Moreover, the influences of topographic characteristics, seasonal stratifications, and tidal forcings are analyzed through a series of sensitivity runs. The simulation results indicate that bidirectional rank-ordered ISW packets are generated by the nonlinear steepening of internal tides. An east-west ISW asymmetry is observed, which is attributed to distinct topographic characteristics. The surrounding sills can also generate internal wave beams, which modulate the intensity of ISWs. However, the topographic structure of the west flank of the ridge mainly contributes to the suppression of westward ISWs, which decreases the modulating effect of internal wave beams. During the spring tide, the generation of ISWs is enhanced. During the neap tide, ISWs are weak, and the east-west ISW asymmetry is less obvious. Moreover, seasonal stratification only has a minor effect on the generation and evolution of ISWs.