Abstract
Internal solitary waves (ISWs) are ubiquitous in the Andaman Sea, as revealed by synthetic aperture radar (SAR) images, but their generation mechanisms and corresponding influencing factors remain unknown. Based on a nonhydrostatic two-dimensional model, the generation of ISW packets along a transect of a channel lying between Batti Malv Island and Car Nicobar Island is investigated. Additionally, the influences of topographic characteristics, seasonal stratification variables and tidal forcings are analysed through a series of sensitivity runs. The simulated 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 are also capable of generating 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 decrease the modulating effect of internal wave beams. During spring tide, the generation of ISWs is enhanced. Under neap tide, ISWs are weak, and the east-west ISW asymmetry is less obvious. Moreover, seasonally varied stratification only has a minor effect on the generation and evolution of ISWs.
Highlights
Internal solitary waves (ISWs) are a ubiquitous phenomenon in marginal seas (Jackson, 2007)
The surrounding sills are capable of generating internal wave beams, which modulate the intensity of ISWs
The energy of the eastward ISWs reaches 74.2 kJ/m2, which is basically four times larger than that of the westward ISWs. These results indicate that ISWs are observed in both the Bay of Bangel (BoB) and the Andaman Sea (AS), ISWs in the two regions have different intensities
Summary
Internal solitary waves (ISWs) are a ubiquitous phenomenon in marginal seas (Jackson, 2007). Accompanied by strong horizontal and vertical currents, large-amplitude ISWs can propagate a long distance from their generation sites, while keeping their waveform nearly invariant (e.g., Alford et al, 2010; Huang et al, 2014; 2016; Lien et al, 2012; 2014). As a result, they carry the potential to damage offshore engineering structures (Xu et al, 2012) and considerably impact nutrient transport systems (Dong et al, 2015). ISWs in the AS are mainly generated in the western island chain, which includes the Nicobar archipelago and the Andaman Islands (Raju et al, 2019; 2021; Jensen et al, 2020; Magalhaes et al, 2020). The topographic section in the numerical simulation is marked with black lines
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