Abstract Oblique interactions between internal solitary waves (ISWs) in the ocean have been frequently recorded by satellite images, nonetheless, only a limited number of studies concentrate on these phenomena, which found that both the Earth's rotation and varying topography are important factors for the underlining wave dynamics. However, the effects of rotation at different latitudes and furthermore, their combined effects with the shoaling topography are still unclear. Thus, the aim of this paper is to investigate these combined effects on oblique ISW wave‐wave interactions. Referring to observed obliquely interacting patterns, three scenarios initiated by two ISWs posing a V shape are explored using the variable‐coefficient Kadomtsev‐Petviashvili (KP) equation under the circumstance of continuous stratification and idealized shoaling topography. In all three experiments, rotation alone disintegrates the coherent waveforms and suppresses the emergence of a Mach stem (a wave generated at the interaction zone, characterized by the maximum of four‐fold initial waves). When shoaling topography is also included, which increases the nonlinearity leading to a competition with dispersion induced by rotation, and the result is a magnification of wave amplitudes and emergence of additional trailing waves. The combined effect of these two factors modulates the birth and subsequent development of the Mach stem, alters the post‐interaction patterns and determines the emergence of a nascent KdV‐like undular bore, which plausibly explains the discrepancies between previous theoretical results (when the combined effect is not considered) and the measured horizontal surface signatures for ISW wave‐wave interactions.
Plain Language Summary Internal solitary waves (ISWs) are large‐amplitude internal waves featuring a robust hump shape and they are ubiquitous in the World's oceans. ISWs originating from different sources can propagate long distances in different directions, creating a high possibility for oblique interactions, which, indeed, have been frequently observed in satellite images. However, these three‐dimensional phenomena are rarely studied, partly owing to the difficulty of collecting in situ data with appropriate spatial and temporal coverage. One of the remarkable features of wave resonance between oblique ISWs is the Mach stem wave which is characterized by an up to four‐fold amplitude enhancement. Nevertheless, the combined effect of shoaling topography and Earth's rotation on oblique ISW wave‐wave interactions is still unclear. In this paper, it is found that the post‐interaction waveforms, the birth and development of the Mach stem, and the emergence of nascent wave packets akin to undular bores are influenced by this combined effect.
Key Points The Earth's rotation disintegrates the coherent wave packets and suppresses nonlinear oblique wave resonance The combined effect of topography and rotation modulates the birth and development of Mach stem This combined effect alters the post‐interaction waveforms and leads to the emergence of a nascent undular bore