Variation of Internal Solitary Wave Propagation Induced by the Typical Oceanic Circulation Patterns in the Northern South China Sea Deep Basin

Large-scale circulations are quite typical processes in the northern South China Sea (SCS) deep basin, yet their impacts on the variation of internal solitary waves (ISWs) remains poorly understood. We, here, focus on impacts of the upstream SCS western boundary current (SCSwbc) and three typical circulation patterns associated with different Kuroshio intruding paths on ISW propagation in this region. We show that the ISW modulated by the upstream SCSwbc gets a speedup, which is comparable to that induced by Coriolis effect, while the ISW amplitude shows an obvious reduction. Statistically, there is approximately one-third time of 23 years (1993-2015) when circulation-induced changes of wave speed exceed Coriolis-induced changes. Specifically, the looping circulation pattern has the highest impact on significant speedup and amplitude reduction among the three patterns, while the leaping pattern has the lowest impact. These differences in wave characteristics caused by different circulation patterns result from the wave scattering, focusing and Doppler effects.

Automated summary

Large-scale circulations play a crucial role in influencing the variation of internal solitary waves in the northern South China Sea deep basin. The upstream South China Sea western boundary current and different circulation patterns associated with Kuroshio intruding paths have significant impacts on wave speed and amplitude, primarily through wave scattering, focusing, and Doppler effects.