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. Plain Language Summary: Oceanic internal solitary waves (ISWs) are ubiquitous features across the world's oceans. Most of previous studies during the past decades were devoted to the impact of the tidal forcing or Coriolis force on these waves, but the impact of typical oceanic circulations, primarily driven by wind forcing, was still not well understood. Here, by modeling and statistical analyses, we illustrate the impacts of the upstream branch of South China Sea (SCS) western boundary current and three typical oceanic circulation patterns associated with different paths of Kuroshio intrusion on the propagation of ISW fronts in the northern SCS deep basin. We show that the speedup of ISW induced by the upstream branch of western boundary current is comparable to that induced by Coriolis effect, while the amplitude shows an obvious reduction. The oceanic circulation‐induced relative change of speed has a quasi‐Gaussian behavior, which is similar to that of large‐scale oceanic turbulent motions retrieved from satellite altimetry measurements. Also, the looping circulation pattern has the largest probability to cause significant speedup of ISW propagation, while the leaping pattern displays the lowest probability. These differences in wave characteristics caused by different circulation patterns result from the wave scattering, focusing and Doppler effects. Key Points: The speedup of internal solitary wave (ISW) induced by upstream South China Sea western boundary current (SCSwbc) is comparable to that induced by Coriolis force, while the amplitude shows obvious reductionCirculation under Kuroshio intrusion of looping path has high impact on wave characteristics, while that of leaping path has low impactThere is approximately one‐third time of 23 years (1993–2015) when circulation‐induced changes of wave speed exceed Coriolis‐induced changes [ABSTRACT FROM AUTHOR]