Abnormal reverse intrusion of the Kuroshio Branch Current induced by super typhoon soudelor

Abstract

The Kuroshio Current has a considerable impact on the environmental characteristics and dynamic of the East China Sea (ECS). On the ECS continental shelf within the study area of (124°E-126°E, 25°N-27°N), the Kuroshio Branch Current (KBC) exists in a stable state and flows towards the main Kuroshio axis. The significant difference in potential vorticity is on both sides of the Kuroshio main axis, which makes it difficult for the seawater on the right side of the Kuroshio main axis to intrude the ECS continental shelf. Based on Argo data, satellite data and reanalysis data, an abnormal reverse intrusion of the KBC was observed during the passage of super typhoon Soudelor in 2015. The mean reverse volume transport during the period of Soudelor reached about 0.56 Sv, and the daily mean volume transport on August 9 reached up to 1.29 Sv. Soudelor inputted additional positive potential vorticity fluxes on the right side of the Kuroshio main axis and counteracted the significant potential vorticity difference on both sides of the Kuroshio main axis, which provided a channel for the apparently reverse enhanced ocean current. The significant Ekman downwelling and changes of the upper ocean stratification also promoted the reverse intrusion of KBC. This study offers new insights into the influence of typhoons on the intrusion of the Kuroshio onto the ECS continental shelf.