Rapid oscillation of sediment transport between the Bohai Sea and the Yellow Sea induced by Typhoon Lekima (2019)

Abstract

Amidst the continued northward migration of tropical cyclones in the context of global warming, mid and high latitudes marginal seas, like the East China Seas in the northwest Pacific Ocean, are increasingly attacked by tropical cyclones. As such, it is crucial to pay more attention to the impact of tropical cyclones on these marginal seas. To address this issue, we utilized a well-calibrated FVCOM model to study the effects of Typhoon Lekima (2019) on sediment transport between the Bohai Sea and the Yellow Sea. The results showed that during Typhoon Lekima's passage, sediment dynamics in the Bohai and Yellow seas were significantly altered. During the first two days of Typhoon Lekima's arrival, the water and sediment transport pattern rapidly changed from normal summer conditions to a strong inflow into the Bohai Sea, which increased water levels in the southwest Bohai Sea. As Typhoon Lekima weakened, the barotropic effect drove the water outflow from the Bohai Sea to the Yellow Sea. Strong bottom shear stress induced by the high-energy waves introduced strong sediment resuspension, which led to massive sediment escaping out of the Bohai Sea via the outflow during the weakening period of Typhoon Lekima. After two days following Typhoon Lekima's passage, the transport pattern gradually returned to normal summer conditions. The study revealed that the net sediment load from the Bohai Sea to the Yellow Sea during Typhoon Lekima was approximately 0.84 Mt., which is equivalent to 5–33% of the annual flux. The study highlights the critical role of extreme weather events in sediment dynamics and provides important insights into the impacts of typhoon on source-to-sink process in mid and high latitude marginal seas.