Generation Mechanism of Upwelling current with "Aoshio" occurrence in summer of 2008 in Ariake Sea

"Aoshio" (the anoxic blue-green turbid water) was first observed in Isahaya Bay, Ariake Sea in August 15, 2008. Field data analysis and numerical experiments were made to clarify the generation mechanism of this "Aoshio" in Isahaya Bay. The field observations showed that the occurrence of "Aoshio" was associated with three characteristic phenomena, the intrusion of high density water (HDW) into the lower layer at neap tide just before the occurrence of "Aoshio", rapid decrease of dissolved oxygen(DO) concentration, leading to the formation of anoxic water during the HDW intrusion and transportation of this anoxic water to the head of Isahaya bay due to south-west wind-induced current, followed by the vertical mixing at around spring tide. Numerical experiments could reproduce these phenomena with high accuracy and the generation mechanism was confirmed by the numerical experiments.