Behavior of the Warm Water Filament Touched with the South Coast of Kyushu

Abstract

The warm ocean water filaments generated periodically from the meandering Kuroshio Current at the East China Sea influences to the south coast of Kyushu such as the intermittent warm ocean water intrusion into Kagoshima bay well known as Kyucho phenomenon.
From the observation with satellite-derived sea surface temperature (SST), the warm water intrusion not only into Kagoshima Bay but also offshore of Fukiage seashore are found. The intrusions occur when the warm water comes into touch with the bay water at the mouth of the bay. In addition to the warm water intrusion, SST image shows the cold-water mass emanating at the coast of Osumi peninsula. While warm water passes through the Osumi strait, it is found that the region of the cold-water is formed along the coast of Osumi peninsula. Then the numerical analysis using a multi-leveled finite difference method (FDM) is performed for the purpose to investigate these phenomena. It is found from the numerical analysis :
(1) The intrusions occur when the warm water comes into touch with the mouth of Kagoshima bay or the east edge of Noma cape.
(2) Intruding speed and thickness of the warm water into Kagoshima bay show the same tendency as the existing report from buoy robot data and the simulation of a limited domain.
(3) The cold-water mass emanated at the coast of Osumi peninsula forms vortex and stagnation region, and the calculated vertical velocity structure shows anticlockwise circulation at the mouth of Kagoshima Bay.