Spatiotemporal structures of tidal currents and upwelling around the Hachiri-ga-se marine hill in the southwestern Japan Sea

Abstract

Spatiotemporal structures of tidal and mean currents in August 2008 and May 2010 were estimated by shipboard ADCP data around the Hachiri-ga-se marine hill in the southwestern Japan Sea. The time variations of the tidal currents were quite similar both in August and May. The vertical structure of tidal and mean currents in August was more baroclinic than that in May. Upwelling region moved when the tidal current varied with time. The upwellings occurred in the convergence region when the horizontal current flowed across the marine hill. The upwellings in August and May mainly occurred at the central and northwestern parts of the Hachiri-ga-se marine hill, respectively. In the case of May 2010, the thermocline was lifted about 10 m near the top of hill along the cross-hill temperature section. It is considered that many zooplankton measured by quantitative echosounder were distributed in the upwelling region.