Vertical Mixing Enhanced by Artificial Mound in the Shallow Ocean

An artificial mound was settled at the shallow ocean of 33deg 28\´ 42\´\´ N and 129deg 25\´ 29" E for the purpose that it enhances vertical mixing and consequently carries the nutrients from the bottom to surface layer aiming at rich primary production. In order to understand the flow characteristics near the mound, vertical shear was measured by two kinds of ADCPs, one was loaded on a moving boat and the other was settled at the sea bottom. Stratification was also measured regularly by a CTD. Energy dissipation rate and diapycnal diffusivity were estimated from vertical shear and stratification. Spatial and temporal distributions of diapycnal diffusivity were obtained from moving and fixed ADCPs, respectively. The estimated values give an evidence for the enhancement of vertical mixing near the mound in the full spring tide, while little enhancement was found in the other tidal timings. It was confirmed that the tidal currents plays a significant role on the turbulent dissipation; namely, the estimated diapycnal diffusivity was well correlated to the tidal speed.