The Environmental Fluid Dynamics Lecture Series Presents a Seminar

Professor Jae Hak Lee, Ph.D

Ocean Circulation and Climate Research Division Korea Institute of Ocean Science And Technology Tuesday, April 22 Dean’s Boardroom, 258 Fitzpatrick 11am-12noon Turbulence and Mixing: A controller of Traces Distributions In the East China Sea

Vertical mixing in the ocean is a key process for the diapycnal exchange of biogeochemical material s between different layers. The data collected from observations of microstructure profiler (MSP) in the East China Sea (ECS) in the summertime show high turbulent energy dissipation rates near the bottom and within the thermocline, with typical value of O(10 -7 Wkg -1 ) and occasionally close to 10 -6 Wkg -1 . Corresponding vertical eddy diffusivities reach to 10 -2 m 2 s -1 . High values of dissipation rate and vertical diffusivity are consistent with high turbidity or enhanced Chlorophyll a concentration. I n addition, the data from repeated MSP castings and vessel mounted Acoustic Doppler Current Pro filer (ADCP) measurements show good correlation between the enhanced bottom mixed layer and the phase of tidal current indicating that vertical mixing near the bottom occurs mainly due to the t idal stirring. During internal wave episodes or strong wind events, high-frequency fluctuations of all components of the velocity occur for almost entire water column suggesting the possibility of verti cal transport of suspended materials across the pycnocline. This implies that near bottom mixing a nd internal mixing within the thermocline are key physical processes to control biogeochemical trac ers, e.g. the subsurface Chlorophyll maximum layer, in the ECS shelf.