Coronavirus Information for the UC San Diego Community

Our leaders are working closely with federal and state officials to ensure your ongoing safety at the university. Stay up to date with the latest developments. Learn more.

CASPO Seminar - Takashi Ijichi (WHOI)

10/24/2018 - 3:30pm
NH 101
Event Description: 

Speaker : Takashi Ijichi (WHOI)

Title: Observed variations in turbulent mixing efficiency in the deep ocean

Abstract: Recent progress in direct numerical simulations (DNSs) of stratified turbulent flows has led to increasing attention to the validity of the constancy of the dissipation flux coefficient Γ in the Osborn’s eddy diffusivity model. Motivated by lack of observational estimates of Γ, particularly under weakly stratified deep-ocean conditions, this study estimates Γ using deep microstructure profiles collected in various regions of the North Pacific and Southern Oceans. It is shown that Γ is not constant but varies significantly with the Ozmidov/Thorpe scale ratio Rot in a fashion similar to that obtained by previous DNS studies. Efficient mixing events with Γ ~ O(1) and Rot ~ O(0.1) tend to be frequently observed in the deep ocean (i.e., weak stratification), while moderate mixing events with Γ ~  O(0.1) and Rot ~ O(1) tend to be observed in the upper ocean (i.e., strong stratification). The observed negative relationship between Γ and Rot is consistent with a simple scaling that can be derived from classical turbulence theories. In contrast, the observed results exhibit no definite relationships between Γ and the buoyancy Reynolds number Reb, although Reb has long been thought to be another key parameter that controls Γ.

For more information on this event, contact: 
Alice Ren
Event Calendar: