OCEANOGRAPHY AND ATMOSPHERIC SCIENCES SEMINAR SERIES 2005

Stirring in the East Australia Current and Tasman Sea

Speaker:Dr. Darryn Waugh
Department of Earth and Planetary Sciences
Johns Hopkins University

Wednesday March 23rd
4 p.m.-5 p.m.
Room RC-4082
Level 4 Red Centre Building

The stirring in the EAC and Tasman Sea is examined using surface currents derived from satellite altimeter measurements. Calculations of the distribution of finite-time Lyapunov exponents (FTLEs)indicate that the stirring in this region is not uniform and there is a wide range of stirring rates.These variations occur at both small (~10 km) and large (~1000 km) scales, and in both cases are linked to dynamical
features of the flow. The small scale variations are related to the characteristics of coherent vortex structures, and there are low FTLES inside vortices and filaments of high FTLEs in strain dominated regions surrounding these vortices.

Regional variations in the stirring are closely related to variations in mesoscale activity and eddy kinetic energy (EKE). There is in fact a a compact relationship between the mean FTLEs and EKE, raising the possibility of using the easily-calculated EKE to estimate the stirring.This possibility is even more intriguing as the FTLE distributions can be approximated by disstributions that depend on the mean alone.