CSIRO Marine and Atmospheric Research
Past Seminars

Thursday 15 April 2004, 11.30 am (Tas time)

CSIRO Auditorium, Hobart

Denny Kirwan
University of Delaware, USA

Stirring for the Lagrangian Challenged

In recent years, high-resolution synoptic data and primitive equation models have shown considerable submesoscale structure and fluid transport on scales of the order of 10 kilometres or less. Associated time scales are of the order of a few days in the open ocean to fractions of a tidal cycle in coastal waters. Typical examples are filaments and mushrooms. Carl Eckart (JMR 1949) anticipated this over 5 decades ago in a little remembered paper (Eckart, JMR, 1948). Eckart correctly theorized that fluid deformation, NOT VORTICITY, was responsible for such stirring processes.

Here I provide a micro-review of some basic fluid mechanics concepts responsible for stirring. It should be no surprise that transport on these scales is most effectively viewed from a Lagrangian perspective, even though the synoptic data and the models are Eulerian. The basic concepts are applied to a hierarchy of examples starting with a back-of-the envelope analytic model, then to flow depicted in a data assimilating model of the Gulf of Mexico, and finally to the tidally dominated flow in Monterey Bay.

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