Monday 03 Dec 2018Nonlinear resonance in the formation of layers in stably stratified fluids

Dr. Paul Burns - University of Exeter

Laver LT3 14:30-16:30

The overarching aim of this work is to develop a new theory of wave-mean flow interaction for continuum and fluid mechanics. The new theory relies on frequency averaging rather than averaging fields across space or time. We focus on the phenomena of layer formation in the upper Arctic Ocean, which prevents the ice packs from melting by limiting vertical heat transfers. A number of outstanding questions remain, such as why are the layers so long-lived, and could the layers change under a warming climate? We seek to describe the low-frequency layer structure (the spatially observed shear-layer structure) using the nonlinear resonance of internal gravity waves. We first explore a more idealised laboratory experiment that can be simplified so that we can use analytical analysis tools. Numerical simulations of the lab experiment show the layer formation, with and without an external force, and our initial analysis associates the layers with the waves. Future work will complete the resonance analysis and incorporate observations from the Beaufort Gyre Exploration program.

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