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Turbulence and scaling processes in the ocean
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Self-organized criticality in geophysical turbulence (Invited)
Tuesday 8th @ 1330-1350, Conference Room 4
William D. Smyth* , College of Earth Ocean and Atmospheric Sciences, Oregon State University
James N. Moum, College of Earth Ocean and Atmospheric Sciences, Oregon State University
Jonathan D. Nash, College of Earth Ocean and Atmospheric Sciences, Oregon State University
Presenter Email: smyth@coas.oregonstate.edu |
| Turbulence in forced, stratified, parallel shear flows tends to organize itself so that the mean flow remains close to a stability boundary in parameter space. Roughly, this is the state in which gradients of velocity and buoyancy balance such that the Richardson number equals 1/4. That characteristic suggests self-organized criticality (SOC), a statistical property that has been identified in a range of complex phenomena including earthquakes, forest fires and solar flares. This this presentation explores the relationship between the properties of sheared, stratified turbulence and those of SOC. Self-organization to the critical state is demonstrated in a wide range of cases drawn mostly (but not entirely) from in situ observations of ocean turbulence. Turbulent events in the ocean also exhibit a second property associated with SOC: their sizes follow a power-law distribution indicating self-similarity. These results suggest a new conceptual foundation for the study of geophysical turbulence, an explanation for the mixing efficiency of ocean turbulence and a potential for cross-fertilization with other areas of geophysics. |
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