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Marginal instability and deep cycle turbulence in the eastern equatorial Pacific Ocean

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Title Marginal instability and deep cycle turbulence in the eastern equatorial Pacific Ocean
Names Smyth, W. D. (creator)
Moum, J. N. (creator)
Date Issued 2013-12-08 (iso8601)
Note This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1944-8007.
Abstract Deep cycle mixing in the cold tongue of the equatorial
Pacific Ocean is associated with a mean flow regime
in which the gradient Richardson number Ri (a ratio of
stratification to shear that affects the evolution of turbulence)
fluctuates about a critical value near 1/4. This is the state
of marginal instability (MI), a stable equilibrium between
forcing by the trade winds (which works to reduce Ri) and
turbulence (which works to increase Ri). Besides providing
insight into the physics of deep cycle turbulence, MI is easily
recognized in moored records of currents and density, and
may therefore provide a valuable indicator of turbulence
in historical data where direct turbulence measurements
were not made. In this initial study, the seasonal cycle of
MI is described. MI is present for 9 months of the year
but disappears in March, April, and May, consistent with
the recently discovered springtime minimum of equatorial
turbulence.
Genre Article
Topic turbulence
Identifier Smyth, W. D., and J. N. Moum (2013), Marginal instability and deep cycle turbulence in the eastern equatorial Pacific Ocean, Geophysical Research Letters, 40, 6181–6185. doi:10.1002/2013GL058403

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