Some Aspects of Turbulence Role in Oceanic Currents - Selected Topics of Computational and Experimental Fluid Mechanics - page 181

to high mixing levels. The “fine-structure” estimates, the microstructure measure-
ments and the tracer released experiment method showed high levels of diapycnal
mixing (Ledwell et al. 2011 ; St. Laurent et al. 2012 ;Watsonetal. 2013 ), i.e. about
one order of magnitude higher than the background values.

4 Summary

The importance of mapping the hotspots regions for diapycnal mixing is an ongoing
worldwide effort, which has shown evidence of regions with high turbulent diffusiv-
ity values. The DIMES experiment belongs to one of those efforts since encompass
The Circumpolar Current, which plays an important role in modulating the world
climate. The measurements presented in this paper show a relatively good agree-
ment among them; however many more experiments to validate the methods are
needed. Specifically on regions that are shear dominated, strain dominated or both.
The “fine-structure” method is one of the cheapest and there are by far many more
datasets spanning large areas of the ocean including sections that are visited con-
tinuously. For example, the currently ongoing project CLIVAR (Climate Variability
and Predictability), which among many other measurements performs LADCP/CTD
measurements on routinely basis. Kunze et al. ( 2006 ) performed one of the most ex-
haustive estimates of diapycnal mixing using some of those databases. The downside
of this method is the low effective vertical resolution usually given by the LADCP
∼ ∼

1mm. The tracer experiment
provides a very accurate estimation with the downside that is only a small region
above and below the injection point. However, one of the beauties of this method is
the possibility of estimating the horizontal and vertical turbulent diffusivity. There
is until now a continuous effort on improving the methods. Additionally, there are
other methods that were not mentioned here, which complement enormously the
effort of mapping the world turbulent diapycnal mixing. The methods mentioned
above are usually good for the ocean interior leaving the coastal regions abandoned.
The mixing processes around coastal regions is very important regionally and also
needs a proper parametrization for the correct implementation of regional models.

50mm, in contrast with the microstructure profiler

Acknowledgments The author would like to thank Dr. AbrahamMedina Ovando for the invitation
to the Enzo Levi Symposium, also A.M. Thurnherr for great and fruitful discussions and sharing a
lot of his knowledge on LADCP/CTD. The author would like to thank as well L. St Laurent and
J. Toole for fruitful conversations during the cruises and outside. Special thanks go to the PIs Lauren
Mullineaux and Jim Ledwell for their invitations to collaborate on LADDER and DIMES projects.
Funding for the LADDER project and the microstructure add-on was provided by the National
Science Foundation under grants OCE-0728766, OCE-0425361 andOCE-0424953. DIMES project
was supported by the U.S. National Science Foundation and by the Natural Environment Research
Council of the United Kingdom.