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Australia: The Land Where Time Began |
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Southern Ocean –
Rates and Mechanisms of Turbulent Dissipation and Mixing – the Diapycnal
and Isopycnal Mixing Experiment (DIMES) In this study the authors1 used
microstructure and finestructure data that had been collected as part of
the Diapycnal and Isopycnal Mixing Experiment in the
Southern Ocean
(DIMES) to analyse the spatial distribution of turbulent dissipation
rates and internal wavefront characteristics across 2 contrasting
regimes of the
Antarctic Circumpolar Current (ACC).
The results indicated that
mid-depth turbulent dissipation rates increase
O(1 x 10-10 W kg-1
in the Southeast Pacific to
O(1 x 1—9 W kg-1)
in the Scotia Sea, which typically reach 3 x 10-9 W kg-1
within a kilometre of the seabed. It has been found that enhanced levels
of turbulent mixing are associated with near-bottom flows that are
strong, rough topography, and regions where the internal wavefield has
enhanced energy, a less-inertial frequency content and a dominance of
energy that is propagating upwards. It is strongly suggested by these
results that a major role in determining the spatial distribution of
turbulent dissipation in the ACC is played by the internal waves that
are bottom-generated. Wave radiation theory is used to calculate the
energy flux that is associated with the generation process of bottom
internal wave generation, which has been found to vary between 0.8 mW m-2
in the Southeast Pacific and 14 mW m-2 in the Scotia Sea. Of
this energy 10%-30% is typically found to dissipate within 1 km of the
seabed. Comparison between turbulent dissipation rates that have been
inferred from finestructure parameterisations and estimates derived from
microstructure it is suggested there is a significant departure from
wave-wave interaction physics in the near-field of wave generation
sites.
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Author: M.H.Monroe Email: admin@austhrutime.com Sources & Further reading |