An investigation into density and velocity
fluctuations in the oceanic thermocline is
presented. Two kinds of numerical simulation are
reported. In the first, an attempt is made to capture
the transition from breaking internal waves
to the small-scale turbulence they generate.
The large-scale forcing of the flow is modelled by
a continual forcing of a large-scale standing
internal-wave. The subgrid scales are modelled by
an isotropic eddy viscosity with a small-scale cutoff
in the inertial range. Evidence is presented for
a transition in the energy spectra from the
anisotropic buoyancy range to the small-scale
isotropic inertial range. Density structures
that form during wave breaking are analyzed and
regions of mixing associated with the breaking
events are visualized. In the second kind of
simulation, internal-wave packets are followed as
they propagate through the thermocline. It is
found that the breaking of crests within the
packet can lead to overturning events on the
scale observed in the ocean, and the
subsequent turbulence can form a continuous
wake. Some of the difficulties
of using analytical closure theory to represent these
phenomena will be discussed.
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