Abstract
Internal waves and vortical mode are ubiquitous in the ocean, providing
a conduit for energy transfer from tides and wind-driven circulation to
fine- and micro-scale turbulence associated with internal-wave breaking
and dissipation. Numerical simulations of a Garrett-Munk internal-wave
field are used to study the interactions between internal waves and
vortical mode, and the generation of turbulent mixing events and
semi-permanent finestructure (vortical mode). Regions of reduced
stratification are found to occupy between ~5% and 25%
of the model domain, depending on the strength of the anomalies.
Decomposition of 3-dimensional model fields into linear internal-wave
and vortical-mode components shows that both influence stratification,
with ~88% of the anomalies due to linear internal waves
and ~40% due to vortical mode, the overlap in
percentiles representing regions that are a combination of the two. The
time evolution of anomalies is examined, from the initial generation to
eventual dissipation. Results further describe the preconditions of
these regions, including their relation to a subcritical Richardson
number and overturning / mixing events as quantified via Thorpe scales
and turbulent dissipation rate.