Oceanography | Vol. 38, No. 2
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SUMMARY AND CONCLUSIONS
The TFO-HYCOM project was a cross-disciplinary investigation
into the modeling of internal tides and high-frequency IGWS
that explored their sensitivity to grid spacing, energy transfer,
and dissipation; the impacts of tidal forcing in ocean simulations
on sound speed structure and acoustic propagation; and the
ability to use DL techniques to replicate tidally forced structure.
The inclusion of tidal forcing in global ocean models improved
the representation of the ocean state and had a direct impact on
sound speed at horizontal scales from kilometers to hundreds of
kilometers and timescales on the order of a few to several hours.
HYCOM simulations run with tides had greater sound-speed
variance that was more consistent with observations. These
impacts were sensitive to vertical and horizontal discretization,
as were the ability of the simulations to resolve IGW interactions
and energy transfer. Further investigations into the impacts of
internal wave modeling choices on acoustic propagation could
also be made by expanding acoustic frequency ranges, looking at
acoustic arrival times, or comparing model results with observa
tional studies. As running models at high resolution is compu
tationally expensive, machine learning techniques may facilitate
predictions of IGW impacts on ocean state in the future.
We have focused on the impacts of IGWs on sound; how
ever, global ocean models are further used by stakeholders with
diverse interests, such as the dispersal of biogeochemical tracers
and biological productivity. As global operational models begin
to include tidal forcing and incorporate finer grid spacing, it is
important to understand how they represent physical processes
and how energy cascades through the internal wave spectrum.
The ability to resolve IGWs in global ocean models has filter-
down effects to several other fields such as ocean biological-
physical interactions and ecosystem modeling. At shallow coastal
locations, where biological productivity and freshwater input are
large, the ability to resolve these IGW processes is important to
understanding ecosystem dynamics. Among the range of their
impacts, IGWs can alter distributions of organisms such as phy
toplankton and chlorophyll, increase or decrease biological pro
ductivity, and alter predator-prey relationships (e.g., Evans et al.,
2008; Lucas et al., 2011; Greer et al, 2014; Garwood et al., 2020).
Having criteria for how IGWs can be resolved in a global model
with a certain discretization will help interpret how well a model
captures IGW energy transfer and the possible effects this may
have on sound speed variability and ecosystem dynamics.
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