  Internal tide generation and breaking play a primary role in the vertical
transport and mixing of heat and other properties in the ocean interior,
thereby influencing climate regulation. Additionally, internal tides increase
sound speed variability in the ocean, consequently impacting underwater
acoustic propagation. With advancements in large-scale ocean modeling
capabilities, it is essential to assess the impact of higher model resolutions
(horizontal and vertical) in representing internal tides. This study
investigates the influence of vertical resolution on internal tide energetics
and its subsequent effects on underwater acoustic propagation in the HYbrid
Coordinate Ocean Model (HYCOM). An idealized configuration with a ridge, forced
only by semidiurnal tides and having 1-km horizontal grid-spacing, is used to
test two different vertical-grid discretizations, defined based on the
zero-crossings of horizontal velocity eigenfunctions, with seven distinct
numbers of isopycnal layers, ranging from 8 to 128. Analyses reveal that
increasing the number of layers up to 48 increases barotropic-to-baroclinic
tidal conversion, available potential energy, and vertical kinetic energy,
reaching equilibrium afterwards with higher layer counts. Vertical shear
exhibits a similar pattern but converging at 96 layers. Simulations with at
least 48 layers fully resolve the available potential energy contained in the
3rd to 8th tidal baroclinic modes. Finally, sound speed variability and
acoustic parameters differ for simulations with less than 48 layers. Therefore,
the study concludes that a minimum vertical resolution (48 layers in this case)
is required in isopycnal models to minimize the impact on internal tide
properties and associated underwater acoustic propagation.
