  Measurements of the carbon-to-oxygen (C/O) ratios of exoplanet atmospheres
can reveal details about their formation and evolution. Recently,
high-resolution cross-correlation analysis has emerged as a method of precisely
constraining the C/O ratios of hot Jupiter atmospheres. We present two transits
of the ultra-hot Jupiter WASP-76b observed between 1.4-2.4 $\mu$m with
Gemini-S/IGRINS. We detected the presence of H$_{2}$O, CO, and OH at
signal-to-noise ratios of 6.93, 6.47, and 3.90, respectively. We performed two
retrievals on this data set. A free retrieval for abundances of these three
species retrieved a volatile metallicity of $\left[\frac{\mathrm{C}+\mathrm{O}}
{\mathrm{H}}\right]=-0.70^{+1.27}_{-0.93}$, consistent with the stellar value,
and a super-solar carbon-to-oxygen ratio of C/O$=0.80^{+0.07}_{-0.11}$. We also
ran a chemically self-consistent grid retrieval, which agreed with the free
retrieval within $1\sigma$ but favored a slightly more sub-stellar metallicity
and solar C/O ratio ($\left[\frac{\mathrm{C}+\mathrm{O}}
{\mathrm{H}}\right]=-0.74^{+0.23}_{-0.17}$ and C/O$=0.59^{+0.13}_{-0.14}$). A
variety of formation pathways may explain the composition of WASP-76b.
Additionally, we found systemic ($V_{sys}$) and Keplerian ($K_{p}$) velocity
offsets which were broadly consistent with expectations from 3D general
circulation models of WASP-76b, with the exception of a redshifted $V_{sys}$
for H$_{2}$O. Future observations to measure the phase-dependent velocity
offsets and limb differences at high resolution on WASP-76b will be necessary
to understand the H$_{2}$O velocity shift. Finally, we find that the population
of exoplanets with precisely constrained C/O ratios generally trends toward
super-solar C/O ratios. More results from high-resolution observations or JWST
will serve to further elucidate any population-level trends.
