Realistic and idealized model output of surface currents and tracers used in frontal maintenance analysis.

Realistic model

./surface_child.zarr directory is a zarr dataset containing a realistic model model based on the Regional Ocean Modeling System \citep[ROMS][]{haidvogel.ea:08} configured with a high-resolution ($\sim$300~m), two-way nested child domain within a coarser ($\sim$1.5~km in the region of nesting) model of the Texas-Louisiana continental shelf, described by \citet{schlichting.ea:23}. The coarser parent model includes the entire coastlines of Louisiana and Texas, and has been run over multiple years of simulated time to examine, for example, interannual variability in harmful algal blooms \citep{thyng.ea:13} along the Texas coast, and the extent of the Mississippi-Atchafalaya plume \citep{zhang.ea:12}. Both models have 30 vertical layers, with resolution focused near the surface. The mean water depth in the nested region is about 50~m. 

Idealized model

./reduced_channel_files contain six resolution cases spanning 200 m to 10 km horizontal resolution. The idealized ROMS model domain for all of them is 100~km by 300~km, with no-slip walls along the short (north/south) boundaries, and re-entrant along the long (east/west) boundaries. Horizontal resolution is varied from 200~m to 10~km. The initial condition is designed to roughly mirror conditions in the Mississippi-Atchafalaya river plume in the northern Gulf of Mexico, which is a location of strong buoyancy forcing, energetic eddy activity, and intense frontal processes \citep[see][]{hetland:17}. The channel has a constant depth of 50~m, with a constant rotation throughout the domain, $f=10^{-4}$~s$^{-1}$. Initial tracer distributions of temperature, $T$, and salinity, $S$, are defined by constant values specifying the vertical and horizontal density gradients, $N^2 = -g \rho_z \rho_0^{-1} = 10^{-4}~\mathrm{s}^{-2}$ and $M^2 = g \rho_y \rho_0^{-1} = 10^{-6}~\mathrm{s}^{-2}$:\begin{align}    T &= T_0 + \frac{N^2}{g \rho_0 \alpha} z\\    S &= S_0 + \frac{M^2}{g \rho_0 \beta} y \quad ,\end{align}where $\alpha$=0.17~$^\circ$C$^{-1}$ and $\beta$=0.76~g$^{-1}$~kg are the linear thermal and haline expansion coefficients in a linearized equation of state, \begin{equation}    \rho = \rho_0 (1 - \alpha T + \beta S) \quad ,\end{equation}where $\rho_0$ is a reference density.A small perturbation to the initial $u$ velocity (in the periodic direction) with a period of 100~km in both the $x$- and $y$-directions and an amplitude of 0.01~m~s$^{-1}$ is applied to supply perturbations on which instabilities can form and grow. The simulations include a weak near inertial (0.9$f$) wind stress in the $x$-direction,\begin{equation}    \label{eqn:roms_wind}    \tau^x = \tau^x_0 \mathrm{sin}(0.9 f\,t) \quad ,\end{equation}to mimic the diurnal winds observed in the northern Gulf of Mexico.