Coupled Ocean Model

The Ocean module wraps the entire velocity-and-tracer pipeline. It is the high-level entry point for time-stepping a Pelagos simulation.

OceanModel holds:

• the shared ImmersedBoundaryGrid (the single source of grid geometry),
• the Oceananigans HydrostaticFreeSurfaceModel that owns $T$ and $S$ and the prescribed velocity Fields,
• the pre-assembled sparse barotropic streamfunction solver, and
• the pressure Field{Center, Center, Center}.

step_ocean! advances the model one timestep using the pipeline:

1. compute_pressure! — hydrostatic $p$ from $T,S$.
2. solve_baroclinic! — frictional-geostrophic $u, v$ on the C-grid.
3. Barotropic correction — solve ψ at T-points, average to corners, derive divergence-free face transports, replace the FG depth-mean with the ψ-derived barotropic flow.
4. diagnose_w! — vertical velocity from the rigid-lid continuity constraint.
5. Oceananigans.time_step! — advance $T$ and $S$.

The corner-ψ correction makes $w_{\text{top}}$ discretely zero to machine precision, so over one year of integration $T$ and $S$ drift only at the diffusive rate (no spurious source/sink from a non-zero rigid-lid residual).

OceanModel

build_ocean_model(restart_dir; T_restore, S_restore, tau_T, tau_S)

step_ocean!(model, tau_x, tau_y, dt)