Abstract
The mixed layer plays a crucial role as an entry or exit point for heat,
salt, momentum and nutrients from the surface to the deep ocean. We
propose here a generic framework to evaluate the mixed layer depth (MLD)
dynamics across a wide range of forcings and preconditioning conditions.
To do so, we propose to use a physically-based parameter space formed by
two dimensionless numbers: $\lambda_s$ the relative
contribution of the buoyancy flux and the wind in the surface layer, and
the Richardson number $R_h$ which characterizes the stability of the
water column at the mixed layer base. Four MLD dynamics regimes
(“restratification”, “stable”, “deepening” and “strong
deepening”) are defined based on the values of the normalized temporal
evolution of the MLD. We show the robustness and the predictive skill of
the parameter space in a context of 1D simulations by showing that to a
given ($\lambda_s$, $R_h$) corresponds a
predictable MLD dynamics regime. Finally, we present two applications
showing how the parameter space can be used with 3D ocean realistic
models. We discuss the impact of the horizontal resolution (1°, 1/12° or
1/60°) and the Gent McWilliams parameterization on the MLD dynamics
regimes.