Enhancing Marine Modelling Accuracy: Recent Developments in the FLEXSEM System

The marine dynamic model at EcoScience,  named FlexSem, model has recently been extended with a set of numerical developments designed to enhance accuracy and stability in realistic marine applications. A new spatial discretization of higher order has been implemented for the horizontal advection of tracers. The method reduces numerical diffusion and improves the representation of sharp gradients, thereby capturing thermocline and pycnocline structures with greater fidelity. In the momentum equations, the surface wind stress parameterization has been revised to include an explicit wind-speed dependency in the drag coefficient formulation. This modification provides a more consistent link between atmospheric forcing and ocean surface response. Furthermore, the agent-based model module has been extended with a diffusive operator, allowing for the simulation of subgrid-scale dispersion in Lagrangian particle tracking. These improvements have been tested across several recent model setups, demonstrating clear benefits to both hydrodynamic and tracer simulations. The enhanced FlexSem system offers a robust and flexible platform for addressing complex marine processes with greater precision.