Controlling the open ocean forcing of baroclinic coastal jets with a 4D-var method

An optimal control approach was carried out to investigate the influence of perturbations of baroclinic coastal jets which are located upstream of the observation site. Two academic numerical experiments were considered: the intrusion of the buoyancy anomaly within an established density current along a straight coast (experiments A), and the interaction of a coastal current with a shelf topography (experiments B). We explored the sensitivity of the forcing retrieval to the spatial distribution of observations (experiments A) and to the temporal sampling of the forcing (experiments B), using a 4D-var formalism. The sensitivity of numerical simulations is discussed in the framework of analytical solutions. The results provide insight into how observational network and data assimilation method would impact the realistic modelling of coastal jets and the shelf slope exchanges.