Towards a better representation of ocean dynamics through a better knowledge of multi-scale processes

This theme focuses on the description of multi-scale processes and their interactions, with the aim of better representing ocean dynamics. A first line of research involves studying the interaction of wave phenomena with ocean dynamics at different scales. For example, the influence of the transformation of gravity waves on the dynamics of coastal zones and beach aquifers is the subject of specific studies within the team.

More generally, the interaction between marine circulation and waves is still very poorly represented in models. The study of the circulation induced by these waves, and the reciprocal influence of this circulation on propagation (coupling), is an example of the multi-scale interactions that need to be taken into account when modelling ocean dynamics in coastal areas.

In addition to the objective of understanding and describing ocean dynamics at different scales, understanding these dynamics and representing them correctly in models is a prerequisite for studying marine ecosystems and responding to environmental issues (see Theme 3). Conversely, the feedback of biogeochemistry on ocean dynamics (via the heat balance) is still poorly quantified and poorly represented in models, even though this impact seems far from negligible.

In this context, another of the team's research avenues in this theme is to study the control exerted by these dynamics (and in particular mesoscale and submesoscale dynamics) on energy and matter flows, on the variability of slope currents and coastal-lake exchanges, as well as on the distribution of hydrological and biogeochemical tracers, and potentially the feedback exerted by the latter on the heat balance and ocean dynamics.

To achieve these objectives, an approach combining in situ measurements using appropriate protocols (lagrangian monitoring, etc.) and numerical modelling is being implemented. This approach is applied on a large scale (Mediterranean, Pacific), on a regional scale (North-Western Mediterranean) and to specific ecosystems (i.e. biotope and biocenosis) such as lagoon-reefs, focusing in particular on the influence of terrigenous, cross-reef and coast-large flows, island plumes and upwelling zones.