Mesoscale eddies are ubiquitous in the ocean, and typically exhibit different characteristics to their surroundings, allowing them to transport properties such as heat, salt and carbon around the ocean. This takes place everywhere in the world’s ocean and at all latitude bands. Most of mesoscale eddies energy is generated by instabilities of the mean flow, and by air-sea interactions. Mesoscale dynamics can feed energy and momentum back into the mean flow and help drive the deep ocean circulation. Their suspected importance in transporting and mixing water properties as they propagate in the ocean, play a significant role in the global budgets of these tracers and climate. Increasing evidences point out at intense air-sea interaction at smaller scale than synoptical, especially in the extratropics that can strongly affect the Troposphere. However we do not have yet neither a global quantitative assessments nor a theoretical understanding of these processes. We will present new results from a recently developed eddy-atlas (ToEddies) that includes eddies merging and splitting. In particular, we will discuss properties of Agulhas Rings in the South Atlantic derived from satellite altimetry and the colocalization of these eddies with Argo floats. Our results show that these eddies are, in the South Atlantic, associated with strong thermal and haline anomalies. These are essentially due to Mode Waters (Agulhas Rings Mode Water: ARMW) formed in the core of the rings in the southeastern Cape Basin, just west of the Agulhas Retroflection, after intense air-sea interactions that can last for more than an entire season. These eddies are then advected in the South Atlantic and are responsible of an important flux of heat and salt into this basin (Laxenaire et al. 2018a,b). We corroborate such findings with full depth hydrography of selected eddies and very high-resolution modelling studies.

Internal tides (ITs) in the Indonesian seas were largely investigated and hotspots of intensified mixing identified in the straits in regional models and observations. Both of them indicate strong mixing up to 10⁻⁴cm/s even close to the surface and show that tides at spring-neap cycle cool by 0.2°C the surface water at ITs’ generation sites.These findings supported the idea of strong and surfaced mixing capable of providing cold and nutrient-rich water favorable for the whole ecosystem. However, it has never been assessed through an ad-hoc study. Our aim is to provide a quantification of ITs impact on chlorophyll-a through a coupled model, whose physical part was validated against the INDOMIX data in precedent studies and the biogeochemical part is compared to in-situ samples and satellite products. In particular, explicit tides’ inclusion within the model improves the representation of chlorophyll and of the analyzed nutrients. Results from harmonic analysis of chlorophyll-a demonstrate that tidal forcing modify spring/neap tides’ variability on the regions of maximum concentration in correspondence to ITs’ génération areas and to plateau sites where barotropic tides produce large friction reaching the surface. The adoption of measured vertical diffusivities explains the biogéochemical tracers’ transformation within the Halmahera Sea and used to estimate the nutrients’ turbulent flux, with an associated increase in new production of ~25% of the total and a growth in mean chlorophyll of ~30%. Hence, we confirm the key role of ITs in shaping vertical distribution and variability of chlorophyll as well as nutrients in the maritime continent.