The potential energy created in the ACC is converted into vigorous nonlinear dynamical structures such as eddies, jets and filaments (Nikurashin et al. 2012). This turbulent energy can power strong air-sea transfers, water-mass formation, transformation, and water properties transport and mixing (Lambaerts et al. 2013).
However, because the observation of such small-scale oceanic structures is very difficult, the exact nature of these processes and their impact are poorly understood, and quantified. This assessment is essential to evaluate, for example, the ocean uptake of climate-relevant tracers such as heat and carbon. Indeed, these oceanic processes drive tracers transport into the ocean (Resplandy et al. 2014). They are also functionally linked to the vertical transfers (i.e., subduction) of water masses and related properties, and they are the rate-limiting step in estimating the ocean sequestration of anthropogenic CO2. The understanding of these processes is therefore capital to accurately estimate the meridional fluxes of mass, heat, fresh-water and biogeochemical tracers.
The project will make it possible (1) to focus on the meso and submeso-scale dynamics, and enhance our understanding and estimates of their role in mixing, and (2) to recover the three-dimensional transport (i.e., lateral, and vertical) of water properties generated by this scale dynamics in this Indian sector of the SO which is characterized by the highest turbulence of the world’s oceans.
Because of their very high variability in space and time, the observations of such processes are challenging, as they cannot be achieved through the classical observational in situ strategy. Within SOCLIM we propose an innovative approach that consists in using the quasi-lagrangian nature of the proposed observing platforms such as profiling floats (Argo and Bio-Argo) and the PolarPod. The deployment of profiling floats will be carried out in selected fine-scale features that will be defined judiciously beforehand by analyses of real-time satellite data. The Lagrangian observations will be associated with measurements provided by others innovative instruments (Seasoar, UCTD, gliders, wave gliders) deployed in collaboration with our foreign partners. These field data, in combination with satellite products, will give us the ability to observe for relatively long spans of time the selected ocean fine-scale structures, and the evolution of their dynamical context as well as that of their properties. These innovative observations will enable us to understand the role of the small–scale ocean dynamics in mixing and 3D transfers of properties in the upper 2000 m of the ocean.