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I am a postdoc at California Institute of Technology, in the ocean physics group led by Jörn Callies. My current work focuses on the study of the spectral content of Sea Surface Height in the context of the upcoming SWOT mission. This work is funded by NASA and aims at giving more understanding on the dynamics of surface marine currents.

Study of surface oceanic turbulence

We know that oceanic currents with horizontal scales smaller than 100 km are a major part of the oceanic circulation. For now, we do not have a global characterization of these flows and their impact because of the crude resolution of satellite altimetry. The Surface Water and Ocean Topography (SWOT) mission, scheduled for launch in late 2022, is expected to lower the noise floor and thus allow to characterize finner scales. However, the sea surface height field at these fine scales is expected to be a combination of geostrophic (balanced) turbulence and internal gravity waves.

My work as a postdoc is to give new keys in the understanding of this balanced turbulence, to allow to better disentangle signals when the satellite fly over the ocean. To do so, I use a combination of state-of-the-art in situ data and numerical simulations. This work is done in collaboration to people from Jet Propulsion Laboratory and SCRIPPS Institution of Oceanography.

Vortices in the Arabian Sea

During my PhD, I studid the dynamics of meso- and submeso-scale coherent structures in the Arabian Sea. This work was supervised by Xavier Carton and Thomas Meunier, in strong collaboration with Pierre L'Hégaret and Mathieu Morvan. It took place at LOPS in Brest thanks to DGA's funding.

A mesoscale eddy representative of Arabian Sea eddies after its destabilization. The image shows its surface relative vorticity, from the outputs of an high resolution numerical simulation.

In the Arabian Sea, vortices of horizontal size between 10 and 100 km have a greater impact on the circulation than the large-scale circulation. In this work, I studied the three-dimensional structure of mesoscale eddies in the Arabian Sea, through the joint use of altimetry and in situ measurements. I described the lifecycle of these eddies using numerical simulations, under the assumption that they are isolated from the rest of the dynamics. For these simulations, a composite vortex extracted from in situ data is used as an initial condition. The vortex stability was shown to be determinent for the vortex lifetime and the generation of submesoscale structures at the surface.

The deep submesoscale vortex measured in the Arabian Sea during the Physindien 2019 experiment. (a) Localisation of the measurement, (b) relative vorticity at 600 m depth, and the associated ship-measured currents.

During this thesis, I also studied the interaction between eddies and the western boundaries of ocean basins, and relate these results to the measurement of a cyclonic submesoscale vortex performed during the Physindien 2019 experiment. This latter was the first deep cyclonic submesoscale vortex measured at such a resolution. Finally, I studied one part of the eddy interactions that occur in the Arabian Sea: mergers. One of the main results was that the comparison between the distance for which two eddies in the ocean merge, and the critical merging distance obtained from idealized studies of two eddies isolated on an f-plane omits the main parameters involved in merging: the ambient turbulent field and the β-effect.

Beside the focus made on the Arabian Sea for this PhD Thesis work, my general interest in oceanography is related to these structures, vortices, because we know that they play a major role in the global ocean dynamics. I tried to relate problematics to the study of vortices in an idealized way, as it allows to more finely describe the processes at play at scales of the order of 100 km.

Is the Earth flat by the way?

Nope, at least if we trust state-of-the-art numerical simulations: click here, not here.