Estimation de la dynamique océanique de surface fine échelle à l’ère de l’altimétrie large fauchée (SWOT)

SWOT provides an unprecedented 2D view of surface dynamics at scales below 100 km, but uncertainties remain regarding the nature of this dynamics, the validity of geostrophy, the contribution of errors, and its added value compared to classical altimetry. This thesis proposes an original approach that reconstructs the instantaneous horizontal conservation of surface momentum by combining SWOT data, drifter trajectories, and atmospheric reanalyses coupled with an Ekman model. A dedicated statistical method quantifies the variance explained by each term, evaluates errors, and assesses the relative importance of different dynamical balances (geostrophic, inertial, cyclogeostrophic. . . ). Two reconstructions — global (2010–2020) and Mediterranean (2023) — confirm the dominance of geostrophy, while inertial and Ekman contributions can approach the geostrophic variance. In the Mediterranean, a new variational algorithm for smoothing buoy trajectories was applied, and the 2 km de-noised SWOT product provides the best noise/variance trade-off. The analysis also reveals cyclogeostrophic signatures in mesoscale eddies.