Aurelien Ponte (Ifremer, France); Pierre Garreau (Ifremer, France); Jean-François Piolle (Ifremer, France); Gwenael Caer (Ifremer, France); Cyril Germineaud (CNES, France)

If SWOT provides for the first time sea level observations at scales below 100km, several outstanding questions remain: what is the dynamics of oceanic surface motions at the newly resolved scales, in particular how well does geostrophy hold ? What is the content of dynamical signals (e.g. related to the ocean circulation) versus non-dynamical signals (e.g. instrumental noise, geophysical noise, …) in the various products proposed (e.g. calibrated/filtered, unsmoothed, 2km)? What is the added value of SWOT compared to mainstream altimetric products (e.g. L4 AVISO)?

We provide partial answers to these questions by collocating SWOT observations with surface drifter trajectories and wind reanalysis. This enables the reconstruction of instantaneous surface momentum balances. A novel methodology opens the door for the estimation of balanced vs unbalanced/noise contributions to the momentum closure for each dynamical term (e.g. inertial and Coriolis accelerations, pressure gradient, turbulent stress divergence). We conduct targeted statistical conditioning, sensitivities to filtering (temporal/spatial) and data products in order to partially answer the questions listed above. The core of the analysis is focused on the Western Mediterranean sea and the fast sampling phase when four different in-situ campaigns of the SWOT-Adac Consortium (C-SWOT-2023, WEMSWOT, FaSt-SWOT and BIOSWOT-Med) led to the deployment of numerous in situ instruments, including drifters, in order to sample the upper ocean underneath SWOT tracks. We also provide preliminary results for analysis at the global scale which broadens the range of dynamical regimes and instrumental conditions considered.