The new FES2022 tidal atlas.

    Thanks to its current accuracy and maturity, altimetry is considered as a fully operational observing system dedicated to various applications such as climate studies. Altimeter measurements are corrected from several geophysical parameters in order to isolate the oceanic variability and tide correction is one of the most critical. The accuracy of tidal models has been much improved for the last 25 years leading to centimetric accuracy in the open ocean. The last release of the global tidal model, referenced as FES2014b was distributed in mid-2016.

The underlying unstructured mesh resolution of FES2014b was increased in areas of interest like shallow waters and on the slope of the continental shelves, and the error of the pure hydrodynamic ocean solution has been divided by a factor of 2 compared to the previous version (FES2004). Still, some significant errors remain in some regions, due to the omission of compound tides and bathymetric errors (in shelf/coastal seas), seasonal sea ice effects, and lack of available data for assimilation (in the high latitudes).

To address the reduction of these errors and face the new challenges of the tide correction for HR altimetry, in particular, the forthcoming SWOT mission, a new global tide model FES2022 has been developed, focusing particularly on shallow waters and high latitudes.
This new tidal solution uses higher spatial resolution in coastal areas, extending systematically the model mesh to the narrowest coastal systems (fjords, estuaries, …), and the model bathymetry has been upgraded in many places thanks to an international collaboration effort. The hydrodynamic modeling benefits also from further improvements which allow producing very accurate hydrodynamic simulations. The use of the most recent altimeter standards and high inclination altimeters like Cryosat-2, Saral/AltiKa, and even Sentinel-3, also allowed retrieving some tide observations in the highest latitudes to help improving the polar tides modeling.

    Results show a great improvement in the FES2022 hydrodynamic solution compared to FES2014’s one. The assimilation procedure was conducted, and a specific loading tide solution was produced. The final FES2022 tidal solution was validated in comparison to the FES2014b, EOT20, GOT, and TPXO9v5 models, for the missions Jason 3, Sentinel-3A, and Cryosat-2.  Some validations of the new FES2022 tidal current are also presented here.