Preliminary results of the new global barotropic tide model FES2026

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 the tide correction is one of the most critical. The accuracy of the tide models has been much improved for the last 30 years, and the most recent FES2022 model allowed reducing the residual errors in shelf and coastal seas and at high latitudes compared to previous version FES2014 and to other state-of-the-art global tide models. However improvements are still needed in these areas were the omission and the modelling error are still significant, but also on the global ocean.

 

In order to answer the new challenges of the tide correction for HR altimetry, in particular the SWOT mission, which gives access to unprecedent high-resolution sea surface measurements and very narrow coastal areas, a new global tide model FES2026 is currently under development.

 

This new model will benefit from new tidal frequencies that were not yet included in global tide models, as some minor third order of the tide potential tides and also some complementary non-linear frequencies that are most important in shallow and coastal zones. A dedicated omission error analysis was performed and gives some information about the main non-linear frequencies to take into account. Some evolutions are also envisioned concerning the improvement of the extrapolation procedure at the transition between ocean and land particularly in narrow fjords regions sampled by SWOT KaRIn measurements.

Some comparison with FES2022 and other global tide models (GOT5.6, R. Ray) are proposed. Preliminary validation results using several altimeter missions including SWOT mission, and also some in situ measurements will be presented.