A new global ocean barotropic tide model: FES2022

Loren Carrere (CLS, France)

CoAuthors

Florent Lyard (LEGOS, France); Mathilde Cancet (NOVELTIS, France); Etienne Sahuc (NOVELTIS, France); Damien Allain (LEGOS, France); Yannice Faugère (CLS, France); Gérald Dibarboure (CNES, France); Nicolas Picot (CNES, France)

Event: 2020 Ocean Surface Topography Science Team Meeting (virtual)

Session: Tides, internal tides and high-frequency processes

Presentation type: Type Forum

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 tidal models has been much improved for last 25 years leading to centimetric accuracy in the open ocean. The last release of the global tidal model, referenced as FES2014b and distributed since mid-2016, takes advantage of long altimeter time series, better altimeter standards (instrumental and geophysical corrections, orbits), improved modelling and data assimilation techniques.
The underlying unstructured mesh resolution of FES2014b has been 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 previous version (FES2004). A specific loading tide solution is also proposed in coherency with FES2014b ocean solution. FES2014b validation results show a significant improvement particularly in shallow seas and in many parts of the Arctic region, compared to other global tidal models available (GOT4v10, DTU10, TPXO8). However some significant errors still remain mainly in those 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 facing the new challenges of the tide correction for HR altimetry, in particular the forthcoming SWOT mission, a new project FES2022 has started this year. This objective is to produce a more accurate global tidal solution, particularly for shallow waters and high latitudes. The new tidal solution will use higher spatial resolution in coastal areas, extending systematically the model mesh to the narrowest coastal systems (fjords, estuaries, …), and provide a more comprehensive tidal spectrum. Further improvements planned are the upgrade of the model bathymetry and to continue the effort on the hydrodynamic modelling accuracy by adding second-order terms in the tidal dynamics. The use of most recent high inclination altimeters like Cryosat-2, Saral/AltiKa and even Sentinel-3, will help improving the polar tides estimations. We present the outline of the project, the production plan and, the different ways of improvement of the new FES2022 global tide solution.
 
Loren Carrere
CLS
France
lcarrere@groupcls.com