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Toulouse Global and Regional Tidal Atlas:

Toulouse Global and Regional Tidal Atlas: a review on progress and recent results in tidal science and products. F. Lyard, T. Letellier, L. Roblou, D. Greenberg* Legos laboratory, CNES/CNRS, Toulouse. The huge benefits of 15 years of altimetry.

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Toulouse Global and Regional Tidal Atlas:

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  1. Toulouse Global and Regional Tidal Atlas: a review on progress and recent results in tidal science and products F. Lyard, T. Letellier, L. Roblou, D. Greenberg* Legos laboratory, CNES/CNRS, Toulouse

  2. The huge benefits of 15 years of altimetry • Altimetry and associated scientific efforts have allowed an unprecedented scientific break-through in tidal sciences • Expected benefits: • precise knowledge of global tidal elevation • Co-lateral benefits: • estimate of the tidal energy budget and tidal cuurents • investigation of long period tides, atmosperically forced tides, non-linear tides • re-discovery of the internal tide issue

  3. Toulouse approach • Hydrodynamic, spectral, quasi-linearized model (CEFMO) • Finite elements discretisation • Harmonic data assimilation, representer method (CADOR)

  4. FES2004 atlas from CEFMO/CADOR spectral model Mf Mm Mmtm Msqm : hydrodynamic K1 O1 P1 Q1 : assimilation S1 : hydrodynamic M2 S2 N2 K2 2N2 : assimilation M4 : hydrodynamic

  5. M2 tide, GOT00 versus FES2004 (difference modulus in cm) Recent models (TPXO, GOT, FES) have now converged, except somehow in shelf/coastal areas Data assimilation is responsible for model accuracy and convergence

  6. The easy part being done, what’s left ? • Tidal dynamic • Shelfs seas tides precise modelling/observation/assimilation • non-linear tides, trapped waves etc… • Variability of the tides (ice cover, stratification, atmospheric forcing) • 3D processes (internal tides) • Coupling with ocean circulation: • Global residual transport • Ocean mixing • Deep ocean/shelf seas and inter-basin straits exchanges

  7. Hydrodynamic, time stepping, non-linear model (Mog2D/Mog3D) • Finite elements (triangle, prisms) discretisation • EnKF assimilation (SEQUOIA) • UGO initiative: Mog2D/Mog3D > T-UGO model • objectives: • Improve the global 2D hydrodynamic model • Numerical schemes • Internal wave parameterisation • Loading/self attraction • Non-elastic loading and solid tide ??? • Global assimilation • Fill the accuracy gap between open ocean and shelves: • Develop assimilation techniques suitable for coastal areas • Implement experimental regional models • Exploit the multi-mission data set and tides gauges for assimilation • Develop the 3D hydrodynamicmodel for internal waves

  8. Internal tide parametrisation reduces global tidal solution error by a factor 2 Large topographic scales, i.e. larger than the tidal excursion=O(1000 m): Small topographic scales (smaller than the tidal excursion): Still need to be improved and tuned regionally

  9. Spectral, Lagrange P2 Time stepping, Lagrange P1 M2 tide, FES2002-H versus FES2004 (difference modulus in cm) M2 tide, model versus FES2004 (difference modulus in cm)

  10. Spectral, Lagrange P2 Time stepping, Lagrange P1 K1 , FES2002-H versus FES2004 (difference modulus in cm) K1 , model versus FES2004 (difference modulus in cm)

  11. M4 tide

  12. Tidal velocities M2 tidal constituent, minimum and maximum currents (cm/s) K1 tidal constituent, minimum and maximum currents (cm/s) Figure 29 : K1 tidal constituent, minimum and maximum currents (cm/s)

  13. Residual tidal transport and stream function

  14. VHR FE mesh : 1000 000 nodes

  15. Regional models implementation Preliminary results

  16. Patagonian shelf model

  17. China Sea model

  18. What is needed for further progress? • Global, accurate bathymetry • Better understading of energy conversion and internal wave propagation/dissipation • 2D/3D hydrodynamic model and assimilation developments • Unstructured Grid Ocean models (UGO) initiative • A close cooperation between ocean circulation and tidal community • We need to call for an extended tidal group including global and regional modellers to address barotropic and baroclinic tides and processes dynamically linked with the tides. • We need a variety of approaches, including a variety of hydrodynamic models.

  19. Tides in a stratified ocean • Circulation in a tidal ocean

  20. DEV1 : Longueur d’onde (km) - Mode nº1

  21. Résultats 1 16 20 Kz (x,y,z,t) induit par la marée 18 14 dans DEV1 Kz linéaire canonique (0.1-1.2cm2.s-1) • Robustesse de l’Intensité de la NADW à 16 Sv • AABW à 20 Sv →+ Réaliste : Comparable aux 27 Sv trouvés par Sloyan & Rintoul (2001) • + Forte Variabilité de la Structure Spatiale de la MOC 16 10 Kz constant observé (0.1cm2.s-1) Overturnings globaux (Fonctions de courant associées aux transports méridien et verticaux) NADW : North Atlantic Deep Water AABW : Antarctic Bottom Water

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