1. Observing mesoscale to submesoscale dynamics today – & in the future with SWOT Rosemary Morrow LEGOS, Toulouse Lee-Lueng Fu JPL - NASA

2. « Our current knowledge of mesoscale eddy activity in the ocean derived from altimetry is largely based on gridded AVISO data sets » 18 year time series (w. minimum 2 altimeters ) => monitoring the impact of mesoscale eddies on the large-scale climate system

3. Tracking large-scale non-linear eddies over years Eddies mainly generated near E boundaries & bathymetry Cyclones tend to the poles , anticyclones to the equator Morrow et al., 2004 Chelton et al., 2010 Cyclones : 84% poleward Anti-cyclones : 74% equatorward

4. Strong zonal mean ocean jets – impact on atmospheric circulation 10 year mean zonal surface geostrophic velocity after Maximenko et al., 2008

5. Surface currents drive strong filamentation Tracer released into an evolving 2D altimetric current field develops filamentation patterns F. D’Ovidio, LOCEAN, Paris Day 0 Day 10 Day 15 Observed Tracer => Statistical techniques based on evolving altimetric currents now used to derive filament zones Tracer filaments patterns can be observed from satellite SST or ocean color ( Chlorophyll ) Filament positions derived from Lyapanuv exponants

8. 1st problem : Missing open ocean mesoscale eddies Mesoscale processes (driving the horizontal dynamics) only partially observed with present generation altimeters (scales > 150 km) Chelton et al., 1998 Only larger eddies resolved by mapped data

9. 2nd problem : Missing coastal structures Coastal & high latitude processes only partially observed with present generation altimeters (scales > 150 km) Eddy scales & amplitudes increase offshore Example : Bay of Biscay Space scales (km) Standard altimetric maps smooth out smaller nearshore eddies, EKE reduced by 50% Number of eddies Eddy amplitudes (cm) From Dussurget et al., 2011

11. Nadir altimetry : 7 km alongtrack over oceans : resolves 30-50 km alongtrack, 150 km between tracks SWOT : 1 km posting over oceans : resolve ~10 km in 2D (baroclinic Rossby radius)

12. Mesoscale eddies drive the ocean’s lateral stirring, advection & mixing Sub-mesoscale fronts and filaments drive the vertical exchanges R. Ferrari, MIT Mesoscale Eddies, fronts & filaments

13. Reconstructing vertical velocities in the upper ocean Under certain conditions, surface QG theory can be used to reconstruct the 3D ocean currents ( u, v, w ) in the upper ocean 0-500 m depth, starting from high-resolution SSH. Observed W and Rel. Vorticity at 200 m Reconstructed W and Rel. Vorticity at 200 m P. Klein, Ifremer

14. Separating internal tide signature from mesoscale eddy processes R. Ray, GSFC 100 10 km 1000

16. Thank you!

17. Improving marine geoid accuracy GRACE and GOCE resolve only large-scale anomalies (spherical harmonic degree < 200, or wavelength > 200 km). This is because they measure the field at satellite orbital altitude. Satellite altimeters measure the effect of the gravity field on sea level, so they resolve shorter scales. SWOT’s 22 day repeat, global coverage of fine-resolution sea surface slopes will provide unprecedented 2D spatial resolution for marine geodesy. Figure from the GOCO1S combined GRACE-GOCE model document, R. Pail et al., 23-07-2010.