Meso to sub-mesoscale variability observed by Sentinel-3A

Oscar Vergara (CLS, France)


Rosemary Morrow (LEGOS, France); Isabelle Pujol (CLS , France); Gérald Dibarboure (CNES, France); Clément Ubelmann (CLS, France)

Event: 2019 Ocean Surface Topography Science Team Meeting

Session: Science III: Mesoscale and sub-mesoscale oceanography

Presentation type: Type Poster

Recent evidence from along-track Sea Surface Height observations (1 Hz) has demonstrated the capabilities of current generation altimeters to tease out the oceanic variability in the meso to sub-mesoscale wavelength range.

In the present work, we update previous results on the submesoscale wavelength range (λ < 100 km) using two years of Sentinel-3A SSH observations (20 Hz), reprocessed using a novel waveform stacking method developed by CNES (SAR/LR-RMC). The main objective is to diagnose the characteristic scale that marks the shift from balanced-motion (eddy) dominated towards unbalanced-motion (wave) dominated in the SSH spectrum (Transition Scale; Lt). Higher signal to noise ratio is obtained due to the LR-RMC reprocessing, improving the observability of fine scale variability. This materializes as an improvement in our estimates of Lt and its comparisons against modeling results.

Our estimates of average Lt and its spatial distribution at global scale are in agreement with the values predicted by global models. The lowest values (Lt < 50 km) are found at the highly energetic western boundary current systems, marking a clear asymmetry with the eastern boundaries in all the ocean basins (Lt ~100-150 km). Lt values progressively increase from the mid-latitudes (~150 km) towards the equatorial ocean (Lt > 250 km), consistent with the increased dominance of unbalanced over balanced motions in the SSH variability that is observed at low latitudes. We also observe a seasonal cycle of Lt , showing the same phase as the one predicted by global models, and reported by in situ measurements. However, the amplitude of the altimetry-derived seasonal cycle of Lt is below that computed from numerical simulations. Limitations of our methodology and implications for the future wide-swath observations from SWOT are discussed.

Poster show times:

Room Start Date End Date
The Gallery Tue, Oct 22 2019,16:15 Tue, Oct 22 2019,18:00
The Gallery Thu, Oct 24 2019,14:00 Thu, Oct 24 2019,15:45
Oscar Vergara