19 Oct 2022
19 Oct 2022
Status: this preprint is open for discussion.

Global submesoscale diagnosis using alongtrack satellite altimetry

Oscar Vergara1,2, Rosemary Morrow2, Marie-Isabelle Pujol1, Gérald Dibarboure3, and Clément Ubelmann4 Oscar Vergara et al.
  • 1CLS Space Oceanography, Ramonville Saint-Agne, 31520, France
  • 2LEGOS, IRD/CNES/CNRS/University of Toulouse, Toulouse, 31400, France
  • 3CNES, Toulouse, 31400, France
  • 4Datlas, Grenoble, 38000, France

Abstract. The ocean’s sea surface height (SSH) field is a complex mix of motions in geostrophic balance and unbalanced motions including high-frequency tides, internal tides and internal gravity waves. Barotropic tides are well estimated for altimetric SSH in the open ocean, but the SSH signals of internal tides remains. The transition scale, Lt, at which these unbalanced ageostrophic motions dominate balanced geostrophic motions, is estimated for the first-time using satellite altimetry. Lt is critical to define the spatial scales above which surface geostrophic currents can be inferred from SSH gradients. We use a statistical approach based on the analysis of 1 Hz altimetric SSH wavenumber spectra to obtain four geophysical parameters that vary regionally and seasonally: the background error, the spectral slope in the mesoscale range, a second spectral slope at smaller scales, and Lt. The mesoscale slope and error levels are similar to previous studies based on satellite altimetry. The break in the wavenumber spectra to a flatter spectral slope can only be estimated in mid-latitude regions where the signal exceeds the altimetric noise level. Small values of Lt are observed in regions of energetic mesoscale activity, while larger values are observed towards low latitudes and regions of lower mesoscale activity. These results are consistent with recent analyses of in situ observations and high-resolution models. Limitations of our results and implications for reprocessed nadir and future swath altimetric missions are discussed.

Oscar Vergara et al.

Status: open (until 14 Dec 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-1073', Anonymous Referee #1, 14 Nov 2022 reply
  • RC2: 'Comment on egusphere-2022-1073', Anonymous Referee #2, 05 Dec 2022 reply

Oscar Vergara et al.

Oscar Vergara et al.


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Short summary
Recent advances allows us to observe the ocean from space with increasingly higher detail, challenging our knowledge of the ocean's surface height signature. We use a statistical approach to determine the spatial scale at which the sea surface height signal is no longer dominated by geostrophic turbulence but in turn it becomes dominated by wave-type motions. This information helps us to better use the data provided by ocean-observing satellites and to gain knowledge on climate-driving processes.