Margot Demol

Supervisors : Pierre Garreau, Aurélien Ponte

Funding : 100% ifremer

Start date : october 2022

Summary :

The emergence of wide-swath altimetry with the launch of the SWOT satellite in December 2022 and high-resolution characterization (spatial and temporal scales < 100km and 1 months) of the resulting surface ocean dynamics are two major oceanographic events of this decade. At these small scales, geostrophy, used for classical surface dynamic estimation from altimetry, is jeopardized by the signature of high frequency ageostrophic motions (inertial oscillations, tides etc, Yu et al. 2021), whose contribution is still not properly determined. Other studies also show that other sources of observations, such as drifters, can be highly complementary to tease apart geostrophic from ageostrophic motions (Caspar-Cohen et al. 2022, Yu et al. 2019).

This PhD aims at taking advantage of the complementarity of diverse source of observations - altimetry, drifters and wind product - to reconstruct the ocean surface dynamic momentum conservation, including ageostrophic terms.

Main questions are :

  • How each term of the momentum conservation quantitatively and geographically contribute to surface ocean dynamic ?
  • What are the errors weakening this reconstruction ?

This reconstruction will be carried out on a range of three different observational datasets :

  • A historical analysis using classical along-track altimetry and Global drifters Program (GDP) drifters (Elipot et al.2016)
  • An in-situ analysis using SWOT fast sampling phase altimetry and drifters released under SWOT swaths during different in situ campaigns.
  • A global analysis using SWOT global altimetry and GDP drifters.

This work is part of the larger International Calibration/Validation effort of the SWOT mission, gathering the SWOT Science Team and the SWOT ‘Adopt-A-Crossover’ Consortium endorsed by CLIVAR (Climate and Ocean - Variability, Predictability and Change).