16 Nov 2021
16 Nov 2021
Status: a revised version of this preprint is currently under review for the journal OS.

On the uncertainty associated with detecting global and local mean sea level drifts on Sentinel-3A and Sentinel-3B altimetry missions

Rémi Jugier1, Michaël Ablain1, Robin Fraudeau1, Adrien Guerou2, and Pierre Féménias3 Rémi Jugier et al.
  • 1MAGELLIUM, Ramonville Saint-Agne, 31520, France
  • 2CLS Collecte Localisation Satellites, Ramonville Saint-Agne, 31520, France
  • 3ESA/ESRIN, Frascaty, Italy

Abstract. An instrumental drift in the Point Target Response (PTR) parameters has been detected on the Copernicus Sentinel-3A (S3A) altimetry mission. It could have an impact on sea level rise of a few tenths of mm yr−1. In order to accurately evaluate this drift, a method for detecting global and local mean sea level relative drifts between two altimetry missions is implemented. Associated uncertainties are also accurately calculated thanks to a detailed error budget analysis. A drift on both S3A and S3B GMSL is detected with values significantly higher than expected. For S3A, the relative GMSL drift detected is 1.0 mm yr−1 with Jason-3 and 1.3 mm yr−1 with SARAL/AltiKa. For S3B, the relative GMSL drift detected is −2.2 mm yr−1 with SARAL/AltiKa and −3.4 mm yr−1 with Jason-3. The drift detected at global level does not show detectable regional variations above the uncertainty level of the proposed method. The investigations led by the altimeter experts can now explain the origin of this drift for S3A, while it is still under investigation for S3B. The ability of the implemented method to detect a sea level drift with respect to the length of the common period is also analysed. We find that the maximum detectable sea-level drift over a 5 years period is 0.3 mm yr−1 at the global scale, and 1.5 mm yr−1 at local scales (2400 km). However, these levels of uncertainty do not meet the sea-level stability requirements for climate change studies.

Rémi Jugier et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on os-2021-106', Graham Quartly, 12 Jan 2022
    • AC3: 'Reply on RC1', Rémi Jugier, 09 May 2022
  • AC1: 'Comment on os-2021-106', Rémi Jugier, 15 Apr 2022
    • EC1: 'Reply on AC1', Joanne Williams, 19 Apr 2022
      • AC2: 'Reply on EC1', Rémi Jugier, 19 Apr 2022
  • RC2: 'Comment on os-2021-106', Anonymous Referee #2, 22 Apr 2022
    • AC4: 'Reply on RC2', Rémi Jugier, 09 May 2022
  • AC5: 'Comment on os-2021-106', Rémi Jugier, 09 May 2022

Rémi Jugier et al.

Rémi Jugier et al.


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Short summary
To ensure that the sea level is measured as accurately as possible by satellite altimeters, we must monitor possible sea level drifts caused by those instruments, through comparison with other satellite altimeters or tide gauges. In this paper, we describe a method, and estimate the associated uncertainties, for detecting altimeter drifts on short time periods (from 2 to 10 years), through cross-comparison with other satellite altimeters, and apply it to the recent Sentinel-3 A/B altimeters.