Abstract's details

Impact of the TopEx/Poseidon GDR-F reprocessing on the Global Mean Sea Level climate data record

Adrien Guerou (CLS, France)


Anne Barnoud (Magellium, France); Michaël Ablain (Magellium, France); Hélène Roinard (CLS, France); François Bignalet-Cazalet (CNES, France); Gérald Dibarboure (CNES, France); Nicolas Picot (CNES, France)

Event: 2022 Ocean Surface Topography Science Team Meeting

Session: Regional and Global CAL/VAL for Assembling a Climate Data Record

Presentation type: Type Poster

Contribution: PDF file


The Global Mean Sea Level (GMSL) climate data record is monitored since 1992 thanks to the reference altimetry missions TopEx/Poseïdon, Jason-1/-2 /-3 and now Sentinel-6A MF. The first and historical mission TopEx/Poseïdon has been shown to be affected by an instrumental degradation of its side-A altimeter (Beckley et aL, 2018) from the middle of 1995 until the change to the side-B in February 1999. The instrumental degradation strongly affects the GMSL long-term stability (Watson et al., 2015; Dieng et al., 2017; Ablain et al., 2018) by about 1 mm/yr over all the TopEx-A period. Based on comparisons with tide gauges or on a sea level budget closure (SLBC) approach, empirical corrections of the TopEx-A GMSL drift were proposed (summarized in WCRP 2018). Applying an empirical correction significantly impacts the GMSL rise estimate over the first altimetry decade and allows the detection of a significant GMSL acceleration over the full data records (0.12±0.06 mm/yr^2). However, improving TopEx-A Geophysical Data Record (GDR) products would be preferable to the application of an empirical correction that is based on external data and subject to significant uncertainty.

A major update of the TopEx/Poseïdon GDR (i.e., GDR-F) has recently been generated by the JPL/CNES teams. It includes major improvements such as the use of numerical retracking of the altimeter instruments, consideration of the radiometer calibrations over the full lifetime of the mission, as well as improved geophysical corrections standards.

In this context, we will present the reference GMSL climate data record using the reprocessed TopEx/Poseidon GDR-F data products. A focus will be made on the estimation of the side-A/side-B GMSL offset determination, as well as its related uncertainties, a key contributor to the GMSL trend uncertainty at the beginning of the climate data record. Thanks to a combined comparison to tide-gauges and estimation of the SLBC, we will concentrate our presentation on the external validation of the major improvements on the TopEx side-A stability. Based on the estimation of each methods’ uncertainties, we will quantify the confidence level at which the TopEx side-A drift is reduced in the GDR-F data. Such analyses will also allow us to revisit the altimetry error budget at the time of the TopEx mission and improve the overall GMSL uncertainties.

Poster show times:

Room Start Date End Date
Mezzanine Tue, Nov 01 2022,17:15 Tue, Nov 01 2022,18:15
Mezzanine Thu, Nov 03 2022,14:00 Thu, Nov 03 2022,15:45
Adrien Guerou