A revised acceleration rate from the altimetry-derived global mean sea level record

Area of Science:

• Earth Science
• Oceanography
• Satellite Remote Sensing

Background:

• Satellite radar altimetry has monitored global mean sea level (GMSL) since 1992.
• The early TOPEX mission data requires careful calibration due to instrument changes and data inconsistencies.
• Accurate GMSL acceleration quantification is essential for understanding climate change impacts.

Purpose of the Study:

• To develop a novel method for calibrating TOPEX altimeter data.
• To provide a more accurate estimate of the intra-mission bias for the TOPEX record.
• To re-evaluate GMSL acceleration using improved calibration techniques.

Main Methods:

• Utilizing sea surface height differences at crossovers between TOPEX and ERS satellite altimetry data for calibration.
• Employing tide gauges solely to determine drift in one of the datasets.
• Estimating and correcting intra-mission biases within the TOPEX record.

Main Results:

• A new, more accurate estimate of the TOPEX intra-mission bias was determined.
• The revised calibration led to a significantly reduced estimate of GMSL acceleration over the entire record.
• The study confirms that GMSL acceleration remains uncertain, contrary to some recent claims.

Conclusions:

• The proposed calibration method improves the consistency of the TOPEX sea level record.
• Uncertainties in GMSL acceleration persist, challenging direct attribution to ocean warming and freshwater fluxes.
• Further research is needed to resolve the conundrum of GMSL acceleration from altimetry data.