Reducing the Uncertainty in the Satellite Altimetry Estimates of Global Mean Sea Level Trends Using Highly Stable Water Vapor Climate Data Records

The global mean sea level (GMSL) has risen by 3.3 & PLUSMN; 0.2 mm.yr(-1) (68% confidence level) over 1993-2021. The wet troposphere correction (WTC) used to compute the altimetry-based mean sea level data is known to be a large source of error in the GMSL long-term stability. The WTC is derived from the microwave radiometers (MWR) on board the altimetry missions. In order to improve the long-term estimates of the GMSL, we propose an alternative WTC computation based on highly stable climate data records (CDRs) of water vapor derived from independent MWR measurements on board meteorological satellites. A polynomial model is applied to convert water vapor to WTC. The CDR-derived WTC enables reducing the low frequency uncertainty of the WTC applied to the altimetry data, hence reducing the uncertainty of the GMSL trend estimate. Furthermore, over 2016-2021, the comparison of MWR-based with CDR-based WTC shows a likely drift of the Jason-3 MWR WTC on the order of -0.5 mm.yr(-1) that would lead to an overestimation of the GMSL trend from 2016.