New estimate of the current rate of sea level rise from a sea level budget approach

Abstract

We revisit the global mean sea level (GMSL) budget during the whole altimetry era (January 1993 to December 2015) using a large number of data sets. The budget approach allows quantifying the TOPEX A altimeter drift (amounting 1.5 ± 0.5 mm/yr over 1993–1998). Accounting for this correction and using ensemble means for the GMSL and components lead to closure of the sea level budget (trend of the residual time series being 0.0 ± 0.22 mm/yr). The new GMSL rate over January 1993 to December 2015 is now close to 3.0 mm/yr. An important increase of the GMSL rate, of 0.8 mm/yr, is found during the second half of the altimetry era (2004–2015) compared to the 1993–2004 time span, mostly due to Greenland mass loss increase and also to slight increase of all other components of the budget.

An improved and homogeneous altimeter sea level record from the ESA Climate Change Initiative

“…For the v2.0 GMSL, the same trend of 3.3 mm yr −1 is found for the 1993-2003 and 2005-2015 altimetry decades, indicating a steady rise of the GMSL. However, several recent studies using different approaches suggest that an instrumental drift has affected the TOPEX-A altimeter measurements during 1993(Valladeau et al, 2012Watson et al, 2015;Dieng et al, 2017;Beckley et al, 2017). The instrumental drift of the TOPEX-A altimeter has long been known (Hayne and Handcock, 1998), leading to the switch early 1999 to the redundant TOPEX-B altimeter.…”

“…Account-ing for the TOPEX-A instrumental correction for the first 6 years of the altimetry dataset, these studies provided a revised GMSL time series that slightly reduces the average GMSL rise over the altimetry era (from 3.3 to 3.0 mm yr −1 ), but shows clear acceleration over 1993-present. Using the corrected GMSL time series, Dieng et al (2017) and Chen et al (2017) found improved closure of the sea level budget compared to the uncorrected data.…”

“…The 1.5 mm yr −1 correction supposed to represent the TOPEX-A drift has been applied to the GMSL time series for 1993-1998 specifically in this figure as discussed in Sect. 4.1; see Dieng et al (2017) for details. We have also used the SL_cci v2.0 time series as well as additional GMSL products provided by other groups (DU-ACS DT2014 distributed by CMEMS -previously AVISOUniversity of Colorado, NOAA, NASA/GSFC and CSIRO) to compute the differences between each individual GMSL time series and the ensemble mean GMSL over 1993-2015.…”

“…Watson et al (2015) compared altimetry-based sea level with vertical land motion-corrected tide gauge data and estimated a TOPEX-A drift correction to the 1993-1998 GMSL trend in the range 0.9 ± 0.5 to 1.5 ± 0.5 mm yr −1 , with 1.5 mm yr −1 being the preferred value. Using a sea level budget approach, Dieng et al (2017) also estimated the TOPEX-A drift correction to 1.5 ± 0.5 mm yr −1 for 1993-1998. Another approach was followed by Beckley et al (2017), consisting of suppressing the so-called "internal calibrationmode" range correction, included in the TOPEX-A "net instrument" correction and considered as suspect.…”

“…We have considered the whole altimetry era and used the various datasets considered in Dieng et al (2017) to estimate the individual mass contributions (glaciers, ice sheets, stored land water, atmospheric water vapour and snow) of Eq. (1).…”