Global sea-level budget and ocean-mass budget, with a focus on advanced data products and uncertainty characterisation
Authors: Horwath Martin , Gutknecht Benjamin D. , Cazenave Anny , Palanisamy Hindumathi Kulaiappan , Marti Florence , Marzeion​​​​​​​ Ben , Paul Frank , Le Bris Raymond , Hogg Anna E. , Otosaka Inès , Shepherd Andrew , Döll Petra , Cáceres Denise , Müller Schmied Hannes , Johannessen Johnny A. , Nilsen Jan Even Øie , Raj Roshin P. , Forsberg René , Sandberg Sørensen Louise , Barletta Valentina R. , Simonsen Sebastian B. , Knudsen Per , Andersen Ole Baltazar , Ranndal Heidi , Rose Stine K. , Merchant Christopher J. , Macintosh Claire R. , von Schuckmann Karina , Novotny​​​​​​​ Kristin , Groh Andreas , Restano Marco , Benveniste Jérôme 
Published: February 2022

Abstract. Studies of the global sea-level budget (SLB) and the global ocean-mass
budget (OMB) are essential to assess the reliability of our knowledge of
sea-level change and its contributors. Here we present datasets for times
series of the SLB and OMB elements developed in the framework of ESA's
Climate Change Initiative. We use these datasets to assess the SLB and the
OMB simultaneously, utilising a consistent framework of uncertainty
characterisation. The time series, given at monthly sampling and available
at https://doi.org/10.5285/17c2ce31784048de93996275ee976fff (Horwath et
al., 2021), include global mean sea-level (GMSL) anomalies from satellite
altimetry, the global mean steric component from Argo drifter data with
incorporation of sea surface temperature data, the ocean-mass component from
Gravity Recovery and Climate Experiment (GRACE) satellite gravimetry, the
contribution from global glacier mass changes assessed by a global glacier
model, the contribution from Greenland Ice Sheet and Antarctic Ice Sheet
mass changes assessed by satellite radar altimetry and by GRACE, and
the contribution from land water storage anomalies assessed by the global
hydrological model WaterGAP (Water Global Assessment and Prognosis). Over the period January 1993–December 2016 (P1, covered by the satellite altimetry records), the mean rate (linear trend) of GMSL is 3.05 ± 0.24 mm yr−1. The steric component is 1.15 ± 0.12 mm yr−1 (38 % of the GMSL trend), and the mass component is 1.75 ± 0.12 mm yr−1 (57 %). The mass component includes 0.64  ± 0.03 mm yr−1 (21 % of the GMSL trend) from glaciers outside
Greenland and Antarctica, 0.60 ± 0.04 mm yr−1 (20 %) from
Greenland, 0.19 ± 0.04 mm yr−1 (6 %) from Antarctica, and
0.32 ± 0.10 mm yr−1 (10 %) from changes of land water storage. In the period January 2003–August 2016 (P2, covered by GRACE and the Argo drifter system), GMSL rise is higher than in P1 at 3.64 ± 0.26 mm yr−1. This is due to an increase of the mass contributions, now about 2.40 ± 0.13 mm yr−1 (66 % of the GMSL trend), with the
largest increase contributed from Greenland, while the steric contribution
remained similar at 1.19 ± 0.17 mm yr−1 (now 33 %). The SLB of
linear trends is closed for P1 and P2; that is, the GMSL trend agrees with
the sum of the steric and mass components within their combined
uncertainties. The OMB, which can be evaluated only for P2, shows that our
preferred GRACE-based estimate of the ocean-mass trend agrees with the sum of mass contributions within 1.5 times or 0.8 times the combined 1σ
uncertainties, depending on the way of assessing the mass contributions.
Combined uncertainties (1σ) of the elements involved in the budgets are between 0.29 and 0.42 mm yr−1, on the order of 10 % of GMSL rise.
Interannual variations that overlie the long-term trends are coherently
represented by the elements of the SLB and the OMB. Even at the level of
monthly anomalies the budgets are closed within uncertainties, while also
indicating possible origins of remaining misclosures.