Revisiting sea-level budget by considering all potential impact factors for global mean sea-level change estimation

Abstract

Accurate estimates of global sea-level change from the observations of Altimetry, Argo and Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-on (GRACE-FO) are of great value for investigating the global sea-level budget. In this study, we analyzed the global sea-level change over the period from January 2005 to December 2019 by considering all potential impact factors, i.e. three factors for Altimetry observations (two Altimetry products, ocean bottom deformation (OBD) and glacial isostatic adjustment (GIA)), three factors for Argo observations (four Argo products, salinity product error and deep-ocean steric sea-level change), and seven factors for GRACE/GRACE-FO observations including three official RL06 solutions, five spatial filtering methods, three GIA models, two C₂₀ (degree 2 order 0) products, Geocenter motion, GAD field and global mass conservation. The seven impact factors of GRACE/GRACE-FO observations lead to ninety combinations for the post-procession of global mean barystatic sea-level change estimation, whose rates range from 2.00 to 2.45 mm/year. The total uncertainty of global barystatic sea-level change rate is ± 0.27 mm/year at the 95% confidence level, estimated as the standard deviation of the differences between the different datasets constituting the ensembles. The statistical results show that the preferred GIA model developed by Caron et al. in 2018 can improve the closure of the global sea-level budget by 0.20-0.30 mm/year, which is comparable with that of neglecting the halosteric component. About 30.8% of total combinations (GRACE/GRACE-FO plus Argo) can close the global sea-level budget within 1-sigma (0.23 mm/year) of Altimetry observations, 88.9% within 2-sigma. Once the adopted factors including GRACE/GRACE-FO solutions from Center for Space Research (CSR), Caron18 GIA model, SWENSON filtering and Argo product from China Second Institute of Oceanography, the linear trend of global sterodynamic sea-level change derived from GRACE/GRACE-FO plus Argo observations is 3.85 ± 0.14 mm/year, nearly closed to 3.90 ± 0.23 mm/year of Altimetry observations.

Figure 1

The impact factors of global sea-level change estimated from Altimetry, Argo and RL06 solutions of GRACE/GRACE-FO observations.

Figure 2

The global mean sterodynamic sea-level change series over January 2005 to December 2019 with two Altimetry products.

Figure 3

The global mean thermosteric sea-level change derived from four Argo products. The ensemble mean of four components is displayed as a black line.

Figure 4

The linear trends of four potential impact factors on global mean barystatic sea-level change estimations over the study period. (a) Processing center, (b) C₂₀ correction, (c) Filtering method and (d) GIA correction.

Figure 5

The global mean sterodynamic and sea-level change estimation from Altimetry and Argo plus GRACE and GRACE-FO observations and corresponding differences from 2005 to 2019.

Figure 6

Linear trends of the global sea-level budget over January 2005 to December 2019 for Altimetry, Argo and GRACE/GRACE-FO observations over the sub-ensembles according to (a) processing center, (b) C₂₀ correction, (c) filtering method, (d) GIA correction and (e) Argo product.