Reduced misclosure of global sea-level budget with updated Tongji-Grace2018 solution

Fengwei Wang,Qiujie Chen,Yunzhong Shen,Yu Sun

doi:10.1038/s41598-021-96880-w

Abstract

The global sea-level budget is studied using the Gravity Recovery and Climate Experiment (GRACE) solutions, Satellite Altimetry and Argo observations based on the updated budget equation. When the global ocean mass change is estimated with the updated Tongji-Grace2018 solution, the misclosure of the global sea-level budget can be reduced by 0.11–0.22 mm/year compared to four other recent solutions (i.e. CSR RL06, GFZ RL06, JPL RL06 and ITSG-Grace2018) over the period January 2005 to December 2016. When the same missing months as the GRACE solution are deleted from altimetry and Argo data, the misclosure will be reduced by 0.06 mm/year. Once retained the GRACE C20 term, the linear trends of Tongji-Grace2018 and ITSG-Grace2018 solutions are 2.60 ± 0.16 and 2.54 ± 0.16 mm/year, closer to 2.60 ± 0.14 mm/year from Altimetry–Argo than the three RL06 official solutions. Therefore, the Tongji-Grace2018 solution can reduce the misclosure between altimetry, Argo and GRACE data, regardless of whether the C20 term is replaced or not, since the low-degree spherical harmonic coefficients of the Tongji-Grace2018 solution can capture more ocean signals, which are confirmed by the statistical results of the time series of global mean ocean mass change derived from five GRACE solutions with the spherical harmonic coefficients truncated to different degrees and orders.

Highlights

The global sea-level variations have been accurately measured by satellite altimetry s ince1 1992, which mainly contain two components: mass-induced variation due to mass exchange among the oceans, land and a tmosphere[2] and steric variation due to the changes in seawater temperature and salinity, which can be directly measured by the Argo project[3]
The conventional sea-level budget equation is expressed as follows[9], SLtotal=SLsteric + SLmass + ε where SLsteric refers to the contribution of ocean thermal expansion and salinity to sea-level change, and SLmass refers to the sea-level change due to the mass change in the oceans,ε is the difference often described as the misclosure
We use three Argo products provided by International Pacific Research Center (IPRC), Scripps Institute of Oceanography (SIO) and China Second Institute of Oceanography (CSIO) to compute the Global Mean Steric Sea Level (GMSSL) change rate between the latitude 64.5° S and 64.5° N, which is 1.19 ± 0.08 mm/year

Summary

Introduction

The global sea-level variations have been accurately measured by satellite altimetry s ince1 1992, which mainly contain two components: mass-induced variation due to mass exchange among the oceans, land and a tmosphere[2] and steric variation due to the changes in seawater temperature and salinity, which can be directly measured by the Argo project (with a reasonable global spatial coverage after 2005)[3]. With the released GRACE RL05 and RL06 solutions, the misclosure of the global sea-level budget has been significantly reduced among GRACE, Argo and Altimetry d ata[4,10,11,12], normally within the uncertainty (about 0.30 mm/year for trend) of the observations during the satellite era[13].

Results

Conclusion