Zhang, W., Yang, F., and Luo, Z. (2025)
Presented at:
AGU Annual Meeting 2025The Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) underscores that mass-driven (barystatic) sea-level rise accounted for 44% of total sea level increase from 1993-2018, making its precise measurement essential for coastal risk management. However, the proliferation of the Gravity Recovery and Climate Experiment (GRACE) gravity field models (GSMs) and ocean model outputs has revealed that current geocenter motion used to compensate for missing degree-1 terms in GRACE GSMs may introduce substantial uncertainties in both global and spatial estimates of barystatic sea level. This study presents a systematic evaluation of barystatic sea-level uncertainty arising from geocenter motion discrepancies, employing nine GSMs and the ocean bottom pressure (OBP) from the Estimating the Circulation and Climate of the Ocean (ECCO) through the GRACE-OBP approach. Key findings demonstrate: (1) geocenter motion uncertainties reach to 0.31 mm (X-axis), 0.24 mm (Y-axis), and 0.22 mm (Z-axis); (2) These discrepancies translate to uncertainty in barystatic sea-level up to 0.99 mm, equivalent to 358 gigatons of terrestrial water storage variation; (3) Spatial error analysis reveals potentially misestimated barystatic signals exceeding 5 mm along Australian southwestern coast. To address IPCC's priority for accurate sea-level budget closure and decision-relevant projections, we propose tailored geocenter motion corrections for individual GSMs or an integrated multi-model fusion approach. These solutions enhance barystatic signal accuracy, particularly for dynamic coastal regions where precise mass-change quantification is crucial for hazard assessment. By bridging gaps between satellite gravimetry and coastal sea-level science, this work advances methodologies to meet the IPCC's demand for improved estimation of past, present, and future sea-level changes.
