1502. Accelerating Sea Level Rise: Improved Observations Advance Understanding of Its Drivers

Global mean sea level (GMSL) rise is primarily caused by thermal expansion of seawater due to ocean warming, as well as increases in ocean mass resulting from glacier and ice-sheet melt. Whether observed sea level rise can be fully explained by these known contributors is considered a critical issue for improving the reliability of future climate projections and coastal adaptation planning.

In this study, researchers integrated the latest observational datasets, including tide gauges, satellite altimetry, Argo floats, and GRACE gravimetry satellites, to analyze the sea level budget over three periods: 1960–2023, 1993–2023, and 2005–2023. The results show that the residual difference between observed sea level rise and the sum of all contributing factors was reduced to within 0.18 mm per year for all analyzed periods, indicating that the sea level budget is now nearly closed.

The study also confirmed that the rate of GMSL rise has accelerated over time, increasing from 2.06 mm per year during 1960–2023 to 3.41 mm per year during 1993–2023 and 3.94 mm per year during 2005–2023. Since 1960, thermal expansion has been identified as the largest contributor, accounting for 43% of total sea level rise, followed by glacier melt, the Greenland Ice Sheet, and the Antarctic Ice Sheet.

According to the authors, the improved budget closure was achieved through advances in satellite altimetry corrections, improved quality control of ocean temperature observations, updated ice-sheet mass balance estimates, and improved corrections for vertical land motion in tide-gauge records. At the same time, the study notes that substantial uncertainty still remains in estimates of land water storage, including groundwater use.

These findings suggest that advances in Earth observation systems are bringing scientists closer to accurately quantifying the major drivers of sea level rise. The study also highlights the importance of maintaining and improving long-term satellite and ocean observing systems to enhance future sea level projections.

(Reference)
Huayi Zheng et al., Improved closure of the global mean sea level budget from observational advances since 1960, Science Advances, Vol.12, Issue 21 (2026). DOI: 10.1126/sciadv.aea0652

Contributor: IIYAMA Miyuki, Strategic Coordination Office