The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

It remains unclear whether the regional sea-level trends observed during the altimeter-era (since 1993) are primarily driven by natural variability or external forcing. Utilizing altimeter measurements, this study develops an Empirical Orthogonal Function re-projection method to separate the externally forced signal from natural variability in the Pacific Ocean. By removing major natural variability, a more robust estimate of the forced sea-level trend is revealed, diverging notably from observed linear trends during the altimeter era. Present-day sea-level trends remain predominantly governed by natural variability, with trends reversing over decades in the tropical Pacific, and do not reflect persistent patterns driven by external forcing. Analysis from Ocean Reanalysis System 5 suggests that when using a 50-year timescale, more than half of the Pacific Ocean is expected to experience forced sea-level rise emergence. These findings underscore the importance of distinguishing the aliasing effect of low-frequency sea-level variability for accurate assessments of the forced sea-level rise emergence in the Pacific Ocean.