The multidecadal fluctuations in sea level changes play an important role in the exact quantification of present-day global mean sea level (GMSL) rise and its acceleration. Here, we use an array processing technique (optimal sequence estimation) to analyze 44 global tide gauge (TG) sea-level records with identical January 1933–December 2019 data spans. The results reveal for the first time a common 64.0 ± 3 years periodic oscillation with a spherical harmonic Y₂₁ spatial pattern. Based on the estimated equivalent “excitation” amplitude (A = 47.7 ± 2 mm) and phase (φ = −0.406 rad), we constructed a global model for this 64 years sea-level fluctuation. The complex amplitudes of the extracted ∼64 years fluctuation from 94 TG records with different data spans, and of two GMSL time series are consistent with the corresponding results predicted by the constructed model using the stacking results using 44 TGs. We find that the 64 years oscillation has significant contributions on the estimate of reconstructed GMSL trend: it contributed about 24% to the sea-level trend during 1993–2014 and cause a relative deceleration during 2024–2055; while it contributes slightly to the satellite-based GMSL trend estimates during 1993–2020. We confirm that this 64 years signal is not originated from the Earth's polar motion; however, it has good consistency with the Earth's magnetic field dipole changes, and with the ∼65 years oscillation in the ΔLOD, which suggests that this 64 years signal could come from core motions. We believe our results unravel a new understanding of the mechanisms of GMSL's long-term fluctuations within the Earth system.

中文翻译：

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新发现的 64 年共同振荡对当今全球平均海平面上升的估计的贡献

海平面变化的数十年波动在准确量化当今全球平均海平面 (GMSL) 上升及其加速方面发挥着重要作用。在这里，我们使用阵列处理技术（最佳序列估计）来分析 44 个具有相同 1933 年 1 月至 2019 年 12 月数据跨度的全球潮位计 (TG) 海平面记录。结果首次揭示了具有球谐Y ₂₁空间模式的常见 64.0 ± 3 年周期振荡。基于估计的等效“激励”幅度 ( A  = 47.7 ± 2 mm) 和相位 ( φ = -0.406 rad)，我们为这 64 年的海平面波动构建了一个全球模型。从具有不同数据跨度的 94 条 TG 记录和两个 GMSL 时间序列中提取的~64 年波动的复振幅与使用使用 44 TG 的叠加结果构建的模型预测的相应结果一致。我们发现64年的振荡对重建的GMSL趋势的估计有显着贡献：它对1993-2014年海平面趋势的贡献约为24%，并在2024-2055年造成相对减速；而它对 1993-2020 年基于卫星的 GMSL 趋势估计的贡献很小。我们确认这个 64 年的信号不是来自地球的极地运动；但是，它与地球磁场偶极子变化具有很好的一致性，并且随着 ΔLOD 的 65 年振荡，这表明这个 64 年的信号可能来自核心运动。我们相信我们的结果揭示了对地球系统内 GMSL 长期波动机制的新理解。