Coral‐Based Sea Surface Salinity Reconstructions and the Role of Observational Uncertainties in Inferred Variability and Trends
Coral‐Based Sea Surface Salinity Reconstructions and the Role of Observational Uncertainties in Inferred Variability and Trends
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DOI：
10.1029/2021pa004371
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发表时间：
2022-05
影响因子：
3.5
通讯作者：
Emma V. Reed;Diane M. Thompson;K. Anchukaitis
中科院分区：
文献类型：
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作者：
Emma V. Reed;Diane M. Thompson;K. Anchukaitis
世纪的大部分时间里，热带海洋的气候观测都很稀少，因此需要古气候代用品来了解自然气候变化的全部范围。过去的替代研究主要集中在海面温度，但有相对较少的盐度重建。这样的重建可以扩展我们对整个热带海洋水文气候的理解，包括降水，蒸发和海洋环流的变化。在这里，我们编制了一个网络的盐度敏感的珊瑚δ 18 O记录，然后应用基于经验正交函数分析的缩减空间方法来重建20世纪的年度热带盐度异常。对包括再分析（SODA 2/3、海洋再分析系统5、全球海洋数据同化系统）和客观分析（大气物理研究所、EN 4、Delcroix）在内的表面盐度数据集进行的比较表明，在空间结构、时间演变和主要变率模式的重要性方面存在很大差异。两个盐度数据集，IAP和ORAS 5，被保留用于气候重建。我们基于珊瑚的盐度重建揭示了20世纪显著的长期趋势，这可能与水文循环强化和步行者环流的减弱有关。这些重建还捕获了与厄尔尼诺-南方涛动，年代际太平洋涛动和大西洋年代际涛动相关的盐度异常的空间和时间模式。最终，这种方法可以增强我们对观测时代之前热带水文气候的理解。
Climate observations in much of the tropical oceans are scarce during most of the 20th century, so paleoclimate proxies are needed to understand the full range of natural climate variability. Past proxy studies have focused primarily on sea surface temperatures, but there are comparatively few salinity reconstructions. Such reconstructions can extend our understanding of hydroclimate across the tropical oceans, including variability in precipitation, evaporation, and ocean circulation. Here we compile a network of salinity‐sensitive coral δ18O records, then apply a reduced‐space method based on empirical orthogonal function analysis to reconstruct annual tropical salinity anomalies over the 20th century. A comparison of surface salinity data sets, including reanalyzes (SODA2/3, Ocean ReAnalysis System 5 (ORAS5), Global Ocean Data Assimilation System) and objective analyses (Institute of Atmospheric Physics (IAP), EN4, Delcroix), show large discrepancies in the spatial structure, temporal evolution, and importance of the leading modes of variability. Two salinity data sets, IAP and ORAS5, are retained for climate reconstruction. Our coral‐based salinity reconstructions reveal significant long‐term trends over the 20th century, which are likely associated with hydrological cycle intensification and possibly a weakening of the Walker Circulation. These reconstructions also capture the spatial and temporal patterns of salinity anomalies associated with the El Niño‐Southern Oscillation, Interdecadal Pacific Oscillation, and Atlantic Multidecadal Oscillation. Ultimately, this approach can enhance our understanding of tropical hydroclimate prior to the observational era.