NOAA/WDS Paleoclimatology - Tobago Coral Sr/Ca, Extension and SST Data from 1988-2016 CE

Massive, long-lived Siderastrea and Diploria corals are species commonly used for sea surface temperature (SST) reconstructions in the North Atlantic. However, they are rarely found to exceed 200 years in age. Thus, it is imperative to continuously develop alternative taxa for paleoreconstructions. Colpophyllia natans, a highly populous tropical North Atlantic coral, are known to grow large colonies, potentially containing environmental records spanning several hundreds of years. However, its low density and complicated architecture poses a challenge in extracting climate signals from this coral. This study presents the first monthly-resolved climate calibration of Colpophyllia natans and validates its utility as a new paleoarchive, relative to Siderastrea siderea. Linear regressions of monthly and interannual coral Sr/Ca with instrumental SST reveal robust, significant relationships (p<0.05), indicating that microsampling along a single thecal wall of C. natans allowed for robust climate reconstructions. Additionally, both corals capture similar SST variations (t-test, p≥0.05), which allowed for the generation of a single, composite interspecies SST record that correlates with instrumental SST even more strongly (p<0.0001) than the individual corals. Mean annual and boreal summer interspecies SST correlate significantly with North Atlantic SST indices (p<0.05), demonstrating the ability to capture regional, long-term SST trends in the North Atlantic. Spatial correlation maps of boreal winter interspecies SST to instrumental SST and geopotential height anomalies reveal coherent spatial patterns linked to the North Atlantic Oscillation. Our findings suggest that Colpophyllia natans has enormous potential as a new paleoclimate archive for reconstructing temporal and spatial SST variability in the tropical Atlantic.

大型长寿的星珊瑚属（Siderastrea）和盾形珊瑚属（Diploria）是北大西洋海域海表温度（SST）古重建研究中常用的珊瑚类群，但这类珊瑚的寿命极少能超过200年。因此，持续开发可用于古气候重建的替代类群迫在眉睫。扁平脑珊瑚（Colpophyllia natans）是北大西洋热带海域种群数量丰富的珊瑚物种，可形成大型珊瑚群落，理论上可保存数百年的环境记录。但该珊瑚骨骼密度较低且结构复杂，为从中提取气候信号带来了挑战。本研究首次对扁平脑珊瑚开展了月分辨率的气候校准，并验证了其作为新型古气候档案的应用潜力（以侧扁星珊瑚（Siderastrea siderea）作为对照物种）。对该珊瑚的月际及年际锶钙比值（Sr/Ca）与仪器观测海表温度进行线性回归分析，结果显示二者存在显著且稳定的相关关系（p<0.05），表明仅在扁平脑珊瑚的单个壁鞘处进行微取样即可实现可靠的气候重建。此外，两种珊瑚所记录的海表温度变化趋势高度一致（t检验，p≥0.05），据此可构建跨物种的复合海表温度记录，该复合记录与仪器观测海表温度的相关性比单一珊瑚物种更强（p<0.0001）。年平均及北半球夏季的跨物种复合海表温度记录与北大西洋海表温度指数存在显著相关（p<0.05），证明该复合记录可捕捉北大西洋区域的长期海表温度变化趋势。将北半球冬季的跨物种复合海表温度记录与仪器观测海表温度及位势高度异常进行空间相关分析，结果显示其空间分布格局与北大西洋涛动（North Atlantic Oscillation）密切相关。本研究结果表明，扁平脑珊瑚作为新型古气候档案，在重建热带大西洋海域海表温度的时空变化方面具有巨大应用潜力。