Southern Ocean link between changes in atmospheric CO2 levels and northern-hemisphere climate anomalies during the last two glacial periods
Southern Ocean link between changes in atmospheric CO2 levels and northern-hemisphere climate anomalies during the last two glacial periods
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DOI：
10.1016/j.quascirev.2019.106067
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发表时间：
2020-02
影响因子：
4
通讯作者：
J. Gottschalk;L. Skinner;S. Jaccard;L. Menviel;Christoph Nehrbass-Ahles;C. Waelbroeck
中科院分区：
文献类型：
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作者：
J. Gottschalk;L. Skinner;S. Jaccard;L. Menviel;Christoph Nehrbass-Ahles;C. Waelbroeck
过去千年尺度的大气二氧化碳(二氧化碳，大气层)浓度的变化通常被归因于海洋倾覆时间尺度的变化，从而导致海洋碳清单的变化。然而，仍然缺乏替代证据来记录全球海洋碳储量的变化，并将这些变化与北半球与大西洋子午线翻转环流(AMOC)扰动有关的突然气候变化联系起来。最后两个冰期被认为在AMOC的空间范围和对扰动的敏感性上有所不同。这为比较它们之间海洋碳循环-气候反馈的性质提供了机会。在这里，我们重建了南大西洋深处呼吸碳储存(通过氧合)和AMOC“几何结构”(通过碳酸盐离子饱和)的变化。我们推断，在两个冰川时期，AOC减弱和二氧化碳浓度上升时，南大西洋深处呼吸的碳水平会下降。这些发现表明，在北半球体育场期间，南大洋对流和/或海-气CO2通量增加的模式是一致的，伴随着AMOC扰动，并促进了二氧化碳、大气水平的上升。我们发现，海洋净碳损失，以及二氧化碳的上升幅度，在很大程度上是由稳定的持续时间决定的。因此，北大西洋气候异常通过海洋(例如，通风翘板)和/或大气过程(例如，埃克曼抽水)以一致的方式影响南大洋的碳循环。
Past millennial-scale changes in atmospheric CO2(CO2,atm) concentrations have often been attributed to variations in the overturning timescale of the ocean that result in changes in the marine carbon inventory. Yet, there remains a paucity of proxy evidence that documents changes in marine carbon storage globally, and that links them to abrupt climate variability in the northern hemisphere associated with perturbations of the Atlantic Meridional Overturning Circulation (AMOC). The last two glacial periods were suggested to differ in the spatial extent of the AMOC and its sensitivity to perturbations. This provides an opportunity to compare the nature of marine carbon cycle-climate feedbacks between them. Here, we reconstruct variations in respired carbon storage (via oxygenation) and the AMOC “geometry” (via carbonate ion saturation) in the deep South Atlantic. We infer decreases in deep South Atlantic respired carbon levels at times of weakened AMOC and rising CO2,atmconcentrations during both glacial periods. These findings suggest a consistent pattern of increased Southern Ocean convection and/or air-sea CO2fluxes during northern-hemisphere stadials accompanying AMOC perturbations and promoting a rise in CO2,atmlevels. We find that net ocean carbon loss, and hence the magnitude of CO2,atmrise, is largely determined by the stadial duration. North Atlantic climate anomalies therefore affect Southern Ocean carbon cycling in a consistent manner, through oceanic (e.g., ventilation seesaw) and/or atmospheric processes (e.g., Ekman pumping).