Sequestration of carbon in the deep Atlantic during the last glaciation
Sequestration of carbon in the deep Atlantic during the last glaciation
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DOI：
10.1038/ngeo2657
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发表时间：
2016-04
影响因子：
18.3
通讯作者：
Jimin Yu;L. Menviel;Zhangdong Jin;D. Thornalley;S. Barker;G. Marino;E. Rohling;Yanjun Cai;Fei Zhang;Xianfeng Wang;Yuhao Dai;P. Chen;W. Broecker
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作者：
Jimin Yu;L. Menviel;Zhangdong Jin;D. Thornalley;S. Barker;G. Marino;E. Rohling;Yanjun Cai;Fei Zhang;Xianfeng Wang;Yuhao Dai;P. Chen;W. Broecker
大约 7 万年前，当地球气候进入最后一次冰期时，大气中的二氧化碳浓度显着下降。人们怀疑从大气中去除的大部分碳已经进入深海，但碳储存增加的证据仍然难以捉摸。在这里，我们使用大西洋多个地点的底栖有孔虫的 B/Ca 比率来重建碳酸根离子浓度的变化，从而重建整个过渡期间大西洋深部的碳库存。我们发现，在 80,000 至 65,000 年前，大西洋深部碳酸根离子浓度下降了约 25 μmol kg−1。这一下降意味着，在大气碳含量减少约 60 Gt 的同时，大西洋深部碳库存增加了至少 50 Gt。通过与深层环流和气候模型模拟的代理记录的比较，我们推断碳固存与大西洋经向翻转环流的浅滩同时发生。因此，我们得出结论，大西洋环流的变化可能通过增加大西洋深部的碳储存，在末次冰期期间大气二氧化碳浓度的降低中发挥了重要作用。
Atmospheric CO2concentrations declined markedly about 70,000 years ago, when the Earth’s climate descended into the last glaciation. Much of the carbon removed from the atmosphere has been suspected to have entered the deep oceans, but evidence for increased carbon storage remains elusive. Here we use the B/Ca ratios of benthic foraminifera from several sites across the Atlantic Ocean to reconstruct changes in the carbonate ion concentration and hence the carbon inventory of the deep Atlantic across this transition. We find that deep Atlantic carbonate ion concentration declined by around 25 μmol kg−1between ∼80,000 and 65,000 years ago. This drop implies that the deep Atlantic carbon inventory increased by at least 50 Gt around the same time as the amount of atmospheric carbon dropped by about 60 Gt. From a comparison with proxy records of deep circulation and climate model simulations, we infer that the carbon sequestration coincided with a shoaling of the Atlantic meridional overturning circulation. We thus conclude that changes in the Atlantic Ocean circulation may have played an important role in reductions of atmospheric CO2concentrations during the last glaciation, by increasing the carbon storage in the deep Atlantic.