Enhanced carbon dioxide outgassing from the eastern equatorial Atlantic during the last glacial
Enhanced carbon dioxide outgassing from the eastern equatorial Atlantic during the last glacial
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DOI：
10.1130/g35806.1
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发表时间：
2014-11-01
期刊：
影响因子：
5.8
通讯作者：
Sexton, P. F.
中科院分区：
文献类型：
--
作者：
Foster, G. L.;Sexton, P. F.
赤道大西洋的生物生产力和碳输出被认为在末次冰期比全新世高得多。在这里，我们重建的pH值和CO2含量的表面沃茨从东赤道大西洋在过去类似于30千年。使用Globigerinoides ruber（一种混合层居的浮游有孔虫）的硼同位素组成。我们的新记录，结合以前发表的数据，表明在末次冰期，与今天相反，在空气：海洋平衡的范围内存在一个强大的西向东梯度，相对于pCO（2）（Delta pCO（2）），东赤道大西洋作为一个重要的CO2来源（+100 mu atm），而西大西洋保持接近平衡（+25 mu atm）。这种模式表明，在最后一次冰期，较深的沃茨上升速率增加了五倍，推动了大西洋生产力的增加和大规模的区域冷却，但比现代更高。东部的pCO（2）表明，输出生产没有跟上营养物上升流的增强。然而，Delta pCO（2）的下游下降提供了证据，证明东部未使用的营养物质最终用于生物碳输出，从而有效地抵消了上升流变化对大气CO2水平的影响。我们的研究结果表明，赤道大西洋发挥了最小的作用，有助于较低的冰川期大气二氧化碳。
Biological productivity and carbon export in the equatorial Atlantic are thought to have been dramatically higher during the last glacial period than during the Holocene. Here we reconstruct the pH and CO2 content of surface waters from the eastern equatorial Atlantic Ocean over the past similar to 30 k.y. using the boron isotope composition of Globigerinoides ruber (a mixed-layer-dwelling planktic foraminifera). Our new record, combined with previously published data, indicates that during the last glacial, in contrast to today, a strong west to east gradient existed in the extent of air: sea equilibrium with respect to pCO(2) (Delta pCO(2)), with the eastern equatorial Atlantic acting as a significant source of CO2 (+100 mu atm) while the western Atlantic remained close to equilibrium (+25 mu atm). This pattern suggests that a fivefold increase in the upwelling rate of deeper waters drove increased Atlantic productivity and large-scale regional cooling during the last glacial, but the higher than modern. pCO(2) in the east indicates that export production did not keep up with enhanced upwelling of nutrients. However, the downstream decline of Delta pCO(2) provides evidence that the unused nutrients from the east were eventually used for biologic carbon export, thereby effectively negating the impact of changes in upwelling on atmospheric CO2 levels. Our findings indicate that the equatorial Atlantic exerted a minimal role in contributing to lower glacial-age atmospheric CO2.