The Evolution of Deep Ocean Chemistry and Respired Carbon in the Eastern Equatorial Pacific Over the Last Deglaciation
The Evolution of Deep Ocean Chemistry and Respired Carbon in the Eastern Equatorial Pacific Over the Last Deglaciation
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DOI：
10.1002/2017pa003155
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发表时间：
2017-12-01
期刊：
影响因子：
--
通讯作者：
Cacho, Isabel
中科院分区：
文献类型：
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作者：
de la Fuente, Maria;Calvo, Eva;Cacho, Isabel
它已被证明，深东赤道太平洋（EEP）地区的通风不良，在末次盛冰期（LGM）相对于全新世值。这一发现表明了一种更有效的生物泵，这间接支持了深海碳储存增加的想法，有助于在末次冰期降低大气中的二氧化碳。然而，为了直接检验这一命题，需要与呼吸碳有关的代理。在这里，我们提出了Cibicides wuellerstorfi B/Ca比值从大洋钻探计划网站1240测量激光烧蚀电感耦合等离子体质谱（LA-ICPMS）作为一个代理深水碳酸盐饱和状态（[CO 32-]，因此[CO 32-]），沿着与C-13测量。此外，有孔虫涂层中的U/Ca比已被分析为氧合变化的指标。我们的研究结果表明，较低的[CO 32-]，C-13，和[O-2]值在末次冰期，这将是一致的，在深EEP驱动，至少部分地，减少深水通风较高的呼吸碳水平。然而，在我们的网站上观察到的末次大冰期和全新世[CO 32-]之间的差异相对较小，与来自整个太平洋的其他记录一致，这表明一种抵消机制，如海底碳酸盐溶解，也发挥了作用。如果是这样的话，这种机制将增加海洋的平均碱度，使更多的大气二氧化碳被海洋隔离。因此，在末次冰期期间，太平洋深海很可能储存了大量的大气CO2，特别是由于更有效的生物碳泵和平均海洋碱度的增加。
It has been shown that the deep Eastern Equatorial Pacific (EEP) region was poorly ventilated during the Last Glacial Maximum (LGM) relative to Holocene values. This finding suggests a more efficient biological pump, which indirectly supports the idea of increased carbon storage in the deep ocean contributing to lower atmospheric CO2 during the last glacial. However, proxies related to respired carbon are needed in order to directly test this proposition. Here we present Cibicides wuellerstorfi B/Ca ratios from Ocean Drilling Program Site 1240 measured by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) as a proxy for deep water carbonate saturation state ([CO32-], and therefore [CO32-]), along with C-13 measurements. In addition, the U/Ca ratio in foraminiferal coatings has been analyzed as an indicator of oxygenation changes. Our results show lower [CO32-], C-13, and [O-2] values during the LGM, which would be consistent with higher respired carbon levels in the deep EEP driven, at least in part, by reduced deep water ventilation. However, the difference between LGM and Holocene [CO32-] observed at our site is relatively small, in accordance with other records from across the Pacific, suggesting that a counteracting mechanism, such as seafloor carbonate dissolution, also played a role. If so, this mechanism would have increased average ocean alkalinity, allowing even more atmospheric CO2 to be sequestered by the ocean. Therefore, the deep Pacific Ocean very likely stored a significant amount of atmospheric CO2 during the LGM, specifically due to a more efficient biological carbon pump and also an increase in average ocean alkalinity.