The Evolution of Deep Ocean Chemistry and Respired Carbon in the Eastern Equatorial Pacific Over the Last Deglaciation

de la Fuente, M. and Calvo, E and Skinner, L. and Pelejero, C and Evans, D and Müller, W and Povea, P and Cacho, I (2017) The Evolution of Deep Ocean Chemistry and Respired Carbon in the Eastern Equatorial Pacific Over the Last Deglaciation. Paleoceanography, 32. pp. 1371-1385. ISSN 1944-9186 | 0883-8305 DOI https://doi.org/10.1002/2017PA003155

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Abstract

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 CO 2 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 (ΔCO 3 2− , and therefore CO 3 2− ), along with δ 13 C measurements. In addition, the U/Ca ratio in foraminiferal coatings has been analyzed as an indicator of oxygenation changes. Our results show lower CO 3 2− , δ 13 C, 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 CO 3 2− 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 CO 2 to be “sequestered” by the ocean. Therefore, the deep Pacific Ocean very likely stored a significant amount of atmospheric CO 2 during the LGM, specifically due to a more efficient biological carbon pump and also an increase in average ocean alkalinity.

Item Type:	Article
Uncontrolled Keywords:	2018AREP; IA74
Subjects:	01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions:	01 - Climate Change and Earth-Ocean Atmosphere Systems 08 - Green Open Access
Journal or Publication Title:	Paleoceanography
Volume:	32
Page Range:	pp. 1371-1385
Identification Number:	https://doi.org/10.1002/2017PA003155
Depositing User:	Sarah Humbert
Date Deposited:	05 Mar 2018 12:18
Last Modified:	12 Sep 2019 09:40
URI:	http://eprints.esc.cam.ac.uk/id/eprint/4107

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