Responses of the deep ocean carbonate system to carbon reorganization during the Last Glacial-interglacial cycle

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• 作者：Jimin Yu ; Robert F. Anderson ; Zhangdong Jin ; James W.B. Rae ; Bradley N. Opdyke ; Stephen M. Eggins
• 关键词：Deep ocean carbonate ion ; Global carbon cycle ; B/Ca ; Carbonate compensation ; Ocean stratification ; Pleistocene
• 刊名：Quaternary Science Reviews
• 出版年：2013
• 出版时间：15 September, 2013
• 年：2013
• 卷：76
• 期：Complete
• 页码：39-52
• 全文大小：1334 K

文摘

We present new deep water carbonate ion concentration ([CO₃^2?]) records, reconstructed using Cibicidoides wuellerstorfi B/Ca, for one core from Caribbean Basin (water depth?=?3623?m, sill depth?=?1.8?km) and three cores located at 2.3-4.3?km water depth from the equatorial Pacific Ocean during the Last Glacial-interglacial cycle. The pattern of deep water [CO₃^2?] in the Caribbean Basin roughly mirrors that of atmospheric CO₂, reflecting a dominant influence from preformed [CO₃^2?] in the North Atlantic Ocean. Compared to the amplitude of ¡«65?¦Ìmol/kg in the deep Caribbean Basin, deep water [CO₃^2?] in the equatorial Pacific Ocean has varied by no more than ¡«15?¦Ìmol/kg due to effective buffering of CaCO₃ on deep-sea pH in the Pacific Ocean. Our results suggest little change in the global mean deep ocean [CO₃^2?] between the Last Glacial Maximum (LGM) and the Late Holocene. The three records from the Pacific Ocean show long-term increases in [CO₃^2?] by ¡«7?¦Ìmol/kg from Marine Isotope Stage (MIS) 5c to mid MIS 3, consistent with the response of the deep ocean carbonate system to a decline in neritic carbonate production associated with ¡«60?m drop in sea-level (the ¡°coral-reef¡± hypothesis). Superimposed upon the long-term trend, deep water [CO₃^2?] in the Pacific Ocean displays transient changes, which decouple with ¦Ä¹³C in the same cores, at the start and end of MIS 4. These changes in [CO₃^2?] and ¦Ä¹³C are consistent with what would be expected from vertical nutrient fractionation and carbonate compensation. The observed ¡«4?¦Ìmol/kg [CO₃^2?] decline in the two Pacific cores at >3.4?km water depth from MIS 3 to the LGM indicate further strengthening of deep ocean stratification, which contributed to the final step of atmospheric CO₂ drawdown during the last glaciation. The striking similarity between deep water [CO₃^2?] and ²³⁰Th-normalized CaCO₃ flux at two adjacent sites from the central equatorial Pacific Ocean provides convincing evidence that deep-sea carbonate dissolution dominantly controlled CaCO₃ preservation at these sites in the past. Our results offer new and quantitative constraints from deep ocean carbonate chemistry to understand roles of various mechanisms in atmospheric CO₂ changes over the Last Glacial-interglacial cycle.