Responses of the deep ocean carbonate system to carbon reorganization during the last glacial-interglacial cycle

• Published in: Quaternary Science Reviews
• Main Authors: Yu, J, Anderson, R. F., Jin, Z., Rae, James William Buchanan, Opdyke, B. N., Eggins, S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2013
• Subjects: North Atlantic
• Online Access: https://research-portal.st-andrews.ac.uk/en/researchoutput/responses-of-the-deep-ocean-carbonate-system-to-carbon-reorganization-during-the-last-glacialinterglacial-cycle(e036abaa-e881-442d-a242-f027c7f59447).html; https://doi.org/10.1016/j.quascirev.2013.06.020; http://www.sciencedirect.com/science/article/pii/S0277379113002400

We present new deep water carbonate ion concentration ([CO32−]) 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 [CO32−] in the Caribbean Basin roughly mirrors that of atmospheric CO2, reflecting a dominant influence from preformed [CO32−] in the North Atlantic Ocean. Compared to the amplitude of ∼65 μmol/kg in the deep Caribbean Basin, deep water [CO32−] in the equatorial Pacific Ocean has varied by no more than ∼15 μmol/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 [CO32−] between the Last Glacial Maximum (LGM) and the Late Holocene. The three records from the Pacific Ocean show long-term increases in [CO32−] by ∼7 μmol/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 [CO32−] in the Pacific Ocean displays transient changes, which decouple with δ13C in the same cores, at the start and end of MIS 4. These changes in [CO32−] and δ13C are consistent with what would be expected from vertical nutrient fractionation and carbonate compensation. The observed ∼4 μmol/kg [CO32−] 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 [CO32−] 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 ...