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

• Published in: Quaternary Science Reviews
• Main Authors: Yu, JM (Yu, Jimin) 1, Anderson, RF (Anderson, Robert F.) 2, Jin, ZD (Jin, Zhangdong) 3, Rae, JWB (Rae, James W. B.) 4, Opdyke, BN (Opdyke, Bradley N.) 1, Eggins, SM (Eggins, Stephen M.) 1
• Format: Report
• Language: English
• Published: 2013
• Subjects: Deep Ocean Carbonate Ion; Global Carbon Cycle; B/ca; Carbonate Compensation; Ocean Stratification; Pleistocene; Pacific; North Atlantic
• Online Access: http://ir.ieecas.cn/handle/361006/10041; https://doi.org/10.1016/j.quascirev.2013.06.020

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 similar to 65 mu mol/kg in the deep Caribbean Basin, deep water [CO32-] in the equatorial Pacific Ocean has varied by no more than similar to 15 mu mol/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 similar to 7 mu mol/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 similar to 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 delta C-13 in the same cores, at the start and end of MIS 4. These changes in [CO32-] and delta C-13 are consistent with what would be expected from vertical nutrient fractionation and carbonate compensation. The observed similar to 4 mu mol/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 Th-230-normalized CaCO3 flux at two adjacent sites from the central equatorial Pacific Ocean provides convincing evidence that ...