Enhanced carbon dioxide outgassing from the eastern Equatorial Atlantic during the last glacial

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doi: 10.1130/G35806.1
Author(s): Foster, G. L.; Sexton, P. F.
Author Affiliation(s): Primary:
University of Southampton, National Oceanography Centre, Southampton, United Kingdom
Other:
Open University, United Kingdom
Volume Title: Geology (Boulder)
Source: Geology (Boulder), 42(11), p.1003-1006. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613 CODEN: GLGYBA
Note: In English. 36 refs.; illus.
Summary: Biological productivity and carbon export in the equatorial Atlantic are thought to have been dramatically higher during the last glacial period than during the Holocene. Here we reconstruct the pH and CO2 content of surface waters from the eastern equatorial Atlantic Ocean over the past ∼30 k.y. using the boron isotope composition of Globigerinoides ruber (a mixed-layer-dwelling planktic foraminifera). Our new record, combined with previously published data, indicates that during the last glacial, in contrast to today, a strong west to east gradient existed in the extent of air:sea equilibrium with respect to pCO2 (ΔpCO2), with the eastern equatorial Atlantic acting as a significant source of CO2 (+100 µatm) while the western Atlantic remained close to equilibrium (+25 µatm). This pattern suggests that a fivefold increase in the upwelling rate of deeper waters drove increased Atlantic productivity and large-scale regional cooling during the last glacial, but the higher than modern ΔpCO2 in the east indicates that export production did not keep up with enhanced upwelling of nutrients. However, the downstream decline of ΔpCO2 provides evidence that the unused nutrients from the east were eventually used for biologic carbon export, thereby effectively negating the impact of changes in upwelling on atmospheric CO2 levels. Our findings indicate that the equatorial Atlantic exerted a minimal role in contributing to lower glacial-age atmospheric CO2.
Year of Publication: 2014
Research Program: ODP Ocean Drilling Program
Key Words: 03 Geochronology; 24 Surficial Geology, Quaternary Geology; Absolute age; Alkaline earth metals; Atlantic Ocean; B-11/B-10; Boron; C-14; Calcium; Carbon; Carbon dioxide; Caribbean Sea; Cenozoic; Chemostratigraphy; Chronostratigraphy; Colombian Basin; Cores; Eastern Equatorial Atlantic; Equatorial Atlantic; Foraminifera; Invertebrata; Isotopes; Late-glacial environment; Leg 165; Magnesium; Marine sediments; Metals; Mg/Ca; Microfossils; North Atlantic; ODP Site 999; Ocean Drilling Program; PH; Paleo-oceanography; Protista; Quaternary; Radioactive isotopes; Reconstruction; Sea-surface temperature; Sediments; Stable isotopes; Upper Quaternary; Upwelling
Coordinates: N124437 N124437 W0784422 W0784422
Record ID: 2014105178
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