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Southern Ocean link between changes in atmospheric CO2 levels and northern-hemisphere climate anomalies during the last two glacial periods

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Gottschalk Julia, Skinner Luke C., Jaccard Samuel L., Menviel Laurie, Nehrbass-Ahles Christoph, Waelbroeck Claire,
Project SeaO2 - Past changes in Southern Ocean overturning circulation - implications for the partitioning of carbon and oxygen between the ocean and the atmosphere
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Original article (peer-reviewed)

Journal Quaternary Science Reviews
Volume (Issue) 230
Page(s) 106067 - 106067
Title of proceedings Quaternary Science Reviews
DOI 10.1016/j.quascirev.2019.106067

Abstract

Past millennial-scale changes in atmospheric CO2 (CO2,atm) concentrations have often been attributed to variations in the overturning timescale of the ocean that result in changes in the marine carbon in- ventory. Yet, there remains a paucity of proxy evidence that documents changes in marine carbon storage globally, and that links them to abrupt climate variability in the northern hemisphere associated with perturbations of the Atlantic Meridional Overturning Circulation (AMOC). The last two glacial periods were suggested to differ in the spatial extent of the AMOC and its sensitivity to perturbations. This provides an opportunity to compare the nature of marine carbon cycle-climate feedbacks between them. Here, we reconstruct variations in respired carbon storage (via oxygenation) and the AMOC “geometry” (via carbonate ion saturation) in the deep South Atlantic. We infer decreases in deep South Atlantic respired carbon levels at times of weakened AMOC and rising CO2,atm concentrations during both glacial periods. These findings suggest a consistent pattern of increased Southern Ocean convection and/or air- sea CO2 fluxes during northern-hemisphere stadials accompanying AMOC perturbations and promoting a rise in CO2,atm levels. We find that net ocean carbon loss, and hence the magnitude of CO2,atm rise, is largely determined by the stadial duration. North Atlantic climate anomalies therefore affect Southern Ocean carbon cycling in a consistent manner, through oceanic (e.g., ventilation seesaw) and/or atmo- spheric processes (e.g., Ekman pumping).
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