Changes in South Atlantic oxygenation, surface temperature and circulation dynamics during termination II and MIS 6 (proxy analyses in sediment core MD07-3077)


Past millennial-scale changes in atmospheric CO2 (CO2,atm) levels have often been attributed to variations in the overturning timescale of the ocean that result in changes in the marine carbon inventory. There remains a paucity of proxy evidence that documents changes in marine carbon storage globally, and that links them to distinct abrupt climate variability in the northern hemi-sphere that involve perturbations of the Atlantic Meridional Overturning Circulation (AMOC). The last two glacial periods were suggested to differ in the extent and sensitivity of the AMOC to changes, and therefore provide an opportunity to study their role in marine carbon cycling. Here, we reconstruct variations in respired carbon storage (via oxygenation) and the AMOC 'geometry' (via carbonate ion saturation) in the deep South Atlantic during the past two glacial periods. 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 pat-tern 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, despite potential differences in the magnitude of the forcing, the climate (and hence, AMOC) background conditions and the rate of ocean-atmospheric CO2 fluxes. We find that net ocean car-bon loss, and hence the magnitude of CO2,atm rise, during a glacial is largely determined by the stadial duration. North Atlantic climate anomalies may therefore significantly affect Southern Ocean carbon cycling through oceanic (e.g., 'ventilation' seesaw) and/or atmospheric processes (e.g., Ekman pumping).

Supplement to: Gottschalk, Julia; Skinner, Luke C; Jaccard, Samuel L; Menviel, Laurie; Nehrbass-Ahles, Christoph; Waelbroeck, Claire (2020): Southern Ocean link between changes in atmospheric CO2 levels and northern-hemisphere climate anomalies during the last two glacial periods. Quaternary Science Reviews, 230, 106067

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Metadata Access
Creator Gottschalk, Julia ORCID logo; Skinner, Luke C ORCID logo; Jaccard, Samuel L ORCID logo; Waelbroeck, Claire ORCID logo
Publisher PANGAEA
Publication Year 2019
Rights Creative Commons Attribution 4.0 International;
OpenAccess true
Resource Type Supplementary Publication Series of Datasets; Collection
Format application/zip
Size 4 datasets
Discipline Earth System Research
Spatial Coverage (-14.220 LON, -44.150 LAT)