Multiple carbon cycle mechanisms associated with the glaciation of Marine Isotope Stage 4

• Published in: Nature Communications
• Main Authors: Menking, James A., Shackleton, Sarah A., Bauska, Thomas K., Buffen, Aron M., Brook, Edward J., Barker, Stephen, Severinghaus, Jeffrey P., Dyonisius, Michael N., Petrenko, Vasilii V.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Research 2022
• Subjects: Southern Ocean; North Atlantic
• Online Access: http://nora.nerc.ac.uk/id/eprint/533234/; https://nora.nerc.ac.uk/id/eprint/533234/1/s41467-022-33166-3.pdf; https://www.nature.com/articles/s41467-022-33166-3

Here we use high-precision carbon isotope data (δ13C-CO2) to show atmospheric CO2 during Marine Isotope Stage 4 (MIS 4, ~70.5-59 ka) was controlled by a succession of millennial-scale processes. Enriched δ13C-CO2 during peak glaciation suggests increased ocean carbon storage. Variations in δ13C-CO2 in early MIS 4 suggest multiple processes were active during CO2 drawdown, potentially including decreased land carbon and decreased Southern Ocean air-sea gas exchange superposed on increased ocean carbon storage. CO2 remained low during MIS 4 while δ13C-CO2 fluctuations suggest changes in Southern Ocean and North Atlantic air-sea gas exchange. A 7 ppm increase in CO2 at the onset of Dansgaard-Oeschger event 19 (72.1 ka) and 27 ppm increase in CO2 during late MIS 4 (Heinrich Stadial 6, ~63.5-60 ka) involved additions of isotopically light carbon to the atmosphere. The terrestrial biosphere and Southern Ocean air-sea gas exchange are possible sources, with the latter event also involving decreased ocean carbon storage.