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

• 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: unknown
• Published: eScholarship, University of California 2022
• Subjects: Life Below Water; Carbon; Carbon Cycle; Carbon Dioxide; Carbon Isotopes; Ice Cover; Seawater; Southern Ocean; North Atlantic
• Online Access: https://escholarship.org/uc/item/2vg912kx

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.