Millennial-scale atmospheric CO2 variations during the Marine Isotope Stage 6 period (190–135 ka)

• Published in: Climate of the Past
• Main Authors: Shin, Jinhwa, Nehrbass-Ahles, Christoph, Grilli, Roberto, Chowdhry Beeman, Jai, Parrenin, Frédéric, Teste, Grégory, Landais, Amaelle, Schmidely, Loïc, Silva, Lucas, Schmitt, Jochen, Bereiter, Bernhard, Stocker, Thomas F., Fischer, Hubertus, Chappellaz, Jérôme
• Format: Text
• Language: English
• Published: 2020
• Subjects: Antarctic; The Antarctic; Antarc*; EPICA; ice core; North Atlantic
• Online Access: https://doi.org/10.5194/cp-16-2203-2020; https://cp.copernicus.org/articles/16/2203/2020/

Using new and previously published CO 2 data from the EPICA Dome C ice core (EDC), we reconstruct a new high-resolution record of atmospheric CO 2 during Marine Isotope Stage (MIS) 6 (190 to 135 ka) the penultimate glacial period. Similar to the last glacial cycle, where high-resolution data already exists, our record shows that during longer North Atlantic (NA) stadials, millennial CO 2 variations during MIS 6 are clearly coincident with the bipolar seesaw signal in the Antarctic temperature record. However, during one short stadial in the NA, atmospheric CO 2 variation is small ( ∼5 ppm) and the relationship between temperature variations in EDC and atmospheric CO 2 is unclear. The magnitude of CO 2 increase during Carbon Dioxide Maxima (CDM) is closely related to the NA stadial duration in both MIS 6 and MIS 3 (60–27 ka). This observation implies that during the last two glacials the overall bipolar seesaw coupling of climate and atmospheric CO 2 operated similarly. In addition, similar to the last glacial period, CDM during the earliest MIS 6 show different lags with respect to the corresponding abrupt CH 4 rises, the latter reflecting rapid warming in the Northern Hemisphere (NH). During MIS 6i at around 181.5± 0.3 ka, CDM 6i lags the abrupt warming in the NH by only 240± 320 years. However, during CDM 6iv ( 171.1± 0.2 ka) and CDM 6iii ( 175.4± 0.4 ka) the lag is much longer: 1290± 540 years on average. We speculate that the size of this lag may be related to a larger expansion of carbon-rich, southern-sourced waters into the Northern Hemisphere in MIS 6, providing a larger carbon reservoir that requires more time to be depleted.