Millennial-scale atmospheric CO 2 variations during the Marine Isotope Stage 6 period (190–135 ka)

• Published in: Climate of the Past
• Main Authors: J. Shin, C. Nehrbass-Ahles, R. Grilli, J. Chowdhry Beeman, F. Parrenin, G. Teste, A. Landais, L. Schmidely, L. Silva, J. Schmitt, B. Bereiter, T. F. Stocker, H. Fischer, J. Chappellaz
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2020
• Subjects: Environmental pollution; TD172-193.5; Environmental protection; TD169-171.8; Environmental sciences; GE1-350; Antarctic; The Antarctic; Antarc*; EPICA; ice core; North Atlantic
• Online Access: https://doi.org/10.5194/cp-16-2203-2020; https://doaj.org/article/379f5fb57a4a421d924853aa240c4af9

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.