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

Abstract

Abstract. Using new and previously published CO2 data from the EPICA Dome C ice core (EDC), we reconstruct a new high-resolution record of atmospheric CO2 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 CO2 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 CO2 variation is small (∼5 ppm) and the relationship between temperature variations in EDC and atmospheric CO2 is unclear. The magnitude of CO2 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 CO2 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 CH4 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.

The speleothem oxygen record as a proxy for thermal or moisture changes: a case study of multiproxy records from MIS 5–MIS 6 speleothems from the Demänová Cave system

“…However, this explanation also leads to dryer conditions (Frisia, 2015). New data revealing CO 2 concentration changes during MIS 6 (Shin et al, 2020) show a local minimum CO 2 concentration between 142 and 138 ka. Therefore, the episode recorded in the JS9 stalagmite may be global in nature.…”

“…The DCS is located in a transitional climate zone between oceanic and continental climates (Sotak and Borsanyi, 2004;Kottek et al, 2006). There are two meteorological stations near the DCS: the first is located in the township of Liptovský Mikuláš close to the Demänovská valley entrance (49.07 • N, 19.61 • E; 570 m a.s.l.…”

Laser-induced sublimation extraction for centimeter-resolution multi-species greenhouse gas analysis on ice cores

“…CO 2 measurements are typically performed using mechanical extraction devices (crushing, milling, grating, etc.) combined with either optical gas analyzers (e.g., near-infrared (NIR) or laser spectroscopy) or gas chromatography (GC) (Lüthi et al, 2010;Bereiter et al, 2013;Marcott et al, 2014;Nehrbass-Ahles et al, 2020;Shin et al, 2020). The Bern cracker, Grenoble mill, or the Bern Centrifugal Ice Microtome (CIM) achieve a vertical sample size of 2-5 cm (corresponding to as low as 15 g of ice).…”

Insolation evolution and ice volume legacies determine interglacial and glacial intensity

“…(c) Caloric summer half-year insolation at 65 • N (orange) and at 65 • S (grey) based on the orbital solution of Laskar et al (2004). (d) Compilation of atmospheric CO 2 records from Antarctic ice cores (Bereiter et al, 2015, and references therein;Shin et al, 2020;Bauska et al, 2021). (e) EPICA Dome C sea salt Na flux, a proxy for sea ice extent (Wolff et al, 2006).…”