Carbon isotope composition of atmospheric CO2 during the last ice age from an Antarctic ice core ...

• Main Authors: Leuenberger, Markus, Siegenthaler, Urs, Langway, Chester C.
• Format: Text
• Language: unknown
• Published: Macmillan Journals Ltd. 1992
• Subjects: 530 Physics; Antarctic; Byrd; Byrd Station; Antarc*; Antarctica; ice core
• Online Access: https://dx.doi.org/10.48350/158241; https://boris.unibe.ch/158241/

Bubbles of ancient air in polar ice cores have revealed that the atmospheric concentration of CO2 during the Last Glacial Maximum was 180–200 p.p.m.v., substantially lower than the pre-industrial value of about 280 p.p.m.v. (refs 1, 2). It is generally thought that this reduction in atmospheric CO2 during glacial time was driven by oceanic processes. The most likely explanations invoke either a decrease in dissolved CO2 in surface waters because of a more efficient 'biological pump' transporting carbon to deep waters, or a higher alkalinity in the glacial ocean as a consequence of changes in carbonate dissolution or sedimentation3. Because isotope fractionation during photosynthesis depletes 13C in the organic matter produced, changes in the biological pump would alter the carbon isotope composition of atmospheric CO2, whereas changes in alkalinity would in themselves have no such effect. Here we report measurements of the carbon isotope content of CO2 in ice cores from Byrd Station, Antarctica, in an ...