Stable-isotope ratios and concentration of CO2 in air from polar ice cores

• Published in: Annals of Glaciology
• Main Authors: Siegenthaler, U., Friedli, H., Loetscher, H., Moor, E., Neftel, A., Oeschger, H., Stauffer, B.
• Format: Conference Object
• Language: English
• Published: International Glaciological Society 1988
• Subjects: 530 Physics; South Pole; Annals of Glaciology; ice core; South pole
• Online Access: https://boris.unibe.ch/158756/1/stable-isotope-ratios-and-concentration-of-co2-in-air-from-polar-ice-cores.pdf; https://boris.unibe.ch/158756/

Analyses of air trapped in an ice core from the South Pole indicate that the CO2 concentration may have increased by about 10 ppm and that the 13C/12C ratio decreased slightly in the thirteenth century. These changes, if really of atmospheric origin, must be due to a significant input into the atmosphere of CO2, either of biogenic or of oceanic origin. 18O/16O ratios in CO2 from different ice cores are much lower than those which have been observed in atmospheric carbon dioxide. A possible explanation is that the CO2 has equilibrated isotopically with the ice. We have calculated equilibrium isotope-fractionation factors between ice and carbon dioxide and found that the observed 18O/16O ratios of CO2 are indeed near isotopic equilibrium with the ice. This indicates that an exchange of oxygen atoms probably occurs between ice and included CO2.