Methane and carbon dioxide measured on the Vostok ice core

CO2 and CH4 measurements have been performed using the methods and analytical procedures previously described (Barnola et al., 1987, Chappellaz et al, 1990). However, the CO2 measuring system has been slightly modified in order to increase the sensitivity of the CO2 detection. The thermal conductivity chromatographic detector has been replaced by a flame ionisation detector which measures CO2 after its transformation into CH4. The overall accuracy for CH4 and CO2 measurements are ± 20 ppbv and 2-3 ppmv respectively. No gravitational correction has been applied.