MEASUREMENTS OF CO2 AND CH4 CONCENTRATIONS IN AIR IN A POLAR ICE CORE

Dry and wet air-extraction systems and precise analysis systems of the CO2 and CH4 concentrations for a polar ice core were developed to reconstruct their ancient levels. A dry-extraction system was capable of crushing an ice sample of 1000 g into fine powder within 2 min, and its air-extraction efficiency was found to be 98%. The CO2 and CH4 concentrations of extracted air were determined using gas chromatography with a flame-ionized detector. The overall precision of our measurements, including air extraction, was estimated to be better than +/- 1 ppmv for CO2 and +/- 10 ppbv for CH4. Preliminary analysis of the ice core drilled at Mizuho Station, Antarctica, showed that the CO2 and CH4 concentrations at 3340-3700 year BP were about 280 ppmv and 700 ppbv, respectively. The Yamato core drilled at the terminus of the glacial flow near the Yamato Mountains, Antarctica, yielded concentrations of 230-240 ppmv for CO2 and 520-550 ppbv for CH4, suggesting that the core had formed during the glacial period.