摘要：We describe a high-precision method, now in use in our laboratory, for measuring the CO 2 mixing ratio of ancient air trapped in polar ice cores. Occluded air in ice samples weighing ∼8–15 g is liberated by crushing with steel pins at −35°C and trapped at −263°C in a cryogenic cold trap. CO 2 in the extracted air is analyzed using gas chromatography. Replicate measurements for several samples of high-quality ice from the Siple Dome and Taylor Dome Antarctic ice cores have pooled standard deviations of <0.9 ppm. This high-precision technique is directly applicable to high-temporal-resolution studies for detection of small CO 2 variations, for example CO 2 variations of a few parts per million on millennial to decadal scales.
