Air is extracted from bubbles of polar ice samples by a dry extraction method, and the 13C/12C ratio is measured on CO2 separated from the air.

Ice samples of typically 700 g are crushed at ca. -20¿C, the evolving air is trapped cryogenically, and CO2 is frozen out from this air for mass-spectrometric isotope analysis. First Δ13C and Δ18O results of CO2 from Antarctic ice cores are presented, and Δ13C is discussed in relation to atmospheric CO2 variations. Δ13C of 400 to 800 year old ice is ca. 1.1%0 higher than the 1980 atmospheric value, which agrees well with model-biased estimations. The measurement of three ca. 50,000 yr old samples yielded astonishingly low values, but contamination cannot be excluded.