ON THE CONCENTRATIONS OF O-2, N-2, AND AR IN TRAPPED GASES FROM ICE CORES

We present data on the relative concentration and isotopic composition of O-2, N-2, and Ar in gases trapped in bubbles of polar ice. O-2/N-2 and Ar/N-2 ratios are generally lower than the atmospheric values, wi th O-2 depletions greater than those of Ar. In samples whose O-2/Ar/N- 2 ratios are highly anomalous with respect tb modern air, delta(18)O o f O-2 may be enriched by 0.1-0.2 parts per thousand. There is no indic ation that delta(15)N of N-2 is enriched by gas loss processes in any of the samples we have studied. Out data suggest that anomalies in the composition of air in bubbles with respect to the modern atmosphere a re due to gas loss from ice during and after coring by a process which fractionates elements according to their molecular diameter (Craig et al., 1988) rather than according to their diffusivity.