Elemental and isotopic composition of occluded O₂ and N₂ in polar ice

We have analysed 13 samples of trapped air in recent (<2200 years B.P.) ice from eight sites. The average δ¹⁵N of N₂ and δ¹⁸O of O₂ in samples from the various ice cores ranged from +0.05 to +0.41 ‰ and from +0.18 to +1.1 ‰, respectively. The heavy isotope enrichments are apparently due to gravitational settling accompanying diffusive equilibrium between the base of the firn and the overlying atmosphere. The δO₂/Ar and δN₂/Ar values ranged from -9.2 to +1.0‰ and from -4.8 to +4.6‰, respectively. The differences between the elemental composition of ice core trapped gases and air result from gravitational fractionation, as well as separation of O₂ and Ar relative to N₂ during either bubble close-off or retrieval and storage of the ice core. -from Authors