Allan Hills CMC3 ice core d18Oatm, d15N, dO2/N2, dAr/N2, d40/36Ar, d40/38Ar 2021 & 2022

These data cover the penultimate glacial period (MIS 6) and parts of MIS5, in Allan Hills ice. The d18Oatm data are useful for dating the core, and the 15N is useful for inferring firn thickness. Importantly, the data have only been corrected for gas loss using published methods (i.e. Baggenstos et al. 2017), but not for recently recognized (and unpublished) effects of declining contemporary atmospheric O2/N2 due to fossil fuel burning. These changes unfortunately affect the La Jolla Air standard gas O2/N2 ratio that is used in our lab to make the measurements. Users of this data are encouraged to contact Jeff Severinghaus for help in making these novel corrections to the standard gas.