FY 2004 The atmospheric helium isotope ratio: Is it changing? Lupton, J., and L. Evans Geophys. Res. Lett., 31, L13101, doi: 10.1029/2004GL020041 (2004) We have compared the helium isotope ratio of samples of Pacific marine air collected over the 30-year period from 1973 to 2003 against a secondary geothermal gas standard and also against a running air standard. The results are consistent with zero rate of change for atmospheric He/He. When the errors are taken into account, the rate of change in the air He/He ratio is between -0.0102 and +0.0019 %/year. At the most this corresponds to a 0.3% change in the air He/He ratio over the past 3 decades, which is at or below the detection limit of most laboratories. While there may be a small decrease in air He/He due to anthropogenic release of He associated with use of fossil fuels, this decrease is not large enough to prevent the use of air helium as an isotopic standard. Feature Publications | Outstanding Scientific Publications Contact Sandra Bigley | Help
