PMEL Publications Abstract

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.

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