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Changes in the atmospheric helium isotope ratio over the past 40 years
Author(s) -
Lupton J.,
Evans L.
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2013gl057681
Subject(s) - helium , isotopes of helium , isotope , atmospheric sciences , environmental science , pacific ocean , isotopic ratio , oceanography , geology , physics , nuclear physics , atomic physics
We have compared the helium isotope ratio in five samples of Pacific marine air spanning the 40 year period between 1973 and 2013 against a secondary gas standard. In a separate experiment we directly compared the 3 He/ 4 He ratio in air samples collected in 1973 and 2013 at the same location in La Jolla, California, eliminating any geographical bias. Both experiments are consistent with zero time rate of change for atmospheric 3 He/ 4 He. Our best estimate for the rate of change of the 3 He/ 4 He ratio in Pacific marine air is −0.0014 ± 0.0045%/yr (2 σ ), indicating that air helium is still a valid standard for terrestrial helium isotope measurements.