This data set contains results from a study of the triple isotope composition
of atmospheric O2, obtained by analysis of the GISP2 and Siple Dome ice cores.
Results are expressed as D17O, where
D17O = [d17O - 0.521 d18O] x 1000.
The primary application of the data is in reconstructing the past rates of
planetary productivity. In most physical and chemical processes, 17O is
fractionated ... approximately 0.521 times as fast as 18O, and D17O is constant.
However in the stratosphere, there is an isotope exchange reaction between O2
and CO2 in which 17O is fractionated approximately 1.7 times as much as 18O
rather than 0.521 times as much. Consequently, D17O of atmospheric O2 is
different from zero, with seawater (SMOW) as the standard. The magnitude of
the fractionation depends on the relative rates of photochemically-indeuced
stratospheric exchange, and biological productivity. Constraining the former
allows the fertility of the planet to be estimated.
Results are expressed with atmospheric O2 as the standard, rather than SMOW.
Results are expressed in units of per meg, where 1 per meg = 0.001 per mil.