Talk by Prof. Thomas Blunier – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > Activities 2013 > Talk by Prof. Thomas B...

Talk by Prof. Thomas Blunier

What can we learn from triple oxygen isotopes of atmospheric oxygen?

About a paper published recently in Climate of the Past

The oxygen cycle in the atmosphere is quite complex. Ultimately
atmospheric oxygen originates from seawater. It gets into the atmosphere
through photosynthesis and is consumed by respiration. Isotope wise
these processes are so called mass dependent where d^17 O fractionates
about half as much as d^18 O. This is also true, in essence, for the
hydrological cycle which affects the isotopic signature of oxygen
produced through the terrestrial biosphere. An "anomalous" (also termed
mass independent) fractionation process changes d^17 O about 1.7 times
as much as d^18 O during isotope exchange between O_2 and CO_2 in the
stratosphere. The relative rates of biological O_2 production and
stratospheric processing determine the relationship between d^17 O and
d^18 O of O_2 in the atmosphere. Variations of this relationship,
measured in ice cores, thus allow us to estimate changes in the rate of
O_2 production by photosynthesis versus the rate of O_2 -CO_2 isotope
exchange in the stratosphere.