Description:
<jats:p>The Earth's Dole effect describes the isotopic <jats:sup>18</jats:sup>O/<jats:sup>16</jats:sup>O‐enrichment of atmospheric oxygen with respect to ocean water, amounting under today's conditions to 23.5‰. We have developed a model of the Earth's Dole effect by combining the results of three‐dimensional models of the oceanic and terrestrial carbon and oxygen cycles with results of atmospheric general circulation models (AGCMs) with built‐in water isotope diagnostics. We obtain a range from 22.4‰ to 23.3‰ for the isotopic enrichment of atmospheric oxygen. We estimate a stronger contribution to the global Dole effect by the terrestrial relative to the marine biosphere in contrast to previous studies. This is primarily caused by a modeled high leaf water enrichment of 5–6‰. Leaf water enrichment rises by ∼1‰ to 6–7‰ when we use it to fit the observed 23.5‰ of the global Dole effect. The present model is designed to be utilized in forthcoming paleo studies allowing a quantitative analysis of long‐term observations from polar ice cores.</jats:p>