A natural artefact in Greenland ice-core CO₂ measurements

Paleoatmospheric concentrations of CO₂ over the last ice ages have been revealed by ice-core analysis. According to the time period (ice age or interglacial) and the hemisphere considered, the ice containing the analysed air bubbles can be either alkaline or acid. It is shown that the interaction between acid and alkaline impurities, when they co-exist naturally in ice, could lead to the production of excess CO₂ in ice samples, and therefore to erroneously-high CO₂ values of no paleoatmospheric significance. The phenomenon is thought to occur only in Greenland ice during climatic transitions. It does not question the low CO₂ levels found in Greenland and Antarctic ice cores for glacial ages.