High Precision Stable Isotope Measurements of Caribic Aircraft CO2 Samples: Global Distribution and Exchange with the Biosphere

In 2007-2009 JRC-IRMM, in collaboration with the project CARIBIC (Civil Aircraft for Regular Investigation of the atmosphere Based on an Instrument Container, www.caribicatmospheric. com), conducted systematic measurements aimed to study the global distribution of CO2 isotopic composition. A large data set for the upper troposphere-lowermost stratosphere and free troposphere was obtained. For the first time it is demonstrated how CO2 isotope signals reflect global scale variability in air mass origin. Tight correlations observed arise either from stratosphere/troposphere mixing or from mixing of background air and air masses affected by CO2 sources and sinks, over long distances and throughout the seasons. The high quality δ18O(CO2) data prove to be a useful tracer reflecting long range CO2 transport and also CO2 exchange with land biosphere and soils. The data provide a benchmark for future comparisons and are available for modelling studies. (author)