Reference : On the application and interpretation of Keeling plots in paleo climate research - De...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Earth sciences & physical geography
On the application and interpretation of Keeling plots in paleo climate research - Deciphering δ 13C of atmospheric CO 2 measured in ice cores
Köhler, Peter mailto [Alfred Wegener Institute for Polar and Marine Research - AWI > > > >]
Fischer, Hubertus [Alfred Wegener Institute for Polar and Marine Research - AWI > > > >]
Schmitt, Jochen [Alfred Wegener Institute for Polar and Marine Research - AWI > > > >]
Munhoven, Guy mailto [Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP) - Pétrologie et géochimie endogènes >]
European Geosciences Union
Yes (verified by ORBi)
[en] atmospheric CO2 ; carbon isotopes ; Keeling plot
[en] The Keeling plot analysis is an interpretation method widely used in terrestrial carbon cycle research to quantify exchange processes of carbon between terrestrial reservoirs and the atmosphere. Here, we analyse measured data sets and artificial time series of the partial pressure of atmospheric carbon dioxide (pCO(2)) and of delta C-13 of CO2 over industrial and glacial/interglacial time scales and investigate to what extent the Keeling plot methodology can be applied to longer time scales. The artificial time series are simulation results of the global carbon cycle box model BICYCLE. The signals recorded in ice cores caused by abrupt terrestrial carbon uptake or release loose information due to air mixing in the firn before bubble enclosure and limited sampling frequency. Carbon uptake by the ocean cannot longer be neglected for less abrupt changes as occurring during glacial cycles. We introduce an equation for the calculation of long-term changes in the isotopic signature of atmospheric CO2 caused by an injection of terrestrial carbon to the atmosphere, in which the ocean is introduced as third reservoir. This is a paleo extension of the two reservoir mass balance equations of the Keeling plot approach. It gives an explanation for the bias between the isotopic signature of the terrestrial release and the signature deduced with the Keeling plot approach for long-term processes, in which the oceanic reservoir cannot be neglected. These deduced isotopic signatures are similar (-8.6 parts per thousand) for steady state analyses of long-term changes in the terrestrial and marine biosphere which both perturb the atmospheric carbon reservoir. They are more positive than the delta C-13 signals of the sources, e.g. the terrestrial carbon pools themselves (similar to -25 parts per thousand). A distinction of specific processes acting on the global carbon cycle from the Keeling plot approach is not straightforward. In general, processes related to biogenic fixation or release of carbon have lower y-intercepts in the Keeling plot than changes in physical processes, however in many case they are indistinguishable (e.g. ocean circulation from biogenic carbon fixation).
Fonds de la Recherche Scientifique (Communauté française de Belgique) - F.R.S.-FNRS ; Bundesministerium für Bildung und Forschung Allemagne) - BMBF
Researchers ; Professionals ; Students
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