Using the Suess effect on the stable carbon isotope to distinguish the future from the past in radiocarbon

Abstract

The depletion of ^14 C due to the emission of radiocarbon-free fossil fuels ( ^14 C Suess effect) might lead to similar values in future and past radiocarbon signatures potentially introducing ambiguity in dating. I here test if a similar impact on the stable carbon isotope via the ^13 C Suess effect might help to distinguish between ancient and future carbon sources. To analyze a wide range of possibilities, I add to future emission scenarios carbon dioxide reduction (CDR) mechanisms, which partly enhance the depletion of atmospheric ${{\rm{\Delta }}}^{14}{\rm{C}}$ already caused by the ^14 C Suess effect. The ^13 C Suess effect leads to unprecedented depletion in ${\delta }^{13}{\rm{C}}$ shifting the carbon cycle to a phase space in ${{\rm{\Delta }}}^{14}{\rm{C}}\mbox{--}{\delta }^{13}{\rm{C}}$ , in which the system has not been during the last 50 000 years and therefore the similarity in past and future ${{\rm{\Delta }}}^{14}{\rm{C}}$ (the ambiguity in ^14 C dating) induced by fossil fuels can in most cases be overcome by analyzing ^13 C. Only for slow changing reservoirs (e.g. deep Indo-Pacific Ocean) or when CDR scenarios are dominated by bioenergy with capture and storage the effect of anthropogenic activities on ^13 C does not unequivocally identify between past and future carbon cycle changes.

Keywords

• carbon cycle
• future CO2 emissions
• carbon isotopes
• radiocarbon dating
• Suess effect
• modeling