Radiocarbon (14C) as a tracer for understanding carbon cycling in the earth system

Abstract

Understanding the response of the global carbon cycle to anthropogenic emissions requires information not only on carbon budgets but also on independent observational limits on the rates at which carbon is exchanged among reservoirs. This review integrates simplified box‐model representations with radiocarbon (14C) observations to evaluate carbon exchange dynamics across the atmosphere, terrestrial biosphere, and oceans. Particular focus is placed on the atmospheric 14C “bomb spike,” which provides a time‐resolved tracer of system‐level adjustment following a known perturbation. Analysis of post‐1963 atmospheric radiocarbon decline demonstrates that rapid gross carbon exchange can coexist with long atmospheric adjustment times, underscoring the distinction between molecular turnover and reservoir‐scale carbon removal. Radiocarbon evidence further indicates that terrestrial and oceanic sinks primarily act as dynamic buffers rather than permanent sequestration pathways on decadal timescales. By combining mass‐balance logic with isotopic constraints, this work highlights the essential role of tracer‐based approaches in resolving ambiguities inherent in bulk‐carbon‐only analyses and in strengthening interpretations of contemporary carbon‐cycle behavior under sustained anthropogenic forcing.