A globally aggregated reconstruction of cycles of carbon and its isotopes

Abstract

A globally aggregated model of the carbon cycle with an upwelling/diffusion ocean and a 6-box biosphere is developed to consistently reconstruct the carbon cycle and isotopic variation in the atmosphere and oceans. The calculated atmospheric δ¹³C trend, based on a model that reproduces the CO₂ concentration record, agrees well with the observed ice core and tree-ring δ¹³C records. The model has also been used to estimate the δ¹³C of oceanic dissolved inorganic carbon, and our model results match observations well within the range of observational uncertainty. This model is found to also match measured values (within measurement error) of the pre-bomb decrease in ¹⁴C in the atmosphere and the mixed layer due to the Suess Effect, the bomb-¹⁴C in the mixed layer, the bomb-¹⁴C penetration depth, the bomb-¹⁴C ocean inventory, and the vertical distribution of total dissolved carbon and ¹⁴C. In addition, the model is used to close the balance between the rates of increase of global inventory and of bomb production of radiocarbon. Our confidence in both the global aggregation of data and our understanding of global carbon cycle is strengthened by the consistency between carbon isotope concentration data and model results.