Global carbon cycle perturbation across the Eocene-Oligocene climate transition

摘要: The Eocene-Oligocene transition (EOT), ~34?Ma, marks a tipping point in the long-term Cenozoic greenhouse to icehouse climate transition. Paleorecords reveal stepwise rapid cooling and ice growth across EOT tightly coupled transient benthic ?13C excursion major permanent deepening of carbonate compensation depth (CCD). Based on biogeochemical box modeling, Merico et al. (2008) suggested that combination (1) glacioeustatic sea level fall-induced shelf-basin burial fractionation (2) shelf weathering can account for carbon cycle perturbation, but this finding has been questioned. Alternative proposed mechanisms include increased ocean ventilation, decreased burial, organic silicate weathering, calcium concentration. Here we use an improved version model reevaluate these competing hypotheses additional mechanism, expansion “carbon capacitors” such as permafrost peatlands. We find changes concentration, or each yield response is fundamentally at odds with form and/or sign paleorecords. Shelf-basin (CCD change), plus sequestration 12C-enriched into capacitors, possibly ventilation (?13C excursion), offers best fit Further work needed understand why perturbation so unique when forcing hypothesized be responsible (cooling growth) are not peculiar event.