Transient Carbon Cycle Evolution in Response to Neogene tectonics

Although the silicate weathering feedback is considered to be the only process able to act as a stabilizing thermostat on long time-scales, other carbon fluxes are relevant for perturbing Earth's climate on multi-million years time-scales, especially in relation to Cenozoic orogeneses. Continental biospheric carbon export to the ocean, oxidative weathering of petrogenic carbon, and carbonate and silicate weathering by sulfuric acid from pyrite oxidation have been argued to produce carbon fluxes that are similar in magnitude to that produced from silicate weathering. Furthermore, these fluxes have also been argued to have a higher sensitivity to continental erosion. However, these processes also affect the ocean-atmosphere oxygen and sulfur cycles, both of these elements have much longer residence times in the surface reservoir than carbon. Thus, a perturbation in these fluxes triggers "medium" time-scale (millions to tens of million years) oxygen or sulfur imbalances that carbon needs to cope with in order to find its own equilibrium, owing to its shorter response time (a few hundreds of thousand years). For instance, a sustained CO ₂ source from petrogenic carbon oxidation should trigger a rise in silicate weathering, until organic carbon burial balances the oxygen cycle again; sulfuric weathering delivers calcium to the ocean without alkalinity to precipitate it as carbonate... Determining what steady state climate will be reached as a result of these combined processes is not straightforward.We used the GEOCLIM geochemical model, with spatially-resolved continental fluxes, to investigate the role of the emergence of the Southeast Asian Islands on oxygen and carbon sources and sinks, and on the transient evolution of ocean-atmosphere geochemistry. We also performed an idealized experiment with varying global erosion rates.