Large changes in climate and Carbone cycle from Neoproterozoic to paleozoic: A modelling approach

The link between changes in greenhouse gas in atmosphere and climate are heavily studied at different timescales. More specifically the link between carbon cycle and global glaciation during Neoproterozoic associated with tectonics and carbon burial in the deep ocean has recently been pointed out through carbone/climate modeling (Donnadieu et al 2004, Ramstein eal 2005). Moreover the escape of a snowball, the threshold in atmospheric CO2 (Pierrehumbert2004) and the large shifts of C13 occuring at he end of Neoproterozoic have also been investigated through modeling studies (LeHir et al 2005) and link with biological evolution (Kirshvink et al 2003). The drastic events correponding to Earth deglaciation are associated with large pulses of dc13 that may be produced by clathrate burst due either to deep water warming or transgressive regressive phases. Concerning more regional and recent glacial episodes of Paleozoic, it has been shown that major disturbances of carbon cycle has led these glaciations (Ordovician and Permo-Carboniferous episodes). These changes leading to the formation of carbonate plateforms preceeds the Ordovician glaciation or changes in alteration due to biosphere evolution on continents (Permo-Carboniferous). Our aim is to show how large perturbations of atmospheric greenhouse gas may produce large global glaciation using Carbon/climate models and to understand how carbon cycle perturbation leading and lagging glaciation may be explained.