Calcium and calcium isotope changes during carbon cycle perturbations at the end-Permian

Negative carbon and calcium isotope excursions, as well as cli-1 mate shifts, took place during the most severe mass extinction event in Earth's 2 history, the end-Permian (∼252 Ma). Investigating the connection between 3 carbon and calcium cycles during transient carbon cycle perturbation events, 4 such as the end-Permian, may help resolve the intricacies between the cou-5 pled calcium-carbon cycles, as well as provide a tool for constraining the causes 6 of mass extinction. Here, we identify the deficiencies of a simplified calcium 7 model employed in several previous studies and we demonstrate the impor-8 tance of a fully coupled carbon-cycle model when investigating the dynam-9 ics of carbon and calcium cycling. Simulations with a modified version of the 10 LOSCAR model, which includes a fully coupled carbon-calcium cycle, indi-11 cate that increased weathering rates and ocean acidification (potentially caused 12 by Siberian Trap volcanism) are not capable of producing trends observed 13 in the record, as previously claimed. Our model results suggest that com-14 bined effects of carbon input via Siberian Trap volcanism (12,000 Pg C), the 15 cessation of biological carbon export, and variable calcium isotope fraction-16 ation (due to a change in the seawater carbonate ion concentration) repre-17 sents a more plausible scenario. This scenario successfully reconciles δ 13 C and 18 δ 44 Ca trends observed in the sediment record, as well as the proposed warm-19 ing of >6 o C.