Modeling the carbon-sulfate interplays in climate changes related to the emplacement of continental flood basalts

Climatic and environmental changes are now widely recognized as the main cause of mass extinctions. Global warming that immediately preceded the Cretaceous-Tertiary boundary is regarded as a consequence of CO2 released during the main phase of Deccan Trap emplacement. Modeling has shown that such global warming cannot be explained by the continuous release of volcanic carbon dioxide. In the present paper, we use a biogeochemical model, coupled to a climate model, to further our understanding of climate changes caused by continental flood basalts. The response of the global climate-carbon-cycle system to sulfur dioxide (SO2) and carbon dioxide (CO2) emissions is investigated, assuming a degassing history consisting of a series of evenly spaced pulses. We find that CO2-related warming is enhanced when large-scale SO2 injections are added. According to our model, we observe that the succession of drastic cooling events induced by sulfate aerosols decreases the efficiency of silicate weathering and destabilizes the carbon cycle during the full time span of trap emplacement. In the case of the Deccan Traps, these transient disequilibria lead to a 25% increase in pCO(2) and ensuing warming. The environmental consequences of emplacement of large igneous provinces appear to be even more complex: A SO2-related climate feedback may have enhanced the long-term warming due to CO2 emissions.