Massive and Rapid Predominantly Volcanic CO2 Emission During the End-Permian Mass Extinction - 2021

Climate Change, Anthropocene, & Associated Issues

Cui, and 4 co-authors, reported in mid-September, 2021 that the end-Permian mass extinction event (ca. 252 Mya) is the most-severe biodiversity loss in Earth’s history and is globally recognized by a rapid negative carbon isotope excursion. The trigger of this event, however, remains controversial. New paired terrestrial and marine compound-specific carbon isotope records may provide clues for this enigma. By comparing observed data to results from an isotope-enabled Earth system model, the authors found that a massive and rapid, predominantly volcanic CO₂ emission during the Siberian Traps volcanism is likely the trigger for the carbon isotope excursion and the severe mass extinction. Their findings provide quantitative constraints of how a massive and rapid increase in CO₂ may have influenced the marine ecosystem 252 Mya.

The end-Permian mass extinction event (∼252 Mya) is associated with one of the largest global carbon cycle perturbations in the Phanerozoic and is thought to be triggered by the Siberian Traps volcanism. Sizable carbon isotope excursions (CIEs) have been found at numerous sites around the world, suggesting massive quantities of ¹³C-depleted CO₂ input into the ocean and atmosphere system. The exact magnitude and cause of the CIEs, the pace of CO₂ emission, and the total quantity of CO₂, however, remain poorly known. Here, we quantify the CO₂ emission in an Earth system model based on new compound-specific carbon isotope records from the Finnmark Platform and an astronomically tuned age model.

By quantitatively comparing the modeled surface ocean pH and boron isotope pH proxy, a massive (∼36,000 Gt C) and rapid emission (∼5 Gt C yr⁻¹) of largely volcanic CO₂ source (∼−15%) is necessary to drive the observed pattern of CIE, the abrupt decline in surface ocean pH, and the extreme global temperature increase. This suggests that the massive amount of greenhouse gases may have pushed the Earth system toward a critical tipping point, beyond which extreme changes in ocean pH and temperature led to irreversible mass extinction. The comparatively amplified CIE observed in higher plant leaf waxes suggests that the surface waters of the Finnmark Platform were likely out of equilibrium with the initial massive centennial-scale release of carbon from the massive Siberian Traps volcanism, supporting the rapidity of carbon injection. The authors' modeling work revealed that carbon emission pulses are accompanied by organic carbon burial, facilitated by widespread ocean anoxia.