Climatic fluctuations modeled for carbon and sulfur emissions from end-Triassic volcanism

Throughout the history of complex life, Earth's climate and biogeochemical cycles have been perturbed by Large Igneous Province (LIP) volcanism, with several LIP episodes correlating with major mass extinction events. Yet many aspects of the interplay between geological, climatic and ecological processes in the Earth System during these times of global upheaval remain poorly understood. This study focuses on the Central Atlantic Magmatic Province and the associated extinction event in the latest Triassic, about 201 million years ago. Although climate and carbon cycle models successfully reproduce aspects of the end-Triassic environmental changes, many questions regarding the causal and temporal relations behind them remain unresolved. Here, we report an effort to model and quantify the dynamic response of the Earth System to short pulses of volcanogenic volatile emissions for an ensemble of emission scenarios. For the first time in the context of the end-Triassic events, this is done with a coupled climate model and under consideration of both carbon and sulfur emissions. Tested are pulses with similar to 1-6 kyr duration during which 2500 - 7500 GtC are emitted and 0 - 500 GtS form stratospheric sulfate aerosols. The simultaneous emission of carbon and sulfur during one pulse of volcanic activity causes climatic fluctuations on annual to millennial timescales: A sequence of transient global cooling and subsequent sustained warming, overprinted with high interannual variability. The simulated maximum global warming ranges from +1.8 to +4.4 degrees C, while the amplitude of cooling is considerably higher in the upper range of the tested sulfur emission scenarios. The magnitude of temperature change varies regionally, being lowest in the Tethys realm. Changes in steric sea level (similar to 1-3 m) and ocean overturning strength, a surface ocean pH decrease (similar to 0.2-0.4) and a drop of the carbonate saturation especially in the Tethys are also obtained from the simulations during each emission pulse. By evaluating the simulated temperature changes against thermal tolerance limits of stony corals in a simplified manner, we find that these are not clearly transgressed on a global scale in the simulated warming scenarios. However, the climatic variability potentially introduced by the volcanic forcing would have represented significant stress for marine organisms. This study represents a significant step towards integrating multiple volcanic forcing mechanisms and environmental response processes in space and time to yield a more complete picture of impacts of CAMP volcanism and LIPs in general. (C) 2020 Elsevier B.V. All rights reserved.