Pulsed biogenic methane emissions coupled with episodic warming during the Toarcian Oceanic Anoxic Event

Area of Science:

• Paleoclimatology
• Biogeochemistry
• Earth Science

Background:

• Understanding ancient climate dynamics is crucial for predicting future climate change.
• The Toarcian Oceanic Anoxic Event (T-OAE) offers insights into rapid warming and carbon cycle perturbations.

Purpose of the Study:

• To investigate the scale of biogenic methane release during the T-OAE.
• To assess methane's contribution to climate variability and mass extinction.

Main Methods:

• Developed a global biogeochemical model.
• Applied Bayesian inversion with Markov Chain Monte Carlo (MCMC) simulations.
• Utilized high-resolution carbon isotope excursion data from the Yorkshire section.

Main Results:

• A release of at least 4,700 Gt of biogenic methane (δ¹³C of -50 to -70‰) is required to explain observed carbon isotope shifts.
• This methane release likely increased atmospheric methane concentrations, causing >2 °C of additional global warming.
• Methane release was facilitated by increased methanogenesis and decreased methane oxidation in marine environments.

Conclusions:

• Biogenic methane release acted as a significant positive feedback during the T-OAE.
• The methane cycle exacerbated environmental changes, contributing to marine life's mass extinction.
• Reconstructing past methane fluxes improves predictions of future carbon cycle and climate dynamics.