Were Neoarchean atmospheric methane hazes and early Paleoproterozoic glaciations driven by the rise of oxygen in surface environments?

Abstract

Geochemical evidence suggests methane was the predominant greenhouse gas in the Archean and early Proterozoic eons. Consequently, fluctuations in methane concentration in Earths atmosphere (i.e., methane hazes) would have contributed to climate change and influenced the flux of UV radiation reaching surface environments. If correct, understanding what factors (e.g., O2 and/or resource concentration) drove the biological methane cycle might shed light on the repetition of biological, atmospheric and climatic events preserved in the sedimentary rock record from ~2.8 to 2.0 BYA. To explore these interdependencies, we developed a novel dynamical model of microbial ecological interactions to investigate the conditions under which methane is preferentially released to the atmosphere. We found that the interplay between resource and O2 availability results in complex cyclic methane dynamics unrelated to the functional groups or efficiencies of microbial communities, to initial conditions, or to other model constraints. Based on these results, we propose that the cyclicity of methane haze events and glacial episodes in the Neoarchean and early Paleoproterozoic may have been linked to the progressive increase in oceanic and atmospheric O2 through the interval.