Dynamics of the Great Oxidation Event from a 3D photochemical-climate model

TL;DR

This study uses a 3D photochemical-climate model to explore the Earth's atmospheric transition during the Great Oxidation Event, revealing temperature effects, glaciation impacts, and methane fluctuations that influenced oxygen levels.

Contribution

It introduces a 3D modeling approach to study the GOE, highlighting the role of climate-chemistry coupling and atmospheric dynamics in this major transition.

Findings

Temperature-dependent photochemical losses influenced oxygenation.

Huronian glaciations caused fluctuations in oxygen levels.

Methane overshoot likely affected climate and glaciation dynamics.

Abstract

From the Archean toward the Proterozoic, the Earth's atmosphere underwent a major shift from anoxic to oxic conditions, around 2.4 to 2.1 Gyr, known as the Great Oxidation Event (GOE). This rapid transition may be related to an atmospheric instability caused by the formation of the ozone layer. Previous works were all based on 1D photochemical models. Here, we revisit the GOE with a 3D photochemical-climate model to investigate the possible impact of the atmospheric circulation and the coupling between the climate and the dynamics of the oxidation. We show that the diurnal, seasonal and transport variations do not bring significant changes compared to 1D models. Nevertheless, we highlight a temperature dependence for atmospheric photochemical losses. A cooling during the late Archean could then have favored the triggering of the oxygenation. In addition, we show that the Huronian glaciations, which took place during the GOE, could have introduced a fluctuation in the evolution of the oxygen level. Finally, we show that the oxygen overshoot which is expected to have occurred just after the GOE, was likely accompanied by a methane overshoot. Such high methane concentrations could have had climatic consequences and could have played a role in the dynamics of the Huronian glaciations.