The Oxygen Valve on Hydrogen Escape Since the Great Oxidation Event
Gregory J. Cooke, Dan R. Marsh, Catherine Walsh, Felix Sainsbury-Martinez, and Marrick Braam

TL;DR
This study uses a 3D Earth System Model to investigate how oxygen levels since the Great Oxidation Event have influenced hydrogen escape rates, finding that oxygen acts as a control valve affecting water vapor and hydrogen loss.
Contribution
It provides the first detailed 3D climate modeling analysis of how varying oxygen levels post-GOE impacted hydrogen escape rates on Earth.
Findings
Oxygen indirectly controls hydrogen escape by affecting ozone and tropopause temperatures.
Maximum differences in hydrogen mixing ratio and escape rates are factors of 3.2 and 4.7.
Hydrogen escape rates post-GOE are negligible compared to pre-GOE estimates.
Abstract
The Great Oxidation Event (GOE) was a Myr transition circa 2.4 billion years ago that converted the Earth's anoxic atmosphere to one where molecular oxygen (O) was abundant (volume mixing ratio ). This significant rise in O is thought to have substantially throttled hydrogen (H) escape and the associated water (HO) loss. Atmospheric estimations from the GOE onward place O concentrations ranging between 0.1% to 150% PAL, where PAL is the present atmospheric level of 21% by volume. In this study we use WACCM6, a three-dimensional Earth System Model to simulate Earth's atmosphere and predict the diffusion-limited escape rate of hydrogen due to varying O post-GOE. We find that O indirectly acts as a control valve on the amount of hydrogen atoms reaching the homopause in the simulations: less O leads to decreased O densities that reduce local…
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Taxonomy
TopicsPaleontology and Stratigraphy of Fossils · Methane Hydrates and Related Phenomena · Photosynthetic Processes and Mechanisms
