EONS: A new biogeochemical model of Earth's longterm evolution




Horne, Julia

Journal Title

Journal ISSN

Volume Title



I present Earth’s Oxygenation and Natural Systematics (EONS): a new, fully coupled biogeochemical model of the atmosphere, ocean, and their interactions with the geosphere, which can reproduce major features of Earth’s evolution fol- lowing the origin of life to the present day. The model includes an interactive biosphere, cycles of carbon, nitrogen, phosphorus, and oxygen, and climate. A nominal model run initialized in the Eoarchean resolves emergent surface oxy- genation, nutrient limitations, and climate feedbacks. The modelled atmosphere oxygenates in stepwise fashion over the course of the Proterozoic; a nearly billion year lag after the evolution of photosynthesis at 3.5 Ga is followed by a great oxi- dation event (GOE) at 2.4 Ga, which appears to be caused by the gradual buildup of organic matter on the continents imposing nutrient limitation on the biosphere by removing key nutrients from the ocean system. The simple climate system shows significant temperature shifts punctuate the oxygenation process, implying that major biological transitions possibly destabilized Earth’s climate. I expand upon this finding by adapting the climate system to include non-linearities such as ice-albedo and supergreenhouse feedbacks in order to investigate potential causes of Paleoproterozoic Snowball Earth events. My preliminary findings suggest that Paleoproterozoic glaciations may have preceded the GOE, and are more likely a result of perturbations to atmospheric CO2 than from declining CH4. This work demonstrates that forward modelling the entirety of Earth’s history with relatively few imposed boundary forcings is feasible, that the Earth system is not at steady state, and that our understanding of coupled C-N-P-O cycling as it functions today can explain much of the Earth’s evolution.



biogeochemistry, Earth evolution, Earth systems, carbon cycle, nitrogen cycle, phosphorus cycle, oxygen, modelling