EarthN: A new Earth System Nitrogen Model

TL;DR

EarthN is a novel nitrogen cycle model that links biological, geological, and atmospheric processes, revealing significant historical variations in Earth's nitrogen distribution driven by mantle cooling and nutrient interactions.

Contribution

The paper introduces EarthN, a comprehensive nitrogen cycle model that incorporates mantle cooling, biological feedbacks, and geologic fluxes, providing new insights into Earth's nitrogen history.

Findings

Atmospheric nitrogen has varied 2-4 times over Earth's history.

Nitrogen sequestration into the mantle and crust has been significant.

Mantle cooling, weathering, and nitrogen budgets control nitrogen distribution.

Abstract

The amount of nitrogen in the atmosphere, oceans, crust, and mantle have important ramifications for Earth's biologic and geologic history. Despite this importance, the history and cycling of nitrogen in the Earth system is poorly constrained over time. For example, various models and proxies contrastingly support atmospheric mass stasis, net outgassing, or net ingassing over time. In addition, the amount available to and processing of nitrogen by organisms is intricately linked with and provides feedbacks on oxygen and nutrient cycles. To investigate the Earth system nitrogen cycle over geologic history, we have constructed a new nitrogen cycle model: EarthN. This model is driven by mantle cooling, links biologic nitrogen cycling to phosphate and oxygen, and incorporates geologic and biologic fluxes. Model output is consistent with large (2-4x) changes in atmospheric mass over time, typically indicating atmospheric drawdown and nitrogen sequestration into the mantle and continental crust. Critical controls on nitrogen distribution include mantle cooling history, weathering, and the total Bulk Silicate Earth+atmosphere nitrogen budget. Linking the nitrogen cycle to phosphorous and oxygen levels, instead of carbon as has been previously done, provides new and more dynamic insight into the history of nitrogen on the planet.