Strong link between Earth's oxygen level and geomagnetic dipole revealed since the last 540 million years.

Earth is the only known rocky planet to support complex life forms that use oxygen and to have a strong intrinsic magnetic field in much of its history, prompting speculation that Earth's magnetic field and habitability are related on geological timescales. We search for possible observational evidence for such a relationship by examining evolutions of the virtual geomagnetic axial dipole moment and the atmospheric oxygen level over the past 540 million years. We find that both exhibit strong linearly increasing trends, coupled with a large surge in magnitude between 330 and 220 million years ago. Our time series analysis and statistical tests show that both are highly correlated, with the maximum correlation reached when there is no time lag between the two. Our findings suggest unexpected strong connections between the geophysical processes in Earth's deep interior, the surface redox budget, and biogeochemical cycling.