MCADAM: A continuous paleomagnetic dipole moment model for the past 3.5 billion years using the PINT v8.0.0 database

Earth’s magnetic field is a long-lived phenomenon generated by dynamo processes occurring in the liquid core. Understanding how the strength of the field changes in time and space is critical to gaining insight into processes in Earth’s core and deep interior. The publication of field strength estimates represents a significant output of the paleomagnetic community, with efforts spanning several decades and dozens of research groups. Recently, the site-mean absolute paleointensity database PINT (www.pintdb.org; Bono et al., GJI, 2022) received a major update to include data published up through 2019 and fully integrates the Quality of Paleointensity (Q_PI) assessments for 94% of the database. Interpreting the paleointensity record as a continuous record of Earth’s field is challenging because of the non-uniformly spaced, often sparse, data records and the combination of natural variation of field strength due to secular variation and measurement uncertainty. Here, we have used the PINT database to construct a continuous paleomagnetic axial dipole moment model spanning 0.05 to 3500 Ma, MCADAM v1.0 (Monte Carlo Axial Dipole Average Model). The dipole moment model applies three resampling approaches: a non-parametric resampling (akin to a bootstrap) of site-mean records, a Monte Carlo simulation of site-mean estimates using age and paleointensity means and uncertainties, and LOWESS smoothing with an adaptative kernel width. These methods are combined to provide posterior predictions of axial dipole field strength and allow for estimation of the median field with confidence bounds. This approach can reproduce the recent (0-2 Ma) field that matches PADM2M (Ziegler et al., GJI, 2011) as well as salient field intervals (e.g., high fields associated with superchrons) during the Phanerozoic. The model also reveals changes in field strength during the Precambrian which may be used to help constrain dynamo simulations and thermal evolution models of Earth’s core.