Collaborative Research: The early Holocene as an analog for the historical geomagnetic field: Investigating dipole moment and field morphology using Arctic paleomagnetic data

Our magnetic field influences Earth’s habitability, human technology and communications, upper atmospheric dynamics, and more. Recent changes to the field open questions as to how the field will to change in the future, and the impact this will have on the Earth system. Notably, during the historical period when humans have made direct measurements of the field, the geomagnetic field strength has decreased and the rate of North Magnetic Pole movement has accelerated. This project will study geologic archives of geomagnetic change from 10,000 to 7,000 years ago, an era that may have been similar to modern geomagnetic field changes. Specifically, the project strengthens international collaborations to synthesize new and existing reconstructions of direction and intensity changes from Arctic Ocean and lake sediment cores that create a broad longitudinal transect including Northern Alaska, Arctic Canada, Northern Greenland, and Northern Europe. This project will target 22 core samples that meet strict quality requirements and are available to the US research community in NSF supported repositories but have not previously been investigated for geomagnetic reconstructions. Two graduate students will learn methods that will have broad applications to their future careers in geophysical, data analysis, and earth science fields. This project will establish an early to mid-Holocene paleomagnetic transect across the Arctic to test a fundamental, yet somewhat counter intuitive, hypothesis about the nature of the geomagnetic field. The hypothesis, “the decrease in geomagnetic dipole moment observed in the last two centuries represents a transition to a more stable, more geocentric axial dipole like field that could persist for millennia”, is informed by 1) Holocene dipole moment reconstructions, 2) longer-term (100 thousand year) dipole moment reconstructions, 3) reconstructions of global field morphology that demonstrate that high intensities of the late Holocene are associated with a more dynamic field than the more average intensities of the early Holocene, and 4) disagreement between modeling efforts for the early Holocene that stems from limited data coverage. While previous work often discusses two states of the geomagnetic field—one that is strong and stable and one that is week and unstable—this hypothesis suggests that the field may be better described by three states with the greatest stability at intermediate dipole moments. The research team identifies archives for which strong independent radiocarbon chronologies already exist (or can be developed), extend to the early Holocene, and have very high accumulation rates (minimally >50 cm/kyr; ideally >100 cm/kyr). Reproducibility is at the heart of this work and is a critical test of reliability. Expected products will include new full-Holocene, full-vector paleomagnetic reconstructions from three Arctic regions (the Beaufort Sea, Northern Greenland, and the Northern North Atlantic) that will be among the highest quality and highest resolution reconstructions available. When combined with previously published data, this paleomagnetic transect will enable exploration of geomagnetic variations at the right time interval needed to assess this hypothesis. This project will support the education of two graduate students, support an international collaboration, and lead to the development of outreach materials on the Earth’s magnetic field. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.