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Simulating 2 Ga of geodynamo history
Author(s) -
Driscoll Peter E.
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl068858
Subject(s) - dynamo theory , dynamo , paleomagnetism , geology , geomagnetic reversal , inner core , apparent polar wander , dipole , geophysics , outer core , physics , magnetic field , quantum mechanics
The paleomagnetic record indicates the geodynamo has been active over much of Earth history with surprisingly little trend in paleointensity. Variability, however, is expected from models that predict a sharp increase in intensity following inner core nucleation (ICN) and implied by Neoproterozoic anomalies that hint at a highly variable field over several hundred million years. Here we demonstrate with a suite of numerical dynamos driven by a new thermal evolution model that the geodynamo could have transitioned from a multipolar to dipolar regime around 1.7 Ga, then to a weak‐field dynamo around 1.0 Ga, and finally to a strong‐field dipole following ICN around 650 Ma that is maintained to the present day. The occurrence of a weak‐field geodynamo in the Neoproterozoic may be consistent with the observed anomalous apparent polar wander paths and reversal behavior. Recovery to a dipolar geodynamo in the Phanerozoic could be a signature of inner core nucleation. Index terms: 1507, 1560, and 1521.