A peer-reviewed study published in the Journal of Studies of Earth’s Deep Interior has mapped a dramatic reversal in the flow of liquid iron at the surface of Earth’s outer core beneath the Pacific Ocean, using 28 years of magnetic field data from ESA satellites and ground observatories spanning 1997 to 2025. The analysis, led by Frederik Dahl Madsen and colleagues at the University of Edinburgh, found that flow in the equatorial Pacific region — which had been drifting weakly westward for at least 9,000 years — abruptly changed direction around 2010, reversing to push strongly eastward at speeds of up to 20 kilometres per year. By applying principal component analysis to secular variation (SV) observations, the team was able to distinguish this Pacific anomaly from the broader planetary gyre of westward flow that dominates the outer core’s behavior at other latitudes. The new eastward current has been weakening since around 2020.
The timing is significant: the 2010 reversal coincides with independently confirmed changes in Earth’s solid inner core, which separate geodetic and seismological studies found was slowing its rotation around the same period. The Edinburgh team hypothesizes that disturbances originating deeper in the planet may have cascaded outward to alter liquid iron flow beneath the Pacific. The study challenges the assumption that outer core dynamics are comparatively stable, and offers new constraints on the turbulent processes that generate Earth’s geomagnetic field — whose secular variation is foundational to satellite navigation, compass calibration, and long-term climate modeling. The researchers note this is the first high-resolution mapping of exactly when the reversal occurred and how strong it became.