Earth's Magnetic Field Can Shift 10 Times Faster Than Thought, Simulations Show
Changes in the Earth's magnetic field could take place 10 times faster than scientists previously thought, according to a new study published in the journal Nature Communications.
Earth's magnetic field could change 10 times faster
The new study, which came from scientists at the University of Leeds and the University of California in San Diego unveils new insight into the swirling flow of iron 2,800 kilometers beneath the earth's surface — in addition to how it's affected the movement of the planet's magnetic field in the last hundred thousand years.
The planet's magnetic field is generated and kept in action via convective flows of molten metal that form the Earth's outer core. Moving liquid iron creates electric currents that power the global field which not only helps navigational systems — but also shields life from extraterrestrial radiation while holding the atmosphere in place.
However, this is not a permanent affair.
Magnetic fields: everything moves, nothing abides
The Earth's magnetic field is perpetually changing. Satellites in orbit have given us a new ability to track its shifts but the field existed long before we knew how to record the action. To capture the field's evolution and study its behavior back through geological time, scientists look at magnetic fields' effect on sediments, lava flows, and human-made artifacts.
It's not easy to track the signal from the Earth's core with accuracy, so the rates of field change estimated via sediment analysis are still hotly debated.
Using simulations to study ancient magnetic fields
Associate Professor Chris Davies of Leeds, along with Professor Catherine Constable from the Scripps Institution of Oceanography, UC San Diego, took a new approach. Pooling their work, they combined computer simulations of the Earth's field generation process, and published a reconstruction of time variations in Earth's magnetic field spanning the past 100,000 years, according to phys.org.
In their new study, the scientists found that directional shifts in Earth's magnetic field happened at rates reaching up to 10 times that of the fastest reported variation of up to one degree per year.
These rapid changes are linked to a local weakening of the magnetic field. Changes in the Earth's magnetic field happen when it has reversed polarity or during geomagnetic excursions. This is when the dipole axis — which corresponds to emerging field lines flowing from one magnetic pole converge at the other — moves far away from the locations typically regarded as the North and South geographic poles.
Sharpest change in known geological history
The most explicit example from their study showed a sharp change in the geomagnetic field direction of roughly 2.5 degrees per year, 39,000 years ago. This was a shift linked to locally weak field strength, in a confined spatial region close to the west coast of Central America, following a global Laschamp excursion — which is a short reversal of the Earth's magnetic field.
This happened roughly 41,000 years ago. And the team's thorough analysis suggests the fastest directional changes are linked to the movement of reversed flux patches across the surface of the liquid core. These are prevalent at lower latitudes, which means future changes of such rapid rates will likely focus on equatorial zones.
"We have very incomplete knowledge of our magnetic field prior to 400 years ago," said Professor Davies of the School of Earth and Environment. "Since these rapid changes represent some of the more extreme behavior of the liquid core they could give important information about the behavior of Earth's deep interior."
More study needed of non-stable magnetic fields on Earth
Constable added to the sentiment, saying: "Understanding whether computer simulations of the magnetic field accurately reflect the physical behavior of the geomagnetic field as inferred from geological records can be very challenging."
"But in this case we have been able to show excellent agreement in both the rates of change and general location of the most extreme events across a range of computer simulations. Further study of the evolving dynamics in these simulations offers a useful strategy for documenting how such rapid changes occur and whether they are also found during times of stable magnetic polarity like what we are experiencing today."
It's not controversial to say that compasses don't point to true north. And, however unrealistic it may be to expect our compasses to spin wildly, like in a sci-fi or fantasy flick — the idea of rapid change in the Earth's magnetic field has more grounding in science, now more so than ever.