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Representation of Earth's magnetic field. The magnetic north pole has been moving towards Siberia at a faster pace than normal.

Last year, scientists announced Earth's magnetic north pole was moving toward Siberia at an unusually fast rate and they could not explain why. It had moved so far, so quickly, there had to be an unscheduled update to the World Magnetic Model (WMM), the representation of Earth's magnetic field used in navigation systems across the globe.

In a study published in the journal Nature Geoscience, researchers have now proposed a cause for the unexpected movement: two massive blobs of "negative magnetic flux" sitting beneath Canada and Siberia, on the edge of Earth's core.

Earth's magnetic field is thought to be generated by the swirling movements of molten iron in the planet's core. The field has a north pole and south pole, the positions of which are constantly moving. The position of the magnetic north pole was first recorded in 1831.

But over the coming decades, its position moved. Scientists eventually found the magnetic north was moving at a rate of around six miles per year. But this changed in the 1990s and 2000s, when the pole's movements starting speeding up, eventually reaching a rate of around 25 miles per year. What had caused this increase was unknown.
In the latest study, led by Philip Livermore from the School of Earth and Environment at the United Kingdom's University of Leeds, looked into a potential cause of this unexpected and "remarkably linear" movement. The team looked at high-resolution geomagnetic data collected over the last two decades and found two large magnetic patches beneath Canada and Siberia.

While these patches are typical of Earth's magnetic field as a whole, they say, if they are examined in isolation they could explain the north pole's recent wanderings. "The present two-patch structure of the high-latitude geomagnetic field then defines two ends of a linear conduit of near-vertical field, along which the north magnetic pole can readily travel," they wrote.

In an email to Newsweek, Livermore said the patches are areas where the magnetic field comes out of Earth's core "like a bundle of spaghetti." He said the patches, or "lobes," are a byproduct of the dynamo process. "Patches of magnetic field move around all the time—over hundred year timescales—but the Canadian lobe seems to be moving particularly fast," he said.
The researchers found that the Canadian patch has elongated and weakened—and that this was likely the result of changes to the pattern of flow in Earth's core starting from around 1970. With the Canadian patch weaker, the pull of the Siberian patch has had more influence, resulting in the magnetic north being pulled toward it. The team's models indicate the north pole will continue along its path toward Siberia, traveling between 242 and 410 miles over the next decade.

Livermore said they are sure the weakened Canadian patch is behind the recent movements, but what caused the elongation is less clear. "We assume that it is the core-flow stretching it, but it is possible that other processes play a role too such as diffusion e.g. magnetic field leaking out of the core," he said.

He also said that with the increased speed the magnetic north pole is moving, the WMM may be needed to be updated more regularly to account for the changes to its position. Normally, the model is updated once every five years. "It's quite possible that yearly updates will be necessary in the coming years, it's hard to say for sure," he said.

credit: ESA


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