Last year, scientists announced that the Earth’s magnetic north pole was moving to Siberia at an unusually fast rate and could not explain why. It had moved so far, so fast, there had to be an unplanned update to the World Magnetic Model (WMM), the Earth’s magnetic field representation used in navigation systems around the world.
In a study published in the magazine Nature Geoscience, researchers have now suggested a cause for the unexpected movement: two massive spots of “negative magnetic flux” sitting below Canada and Siberia, on the edge of the Earth’s core.
It is believed that the Earth’s magnetic field is generated by the rotational motions of molten iron in the nucleus of the planet. The field has a north and south pole, the positions of which are constantly moving. The position of the magnetic north pole was first recorded in 1
But over the coming decades, his position has shifted. Eventually, scientists found that the magnetic north was moving at a speed of about six miles a year. But that changed in the 1990s and 2000s, when the movements of the pole began to accelerate, eventually reaching a speed of about 25 miles a year. What caused this increase was unknown.
The latest study, led by Philip Livermore of the School of Earth and Environment at the University of Leeds in the United Kingdom, looked at a potential cause for this unexpected and “remarkably linear” movement. The team looked at the high-resolution geomagnetic data collected over the last two decades and found two large magnetic patches under Canada and Siberia.
Although these patches are characteristic of the Earth’s magnetic field as a whole, they say that if examined in isolation, they could explain the recent wanderings of the North Pole. “The current, two-width, high-latitude geomagnetic field structure then defines two ends of a linear channel in an almost vertical field along which the north magnetic pole can easily move,” they wrote.
In an email to NewsweekLivermore said the patches are areas where the magnetic field exits the Earth’s core “like a bundle of spaghetti.” He said patches, or “foreheads,” are a by-product of the dynamo process. “The magnetic field plates are moving all the time – over a hundred years time range – but the Canadian forehead seems to be moving especially fast,” he said.
Researchers have found that the Canadian patch has lengthened and weakened – and that this is likely the result of changes in the pattern of flow in the Earth’s core, dating to about 1970. With the weaker Canadian patch, the pull of the Siberian patch has been greater influence that causes the magnetic north to be drawn to it. Team models indicate that the North Pole will continue on its way to Siberia, passing between 242 and 410 miles over the next decade.
Livermore said they were sure the weakened Canadian patch was behind the latest movements, but what caused the extension was less clear. “We assume that the nucleus stretches it, but other processes may play a role such as diffusion, such as a magnetic field emanating from the nucleus,” he said.
He also said that as the magnetic north pole moves faster, the WMM may need to be updated more regularly to take account of changes in its position. Typically, the model is updated every five years. “It is quite possible that annual updates will be needed in the coming years. It is difficult to say for sure,” he said.