The north magnetic pole is restless.
Distinct from the geographic North Pole, where all the lines of longitude meet at the top of the world, the magnetic pole is the point that a compass recognizes as north. At the moment, it’s 4 degrees south of the geographic North Pole, which lies in the Arctic Ocean at 90 degrees north. But that wasn’t always the case.
In the mid-19th century, the north magnetic pole floated much farther south, roaming around Canada. For the past 150 years, however, the pole has been sprinting away from Canada and toward Siberia.
That change of address cannot be ignored, given that magnetic compasses still underpin modern navigation, from the systems used by civilian and military airplanes to those that orient your iPhone.
In 1965, scientists began a data-based representation of Earth’s magnetic field in order to better keep track of the pole’s ever-changing home. The World Magnetic Model is updated every five years — most recently in 2015 — because the magnetic field is constantly shifting.
In early 2018, it became clear that 2015’s edition was in trouble, because the pole’s Siberian stroll had picked up speed, rendering the model — and therefore a number of navigational systems — incorrect.
So for the first time, scientists have updated the model ahead of schedule, which they released Monday afternoon. Since this work was completed in the wake of the partial government shutdown (which delayed its full release), researchers are still trying to get a handle on the mysteries within Earth’s core that must be driving the magnetic pole’s surprising behavior.
A continuous makeover
The north magnetic pole’s dizzying dance was discovered nearly 400 years ago, when Henry Gellibrand, an English mathematician, realized that it had jumped hundreds of miles closer to the geographic pole over the course of 50 years.
“That was a big, monumental recognition that the field was not static, but dynamic,” said Andrew Jackson, a geophysicist at ETH Zurich.
It didn’t take long, however, before magnetic north flipped direction and started to move away from the geographic pole — demonstrating that the field is not just dynamic, it’s unpredictable.
Scientists attribute this wanderlust to the liquid iron sloshing within our planet’s outer core. That iron rises, cools and then sinks. And that motion below carries Earth’s magnetic field with it, producing changes above.
Alongside GPS, navigational systems used by satellites, aircraft, ships and other vehicles rely on magnetic compasses to ensure they’re moving in the correct direction. Perhaps the most visible sign of this can be found at the end of every airport runway, where large white numbers reflect the runway’s magnetic heading.
But as the magnetic field shifts, those headings change and runways get a makeover. And it all depends on the World Magnetic Model, which is not easy to build. Unlike the kilogram or the second, the magnetic field cannot be defined once and then used for decades.
The pole’s pilgrimage
After scientists released the World Magnetic Model in 2015, they periodically checked it against field measurements to ensure that it was accurately predicting variations in Earth’s magnetic field. When they ran that check in early 2018, they discovered the model and reality were out of alignment.
“We noticed that the error in the Arctic was increasing faster than what we would expect,” said Arnaud Chulliat, a geophysicist with NOAA.
Although the north magnetic pole has long been scurrying away from Canada and toward Siberia, the rate of its movement drastically changes. Throughout most of the 20th century, it drifted at roughly 6 miles per year. In the 1980s, it picked up speed, and by the year 2000 it was traveling at 35 miles per year on the way out of Canada.
Then, in 2015, the pole slowed to 30 miles per year. So when the team issued the most recent magnetic map, scientists predicted the speed would continue dropping.
Just after the model was released, the north magnetic pole picked up momentum again, and now it is fluctuating at around 35 miles per year. In late 2017, the pole crossed the international date line into the Eastern Hemisphere.
“It’s not the fact that the pole is moving that is a problem, it’s the fact that it’s accelerating at this rate,” said William Brown, a geophysicist at the British Geological Survey. “The more acceleration or deceleration there is, the harder to predict where the thing is going to be.”
For people like Peter Olson, a geophysicist at Johns Hopkins University, the concern is relative. Whatever the risks to power grids and communications, humanity would have ample time to prepare. “Of all the problems we have, this is not a top 10 problem,” Olson said.