The magnetic field that surrounds our planet is constantly shifting. But recently, near the Arctic, it’s been so active that researchers had to release a crucial update to a computer model that allows maps and other navigation software to correctly point North. The public release of this update to the World Magnetic Model (WMM) has been highly anticipated, but it was delayed until Monday due to the recent US government shutdown.
Unlike the geographic North Pole, which stays put at the top of the globe, the North Magnetic Pole moves, and it historically does this at a fairly steady rate. Lately, it’s moved at about 31 miles (50 kilometers) per year. Since compasses were invented hundreds of years ago, we’ve used the magnetic field to navigate with compasses pointing generally North. But as the North Magnetic Pole moves away from the geographic North Pole, figuring out where you are in the world can become a lot harder.
“The pole moved maybe about 1,000 kilometers [621 miles] between 1900 and 1990, and it’s also moved about 1,000 kilometers between the late 1990s and today, so it’s really sped up,” says William Brown, a global geomagnetic field modeler for the British Geological Survey, who worked on this update to the World Magnetic Model.
Cartographers figured out that they needed to take the distance between geographic and magnetic North into account a long time ago, which you might notice if you look carefully at paper maps. “If you go hiking and you use a very old map, the correction that you set your compass to will be written on the map somewhere, and that actually has an expiry date,” says Brown.
When the pole moves, print maps need to be reprinted, and digital maps used on smartphones and mapping software used by military and government agencies have to be updated. Occasionally, it changes enough that airport runways have to get new names so that pilots, who sometimes use magnetic fields to navigate, know where to land.
For both digital and analog updates, that’s where the WMM comes in. It’s jointly funded by military mapping agencies of both the United States and the United Kingdom. Usually, it’s updated every five years. It predicts how much the pole will move and how much other portions of the magnetic field will shift over that time span.
But over the past few years, something strange happened: the magnetic field near the North Pole began changing even more than usual.
“The error grew a little bit faster than usual, especially in the Arctic region very high up north near the North Magnetic Pole,” says Arnaud Chulliat, a research scientist at the University of Colorado Boulder and the National Oceanic and Atmospheric Administration (NOAA) who worked on the update. The first phenomenon was the moving North Pole, which is moving toward Siberia. That alone wouldn’t have been enough to throw off the model. But the catalysts, in this case, were relatively sudden changes in how fast molten iron was moving around in the Earth’s core.
“Sometimes it speeds up, and sometimes it slows down. The reason for the very rapid change at the poles is because that flow has sped up in certain areas,” Brown says. These shifts in speed are called geomagnetic pulses, and typically, they aren’t that noticeable.
“Normally, it’s a subtle event that has no practical impact,” Chulliat says. “But here, in the present situation, this geomagnetic pulse combined with the fast-moving North Magnetic Pole led to the error increasing faster than usual.”
The effects of the inaccurate model are too small to be noticed in people’s everyday lives — unless their everyday lives include using their smartphone compass in the immediate vicinity of the North Pole — but it got to the point where the model in the Arctic just wasn’t accurate enough for the researchers’ comfort.
“I don’t want to exaggerate the consequences of this. In lower latitudes, the current model is fine,” Chulliat says. “Only the area around the North Magnetic Pole is where the error will become substantial.”
In 2017, WMM scientists decided it would be best to do another small update early this year instead of just waiting until the current model expired at the end of 2019.
Monitoring how the magnetic field moves can give researchers like Brown insight into what’s happening at the Earth’s core about 1,800 miles below the Earth’s surface. But it also helps keep the model up to date. One reason that Chulliat, Brown, and their colleagues were able to update the model before the five-year mark is that the Earth’s magnetic field is more closely monitored today than it ever has been. Three European satellites called Swarm measure the magnetic field every 90 minutes, and 160 research observatories keep a constant watch.
Data from all of those observatories were incorporated into the update. A calculator based on the model was released in January by the British Geological Survey, but the American rollout of the same model was delayed until this week due to the government shutdown. (The World Magnetic Model is released online by NOAA, and the agency’s websites were inaccessible until the US government reopened.)
Now, the updated model is online and publicly accessible. It is expected to stay accurate through the end of 2019, at which point the regularly scheduled update — which will be valid from 2020–2025 — will be released. Though this particular out-of-cycle update is unprecedented, researchers say that really, there’s no cause for alarm.
“Don’t panic,” Brown says. “The magnetic field does change, and we’ve seen it change unexpectedly and quickly before. This is something that we know. It’s not something that we understand how it works, but we’re aware that it happens.”