Scientists have known since the early nineteenth century that the Earth’s magnetic north pole wanders slowly over time, a phenomenon that cartographers have kept track of to ensure the accuracy of navigational charts and any other fields that might be affected by this magnetic meandering. Over the centuries, this drift has been slow, but in recent years the movement of magnetic north has accelerated for reasons that aren’t completely understood, and this rapid movement has prompted researchers to update the map of the planet’s magnetic field a year ahead of schedule.
Mapped out by the U.S. National Geophysical Data Center (NGDC) and the British Geological Survey (BGS), the World Magnetic Model is a large-scale map of the Earth’s magnetic field that informs virtually all of the world’s navigation systems, from ocean-bound nautical navigation guiding ships at sea to Google Maps on smartphones helping their users find their way down the street. But a number of rapid changes that have occurred to the Earth’s magnetic field have caused the most recent World Magnetic Model to become inaccurate, prompting its custodians to update it earlier than planned.
Two major changes within the Earth’s magnetic field have prompted the urgent update: in 2016, part of the magnetic field deep under northern South America and the eastern Pacific Ocean temporarily accelerated; the other was that the acceleration of the drift of the north magnetic pole that began in the mid-1990s has caused the pole to be further along in its Siberia-bound journey than anticipated.
The last update to the WMM was made in 2015, with the next update originally scheduled to be made in 2020, but these recent magnetic events, along with other minor rapid changes, have caused the model to become inaccurate enough that the National Oceanic and Atmospheric Administration (NOAA) decided to release the next update on January 15 2019 instead, although the release has been postponed to January 30, due to the ongoing US government shutdown.
Up until about 25 years ago, the north magnetic pole’s drift moved at about 15 kilometers (9.3 miles) per year, but since then it has accelerated to nearly four times that rate, at 55 kilometers (34 miles) per year. Traditionally situated in the Canadian Arctic Archipelago, the pole recently passed the International Date Line into the Eastern Hemisphere, and is currently heading straight for Siberia.
Researchers are working to understand why the morphing of the planet’s magnetic field has been accelerating in recent years. The field itself is thought to be generated by differences in the flow of the planet’s outer core, being composed of mostly liquid iron and nickel. Heat from the solid inner core drives currents that have been observed in the outer core, and the coriolis effect organizes these currents into regional zones that act as large electrical generators, and in turn, that electrical current generates a series of magnetic fields. Combined together, these individual fields form the larger effect known as the Earth’s magnetic field.
But some of the currents generating the individual fields may be affected by hydromagnetic waves that originate deep within the planetary core, accelerating movements like the 2016 geomagnetic pulse, and the high-speed current of liquid iron flowing beneath Canada.
"The location of the north magnetic pole appears to be governed by two large-scale patches of magnetic field, one beneath Canada and one beneath Siberia," according to Phil Livermore, a geomagnetist at the University of Leeds, UK. "The Siberian patch is winning the competition."