Every few years, scientist Larry Newitt of the Geological Survey of Canada embarks on an unusual kind of hunt. Equipped with gloves, a parka, a sophisticated compass, and a plane ticket, he heads north to the Canadian Arctic. While the scattered islands and sea ice may appear desolate, Newitt knows that his quarry is out there—constantly shifting, elusive, and on the move.
His target? Earth’s north magnetic pole.
Currently located in northern Canada, the pole sits about 600 kilometers from the nearest settlement, Resolute Bay, a tiny town with a population of 300. The town’s popular T-shirt reads, “Resolute Bay isn’t the end of the world, but you can see it from here.” Newitt uses the town as a base for supplies, snacks, and shelter when the weather turns hostile—which, he notes, is quite often.
Right: The movement of Earth’s north magnetic pole across the Canadian Arctic, 1831–2001. Credit: Geological Survey of Canada. [more]
Scientists have known for centuries that the magnetic pole is not fixed. James Ross first located the pole in 1831 after an arduous Arctic expedition during which his ship became trapped in ice for four years. It wasn’t until the next century that anyone returned. In 1904, Roald Amundsen revisited the pole and discovered that it had already shifted—at least 50 kilometers from where Ross had found it.
The magnetic pole has continued its journey throughout the 20th century, moving north at an average rate of 10 km per year. Recently, however, its speed has increased, with Newitt reporting that it is now traveling “up to 40 km per year.” If this trend continues, the pole will exit North America and reach Siberia within a few decades.
Tracking the movement of the north magnetic pole is Newitt’s responsibility. “We usually check its location once every few years,” he says. “But with its current speed, we’ll need to make more frequent trips.”
Earth’s magnetic field is undergoing other changes as well. For example, compass needles in Africa are shifting by about 1 degree per decade, and the global magnetic field has weakened by about 10% since the 19th century. When researchers recently discussed this at a meeting of the American Geophysical Union, many media outlets ran with the story, often with headlines like, “Is Earth’s magnetic field collapsing?”
The answer is probably not. As significant as these changes may seem, University of California professor Gary Glatzmaier points out, “They’re mild compared to the dramatic shifts Earth’s magnetic field has experienced in the past.”
Sometimes, Earth’s magnetic field undergoes a complete reversal, where the north and south poles swap places. These reversals, recorded in the magnetism of ancient rocks, are unpredictable and occur at irregular intervals, averaging about 300,000 years. The last reversal took place 780,000 years ago—so, are we overdue for another one? The truth is, no one knows.
Left: Magnetic stripes along mid-ocean ridges record Earth’s magnetic field over millions of years. The study of past magnetism is known as paleomagnetism. Image credit: USGS.
Despite the ongoing 10% decline in the magnetic field, Glatzmaier assures that a reversal is not imminent. “The magnetic field is constantly fluctuating,” he explains. “We can track this through studies of the paleomagnetic record.” In fact, Earth’s current magnetic field is much stronger than usual. The dipole moment—a measure of the magnetic field’s intensity—is now 8 × 10²² amps × m², which is twice the million-year average of 4 × 10²² amps × m².
Glatzmaier says we need to travel to the center of the Earth, where the magnetic field is generated to understand these fluctuations.
At the Earth’s core lies a solid iron ball, nearly as hot as the surface of the sun. This solid inner core, which is about 70% the width of the moon, spins at a slightly faster rate than the Earth above it—about 0.2° of longitude per year. Surrounding the inner core is a deep ocean of liquid iron known as the outer core, which plays a key role in generating Earth’s magnetic field.
Earth’s magnetic field is generated by the outer core, a vast ocean of electrically conductive liquid iron in constant motion. Resting atop the hot inner core, the outer core churns and roils like water in a pan on a stove, driven by intense heat. This fluid also features “hurricanes”—whirlpools created by the Coriolis effect, which is powered by Earth’s rotation. These dynamic motions produce the planet’s magnetic field through a process known as the dynamo effect.
Using magnetohydrodynamics—the study of conducting fluids and magnetic fields—Glatzmaier and his colleague Paul Roberts have developed a supercomputer model of Earth’s interior. Their simulation heats the inner core, stirs the liquid outer core, and then calculates the resulting magnetic field. Running the model for hundreds of thousands of simulated years, they observe how the magnetic field changes.
What they see mirrors Earth’s actual behavior: the magnetic field fluctuates, the poles drift, and occasionally, they flip. Change, they’ve learned, is a normal part of this process. And it makes sense, given that the outer core, the source of the field, is itself in a state of constant turbulence. “It’s chaotic down there,” Glatzmaier says. The changes we observe on Earth’s surface reflect this inner chaos.
Through their simulations, they’ve also learned what happens during a magnetic reversal. Contrary to popular belief, the magnetic field doesn’t disappear during a flip—it simply becomes more complicated. “It gets more tangled,” Glatzmaier explains. During a reversal, the magnetic lines of force near the surface of the Earth twist and become confused, and magnetic poles can appear in unexpected locations. For example, a south magnetic pole might emerge over Africa, or a north pole might pop up over Tahiti. It may seem strange, but it’s still a magnetic field, and it continues to protect the planet from space radiation and solar storms.
Above: Supercomputer simulations of Earth’s magnetic field. On the left, you see a typical dipolar magnetic field, representing the stable periods between polarity reversals. On the right, the field is much more complex, illustrating the chaotic conditions during a magnetic reversal.
As a bonus, Tahiti could become a prime spot to view the Northern Lights. If that were the case, Larry Newitt’s job would take a different turn. Instead of braving the cold in Resolute Bay, he might enjoy the warm South Pacific, island-hopping in search of magnetic poles while auroras shimmered above.
Perhaps, sometimes, a little change can be a good thing.