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Rate of change of magnetic field over the Pacific region: tackling a century-old question

U of A physicist Mathieu Dumberry believes the electric conductivity of the Earth's mantle may play a role in weakening the magnetic field over the Pacific

A study by a University of Alberta physicist tackles a mystery of nearly a century: why changes to the magnetic field are weaker over the Pacific region.

Mathieu Dumberry, a physics professor, alongside co-author PhD student Colin More, explored why changes in the magnetic field differ over different regions of the Earth through a study published in the Journal Nature Geoscience. Through this study, the team was able to come up with a possible reason for the mystery of why changes in the magnetic field are weaker over the Pacific region.

Within the Earth’s inner core are fluid motions, much like ocean currents. The Earth’s magnetic field is generated and maintained by these fluids. As a result, we have a magnetic field that changes as a function to time. In their study, Dumberry and More observed these fluid motions using simplified, idealized models of the dynamics of the Earth’s core. 

Dumberry explained that getting proper data over the Pacific region hasn’t always been easy. Previously, researchers blamed improper data collection while onboard ships for the weaker change of magnetic field over the Pacific. However, once satellites were used, it became evident it was the magnetic field itself that was actually weaker over the Pacific. 

“A few decades ago, people thought that perhaps the quality of the data over the Pacific was not good enough,” Dumberry explained. “But once we started having data from satellites, the surprise was that the satellite data confirmed [the weaker change of the magnetic field over the Pacific] even more strongly.” 

The study credits the weak changes in the Pacific Ocean’s magnetic field to the electric conductivity of the Earth’s lowermost mantle. This conductivity is higher in the Pacific region than elsewhere, and may weaken the local fluid motions in the inner core that generate an electric current, leading to changes in the magnetic field.

Dumberry also posed other possible reasons for this data, explaining this information to be a simple snapshot in the complex and dynamic system of the Earth’s core. 

“Now the key here —and that’s the subtlety — is it’s not so much the magnetic field itself that is weaker, it’s really the time changes of the field, ” Dumberry explained. “Essentially really what we’re looking at is the rate of change. The escalation of that could be simply that the core is a dynamic system, and we just happen to be looking at a time snapshot of that complex dynamical system, and currently it’s a bit asymmetrical in such a way that it’s currently weaker in the Pacific.”

For Dumberry, there are large goals for his work, and he has sights of advancing this hypothesis in the future. This includes using more realistic and complex models and simulations to test the idea further. 

“The way we approached this problem is that we wanted to do a quick demonstration,” Dumberry said.” In order to do this, we used a highly idealized model of the dynamics of the Earth’s core. What we would like to do is a better job at it.” 

“In other words, [we want to] include this idea in a more complex and realistic model. These are all computer simulations of the dynamics of the Earth’s core, but using one of these more complex models to test this idea a little bit further is certainly one prospective for the future.”

Areeha Mahal

Areeha Mahal is The Gateway’s 2020-21 Deputy News Editor and a first-year Biological Sciences student. When she’s not learning the Krebs cycle for the millionth time, Areeha enjoys stargazing, baking pies, and stalking Chris Hadfield on Twitter.

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