The emergence of a mysterious area in the South Atlantic where the intensity of the geomagnetic field is rapidly decreasing, has led to speculation that the Earth is heading towards a magnetic polarity reversal. However, a new study that collates evidence dating back 9,000 years suggests the current changes are not unique and a reversal may not be predicted after all. The study is published in PNAS.
Earth’s magnetic field acts as an invisible shield against the life-threatening environment in space and the solar winds that would otherwise sweep through the atmosphere. However, the magnetic field is not stable and at irregular intervals, on average every 200,000 years, polarity reversals occur. This means that the north and south magnetic poles swap places.
Over the past 180 years, the strength of the Earth’s magnetic field has decreased by about 10%. Simultaneously, an area with an unusually weak magnetic field developed in the South Atlantic off the coast of South America. This area, where satellites have repeatedly malfunctioned due to exposure to highly charged particles from the sun, is called the South Atlantic Anomaly. These developments have led to speculation that we may be heading for a polarity reversal. However, the new study suggests that may not be the case.
“We have mapped the changes in the Earth’s magnetic field over the past 9,000 years, and anomalies like the one in the South Atlantic are likely recurring phenomena linked to corresponding variations in the strength of the Earth’s magnetic field,” explains Andreas Nilsson, geologist in Lund. University.
The results are based on analyzes of burnt archaeological artifacts, volcanic samples and sediment drill cores, all of which contain information about the Earth’s magnetic field. These include clay pots that have been heated to over 580 degrees Celsius, volcanic lava that has solidified, and sediments that have been deposited in lakes or the sea. The objects act as time capsules and contain information about the magnetic field in the past. Using sensitive instruments, the researchers were able to measure these magnetizations and recreate the direction and intensity of the magnetic field at specific locations and times.
“We have developed a new modeling technique that links these indirect observations from different time periods and locations into an overall reconstruction of the magnetic field over the past 9,000 years,” explains Andreas Nilsson.
By studying how the magnetic field has changed, researchers can learn more about the underlying processes in the Earth’s core that generate the field. The new model can also be used to date archaeological and geological records, by comparing measured and modeled variations in the magnetic field. And reassuringly, that led them to a conclusion regarding speculation of an impending polarity reversal:
“Based on the similarities with the recreated anomalies, we predict that the South Atlantic Anomaly will likely disappear within the next 300 years, and that the Earth is not heading towards a polarity reversal,” concludes Andreas Nilsson.
Study reveals strange magnetic behavior 8 to 11 million years ago
Andreas Nilsson et al, Recurring Ancient Geomagnetic Field Anomalies Shed Light on Future Evolution of the South Atlantic Anomaly, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2200749119
Provided by Lund University
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