The emergence of a mysterious area in the South Atlantic, where the strength of the geomagnetic field is rapidly decreasing, has led to speculation that the Earth is heading towards a reversal of magnetic polarity. However, a new study gathering evidence dating back 9,000 years suggests that the current changes are not unique and that a reversal may not be in the cards 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 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 switch places.
During the last 180 years, the strength of Earth’s magnetic field has decreased by about 10%. Simultaneously, an area with an exceptionally weak magnetic field grew in the South Atlantic off the coast of South America. This area, where satellites have failed multiple times 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 towards a polarity reversal. However, the new study suggests this may not be the case.
“We’ve mapped changes in Earth’s magnetic field over the last 9,000 years, and anomalies like the South Atlantic are likely to be recurring phenomena linked to corresponding variations in the strength of Earth’s magnetic field,” says Andreas Nilsson, a geologist at Lund. University.
The results are based on analyzes of burnt archaeological artifacts, volcanic samples and sediment drill cores, all of which carry 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. Objects act as time capsules and carry information about the magnetic field in the past. Using sensitive instruments, the researchers were able to measure these magnetizations and recreate the direction and strength of the magnetic field at specific locations and times.
“We have developed a new modeling technique that connects these indirect observations from different periods and locations into a global reconstruction of the magnetic field over the last 9,000 years,” says 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 about speculation about 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 Earth is not heading for a polarity reversal,” concludes Andreas Nilsson.
Study reveals strange magnetic behavior from 8 to 11 million years ago
Andreas Nilsson et al, Ancient Recurrent Geomagnetic Field Anomalies shed light on the 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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