Study reveals South Atlantic magnetic anomaly is a recurring feature

Study reveals South Atlantic magnetic anomaly is a recurring feature

In a new study, scientists from the University of Liverpool in England traced back the strange behavior of the magnetic field in the South Atlantic region and found that similar anomalies existed as far back as 8 to 11 million years ago.

The South Atlantic Anomaly is an area characterized by a major reduction in the strength of the Earth's magnetic field, compared with areas of the same geographic latitudes.

In this area, there is less protection from harmful radiation from space. The most significant indications of this are technical malfunctions aboard spacecraft and satellites.

Liverpool paleomagnetic researchers examined the record of the planet's magnetic field, which is preserved in igneous rocks from the Saint Helena Island, located in the middle of the South Atlantic Anomaly.

Geomagnetic records from the rocks covering 34 various volcanic explosions that occurred between eight to 11 million years ago showed that at these occurrences, the direction of the magnetic field for Saint Helena usually pointed far from the North Pole, just as it does now.

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A map of the Earth showing today's deviation from the expected magnetic field direction. Image credit: Dr. Yael Engbers, Universit of Liverpool

The South Atlantic Anomaly is a topic of debate among scientists. Aside from the fact that it causes damage to space technology, it also raises the concern about where it originates and whether it represents the beginning of the total weakening of the field, and a possible pole reversal.

"Our study provides the first long term analysis of the magnetic field in this region dating back millions of years," said lead author Yael Engbers, a Liverpool Ph.D. student.

"It reveals that the anomaly in the magnetic field in the South Atlantic is not a one-off, similar anomalies existed 8to 11 million years ago."

"This is the first time that the irregular behavior of the geomagnetic field in the South Atlantic region has been shown on such a long timescale. It suggests that the South Atlantic Anomaly is a recurring feature and probably not a sign of an impending reversal," he added.

"It also supports earlier studies that hint towards a link between the South Atlantic Anomaly and anomalous seismic features in the lowermost mantle and the outer core. This brings us closer to linking behavior of the geomagnetic field directly to features of the Earth's interior."

Reference

"Elevated paleomagnetic dispersion at Saint Helena suggests long-lived anomalous behavior in the South Atlantic" - Engbers, Y. A. et al. - Proceedings of the National Academy of Sciences of the United States of America - https://doi.org/10.1073/pnas.2001217117

Abstract

Earth’s magnetic field is presently characterized by a large and growing anomaly in the South Atlantic Ocean. The question of whether this region of Earth’s surface is preferentially subject to enhanced geomagnetic variability on geological timescales has major implications for core dynamics, core−mantle interaction, and the possibility of an imminent magnetic polarity reversal. Here we present paleomagnetic data from Saint Helena, a volcanic island ideally suited for testing the hypothesis that geomagnetic field behavior is anomalous in the South Atlantic on timescales of millions of years. Our results, supported by positive baked contact and reversal tests, produce a mean direction approximating that expected from a geocentric axial dipole for the interval 8 to 11 million years ago, but with very large associated directional dispersion. These findings indicate that, on geological timescales, geomagnetic secular variation is persistently enhanced in the vicinity of Saint Helena. This, in turn, supports the South Atlantic as a locus of unusual geomagnetic behavior arising from core−mantle interaction, while also appearing to reduce the likelihood that the present-day regional anomaly is a precursor to a global polarity reversal.

Featured image credit: Dr. Yael Engbers, University of Liverpool

Comments

André Hermans 8 days ago

On Earth in the European Miocene, between ~ 8 million and 11 million years ago within the tortonian marine stage, there were 6 polarity switches C4-C4r-C4A-C4Ar-C5-C5r https://www.sciencedirect.com/topics/earth-and-planetary-sciences/tortonian

André Hermans 8 days ago

366/5000 A magnetic REVERSAL always starts with a magnetic excursion. The current excursion started during the birth year of Svante Arrhenius with the Carrington event SOL-09-01. The influence of the sun on the geodynamo of the earth is modulated, among other things, by the third parameter (relative to the seabed) of the geographical positions of the magnetic poles.

Jamal Shrair 8 days ago

YOU ARE WRONG, IT IS A SIGN OF AN IMPENDING REVERSAL.............................I have been arguing for years that the energy builds up at the Earth's interior is the reason for the rapid pole shift and most of the climate changes and also, reason for the massive increase in the eruption of underwater volcanoes. https://www.nature.com/articles/d41586-019-00007-1 However, the leading author of the paper is wrong in saying that the South Atlantic Anomaly is not a sign of an impending reversal. IT IS A SIGN OF AN IMPENDING REVERSAL. Our star is the best example to understand the cause of the South Atlantic Anomaly. A similar phenomenon is taking place during the final stage in the reversal of the Sun's magnetic field. Keep in mind, however, that the time scale is different. The Sun takes a few weeks to complete the final stage, while the Earth might take several years.

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