Magnet “hole” does not announce pole shift

The “hole” in the earth’s magnetic field over the South Atlantic is probably not a sign of an impending magnetic field reversal. A working group led by Andreas Nilsson from Lund University came to this conclusion based on a new model of the magnetic field over the period of the last 9000 years. As the team reports in »PNAS«, zones with an unusually weak magnetic field, such as the South Atlantic anomaly, occur from time to time, most recently around 2,600 years ago.

The model is based on measurements of archaeological finds, deep-sea sediments and volcanic deposits, which provide information about the direction and strength of the magnetic field at specific locations and times. The results show that strong regional anomalies are associated with regular fluctuations in the magnetic field dipole moment. Accordingly, the earth’s magnetic field should soon become stronger and more symmetrical and the South Atlantic “hole” will disappear again in the next few hundred years.

Behind the analysis is the question of how unusual the behavior of the magnetic field actually is at the moment – and whether it heralds a dramatic change. In the last 200 or so years, the earth’s magnetic field has weakened significantly, and since the late 1990s the North Pole has been moving at around 50 kilometers per year – more than three times as fast as before. This and the pronounced zone of very weak magnetic field over the South Atlantic have been interpreted by some experts as an indication that the earth’s magnetic field could soon be changing polarity.

Such pole shifts were common in the history of the earth. Such a “pole shift” would presumably have serious consequences for mankind. The magnetic field would probably almost disappear for centuries, possibly with significant effects on the earth’s climate. That would also be a problem for technology, for example satellites would be fully exposed to the solar wind.

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