What happens when the magnetic poles are reversed

Magnetic field shift : The North Pole no longer wanders - it runs

For January 30th, geophysicists from the USA and Great Britain decided to take an unusual step that is significant for the whole world: They are updating the "World Magnetic Model" ahead of time. If they didn't, pilots, ship captains and even users of Google Maps would soon look stupid if their GPS fails.

Precise navigation by compass only works thanks to the magnetic model. It describes the earth's magnetic field. Like how the magnetic north pole relates to the geographic north pole. Because the two are by no means identical. On the contrary: the magnetic north pole - the place where the field lines of the earth's magnetic field hit the earth vertically - is several hundred kilometers away from the geographic one. And he wanders. Even faster and faster in recent years. He no longer wanders, he runs.

Magnetic poles are not exactly opposite each other

The earth's magnetic field is important for all life. It protects against deadly radiation from space. And some animals use it for orientation - including us humans since we invented the compass. Since we now want to navigate very precisely on our travels around the globe, scientists have developed the world magnet model. So that we not only know roughly, but exactly where north is.

For this purpose, the model not only describes where the magnetic poles are currently located, but also how the magnetic field lines run, on which the compass aligns. Because their network, which spans the globe from north to south pole, is by no means symmetrical. Magnetic poles are not exactly opposite one another, nor do they move in lockstep. And the network of field lines has dents: They do not run in a straight line everywhere, the field strength is weaker in some places than elsewhere.

This has to do with the cause of the magnetic field: It is created by movements inside the earth. Heat rises from the solid core of iron and nickel, which is up to 5000 degrees hot, and leads to convection currents in the outer, liquid core, which is also largely made of iron. Material penetrates to the outside, cools down again and sinks back into deeper layers in a cycle. Because of the earth's rotation, there are also lateral movements. And because the material is electrically conductive, the magnetic field is formed around our home planet.

The North Pole has been migrating 50 kilometers a year since the 1990s

"You can imagine the circulation like boiling water in a pot," says Achim Morschhauser, research assistant at the Niemegk geomagnetic observatory of the German Research Center for Geosciences (GFZ) in Potsdam. "The heat rises from below and keeps everything in motion. And the magnetic field lines are linked to these movements. Like spaghetti that is thrown into the boiling water, they too are continually shifted."

It is a dynamic system with many irregularities in which movements alternate with countermovements. In extreme cases, there is even a complete reversal of polarity: The magnetic north pole then becomes the south pole and vice versa. Strictly speaking, the North Pole is actually a South Pole from a magnetic point of view. On average, this happens every 250,000 years, as analyzes of magnetized iron particles in old rock layers have shown. The Earth was last reversed 780,000 years ago - so the next one seems overdue.

The frenzy of the North Pole may even be a harbinger of this. While it covered ten to 15 kilometers per year in the course of the 20th century, moving in a relatively straight line from northern Canada through the Arctic Sea towards eastern Siberia, it has accelerated to over 50 kilometers per year since the 1990s. However, this does not have to result in polarity reversal. Some researchers also believe that the reason for his hurry lies in a 400-kilometer-wide horizontal stream of liquid iron, which they discovered two years ago 3,000 kilometers below Canada and Russia and which travels 40 kilometers a year towards Europe - three times faster than the material in the outer core of the earth usually flows.

Little is known about the interior of the earth

"In theory, the pole can change its direction of movement at any time, as it did several times in the 19th century," says Achim Morschhauser. "That's where the problem lies: We don't know enough about the convection currents in the Earth's core to predict such effects."

In fact, research still knows less about the interior of the earth than about that of the sun. So-called geomagnetic impulses, comparatively sudden peaks in the circulation in the earth's core, can occur in a similarly unforeseen way. Like particularly large bubbles in the saucepan, these outbreaks cause strong disturbances in the earth's magnetic field.

Other distortions are of longer duration: For almost 200 years - Alexander von Humboldt noted this at the time - we have known that the magnetic field over the South Atlantic, including South America and South Africa, is particularly weak. Satellites that fly over this region - but also living beings on the ground - are exposed to increased radiation from space. Experts call this the "South Atlantic Anomaly". Similar to the acceleration of the North Pole, it could also herald a polarity reversal. But it doesn't have to. The magnetic field has often recovered from such weak phases.

Usually the model is only updated every five years

In any case, such effects mean that the geophysicists now update their model prematurely. Usually they do this every five years: The model describes the current state and extrapolates how the field will develop in the following years - where, for example, the North Pole will move. To do this, the researchers use measurement data from satellites and terrestrial observatories that are distributed across the globe.

"But the forecasts are linear," says Morschhauser. "If there is a short-term anomaly, the forecast is no longer correct." In 2016, for example, just a year after the researchers last updated their model, a violent geomagnetic impulse occurred under South America, which causes the actual development to deviate from the forecast. "Since then, the mistake has grown bigger and bigger," says Arnaud Chaulliat from the University of Boulder Colorado, who is working on the world magnet model, the journal "Nature".

Now the threshold of tolerance has been reached. Those responsible for the world magnet model must act. Otherwise the deviations in the navigation will be so great that a pilot from the USA would possibly end up in Luckenwalde instead of in Berlin on a transatlantic flight using a compass bearing.

Now new: We give you 4 weeks of Tagesspiegel Plus! To home page