Tag Archives: magnetic pole

This map shows the location of the north magnetic pole (white star) and the magnetic declination (contour interval 2 degrees) at the beginning of 2019. Credit: NOAA NCEI/CIRES.

Magnetic north pole finally gets a much needed update

This map shows the location of the north magnetic pole (white star) and the magnetic declination (contour interval 2 degrees) at the beginning of 2019. Credit: NOAA NCEI/CIRES.

This map shows the location of the north magnetic pole (white star) and the magnetic declination (contour interval 2 degrees) at the beginning of 2019. Credit: NOAA NCEI/CIRES.

Earth’s northern magnetic pole isn’t fixed but, rather, is in a perpetual motion driven by the movement of the planet’s liquid outer core. In the last couple of decades, scientists have noticed that the northern magnetic pole has been shifting away from the Canadian Arctic toward Siberia at an unprecedented rate. This anomalous variation has forced scientists at the National Centers for Environmental Information to publish their update to the World Magnetic Model (WMM) a year early in order to avoid significant inaccuracies in navigation and positioning. The WMM is used by everything from smartphones to the military.

The planet’s outer core is formed of liquid iron which constantly moves as the planet’s interior gradually cools down. This motion creates electric currents as electrons move through the liquid and, in the process, the energy of the fluid is converted into a magnetic field. If we imagined that Earth’s magnetic field is similar to a bar magnet (or dipole), then we can locate a geomagnetic north and south pole. However, this is an oversimplification of the complexity and variation of Earth’s true magnetic field.

Confusingly, scientists refer to the places where the planet’s magnetic field is vertical as the north and south magnetic poles. If you were standing over the north magnetic pole with a compass, the needle would dip and point towards the south pole, hence its other name: the magnetic dip pole. Over the south magnetic pole, the compass needle would try to point upward.

The northern dipole is roughly off the northwest coast of Greenland and its position has changed very little over the last century. The same can’t be said about the northern dip pole (true magnetic north pole), which has marched north by hundreds of miles in the last couple of decades. Up until the 1950s, the north magnetic pole had been moving at a rate of about 11 km (7 miles) per year but since the 1990s, this rate has jumped to about 54 km (34 miles) per year. Strangely, the south magnetic pole has shifted very little during this time.

Credit: University of Kyoto.

Scientists aren’t sure what causes this anomaly but the leading theory is that surges and flows in the swirl of liquid iron in the core are creating a tug between two magnetic patches: one under northern Canada and one under Siberia. The latter patch seems like its exerting more influence, hence the rapid shift of the magnetic north towards it.

Historically, the WMM has been updated every five years in order to keep up with these movements. The most recent update was scheduled for 2020 but researchers at the National Centers for Environmental Information — a collaboration between NOAA and the British Geological Survey — decided that it had to be released much sooner so as not to disrupt navigation, especially over the Arctic. The new model was pre-released online in October 2018 but its official release was delayed by a 35-day government shutdown. It’s only recently, after President Trump temporarily lifted the shutdown on January 25, that the WMM has finally been updated. 

The new model has the North Pole a good 25 miles away from the one previously predicted. This gross discrepancy means that updates in the future will have to be made much more often than before, preferably yearly. But while the WMM is also incorporated by things like Google Maps, regular folks shouldn’t worry too much since the north magnetic pole’s movements aren’t all that important for latitudes below 55 degrees.

Credit: University of Kyoto.

The magnetic North Pole has shifted, but we can’t update it because of the US government shutdown

Credit: University of Kyoto.

Credit: University of Kyoto.

Hundreds of miles beneath our feet, floating molten liquid is churning away, driving the planet’s magnetic field like a huge electromagnet. It creates our planet’s north and south magnetic poles. These poles do not correspond to the geographic poles, which mark the ends of Earth’s axis of rotation. In fact, their location changes — daily. What’s more, the magnetic poles even flip from time to time. 

Scientists have known this for quite a while and have tracking magnetic pole migrations with high precision for well over a century. This means you shouldn’t be worried about click-bait headlines that announce magnetic pole shifts as something out of the ordinary or even potentially catastrophic. It’s all totally harmless. But what seems to be happening in the last decade is an acceleration in the rate at which the North magnetic pole is moving towards the direction of Siberia and away from Canada.

True North is relative

Historically, researchers recalculate the position of the magnetic North Pole every five years, which is then synced with global navigation systems, such as GPS. The World Magnetic Model is supervised by NOAA and the British Geological Survey, and its most recent update was supposed to happen on January 15 — but it didn’t. The reason behind it is that NOAA, a US federal agency, is currently inactive due to the ongoing government shutdown.

Credit: NOAA.

Credit: NOAA Website screenshot.

For most of the previous century, the pole has moved around nine miles each year. However, since the 1990s, the migration has sped up to 35 miles a year. Over the last 150 years, the magnetic pole has crept north over 1,000 kilometers. It’s not clear why this acceleration is occurring due to gaps in our knowledge of how the planet’s core behaves. One leading hypothesis suggests that liquid molten iron under Canada is being dragged toward Siberia. In the meantime, the magnetic South Pole has barely moved, which is another mystery.

What’s more, a geomagnetic pulse occurred beneath South America in 2016. That was right after a 2015 update to the World Magnetic Model, prompting scientists to schedule a revision earlier than the planned 2020 update. This update should have been online this week were it not for the government shutdown. In the meantime, those engaged in navigation requiring great precision around the North Pole will have to wait — and it’s anybody’s guess for how long.

The new model has the North Pole a good 25 miles away from the one previously predicted. This gross discrepancy means that updates in the future will have to be made much more often than before, preferably yearly. Yet normal folks shouldn’t be too worried since the error gets smaller and smaller the farther away you get from the North Pole. If you live in the United States, your compass should be pointing northward as before with reasonable accuracy.

 

Credit: Los Angeles Air Force Base.

Earth’s magnetic poles might flip a lot faster than we thought — and we’re woefully unprepared

Credit: Los Angeles Air Force Base.

Credit: Los Angeles Air Force Base.

Earth can be likened to one big, planetary magnet. Likewise, Earth’s magnetic field is similar to that of a bar magnet tilted 11 degrees from the spin axis of the Earth. The magnetic field serves to deflect most of the solar wind, whose charged particles would otherwise strip away the ozone layer that protects the Earth from harmful ultraviolet radiation. But were you to use a compass at varied points throughout history, you would be in for a huge surprise, like seeing the compass’ needle pointing in the opposite direction than expected. When South becomes North and North becomes South, all sorts of unexpected and dangerous things can happen. This has happened many times throughout Earths’ geological history, and a new study suggests that we’re not only overdue for a pole reversal but that such events happen much faster and suddenly than previously thought.

The Earth’s magnetic field looks like that which would be produced by placing a bar magnet at the center of the Earth, with the North Magnetic Pole corresponding to the South Geographic Pole and vice versa. The Earth’s magnetic dipole originates in swirling currents of molten iron deep in the Earth’s core, and extends more than 10 Earth radii, or 63.7 million meters out into space on the side facing the Sun, and all the way to the Moon’s orbit, at 384.4 million meters on the opposite side. Magnetic field lines loop out of the South Geographic Pole and into the North Geographic Pole.

magnetic field

Credit: NASA Cosmos.

There are currents that guide the molten iron inside the planet’s core and, consequently, the magnetic poles can move or shift over time, losing or gaining strength. Scientists not only know that the magnetic field’s intensity changes over time, but they also know when dramatic shifts in intensity or pole reversal occurred. That’s because such events are recorded in the “frozen” ferromagnetic (or, more accurately, ferrimagnetic) minerals of consolidated sedimentary deposits or cooled volcanic flows on land.

It’s from these records that geologists learned that the last magnetic reversal took place 786,000 years ago. It happened very quickly, too, occurring in less than 100 years.

However, there are also dramatic reversals in field polarity, which occur more frequently. The challenge in pinpointing such events lies in the fact that igneous rocks do not capture the fine movements that lead up to a reversal. Andrew Roberts from the Australian National University (ANU) and colleagues found a workaround by studying stalagmite growing on the floor of a cave in southwestern China. A stalagmite is a type of rock formation that rises from the floor of a cave due to the accumulation of material deposited on the floor from ceiling drippings — given its slow growth, such formations offer the perfect opportunity to study slight variations in Earth’s magnetic field along the years.

The stalagmite, which is one meter in length and eight centimeters in diameter, has a candle-like shape and ranges in color from yellow to dark brown. Researchers cut it into 190 pieces, analyzing each with a high-res cryogenic magnetometer to make a snapshot of Earth’s magnetic field direction and strength as they stood from 107,000 to 91,000 years ago.

Writing in the Proceedings of the National Academy of Sciences, the authors of the new study found a brief pole reversal that occurred about 98,000 years ago and lasted for a century, maybe two. That’s a lot faster than scientists had guessed. Previously, scientists used to think it would take several thousands of years for the poles to change.

“The record provides important insights into ancient magnetic field behaviour, which has turned out to vary much more rapidly than previously thought,” Professor Roberts said.

This is bad news for a technologically-dependent species such as ourselves. Every pole reversal is joined by a weakening of the field and because the field’s intensity is bound to decrease considerably, much more radiation from space will be able to reach the planet’s surface than it does today. However, life on Earth shouldn’t be affected too much by this directly — humanity has lived through several pole reversals and we’re still here. Likewise, there were no mass extinction events coinciding with a pole reversal that scientists could find.

However, much has changed since the last time the planet’s magnetic field weakened by this much. For one, much of our existence is predicated on not only electrical power but also satellite-based communications, which nowadays are synced so much with the power grid that the two are basically inseparable. If our fleet of satellites was to suddenly come offline, much the world could suffer blackouts which could last for years. In the ensuing chaos, it’s anyone’s guess what would happen next.

Even today with Earth’s magnetic field at full strength, solar weather can pose a threat to sensitive electronics.

“Hopefully such an event is a long way in the future and we can develop future technologies to avoid huge damage, where possible, from such events,” Professor Roberts said in a statement.

No evidence to say that Earth’s magnetic pole is reversing, new study concludes

In recent years, the scientific community has closely followed the evolution of the Earth’s magnetic field, with some scientists finding clues of a sign of an incoming magnetic pole reversal (something which also spurred a hodgepodge of conspiracy theories). However, a new study reports that what we’re seeing now is probably not a precursor of a magnetic pole reversal.

The South Atlantic Anomaly. Image credits: NASA.

The Earth’s magnetic field is crucial for life on the planet, serving as a shield against hazardous radiation from space, especially coming from the Sun. Since 1840, scientists have been consistently monitoring this magnetic field, and since then, the global strength of the magnetic field has decayed at a rate of about five percent per century. Following this continuous decrease, a significant anomaly has emerged, called the South Atlantic Anomaly.

This anomaly represents an area of an abnormally weak magnetic field — think of it as a dip in the Earth’s magnetic defenses. Here, protection from harmful radiation from space is reduced, which has several unfortunate consequences (for instance, satellites in the area are more likely to suffer from communication blackouts and passengers on flights around the area are subjected to more radiation).

Within the research community, some have interpreted this anomaly as a sign of an incoming pole reversal. If this were the case, it wouldn’t really be surprising — the Earth’s magnetic field is constantly changing, and the way which it changes also changes. As a result, in the Earth’s geological history, magnetic pole reversals have been quite common, and we know this by studying geological proxies — magnetic minerals in the rocks and sediments “record” the orientation and strength of the Earth’s magnetic field at the time of rock formation. By dating the rocks, we can know how the magnetic field evolved, and we have a pretty good idea on how this field evolved through the ages. However, we don’t really know when the next reversal will come.

[panel style=”panel-default” title=”Chrons” footer=””]The Earth’s field has alternated between periods of normal polarity, in which the predominant direction of the field was the same as the present direction, and reverse polarity, in which it was the opposite. These periods are called chrons. The duration of chrons isn’t fixed, though the average time seems to be 450,000 years. The reversals themselves typically take between 1,000 and 10,000 years. However, the last one, which happened 780,000 years ago, happened very quickly — quite possibly in less than 100 years. It’s not really possible to predict these shifts.[/panel]

 Image via Wiki Commons.

 

Within their new study, scientists have reconstructed past changes in Earth’s magnetic field using paleomagnetic data from sediment cores and volcanic rocks from across the globe. They found a specifically good record for the time interval of 50,000 to 30,000 years before the present, including two magnetic dips that are similar to the South Atlantic Anomaly.

Neither of them led to a magnetic pole reversal, and as a result, the team concludes that the current anomaly is also unlikely to lead to a pole reversal. While this doesn’t rule out the possibility of a magnetic pole reversal at some point in the near future, it makes it much less likely. Monika Korte, co-author of the study, explained:

“Based on our observations of the past 50,000 years we conclude that the South Atlantic Anomaly cannot be interpreted as a sign for the beginning of a reversal of the poles. Times of the past that, unlike the beginning of the Laschamp excursion, showed patterns of the magnetic field like today were not followed by a pole reversal. After some time the anomalies disappeared.”

 

Richard Holme, Professor of Geomagnetism at the University of Liverpool and co-author, concludes:

“There has been speculation that we are about to experience a magnetic polar reversal or excursion. However, by studying the two most recent excursion events, we show that neither bear resemblance to current changes in the geomagnetic field and therefore it is probably unlikely that such an event is about to happen.

“Our research suggests instead that the current weakened field will recover without such an extreme event, and therefore is unlikely to reverse.”

The paper, `Earth’s magnetic field is probably not reversing’ has been published in Proceedings of the National Academy of Sciences (PNAS) doi:/10.1073/pnas.1722110115.