The Magnetic North Pole is Shifting Fast – Is This the First Sign of an Impending Pole Reversal?
Schematic illustration of Earth's magnetic field -- Earth's polarity is not a constant. It moves and shifts. Geophysicists are pretty sure that the reason Earth has a magnetic field is because its solid iron core is surrounded by a fluid ocean of hot, liquid metal. The flow of liquid iron in Earth's core creates electric currents, which in turn create the magnetic field. So while parts of Earth's outer core are too deep for scientists to measure directly, we can infer movement in the core by observing changes in the magnetic field. (Credit: Oregon State University, Joseph Stoner) (Image Credit: Peter Reid, University of Edinburgh)
The Magnetic North Pole is Shifting Fast – Is This the First Sign of an Impending Pole Reversal?
After some 400 years of relative stability, Earth's North Magnetic Pole has moved nearly 1,100 kilometers out into the Arctic Ocean during the last century and at its present rate could move from northern Canada to Siberia within the next half-century.
If that happens, Alaska may be in danger of losing one of its most stunning natural phenomena - the Northern Lights.
But the surprisingly rapid movement of the magnetic pole doesn't necessarily mean that our planet is going through a large-scale change that would result in the reversal of the Earth's magnetic field according to Oregon State University paleomagnetist Joseph Stoner.
"This may be part of a normal oscillation and it will eventually migrate back toward Canada," said Stoner, an assistant professor in OSU's College of Oceanic and Atmospheric Sciences. "There is a lot of variability in its movement."
Calculations of the North Magnetic Pole's location from historical records goes back only about 400 years, while polar observations trace back to John Ross in 1838 at the west coast of Boothia Peninsula. To track its history beyond that, scientists have to dig into the Earth to look for clues.
Stoner and his colleagues have examined the sediment record from several Arctic lakes. These sediments - magnetic particles called magnetite - record the Earth's magnetic field at the time they were deposited. Using carbon dating and other technologies - including layer counting - the scientists can determine approximately when the sediments were deposited and track changes in the magnetic field.
The Earth last went through a magnetic reversal some 780,000 years ago. These episodic reversals, in which south becomes north and vice versa, take thousands of years and are the result of complex changes in the Earth's outer core. Liquid iron within the core generates the magnetic field that blankets the planet.
Because of that field, a compass reading of north in Oregon will be approximately 17 degrees east from "true geographic north." In Florida, farther away and more in line with the poles, the declination is only 4-5 degrees west.
The Northern Lights, which are triggered by the sun and fixed in position by the magnetic field, drift with the movement of the North Magnetic Pole and may soon be visible in more southerly parts of Siberia and Europe - and less so in northern Canada and Alaska.
In their research, funded by the National Science Foundation, Stoner and his colleagues took core samples from several lakes, but focused on Sawtooth Lake and Murray Lake on Ellesmere Island in the Canadian Arctic. These lakes, about 40 to 80 meters deep, are covered by 2-3 meters of ice. The researchers drill through the ice, extend their corer down through the water, and retrieve sediment cores about five meters deep from the bottom of the lakes.
The 5-meter core samples provide sediments deposited up to about 5,000 years ago. Below that is bedrock, scoured clean by ice about 7,000 to 8,000 years ago.
"The conditions there give us nice age control," Stoner said. "One of the problems with tracking the movement of the North Magnetic Pole has been tying the changes in the magnetic field to time. There just hasn't been very good time constraint. But these sediments provide a reliable and reasonably tight timeline, having consistently been laid down at the rate of about one millimeter a year in annual layers.
"We're trying to get the chronology down to a decadal scale or better."
What their research has told Stoner and his colleagues is that the North Magnetic Pole has moved all over the place over the last few thousand years. In general, it moves back and forth between northern Canada and Siberia. But it also can veer sideways.
"There is a lot of variability in the polar motion," Stoner pointed out, "but it isn't something that occurs often. There appears to be a 'jerk' of the magnetic field that takes place every 500 years or so. The bottom line is that geomagnetic changes can be a lot more abrupt than we ever thought."
Shifts in the North Magnetic Pole are of interest beyond the scientific community. Radiation influx is associated with the magnetic field, and charged particles streaming down through the atmosphere can affect airplane flights and telecommunications.
The National Oceanic and Atmospheric Administration (NOAA) models the Earth’s magnetic field through its World Magnetic Model (WMM). This is the official standard model used by the US Department of Defense (DoD), the UK Ministry of Defence, the North Atlantic Treaty Organization (NATO) and the International Hydrographic Organization (IHO). The model is used for navigation, attitude, and heading referencing systems that rely on the Earth’s geomagnetic field. It is also used widely in civilian navigation and heading systems.
The North Magnetic Pole has been shifting at such an unexpected rate recently that on March 21, 2018, NOAA issued the following statement to the users if the World Magnetic Model:
“This is to inform users that the WMM Gridded Variation (GV) error has recently exceeded the performance specification in the Arctic region. Other geographic areas and other model parameters are not affected. The increased GV error may adversely affect compass navigation in those areas… The WMM GV error is currently above the WMM performance specification… The GV error is largest in the Canadian Arctic Archipelago, Northern Greenland, parts of Northern Siberia, a large portion of Arctic Ocean and the Laptev Sea… This performance degradation is caused by fast-changing core flows in the North Polar region of the Earth’s outer core.”
Scientists have determined that Earth's magnetic field has flipped its polarity many times over the millennia. In other words, if you were alive about 800,000 years ago, and facing what we call north with a magnetic compass in your hand, the needle would point to 'south.' This is because a magnetic compass is calibrated based on Earth's poles. The N-S markings of a compass would be 180 degrees wrong if the polarity of today's magnetic field were reversed. Many doomsday theorists have tried to take this natural geological occurrence and suggest it could lead to Earth's destruction. But would there be any dramatic effects? The answer, from the geologic and fossil records we have from hundreds of past magnetic polarity reversals, seems to be 'no.'
Reversals are the rule, not the exception. Earth has settled in the last 20 million years into a pattern of a pole reversal about every 200,000 to 300,000 years, although it has been more than twice that long since the last reversal. A reversal happens over hundreds or thousands of years, and it is not exactly a clean back flip. Magnetic fields morph and push and pull at one another, with multiple poles emerging at odd latitudes throughout the process. Scientists estimate reversals have happened at least hundreds of times over the past three billion years. And while reversals have happened more frequently in "recent" years, when dinosaurs walked Earth a reversal was more likely to happen only about every one million years.
Sediment cores taken from deep ocean floors can tell scientists about magnetic polarity shifts, providing a direct link between magnetic field activity and the fossil record. The Earth's magnetic field determines the magnetization of lava as it is laid down on the ocean floor on either side of the Mid-Atlantic Rift where the North American and European continental plates are spreading apart. As the lava solidifies, it creates a record of the orientation of past magnetic fields much like a tape recorder records sound. The last time that Earth's poles flipped in a major reversal was about 780,000 years ago, in what scientists call the Brunhes-Matuyama reversal. The fossil record shows no drastic changes in plant or animal life. Deep ocean sediment cores from this period also indicate no changes in glacial activity, based on the amount of oxygen isotopes in the cores. This is also proof that a polarity reversal would not affect the rotation axis of Earth, as the planet's rotation axis tilt has a significant effect on climate and glaciation and any change would be evident in the glacial record.
Earth's polarity is not a constant. Unlike a classic bar magnet, or the decorative magnets on your refrigerator, the matter governing Earth's magnetic field moves around. Geophysicists are pretty sure that the reason Earth has a magnetic field is because its solid iron core is surrounded by a fluid ocean of hot, liquid metal. This process can also be modeled with supercomputers. Ours is, without hyperbole, a dynamic planet. The flow of liquid iron in Earth's core creates electric currents, which in turn create the magnetic field. So while parts of Earth's outer core are too deep for scientists to measure directly, we can infer movement in the core by observing changes in the magnetic field. The magnetic north pole has been creeping northward by more than 600 miles (1,100 km) since the early 19th century, when explorers first located it precisely. It is moving faster now, actually, as scientists estimate the pole is migrating northward about 40 miles per year, as opposed to about 10 miles per year in the early 20th century.
A doomsday hypothesis about a geomagnetic flip plays up fears about incoming solar activity. This suggestion mistakenly assumes that a pole reversal would momentarily leave Earth without the magnetic field that protects us from solar flares and coronal mass ejections from the sun. But, while Earth's magnetic field can indeed weaken and strengthen over time, there is no indication that it has ever disappeared completely. A weaker field would certainly lead to a small increase in solar radiation on Earth – as well as a beautiful display of aurora at lower latitudes - but nothing deadly. Moreover, even with a weakened magnetic field, Earth's thick atmosphere also offers protection against the sun's incoming particles.
The science shows that magnetic pole reversal is – in terms of geologic time scales – a common occurrence that happens gradually over millennia. While the conditions that cause polarity reversals are not entirely predictable – the North Pole's movement could subtly change direction, for instance – there is nothing in the millions of years of geologic record to suggest that any of the doomsday scenarios connected to a pole reversal should be taken seriously.
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