True Polar Shift? Wandering magnetic pole could point to unsettled Earth core

The Arctic’s melting ice may be having a far deeper impact than expected. We’re seeing large, unexpected shifts in the magnetic north pole. And this could be symptomatic of changes deep within the Earth’s core. But could it also throw the entire planet off balance?

As with everything else about the biosphere that is our planet, Earth, the magnetic field is part of a subtly balanced and interlocked system.

And series of studies has shown the amount of ice lost off the Greenland landmass was 267 gigatons in 2017. In 1996, it was 97 gigatons. To put that in perspective, a single gigatonne is an ice-cube 1km wide, 1km tall and 1km long.

This change has been measured by satellites. Some photograph the melt, others use lasers to measure the height of the ice. Some sense the minute decrease in gravity caused by the loss of mass.

As this ice retreats, ocean currents are changing course. New shipping lanes are being opened to Canada’s north. The salinity of the surrounding sea is being reduced.

But it now appears there is more going on.

Greenland isn’t as heavy as it was.

This means the pressure it applied to the veins of magma pulsing deep below the Earth’s surface has reduced.

And this swirling mass of molten iron is shifting.

Faster.

In new directions.

This could account for the highly erratic shift in the position of magnetic north.
But it also could give the whole planet an unexpected shake-up.

‘TRUE POLAR WANDER’
This pale blue dot wandering through space is locked in an internal feedback loop.

What happens to one aspect of this little world affects another, which — in turn — affects another.

A 2018 study in the science journal Geophysical Research Letters examined fossil signatures found deep in ocean sediments around the Hawaiian Islands.

It suggests the Earth’s magnetic field isn’t the only thing to occasionally undergo a dramatic shift.

The same can be said of the Earth’s surface.

“The Hawaiian hot spot was fixed, relative to the spin axis, from about 48 million years ago to about 12 million years ago, but it was fixed at a latitude farther north than we find it today,” said Daniel Woodworth, a graduate student of Rice University. “By comparing the Hawaiian hot spot to the rest of the Earth, we can see that shift in location was reflected in the rest of the Earth and is superimposed on the motion of tectonic plates. That tells us that the entire Earth moved, relative to the spin axis, which we interpret to be true polar wander.”

Essentially, the Earth’s surface was thrown off-kilter.

And that was probably caused by a magma ‘blob’ in the mantle beneath the crust.

Generally, everything is kept relatively consistent by the balancing effect of Earth’s rotational centrifugal force. But not always.

Magma flows can shift. Its consistency in certain places can change.

“Imagine you have really, really cold syrup, and you’re putting it on hot pancakes,” Gordon, the W.M. Keck Professor of Rice University’s Earth, Environmental and Planetary Science said. “As you pour it, you temporarily have a little pile in the centre, where it doesn’t instantly flatten out because of the viscosity of the cold syrup. We think the dense anomalies in the mantle are like that little temporary pile, only the viscosities are much higher in the lower mantle. Like the syrup, it will eventually deform, but it takes a really, really long time to do so.”

If these magma blobs are big enough, they can unsettle the planet’s spin. While the Earth’s angle relative to the Sun doesn’t change, the position of the continents does.

Essentially, centrifugal force pulls this ‘blob’ of magma closer to the equator. From the perspective of the continents, the equator appears to shift.

The study said the last time this happened about 3.2 million years ago, it moved Greenland and parts of Europe and North America further north.

“That may have triggered what we call the ice age,” Professor Gordon said.

GEOLOGICAL PRESSURE COOKER
Less than 100 years ago, the idea that the Earth’s continents could shift position was considered ludicrous. But the discovery of plate tectonics changed that virtually overnight.

The Earth’s outer crust is a system of solid plates floating on a mantle of highly pressurised, superhot rock beneath. These cycle constantly, as do the continents they contain, through the tectonic forces expressed through volcanoes and earthquakes. It may just be a matter of a few centimetres each year. But it's already been enough for the GPS network to have to be reset to avoid navigational errors.
It’s easy to forget the driving force for all of this as it is far, far out of sight.

The ebb and flow of the molten metals of the Earth’s mantle and core.

As our planet rotates around its axis, this liquid iron is churned.

And that’s a good thing.

The constant interaction of iron on iron generates electric currents that power the magnetic field that shields the surface of the Earth. This ‘bounces’ the worst of the Sun’s radiation, and even powerful cosmic rays.

Likewise there is a constant interaction between the molten core and the solid crust.

Magma can pool, shift and cool as the crust above changes.

It can result in areas becoming more — or less — dense in magnetic material.

And it can affect the circulation of molten magma around it.

Such changes could account for mysteries such as the powerful South Atlantic magnetic anomaly that has claimed several satellites in recent years.

It also changes the ‘balance’ of the Earth’s magnetic field, causing the location of the North and South poles to ‘wander’.

They can even ‘flip’.

“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’,” A NASA commentary reads.
But the implication now is the balance of the Earth’s crust itself can be unsettled if the magma below shifts and changes in unexpected ways.

ANTARCTIC WILDCARD
Just as the tectonic plates react to shifts in Greenland’s weight, so too will they be affected by Antarctica. And ice is melting in Antarctica faster than ever before — about six times more per year now than 40 years ago.

As this ice sits on land, the run-off is leading to increasingly high sea levels worldwide.

Already, Antarctic melting has raised global sea levels more than 1.4 centimetres between 1979 and 2017, a report in this week’s edition of the science journal Proceedings of the National Academy of Sciences (PNAS).

A rise of 1.8 metres by 2100, as some scientists forecast in worst-case scenarios, would flood many coastal cities that are home to millions of people around the world, previous research has shown.

It would also greatly reduce the weight of ice sitting on Antarctica, and redistribute that weight on the ocean floor — and the magma beneath.

For the current study, researchers embarked on the longest-ever assessment of ice mass in the Antarctic, across 18 geographic regions. Data came from high-resolution aerial photographs taken by NASA planes, along with satellite radar from multiple space agencies.

Researchers discovered that from 1979 to 1990, Antarctica shed an average of 40 billion tons of ice mass annually. By the years 2009 to 2017, the ice loss had increased more than sixfold, to 252 billion tons per year.

Even more worrying, researchers found that areas that were once considered “stable and immune to change” in East Antarctica, are shedding quite a lot of ice, too, said the study.

The total amount of ice in the Antarctic, if it all melted, would be enough to raise sea level 57 metres. By far, the most ice in Antarctica is concentrated in the east, where there is enough sea ice to drive 52 metres of sea level rise, compared to about 5m in the entire West Antarctic ice sheet.

The latest research shows that East Antarctic melting deserves “closer attention,” according to the PNAS report.