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We hear about a lot of extreme things happening as a result of climate change.
But the findings of a recent study published in the journal Geophysical Research Letters
are pretty over the top.
Santa might need to pack up and find a new apartment, because the study says climate change
is literally shifting the Earth’s axis and changing the location of the North Pole.
And the new study suggests it’s been doing it since at least the 90s.
The idea that the North Pole can move is nothing new.
It’s something we’ve been tracking actively for over a century, but we’ve known about
it for even longer.
You can picture the Earth more or less like a spinning top as it rotates around its axis.
And just like a top wobbles as it spins,
Earth’s axis is moving slightly this way or that in what’s known as polar motion.
A lot of this movement is pretty predictable.
It has to do with how all the stuff that makes up our planet --
from the mantle to the atmosphere to the oceans -- sloshes around over time.
For instance, the location of the poles varies annually due to the seasonal movement
of water vapor in the atmosphere between the Northern and Southern hemispheres.
And thanks mostly to pressure changes on the seafloor, the poles can also move
on a 433-day cycle known as the Chandler wobble.
Which also - coming soon - the name of my new TikTok dance.
Other changes happen on much longer timescales, influenced by things like glacial isostatic adjustment,
That’s the slight shifting of land that’s still getting used to the idea that the last ice age
is over and so it isn’t being smothered by humungous glaciers anymore.
But just over a decade ago, scientists noticed that the direction of the North Pole’s
drift had shifted dramatically in the mid-90s.
It started heading eastward, instead of south.
And it accelerated: between 1995 and 2020, the average speed of the drift
was seventeen times faster than from 1981 to 1995.
Which led scientists to ask: could the culprit be climate change?
The thinking was that the faster melting of glaciers beginning in the mid-90s could have caused enough
redistribution of the world’s water to set the Earth-top wobbling different than usual.
The key to finding out if this is the case is a pair of satellites launched into space in
2002 for a mission called the Gravity Recovery and Climate Experiment, or GRACE.
They allow us to accurately measure changes to the Earth’s gravity caused by the
location and movement of ice, snow, surface water, and groundwater.
Based on those observations, scientists have been able to show that
climate change-driven melting in Greenland caused the North Pole to drift eastward around
the year 2005.
Similarly, a shift in global patterns of wet and dry weather appears to have caused
westward North Pole drift around 2012.
But showing that glacial melt played a similar role in the 90s,
before the GRACE satellites were launched, has been more challenging.
In this new study, the researchers found a way to tackle that:
they came up with a technique that could extrapolate GRACE data back in time.
They modeled two scenarios of polar drift using this extrapolation technique.
One was based just on data from the 2000s,
while the other took into account the climate change we know happened in the 90s.
For the first scenario, they basically assumed what GRACE satellites observed
in the twenty-first century was also happening in the 80s and 90s.
That scenario didn’t end up with the poles in the right positions.
So next, they factored in records of accelerated ice melt during the 90s in key glacial regions
around the world.
If this one predicted polar drift correctly, it would suggest that the
climate change-driven ice melt during that period contributed to the movement of the poles.
And what do you know, it was this second model that correctly predicted
the way the North Pole wobbled in the mid-90s.
Now, the authors say that it’s possible there are other explanations for what moved
some of this water around and caused the unexpected polar drift.
But they’re not exactly news great either.
One possibility is that in some areas, the shift in terrestrial water was actually
more about humans using groundwater unsustainably for things like farming.
There’s one pretty neat outcome from the research, though: the authors think it might
be possible to use these methods to look even further back in time.
Instead of trying to predict the movement of the North Pole
based on known measurements of glacier loss,
they think we could perhaps use known measurements of the poles’ locations to
guess at how much of the world’s terrestrial water was lost earlier in the 20th century.
And that would allow them to reconstruct a history of how the Earth’s water moved
and melted during a time when we weren’t able to precisely measure it.
But in the meantime, we probably have another completely bonkers thing
to blame on climate change: knocking the Earth a little bit off its axis.
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