Experts at NASA’s Jet Propulsion Laboratory in California have tracked changed over the entire 20th century to explore what is scientifically known as “polar motion”.
The Earth is not like the globes you may find sitting on a desk. It is not a perfect sphere and doesn’t rotate smoothly while it spins – instead it drifts and wobbles.
NASA have broken down the three main reasons for this, the first being ‘glacial rebound’.
This happens when glaciers cover a larger area that causes the planet to be squeezed and bulge at the end of the ice.
As they melt the bulging changes shape and redistributes the Earth’s mass. Although this last happened 26,000 years ago the planet is still slowly changing shape.
The second reason is what scientists call ‘mantle convection’.
This theory is similar to the ice one that says the shifting is due to large rocks in the Earth's core moving over each other and making the planet wobble.
The third and final one is human influence. NASA says this is that of a rapidly warming environment thanks to climate change.
Greenland’s ice caps melting saw 7,500 gigatons of ice drift into the ocean. This weight change could have contributed to the wobble.
Eric Ivins of JPL said: “There is a geometrical effect that if you have a mass that is 45 degrees from the North Pole – which Greenland is – or the South Pole (like Patagonian glaciers), it will have a bigger impact on shifting Earth’s spin axis than a mass that is right near the pole.”
HOW THE EARTH IS 'WOBBLING'
The science behind NASA's discovery might be slightly confusing, but not when broken down in simple stages.
NASA think there are three contributing reasons behind the Earth wobbling. They are as follows…
The wobble does not pose a major threat to life. It does, however, create challenges for navigation.
But technology can compensate for our wobbly planet. You can see an interactive demo on NASA’s Polar Motion Simulator.
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