The Earth had been ‘slimming down’ by just under a mm a year following the Ice Age, which finished about 20,000 years ago, but global warming is now reversing this process.
Researchers have suggested that melting ice in Antarctica and Greenland is adding volume to the oceans, with the excess water gravitating towards the equator and fattening the planet in its widest part. During the Ice Age, (geological period of long-term reduction in the temperature of the Earth’s surface and atmosphere), the weight of ice sheets was so great that they deformed the Earth’s crust and mantle, causing it to bulge at the middle.
The Earth isn’t completely spherical -- land at the North Pole is a number of km nearer to the core of the planet than land at the Equator.
And it was believed that the rebound effect following the Ice Age would result in our planet becoming more of a perfect sphere.
According to National Geographic, the ‘bulge’ at the Equator had been shrinking by less than a millimetre a year. But by looking at measurements from the Gravity Recovery and Climate Experiment (GRACE) satellites, it was found that this effect was reversing.
"There’s something else going on that offsets [the shrinking of the Earth’s girth],” John Wahr, a geophysicist at the University of Colorado, told the Daily Mail.
The rate of melting ice at the North and South Poles -- which totals 382 billion tons of ice a year -- is counteracting the ‘slimming’ effect.
