The shocking reason why Earth's poles are wobbling
Saturday, April 9, 2016, 4:37 PM - You don't tend to think of Earth's axis as a thing that is drastically changeable. The planet's tilt toward the sun feels like a geophysical feature far beyond the impact of puny humans.
Which is why NASA's latest research into why Earth's north pole took a drastic turn around 2000 -- when the usual movement of the Earth's poles is typically slower -- should be the most worrisome.
"The bottom line is that climate change is driving the motion of the polar axis," study author Surendra Adhikari told Gizmodo.
Before 2000, the north pole spent most of the 20th Century moving toward Hudson Bay.
But at the turn of the millennium, the Earth's axis started moving abruptly east, heading now toward the British Isles at a rate of around 17 cm per year, which NASA says is about twice the normal.
New research from NASA's Jet Propulsion Laboratory suggests that's due to ice sheet melting in Greenland and Antarctica, and changes in the way water is stored on land -- which are due in large part to global warming caused by human activity.
NASA at first thought the melting of the ice sheets was enough to cause the new wobble, but subsequent calculations found that the combined effects of the decline in Greenland and Antarctic ice wouldn't have been enough to explain the speeding up of the pole's shift, nor its new direction.
The researchers then turned their eyes to Eurasia, found found their answer: A water deficit in the Indian subcontinent and the Caspian Sea.
Not only that, the reseachers examined the data gathered by satellites in the Gravity Recovery and Climate Experiment (GRACE), and found that dry years in Eurasia matched up with eastward swings of the pole, while wet years seemed synced to westward swings.
"This is much more than a simple correlation," study coauthor Erik Ivins said. "We have isolated the cause."
Aside from explaining the present behaviour of the poles, and how it relates to climate change, the new knowledge gleaned from the study could give a clearer picture of the past as well.
"That could tell us something about past climate -- whether the intensity of drought or wetness has amplified over time, and in which locations," Adhikari says.
The new study appears in the latest issue of Science Advances.