We Finally Know Why The North Pole Is Moving East

We Finally Know Why The North Pole Is Moving East







Relationship between continental water storage and the wobble in Earth's spin axis. Image: NASA/JPL-Caltech

Relationship between continental water storage and the wobble in Earth’s spin axis. Image: NASA/JPL-Caltech

But it turns out ice sheets don’t tell the full story. By combining mass distribution models with data from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellite, Adhikari teased out another critical factor: the storage of water on land, and in particular, across Eurasia. Humans move tremendous volumes of groundwater through pumping, but also indirectly via climate change, which is causing some places to become drier and others wetter.

Taken together, these changes are causing our planet to tip over ever so slightly.

Land water storage is also directly related to another curious feature of our planet’s spin axis: a decadal oscillation from east to west. The poles don’t migrate along a straight line — rather, they trace a sine curve that wobbles back and forth. “Here, for the first time ever, we have presented a plausible physical mechanism for this,” Adhikari said.

And that mechanism points to an important reason for studying polar wander — reconstructing past climate. We have polar migration records stretching back to the beginning of the 20th century, and now, we know that these records are related to patterns of wetness and dryness.

“This means, you can start answering questions like, during the 20th century, was there an intensification of drought or wetness in some region of the planet,” Adhikari said. Which is exactly what Adhikari is now starting to do, in collaboration with hydrologists at the JPL.

Perhaps most importantly, the findings offer a powerful new piece of evidence humans have become the dominant force of nature on the planet. Later this year, a group of scientists will formally review a proposal to move us into a new geologic epoch — an age of humans and machines dubbed “the Anthropocene”. I can’t help but feel like the revelation that we’re shifting the very axis on which our world spins only strengthens the case.