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Humans Moved So Much Water Around, We Changed the Earth’s Tilt
Now we're casually nudging planets, by accident.
Nobody really likes a work retreat, but hopefully you’ve never been attacked by a group of murderous sharks with an inexplicable talent for architecture. That’s the unplanned team-building exercise on a tech company’s work retreat in the 2016 SYFY original film Dam Sharks, when a group of bull sharks is forced up river during a storm and sets about eating everyone in sight and building a dam out of their bodies.
That might be the most horrifying way anyone has ever redistributed water, but it isn’t the most impressive. Humans have moved so much water around that we’ve raised global sea levels and changed the rotational axis of the planet, according to new research published in the journal Geophysical Research Letters.
How Water Redistribution Changes the Planet’s Axial Tilt
Archimedes once said, “Give me a lever and a place to stand and I will move the Earth.” Archimedes’ hubris might be unmatched, but the man was on to something. Between the years of 1993 and 2010, humans collectively moved so much water around that we shifted the planet’s North Pole by about 80 centimeters (31 inches).
Researchers knew that the movements of water across the face of the planet should have an effect on the degree of its tilt, but it wasn’t clear how much of that was driven by groundwater redistributed for agriculture. Prior research focused largely on the melting of sea ice and glaciers, but the new study demonstrates that agriculture and irrigation are significant contributors both to sea level rise and the shifting of the Earth’s tilt.
Researchers used a computer model of the Earth to simulate the movements of water and recreate the observed 80 centimeter tilt shift. When they plugged in only the water redistribution from natural processes, their model didn’t match up with reality. In fact, it shows a slight shift in the opposite direction. However, when they plugged in the roughly 2,150 gigatons of water pumped out of underground aquifers between 1993 and 2010, their model lined up nicely with reality. That 2,150 gigatons is equivalent to about a quarter of an inch of global sea level rise.
It wouldn’t be so bad if water stayed more or less in the same place, but it doesn’t. Only about half of the water coming out of your sprinkler makes its way back underground or into other freshwater sources. The rest evaporates, is taken up into the water cycle, and is redistributed to the planet’s oceanic hips. As a result, the Earth is spinning with a little bit of a limp.
Fortunately, the Earth wobbles back and forth due to a whole host of terrestrial and cosmic influences, and those couple of feet probably aren’t anything to worry about. It might be worth taking a moment to pause, however, and reflect on the awesome power we hold over our planet. Two and a half feet of drift probably isn’t going to hurt us, but that’s a pretty big change to happen accidentally.
If sharks really figure out how to manipulate waterways, we’re in big trouble. Catch Dam Sharks streaming now on SYFY.