New research shows that persistent groundwater extraction over more than a decade has shifted the axis on which our planet rotates.
Humans’ unquenchable thirst for groundwater has sucked so much liquid from subsurface reserves that it’s affecting Earth’s tilt, according to a new study.
Groundwater provides drinking water for people and livestock, and it helps with crop irrigation when rain is scarce. However, the new research shows that persistent groundwater extraction over more than a decade shifted the axis on which our planet rotates, tipping it over to the east at a rate of about 1.7 inches (4.3 centimeters) per year.
That shift is even observable on Earth’s surface, as it contributes to global sea level rise, researchers reported in the study published June 15 in the journal Geophysical Research Letters.
“Earth’s rotational pole actually changes a lot,” said lead study author Ki-Weon Seo, a professor in the department of Earth science education at Seoul National University in South Korea, in a news release. “Our study shows that among climate-related causes, the redistribution of groundwater actually has the largest impact on the drift of the rotational pole.” …
The researchers then evaluated sea level variations “using the groundwater mass change from the model,” to pinpoint how much of the axis shift was caused by groundwater pumping alone, Seo said.
The redistribution of groundwater tilted Earth’s rotational axis east by more than 31 inches (78.7 centimeters) in just under two decades, according to the models. The most notable driver of long-term variations in the rotational axis was already known to be mantle flow — the movement of molten rock in the layer between Earth’s crust and outer core. The new modeling reveals that groundwater extraction is the second most significant factor, Seo said.
Is it just me, or is 31 inches over two decades an incredibly frightening number?
The observed drift since humans have been able to make these observations is that our natural tilt fluctuates 2⁰ over 40,000 or so years. Which comes out to about 576 inches a year (I didnt do the maths, im basing this off the speed that the polar circle is currently drifting, not sure if thats the best way to approximate earths tilt vs. orbital plane). So comparing that to 31 inches of drift per year due to water, this seems to account for roughly 5% of the observed axial drift of the earth.
It’s dawning on me that our most current astronomical measurements and this study are drawing on the same time period of observations, and that most of the water humans have moved around on earth likely occurred before and/or after the decades this model accounts for. So yeah, it’s troubling.
Haven’t humans been extracting groundwater (i.e. drilling wells for drinking water & irrigation) since prehistoric times? No doubt our usage has grown in recent decades. Our use of nearly all resources has become much more intensive over time. But it’s not easy to see how civilization might exist away from immediately riparian areas without using groundwater.
