Humanity’s insatiable thirst for water has consequences of planetary proportions, a new study reveals: constant groundwater pumping has shifted enough mass to raise ocean levels and change the planet’s tilt.
Previous studies of Advancing Earth and Space Sciences (“Global depletion of groundwater resources“) have estimated that, from 1993 to 2020, humans removed from aquifers about 2.15 trillion tons of water – a huge amount that was first channeled into crops and water supply networks, before finally ending up in the sea.
In fact, this water was enough to raise the level of the oceans by 6 millimeters, estimates the new study in the journal Geophysical Research Letters (“Drift of Earth’s Pole Confirms Groundwater Depletion as a Significant Contributor to Global Sea Level Rise 1993–2010“).
The research team, split between South Korea, the US and Hong Kong, wanted to examine whether shifting all that mass affected the Earth’s rotation.
It is also known that the distribution of the planet’s mass affects the position of the geographic poles, just as a spinning top spins in a different way if one adds a little extra mass to it.
Previous Research of Science Advances (“Climate-driven polar motion: 2003–2015“) of 2016 had also shown that the melting of the Greenland ice sheet due to climate change has shifted the axis of rotation by several meters.
Groundwater pumping has a smaller but not negligible effect, the new calculations show: between 1993 and 2020 alone, humans displaced enough water to move the North Pole 80cm eastward.
To arrive at this figure, the researchers used models of the planet’s rotation, which showed that the observed shift in the geographic poles cannot be explained without taking into account water pumped from boreholes.
However, the phenomenon is not strong enough to change the seasons, since the geographic poles shift several meters each year due to other factors that cause mass redistribution.
Such factors include the movement of the Earth’s mantle and core, the “rebounding” of areas previously covered by glaciers, and even strong earthquakes.
