Humans have pumped enough groundwater to tilt the Earth's axis of rotation, according to a new study. Groundwater pumped out of the ground and moved elsewhere to quench people’s thirst and aid their activities has altered the planet’s axis by nearly 80 cm to the east.
Published in the journal Geophysical Research Letters, the new study highlights that between 1993 and 2010, more than 2,000 gigatons of groundwater, equivalent to a global sea level rise of 6.24 mm, has been pumped out by humans, according to a press statement by Advancing Earth and Space Sciences. Sea level rise is one of the most significant phenomena associated with the warming climate.
In 2016, scientists discovered water's ability to change the Earth's rotation but groundwater‘s impact on changes in Earth’s rotation had not been considered. To fill this gap, Ki-Weon Seo, a geophysicist at Seoul National University, and his team examined how Earth’s axis of rotation is linked to the movement of water, the statement explains.
Earth's rotational pole is the point around which the planet rotates. The axis of rotation of the planet lies at this point and it moves in a process called polar motion, which is when the position of the Earth's rotational pole varies relative to the crust. The distribution of water on the planet affects how mass is distributed. Similar to adding a bit of weight to a spinning top, the Earth spinning movement differs a little as water is moved around, the statement adds.
In the researcher's model, the shift in the axis was not in line with the melting glaciers or ice caps. However, when the researchers considered 2,150 gigatons of groundwater redistribution, the model matched the observed drift. “Our study shows that among climate-related causes, the redistribution of groundwater actually has the largest impact on the drift of the rotational pole,” Seo said in the statement.
The study measured the role of groundwater pumping on polar motion, which is significant. The groundwater's location is crucial as it could significantly affect polar drift. Moreover, redistributing water from the midlatitudes has a greater impact on the rotational pole. Most water was redistributed in western North America and northwestern India during the study period. Both regions are midlatitudes areas.
These countries’ attempts to slow groundwater depletion, specifically in the sensitive regions, could theoretically alter the change in drift, but it’s only possible if such approaches are sustained for decades, Seo said in the statement.