Scientists have discovered groundwater pumps tilted the planet 80 centimetres east between 1993 and 2010 alone. Previous climate models suggest between that time period we pumped 2,150 gigatons of groundwater - the equivalent weight of 5.5 million Empire State Buildings, or six millimetres of sea level rise.
The planet turns around a point, known as its rotational pole, and moving masses of water around the planet has shifted its balance. Experts at Seoul National University compared the phenomenon to adding a tiny bit of weight to a spinning top.
Groundwater may be pumped to irrigate crops, mines or used at home. Changes in water distribution have been known to effect the globe’s tilt since 2016, but at the time scientists only studied the shift in the context of ice sheets and glaciers' journeys.
Those numbers didn’t stack up. When the South Korean university factored in the 2,150 gigatons of groundwater it all started to make sense.
Until the discovery, the model was off by 78.5 centimetres, or 4.3 centimetres of water drift a year. Redistributing water is most affecting when conducted in the midlatitudes - the most temperate areas of the earth that lie just beneath the north pole and above the south pole.
The northern midlatitude includes the bottom of the UK, mainland Europe, the central portion of the United States, and the top of India. The southern midlatitude comprises the majority of Chile and Argentina, South Africa, and south Australia, and New Zealand.
During the study period the most water was distributed in western North America and north-western Indian, both at midlatitudes. Despite the “concerning” results, experts say countries in the sensitive regions could theoretically correct the Earth’s drift but only if conservation methods are sustained for decades.
The seasons are not at risk of changing because the rotational pole usually changes by several metres within a year. However, a tilting Earth could impact our climate. Dr Ki-Weon Seo, a geophysicist at Seoul National University who led the study said: “Earth’s rotational pole actually changes a lot. Our study shows that among climate-related causes, the redistribution of groundwater actually has the largest impact on the drift of the rotational pole.
“I’m very glad to find the unexplained cause of the rotation pole drift. On the other hand, as a resident of Earth and a father, I’m concerned and surprised to see that pumping groundwater is another source of sea-level rise.
“Observing changes in Earth’s rotational pole is useful for understanding continent-scale water storage variations. Polar motion data are available from as early as the late 19th century. So, we can potentially use those data to understand continental water storage variations during the last 100 years.
"Were there any hydrological regime changes resulting from the warming climate? Polar motion could hold the answer.”
Dr Surendra Adhikari, a research scientist at NASA’s Jet Propulsion Laboratory, California, who was not involved in the study, said quantifying the role of groundwater pumping is major. Discussing the study published in American Geophysical Union, he said: “This is a nice contribution and an important documentation for sure.
“They’ve quantified the role of groundwater pumping on polar motion, and it’s pretty significant.”
