A study shows that groundwater extraction over several decades has caused the Earth’s axis to shift eastward by nearly 80 cm in 20 years.
The Earth’s rotation axis, the point around which the Earth spins, is not fixed. It moves in a process known as polar motion, where the position of the rotation axis changes relative to the Earth’s crust. This process can be visualized like a spinning top; if the weight distribution of the top changes, it will spin differently. The distribution of water on the planet operates similarly. As water shifts, it alters the way the Earth rotates, according to IFL Science on November 28.
Over-extraction of groundwater may impact the environment. (Photo: Sumeth c/Shutterstock)
“The rotation axis of the Earth is actually changing quite a lot,” Dr. Ki-Weon Seo, a geophysicist at Seoul National University, explained in a statement about the 2023 study published in Geophysical Research Letters. “Our research shows that among the climate-related causes, the redistribution of groundwater actually has the most significant impact on the drift of the rotation axis”, he said.
Groundwater is different from river and lake water. It is water hidden beneath the ground, accumulated from rain and other forms of precipitation. When water seeps into the soil, it gradually filters down into natural aquifers – underground reservoirs. This type of water is a crucial element of the water cycle as it provides moisture even during dry periods.
Today, about 50% of the world’s population relies on groundwater for drinking water and one-third of the world’s irrigation water. Traditionally, humans accessed this water through wells and boreholes. However, throughout the 20th century, modern societies began to exploit aquifers on a much larger scale. Research indicates that from 1993 to 2010, humans pumped 2,150 billion tons of groundwater.
In 2016, scientists warned that water distribution could change the Earth’s rotation. However, at that time, the phenomenon lacked details on how groundwater usage might be related to it.
Subsequently, Dr. Ki-Weon Seo’s research team modeled the observed changes in the drift of the Earth’s rotation axis and water movement. They ran multiple scenarios and found the only one that matched the drift rate of 4.3 cm per year corresponding to the previously calculated 2,150 billion tons of redistributed groundwater.
This study effectively quantified the role of groundwater pumping on polar motion and climate change. Although the polar shift caused by this type of extraction is unlikely to change how at-risk areas experience seasons, the polar shift could influence climate.
