Groundwater exploitation tilts the Earth’s axis

The Earth’s rotation pole, the point around which the Earth rotates, is not fixed. It moves in a process called polar motion, when the position of the rotating pole changes relative to the Earth’s crust. This process can be visualized as a spinning top; If the weight distribution of the gyro changes, it will spin differently. The distribution of water on the planet works similarly. When water moves, it changes the way the Earth rotates IFL Science on November 28.

“The Earth’s rotation pole actually changes 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 study shows that among climate-related causes, groundwater redistribution actually has the greatest impact on rotational pole drift,” he said.

Groundwater is different from river and lake water. It is water that is hidden underground and accumulates from rain and other forms of precipitation. As water seeps into the soil, it slowly seeps down into natural aquifers – underground tanks. This type of water is an important feature of the water cycle because it provides water even during periods of low rainfall.

Today, about 50% of the world’s population depends on groundwater for drinking water and one-third of the world’s irrigation water. Traditionally, people accessed this water through wells, boreholes, etc. However, during the 20th century, modern societies began exploiting underground water tanks on a much larger scale. Research shows that from 1993 to 2010, humans pumped 2,150 billion tons of groundwater.

In 2016, scientists warned that the distribution of water could change the Earth’s rotation. But at the time, the phenomenon lacked details about how groundwater use might be related to it.

Dr. Ki-Weon Seo’s team then modeled the observed changes in the drift of the Earth’s rotation pole and the movement of water. They ran multiple scenarios and found the only one that matched the previously calculated drift of 4.3 cm per year corresponding to the 2,150 billion tons of groundwater redistribution.

This study effectively quantifies the role of groundwater pumping in polar motion and climate change. While the pole shifts caused by this type of mining likely won’t change how at-risk areas experience the seasons, the pole shifts could impact climate.