Depletion of groundwater has affected pole rotation drift: Study

By Yeter Ada Seko

ISTANBUL (AA) - The excessive extraction of groundwater for drinking and irrigation has caused an additional 1.57-inch (3.98-centimeter) shift in the Earth’s axis, according to a new study released Monday.

“This shift does not have an impact on climate change, but excessive use of groundwater due to climate change may have indirectly contributed to the shift,” said Ki-Weon Seo, a professor of earth sciences at Seoul National University in South Korea.

Academics from universities in South Korea, Australia, China, and the United States examined data from climate models that focused on polar movements between 1993 and 2010.

The data showed that a total of 2.15 gigatons of water equivalent to a 6.24-millimeter rise in sea levels was extracted from underground.

The study emphasized that water distribution on Earth is affected by the melting of polar and mountain glaciers and groundwater depletion.

This movement occurred towards the 64.16 east longitude, and the study focused on the change in the distribution of groundwater between 1993-2010 and had a total impact of 30.89 inches (78.46 cm), resulting in an annual shift of 1.71 inches (4.34 cm).

Seo, who led the research, told Anadolu that the change mentioned in the study is not primarily related to geographic poles but rather to the movement known as “polar motion” according to the rotation axis of the Earth’s crust.

“We call this ‘polar motion’ of the Earth, and it is a natural phenomenon. It already has an average annual shift of about 32.8 feet (10 meters). In this study, we demonstrated how much the 32.8 feet of normal movement is increased by human influence. Many factors can affect polar movement, but the most prominent ones are the pressure created by the atmosphere and oceans,” said Seo.

Seo added that anything that changes the mass distribution on Earth can affect polar movement.

“Until we conducted this study, the impact of groundwater was overlooked. However, excessive groundwater depletion is significant enough to alter polar movements. When we extract and use groundwater, a portion of it rises to the atmosphere through evaporation while another part mixes with the oceans, redistributing mass. This affects the balance. This is what is referred to as polar motion,” he said.

He noted that this movement is a relatively small change and does not significantly impact climate change.

“We are talking about almost a 3.2-feet (1 meter) change within 20 years, which is a minimal effect. Imagine sliding a little further from where you are sitting; it won’t change your position,” he added.

Seo highlighted that the decline in water resources caused by climate change has led to increased reliance on groundwater extraction, indirectly affecting polar movements.

He evaluated the impacts of these shifts in polar movements on GPS systems, satellites and terrestrial observation stations.

“Those working in these fields already know that there is an average annual change of 32.8 feet. The International Earth Rotation and Reference Systems Service (IERS) studies this matter and redefines the coordinates every five to 10 years. People are aware of this and understand the situation,” he said.

*Writing by Esra Tekin in Istanbul