According to a new study, humans have extracted so much water from underground that the Earth’s axis of rotation has shifted approximately 80 cm eastward in just 20 years.
Researchers studying the shift in the geographical pole of the Earth argue that such a change would not be possible without the influence of groundwater.
The Earth’s axis of rotation, around which the planet spins, is not a fixed and static structure. It wobbles and drifts as it rotates on an imaginary line passing through the North and South Poles, known as the rotational axis.
According to a recent study, the movement of the Earth’s axis is referred to as polar motion. It is known that the North Pole draws a circle with a width of 10 meters each year.
In the 20th century, the National Aeronautics and Space Administration (NASA) determined that the Earth’s axis of rotation shifted by 4 cm per year.
Recent research has found that climate change is causing the shift in the Earth’s rotation. However, the exact impact of groundwater on this shift has not been fully determined.
Professor Ki-Weon Seo, the lead author of the study and a researcher at Seoul National University’s Department of Earth Sciences, emphasized, “In the history of the Earth, significant changes have occurred in the Earth’s axis of rotation. However, our study highlights the importance of groundwater depletion in causing the shift of the Earth’s axis.”
Global climate models have found that the depletion of groundwater contributes to the rise in sea levels. Between 1993 and 2010, approximately 2 trillion tons of water were extracted from underground sources.
Most of this water, used for drinking and agricultural irrigation purposes, is eventually discharged into the sea. This means that a considerable mass of water is being moved from its original location due to human intervention.
Previous estimates suggested that this displacement raised sea levels by approximately 6 mm. A new study published in the scientific journal Geophysical Research Letters, focusing on the change in the Earth’s rotation pole, confirms this estimate.
The distribution of water on the Earth’s surface alters the distribution of mass. Researchers liken this to adding a small weight to a spinning top. They explain that when the location of the water mass on Earth changes, it causes a slight modification in the rotational motion.
To understand this change, researchers tested the observed shift in the Earth’s rotation axis using computer models.
When only the melting of ice and glaciers were taken into account, a gap of 78.5 cm was observed in the current shift. The study linked this gap to groundwater depletion.
Prof. Seo states, “We found that groundwater consumption shifts the Earth’s pole eastward at a rate of 4.36 cm per year at 64 degrees. This trend will continue.”
Expressing his happiness for finding the previously unexplained cause of polar motion, Prof. Seo, as someone living on Earth and a father, also expresses concern and surprise about the additional consequence of groundwater depletion contributing to rising sea levels.
Surendra Adhikari, a scientist at NASA’s Jet Propulsion Laboratory, mentioned in a statement to the American Geophysical Union that the Earth’s rotation axis changes by a few meters annually and that groundwater depletion does not pose a risk of changing seasons.
Adhikari notes that recent research has shown that the loss of ice mass in Greenland is one of the primary causes of the shift in the rotational axis.
However, Adhikari mentions that in geological timescales, the shift in the pole can have implications for climate change.