Humans’ unquenchable thirst for groundwater has sucked so much water out of the reserves that it’s affecting the Earth’s tilt, according to a new study.
Groundwater provides fresh water for people and livestock, and helps irrigate crops when rainfall is scarce.
However, new research shows that persistent groundwater extraction for more than a decade has shifted the axis on which our planet rotates, tilting it eastward at a rate of about 4.3 centimeters per year.
This change is observable even on Earth’s surface as it contributes to global sea level rise, the researchers reported in the study published June 15 in the journal Geophysical Research Letters.
“Earth’s rotational pole actually shifts a lot,” said study lead author Ki-Weon Seo, a professor in the department of Earth science education at Seoul National University in South Korea, in a press release.
“Our study shows that among climate-related causes, groundwater redistribution actually has the greatest impact on rotational pole drift.”
Earth’s Drift Axis
You may not be able to feel the Earth’s rotation, but it is rotating on a north-south axis at a rate of about 1,609 kilometers per hour.
The ebb and flow of seasonal change is linked to the angle of the planet’s axis of rotation, and over geological time, an errant axis can affect climate on a global scale, said Surendra Adhikari, research scientist at NASA’s Jet Propulsion Laboratory. , in the statement.
The Earth’s interior is covered by rocks and magma surrounding a dense, hot core. But in the outermost rock layer there are also large amounts of water.
Beneath the planet’s surface, rocky reservoirs known as aquifers are estimated to hold more than 1,000 times more water than all of the world’s surface rivers and lakes.
Between 1993 and 2010, the period examined in the study, humans extracted more than 2,150 gigatons of groundwater from the Earth’s interior, mainly in western North America and northwest India, according to estimates published in 2010.
To put that in perspective, if that amount were spilled into the ocean, it would raise global sea levels by about 6 millimeters.
In 2016, another team of researchers found that the drift in Earth’s axis of rotation between 2003 and 2015 could be linked to changes in the mass of glaciers and ice sheets, as well as the planet’s terrestrial liquid water reserves.
In fact, any mass change on Earth, including atmospheric pressure, can affect its axis of rotation, Seo told the CNN in an email.
But axis shifts caused by atmospheric pressure changes are periodic, meaning the rotational pole wanders and then returns to its previous position, explained Seo.
Seo and his colleagues had questions about long-term changes in the axis – specifically, how groundwater contributed to this phenomenon. It had not been calculated in previous surveys.
The impact of groundwater extraction
Changes in the Earth’s axis are measured indirectly through radio telescope observations of motionless objects in space — quasars — using them as fixed reference points.
For the new study, the scientists took 2010 data on groundwater extraction and incorporated them into computer models, along with observational data on surface ice loss and sea level rise and estimates of rotational pole shifts.
The researchers then evaluated sea level variations “using the model’s groundwater mass change,” to identify how much of the axis shift was caused by groundwater pumping alone, Seo said.
Redistribution of groundwater has tilted Earth’s rotational axis eastward by more than 78.7 centimeters in just under two decades, according to the models.
The most notable driver of long-term variations in the rotational axis was already known as mantle flow – the movement of molten rock in the layer between the Earth’s crust and the outer core.
The new modeling reveals that groundwater extraction is the second most significant factor, Seo said.
“This is a good contribution and important documentation,” said Adhikari. “They’ve quantified the role of groundwater pumping in polar motion, and it’s quite significant.”
Future models could use observations of Earth’s rotation to illuminate the past, Seo added.
“The data has been available since the end of the 19th century,” he said.
With this information, scientists can go back in time and track changes in planetary systems as the climate warms over the last 100 years.
Groundwater pumping can be a lifeline, especially in parts of the world that are heavily affected by drought caused by climate change.
But underground reserves of liquid water are finite; once drained they are slow to replenish.
And groundwater extraction doesn’t just deplete a valuable resource; the new findings demonstrate that this activity has unintended global consequences.
“We affect Earth’s systems in many ways,” said Seo. “People need to be aware of this.”
Source: CNN Brasil
Bruce Belcher is a seasoned author with over 5 years of experience in world news. He writes for online news websites and provides in-depth analysis on the world stock market. Bruce is known for his insightful perspectives and commitment to keeping the public informed.
