Study: Pumping Groundwater Has Changed How Earth Turns
2023-07-03
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1A recent study says that pumping massive amounts of groundwater to the surface can affect the position of Earth's poles.
2The poles are at either end of the imaginary line running through the Earth.
3The turning motion of Earth around this line causes day and night.
4The tilt of the line, in relation to the sun, causes the seasons.
5Scientists have known for more than 100 years that the Earth's poles change position a little over time with what is called polar motion.
6A group of international scientists recently published their study of polar motion.
7Earlier studies linked the way water is spread out over the Earth to polar motion.
8The scientists wanted to see if the movement of groundwater could help explain differences between observed and predicted polar motion.
9The researchers used a climate computer model to estimate that humans pumped a total of 2,150 gigatons of groundwater to the Earth's surface from 1993 to 2010.
10One gigaton is equal to about 1 billion metric tons, the American space agency NASA notes.
11The model estimated that world sea levels rose six millimeters because of the additional groundwater.
12Groundwater pumped to the surface is used for crops and drinking water.
13It is an important resource to support human life.
14The recent study suggests that the movement of groundwater to the oceans can, in a way, affect Earth's rotation and might also add to sea level rise.
15A 2016 study first showed evidence that ocean water flows can affect polar motion.
16But the latest study is the first to explore in depth how groundwater brought to the surface might change Earth's tilt.
17The researchers created their climate model to study polar motion.
18Described another way, polar motion is when the position of the planet's rotational axis moves in relation to Earth's crust.
19Water movements on Earth can cause the planet to rotate "a little differently as water is moved around," the researchers said in a statement.
20Ki-Weon Seo is a geophysicist at Seoul National University who led the study.
21It recently appeared in the publication Geophysical Research Letters.
22Seo said, "Earth's rotational pole actually changes a lot."
23He added that the study shows "that among climate-related causes, the redistribution of groundwater actually has the largest impact on the drift of the rotational pole."
24The researchers depended on data collected by satellites over nearly 20 years.
25They used their computer model to estimate what kinds of water redistribution caused a notable change in the Earth's tilt.
26The team's main finding was that the Earth tilted nearly 80 centimeters towards the 64 degrees east longitude line between 1993 and 2010.
27The study notes that where the groundwater is pumped from affects how much polar motion happens.
28The biggest changes were recorded in mid-latitude areas: areas not too close to the North Pole and not too near the equator.
29During the study period, the most water was redistributed in western North America and northwestern India.
30Both of these are in mid-latitude areas.
31Seo noted that the rotational pole changes caused by groundwater are too small to affect Earth's seasons.
32He said that, in theory, making changes to slow the rate of groundwater removal could affect Earth's polar motion.
33But major changes would likely only be seen if such efforts were highly organized and continued for many years.
34"I'm very glad to find the unexplained cause of the rotation pole drift," Seo said.
35"On the other hand, as a resident of Earth and a father, I'm concerned and surprised to see that pumping groundwater is another source of sea-level rise."
36Seo noted that the latest study could mark the start of additional research into how water flow changes affected different, specific areas of the world.
37He said the same rotational pole data could be used to learn about possible causes of redistributed water over the past 100 years.
38"Were there any...changes resulting from the warming climate? Polar motion could hold the answer," he added.
39Surendra Adhikari is a research scientist at NASA's Jet Propulsion Laboratory.
40He was not involved in this study.
41In a statement, Adhikari said the research was "a nice contribution and an important documentation for sure."
42He published the 2016 paper on water redistribution's effects on rotational drift.
43Adhikari added that the study clearly demonstrates "the role of groundwater pumping on polar motion, and it's pretty significant."
44I'm Bryan Lynn.
1A recent study says that pumping massive amounts of groundwater to the surface can affect the position of Earth's poles. 2The poles are at either end of the imaginary line running through the Earth. The turning motion of Earth around this line causes day and night. The tilt of the line, in relation to the sun, causes the seasons. 3Scientists have known for more than 100 years that the Earth's poles change position a little over time with what is called polar motion. 4A group of international scientists recently published their study of polar motion. Earlier studies linked the way water is spread out over the Earth to polar motion. The scientists wanted to see if the movement of groundwater could help explain differences between observed and predicted polar motion. 5The researchers used a climate computer model to estimate that humans pumped a total of 2,150 gigatons of groundwater to the Earth's surface from 1993 to 2010. One gigaton is equal to about 1 billion metric tons, the American space agency NASA notes. The model estimated that world sea levels rose six millimeters because of the additional groundwater. 6Groundwater pumped to the surface is used for crops and drinking water. It is an important resource to support human life. The recent study suggests that the movement of groundwater to the oceans can, in a way, affect Earth's rotation and might also add to sea level rise. 7A 2016 study first showed evidence that ocean water flows can affect polar motion. But the latest study is the first to explore in depth how groundwater brought to the surface might change Earth's tilt. 8The researchers created their climate model to study polar motion. Described another way, polar motion is when the position of the planet's rotational axis moves in relation to Earth's crust. 9Water movements on Earth can cause the planet to rotate "a little differently as water is moved around," the researchers said in a statement. 10Ki-Weon Seo is a geophysicist at Seoul National University who led the study. It recently appeared in the publication Geophysical Research Letters. 11Seo said, "Earth's rotational pole actually changes a lot." He added that the study shows "that among climate-related causes, the redistribution of groundwater actually has the largest impact on the drift of the rotational pole." 12The researchers depended on data collected by satellites over nearly 20 years. They used their computer model to estimate what kinds of water redistribution caused a notable change in the Earth's tilt. The team's main finding was that the Earth tilted nearly 80 centimeters towards the 64 degrees east longitude line between 1993 and 2010. 13The study notes that where the groundwater is pumped from affects how much polar motion happens. The biggest changes were recorded in mid-latitude areas: areas not too close to the North Pole and not too near the equator. During the study period, the most water was redistributed in western North America and northwestern India. Both of these are in mid-latitude areas. 14Seo noted that the rotational pole changes caused by groundwater are too small to affect Earth's seasons. He said that, in theory, making changes to slow the rate of groundwater removal could affect Earth's polar motion. But major changes would likely only be seen if such efforts were highly organized and continued for many years. 15"I'm very glad to find the unexplained cause of the rotation pole drift," Seo said. "On the other hand, as a resident of Earth and a father, I'm concerned and surprised to see that pumping groundwater is another source of sea-level rise." 16Seo noted that the latest study could mark the start of additional research into how water flow changes affected different, specific areas of the world. He said the same rotational pole data could be used to learn about possible causes of redistributed water over the past 100 years. "Were there any...changes resulting from the warming climate? Polar motion could hold the answer," he added. 17Surendra Adhikari is a research scientist at NASA's Jet Propulsion Laboratory. He was not involved in this study. In a statement, Adhikari said the research was "a nice contribution and an important documentation for sure." 18He published the 2016 paper on water redistribution's effects on rotational drift. Adhikari added that the study clearly demonstrates "the role of groundwater pumping on polar motion, and it's pretty significant." 19I'm Bryan Lynn. 20Bryan Lynn wrote this story for VOA Learning English, based on reports from Geophysical Research Letters, the American Geophysical Union and the U.S. Geological Survey. 21______________________________________________________________ 22Words in This Story 23tilt - n. a state of having one side higher than the other; leaning to one side 24rotation - n. the act of turning around a central point 25axis -n. a line around which something turns, such as the Earth 26crust - n. the outer, solid part of the Earth 27redistribute - v. to take from one area and put in another area 28impact - n. effect 29longitude -n. the system of lines going north to south that help travelers know where they are on the Earth 30drift -n. the slow movement of something away from where it was before to a new position that is hard to predict 31contribute - v. to help cause something to happen 32role - n. the part something plays in an event or situation 33_________________________________________________________________ 34What do you think of this story? 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