Tim Newcomb
POP MECH
Fri, July 14, 2023
Henrik Sorensen - Getty Images
Researchers think they’ve found the reason for the most significant drop in Earth’s gravity, known as the Indian Ocean geoid low.
In this location in the Indian Ocean south of Sri Lanka, our planet’s gravity is at its weakest.
A new study says mantle movement that was part of the ghost ocean Tethys attributes to this anomaly.
We might be able to blame a ghost ocean for one of the wildest gravitational anomalies on Earth.
The existence of the deepest gravitational dip on our planet, known as the Indian Ocean geoid low (IOGL), has long puzzled scientists. For context, the “geiod” is a model that shows what the surface of the Earth would look like if the only influences were gravity and rotation—no land, no wind, nothing else that could disturb the surface. If the Earth were a uniform sphere, that geoid would be even, smooth, and largely uninteresting.
But the Earth isn’t a uniform sphere, and the geoid shows all the ways in which it can vary gravitationally. Areas of lower-than-average mass density, and therefore lower gravity, show up as dents in the geoid, whereas areas of higher-than-average mass density and higher gravity show up as peaks. These peaks and dents, known collectively as gravitational anomalies, indicate regions of particular strength and weakness in Earth’s gravitational field.
In a new study published in Geophysical Research Letters, a team of researchers ran dozens of computer simulations on the origin of the Indian Ocean geoid low, which spans 8 million square miles and is located south of Sri Lanka. Researchers now believe that this “elusive feature” is, in part, the result of some undersea movements that happened pre-Indian Ocean.
“Assimilating plate motion in global mantle convection models from the Mesozoic till the present day,” the authors write, “we attempt to trace the formation of this geoid low. We show that flow induced by downwelling Tethys slabs perturbs the African Large Low Shear Velocity province and gives rise to plumes that reach the upper mantle.”
Attreyee Ghosh, an assistant professor at the Indian Institute of Science and one of the authors on the study, says in a news release that, while there have been previous studies focused on this anomaly, most attributed it to a remnant of an earlier plate that dived beneath another plate and into Earth’s mantle beneath millions of years ago, none of them have provided what she would deem a sufficient explanation for the anomaly.
Ghosh and her team were not satisfied with that lack of explanation, and attempted to with their study to fill in the blanks. Over the course of their research, the scientists discovered that the gravity low could be attributed to the presence of lighter materials in the upper- to mid-mantel below the IOGL. This can be attributed to mantle plumes—caused by the rising of abnormally hot rock—and the team discovered there was hot material coming from the nearby African large low-shear-velocity providence, known as the African superplume.
“A geoid low or negative geoid anomaly would be caused by a mass deficit within the deep mantle,” Ghosh says. “Our study explains this low with hotter, lighter material stretching from a depth of 300 kilometers up to around 900 kilometers in the northern Indian Ocean, most likely stemming from the African superplume.”
Also known as the African blob, this geological feature that helped form the IOGL likely came from oceanic slabs from the Tethys Ocean, a “ghost ocean” that was possibly in place before India shifted and helped form the Indian Ocean.
Though the researchers say that the lower mantle slabs from the Tethys Ocean likely contributes less to the formation of the IOGL than the plumes, the team also call them “necessary” for the generation of this geoid low. So, apparently, combining plumes with a unique region of mantle structure makes the perfect recipe for the formation of a negative geoid anomaly.
Fri, July 14, 2023
Henrik Sorensen - Getty Images
Researchers think they’ve found the reason for the most significant drop in Earth’s gravity, known as the Indian Ocean geoid low.
In this location in the Indian Ocean south of Sri Lanka, our planet’s gravity is at its weakest.
A new study says mantle movement that was part of the ghost ocean Tethys attributes to this anomaly.
We might be able to blame a ghost ocean for one of the wildest gravitational anomalies on Earth.
The existence of the deepest gravitational dip on our planet, known as the Indian Ocean geoid low (IOGL), has long puzzled scientists. For context, the “geiod” is a model that shows what the surface of the Earth would look like if the only influences were gravity and rotation—no land, no wind, nothing else that could disturb the surface. If the Earth were a uniform sphere, that geoid would be even, smooth, and largely uninteresting.
But the Earth isn’t a uniform sphere, and the geoid shows all the ways in which it can vary gravitationally. Areas of lower-than-average mass density, and therefore lower gravity, show up as dents in the geoid, whereas areas of higher-than-average mass density and higher gravity show up as peaks. These peaks and dents, known collectively as gravitational anomalies, indicate regions of particular strength and weakness in Earth’s gravitational field.
In a new study published in Geophysical Research Letters, a team of researchers ran dozens of computer simulations on the origin of the Indian Ocean geoid low, which spans 8 million square miles and is located south of Sri Lanka. Researchers now believe that this “elusive feature” is, in part, the result of some undersea movements that happened pre-Indian Ocean.
“Assimilating plate motion in global mantle convection models from the Mesozoic till the present day,” the authors write, “we attempt to trace the formation of this geoid low. We show that flow induced by downwelling Tethys slabs perturbs the African Large Low Shear Velocity province and gives rise to plumes that reach the upper mantle.”
Attreyee Ghosh, an assistant professor at the Indian Institute of Science and one of the authors on the study, says in a news release that, while there have been previous studies focused on this anomaly, most attributed it to a remnant of an earlier plate that dived beneath another plate and into Earth’s mantle beneath millions of years ago, none of them have provided what she would deem a sufficient explanation for the anomaly.
Ghosh and her team were not satisfied with that lack of explanation, and attempted to with their study to fill in the blanks. Over the course of their research, the scientists discovered that the gravity low could be attributed to the presence of lighter materials in the upper- to mid-mantel below the IOGL. This can be attributed to mantle plumes—caused by the rising of abnormally hot rock—and the team discovered there was hot material coming from the nearby African large low-shear-velocity providence, known as the African superplume.
“A geoid low or negative geoid anomaly would be caused by a mass deficit within the deep mantle,” Ghosh says. “Our study explains this low with hotter, lighter material stretching from a depth of 300 kilometers up to around 900 kilometers in the northern Indian Ocean, most likely stemming from the African superplume.”
Also known as the African blob, this geological feature that helped form the IOGL likely came from oceanic slabs from the Tethys Ocean, a “ghost ocean” that was possibly in place before India shifted and helped form the Indian Ocean.
Though the researchers say that the lower mantle slabs from the Tethys Ocean likely contributes less to the formation of the IOGL than the plumes, the team also call them “necessary” for the generation of this geoid low. So, apparently, combining plumes with a unique region of mantle structure makes the perfect recipe for the formation of a negative geoid anomaly.
Earth Has Tilted 31.5 Inches. That Shouldn't Happen.
Tim Newcomb
Tim Newcomb
POP MECH
Thu, July 13, 2023
Earth Has Tilted 31.5 Inches. That's Alarming.
Thu, July 13, 2023
Earth Has Tilted 31.5 Inches. That's Alarming.
PM Images - Getty Images
Humans pumping groundwater has a substantial impact on the tilt of Earth’s rotation.
Additionally, a new study documents just how much of an influence groundwater pumping has on climate change.
Understanding this relatively recent data may provide a better understanding of how to help stave off sea-level rise.
Water has power. So much power, in fact, that pumping Earth’s groundwater can change the planet’s tilt and rotation. It can also impact sea-level rise and other consequences of climate change.
Pumping groundwater appears to have a greater consequence than ever previously thought. But now—thanks to a new study published in the journal Geophysical Research Letters—we can see that, in less than two decades, Earth has tilted 31.5 inches as a result of pumping groundwater. This equates to.24 inches of sea level rise.
“Earth’s rotational pole actually changes a lot,” Ki-Weon Seo, a geophysicist at Seoul National University and study lead, says in a statement. “Our study shows that among climate-related causes, the redistribution of groundwater actually has the largest impact on the drift of the rotational pole.”
With the Earth moving on a rotational pole, the distribution of water on the planet impacts distribution of mass. “Like adding a tiny bit of weight to a spinning top,” authors say, “the Earth spins a little differently as water is moved around.”
Thanks to a study from NASA published in 2016, we were alerted to the fact that the distribution of water can change the Earth’s rotation. This new study attempted to add some hard figures to that realization. “I’m very glad to find the unexplained cause of the rotation pole drift,” Seo says. “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.”
The study included data from 1993 through 2010, and showed that the pumping of as much as 2,150 gigatons of groundwater has caused a change in the Earth’s tilt of roughly 31.5 inches, thanks to. The pumping is largely for irrigation and human use, with the groundwater eventually relocating to the oceans.
In the study, researchers modeled observed changes in the drift of Earth’s rotational pole and the movement of water. Across varying scenarios, the only model that matched the drift was one that included 2,150 gigatons of groundwater distribution.
Surendra Adhikari, a research scientist at NASA’s Jet Propulsion Laboratory who was involved in the 2016 study, says the additional research is important. “They’ve quantified the role of groundwater pumping on polar motion,” he says in a news release, “and it’s pretty significant.”
Where the water moves from—and to—matters. Redistributing water from the midlatitudes makes the biggest difference, so our intense water movement from both western North America and northwestern India have played a key role in the tilt changes.
Now that the impact of water movement is known for such a short–and relatively recent—time, digging through historical data may help show trends and provide greater depth to the understanding of groundwater movement effects.
“Observing changes in Earth’s rotational pole is useful,” Seo says, “for understanding continent-scale water storage variations.”
This data may also help conservationists understand how to work toward staving off continued sea level rise and other climate issues. Hopefully, changes can be properly implemented over time.
Humans pumping groundwater has a substantial impact on the tilt of Earth’s rotation.
Additionally, a new study documents just how much of an influence groundwater pumping has on climate change.
Understanding this relatively recent data may provide a better understanding of how to help stave off sea-level rise.
Water has power. So much power, in fact, that pumping Earth’s groundwater can change the planet’s tilt and rotation. It can also impact sea-level rise and other consequences of climate change.
Pumping groundwater appears to have a greater consequence than ever previously thought. But now—thanks to a new study published in the journal Geophysical Research Letters—we can see that, in less than two decades, Earth has tilted 31.5 inches as a result of pumping groundwater. This equates to.24 inches of sea level rise.
“Earth’s rotational pole actually changes a lot,” Ki-Weon Seo, a geophysicist at Seoul National University and study lead, says in a statement. “Our study shows that among climate-related causes, the redistribution of groundwater actually has the largest impact on the drift of the rotational pole.”
With the Earth moving on a rotational pole, the distribution of water on the planet impacts distribution of mass. “Like adding a tiny bit of weight to a spinning top,” authors say, “the Earth spins a little differently as water is moved around.”
Thanks to a study from NASA published in 2016, we were alerted to the fact that the distribution of water can change the Earth’s rotation. This new study attempted to add some hard figures to that realization. “I’m very glad to find the unexplained cause of the rotation pole drift,” Seo says. “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.”
The study included data from 1993 through 2010, and showed that the pumping of as much as 2,150 gigatons of groundwater has caused a change in the Earth’s tilt of roughly 31.5 inches, thanks to. The pumping is largely for irrigation and human use, with the groundwater eventually relocating to the oceans.
In the study, researchers modeled observed changes in the drift of Earth’s rotational pole and the movement of water. Across varying scenarios, the only model that matched the drift was one that included 2,150 gigatons of groundwater distribution.
Surendra Adhikari, a research scientist at NASA’s Jet Propulsion Laboratory who was involved in the 2016 study, says the additional research is important. “They’ve quantified the role of groundwater pumping on polar motion,” he says in a news release, “and it’s pretty significant.”
Where the water moves from—and to—matters. Redistributing water from the midlatitudes makes the biggest difference, so our intense water movement from both western North America and northwestern India have played a key role in the tilt changes.
Now that the impact of water movement is known for such a short–and relatively recent—time, digging through historical data may help show trends and provide greater depth to the understanding of groundwater movement effects.
“Observing changes in Earth’s rotational pole is useful,” Seo says, “for understanding continent-scale water storage variations.”
This data may also help conservationists understand how to work toward staving off continued sea level rise and other climate issues. Hopefully, changes can be properly implemented over time.
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