Gravity feels like the one thing that never changes. But it does change a little from place to place. And after you account for Earth’s rotation, the weakest gravity on the planet sits beneath Antarctica.
Scientists sometimes call this a “gravity hole,” not because gravity disappears, but because it’s measurably lower there than you’d expect.
A new study suggests this oddity wasn’t created by anything happening at the surface. Instead, it likely formed because of extremely slow shifts in rock deep inside the Earth over tens of millions of years.
The researchers also found that the gravity low strengthened during a time window that overlaps with major climate changes in Antarctica, including the start of widespread glaciation. This raises an intriguing question about whether the two are connected.
Small gravity differences
The study emphasizes that these gravity variations are tiny in absolute terms. You wouldn’t feel them walking around. But they can matter in a sneaky way through the ocean.
Gravity helps “pull” ocean water into shape. Where gravity is slightly weaker, water tends to flow away toward areas with stronger gravity. That means the ocean surface can sit a bit lower relative to Earth’s center in weaker-gravity regions.
Around Antarctica, that effect is measurable: sea-surface height is lower than it would otherwise be because of the gravity hole.
That doesn’t automatically mean the gravity hole controls the ice sheets. But it does mean gravity is part of the background physics that influences sea level, coastal geometry, and how water is distributed around continents.
A deep-Earth explanation
The study argues that Antarctica’s gravity low is linked to differences in rock density far below the surface.
Inside the Earth, not all rock is the same. Some regions are denser, some are less dense, and these differences affect how strongly gravity pulls at the surface.
The new research was led by geophysicist Alessandro Forte from the University of Florida and Petar Glišović from the Paris Institute of Earth Physics.
The goal was to map the gravity hole and then figure out how it developed over millions of years.
“If we can better understand how Earth’s interior shapes gravity and sea levels, we gain insight into factors that may matter for the growth and stability of large ice sheets,” Forte said.
How do you “see” inside the Earth?
To get at the deep interior, the researchers relied on a global science effort that combines earthquake recordings with physics-based modeling. The basic idea is like medical imaging, but for a planet.
“Imagine doing a CT scan of the whole Earth, but we don’t have X-rays like we do in a medical office,” said Forte. “We have earthquakes. Earthquake waves provide the ‘light’ that illuminates the interior of the planet.”
As earthquake waves travel through Earth, they speed up or slow down depending on the properties of the rocks they pass through.
By collecting recordings from earthquakes around the globe, scientists can reconstruct a 3D picture of Earth’s interior structure. From that, you can estimate density differences – and from density differences, you can predict gravity patterns.
Evolution of the gravity pattern
Forte and Glišović used their earthquake-based model of Earth’s interior to predict the gravity field for the whole planet. Then, they checked it against satellite measurements – basically the “gold standard” for gravity mapping.
The reconstructed map matched closely, which gave them confidence they weren’t just building a nice-looking model that had nothing to do with reality.
Next came the ambitious part: turning the clock backward. Using sophisticated computer simulations, they “rewound” the flow of rock inside the Earth and tracked changes back around 70 million years, roughly to dinosaur times.
This let them produce snapshots of what the gravity pattern might have looked like in the past, and how it evolved over time.
The gravity hole over time
The reconstructed snapshots suggest the Antarctic gravity hole started out weaker. Then, between about 50 and 30 million years ago, it began strengthening.
That timing is what makes the result especially interesting. The 50 to 30 million-year window overlaps with major shifts in Antarctica’s climate system – including the onset of widespread glaciation, when Antarctica began transitioning toward the ice-dominated continent we know today.
The study doesn’t claim the gravity change caused the ice sheets. But the overlap suggests it’s worth asking whether deep Earth processes could have nudged surface conditions in ways that mattered for ice growth.
What kind of connection is possible?
This is the tricky part, because “gravity hole” sounds dramatic, but the mechanisms are subtle. One possible pathway is through sea level and ocean circulation.
Since gravity influences where water piles up or drains away, a change in the gravity field over geologic time could slightly reshape sea-surface height patterns around Antarctica.
Another pathway could involve how the solid Earth itself rises or sinks over long periods as mantle rock flows and continents respond.
Changes in the Earth’s interior can alter surface elevation, which in turn affects climate, ice stability, and how easily ice can expand across a continent.
That’s why Forte wants to go further and link gravity, sea level, and continental elevation changes in a single modeling framework.
Going forward, Forte hopes to test for a causal connection between this strengthening gravity hole and the ice sheets, using new modeling that links gravity, sea level, and continental elevation changes.
The climate link to Earth’s interior
Most people think of climate as an atmosphere-and-ocean story. This research is a reminder that there’s another slow-moving system in the background: the planet’s interior.
It doesn’t change day to day, but over millions of years it can reshape continents, ocean basins, and even the gravity field that helps set the stage for sea level.
“How does our climate connect to what’s going on inside our planet?” Forte asked.
The study doesn’t end with a neat, single answer. It begins with a strange fact: Antarctica’s gravity is unusually low. Scientists trace that pattern back to deep Earth motions playing out over tens of millions of years.
The finding also points to a bigger possibility – that the solid Earth and the climate system may be more connected than we usually assume.
The study was published in the journal Scientific Reports.
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