Origins of ‘gravity hole’ over Antarctica finally unveiled

Researchers found that shifting gravity patterns may have encouraged the growth of Antarctica’s huge ice sheets

Scientists have finally cracked the origins of a “gravity hole” beneath the continent of Antarctica - the part of Earth where gravity is weakest.

While gravity is often understood as consistent around the world, in reality, its strength varies significantly in different areas. Weaker gravity in Antarctica has a major impact on the oceans, causing water to flow towards areas of stronger gravity and leaving the continent’s sea level lower than it otherwise would be.

Gravity is weaker in the regions where hot rock from within the Earth’s mantle rises towards the surface - over millions of years, these slow rock movements deep under the Earth’s surface have led to the so-called “gravity hole” in Antarctica.

The study, which was published in the Scientific Reports journal, looked at how the changes in Antarctica’s gravity may have caused significant changes in the region’s climate. Researchers say it has laid the ground for future research into how shifting gravity patterns could have promoted the growth of the continent’s vast ice sheets.

Antarctica has a gravity hole under its surface (Getty)

"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," said professor Alessandro Forte of the University of Florida, the co-author of the study.

Researchers mapped the Antarctic gravity hole in order to evaluate how it developed over millions of years. They combined earthquake recordings with physics-based modelling to construct a gravitational map of the planet. Scientists said the map matched the gravitational data captured by satellites, backing up the accuracy of their models.

"Imagine doing a CT scan of the whole Earth, but we don't have X-rays like we do in a medical office. We have earthquakes. Earthquake waves provide the 'light' that illuminates the interior of the planet," professor Forte said.

Researchers used a computer model to discover that the gravity hole was weaker around 70 million years ago (left) but was becoming stronger 40 million years ago (right) (Scientific Reports)

Researchers then used computer models to rewind how rocks flowed in the interior of the earth, tracking changes back as far as 70 million years - when the dinosaurs were around.

They discovered that the gravity hole had been weaker 70 million years ago, before it began gaining strength around 50 and 30 million years ago.

These timings overlapped with major changes in Antarctica’s climate system, including the emergence of huge glaciers across the continent, suggesting there may have been a causal connection.

The study was named ‘Cenozoic evolution of Earth's strongest geoid low illuminates mantle dynamics beneath Antarctica’.