The origins of Antarctica’s ‘gravity hole’ may have finally been revealed, after researchers probed beneath the ice to trace the anomaly’s formation over millions of years of geological history.
Earth’s gravity is not as steady and even as it may feel to us, with variations in strength across the planet. In a recent paper published in Scientific Reports, international researchers finally identified how a spot below Antarctica came to have the weakest gravity on Earth, after considering the planet’s rotation.
Antarctic Gravity
Earth’s gravity variations result from differences in rock density in the mantle, far below the surface. These differences are subtle and not readily noticeable by humans.
“From the gravity reduction, a 90 kg man would ‘weigh’ about 5–6 grams less in this region,” co-author Dr. Alessandro Forte told The Debrief.
The researcher’s work demonstrated that the gravity hole formed through long-term geological processes, as slow-moving rock shifted over tens of millions of years. Their analysis also concluded that Antarctica’s gravity changes over time correlated with shifting climate patterns in the region. They suggest that further research may illuminate whether gravity changes could account for Antarctica’s ice sheet growth, which acts as a natural climate record.
“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,” Dr. Forte said.
Gravity and Antarctica’s Sea Level
These gravity variations can have major effects on the world’s oceans. The power of gravity drives the flow of water, pulling water towards a stronger source. This results in lower water levels relative to the Earth’s center in areas of weaker gravity, and for that reason, Antarctica’s sea surface is lower than it would be if the region experienced normal gravity.
Based on this, the research team set out to better understand the strange gravity fluctuation under the Antarctic and its impact on sea level.
“We want to model the dynamics of the Earth under Antarctica and the impacts on the elevation and sea level around this continent,” Dr. Forte explained. “The results presented in this new study are the first step toward that mapping of sea level change, at the time the massive ice complex in Antarctica began to grow between 35 and 30 million years ago.”
For their research, the team used data from a long-standing collaboration between Alessandro Forte’s group at the University of Florida and a team of seismologists at the University of Texas at Austin, including researchers Nathan Simmons and Steve Grand. That collaboration produced three-dimensional maps of the Earth’s interior structures through analyzing earthquake waves.
“The mantle rocks that are mainly contributing to this very large ‘gravity low’ are (long-lived, sinking) cold dense rocks deeper than ~2000 km depth and an increasing upper-mantle contribution, above ~1300 km depth, during the last ~40 million years, associated with a broad, buoyant upwelling rising toward shallower mantle,” Dr. Forte said.
Continuing to Investigate the Antarctic
“Our principal focus going forward is to model and quantify the implications for relative sea level through time,” Dr. Forte explained. “Gravity/geoid changes can shift where the ocean ‘wants’ to sit (in a purely gravitational sense).”
To better understand this phenomenon, Dr. Forte suggests combining the team’s time-dependent sea surface data with modeled changes in continental elevation, then comparing the results with real-world geological observations.
“One major—outstanding—challenge is to obtain reliable maps of the thickness of the outer crust of our planet,” Dr. Forte added. “This crust sits atop the mantle below. There are many gaps in our knowledge of the thickness and mass density of this outermost rocky layer on our planet, despite its critical role in understanding the evolution of our planet.”
While some regions, like North America, are relatively well-investigated in this regard, the southern hemisphere’s mantle remains poorly explored. The team hopes that filling that information gap will provide crucial new insights into the Antarctic and what we can expect from global climate change.
The paper, “Cenozoic Evolution of Earth’s Strongest Geoid Low Illuminates Mantle Dynamics Beneath Antarctica,” appeared in Scientific Reports on December 19, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.