A peer-reviewed study published in Scientific Reports has reconstructed the evolution of the Antarctic Geoid Low, the strongest negative gravity anomaly on Earth, over approximately 70 million years, finding that its amplitude and position have shifted significantly across geologic time due to active mantle dynamics beneath the continent. The research adds new detail to a feature that has puzzled geophysicists for decades: a region where Earth’s gravitational pull is measurably weaker than the global average, centered beneath the ice of East Antarctica. Combined with satellite gravity measurements showing ongoing non-linear mass changes across the continent through early 2025, the findings are sharpening scientific focus on what drives this anomaly and whether its behavior carries consequences for ice-sheet stability.
Tracing 70 Million Years of Mantle Shifts
The Antarctic Geoid Low, or AGL, represents a zone where the geoid, an imaginary surface of equal gravitational potential, dips well below its expected level. A study in Scientific Reports traces the time-dependent evolution of this anomaly across roughly 70 million years of Earth history, linking changes in its amplitude and geographic position to convection patterns deep in the mantle. Rather than treating the AGL as a static relic, the research models it as a dynamic feature shaped by the slow churning of material hundreds of kilometers below the surface. The paper explicitly describes a “giant gravity/geoid anomaly over Antarctica,” framing it as the planet’s most pronounced depression in gravitational strength.
What makes this reconstruction significant is its timescale. Most gravity studies rely on satellite data spanning a few decades at most. By extending the analysis back through the Cenozoic era, the researchers show that the AGL has not simply persisted but has evolved, with its depth and center migrating as tectonic plates shifted and mantle plumes reorganized. This long view challenges a common assumption that large-scale gravity anomalies are geologically inert. If the mantle dynamics responsible for the AGL are still active, they could influence how mass is distributed beneath the Antarctic ice sheet in ways that shorter-term satellite records alone cannot capture. In turn, that has implications for how scientists interpret present-day gravity signals, which blend contributions from deep Earth processes and near-surface ice changes.
A 500-Kilometer Basin Hidden Under Ice
Layered on top of the broader AGL is a more localized and equally striking feature in Wilkes Land, a region of East Antarctica. A NASA technical report describes a prominent positive free-air gravity anomaly centered near 70 degrees south latitude and 120 degrees east longitude, sitting above depressed subglacial topography. The feature was interpreted as a possible mascon, a mass concentration similar to those found beneath large lunar impact craters. Separate peer-reviewed work confirmed the anomaly as a circular structure roughly 500 km in diameter, with a gravity-to-topography relationship consistent with an ancient impact basin that has since been buried under ice and modified by geological processes.
Independent geophysical evidence strengthens the case. An analysis integrating satellite magnetic data from the Magsat, Orsted, and CHAMP missions with GRACE gravity and subglacial terrain measurements found a major crustal magnetic anomaly in the same area, consistent with crustal thinning or modification from a massive impact. Ohio State University researchers first brought the Wilkes Land mass concentration to wide public attention in 2006, when NASA’s Earth Observatory highlighted GRACE satellite detections of the feature, which spans hundreds of kilometers. The GRACE system measures gravity variations through precise inter-satellite ranging, detecting subtle differences in mass distribution beneath the ice that ground-based instruments cannot reach, and thereby revealing hidden basins and structural anomalies.
Satellite Records Show Non-Linear Mass Changes
The static picture of buried craters and ancient mantle plumes gains urgency when placed alongside modern satellite gravity records. A recent synthesis of Antarctic mass change using GRACE and GRACE-FO data through January 2025 documents non-linear variability in ice-mass balance at the basin level across the continent. This means that ice loss and gain do not follow smooth, monotonic trends but instead fluctuate in response to changing atmospheric circulation, ocean heat content, and internal ice dynamics. For a region like Wilkes Land, where a deep subglacial basin already creates unusual gravitational conditions, these non-linear shifts raise questions about feedback loops between ice flow, bedrock geometry, and the underlying lithosphere and mantle.
The practical concern is direct. If ice loss accelerates over a subglacial basin where the bedrock is already depressed well below sea level, warm ocean water can intrude farther inland, destabilizing glaciers from below and potentially triggering marine ice-sheet instability. Time-variable gravity measurements are the primary tool for tracking these changes at continental scale, but interpreting the signal requires disentangling ice-mass shifts from deeper geological contributions. The 70-million-year reconstruction of the AGL offers a baseline against which scientists can measure whether recent changes in the gravity field reflect ice dynamics alone or also involve ongoing adjustments in the mantle. Without that baseline, attributing cause to the satellite-era signal is significantly harder, and projections of future sea-level rise remain more uncertain.
Reassessing the Wilkes Land Signal
As gravity and topography models have improved, so has the ability to evaluate whether the Wilkes Land structure is as clear-cut as early studies suggested. A peer-reviewed reassessment using updated gravito-topographic models, including SatGravRET 2014 and Bedmap 2, evaluated the detectability and geometry of the proposed impact basin. The study found that improved data affect both the strength and clarity of the gravitational signal, meaning earlier estimates of the structure’s size, depth, and degree of circularity may need revision as measurement precision increases. In some reconstructions, the signal appears more diffuse than initially reported, which opens the door to alternative geological interpretations beyond a single large impact.
This matters because the scientific debate over the Wilkes Land feature is far from settled. Some researchers view the gravity and magnetic evidence as strongly consistent with a mega-impact origin, while others argue that tectonic processes, rift-related magmatism, or variations in crustal thickness could produce similar signatures. The ongoing refinement of models through programs highlighted in NASA technical updates underscores how sensitive interpretations are to the underlying datasets and processing choices. As new satellite missions and airborne surveys add higher-resolution measurements, scientists will be able to test whether the Wilkes Land anomaly resolves into a sharply bounded basin or remains a more ambiguous mass concentration that defies a simple impact narrative.
What the Antarctic Geoid Low Means for Future Research
Taken together, the long-term reconstruction of the Antarctic Geoid Low, the enigmatic Wilkes Land structure, and the non-linear satellite record of ice-mass change point to a continent where deep Earth processes and surface climate are tightly intertwined. The AGL demonstrates that even the largest-scale gravity anomalies evolve over tens of millions of years, while Wilkes Land shows how localized structures can superimpose additional complexity on top of that background. For glaciologists and climate modelers, this means that projections of Antarctica’s future contribution to sea-level rise must account not only for atmospheric and oceanic forcing but also for how ice sheets respond to the three-dimensional shape and rheology of the solid Earth beneath them.
Future work is likely to focus on integrating mantle convection models, high-resolution crustal maps, and time-variable gravity data into unified frameworks that can simulate both slow geoid evolution and rapid ice-sheet change. Such efforts will depend on continued access to satellite observations and on open dissemination of technical analyses through channels like NASA information services, which help researchers coordinate datasets and methods across institutions. As these lines of evidence converge, scientists hope to determine whether features like the Wilkes Land anomaly primarily record ancient cataclysms, ongoing tectonics, or some combination of both, and, crucially, how those deep structures might shape the stability of Antarctica’s ice in a warming world.
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*This article was researched with the help of AI, with human editors creating the final content.
