A region beneath Antarctica where Earth’s gravitational pull is measurably weaker than anywhere else on the planet has persisted for roughly 70 million years, according to new research that traces the anomaly to ancient shifts deep inside the mantle. The study, published in Scientific Reports by researchers Petar Glisovic and Alessandro Forte, reconstructs the history of what scientists call the Antarctic Geoid Low, a broad depression in the Ross Sea sector where the geoid surface dips well below the global average. The finding connects this “gravity hole” to buried remnants of tectonic plates and slow-rising plumes of hot rock, offering a rare window into how processes thousands of kilometers below the surface shape the planet we stand on.
Scientists at the University of Florida, working with collaborators in Canada and Europe, describe the feature as the deepest known long-wavelength geoid minimum on Earth, centered off the coast of Marie Byrd Land and extending beneath the Ross Ice Shelf. In a university release on the discovery, the team emphasizes that this low is not a void but a subtle deficit in mass distribution relative to surrounding regions, detectable only with precise satellite measurements and advanced modeling. Their reconstruction shows the anomaly emerging in tandem with tectonic reorganizations around the southern Pacific and then persisting as mantle structures beneath Antarctica slowly evolved.
What the Antarctic Geoid Low Actually Is
Earth is not a perfect sphere, and its gravity field is not uniform. Satellites measure these variations by tracking tiny changes in their own orbits, and the data reveal that certain regions pull slightly less than others. The most extreme such region sits beneath the Ross Sea sector of Antarctica, where the nonhydrostatic geoid, a mathematical surface representing equal gravitational potential, sags dramatically. The Scientific Reports analysis frames this feature as a long-wavelength depression that has endured for approximately 70 million years, spanning most of the Cenozoic era and surviving continental drift, ice sheet growth, and repeated climate shifts.
For readers unfamiliar with gravity mapping, the effect is real but subtle. No one standing on Antarctic ice would feel lighter, and a bathroom scale would not register a noticeable change. Instead, the anomaly shows up in precise satellite measurements as a region where mass is distributed differently at depth. Modern gravity models rely on spherical harmonic fields, mathematical coefficients that act as building blocks for mapping the global gravity signal. These coefficients, derived from missions like GRACE and its successor GRACE-FO, allow scientists to pinpoint where mass concentrations are stronger or weaker relative to a reference ellipsoid. The Antarctic Geoid Low stands out as the single deepest depression in that global picture, rivaling long-recognized geoid lows in the Indian and Pacific oceans but dipping even farther below the reference surface.
Rewinding the Mantle Clock
The central technical achievement of the new study is its use of time-reversed mantle convection modeling to trace the geoid low backward through geological time. Glisovic and Forte built on a data-assimilation scheme they previously developed for reconstructing three-dimensional mantle structure. The approach starts with present-day mantle images captured by seismic tomography, which maps variations in rock density and temperature using earthquake waves, and then runs the convection equations in reverse while nudging the model to stay consistent with observations. The result is a series of snapshots showing how material moved inside the mantle over tens of millions of years and how those flows sculpted Earth’s long-wavelength gravity field.
This technique rests on established mathematical foundations. An earlier peer-reviewed paper in Geophysical Journal International laid out a quasi-reversibility framework for assimilating observational constraints into mantle dynamics models, stabilizing what would otherwise be an ill-posed problem when run backward in time. By combining that framework with high-resolution tomographic images and plate reconstructions, the researchers could test whether the gravity low beneath Antarctica appeared suddenly or evolved gradually. Their models consistently showed the feature persisting through the Cenozoic, which rules out explanations that treat it as a short-lived artifact of recent tectonic activity or ice-sheet loading and instead points to deep, slowly changing structures in the lower mantle.
Slab Graveyards and Rising Plumes
Why would a gravity deficit endure for 70 million years? The answer, according to the modeling, involves structures deep in the lower mantle that are remarkably stable. When tectonic plates subduct, they sink through the mantle and eventually pile up near the core-mantle boundary, forming dense “slab graveyards.” These accumulations displace hotter, more buoyant material, triggering broad upwellings of rock that rise toward mid-mantle depths. Earlier work in mantle geodynamics linked long-wavelength geoid lows to this kind of coupled pattern: dense slabs that locally increase gravity and adjacent upwellings that decrease it, together producing broad undulations in Earth’s gravity field.
The new research extends that interpretation specifically to Antarctica. The models suggest that ancient subducted slabs beneath the southern hemisphere created a pattern of lower-mantle upwelling that reduced local mass concentration under the Ross Sea sector, carving out a persistent depression in the geoid. Because these deep structures move slowly, on the order of centimeters per year, the resulting gravity low has been self-reinforcing over geological time, migrating only modestly as mantle flow reorganized. This challenges older views that geoid lows are transient features tied directly to active subduction zones. Instead, the Antarctic case points to a feedback loop: slab remnants generate upwellings, those upwellings sustain the gravity deficit long after the original subduction has ceased, and the combined pattern leaves a lasting fingerprint on the global gravity field.
How Satellites Measure a Hidden Signal
The observational backbone for this work comes from the GRACE satellite mission, which operated from 2002 to 2017, and from related gravity products derived at NASA centers. GRACE measured gravity by tracking the distance between twin satellites flying in formation; as they passed over regions of varying mass, one satellite would speed up or slow down relative to the other, and those tiny shifts were converted into maps of Earth’s gravity field. For many geophysical applications, gravity information from these missions is expressed as mascon solutions, or mass concentration blocks, which are fitted on an ellipsoidal Earth model and incorporate regularization to reduce noise from atmospheric and oceanic variability.
The Antarctic study focuses on long-wavelength components of the gravity field, which are less sensitive to short-term mass changes at the surface and more reflective of deep mantle structure. One gap in the current research is the absence of updated GRACE-FO Level-2 fields specifically applied to the Antarctic Geoid Low; the authors instead rely on earlier GRACE-era solutions and static gravity models that synthesize multiple data sets. The latest GRACE-FO products could refine the modern baseline against which the 70-million-year reconstruction is calibrated, particularly by improving estimates of present-day polar mass redistribution and its subtle imprint on the low-degree gravity field.
Implications for Antarctica’s Past and Future
Although the gravity anomaly itself has negligible direct impact on life at the surface, its existence carries important implications for how scientists interpret Antarctica’s geological and climatic history. The University of Florida release on this work notes that a long-lived geoid low can influence how ice sheets and oceans respond to loading and unloading, because the geoid partly governs sea-surface height and the way water redistributes around large ice masses. Over tens of millions of years, a persistent depression in the geoid beneath West Antarctica may have slightly altered regional sea levels and the buoyancy forces acting on the ice sheet, subtly shaping the evolution of the Ross Sea embayment and surrounding continental margins.
The findings also help clarify the relationship between deep mantle dynamics and surface volcanism in the region. Marie Byrd Land hosts a belt of Cenozoic volcanoes and elevated topography that some researchers have interpreted as evidence for a mantle plume rising beneath West Antarctica. By tying the Antarctic Geoid Low to a broad, slowly evolving upwelling rooted near the core-mantle boundary, the new modeling provides a physical context for that volcanism without requiring a narrow, stationary plume like those proposed for Hawaii or Iceland. Instead, the region appears to sit atop a wider zone of warm mantle associated with slab graveyards and their compensating upwellings, reinforcing the idea that even the coldest, most remote parts of Earth’s surface are intimately connected to the restless interior far below.
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*This article was researched with the help of AI, with human editors creating the final content.
