A new study by researchers at the University of Florida and the Paris Institute of Earth Physics reconstructs how this Antarctic gravity low developed over tens of millions of years. The team focused on very slow rock movements in Earth mantle and how those flows reshaped the geoid, the gravity-defined surface to which global sea level roughly conforms.
Co author Alessandro Forte, a professor of geophysics at the University of Florida, said a better understanding of the link between Earth interior, gravity and sea level could improve insight into the growth and stability of large ice sheets. He noted that changes in the Antarctic gravity low appear to overlap in time with major shifts in the continent climate, including the onset of widespread glaciation.
To investigate the origin of the anomaly, Forte and colleague Petar Glisovic used data from a global seismological project that combines earthquake recordings with physics based modeling to reconstruct three dimensional structure inside Earth. They liken the approach to performing a CT scan of the planet, with seismic waves from earthquakes providing the signals that illuminate the interior instead of X rays.
Using this seismic information, the researchers built a model of mantle density variations and then applied physics based calculations to predict the resulting pattern of gravity at Earth surface. The computed gravity map closely matches high precision satellite measurements, which the authors interpret as evidence that their model captures the main features of the interior structure responsible for the observed geoid anomalies.
The team then used sophisticated numerical methods to run the mantle flow backward in time, effectively rewinding interior dynamics over the past 70 million years to the late age of dinosaurs. By tracking how density structures and associated gravity signals evolve in these simulations, they produced a series of snapshots that show the Antarctic gravity low emerging and changing through the Cenozoic.
The reconstructions indicate that the gravity low was initially weaker but began to strengthen between about 50 million and 30 million years ago. This interval coincides with major changes in Antarctica climate system, including the transition from a largely ice free continent to one dominated by extensive ice sheets.
Because gravity helps shape regional sea level, a strengthening low around Antarctica could influence how and where ice sheets grow by subtly altering coastal ocean heights and the buoyancy forces acting on ice margins. Changes in the distribution of mass within the mantle can also affect the elevation of the continent itself, adding another pathway by which deep Earth processes may interact with surface climate.
Forte plans to extend this work by explicitly coupling models of gravity, sea level and vertical land motion to test whether the evolving gravity low played a causal role in the initiation or growth of Antarctic ice. He frames the broader goal as answering how climate at the surface connects to slow but powerful processes far below, where mantle rocks flow on timescales of millions of years.
Research Report:Cenozoic evolution of earth's strongest geoid low illuminates mantle dynamics beneath Antarctica
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University of Florida
The Physics of Time and Space
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