A gravitational anomaly beneath Antarctica, persisting for at least 70 million years, has undergone shifts in intensity and location over millennia, according to a study published in the journal Scientific Reports. Researchers Petar Glišović and Alessandro M. Forte utilized seismic data and physical simulations to investigate the processes within Earth’s interior that created the anomaly and its connection to the region’s geological and climatic history.
The analysis establishes that the Antarctic geoide depression – the reference surface reflecting variations in Earth’s gravitational field – has existed for at least 70 million years, though its strength and position have substantially changed. Initially located in the South Atlantic during the early Cenozoic era, the anomaly migrated towards the South Pole between 40 and 30 million years ago, the study found.
According to the researchers’ models, the Antarctic geoide depression experienced fluctuating intensity between 70 and 35 million years ago. Since approximately 35 million years ago, its magnitude has increased by 30 percent. This change coincides with a significant alteration in Earth’s rotational axis, identified through paleomagnetic records as the True Polar Wander, which occurred around 50 million years ago.
The reconstruction of mantle flow indicates that, in the area where the depression is now located, the anomaly was originally due to density differences in the deeper layers of the mantle, accounting for 30 to 50 percent of its total intensity. However, over the last 35 million years, the shallower mantle layers have played an increasingly significant role. The study indicates that the contribution from the upper mantle has risen while that of the middle mantle has declined, intensifying the geoide depression under Antarctica.
To investigate the changes in the gravitational depression beneath Antarctica, the scientists employed a technique called back-and-forth nudging (BFN). This method allowed them to simulate the movements of Earth’s mantle both forward and backward in time, combining earthquake data – which helps visualize Earth’s interior – with information on plate movements and the physical properties of subsurface minerals. In their models, plate movements were not predetermined but emerged naturally from the flow of material within the planet.
The researchers also adjusted the model to ensure the mantle’s properties were as realistic as possible, using data on plate speeds and Earth’s response to glaciers. Multiple model variations were tested, and the primary result remained consistent: the gravitational depression under Antarctica followed a persistent and well-defined pattern throughout time.
The study suggests links between the deep dynamics of the planet and the onset of major Antarctic glaciers. The authors propose that fluctuations in the gravitational depression beneath Antarctica influence the relative height of sea level in the region, potentially impacting the conditions for the formation and growth of ice sheets. A current of warmer, less dense material rising from the deepest layers of Earth’s mantle has been active beneath Antarctica for 70 million years and may have contributed to lifting the landmass in the continent’s center. Scientists connect this internal movement to the presence of hidden mountains under the ice and the beginning of the formation of large Antarctic glaciers approximately 34 million years ago.
The researchers state that further investigation is needed to fully understand how these changes within Earth affect sea level and the climate in Antarctica. University of Florida’s Alessandro Forte stated, “The goal is to address a substantial question: ‘How does our climate connect to what’s happening inside the planet?’”
