A recent investigation conducted by geophysicists from the University of Florida and the Paris Institute of Earth Physics traces the origin of the Antarctic gravitational low—also known as the Antarctic geoid anomaly, the planet’s most extreme gravitational deviation—to slow-moving subterranean rock flows that unfolded over tens of millions of years. The findings of this research were published in the journal Scientific Reports.
“By gaining a better grasp of how Earth’s interior structure impacts gravity and sea level, we can gain insight into the mechanisms that may be relevant for the accretion and stability of major ice sheets,” stated Professor Alessandro Forte of the University of Florida.
These variations in gravitational pull, stemming from differing rock densities deep beneath the surface, are minor in absolute terms. However, they can exert a notably strong influence on the oceans.
In areas where gravity is weaker, the ocean surface tends to sit slightly lower relative to Earth’s core because water migrates towards regions experiencing stronger gravitational attraction.
Because of this gravitational void, the sea level surrounding Antarctica is noticeably lower than it otherwise would be.
In this novel study, Professor Forte and Petar Glišović from the Paris Institute of Earth Physics mapped the Antarctic geoid anomaly and demonstrated its evolution throughout the Cenozoic Era, the span from 66 million years ago up to the present day.
The researchers leveraged a comprehensive global scientific project that integrated worldwide earthquake records with physical modeling to reconstruct the three-dimensional structure inside the Earth.
“Imagine performing a CT scan on the whole Earth, but instead of X-rays like in a medical setting,” explained Professor Forte, “we have earthquakes. Seismic waves provide the ‘illumination’ that lights up the planet’s interior.”
By considering all the material illuminated by Earth’s seismic waves and employing physical models to forecast the gravitational landscape, the scientists reconstructed a gravitational map for the entire planet.
This reconstructed map correlated precisely with benchmark gravitational data gathered from satellites, validating the fidelity of the underlying models used in the reconstruction.
The most demanding phase followed: reversing time to observe how the Antarctic geoid depression developed over millennia.
Utilizing sophisticated computational models, they were able to recreate the subsurface rock movement dynamics within the formation using physics-based reconstructions, tracking the changes across the last 70 million years.
Earlier visualizations indicated that the Antarctic geoid depression was less pronounced during its initial development stages.
Subsequently, between perhaps 50 and 30 million years ago, the gravitational anomaly began to gain intensity.
These events coincide temporally with major shifts in Antarctica’s climatic system, including the onset of widespread glaciation.
“We aim to investigate potential causation between the intensifying gravitational sink and the ice sheets by employing new models that couple gravity, sea level, and continental uplift changes,” Professor Forte remarked. “The ultimate goal is to answer a fundamental question: how does our climate connect to the processes unfolding within our planet’s interior?”
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