Cenozoic evolution of earth’s strongest geoid low illuminates mantle dynamics beneath Antarctica
Bibliographic record
Abstract
Constraining the long-term evolution of geoid anomalies is essential for unraveling Earth's internal dynamics. While most studies focus on present-day geoid snapshots, we reconstruct the time-dependent evolution of Earth's strongest geoid depression, the Antarctic Geoid Low (AGL), over the Cenozoic. Unlike geodetic reference frames that place the deepest geoid low in the Indian Ocean, a geodynamic perspective - relative to a hydrostatic ellipsoid - reveals the strongest nonhydrostatic geoid depression resides over Antarctica. Using a back-and-forth nudging technique for time-reversed mantle convection modeling, we leverage 3-D mantle density structures derived from seismic tomography and geodynamic constraints. Our results show that the AGL has persisted for at least ~70 Myr, undergoing a major transition in amplitude and position between 50 and 30 Ma. This transition coincides with an abrupt lateral shift in Earth's rotation axis at ~50 Ma, independently validated through paleomagnetic constraints on True Polar Wander. Initially, the AGL was supported by stable lower mantle density anomalies, but over the past ~40 Myr, an increasing contribution from upper-mantle buoyancy - particularly above ~1300 km depth - amplified the AGL magnitude. This shift reflects the interplay between long-term deep subduction beneath the Northwest Antarctic margin and a broad, thermally driven upwelling of buoyant material sourced from the lowermost mantle. These results contrast with earlier interpretations by demonstrating the crucial role of time-dependent coupling between both positive and negative mantle buoyancy in shaping global geoid anomalies. By integrating seismic, geodynamic, and mineral-physics data, our reconstructions provide a dynamically consistent view of mantle flow beneath Antarctica and offer new insights into the coupling between deep and shallow mantle processes that govern Earth's long-wavelength geoid evolution.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".