The Cenozoic Evolution of Earth’s Strongest Geoid Low: Insights into Mantle Dynamics below 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 actually 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 coincides with abrupt lateral shifts in Earth’s rotation axis at ~50 Ma, validated through paleomagnetic constraints on True Polar Wander. Initially, stable lower mantle contributions dominated the AGL, but over the past ~40 Myr, increasing upper-mantle buoyancy, particularly above ~1300 km depth, amplified the AGL magnitude. This shift stems from the interplay between long-term deep subduction beneath the Antarctic Peninsula and a buoyant, thermally driven upwelling of hot, low-density material from the lowermost mantle. These new results contrast with earlier interpretations, clarifying the crucial role of evolving mantle buoyancy in shaping global geoid anomalies. By incorporating seismic, geodynamic, and mineral-physics data, our reconstructions provide a more comprehensive understanding of mantle flow beneath Antarctica and offer new insights into the dynamic coupling between lower and upper 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".