Large-scale palaeoflow at the top of Earth's core
Bibliographic record
Abstract
A number of recent studies have made use of statistics derived from geodynamo simulations to constrain the flow at the top of the Earth's core. Here we adapt these methods to infer possible core surface flow solutions over the past 9000 years, using a low degree geomagnetic field model, based on archaeomagnetic and sedimentary archives. Despite the low spatial resolution of the field model, we find that the largest scale aspects of the recovered flow agree well with those derived from historical field models. In particular we see the growth of an eccentric planetary gyre over the past 400 years and find that a similar feature appears on bimillennial timescales, concurrent with pulses in the zonal flow. In the flow model vigorous gyre structures are not persistent but appear as transient features with durations of a few hundred years. The zonal flow is westward over the entire period with a mean value of 0.09° /yr. Finally, we consider the variations in length-of-day that are implied by the flow model under the assumption of geostrophy, and compare the total clock error with that inferred from records of historical solar eclipses. Good agreement is found between the two series of mantle rotation for at least the past 1200 years, with anomalously slow mantle rotation coupled with reduced westward zonal flow. Further back in time a rigorous assessment is hard to make, owing to uncertainty surrounding the exact locations of eclipses.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| 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".