Insights into the East Antarctic Ice Sheet, 3.5 to 19 Ma, inferred from iceberg provenance
Bibliographic record
Abstract
The past behavior of the Antarctic ice sheets under different climate conditions to today is a topic that bears directly on the stability of the ice sheets under future global warming. While global ice volume history is broadly known from δO in marine sediment records, uncertainties remain, and changes in the geographic extent of the Antarctic ice sheet are not well known. Here we address this deficiency by determining the provenance of Ice-Rafted Debris (IRD) and hence the provenance of the icebergs that carried it, using the isotope geochemical signature of the IRD. ODP Site 1165, 400 km offshore of Prydz Bay, Antarctica, covers the last 20 Ma and is well located to record changes in iceberg provenance over this time. The potential sources of icebergs, Prydz Bay and the coast to the east, have been found to have distinct neodymium and argon isotopic signatures (Roy et al., submitted, van de Flierdt et al., in press). A major provenance change in IRD at Site 1165 is observed between 14 and 7 Ma: before 14 Ma, IRD is locally sourced from the Prydz Bay sector, whereas after 7 Ma, roughly half the IRD comes from the Wilkes Land, Adelie Land, and George V Land. This is likely associated with ice expansion on East Antarctica after the mid-Miocene transition. Additionally, an iceberg drift model has been developed to assess the ocean and climate conditions required to produce the IRD provenance observations. The combination of geochemical provenance analyses and iceberg drift modeling shows promise to be a powerful tool for interpretation of IRD records around Antarctica.
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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 | 0.001 |
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".