North Atlantic Evidence for a Unipolar Icehouse Climate State at the Eocene‐Oligocene Transition
Bibliographic record
Abstract
Abstract Earth's climate transitioned from a warm unglaciated state to a colder glaciated “icehouse” state during the Cenozoic. Extensive ice sheets were first sustained on Antarctica at the Eocene‐Oligocene Transition (EOT, ~34 Ma), but there is intense debate over whether Northern Hemisphere ice sheets developed simultaneously at this time or tens of millions of years later. Here we report on EOT‐age sediments that contain detrital sand from Integrated Ocean Drilling Program Sites U1406 and U1411 on the Newfoundland margin. These sites are ideally located to test competing hypotheses of the extent of Arctic glaciation, being situated in the North Atlantic's “iceberg alley” where icebergs, calved from both the Greenland Ice Sheet today, and the Laurentide Ice Sheet during the Pleistocene, are concentrated by the Labrador Current and deposit continentally derived detritus. Here we show that detrital sand grains present in these EOT‐aged sediments from the Newfoundland margin, initially interpreted to represent ice rafting, were sourced from the midlatitudes of North America. We find that these grains were transported to the western North Atlantic by fluvial and downslope processes, not icebergs, and were subsequently reworked and deposited by deep‐water contour currents on the Newfoundland margin. Our findings are inconsistent with the presence of extensive ice sheets on southern and western Greenland and the northeastern Canadian Arctic. This contradicts extensive bipolar glaciation at the EOT. The unipolar icehouse arose because of contrasting latitudinal continental configurations at the poles, requiring more intense Cenozoic climatic deterioration to trigger extensive Northern Hemisphere glaciation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 teacher head, 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".