Collapse of a marine-based ice stream during the early Younger Dryas chronozone, western Canadian Arctic
Bibliographic record
Abstract
Abstract New geophysical surveys and sediment cores constrain past dynamics of the Amundsen Gulf ice stream of the northwest Laurentide Ice Sheet (LIS), Arctic Canada, during the last glacial episode. An ice-rafted debris (IRD) unit and its stratigraphic relationship to former grounding lines record the withdrawal of the ∼60,000 km2 marine-based ice stream. Calibrated (cal.) radiocarbon ages from the IRD unit and from ice-contact raised marine sediments indicate that the ice stream retreated ∼250 km over a few centuries or less during the early Younger Dryas, ca. 12.80 ± 0.15 cal. kyr B.P. Despite a likely cooler paleoclimate, ice-marginal recession occurred at rates of at least 1 km/yr, triggered by grounding line retreat from a bathymetric sill and by a concomitant increase in calving margin length. Sediment cores from the adjacent continental slope confirm that the IRD-rich unit was also deposited in the Beaufort Sea as a chronostratigraphic marker bed. Such new evidence for widespread ice rafting establishes Amundsen Gulf as a discrete source area for early Younger Dryas sediment in the Arctic Ocean, including Fram Strait (between Greenland and Svalbard). The timing and scale of iceberg discharges show that Amundsen Gulf was a major conduit for fresh water to the Arctic Ocean during the Pleistocene-Holocene transition.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.007 | 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; both teacher heads agree on what is shown here.
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".