Structure of the upper water column in the northwest North Atlantic: Modern versus Last Glacial Maximum conditions
Bibliographic record
Abstract
During the Last Glacial Maximum, the northwestern North Atlantic constituted a major conduit for Labrador and Greenland ice sheet meltwaters. Vertical density gradients in its upper water masses have been reconstructed by combining information from transfer functions based on dinocysts and from oxygen isotope measurements (δ18O) in planktonic foraminifera. Transfer functions yield temperature and salinity and thus potential density (σθ) for the warmest (August) and coldest (February) months in the photic zone. The δ18O values in different size fractions of epipelagic (Globigerina bulloides) and mesopelagic (Neogloboquadrina pachyderma left‐coiled (Npl)) foraminifera allow us to assess σθ gradients through the pycnocline between surface and intermediate waters, based on the calibration of a σθ versus δ18O relationship from transfer function reconstructions. The size and density of Npl shells provide further constraints on these σθ gradients. The results show the development of a very strong pycnocline during the LGM with a difference of about 3 (summer) to 1.5 (winter) σθ units between surface and underlying waters. They indicate conditions unfavorable for vertical convection and support the hypothesis of the spreading of a shallow, low‐salinity buoyant layer over the northern North Atlantic. This layer depicted a strong E‐W gradient, with maximum seasonal contrast and minimum absolute σθ values westward.
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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 | 0.000 |
| 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 | 0.000 |
| 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 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".