Nd and Pb isotope signatures of the clay-size fraction of Labrador Sea sediments during the Holocene: implications for the inception of modern deep circulation pattern
Bibliographic record
Abstract
Nd and Pb isotopes were measured on the fine fraction of one sediment core drilled off southern Greenland (MD99-2227). This work aims to reconstruct the evolution of deep circulation patterns in the North Atlantic during the Holocene on the basis of sediment supply variations. For the last 12 kyr, three sources are involved in the sediment mixture: the North American Shield, the Panafrican and Variscan crusts, the Mid-Atlantic Ridge. Clay isotopic signatures indicate two mixtures of sediment sources for the last 12 kyr. The first mixture (12.2-6.5 kyr) is composed of material derived from the North American shield and from a ‘young’ crustal source. From 6.5 kyr onward, the mixture is defined by a ‘young’ crustal component and by a mantellic component characteristic of the Mid-Atlantic Ridge. Since the significant decrease of proximal deglacial supplies, the evolution of the relative contributions of the sediment sources implies major changes in the relative contributions of the Western Boundary Undercurrent components for the last 8.4 kyr. The progressive intensification of the Western Boundary Undercurrent is associated with the transport of the North East Atlantic Deep Water until 6.5 kyr then, by the Denmark Strait Overflow Water mass. The setting up of the modern circulation pattern at 3 kyr suggests a decrease of the control by the Denmark Strait Overflow Water mass. This change is synchronous with inception of the Labrador Sea Water mass. Our isotopic dataset emphasizes several changes in the relative contribution of the North Atlantic Deep Water components through the Holocene.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| 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 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".