Iodine 129/CFC 11 transit times for Denmark Strait Overflow Water in the Labrador and Irminger Seas
Bibliographic record
Abstract
Iodine 129 discharged from nuclear fuel reprocessing plants in France and the United Kingdom is transported into the Nordic Seas on timescales of 3–5 years. Tracer 129I is subsequently injected into intermediate waters that overflow the sills between Greenland, Iceland, and Scotland and ventilate the North Atlantic Deep Waters (NADW). During the early 1990s, discharges of 129I increased by 600%, resulting in a large, well‐resolved tracer “front” whose passage through the Nordic Seas is presently being observed by a time series of 129I measurements on the WOCE (AR7W) section in the Labrador Sea. The highest 129I levels were measured below depths of 3000 m in Denmark Strait Overflow Water (DSOW). These levels increased by about 300% between 1997 and 2001 to values >40 × 107 atoms/L, indicating that the leading edge of the tracer “front” from the early 1990s was being observed entering the NADW. Using a simple mixing/advection model, 129I and CFC 11 results were used to calculate transit times of 0.4–2.6 years for the flow of DSOW from formation regions in the Nordic Seas to the Labrador Sea. Measurements on samples collected in the Irminger Sea in 2001 gave transit times of 0.3 years for core DSOW immediately south of Denmark Strait and about 2 years for locations off the southern tip of Greenland. An increase in DSOW transit times observed in the Labrador Sea between 1999 and 2001 probably reflects a more general weakening in the subpolar gyre of the North Atlantic during the 1990s.
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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 | 0.001 | 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".