First sulfur isotope measurements in central Greenland ice cores along the preindustrial and industrial periods
Bibliographic record
Abstract
Sulfur isotopes of sulfate have been measured in a discontinuous set of polar ice core samples from Summit, central Greenland, covering the preindustrial (from the fourteenth to the eighteenth century) and industrial (from 1872 to 1969 A.D.) periods. Results have been used to estimate the different source contributions to the deposited sulfate and their evolution along the last centuries. They indicate that the preindustrial background sulfate budget is slightly dominated on a year‐round average by marine biogenic emissions, amounting to close to half of the non‐sea‐salt sulfate (49%). The second contribution is provided by continental sources of secondary sulfate, including background volcanism and, to a lesser extent, continental biota (44% of the non‐sea‐salt sulfate). Sulfur emitted by relatively weak eruptions is found to be largely depleted in 34S compared to bulk volcanic S, suggesting an efficient washout of the heavier isotope during the tropospheric transport. The impact of human‐driven emissions on the sulfate deposited in central Greenland ice is visible in isotope data as early as 1870 A.D. The isotopic signature of anthropogenic sulfur deposited during the twentieth century is found to be constant (δ34S ≈ +3.0 ± 1.5‰), regardless of the changes of dominant source regions and emission processes. This signature is slightly but measurably lighter than the one reported for Arctic haze pollution events.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 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) | 0.000 | 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".