Radiocarbon ages of western Pacific intermediate waters during the past 25 kyrs: Implications for global carbon cycling
Bibliographic record
Abstract
The rapid increase of atmospheric carbon dioxide (CO2) and the concurrent decline in Δ14C during the last deglaciation were mainly ascribed to the release of old, 14C-depleted CO2 from an abyssal ocean reservoir, specifically the Southern Ocean, or the deep Pacific Ocean via intermediate waters. In support of this hypothesis, several records from intermediate waters around the globe depict a drop in Δ14C during the deglaciation. However, other records closer to the source regions of intermediate waters do not depict this anomaly and thus, question the hypothesis. Alternative scenarios include the release of 14C-depleted CO2 by hydrothermal vents, volcanoes and pockmarks. An ideal region to test the hypothesized scenarios is the western equatorial Pacific Ocean (WEP), where intermediate waters of southern and northern origin converge.We present paired planktic and benthic foraminiferal 14C ages from a depth transect (404 – 2210 m) of seven gravity cores from the WEP that cover the past 25 kyrs. Our records do not show any discernible Δ14C anomaly during the Last Glacial Maximum and initial deglaciation making the WEP an unlikely candidate for the release and ventilation of oceanic CO2 to the atmosphere. However, the intermediate-depth records consistently show anomalously low benthic Δ14C values during the final stage of the deglaciation and early Holocene. This Δ14C variability will be discussed in the context of potential sources and mechanisms.
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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 | 0.001 |
| 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".