Regional estimates of POC export flux derived from thorium-234 in the western Arctic Ocean
Bibliographic record
Abstract
In order to elucidate the regional export variation of particulate organic carbon in the western Arctic Ocean, samples vertically integrated between 0 and 100 m depth or between 0 and 30 m/40 m depth were collected for total 234Th measurements and those from 30 m/40 m or 100 m depth were collected for particulate 234Th measurements during the Second Chinese Arctic Expedition in July-September 2003. The removal fluxes and residence time of 234Th in the upper water column were calculated by using irreversible steady-state scavenging model. The results showed that, total 234Th was deficit relative to its parent 238U in the western Arctic Ocean except in the western Chukchi shelf and the slope regions around 160°W, indicating that scavenging and removal processes play an important role in element biogeochemical cycle in the Arctic Ocean. In the western Chukchi shelf and the slope regions around 160°W, total 234Th was excess relative to 238U, ascribing to the horizontal input of 234Th adsorbed by ice-rafted sediments. Thorium-234 removal fluxes decreased from the shelf to the deep ocean, while the residence time of 234Th increased from shelf to offshore, demonstrating that particle scavenging and removal processes are more active in the shelf regions. The estimated POC export fluxes from 40 m in the shelf regions and from 100 m in the slope and deep ocean varied between 1.6 and 27.5 mmol/(m2·d), and between 1.8 and 14.4 mmol/(m2·d), respectively. The averaged POC export fluxes over the entire water column decreased from the shelf to the deep ocean, indicating that the Chukchi shelf is an important region for organic carbon sequestration. The high ThE ratios (ratio of POC export flux derived from 234Th/238U disequilibria to primary production) in the western Arctic Ocean suggested that the biological pump runs actively in high-latitudes.
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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) | 0.001 | 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) | 0.000 | 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".