Insights into constraining coastal carbon export from radioisotopes
Bibliographic record
Abstract
Coastal shelves are important regions for carbon transformation and storage, however, constraining coastal carbon budgets and their uncertainties remains a challenge. Repeated sampling of a semi-restricted coastal basin in Nova Scotia, Canada was performed in 2019 utilizing the 238U-234Th isotope system to estimate carbon flux in both the water column and surface sediments. 234Th fluxes in the Bedford Basin water column appeared to be in relative balance with those arriving at the seafloor averaged over spring and summer. The resulting carbon export estimates averaged ~70 mmol C m-2 d-1 for April through August of 2019 and 234Th-derived annual export estimates (19 mol C m-2 yr-1) were within a factor of three of the model-based estimates for the basin. Incorporating the results from prior research, this study constrains the major carbon sources and sinks in Bedford Basin. While the 238U-234Th method is well-established in the open ocean, its use in coastal shelf regions is still evolving. Pronounced 234Th deficits are unique to coastal zones and continue to raise important questions about the physical and biogeochemical factors that influence tracer distributions and the carbon estimates that are derived from them. Future paths and method refinements for utilizing the 238U-234Th system in coastal regions are put forth here, including the use of size-fractionated sampling, the need for boreal winter estimates, the quantification of horizontal mixing contributions, an analysis of the role of small particles in coastal carbon budgets, and the study of sediment resuspension’s impact on tracer distributions.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 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 | 0.001 |
| Open science | 0.001 | 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".