Direct evidence of sediment carbonate dissolution in response to bottom-water acidification in the Gulf of St. Lawrence, Canada
Bibliographic record
Abstract
Over the past century, dissolved oxygen concentrations have decreased and metabolic CO2 has accumulated in the bottom waters of the Gulf of St. Lawrence (GSL) and Lower St. Lawrence Estuary (LSLE). Oxygen depletion has been attributed primarily to changes in ocean circulation in the northwest Atlantic Ocean, as well as an increase in the flux of organic matter at or near the seafloor and its accompanying biological oxygen demand. The accumulation of metabolic CO2 in these waters has led to their progressive acidification and a decrease in pH (0.3–0.4 pH unit) commensurate to the variation expected for global oceanic surface waters by the end of this century, albeit by a different mechanism (anthropogenic CO2 uptake from the atmosphere). The decrease in bottom-water pH of the GSL and LSLE is accompanied by a decrease in the carbonate ion concentration and the saturation state of the waters with respect to both calcite and aragonite (ΩC and ΩA). Although the Laurentian Trough sediments are mostly devoid of modern calcium carbonate fossils, detrital (Ordovician/Silurian) carbonates, eroded from Anticosti Island, accumulate on the seafloor. Evidence of carbonate mineral dissolution in the sediments of the Laurentian Trough is examined and supported by pore-water data and vertical variations of their inorganic carbon content. Historical, solid-phase profile data are used to estimate temporal variations of the sedimentary calcite dissolution rates and document the anthropogenic modification of the sediment record.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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".