Oxygen in the deep Strait of Georgia, 1951–2009: The roles of mixing, deep‐water renewal, and remineralization of organic carbon
Bibliographic record
Abstract
The concentration of oxygen in the deep Strait of Georgia has declined at a rate of 0.45–1.3 µmol L−1 yr−1 since 1971 and now seasonally approaches thresholds of biological tolerance. The decline has resulted principally from the increasing hypoxia of upwelled Pacific Ocean water. Local anthropogenic loadings have little potential to reduce bottom water oxygen concentrations. Hypoxic, upwelled water mixes vigorously with surface water in the tidal passages of Haro Strait before entering the deep Strait of Georgia during a series of deep‐water renewal events in late spring and late summer. Remineralization of at least 22 µmol L−1 yr−1, together with diffusive mixing, reduces the bottom water oxygen concentration to a winter minimum of 90–110 µmol L−1. Linear extrapolation of the long‐term trend indicates that parts of the Strait could become episodically hypoxic (< 62.5 µmol L−1; < 1.4 mL L−1) as early as 2042. However, water mass modeling shows that the mixing with surface water in Haro Strait limits the potential of the shelf water to reduce the oxygen concentration in the deep Strait; even should the shelf water become completely anoxic, the concentration of oxygen in bottom waters would level off just above 90 µmol L−1 after 3 yr. Increasing surface water temperature will reduce the solubility of oxygen, but this effect is projected to cause a further decline of only 2.2 µmol L−1 over the next 25 yr. Despite its restricted circulation, the deep Strait of Georgia is less threatened by hypoxia than are many other coastal areas, because of the combination of light‐limited primary production and intense tidal mixing in the approaches, which replenishes the deep‐water oxygen annually.
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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 | 0.000 | 0.001 |
| 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".