Decadal Trends in Oxygen Concentration in Subsurface Waters of the Northeast Pacific Ocean
Bibliographic record
Abstract
Previous studies have shown decreasing oxygen concentration (O2) in subsurface waters of the continental slope from California to Canada since about 1980. With longer time series we show that from southern California to northern Canada increasing O2 preceded these decreases from 1950 to about 1980. Because there has been no clear trend since 1950, we cannot yet conclude that anthropogenic climate change is the cause of these decreasing trends after 1980. These findings are based mainly on O2 on the 26.7 potential density (σθ) surface in the region north of 30°N and east of 170°W, covering both the continental margin and deep-sea regions. On the continental slope, O2 increased at most locations by 10 to 20 µmol kg−1 to about 1980, followed by declines of similar magnitude in recent years. Changes in O2 were associated with changes in temperature of the opposite sign south of 37°N, but correlation of temperature and O2 is irregular in more northerly locations. At all locations, temperature-related solubility change was a minor cause of these O2 trends. In deep-sea waters, O2 decreased with time with a more rapid decrease from about 1995 to about 2003. At Ocean Station P (OSP; 50°N, 145°W), which has the longest uninterrupted record of observations, significant linear trends of −0.4 to −0.5 µmol kg−1 y−1 were found on the 26.5, 26.7, and 26.9 σθ surfaces. In addition, a significant sinusoidal oscillation of period 18.61 years and amplitude of 18 µmol kg−1 was found on the 26.9 σθ surface at OSP and a station 400 km to the east, which fits reasonably well with the lunar nodal cycle. The phase of this oscillation was identical at both locations. Clear evidence of similar variability did not emerge at other open-ocean locations or along the continental slope.
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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 | 0.000 | 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".