The impact of atmospheric <i>p</i>CO<sub><b>2</b></sub> on carbon isotope ratios of the atmosphere and ocean
Bibliographic record
Abstract
Abstract It is well known that the equilibration timescale for the isotopic ratios 13 C/ 12 C and 14 C/ 12 C in the ocean mixed layer is on the order of a decade, 2 orders of magnitude slower than for oxygen. Less widely appreciated is the fact that the equilibration timescale is quite sensitive to the speciation of dissolved inorganic carbon (DIC) in the mixed layer, scaling linearly with the ratio DIC/CO 2 , which varies inversely with atmospheric p CO 2 . Although this effect is included in models that resolve the role of carbon speciation in air‐sea exchange, its role is often unrecognized, and it is not commonly considered in the interpretation of carbon isotope observations. Here we use a global three‐dimensional ocean model to estimate the redistribution of the carbon isotopic ratios between the atmosphere and ocean due solely to variations in atmospheric p CO 2 . Under Last Glacial Maximum (LGM) p CO 2 , atmospheric Δ 14 C is increased by ≈30‰ due to the speciation change, all else being equal, raising the surface reservoir age by about 250 years throughout most of the ocean. For 13 C, enhanced surface disequilibrium under LGM p CO 2 causes the upper ocean, atmosphere, and North Atlantic Deep Water δ 13 C to become at least 0.2‰ higher relative to deep waters ventilated by the Southern Ocean. Conversely, under high p CO 2 , rapid equilibration greatly decreases isotopic disequilibrium. As a result, during geological periods of high p CO 2 , vertical δ 13 C gradients may have been greatly weakened as a direct chemical consequence of the high p CO 2 , masquerading as very well ventilated or biologically dead Strangelove Oceans. The ongoing anthropogenic rise of p CO 2 is accelerating the equilibration of the carbon isotopes in the ocean, lowering atmospheric Δ 14 C and weakening δ 13 C gradients within the ocean to a degree that is similar to the traditional fossil fuel “Suess” effect.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.000 |
| 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 teacher head, 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".