Climate simulations of the Permian‐Triassic boundary: Ocean acidification and the extinction event
Bibliographic record
Abstract
The causes for the Permian‐Triassic Boundary (PTB) extinction, the largest mass extinction on record, remain enigmatic. The period is marked by large‐scale volcanic eruptions and evidence for widespread ocean anoxia, which have led to suggestions that these events generated, or played a part in, the extinction. Furthermore, hypercapnia and ocean acidification caused by volcanic emissions of CO2 and CH4 have been put forward as potential kill mechanisms. We present the first PTB climate simulations in which ocean acidity is evaluated directly with a coupled climate‐carbon cycle model. The experiments also address the sensitivity of ocean circulation and oxygen levels to uncertainties in paleogeography and to different bottom topographies. Modeled temperature and precipitation‐evaporation are in good agreement with reconstructions and climate‐sensitive sediments. There is also good agreement between modeled vegetation and reconstructed biomes. The reduction in ocean pH brought about by the increase in atmospheric CO2 is biologically significant. Aragonite saturation levels are low enough to make the whole ocean unsuitable to aragonitic species, and large areas of the ocean become unsaturated in relationship to calcite. No general bottom anoxia is reproduced. Modeled deep ocean O2 concentrations are not significantly impacted by changes in paleogeography and bathymetry, an indication that in our model a change in ocean dynamics resulting from climate warming is not sufficient by itself to generate widespread anoxic conditions during the period.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".