Contrasting trends of the ocean CO2 sink and pH in the agulhas current system and the Mozambique basin, south-western Indian ocean (1963–2023)
Bibliographic record
Abstract
We describe new observations of the oceanic carbonate system in the South-Western Indian Ocean obtained in January 2021 (OISO-31 cruise) and May 2022 (RESILIENCE cruise). To evaluate the decadal trends and drivers of fugacity of CO 2 (fCO 2 ), air-sea CO 2 fluxes, dissolved inorganic carbon (C T ) and pH, we used available data in this region over 1963–2023 and compared the results in the Mozambique Basin and in the Agulhas region near the African coast. Over 1995–2023, we found a faster fCO 2 increase in the Mozambique basin (2.03 ± 0.07 μatm.yr −1 ) compared to the coastal zone (1.37 ± 0.07 μatm.yr −1 ). The temporal change of anthropogenic CO 2 concentrations estimated in subsurface enables to reconstruct the carbonate system properties since the 1960s. In the Mozambique Basin the CO 2 sink increased slightly over 1960–2022 with a maximum observed in May 2022 (−2.4 mmolC.m −2 .d −1 ). In the coastal zone, the ocean CO 2 sink increased from near equilibrium in the 1960s to a maximum observed in May 2022 (−4.2 mmolC.m −2 .d −1 ). In both regions, we found a decrease of pH, most pronounced in the open ocean zone (−0.020 ± 0.001.decade −1 over 1995–2023). The lowest pH of 8.04 was observed in January 2021, 0.11 lower than in the 1960s. The increase of the CO 2 sink and the decrease of pH were mainly driven by anthropogenic CO 2 uptake, with about 10% due to the ocean warming.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 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".