Shifts in the Isotopic Composition of Nitrous Oxide Between El Niño and La Niña in the Eastern Tropical South Pacific
Bibliographic record
Abstract
Abstract The El Niño‐Southern Oscillation (ENSO) is a natural climate phenomenon that alters the biogeochemical and physical dynamics of the Eastern Tropical Pacific Ocean. Its two phases, El Niño and La Niña, are characterized by decreased and increased coastal upwelling, respectively, which have cascading effects on primary productivity, organic matter supply, and ocean‐atmosphere interactions. The Eastern Tropical South Pacific oxygen minimum zone is a source of nitrous oxide (N 2 O), a potent greenhouse gas, to the atmosphere. Here, we present the first study to directly compare N 2 O sources during opposing ENSO phases using N 2 O isotopocule analyses. Our data show that during La Niña, N 2 O accumulation increased six‐fold in the upper 100 m of the water column, and N 2 O fluxes to the atmosphere increased up to 20‐fold. N 2 O isotopocule data demonstrated substantial increases in δ 18 O up to 60.5‰ and decreases in δ 15 N β down to −10.3‰ in the oxycline, signaling a shift in N 2 O cycling during La Niña compared to El Niño. During El Niño, N 2 O production was primarily due to ammonia‐oxidizing archaea, whereas during La Niña, N 2 O production by incomplete denitrification supplemented that from ammonia‐oxidation, with N 2 O consumption likely maintaining the high site preference values (up to 26.7‰). Ultimately, our results illustrate a strong connection between upwelling intensity, biogeochemistry, and N 2 O flux to the atmosphere. Additionally, they highlight the combined power of N 2 O isotopocule analysis and repeat measurements in the same region to constrain N 2 O interannual variability and cycling dynamics under different climate scenarios.
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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".