Bridging the gap between bromocarbon oceanic emissions and upper air concentrations
Bibliographic record
Abstract
Abstract. Oceanic emissions of halogenated very short-lived substances (VSLS) are expected to contribute significantly to the stratospheric halogen loading and therefore to ozone depletion. Estimates of the amount of VSLS transported into the stratosphere are highly uncertain and based on sporadic observations around the tropical tropopause layer (TTL) and on modeling studies which use prescribed emission scenarios to reproduce observed atmospheric concentrations. Actual measurements of VSLS emissions at the ocean surface have not been linked to the stratospheric halogen loading until now. Here we use observations of oceanic VSLS emissions in the western Pacific and an atmospheric Lagrangian transport model to estimate the direct contribution of bromoform (CHBr3), and dibromomethane (CH2Br2) to the stratospheric bromine loading. Our emission-based estimates of VSLS profiles provide the first link between observed oceanic emissions and in situ TTL measurements. The emission-based and observed profiles of CHBr3 show good agreement, confirming the importance of the western Pacific as a source region. However, CH2Br2 emission-based estimates are considerable smaller than current upper air observations as a result of relatively low western Pacific emissions. We estimate the relative importance of the highly variable emission rates and the surface to stratosphere transport for the contribution of the two bromocarbons to the stratospheric bromine budget. Our results show that stratospheric entrainment of bromine in form of VSLS or their degradation products is highly variable and that this variability is primarily linked to the variability of the observed sea-to-air flux. Together, both bromocarbons contribute to the stratospheric bromine budget with 0.4 pptv on average and 2.3 pptv for cases of maximum emissions.
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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 | 0.000 | 0.000 |
| 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) | 0.000 | 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 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".