Temporal and spatial variability of the stable isotopic composition of atmospheric molecular hydrogen: observations at six EUROHYDROS stations
Bibliographic record
Abstract
Abstract. Despite the potential of isotope measurements to improve our understanding of the global atmospheric molecular hydrogen (H2) cycle, few H2 isotope data have been published so far. Now, within the EUROpean network for atmospheric HYDRogen Observations and Studies project (EUROHYDROS), weekly to monthly air samples from six locations in a global sampling network have been analysed for hydrogen mixing ratio (m(H2)) and the stable hydrogen isotopic composition of H2 (δ(D,H2), hereafter referred to as δ(D)). The time series thus obtained now cover one to five years for all stations. This is the largest set of ground station observations of δ(D) so far. Annual average δ(D) values are higher at the Southern Hemisphere (SH) than at the Northern Hemisphere (NH) stations; the maximum is observed at Neumayer (Antarctica), and the minimum at the NH midlatitude or subtropical stations. The maximum seasonal differences in δ(D) range from ≈18‰ at Neumayer to ≈45‰ at Schauinsland (Southern Germany); in general, seasonal variability is largest at the NH stations. The timing of minima and maxima differs per station as well. In Alert (Arctic Canada), the variations in δ(D) and m(H2) can be approximated as simple harmonic functions with a ≈5-month phase shift. This out-of-phase seasonal behaviour of δ(D) and m(H2) can also be detected, but with a ≈6-month phase shift, at Mace Head and Cape Verde. However, no seasonal δ(D) cycle could be observed at Schauinsland, which likely reflects the larger influence of local sources and sinks at this continental station. At the two SH stations, no seasonal cycle could be detected in the δ(D) data. Assuming that the sink processes are the main drivers of the observed seasonality in m(H2) and δ(D) on the NH, the relative seasonal variations can be used to estimate the relative sink strength of the two major sinks, deposition to soils and atmospheric oxidation by the hydroxyl (OH) radical. For the NH coastal and marine stations this analysis shows that the relative contribution of soil uptake to the total sink processes increases with latitude.
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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 | 0.001 | 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 | 0.000 | 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".