Characterization of atmospheric methane release in the outer Mackenzie River delta from biogenic and thermogenic sources
Bibliographic record
Abstract
Abstract. The Mackenzie River delta is the second largest Arctic river delta in the world. Thin and destabilizing permafrost coupled with vast natural gas reserves at depth, high organic-content soils, and a high proportion of wetlands create a unique ecosystem conducive to high rates of methane (CH4) emission from biogenic and thermogenic sources. Hotspots are known to have a significant contribution to summertime CH4 emissions in the region. Still, little research has been done to determine how often geologic or biogenic CH4 contributes to hotspots in the Mackenzie River delta. In the present study, stable carbon isotope analysis was used to identify the source of CH4 at several aquatic and terrestrial sites thought to be hotspots of CH4 flux to the atmosphere. Walking transects and point samples of atmospheric CH4 and CO2 concentrations were measured. Source stable carbon isotope (δ13C-CH4) signatures were derived from keeling plots of point samples and ranged from −42 ‰ to −88 ‰ δ13C-CH4, identifying both biogenic and thermogenic sources. A CH4 source was determined for eight hotspots, two of which were thermogenic in origin (−42.5 ‰, −44.7 ‰), four of which were biogenic in origin (−71.9 ‰ to −88.3 ‰), and two of which may have been produced by the oxidation of biogenic CH4 (−53.0 ‰, −63.6 ‰), as evidenced by δ13C-CH4 signatures. This indicates that the largest hotspots of CH4 production in the Mackenzie River delta are caused by a variety of sources.
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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 | 0.001 |
| 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 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".