Isotopic Analysis of Dissolved CO2 and CH4 in a Coastal Permafrost Zone
Bibliographic record
Abstract
The steady rise in global temperature is likely to perturb the cycling and transfer of carbon in the coastal Arctic. Given the high carbon content of Arctic soils, this region may become an increasingly important source of methane (CH4) and carbon dioxide (CO2) in response to permafrost loss in coming decades. We present targeted observations along a lake to bay system during the spring thaw around Cambridge Bay, in the coastal Canadian high Arctic. In this system, greenhouse gases produced in the freshwater environment are transported to the bay, where they may undergo further transport, transformation, or ventilation to the atmosphere. As warming alters the timing and dynamics of the ice retreat, carbon sources may shift and the magnitude of outgassing may change. We investigate the sources and pathways of the dissolved CO2 and CH4 via radio- and stable carbon isotope analyses, and conduct a spatial survey using a sensor suite containing a dissolved gas extractor, greenhouse gas analyzer, conductivity-temperature-depth probe, and oxygen optode. Across the transect, observed CH4 ranged from 1-5900 ppm, with δ13C values ranging from -70 to -47‰ (mean: -61.1±10.5‰); CO2 ranged from 100-3350 ppm, with δ13C values of -12 to +38‰ (mean: 6.1±13.1‰). Isotopic depletion of 13C correlated with lower CH4, while enrichment consistent with a primary productivity signal was seen in lower CO2 concentrations. Isotopic signatures additionally clustered with habitat type, revealing spatial variability in the processes controlling the production and transformation of CH4. Radiocarbon dating of the dissolved gases indicated predominantly modern carbon sources at all locations, with the high-CH4 melt ponds containing the youngest carbon (mean age of CH4: 148±16 years; mean age of CO2: 252±16 years). This work aims to enhance our understanding of interannual variability in the carbon cycle dynamics at this site, and to assess the system’s response to a changing climate.
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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 | 0.001 | 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".