Tracking atmospheric carbon emissions in southern Ontario, Canada using dendrochronological records
Bibliographic record
Abstract
Records of environmental change are often temporally short, perhaps spanning a few decades. For many environmental issues impacting the world today, we have very limited observations or data concerning those changes. Therefore, we need to supplement the short observational and instrumental records of environmental change with proxy data sources. Tree-ring growth records are one type of proxy data source that can be examined at annual timescales to track changes in the environment across longer periods than afforded by relatively short observations and instrumental data records. Changes in the composition of some gases in the atmosphere, are one example of environmental change that can be elucidated using tree-ring records. Trees utilize various forms of carbon dioxide during photosynthesis, including radiocarbon (14C). Naturally, 14C in the atmosphere varies through time due to cosmic ray flux and ocean-atmosphere dynamics. The concentration of 14C also varies due to anthropogenic activities, including burning of fossil fuels, nuclear bomb testing, and the operation of nuclear power plants (NPPs). Tree rings record atmospheric 14C concentration during the growing season and are an effective tool to trace 14C in the atmosphere from a variety of sources, including NPPs. In Southern Ontario, Canada there are 15 operational CANDU reactors at three NPPs (Bruce (8), Darlington (1) and Pickering (6)). Southern Ontario is also one of the most densely populated regions of Canada and is a major source of fossil fuel derived carbon that is depleted in 14C. Monitoring of atmospheric 14C in Ontario is conducted at the Centre for Atmospheric Research Experiments, operated by Environment and Climate Change Canada (ECCC). The facility is considered a clean air site, located approximately halfway between the Bruce and Darlington NPPs. We measured the Δ14C in tree rings from white spruce (Picea glauca) trees sampled across a west-east geographic transect between the NPPs with the aim of better understanding how the atmospheric concentration of 14C has varied locally in this region, while also attempting to pinpoint sources of 14C emissions. Data from our clean-air sites track globally derived 14C data from the Jungfraujoch clean-air atmospheric sampling site in Switzerland. Tree-ring 14Cmeasurements from our most densely populated site near the city of Toronto are depleted in 14C, reflecting fossil fuel combustion. Conversely, 14C measurements at our site nearest the Pickering and Darlington NPPs are the most enriched. Our results give insight into how tree rings record 14C and how well they compare to established atmospheric sampling techniques.
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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 | 0.002 | 0.005 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".