Reconstruction of Paleoclimate Time-Series in the Peace-Athabasca Delta, Northern Alberta, from Stable Isotopes in Tree-Rings
Bibliographic record
Abstract
The isotopic labelling of carbon in tree-rings varies as a function of growth season temperature and relative humidity. The isotopic labelling of oxygen in tree-rings varies as a function of source-water isotopic composition and humidity-dependent evaporative enrichment of leaf water during the growth season. The season of carbon-isotope labelling was identified statistically as late-spring to early-fall (April to October) for temperatures and relative humidity with a three-year weighted (50-30-20) carry-over due mainly to stored photosynthates. The season of oxygen-isotope labelling was identified statistically as a combination of a winter (pDecember to March) source-water signal (temperature-dependent precipitation isotope composition) with a late-spring to early-fall (April to October) humidity signal (evaporative enrichment of leaf water). A two-year carry-over was attributed to the residence time of soil water, but no notable photosynthate carry-over was identified. Carbon- and oxygen- (mechanistic) isotope response surface models were then compared and contrasted to regression-based bivariate and univariate models. It was found that in most cases the isotope response surface models were the best means of predicting isotopic labelling when environmental data are known. The carbon-isotope response surface was used to reconstruct 50-years (AD 1900-1954) of relative humidity data by introducing measured carbon isotope values and instrumental growth season temperature. During the analysis of the oxygen-isotope response surface we found an isotope-temperature relation that appears to reflect circulation-dependent damping. To verify this we introduced scaled values of the North Pacific index as a proxy for this suppression. The coupling of the isotope response surfaces generated a humidity reconstruction that is also thought to be driven by atmospheric circulation. Our reconstruction shows that the fluctuations in temperature range have not exceeded the natural variability in the instrumental record of the 20th century; however, the atmospheric moisture (humidity) reconstruction predicts a directional drying trend in the Peace-Athabasca Delta that appears to reflect increasingly zonal circulation in western Canada over this period.
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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 | 0.001 | 0.001 |
| 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) | 0.001 | 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".