Recent warming in a 500-year palaeotemperature record from varved sediments, Upper Soper Lake, Baffin Island, Canada
Bibliographic record
Abstract
Laminated sediments from Upper Soper Lake on southern Baffin Island provide a new 500-year record of temperature change in the Arctic. Radiometric dating, using 210 Pb and Pu, shows that the light-and dark-coloured laminae couplets are annually deposited varves. Dark laminae thickness is strongly correlated to average June temperature from Kimmirut (r = 0.82), reflecting the influence of temperature on snowmelt and fluxes of runoff and suspended sediment. This relationship allowed the construction of a palaeotemperature record that documents large-amplitude interannual to decadal variability superimposed on distinct century-scale trends, including 2°C average warming and maximum temperatures during the 1900s. Similar patterns of change are seen in individual and regionally averaged palaeotemperature records from around the circum-Arctic. Upper Soper Lake records temperatures, rates of change and variance during the twentieth century that are all anomalously high within the context of the last 500 years, and outside the observed range of natural variability. Comparisons of Upper Soper Lake and Arctic average palaeotemperature to proxy-records of hypothesized forcing mechanisms suggest that the recent warming trend is mostly due to anthropogenic emissions of atmospheric greenhouse gases. The magnitude of the warming and decade-scale variability throughout the records, however, indicate that natural forcing mechanisms such as changing solar irradiance and volcanic activity, as well as positive feedbacks within the Arctic environment, also play an important role.
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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 | 0.002 |
| Science and technology studies | 0.002 | 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".