Younger Dryas and Holocene winter conditions in the Richardson Mountains, Canadian Arctic, reconstructed from precipitation isotopes in relict ice wedges
Bibliographic record
Abstract
Recent retrogressive thaw slump activity in the Richardson Mountains (northwestern Canada), induced by climate warming, has exposed a stratigraphic record of landscape evolution and permafrost development since the last glaciation. Horizontal profiles of five relict ice wedges and one rejuvenation-stage (ca. modern) ice wedge were collected from the headwalls of four thaw slumps in the Willow Creek area of the Richardson Mountains to study post-glacial changes in winter climate. The ice wedges contain vertically elongated bubbles, indicating a likely snowmelt origin. δ2H and δ18O measurements, sampled every ~1.5 cm across the profiles (n = 325), fall well within the range of local winter precipitation values, thereby confirming winter precipitation as the probable source water. Detrital plant macrofossils from several pristine ice samples were AMS 14C dated (n = 16) and confirm at least 2 generations of relict wedge ice dating to the Younger Dryas (YD) and Late Holocene; this is only the second study from the Western Arctic to document YD wedge ice. YD wedge ice is ~2.2‰ more negative in δ18O compared to Late Holocene wedge ice, which could be explained by one or a combination of plausible factors: (i) winter temperatures were up to ~5°C colder on average (e.g., assuming a δ18Oprecip-T sensitivity of 0.41‰·°C-1); (ii) a greater proportion of snow fell during the coldest winter months; or (iii) the moisture source region varied in response to changing atmospheric circulation, moderated by the collapse of the last ice sheet. However, no significant difference is observed in dexcess between YD and Late Holocene wedge ice, which may suggest the precipitation seasonality and moisture source region were comparable. Conversely, the rejuvenation-stage wedge ice, which likely formed in the last few decades, is 1.7‰ more positive in δ18O than Late Holocene wedge ice, while dexcess is statistically indifferent. The strong increase in δ18O in modern wedge ice relative to Late Holocene wedge ice reflects the impact of recent Arctic warming, especially in winter, a pattern that has been previously observed in other ice wedge records from the Canadian and Siberian Arctic. In summary, this study provided insights on winter climate variability in the northwestern Canadian Arctic, with a focus on the YD, Late Holocene and recent times, and demonstrates the potential to use ice wedges to further our knowledge of cold-season climate dynamics in the circum-Arctic more broadly.
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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 | 0.001 | 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".