Recent Permafrost Dynamics in a Subarctic Floodplain Associated with Changing Water Levels, Québec, Canada
Bibliographic record
Abstract
We have reconstructed from tree-rings the dynamics of mineral frost mounds on the floodplain of a subarctic river (Rivière Boniface, northern Québec) likely associated with snow precipitation and temperature changes during the past centuries. Due to their peculiar location in the river bed, we have postulated that the inception and decay of frost mounds (thermokarst ponds) were associated with snow-controlled water levels of the river. The periods of establishment, growth, and mortality of spruce around and in two thermokarst ponds on the shore zone were identified. The oldest tree-ring dates show that permafrost mounds formed during a period of water lowering in the 17th century, likely in a long-enduring sequence of low waters initiated around cal AD 1150 (910 yr BP), which persisted for at least 200 yr until the beginning of the 20th century. Two main periods of spruce mortality were identified, in the late 19th century and early 20th century and in the 1950s–1960s, which corresponded to a rising river level probably due to greater snow precipitation. The patterns of spruce establishment and mortality were strikingly similar in the studied sites. The first spruce to establish were all located along the pond's edges and they were also the first ones to die; most of the youngest spruce established later in the central part of each feature, i.e., in the early to mid-1850s to 1910, and died during the 1950s–1960s. The sequence of events reported here suggests an important lowering of the Rivière Boniface during the first part of the Little Ice Age (end of the 16th century–17th century) which was drier and cold. During the second part of the Little Ice Age (mainly 19th century), greater precipitation occurred and climaxed in the 20th century when climate warmed and the river stage reached its maximum level. Changes in snow precipitation were probably more instrumental than temperature changes in the rise and fall of permafrost landforms because of the snowpack's direct influence on the soil thermal regime and river level during snowmelt.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.028 | 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 teacher head, 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".