Palaeo‐ice‐stream onsets: examples from the north‐eastern Laurentide Ice Sheet
Bibliographic record
Abstract
Abstract In this paper we report on observations of glacial landscapes at the head of geomorphologically interpreted palaeo‐ice streams, i.e. palaeo‐ice‐stream onsets. Our work is based on the results of systematic palaeoglaciological mapping of the portion of north‐eastern Canada formerly covered by the Laurentide Ice Sheet. Four different cases are considered and analysed in detail: one is the Dubawnt Lake Ice Stream and the others are smaller (<70 km long) palaeo‐ice streams. We found that in this region onset zones are generally characterized by a heterogeneous landform record and are more easily recognized when landscapes typical of partially frozen beds are present. Based on publicly available topographical and geological data as well as theoretical developments, we discuss the conditions and controls on the location of these onset zones and their potential stability. Except for the Dubawnt Lake Ice Stream, we found that, although topography and geology are important conditioning factors, the geomorphological imprint of palaeo‐ice‐stream onsets cannot be explained without invoking the role of the basal thermal boundary between cold‐ and warm‐based ice. Finally, we observed that, except for the Dubawnt Lake Ice Stream, the onset zones of large ice streams are rarely preserved, and we suggest two possible explanations for this. We conclude that although the same qualitative processes are present under the majority of ice streams, conditions for the preservation of the onset zones are more likely to be met in the case of relatively small ice streams because these are more rapidly deglaciated. Copyright © 2008 John Wiley & Sons, Ltd.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".