Permafrost at the Ice Base of Recent Pleistocene Glaciations–Inferences from Borehole Temperature Profiles
Bibliographic record
Abstract
Abstract Paleo-temperature reconstruction from precise depth (>2.0 km) well temperature logs can offer information on whether the bed of an ice sheet was frozen. Inversion or upward extrapolation of the >2-km-deep geothermal profile is the only method by which temperature evolution at the base of long-disappeared ice sheets such as the Laurentide and Fennoscandian in the northern part of the Northern Hemisphere in North America and Europe can be inferred. It is obvious from the results from well temperature profiles that there were spatial variations in temperature at the base of the ice sheets during glaciations. This comes as no surprise, since modern-day measurements of temperature profiles through the ice of existing glaciers show a similarly large variability. Present bedrock temperatures measured beneath the central part of the Yukon Rusty glacier are near 0°C to -2°C while Greenland ice sheet base temperatures are -8 and -13°C. In case of very low paleo-temperatures derived from the interpretation of temperature profiles in the areas presently outside the current extent of glacial ice it can be shown that low temperature conditions under glacial ice could facilitate the existence of moderate (some 100-200 m) to thick (0.5 km-1 km) permafrost conditions. It is speculated here that, in many cases, paleo-glacial cold base ice could have existed right on top of paleo-permafrost in sediments just below. Such ice-bonded permafrost may have been frozen to glacial ice above, forming pillars which fixed glacial ice to permafrost below, thus limiting ice movement in such places and resulting in the -extended persistence of permafrost.
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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 | 0.000 | 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 | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.013 | 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".