Regional geothermal effects on subglacial water routes beneath the last Cordilleran ice sheet
Bibliographic record
Abstract
The Cordilleran ice sheet, which covered the mountain ranges of north-western America during the last glacial\ncycle, provides an ideal setting to study the effect of geothermal anomalies on subglacial water routing beneath\nlarge-scale ice masses. First, the Cordilleran ice sheet rested directly on a geologically old yet still active subduction\nzone, which is responsible for significant geothermal variability in the region. Second, the deep valleys and\nintramontane basins that characterize the Cordilleran topography tend to act as flux wells to further enhance the\nheterogeneity of this geothermal distribution. Third, compared to the currently ice covered areas such as Greenland\nand Antarctica where direct observations of the geothermal distribution are exceedingly rare, the region of\nthe North American Cordillera offers insights into geothermal variability from numerous borehole measurements\ntaken across western territories of the US and Canada. Fourth and last, the subglacial water system left ample\nevidence on the landscape, including vast esker systems, deep canyons and subglacial lake sediments, allowing for\nan interpretation of the modeled hydrological networks and their comparison with geological data.\nHere we use the Parallel Ice Sheet Model (PISM) to simulate ice dynamics and simplified subglacial hydrology of\nthe Cordilleran ice sheet through the last 120 000 years. We test several existing reconstructions of the geothermal\nflux from direct and indirect observations versus a uniform distribution of heat flux to isolate the effects of regional\ngeothermal variability on thermo-hydrological conditions at the base of the last Cordilleran ice sheet. We find\nthat the uncertainties in the geothermal flux distribution as well as regional geothermal anomalies present in the\nreconstructions have little effect on the modelled ice extent and thickness, but they affect the distribution of melt\nrate and water routes beneath the ice sheet. All but one of the reconstructions used result in increased water content\nin the Fraser Valley system due to high geothermal heat flux in upstream zones, showing the role of these regional\nanomalies on the formation of subglacial lakes previously documented by geomorphology in this region.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".