The organization of subglacial drainage during the demise of the Finnish Lake District Ice Lobe
Bibliographic record
Abstract
Unknown basal characteristics limit our ability to simulate the subglacial hydrology of rapidly melting contemporary ice sheets. Sediment-based landforms generated beneath Late Pleistocene ice sheets, together with detailed digital elevation models, offer a valuable means of testing basal hydrology models, which describe the flow and dynamics of water in the subglacial system. However, to date no work has evaluated how well process-based subglacial hydrology models represent the hypothesized conditions associated with glaciofluvial landform formation in the palaeo setting. Previous work comparing model output to geomorphological evidence has typically done so using models that do not resolve subglacial processes and instead express likely subglacial water pathways. Here, we explore the ability of the Glacier Drainage System model (GlaDS), a process-based subglacial hydrology model, to represent the genesis conditions associated with a specific glaciofluvial landform termed “murtoos”. Distinctive triangular landforms found throughout Finland and Sweden, murtoos are hypothesized to form 40–60 km from the former Fennoscandian Ice Sheet margin within a “semi-distributed” system at the onset of channelized drainage in small cavities where water pressure is equal to or exceeds ice overburden pressure. Concentrating within a specific ice lobe of the former Fennoscandian Ice Sheet and using digital elevation models with a simulated former ice surface geometry, we forced GlaDS with transient surface melt and explored the sensitivity of our model outcomes to parameter decisions such as the system conductivity and bed topography. Our model outputs closely match the general spacing, direction, and complexity of eskers and mapped assemblages of features related to subglacial drainage in “meltwater routes”. Many of the predictions for murtoo formation are produced by the model, including the location of water pressure equal to ice overburden, the onset of channelized drainage, the transition in drainage modes, and importantly the seasonal sequence of drainage conditions inferred from murtoo sedimentology. These conclusions are largely robust to a range of parameter decisions, and we explore seasonal and inter-annual drainage behaviour associated with murtoo zones and meltwater pathways. Our results demonstrate that examining palaeo basal topography alongside subglacial hydrology model outputs holds promise for the mutually beneficial analyses of palaeo and contemporary ice sheets to assess the controls of hydrology on ice dynamics and subglacial landform evolution.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 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".