Subglacial drainage patterns of Devon Island, Canada: Detailedcomparison of river and tunnel valleys
Bibliographic record
Abstract
Abstract. Tunnel valleys are bedrock incised channels (N-channels) attributed to erosion by meltwater in subglacial conduits. They exert a major control on meltwater accumulation at the base of ice sheets, serving as drainage pathways and modifying ice flow rates. Exposed relict tunnel valleys offer a unique opportunity to study the geomorphologic fingerprint of subglacial erosion and characterize the geometry of individual channels. In this study we present field and remote sensing observations of exposed tunnel valleys on Devon Island (Canadian Arctic Archipelago), including descriptions of tunnel valley cross sections and longitudinal profiles, as well as network morphology, to describe the spatial extend and distinctive characteristics of subglacial drainage systems. We use field-based GPS measurements of tunnel valley longitudinal profiles, along with stereo imagery derived Digital Surface Models (DSM), and novel kinematic mobile LiDAR data to establish a quantitative comparison of tunnel and river valleys in our field study area. Tunnel valleys typically cluster in groups of 5-10 channels throughout the island, oriented radially with respect to active or former ice margins. We identify departures in tunnel valley direction from local topographic gradients and undulations in the longitudinal profiles. We also observe that the width of first order tributaries is one to two orders of magnitude larger than in river systems, and remarkably constant downstream. These distinctive aspects of tunnel valley morphology are similar among the different locations characterized in the study. Furthermore, our findings are consistent with expectations of flow driven by gradients in effective water pressure related to variations in ice thickness. Our field and remote sensing observations provide a rigorous way to distinguish tunnel and river valleys in local and regional topography data that revisits well-established field identification guidelines. Distinguishing river and tunnel valleys in topographic data is critical for understanding the emergence, geometry and extent of channelized subglacial drainage systems. The final aim of this study is to facilitate the identification of tunnel valley networks throughout the globe by using remote sensing techniques, which will improve the detection of these systems and help to build understanding of the mechanics of subglacial channelized drainage.
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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 | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 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".