Seasonal evolution of the subglacial drainage system within a High Arctic polythermal valley glacier, as revealed by dye-tracing studies
Bibliographic record
Abstract
Current knowledge concerning the impact of subglacial hydrology on the dynamics of polythermal glaciers is limited. Conventional wisdom suggests that subglacial hydrology has a negligible influence on surface patterns of ice dynamics in polar regions, due mainly to the presence of cold, impermeable surface ice layers which prevent large seasonal supraglacial meltwater inputs from reaching the bases of polythermal glaciers. However, recent research has suggested a) that subglacial hydrology exerts a major influence on ice dynamics throughout temperate glaciers, and b) that many Arctic glaciers may experience considerable subglacial water flow. During summer 2000, intensive field investigations were undertaken at John Evans Glacier, a polythermal valley glacier situated on Ellesmere Island in the Canadian High Arctic (79°40'N, 74°00'W) to i) characterise the subglacial hydrology of the glacier and determine the extent to which it evolved over the course of a melt season, and ii) establish whether variations in subglacial hydrology affected rates of glacier motion. Known quantities of fluorescent dye were periodically injected into the englacial system via moulins, and dye emergence was detected in a single stream emerging from the terminus 5 km downglacier. Early in the season (late June), dye returns were highly dispersed and dye velocities were low (~0.14 ms-1), implying that inefficient distributed drainage was taking place. Later in the season (late July), dye experienced little dispersion, and dye transit velocities reached 0.7 ms-1, suggesting that the subglacial drainage had evolved into an efficient, channelised system. Measurements of surface glacier motion across the lower glacier area were made on a two-daily basis throughout the field season and show highest horizontal velocities occurring in conjunction with vertical uplift of a number of motion stakes during late June. We hypothesise that the surface motion variations are directly related to the seasonal evolution of the subglacial drainage system. Given the sensitivity of Arctic regions to climate change and the resultant impetus to model such potential change, these conclusions suggest that the critical role of subglacial hydrology on ice dynamics in polar regions cannot be neglected.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".