The ablation zone in northeast Greenland: ice types, albedos and impurities
Bibliographic record
Abstract
Abstract Ice types, albedos and impurity content are characterized for the ablation zone of the Greenland ice sheet in Kronprinz Christians Land (80° N, 24° W). Along this ice margin the width of the ablation zone is only about 8 km. The emergence and melting of old ice in the ablation zone creates a surface layer of dust that was originally deposited with snowfall high on the ice sheet. This debris cover is augmented by locally derived wind-blown sediment. Subsequently, the surface dust particles often aggregate together to form centimetre-scale clumps that melt into the ice, creating cryoconite holes. The debris in the cryoconite holes becomes hidden from sunlight, raising the area-averaged albedo relative to surfaces with uniform debris cover. Spectral and broadband albedos were obtained for snow, ice hummocks, debris-covered ice, cryoconite-studded ice and barren tundra surfaces. Broadband ice albedos varied from 0.2 (for ice with heavy loading of uniform debris) to 0.6 (for ice hummocks with cryoconite holes). The cryoconite material itself has albedo 0.1 when wet. Areal distribution of the major surface types was estimated visually from a transect video as a function of distance from the ice edge (330 m a.s.l.). Ablation rates were measured along a transect from the ice margin to the slush zone 8 km from the margin (550 m a.s.l.), traversing both Pleistocene and Holocene ice. Ablation rates in early August averaged 2 cm d−1. Impurity concentrations were typically 4.3 mg L−1 in the subsurface ice. Surface concentrations were about 16 g m−2 on surfaces with low impurity loading, and heavily loaded surfaces had concentrations as high as 1.4 kg m−2. The mineralogical composition of the cryoconite material is comparable with that of the surrounding soils and with dust on a snowdrift in front of the ice margin, implying that much of the material is derived from local sources. A fine mode (clay) is present in the oldest ice but not in the nearby soil, suggesting that its origin is from wind deposition during Pleistocene glaciation.
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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".