Statistics and characteristics of permafrost and ground-ice distribution in the Northern Hemisphere
Bibliographic record
Abstract
The recently published digital version of the International Permafrost Association (IPA) Circum-Arctic Map of Permafrost and Ground Ice Conditions (the IPA map), together with ancillary data sets of the global land cover characteristics data base and the Global Land One-kilometer Base Elevation data base, are used to investigate the distribution of permafrost and ground ice in the Northern Hemisphere. Our study indicates that permafrost underlies approximately 22.79×106 km2 or 23.9% of the exposed land area of the Northern Hemisphere. Permafrost extends from 26°N in the Himalayas to 84°N in northern Greenland. Approximately 70% of the permafrost is distributed between 45 and 67°N. Generally, permafrost with high ice content (>20% by volume) and relatively thick overburden cover (>5 to 10 m) is found at high latitudes, representing approximately 8.57% of the total permafrost area, or 2.02% of the exposed land area of the Northern Hemisphere. Permafrost with low ice content (<10% by volume with either thick or thin overburden cover) occurs mainly in mountainous regions and high plateaus, representing approximately 66.5% of the total permafrost area or 15.8% of the exposed land area. Approximately 62% of the permafrost of the Northern Hemisphere is found below 500 m a.s.l. and about 10% occurs above 3000 m a.s.l. Based on the IPA map categories, the estimated volume of ground ice in the Northern Hemisphere is between 5.63 and 15.12×103 km3, corresponding to ∼2–4 cm sea level equivalent. Based on alternative assumptions, the volume of ground ice may be between 11.37 and 36.55×103 km3, which corresponds to 3-10 cm sea-level equivalent.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.003 |
| 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) | 0.003 | 0.001 |
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".