Nitrate record of the 2022 Mt. Logan ice core suggests highest elevation regions sensitive to atmospheric acidity
Bibliographic record
Abstract
Anthropogenic nitrogen oxide (NOx = NO + NO2) emissions have increased since the Industrial Revolution as a result of fossil fuel burning, contributing to increasing atmospheric acidity and changes to the oxidative capacity of the atmosphere. Oxidation of NOx leads to the formation of atmospheric nitrate both in the gas phase (HNO3(g)) and aerosol phase (p-NO3–), which may then be removed from the atmosphere via wet and dry deposition. Ice core records of nitrate may thus be used to infer past changes in atmospheric NOx concentrations and atmospheric acidity given high enough accumulation rates to prevent substantial post-depositional photolytic loss from the snowpack. Increasing trends innitrate concentrations over the 20th century have been observed in ice core records throughout the Northern Hemisphere including Greenland and the North Pacific. However, two ice cores (1980 NW Col and 2002 PR Col ice cores) retrieved from the summit plateau (5,334 m a.s.l.) of Mt. Logan, the second tallest mountain in North America located in the glaciated region of the St. Elias Mountains in southwest Yukon, revealed no long-term trend in acid chemistry. This lack of sensitivity to increasing atmospheric acidity was largely attributed to the high elevation of the site within the free troposphere and the efficient scrubbing of atmospheric pollutants during transit across the Pacific. Here, we present a nitrate record from the new 2022 Mt. Logan ice core since 1912 CE (~256 m depth). Reconstructed accumulation at the site is extremely high with an average rate of 2.97 m weq a-1 from 1912 to 2020, implying excellent preservation of volatile species coupled with low average temperatures (-26.9°C). The nitrate record suggests a statistically significant (p < 0.01) increasing trend since 1912 CE, in contrast to both the NW Col and PR Col records. The record agrees with other Northern Hemisphere ice core nitrate records including Summit (Greenland; r = 0.49, p < 0.01, 1912–2006), Begguya (Alaska; r = 0.44, p < 0.01, 1912–2012), and Eclipse (Yukon; r = 0.30, p < 0.01, 1912–2001). These results indicate that the highest elevation regions of the North Pacific, such as Mt. Logan, are indeed sensitive to anthropogenic NOx emissions, with ice cores providing rare insight into mid-tropospheric acid chemistry where preservation is adequate.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 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) | 0.001 | 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".