Bibliographic record
Abstract
Methane (CH 4 ) is a trace gas playing an important role in the global carbon cycles and climate change as a greenhouse gas.Recent Arctic warming and decreasing sea-ice could promote release of CH 4 from sediment on the continental shelf and microbes, and provide a strong positive climate feedback.However, dynamics of dissolved CH 4 in the Arctic Ocean are still uncertain, especially in the western part (Bering Strait, Chukchi Sea and Canada Basin).Therefore, this thesis describes the horizontal and vertical distributions of concentration and stable carbon isotope ratio (δ 13 C value) of CH 4 in the western Arctic Ocean.Surface layer samples analyzed by this study were supersaturated with CH 4 in comparison to the atmosphere.Furthermore, the concentrations in 2013 were 2-3 times higher than in 2012.This reason might be considered as vertical transportation of CH 4 from bottom layer to surface layer due to weaker stratification by freshwater.In coastal shelf area in 2012, concentrations in bottom layer were higher (up to 55.9 nmol kg -1 ), whereas δ 13 C values were lower (down to -63.8‰).This might indicate that CH 4 in bottom layer was produced mainly by organic matter degradation in seafloor sediment via methanogen.On the other hands, gradients of concentration and δ 13 C value of dissolved CH 4 were not found in 2013.This fact supported that effect by vertical mixing were stronger in 2013.At deeper stations in the Canada Basin (seafloor > 300 m depth) in 2012, the maxima of CH 4 concentration were detected at depths of 10-50 m and 100-200 m, although δ 13 C values were lowest at 50 m depth.The shallower CH 4 maximum coincided with the DO maximum, suggesting CH 4 production by plankton activity or sinking particles.The deeper CH 4 maximum corresponded to the nutrient maximum, suggesting horizontal advection of shelf water from the coastal shelf area.In fixed station observation in 2013, vertical mixing at windy condition produced the highest CH 4 concentration in surface layer (17.2 nmol kg -1 with δ 13 C = -52.9‰),which suggested vertically transportation of CH4 from bottom of mixed layer to surface layer.From the results, the dynamic variation of dissolved CH 4 in the western Arctic Ocean in summer 2012 and 2013 with area, depth and years were carefully studied and its mechanism was evaluated quantitatively.
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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 | 0.002 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.012 | 0.012 |
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".