Subseafloor Temperature Variations Influenced by Variations in Bottom Water Temperature and Pressure: New High Resolution Observations and Implications
Bibliographic record
Abstract
Abstract A new instrument developed for monitoring acceleration, tilt, and pressure at the ocean floor also measures sediment temperature 1 m below the seafloor. Four deployments have been completed and connected to the Ocean Networks Canada cabled observatory, one on the inner Cascadia accretionary prism, two on the outer prism, and one on the sedimented eastern flank of the Juan de Fuca Ridge. Relative amplitudes and phases of temperature variations measured at the seafloor and in the sediment at periods greater than roughly 1 week constrain the thermal diffusivity of the upper meter of subseafloor sediment to be 4 × 10−7 m2/s. Clear ±0.1‐mK amplitude tidal sediment temperature variations are also resolved. These are too large and regular to be the consequence of downward thermal diffusion from the seafloor and too large to be the consequence of fluid migration driven along the sediment geotherm by poroelastic response to tidal loading. The variations are closely correlated with tidal pressure variations, however, and we infer that these temperature signals reflect adiabatic heating and cooling. The lapse rates inferred from the observations at two of the sites are close to the values for seawater but significantly higher than predicted for a mixture that includes sediment grains. The values observed by both instruments at the outer prism site, located near methane‐bearing‐fluid springs, are particularly high, 20% higher than predicted for a sediment‐seawater mixture. This discrepancy could be reconciled if free gas or methane hydrate were present within the pore volume.
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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 | 0.001 | 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".