Isopycnal Mixing in the North Atlantic Oxygen Minimum Zone Revealed by RAFOS Floats
Bibliographic record
Abstract
Abstract The Eastern Tropical North Atlantic Oxygen Minimum Zone (OMZ) is a biogeochemically important area. The low oxygen in this region is thought to be maintained by a balance between the slow mixing supply of O 2 and its removal by respiration. We use data from 90 isopycnal RAFOS floats to characterize the mixing coefficients responsible for the supply of oxygen to the region. One group was ballasted to drift on the isopycnal where oxygen is at its minimum and the other about 300 m deeper. Using the record of the float positions at each 6‐hr interval, we calculate the relative dispersion of pairs of floats. The time derivative of this dispersion provides a diffusivity coefficient that captures the net effect of eddy‐driven mixing along each isopycnal. Float pairs deployed at shared locations but across the two target densities reveal that the influence of vertically sheared currents is to accelerate the dispersion by 10–15% relative to true isopycnal dispersion. Relative dispersion of the floats in the OMZ area obeyed the canonical four‐thirds power scaling, representative of two‐dimensional turbulence. At the length scale of the maximum energy‐containing eddy (approximately 100 km), the effective diffusivity is 1,400±500 m 2 /s in the zonal direction and 800±300 m 2 /s in the meridional. Within the uncertainty, the diffusivities on the two isopycnals are indistinguishable from one another. An idealized model suggests that meridional mixing across the large‐scale O 2 gradient is the leading supply term of oxygen to the OMZ.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 teacher head, 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".