Investigating the role of extratropical cyclones in North Atlantic deep water formation
Bibliographic record
Abstract
The Atlantic Meridional Overturning Circulation (AMOC) is a vital mechanism of heat transport in the climate system, but it has been suggested that its strength will change in the coming decades. This strength depends in part on water mass transformations in the North Atlantic, and understanding the factors that contribute to this variability is crucial to predicting the future behaviour of the AMOC. In the Labrador and Nordic Seas, where deep convection occurs and replenishes the deep water masses of the AMOC, atmospheric forcing is a critical factor in the priming and initiation of convection. In particular, extratropical cyclones (ETCs) provide high-frequency forcing that can influence hydrographic properties in the upper water column. These effects can be studied by forcing an ocean model with atmospheric datasets that include such storms, and then analyzing the response of the ocean to them. This thesis will first present background information on the processes of deep convection and deep water formation in the North Atlantic, as well as discussing extratropical cyclones and the air-sea interactions associated with them. Details of the ocean model and atmospheric datasets used to perform this study will be described. ETC statistics are calculated to study seasonal and interannual patterns of storm characteristics. The results indicate that stronger cyclones tend to occur in the cold season, and that the maximum strength of ETCs on a year-to-year basis may correlate with the phase of the NAO. Various properties from the ocean model output are also examined as time series associated with individual cyclones that are detected in the atmospheric datasets. These time series are also averaged to calculate the mean ocean response to various categories of ETCs. We find that individual cyclones may change sea surface temperatures by up to 2°C, though the mean change was around 0.2°C. The density and depth of the mixed layer do increase in response to ETC passage, and these changes persist for at least a week post-cyclone. The depth of the mixed layer also tends to remain somewhat deeper than its pre-cyclone depth even after returning to equilibrium, suggesting that ETCs passing in succession may progressively deepen the mixed layer over time.
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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 | 0.000 | 0.000 |
| 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) | 0.001 | 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".