Response of the northern North Atlantic and Arctic oceans to a sudden change of the North Atlantic Oscillation
Bibliographic record
Abstract
The influence of a switch from a long‐time high North Atlantic Oscillation (NAO+) state to an enduring NAO− situation is investigated with a coupled sea ice–ocean model. We compare the response to a sustained shift to NAO− conditions with that to a short‐lived transition to NAO− and back to NAO+ forcing. Observed changes in sea ice and oceanic variables between high and low NAO states are well captured in the model response. The ocean circulation adjustment includes a fast barotropic anomaly, accompanied by an enhancement of the meridional overturning and the northward heat transport at 48°N. The slow response contains a substantial decrease of the northward heat transport, which is caused by a reduction of the transport of subpolar and subtropical gyres. After a delay of around 2 years, the oceanic heat transport reacts to counteract the meridional temperature gradient imposed by the surface forcing. The propagation time of baroclinic Rossby waves is irrelevant for the delay between the forcing and the oceanic response. Rather, the strength of the subpolar gyres is determined by the rapid spin‐up of a topographic Sverdrup circulation and the subsequent slower changes through the JEBAR (Joint Effect of Baroclinicity And Relief). In an experiment where only the wind stress is changed to NAO− conditions, the adjustment is dampened strongly by the NAO+ thermohaline forcing. The gyres decrease slower than in the NAO− case. Comparison with an experiment where only the wind stress is changed to NAO− conditions indicates that the thermohaline forcing is most important. The heat fluxes counteract the wind stress forcing such that the meridional overturning and the northward heat transport decrease only slightly compared to the control run.
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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 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".