North Atlantic response to the above‐normal export of sea ice from the Arctic
Bibliographic record
Abstract
The response of the thermohaline circulation (THC), as well as the freshwater and heat budgets of the northern North Atlantic, to above‐normal sea ice export from the Arctic is examined using a global model. The model is not constrained by either open boundary conditions or prescribed atmospheric air temperature and humidity. Two sets of experiments are presented: the transient and the persistent above‐normal ice export. In the transient case, ice export is increased by a factor of 2 for 1–5 years. Our century‐long simulations do not support the notion that the simulated climate may switch to a new quasi‐equilibrium under such perturbations. Rather, in response to the transient positive ice export anomalies the overturning circulation first slows down but then almost completely recovers 15–20 years after the perturbation is removed. However, the budgets of freshwater and heat continue to evolve for up to 40 years in this case. When the simulated North Atlantic freshening reaches a magnitude comparable to that during the Great Salinity Anomaly (GSA), the strength of overturning and heat transport from subtropical to subpolar North Atlantic reduce by no more then 5%. We show that in order to generate a previously reported decrease of overturning and heat transport of as much as 20% the doubled ice export must be sustained for at least 5 years. This would result in a North Atlantic freshening more than 3 times larger than that estimated for the GSA event. In the case of a persistent above‐normal export of sea ice from the Arctic the THC also does not collapse, at least within the range of the ice export increase (1.5–3 times) used here. Rather, after about 15–20 years the overturning begins to recover. The stability of the overturning to the persistent above‐normal export of sea ice from the Arctic appears to be due to two processes operating on a decadal timescale of 15–20 years. First, the internal (to the coupled system) redistribution of freshwater between the Arctic and North Atlantic, associated with the enhanced export of sea ice, makes the North Atlantic fresher and Arctic Ocean saltier. This, if persistent, decreases the amount of freshwater leaving the Arctic toward the North Atlantic in a liquid form. Second, because the overturning circulation does not collapse, the freshwater anomaly propagates downward within the region of deep water formation, removing the excess of buoyancy from the surface ocean. Also, the use of an active atmospheric component is important for stabilizing the overturning circulation.
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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".