The North Atlantic mean state in mesoscale eddy-resolving coupled models: a multimodel study
Bibliographic record
Abstract
Abstract. Ocean mesoscale structures, which are parameterized in models with standard resolutions on the order of 1° or coarser, have an impact at larger scales, affecting the ocean mean state and circulation. Here we study the effects of increasing model ocean resolution to mesoscale eddy-resolving scales on the representation of the North Atlantic mean state, by comparing an ensemble of four HighResMIP coupled historical simulations with nominal ocean resolutions of at least 1/10° – corresponding to the models CESM1-CAM5-SE-HR, EC-Earth3P-VHR, HadGEM3-GC31-HH, and MPI-ESM1-2-ER – to a baseline of 39 Coupled Model Intercomparison Project phase 6 (CMIP6) simulations at coarser resolution. We find an improved representation of the Gulf Stream (GS) structure and position in the mesoscale-resolving ensemble, which leads to significantly reduced surface temperature and salinity biases north of Cape Hatteras (NCH). While higher resolution lessens the mean cold–fresh surface biases in the Central North Atlantic (CNA), the improvement is not statistically significant, as some mesoscale-resolving models still present an overly weak North Atlantic Current (NAC). Important differences also occur in the Labrador (LS) and western Irminger Seas (IS). Although the mesoscale-resolving ensemble exhibits larger warm and salty local biases at the surface compared to the low-resolution one, its full-depth profile reveals significantly weaker vertical stratification in the area, closer to observations. This reduced stratification in the high-resolution ensemble is consistent with the presence of stronger (although not significantly stronger) deep water convection in the region. While in the LS the wide range of MLD observational estimates makes model assessment challenging, in the Nordic Seas and along the East Greenland Current, convection in the high-resolution model ensemble is in better agreement with observational records, compared to the low-resolution ensemble. Another clear improvement in the mesoscale-resolving ensemble is found for the representation of the Atlantic overturning in depth-space, which is significantly closer to RAPID observations at 26.5° N than in the low-resolution counterpart; however, it still remains too shallow compared to observations and reanalyses. The subpolar gyre (SPG), as characterized by the barotropic streamfunction, is not significantly stronger in the higher resolution ensemble, although it presents a narrower and locally stronger boundary current.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".