Meridional heat transport in the North Atlantic region: Effects of ocean and atmosphere grid resolutions
Bibliographic record
Abstract
The consequences of grid resolution refinement of both ocean and atmosphere components in and over the North Atlantic Ocean are examined in this study. The Flexible Ocean and Climate Infrastructure (FOCI) model is used to run three simulations carried out under constant 1950 forcing. Ocean and sea ice models run on the ORCA05.L46 grid; in two simulations, regional AGRIF grid refinement from 1/2˚ to 1/10˚ (VIKING10) is applied to the North Atlantic between 30˚ and ~80˚N. We also use two different atmospheric resolutions, Tco95.L91 (100km) and Tco319L137 (31 km) applied globally. The three combinations studied are: (1) coarse ocean and atmosphere, (2) refined ocean but coarse atmosphere, and (3) both components in the high-resolution configuration. Ocean grid refinement in regions of complex dynamics, such as the Gulf Stream and North Atlantic Current, is essential to capture mesoscale variabilities. Air-sea interaction and in particular surface heat fluxes only benefit from the explicit representation of mesoscale eddies, when also using the high-resolution atmosphere capturing a wider range of, for instance, the temperature distributions. We examine the ocean and atmospheric mean state changes over the North Atlantic and find significant changes: The Atlantic Meridional Overturning Circulation strengthens as we move to higher ocean and atmospheric resolution. Most parts of the North Atlantic Ocean surface become warmer and saltier in the high-resolution ocean configuration, but with the finer atmospheric grid, this warming reduces and transforms into a colder and fresher mean state. The surface cooling with increasing atmospheric resolution is a result of a reduced TOA imbalance. The mid-depth (500-1200m) ocean experiences strong cooling of more than 2˚C especially in the subtropics with the grid refinement in the ocean, a difference that is considerably weaker when also refining the atmosphere. The cooling in the subtropics has two reasons, a stronger gyre-gyre interaction mixing more subpolar water into the subtropical gyre and intensified deep mixing in the Labrador Sea (associated with a stronger overturning) in the high-resolution ocean compared to the coarser one. Meridional volume and heat transports in the subtropical North Atlantic exhibit significant differences of up to 2-2.5 Sv with the change in resolution, which also suggests an influence by model resolution in the ocean and the air-sea interaction processes. With a higher ocean resolution, the oceanic heat transport into the Arctic increases by 0.15 PW at 62°N, causing a reduction of Arctic sea ice. Increasing the atmospheric resolution causes an expansion of Arctic sea ice, consistent with the overall surface cooling, but also changes the distribution of sea-ice thickness with thicker ice north of Greenland and thinner ice toward Russia, consistent with observations. Overall, the changes in the mean state of the ocean and atmosphere, as well as the feedback processes involved, will be discussed in this presentation, which we hope also benefits other modelling groups.
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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 | 0.002 | 0.007 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 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".