Pathways and variability of the circulation in the subpolar eastern North Atlantic studied with inverted echo sounders and model data
Notice bibliographique
Résumé
The North Atlantic Current (NAC) as part of the Atlantic Meridional Overturning Circulation (AMOC) is the major pathway for warm and saline water from the subtropics into the subpolar North Atlantic. Due to buoyancy loss along its flow path and subsequent deep water formation, it connects the upper warm limb of the AMOC with the deeper cold limb. Associated volume fluxes and their variability are thus of great interest, especially in the context of climate change. The main branch of the NAC and related transports are widely studied. The NAC crosses 47°/48°N in the western North Atlantic and further north the Mid-Atlantic Ridge (MAR) before entering the eastern subpolar basin where it partly feeds the Subpolar Gyre or flows into the Nordic Seas. To quantify the meridional exchange of water between the subtropical and subpolar regime in the interior eastern North Atlantic where studies are scarce, in this work, long-term (1993 to 2017) transport time series were calculated by combining data from inverted echo sounders taken in 2016 and 2017 with satellite altimetry. The results obtained from observational data are complemented with transport time series calculated from high resolution model output of the ANHA12 configuration of the NEMO model and with the analysis of particle trajectories calculated from the Lagrangian model ARIANE. The observational data reveal an additional more direct pathway from the south across 47°/48°N into the subpolar eastern North Atlantic with a mean northward transport of +9.1 Sv ± 0.8 Sv contributing about 22% to the total inflow of +41.4 Sv into the eastern basin. The meridional transport of this pathway is significantly anticorrelated to the transport across the MAR (R = −0.7), damping the interannual variability of the total inflow into the subpolar eastern North Atlantic. Moreover, for the meridional transport in the interior eastern basin, a positive trend of +2.0 Sv ± 1.5 Sv per decade is found, partly balancing the negative decadal trend of −6.0 Sv ± 5.7 Sv observed for the interior western basin. The mean transport imbalance at the 47°/48°N transect between Newfoundland and 15°W was found to be −2.2 Sv which is likely to be compensated by the flow east of 15°W. In the model, the overall circulation pattern in the subpolar North Atlantic as well as the main regions for water mass transformation are very similar to what is found from observations. However, also substantial differences between the model and observations were found such as a surplus northward flow across 47°/48°N in the western basin, a weaker coupling between the western and eastern basin, and a smaller total inflow into the eastern subpolar North Atlantic of +24.2 Sv. Moreover, the analysis of particle trajectories reveals that about 60% of the water at 47°/48°N and the MAR originates in the subtropics and about 11% flows into the Nordic Seas.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».