Spatial and temporal reconstructions of surface and deepwater flow in the subtropical NW Atlantic at sharp climatic transitions
Notice bibliographique
Résumé
A suite of deep-marine sediment cores recovered from the Blake Outer Ridge (BOR) in the subtropical North West Atlantic (28-34 N, 75-71 W) provide material for centennial to millennial scale investigations of abyssal circulation and surface ocean conditions during selected intervals in the last 130 kyr. Particular focus is placed on reconstructing the position and strength of the Deep Western Boundary Current (DWBC) at a high temporal resolution. Palaeocurrent dynamics are reconstructed using the 'sortable silt' (10-63 urn terrigeneous fraction) mean grain size sedimentological proxy. Paired Mg/Ca and 8 () records from the planktonic foraminifera <italic>G. ruber</italic> (white) are used to reconstruct deglacial sea surface temperature (SSI) and salinity variations, while benthic 513C data from Cibicidoides spp. document the interchange of northern- and southern source deepwater (NSW/SSW) in the subtropical Atlantic. Comparison of Holocene sediments with modern physical hydrographic measurements reveals a DWBC high velocity core between 3,000-4,000 m water depth. A deep position for the DWBC core below 3,500 m was also observed during the peak of the last interglaciation, marine isotope stage (MIS) 5e. The benthic 5I3C during these interglacial intervals reveals little chemical stratification and a water column dominated by NSW. A shallow Labrador Sea Water (LSW)-sourced secondary fast flowing DWBC core is also apparent during the Holocene, however during MIS 5e palaeocurrent data at intermediate depths suggest a weaker and possibly shallower position for the LSW-sourced secondary DWBC limb. The last glacial maximum and Younger Dryas reconstructions show similar hydrographic regimes with nutrient-depleted, vigorously flowing NSW above 2,500 m consistent with intermediate water formation. Northern sourced intermediate water was first apparent in the records presented at 111 kyr BP and is suggested to have persisted throughout the last glacial. Benthic 5I3C data suggest the presence of a highly stratified water column with an increasing influence of SSW with depth. Coupled suborbital oscillations in DWBC flow variability and palaeo-hydrography persist throughout the records. There is evidence for a broad-scale divergence in flow speed changes in the deep subtropical North Atlantic, with the presence of a vigorous, but poorly ventilated SSW mass below 4,200 m water depth during cold episodes of the last deglaciation and LGM, when shallower palaeocurrent and geochemical data suggest that NSW was suppressed. This is consistent with the operation of a bipolar see-saw effect. This study suggests a hitherto unrecognised degree of linkage between oscillations in subtropical North Atlantic SST and DWBC flow. During the last deglaciation the SST record is dominated by the position/strength of the Gulf Stream, while the effects of tropical heat retention are restricted prior to Heinrich event 1. A combination of meridional overturning strength, meltwater inputs and hydrological changes control salinity variability.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,001 | 0,001 |
| 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 tête enseignante, 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 ».