A 10,000-year lake-sediment based reconstruction of precipitation isotope values in the Canadian Rocky Mountains
Notice bibliographique
Résumé
We present a 10,000-year carbonate oxygen isotope (δ 18 O) record from Shark Lake, Alberta, (50.8411°N, 115.3983°W; 1,857 m above sea level) that provides insight on past changes in precipitation seasonality, regional hydroclimate dynamics and atmospheric circulation. Shark Lake has a hydrologically open configuration, with water isotope values that mirror annual mean precipitation, and contains a continuous sediment sequence consisting largely of authigenic carbonate minerals precipitated from the water column. The sediment δ 18 O record exhibits a shift from lower to higher-than-average δ 18 O values from the middle to late Holocene circa 4,100 calendar years before present (yr BP). This transition generally aligns with hypothesized transformations in atmospheric circulation that ostensibly led to reduced winter precipitation in northwestern North America and heightened aridity in the southwest during the late Holocene. Monte Carlo cross-correlation analysis demonstrates that other precipitation δ 18 O records from the Pacific Northwest have a significant positive correlation with the Shark Lake record, in contrast with records from the southern Rocky Mountains and central/eastern North America, which have a negative correlation with the Shark Lake record and others from the Northwest. We apply the previously established strong relationship between atmospheric circulation associated with the Pacific North American Pattern (PNA) and precipitation isotope values across North America to explain the marked coherency in precipitation δ 18 O reconstructions. Collectively, the paleo-records suggest a middle to late Holocene transition in the mean state of atmospheric circulation over North America from one similar to the negative phase of the PNA to one comparable to the positive PNA phase, in response to non-linear changes in ocean-atmosphere circulation driven by ice sheet decay and insolation forcing. This shift had substantial impacts on the source and isotopic composition of air masses traversing the continent and their interplay with circulation from the Gulf of Mexico as well as the seasonal amount and distributions of precipitation. Our results underscore the need for additional isotope-enabled climate model simulations and additional δ 18 O records, especially from understudied regions across North America, for a comprehensive view of seasonal-scale hydroclimate variations and synoptic-scale atmospheric circulation pattern changes over the Holocene. • 10,000-year δ 18 O record from Shark Lake reveals past hydroclimate changes. • δ 18 O records from across North America exhibit strong, significant correlations. • Northwestern δ 18 O records are anticorrelated with those from central/eastern regions. • A shift from negative to positive PNA-like circulation occurred in the mid-Holocene. • Air mass source and the amount and seasonal distribution of precipitation were impacted.
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 | 0,004 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 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 ».