Climatic variations and societies in Northwest Alaska (11th-13th centuries CE) : contributions of dendrochronological, dendroclimatic and dendroisotopic approaches
Notice bibliographique
Résumé
At the onset of the 2nd millennium CE, during the Medieval Climate Anomaly [MCA] (10th-13th centuries) and the transition to the Little Ice Age [LIA] (13th-15th centuries), the Thule culture (1200-1800 CE), directly ancestral to the Iñupiaq culture in northwest Alaska, originated in the Birnirk and Punuk cultures in the Bering Strait region. Despite extensive archaeological research since the 1920s, the spatio- temporal dynamics of these cultures remain poorly understood in northwestern Alaska. The scarcity of local climatic and environmental indicators and their low resolution, both in time and space, limit our understanding of the complex human-environment interactions at this pivotal period in the emergence of Inuit culture. The exceptional preservation of Birnirk and Thule architectural wood remains along northern coastal Alaska provides an ideal context for high-resolution dendroarchaeological studies (analysis of annual growth rings in archaeological wood). Combining conventional dendrochronology and dendroclimatology with innovative methods (δ18O dating, 14C wiggle-matching, carbon δ13C and oxygen δ18O isotope dendroclimatology), I analyzed 284 architectural timbers (Picea glauca) from six sites of northern and northwestern Alaska. The aim was to refine the chronological and climatic framework of cultural transformations in the early 2nd millennium CE in the region. By constructing annual and local climatic sequences, my doctoral work sought to reconstruct the climatic variations of the MCA and the transition to the LIA (amplitudes, frequencies, rhythm of variations) and discuss their effects on the environment in which the Birnirk, Punuk and Thule groups developed. Conventional dendrochronological analyses allowed building mean sequences (composed of several wood samples) and strengthening the network of dendrochronological sequences contributing to the millennial chronology of northwest Alaska. For the 10-11th centuries, the number of samples contributing to the chronology was multiplied by four. Variations in ring widths in this chronology are partly linked to a summer temperature index that documents low-frequency Picea glauca growth trends over the last millennium. Two isotopic chronologies δ13C and δ18O were built for the periods 1945 to 2002 and 935 to 1157 CE from six modern driftwood and five archaeological wood samples from Cape Espenberg. The δ18O chronology allowed for the reconstruction of a standardized precipitation and evapotranspiration index (SPEI4) for the month of July from 1042 to 1123 CE. This reconstruction indicates wetter conditions during the ACM with their gradual drying out from moderately wet to normal, neither wet nor dry. A wiggle-matching procedure (14C dating and Bayesian statistics) placed in calendar time 22 wood remains that conventional dendrochronology could not date. The δ18O dating approach, made possible by the newly built δ18O chronology, now a reference for northwest Alaska, provided encouraging results, but stressed out the necessity to further develop the isotopic chronology and strengthen it with a larger number of trees. These new data hold great potential for contextualizing the cultural dynamics of ancient Inuit societies in their environment at annual or decadal temporal resolution, analyzing the effects of local climate variations on resource availability and subsistence strategies, and improving our understanding of the socio-environmental dynamics at a time of major cultural transformation.
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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 | 0,002 | 0,002 |
| Études des sciences et des technologies | 0,001 | 0,001 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 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 ».