Ice ages and interglacials: measurements, interpretation and models
Notice bibliographique
Résumé
The typical description of the past 800,000 years would be that the Earth has experienced about nine major periods of glaciation ("Ice Ages") spaced at various intervals ranging from 0.9 my to 1.1 my (see Fig. 8.23).This presupposes that Ice Ages are unusual departures from normalcy.Actually, it appears as if the natural state of the Earth during this period was an Ice Age, but there were about nine interruptions of the glacial state, during which the Arctic climate was much warmer for time periods of the order of 10,000 years or so.Each Ice Age required many tens of thousands of years to develop to its maximum state of glaciation.During the last glacial maximum, some 20,000 years ago, Canada and the northern USA were blanketed by huge ice sheets, up to 4 km in thickness.In addition, there was a large ice sheet covering Scandinavia that reached down into Northern Europe.The Antarctic ice sheet was somewhat more extensive than today.Local glaciations existed in mountainous regions of North America, Europe, South America and Africa, driving the tree line down by up to 700-800 m.The temperature of Greenland was lower by up to 20 °C, but the climate was probably only a few degrees colder than normal in the tropics.Conditions were very harsh 20,000 years ago at the last glacial maximum (LGM).These ice sheets tied up so much of the Earth's water that more than 150 m of ocean was removed.As a result, the shorelines of the continents moved outward by a considerable distance.The Beringia land bridge from Siberia to Alaska was created, allowing animals and humans to cross from one continent to the other.In the upper-mid latitudes, the climates were semi-arctic and the flora shifted to tundra.Humidity was reduced, and many lands dried out.At the LGM, the CO 2 concentration dropped below 200 ppm, and this combined with cold, led to plant starvation and desertification of marginal areas.The sharp temperature discontinuity at the edges of the ice sheets generated violent winds that swept up dust and dirt from dry regions, filling the atmosphere with dust.Dust deposited on the ice sheets preceded each termination of an Ice Age, allowing much greater solar absorption and the demise of the ice sheets.This last Ice Age began to wane around 17,000 years ago and dissipated through a series of gyrating climate oscillations, ending in a comparatively benign period that has lasted for the past *10,000 years, called the Holocene.
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) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 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) | 0,001 | 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 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 ».