Surface velocity and ice thickness of the Müller ice cap, Axel Heiberg Island
Notice bibliographique
Résumé
Muller ice cap is situated on Axel Heiberg Island in Arctic Canada. It is characterised by a mountanious region separating the ice cap in the east from the outlet glaciers in the west. Research has taken place on the outlet glaciers of the ice cap since 1959, but only limited research has been conducted on the main ice cap, and no full depth ice cores have ever been drilled. The interesting location of the ice cap facing the Arctic Ocean, the chance of finding ice dating back to the Innuitian Ice Sheet, and the fact that no full depth ice cores have been drilled, makes it an obvious place to do so. In order to achieve a long and undisturbed chronology of the ice core, one needs to find a location for the drilling site, where there is a great ice thickness, low surface velocity and little melt. In this project the aim is to make surface velocity maps of the ice cap and estimate the ice thickness to be able to come up with suggestions of possible drill site areas.Surface velocities are calculated using feature tracking of optical satellite images from the Landsat satellites in the period of 2004-2019. A median velocity map of all Landsat 8 velocity maps is used as validation in modelling the ice thickness and in the investigation of possible drill site areas.To estimate the ice thickness various methods are used and are being compared to the ice thickness measured by Operation IceBridge. The first method is an iterative inverse method where the ice sheet model PISM works as a forward model. The model is found to work rather well on the ice cap, with a root mean squared error (RMS) of 138.9 m, but overestimates the ice thickness on the outlet glaciers. The second model uses a simple inversion of the shallow ice approximation. It overestimates the ice thickness in areas with low surface slope, but has a RMS of 131.4 m on the ice cap. The third and and fourth models uses Monte Carlo sampling methods of the shallow ice approximation without and with sliding, respectively. The latter uses an initial ice thickness guess, and the modelled ice thickness was proofed not to differ from that initial guess at all. The RMSs on the icecap of the two models were found to be 132.1 m and 129.9 m, respectively. Finally, the fifth model uses the PISM setup but with an initial geometry defined by the SIA inversion. The RMS on the ice cap is found to be 135.4 m.Based on the median Landsat 8 surface velocity map, the modelled ice thicknesses and the surface elevation from the Arctic Digital Elevation Model, a map of suggested drill site areas is made. The site which fulfilled the criteria the most is located at 526629 m easting and 8866463 m northing in UTM zone 15N. In this site the surface velocity is 1.2 m yr−1, the surface elevation is 1804 m and the modelled ice thicknesses varies from 535-579 m. The melt in this area is estimated to be less than 20 melt days per year based on the backscatter from Sentinel-1.
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 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 | 0,000 |
| 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) | 0,002 | 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 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 ».