Evolution of Late Season Meltwater in Alpine and Arctic Glaciers: Sampling Strategies and Geochemical Observations
Notice bibliographique
Résumé
The presence, configuration, and efficiency of subglacial hydrologic systems has important implications for both glacial dynamics and the chemistry of meltwaters. These networks may exist in configurations that range from poorly connected and unable to accommodate large volumes of water to fast flowing and highly competent in different regions of the glacial bed, simultaneously or in different seasons. Direct study of the configuration and development of these networks is difficult as they are obscured by ice, yet network configuration is important in glaciological research as it controls the spatial distribution and residence time of subglacial water. Subglacial network efficiency, or the ability of the network to quickly evacuate water, controls under-ice water-rock interaction time affecting chemical weathering reactions and thus solute type and concentration expressed in proglacial meltwaters. Previous research into the configuration of subglacial hydrologic networks is limited in both temporal and spatial resolution, as field research generally occurs during summer months and is limited to more easily accessible glaciers. This dissertation investigates seasonal changes in subglacial hydrologic networks as evidenced by changing meltwater chemistry in late-summer at both a Canadian alpine glacier and an outlet glacier from the Greenland Ice Sheet. I undertook multi-month field campaigns at each location, during which I collected samples and made in situ measurements to correlate changes in chemical constituents carried within melt to changes in seasonality, improving understanding of this understudied time in seasonal glacial development. This dissertation uses laboratory experiments with sediment samples collected at glacial termini to evaluate the use of radon-222 (222Rn) activity concentrations, an intermediary in the uranium-238 (238U) decay chain, as a proxy for subglacial water residence time. These measurements are compared to in field 222Rn activity concentration measurements at sediment collection locations. Results show 222Rn activity concentration serves as a subglacial water residence time proxy but also reflects mineralogical sources of its parent isotope, radium-226 (226Ra). Field measurements of 222Rn activity concentrations as a proxy will be more robust and reliable if supported with laboratory leachate experiments with site-specific sediment samples, addressing likely lithological and sediment-size controls on 226Ra concentrations. I undertook a three-month field study of the alpine Athabasca Glacier in the Canadian Rockies in August through October, 2014. Both in situ and elemental chemistry of pro-glacial meltwaters are investigated relative to water discharge fluxes, air temperatures, and precipitation events to see how the subglacial network responds to climatic and glacial variables during the late summer-early fall. Different chemical weathering rates in response to changes in weather reveal shifts in network configuration, indicating the subglacial environment is dynamic and very responsive to climate conditions. Methods used at the Athabasca Glacier were then applied to Kiattuut Sermiat, an outlet glacier from the Greenland Ice Sheet to investigate possible differences in hydrology between alpine and outlet glaciers. Although environmental conditions are dissimilar between locations, the Kiattuut Sermiat results suggest the possible existence of an interannual subglacial drainage system capable of evacuating waters sourced from significantly further up into the Greenland Ice Sheet concurrent with a well-organized subglacial network configuration. This dissertation presents new measurements of glacial chemistry from an understudied period in seasonal glacial evolution, with interpretations unique to each glacier investigated.
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 | 0,000 | 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) | 0,000 | 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 ».