| Titre | Thaw depth monitoring in the Mackenzie Valley, Northwest Territories |
| Auteur | Smith, S L; Duchesne, C |
| Source | 2017 Yellowknife Geoscience Forum, abstract and summary volume; Northwest Territories Geological Survey, Yellowknife Geoscience Forum Abstracts Volume 2017, 2017 p. 75 (Accès ouvert) |
| Liens | Online - En direct (complete
volume - volume complet, 1.69 MB)
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| Année | 2017 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20180068 |
| Éditeur | Commission géologique des Territoires du Nord-Ouest |
| Réunion | 45th Annual Yellowknife Geoscience Forum; Yellowknife, NT; CA; Novembre 14-16, 2017 |
| Document | publication en série |
| Lang. | anglais |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Province | Territoires du Nord-Ouest |
| SNRC | 95H; 95I; 95J; 95N; 95O; 96C; 96D; 96E; 96F; 96L; 106I; 106J; 106N; 106O; 106P; 107B; 107C |
| Lat/Long OENS | -136.0000 -120.0000 70.0000 61.0000 |
| Sujets | pergélisol; glace fossile; climat; instruments d'observation; Changement climatique; géologie de l'environnement; géologie des dépôts meubles/géomorphologie; Nature et environnement |
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| Programme | Pergélisols, Géosciences de changements climatiques |
| Résumé | (disponible en anglais seulement)
In permafrost regions, increases in thaw depth in response to a warming climate have considerable implications for landscape stability, infrastructure
integrity, drainage and ecosystems. In ice-rich terrain, increases in thaw depth can result in significant ground settlement due to melting of excess ice. This leads to a reduction of the thawed layer so that over time, active layer thickness (i.e.
thickness of the seasonally thawed layer) may change very little even though the lower boundary of the active layer continues to progress deeper into the ground.
Mechanical probing is often used to monitor active layer thickness but this method
does not consider changes in surface elevation over time and therefore does not provide an accurate picture of the loss of frozen ground that may occur in response to a warming climate. Thaw tubes however, do allow tracking of both thaw penetration,
relative to a fixed datum, and thaw settlement. Thaw tubes have been used, by the Geological Survey of Canada, throughout the Mackenzie Valley since the early 1990s as part of a permafrost monitoring program. Records up to 25 years long exist for
over 40 sites.
Analysis of thaw depths indicates that at sites located within ice-rich terrain, increases in thaw penetration (measured relative to original ground surface) over the last two decades can be as much as double the increase in active
layer thickness over the same period. For example, data from two sites in the Central Mackenzie Valley indicate that between 1993 and 2014 thaw penetration increased by 21-29 cm, a process which was accompanied by 12-15 cm of settlement. The active
layer thickness over this period, however, only increased by 10-12 cm. The loss of frozen ground over time, may therefore be considerably more than that indicated by the change in active layer thickness alone.
Data analysis from the active layer
monitoring network help describe relations between thaw penetration, settlement and ground conditions. These results can advance our understanding of changes in regional permafrost conditions. They can also contribute to better representation of
active layer processes in models and improved prediction of future permafrost conditions. |
| Résumé | (Résumé en langage clair et simple, non publié)
Dans les régions de pergélisol, l'augmentation de la profondeur du dégel en réponse à un réchauffement climatique a des répercussions
considérables sur la stabilité du paysage, l'intégrité de l'infrastructure, le drainage et les écosystèmes. L'information sera présentée sur la profondeur du dégel acquise à partir d'un vaste réseau de sites instrumentés dans la vallée du Mackenzie
(TN-O.). Les augmentations de la pénétration du dégel au cours de l'été seront résumées ainsi que les implications, y compris le tassement en surface et la perte de pergélisol. L'information fournie fait progresser notre compréhension des changements
dans les conditions du pergélisol régional et peut également contribuer à améliorer les modèles de prévision des futures conditions du pergélisol. |
| GEOSCAN ID | 308272 |
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