| Titre | Disturbed permafrost environments: research opportunities |
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| Auteur | Morse, P D ;
Wolfe, S A |
| Source | Northwest Territories Geological Survey, Yellowknife Geoscience Forum Abstract and Summary Volume 2015, 2015 p. 71  Accès ouvert |
| Liens | Online - En ligne (complete volume, pdf, 1.98
MB)
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| Image |  |
| Année | 2015 |
| Séries alt. | Secteur des sciences de la Terre, Contribution externe 20150406 |
| Éditeur | Commission géologique des Territoires du Nord-Ouest |
| Réunion | 43rd Annual Yellowknife Geoscience Forum; Yellowknife, NT; CA; Novembre 24-26, 2015 |
| Document | publication en série |
| Lang. | anglais |
| Media | papier; en ligne; numérique |
| Formats | pdf (Adobe® Reader®) |
| Province | Territoires du Nord-Ouest |
| SNRC | 85J; 85K |
| Région | Tlicho Region; North Slave Region; Behchokö; Yellowknife |
| Lat/Long OENS | -118.0000 -114.0000 63.0000 62.0000 |
| Sujets | pergélisol; glace fossile; climat; sediments; argiles; silts; tourbières; eaux de surface; exploitation minière; ballastières; géologie du substratum rocheux; végétation; milieu hydrologique; régimes des
eaux souterraines; regimes d'écoulement; météorologie; Changement climatique; Infrastructure; Réseau routier; Construction routière; Impact sur l'environnement; Incendie de forêt; glaçages; géologie de l'environnement; géologie des dépôts
meubles/géomorphologie; hydrogéologie |
| Programme | Géosciences de changements climatiques Infrastructures terrestres |
| Diffusé | 2015 11 01 |
| Résumé | (disponible en anglais seulement)
We present three research areas from NWT, with broad reaching implications, where recent human and natural disturbances may affect previously impacted
permafrost environments, providing new opportunities for understanding.
The first is GNWT Highway 3, crossing the Great Slave Lowland High Boreal ecoregion from Behchoko to Yellowknife, as an example of road infrastructure that traverses a highly
heterogeneous landscape with discontinuous permafrost. Permafrost is widespread within undisturbed terrain underlain by fine-grained silty-clay sediments. Construction during the mid-1960s utilized locally available silt and clay excavated from
shallow borrow pits, the alignment preferentially crossed natural terrain including peatland and clay-rich terrain, largely avoiding water bodies. Recently (1999 to 2006) major realignments were made to maximize bedrock traverses with new embankments
constructed primarily of open graded, blast-rock fill, and to minimize crossing over thaw-sensitive permafrost and thus embankment settlement. However, newly aligned sections extend across natural terrain that includes ponds, peatland, clay-rich
terrain, and disturbed terrain including the former highway and associated borrow pits in addition to bedrock. Compared with contemporary conditions at natural sites, the status of environmental changes (permafrost, hydrology, and vegetation) at
abandoned and new highway alignments are not well documented. Thus the long-term recovery of abandoned alignments and fate and environmental impacts of the new alignments are difficult to predict.
The second is the influence of fire on permafrost
in previously disturbed areas and infrastructure. Following the forest fires of 2014, preliminary results indicate that fire-induced permafrost degradation is likely to be extensive, and may occur in ice-rich terrain. Permafrost degradation affects
hydrological conditions and pathways, and likely the effectiveness of infrastructure. The degree and rate of permafrost recovery are unknown and require long-term consideration.
The last concerns icing development. Icings impinge on the safe
operation and management of infrastructure, either directly through accumulation of ice, or indirectly by diversion of flood water. In the North Slave region our research indicates icing distribution and dynamics are related to permafrost and
geology. Icing development is linked to precipitation conditions the preceding autumn, but overflow events result from winter air temperature conditions. Others have linked overflow events with increased ground water pressure related to air
temperature change, but the physical mechanism is unknown. Better understanding of these processes may be used to develop effective prevention or mitigation measures.
Knowledge gaps identified in these areas may lead to opportunities for future
research directions. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Nous présentons trois cas ayant des lacunes en matière de connaissances où des perturbations récentes au pergélisol, causées par des effets
humains et naturels, affecteront des environnements précédemment perturbés dans les Territoires du Nord-Ouest. (1) Les tracés routiers actuel et désaffecté de l'autoroute 3 traversent des milieux naturels et perturbés présentant un terrain hétérogène
de pergélisol discontinu. Comparativement aux sites naturels, l'état des changements environnementaux (le pergélisol, l'hydrologie et la végétation) des tracés routiers est méconnu, rendant difficile à prédire le sort à long terme et les impacts
environnementaux. (2) Une dégradation du pergélisol affectant des milieux riche en glace suivra probablement les graves incendies de forêt qui ont eu lieu en 2014. Le degré et le taux de récupération potentiel du pergélisol à ce genre de site n'est
pas bien connu et nécessitent un examen à long terme là où l'infrastructure peut être affectée. (3) Le développement de glaçages est un géorisque. L'approfondissement des connaissances sur les processus physiques provoquant la croissance des glaçages
permettra de mieux prédire leur développement et d'élaborer des mesures d'atténuation efficaces. |
| GEOSCAN ID | 297528 |
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