|Title||Disturbed permafrost environments: research opportunities|
|Author||Morse, P D; Wolfe, S A|
|Source||Northwest Territories Geological Survey, Yellowknife Geoscience Forum Abstract and Summary Volume 2015, 2015 p. 71 (Open Access)|
|Links||Online - En ligne (complete volume, pdf, 1.98
|Alt Series||Earth Sciences Sector, Contribution Series 20150406|
|Publisher||Northwest Territories Geological Survey|
|Meeting||43rd Annual Yellowknife Geoscience Forum; Yellowknife, NT; CA; November 24-26, 2015|
|Media||paper; on-line; digital|
|File format||pdf (Adobe® Reader®)|
|Area||Tlicho Region; North Slave Region; Behchokö; Yellowknife|
|Lat/Long WENS||-118.0000 -114.0000 63.0000 62.0000|
|Subjects||environmental geology; surficial geology/geomorphology; hydrogeology; permafrost; ground ice; climate; sediments; clays; silts; peatlands; surface waters; mining; borrow pits; bedrock geology;
vegetation; hydrologic environment; groundwater regimes; flow regimes; meteorology; Great Slave Lowland High Boreal Ecoregion; climate change; permafrost degradation; infrastructures; road networks; road construction; terrain sensitivity;
environmental impact; forest fires; icings|
Geoscience, Land-based Infrastructure|
|Released||2015 11 01|
|Abstract||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.
|Summary||(Plain Language Summary, not published)|
We present three knowledge gaps with broad relevance where recent human and natural disturbances will affect previously impacted permafrost environments
in NWT. (1) New and abandoned Highway 3 alignments cross natural and disturbed terrain in a highly varied landscape with discontinuous permafrost. Compared to natural sites, the status of environmental changes (permafrost, hydrology, and vegetation)
at highway alignments are not well known, making the long-term fate and environmental impacts difficult to predict. (2) Permafrost degradation affecting ice-rich terrain will likely follow severe forest fires in 2014. The degree and rate of
permafrost recovery are unknown and require long-term consideration where infrastructure may be affected. (3) Icing development is a geohazard. To predict their development and to develop effective mitigation measures, the unknown physical mechanism
causing icing growth requires better understanding.