Difference between revisions of "Scotty Creek, NWT Canada, 1990s -"
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== Location and Scale ==
== Location and Scale ==
Revision as of 11:45, 8 June 2019
Location and Scale
The Scotty Creek basin is located in the lower Liard River valley, approximately 50 km south of Fort Simpson, Northwest Territories, Canada. Scotty Creek is located in the continental high boreal and sporadic discontinuous permafrost zones and drains a 152 km2 area comprised of permafrost-cored peat plateaus and extensive thermokarst features including collapse scar bogs and fens, particularly in the headwaters of the basin. Given that the circumpolar region of the Northern Hemisphere is experiencing more rapid warming than other regions globally (Richter-Menge et al., 2017), permafrost is rapidly thawing, catalyzing the transition of the landscape from permafrost-dominated forests to treeless wetlands. This landscape transition has significant implications for the availability and sustainability of freshwater resources in this region. Therefore, the controls on permafrost thaw-induced landscape change and the hydrological implications of such change have been the focus of long-term, intensive research in the Scotty Creek basin.
Mid 1990s to present.
Scotty Creek has a continental climate with short, dry summers and long, cold winters. Annual air temperature at Fort Simpson (1981-2010) averages -2.8 ˚C, with a mean January temperature of -24.2 ˚C and a mean July temperature of 17.4 ˚C. Over recent decades, climate in this area has warmed twice the rate of the global average (Quinton et al., 2019). From 1950 to 2015 mean annual air temperature has increased by 2.5 ˚C, with the most pronounced increase of 4.5 ˚C in winter.
Annual precipitation (1981-2010) averages 390 mm, with 149 mm (38%) falling in the form of snow, and has remained relatively stable over the past 50 years (Quinton et al., 2019). Snowmelt typically begins in the second half of March and continues throughout most of April and early May.
Average annual basin runoff is 149 mm. Hayashi et al (2004) used chloride mass balance computations to estimate average evapotranspiration of 280 to 300 mm per year. Snowmelt water contributes to less than half of the basin discharge during the spring freshet, indicating that a large amount of water must be stored over winter. The total amount of water stored over the winter in the basin is estimated to be 140 to 240 mm (Hayashi et al., 2004).
Geology and Soils
The subsurface characteristics of Scotty Creek are typical of the continental high boreal wetland region, with a nearly continuous cover of Sphagnum peat (with a depth range of 2 m to 8 m) overlying a thick clay to silt-clay glacial till deposit of low permeability.
The soil profile of plateaus at Scotty Creek contain a relatively thin (~0.1-0.2 m) upper, lightly decomposed layer, overlying a darker layer in a more advanced state of decomposition. With increasing depth, the bulk density increases, while the porosity and average pore diameter decrease. The permafrost beneath the plateaus is protected by the thermally insulating overlying peat, a common feature of the discontinuous and sporadic permafrost zones in high boreal and subarctic regions throughout the circumpolar north. As such, permafrost is largely confined to these peat plateaus, while the surrounding terrain of collapsed wetlands and channel fens is permafrost-free.
In areas of thawing discontinuous permafrost, the active layer (that freezes and thaws annually) may not completely re-freeze during the winter months, resulting in the formation of a shallow talik (layer of perennially unfrozen ground in permafrost areas) between the overlying active layer and the underlying permafrost. The widespread occurrence of taliks has been found beneath the active layer on plateaus. Some taliks are isolated in depressions of the permafrost table whereas others extend across plateaus hydrologically connecting the wetlands on either side of them. Connon et al. (2018) found that the development of a talik is a “tipping point” that greatly accelerates permafrost thaw, as it reduces heat loss from the underlying permafrost during the winter while introducing a second thawing front to the overlying active layer. Permafrost beneath taliks was found to thaw 5 times faster than areas without a talik.
The mosaicked landscape of the Scotty Creek watershed is comprised of forested permafrost-cored peat plateaus, channel fens, collapsed wetlands, and small lakes. In more recent publications, the term ‘flat bog’ was replaced with ‘collapse scar bog’ to more accurately reflect their formation and hydrology. The forested peat plateaus underlain by permafrost are 1-2 m higher in elevation than surrounding land cover features. The collapsed wetlands result from thermokarst erosion, and are categorized as either isolated or connected. Isolated collapsed wetlands occur within peat plateaus, and are hydrologically isolated from channel fens. Connected collapsed wetlands are hydrologically connected to channel fens. The plateaus function to generate runoff, whereas collapsed wetlands primarily contribute to water storage and channel fens act as networks of drainage.
Linear disturbances, such as winter roads and seismic lines (introduced between 1942 and 1985) are the most widely occurring types of anthropogenic disturbances at Scotty Creek. The density of such disturbances is 7 times greater than the density of the drainage network of channel fens and open channels in the basin area. Where the linear disturbances traverse plateaus the tree canopy was felled and the permafrost beneath has thawed, producing a grid of permafrost-degraded corridors, which allow isolated wetlands to drain and hydrological connections among collapsed wetlands, fens, and plateaus to form bypassing typical drainage channels and facilitating more direct and efficient flowpaths.
Vegetation / Land Use
Mature plateaus support shrubs and trees with the ground cover composed of lichens and mosses. Plateaus are dominated by an overstory of black spruce (Picea mariana) trees, with an understory of ericaceous shrubs (e.g. Rhododendron groenlandicum), lichens (Cladonia spp.), and mosses (Sphagnum spp.). Trees are typically small and sparse, with short stunted branches. Channel fens are dominated by sedges (Carex and Eriophorum spp.) with individual tamarack (Larix laricina) and birch (Betula glandulosa) trees scattered throughout the fens. Collapsed wetlands are vegetated by ericaceous shrubs such as leatherleaf (Chamaedaphne calyculata), bog rosemary (Andromeda polifolia), and small cranberry (Vaccinium oxycoccos).
Due to climate warming and consequential permafrost thaw, land cover at Scotty Creek is among the most rapidly changing on the planet. Thawing permafrost along the edges of forested plateaus often results in ground surface subsidence leading to the development of ‘drunken forests’. Recent field studies at Scotty Creek have identified the growing presence of “treed wetlands”, which sheds light on how treeless wetlands can transition back to forest.
Dr. William (Bill) Quinton is the Director of the Scotty Creek Research Station (SCRS). He is also Director of the Cold Regions Research Centre at Wilfrid Laurier University, where he was appointed as a Canada Research Chair in Cold Regions Hydrology (August, 2005). Quinton has worked in the Northwest Territories since 1987, and in the Fort Simpson region since 1999. Also a founding member of the Laurier-GNWT Partnership Agreement (http://nwtwlu.com/), he enjoys a long-standing working relationship with the Dehcho First Nations, Liidlii Kue First Nation and Jean Marie River First Nation (http://jmrfn.com/), and other Indigenous communities.
At the time field studies began at Scotty Creek, the hydrological function of such low-relief, peatland-dominated zones of discontinuous permafrost was poorly understood. The first gauging station was installed at Scotty Creek in 1996, followed by the establishment of the SCRS basecamp. Over the years, infrastructure at the SCRS was expanded and the following equipment were installed in various land-cover features: water level recorders, ground temperature sensors, hydrometric sensors, ground thaw surveys, snow courses for annual snow surveys, climate stations, soil pits, wells, flux towers, deep thermistor profiles, and experimental thermosyphons along seismic lines. Field-based studies over this period formed the basis of new conceptual models, which in turn shaped the development of numerical simulations of the hydrological processes for this environment (Quinton et al., 2019). Field and modelling studies have generated new insights into the thermal and physical mechanisms governing the flux and storage of water in the wetland-dominated regions of the discontinuous permafrost zone, that characterises much of the Canadian and circumpolar subarctic. Research at Scotty Creek has coincided with a period of unprecedented climate warming, permafrost thaw, and resulting land cover transformations including the expansion of wetland areas and loss of forests.
Given the region’s rapidly warming climate, permafrost thaw, and concomitant land-cover changes, there is an urgent need on the part of provincial, territorial, and federal government agencies, NGOs, Aboriginal communities and industry to understand how these land-cover changes affect their shared water resources today and in the future. In response to this need SCRS researchers are working to 1) develop and mobilise new knowledge on the hydrological and ecological impacts of permafrost thaw, 2) develop new modelling tools to predict the rates and patterns of permafrost thaw and the hydrological and ecological consequences, and 3) provide interactive training on these tools to end-users. For more information regarding past, ongoing and future studies at Scotty Creek see Quinton et al. (2019).
About us. (2019). Scotty Creek Research Station. Retrieved from http://www.scottycreek.com/site/about
Aylesworth, J., & Kettles, I. (2000). Distribution of fen and bog in the Mackenzie Valley, 60 ˚N-68 ˚N. The Physical Environment of the Mackenzie Valley: A Base Line for the Assessment of Environmental Change, in Geol. Surv. Bull. 547 (map sheet), Natural Resources Canada, Ottawa, Canada.
Braverman, M., & Quinton, W. Hydrological impacts of seismic lines in the wetland-dominated zone of thawing, discontinuous permafrost, Northwest Territories, Canada. Hydrological Processes, 30(5), 2617-2627. https://doi.org/10.1002/hyp.10695
Connon, R., Devoie, É., Hayashi, M., Veness, T., & Quinton, W. (2018). The influence of shallow taliks on permafrost thaw and active layer dynamics in subarctic Canada. JGR Earth Surface, 123(2), 281-297. https://doi.org/10.1002/2017JF004469 Ecodynamics Consulting Inc. (2008). Northwest Territories soil survey enhancement project: Final report. Retrieved from http://sis.agr.gc.ca/cansis/publications/surveys/nt/nts2008/nts2008_report.pdf
Garon-Labrecque, M., Leveille-Bourret, E., Higgins, K., & Sonnentag, O. (2015). Additions to the boreal flora of the northwest territories with a preliminary vascular flora of Scotty Creek. Can FieldNat, 129(4), 349-367
Hayashi, M., Quinton, W., Pietroniro, A., & Gibson, J. (2004). Hydrologic functions of wetlands in a discontinuous permafrost basin indicated by isotopic and chemical signatures. Journal of Hydrology, 296, 81-97. doi:10.1016/j.jhydrol.2004.03.020
Haynes, K., Connon, R., & Quinton, W. (2018). Permafrost thaw induced drying of wetlands at Scotty Creek, NWT, Canada. Environmental Research Letters, 13(11), 114001. https://doi.org/10.1088/1748-9326/aae46c
Higgins, K., Garon-Labrecque, M. (2018). Fine-scale influences on thaw depth in a forested peat plateau landscape in the Northwest Territories, Canada: Vegetation trumps microtopography. Permafrost and Periglacial Processes, 29, 60-70. https://doi.org/10.1002/ppp.1961
Quinton, W., Baltzer, J. (2013). The active-layer hydrology of a peat plateau with thawing permafrost (Scotty Creek, Canada). Hydrogeology Journal, 21(1), 201-220. DOI 10.1007/s10040-012-0935-2
Quinton, W., Berg, A., Braverman, M., Carpino, O., Chasmer, L., Connon, R., Craig, J., Devoie, É., Hayashi, M., Haynes, K., Olefeldt, D., Pietroniro, A., Rezanezhad, F., Schincariol, R., & Sonnentag, O. (2019). A synthesis of three decades of hydrological research at Scotty Creek, NWT, Canada. Hydrology and Earth System Science, 23, 2015-2039. https://doi.org/10.5194/hess-23-2015-2019 Richter-Menge, J., Overland, J., Mathis, J., & Osborne, E., Eds. (2017). Arctic Report Card 2017. Retrieved from http://www.arctic.noaa.gov/Report-Card