Changing hydrologic connectivity due to permafrost thaw in the lower Liard River valley, NWT, Canada

Abstract

Flows from river basins in northwestern Canada have been rising in the last two decades as a result of climate warming. In the wetland‐dominated basins that characterise the southern margin of permafrost, permafrost thaw and disappearance, and resulting land‐cover change, is occurring at an unprecedented rate. The impact of this thaw on runoff generation in headwater basins is poorly understood. Permafrost thaw has the potential to fundamentally alter the cycling and storage of moisture inputs in this region by altering the type and relative proportions of the major land‐cover types, such as peat plateaus, channel fens and flat bogs. This paper examines streamflow changes in the four Water Survey of Canada gauged river basins (152–2050 km2) in the lower Liard River valley, Northwest Territories, Canada, a region where permafrost thaw has produced widespread loss of forest and concomitant expansion of permafrost‐free wetlands. Annual runoff in the lower Liard Valley increased by between 112 and 160 mm over the period of 1996–2012. The Mann‐Kendall non‐parametric statistical test and the Kendall‐Theil robust line were used to ascertain changes in streamflow. Historical aerial photographs from 1977 and high‐resolution satellite imagery (WorldView 2) from 2010 were used to measure the rate and pattern of permafrost thaw in a representative 6 km2 area of Scotty Creek. Permafrost thaw‐induced land‐cover change is both increasing the adjacency between runoff producing and transmitting land cover types and transforming certain land covers that store water into ones that produce runoff. This land‐cover change was found to be the single most important factor (37–61 mm) contributing to the observed increase in river discharge. Other contributing factors include increases in plateau runoff contributing areas (20–32 mm), increases in annual effective precipitation depth (18–30 mm), contribution of water from the melt of ice within permafrost (9 mm) and increases in baseflow (0.9–6.8 mm). Although runoff has significantly (p < 0.05) increased in all four basins, the largest increases are in basins with a relatively high cover of flat bogs. Copyright © 2014 John Wiley & Sons, Ltd.

Recent climatic, cryospheric, and hydrological changes over the interior of western Canada: a review and synthesis

“…Similar analysis at the Scotty Creek Research Basin near Ft. Simpson (Quinton et al, 2011) showed that the extent of forest-covered permafrost plateaus had decreased by over 38 % in localized areas between 1947 and 2008, with associated collapse of black spruce forest on the plateaus and an increasingly connected surface drainage network. This has the potential to substantially alter basin runoff production in the region (Connon et al, 2014). Further, it has been shown that the rates of permafrost and forested plateau loss have been accelerating, with the average rate of loss in seven different local areas of interest being over 3 times greater during the period -2010compared to 1977(Baltzer et al, 2014.…”

Hydrological Response of Alpine Wetlands to Climate Warming in the Eastern Tibetan Plateau

“…In both alpine and northern wetlands, the existence of thick soil organic layers plays a large role in regulating hydrological sensitivity (including changes in surface ET) to climate warming due to high porosity and hydraulic conductivity of organic soil [54]. In addition, the existence of permafrost helps maintain high water tables and enhance soil saturation even under relatively dry climate conditions by limiting water infiltration to deep soil layers [58]. However, warming-induced permafrost degradation may have a much larger impact on the surface hydrology of northern wetlands underlain by greater permafrost coverage, while the potential influence of warming-induced permafrost thaw on TP wetlands is likely limited due to only sparse permafrost cover in these areas [46,59].…”

“…However, warming-induced permafrost degradation may have a much larger impact on the surface hydrology of northern wetlands underlain by greater permafrost coverage, while the potential influence of warming-induced permafrost thaw on TP wetlands is likely limited due to only sparse permafrost cover in these areas [46,59]. For example, permafrost thaw may change the hydrological connectivity of northern wetlands, and increase surface/subsurface runoff [58,60,61], while similar impacts of permafrost thaw in TP wetlands are expected to be minimal.…”

Recent changes to the hydrological cycle of an Arctic basin at the tundra–taiga transition

“…A reduced snow cover period can result in smaller and slower snowmelt, larger evapotranspiration losses and reduced sublimation losses from headwater basins in cold regions Rasouli et al, 2015). Permafrost thaw can impact regional and local hydrology by increasing surface and subsurface connectivity and baseflow (Connon et al, 2014;Liljedahl et al, 2016;Walvoord and Kurylyk, 2016). Increases in vegetation cover and density have been observed and are especially pronounced near the tundra-taiga ecozone transition (Lantz et al, 2013;Myers-Smith et al, 2011;Sturm et al, 2001;Tape et al, 2006;Xu et al, 2013); however, the impact on the hydrology of these transition Arctic basins is poorly understood.…”