Daniel Fortier

Effects of thermo-erosion gullying on hydrologic flow networks, discharge and soil loss

Thermo-erosion gullies in continuous permafrost regions where ice-wedge polygons are widespread contribute and change the drainage of periglacial landscapes. Gullying processes are causing long-term impacts to the Arctic landscape such as drainage network restructuring, permafrost erosion, sediment transport. Between 2009 and 2013, 35 gullies were mapped in a polygon terrace in the valley of the Glacier C-79 on Bylot Island, Nunavut (Canada), one of which was monitored for its hydrology. A gully (R08p) initiated in 1999 in a low-center polygon terrace. Between 1999 and 2013, 202 polygons over a surface of 28 891 m2 were breached by gullying. Overall, 1401 polygons were similarly breached on the terrace in the valley before 2013. R08p is fed by a 1.74 km2 watershed and the hydrological regime is characterized by peak flows of 0.69 m3 s−1 and a cumulative volume of 229 662 m3 for 2013. Historic aerial photography from 1972 and recent field surveys showed a change in the paths of water tracks and an increase in channelized flow in the gully area from none to 35% of the overall flow path of the section. The overall eroded area for the studied gullies in the valley up to 2013 was estimated at 158 000 m2 and a potential volume close to 200 000 m3. Gullying processes increased drainage of wetlands and the hydrological connectivity in the valley, while lowering residence time of water near gullied areas.

Extreme Ecosystems and Geosystems in the Canadian High Arctic: Ward Hunt Island and Vicinity

Abstract: Global circulation models predict that the strongest and most rapid effects of global warming will take place at the highest latitudes of the Northern Hemisphere. Consistent with this prediction, the Ward Hunt Island region at the northern terrestrial limit of Arctic Canada is experiencing the onset of major environmental changes. This article provides a synthesis of research including new observations on the diverse geosystems/ecosystems of this coastal region of northern Ellesmere Island that extends to latitude 83.11° N (Cape Aldrich). The climate is extreme, with an average annual air temperature of -17.2 °C, similar to Antarctic regions such as the McMurdo Dry Valleys. The region is geologically distinct (the Pearya Terrane) and contains steep mountainous terrain intersected by deep fiords and fluvial valleys. Numerous glaciers flow into the valleys, fiords, and bays, and thick multi-year sea ice and ice shelves occur along the coast. These extreme ice features are currently undergoing rapid attrition. The polar desert landscape contains sparse, discontinuous patches of vegetation, including dense stands of the prostrate shrub Salix arctica (Artic willow) at some sites, and 37 species of vascular plants on Ward Hunt Island. Diverse aquatic ecosystems occur throughout the area, including meromictic, epishelf, and perennially ice-covered lakes. Many of these have responded strongly to climate shifts in the past and like other geosystems/ecosystems of the region are now sentinels of ongoing global climate change.

Rapid disappearance of perennial ice on Canada's most northern lake

Field records, aerial photographs, and satellite imagery show that the perennial ice cover on Ward Hunt Lake at Canadas northern coast experienced rapid contraction and thinning after at least 50 years of relative stability. On all dates of sampling from 1953 to 2007, 3.5 to 4.3 m of perennial ice covered 65–85% of the lake surface in summer. The ice cover thinned from 2008 onward, and the lake became ice free in 2011, an event followed by 26 days of open water conditions in 2012. This rapid ice loss corresponded to a significant increase in melting degree days (MDD), from a mean (±SD) of 80.4 (±36.5) MDD (1996–2007) to 136.2 (±16.4) MDD (2008–2012). The shallow bathymetry combined with heat advection by warm inflows caused feedback effects that accelerated the ice decay. These observations show how changes across a critical threshold can result in the rapid disappearance of thick perennial ice.

A late-Holocene record of loess deposition in ice-wedge polygons reflecting wind activity and ground moisture conditions, Bylot Island, eastern Canadian Arctic

On Bylot Island, a field of tundra polygons at the margin of a glacial outwash plain contains a well-preserved syngenetic permafrost sequence of ground ice and alternating loess and organic layers that was accumulated during the late Holocene. Periods of increased deposition of loess alternated with periods of growth of bryophytes during the last 3500 years. These shifts in soil accretion regime are interpreted in terms of significant shifts of the summer surface wind conditions and active layer moisture regime (Precipitation-Evaporation or P-E), in response to regional climatic variations and recurrent changes of atmospheric circulation. There was a high level of variability and large amplitude of the P-E regime and summer surface wind conditions on a decennial and secular timescale in general. However, according to the Greenland GISP2 bi-decennial oxygen isotopes data, there was a low variability and amplitude (by a few degrees centigrade or less) of the regional mean annual air temperature. From 2950 to 2750 cal. BP, the summer climate was warmer and had the strongest and most frequent northwesterly surface winds of the late Holocene. Shifts to a weaker northwesterly summer surface wind activity preceded the dryer episodes that occurred from 2750 to 2450 and around 1850 cal. BP. Major wetter episodes occurred from 2450 to 2350, around 2050, from 1750 to 1550, from 1350 to 1150 and from 550 to 250 cal. BP. There is no clear relationship between P-E or summer surface wind regimes and air temperatures. Shifts of late Holocene summer aeolian regime can probably be better explained by the recurrence of particular synoptic circulation types in response to changes in the position of the atmospheric eastern Canadian Polar Trough.

Water tracks in the High Arctic: A hydrological network dominated by rapid subsurface flow through patterned ground

Water tracks play a major role in the headwater basin hydrology of permafrost landscapes in Alaska and Antarctica, but less is known about these features in the High Arctic. We examined the physical and hydrological properties of water tracks on Ward Hunt Island, a polar desert site in the Canadian High Arctic, to evaluate their formation process and to compare with water tracks reported elsewhere. These High Arctic water tracks flowed through soils that possessed higher near-surface organic carbon concentrations, higher water content, and coarser material than the surrounding soils. The water track morphology suggested they were initiated by a combination of sorting, differential frost heaving, and eluviation. The resultant network of soil conduits, comparable to soil pipes, dominated the hydrology of the slope. The flow of cold water through these conduits slowed down the progression of the thawing front during summer, making the active layer consistently shallower relative to adjacent soils. Water trac...

Thermal Effectiveness of the Mitigation Techniques Tested at Beaver Creek Experimental Road Site Based on a Heat Balance Analysis: Yukon, Canada

To better understand permafrost degradation under roadways, 12 experimental sections were constructed on the Alaska Highway near Beaver Creek in April 2008. These techniques designed to prevent permafrost thawing are: air convection embankments, heat drains, snow/sun sheds, longitudinal culverts, light-coloured aggregate for road surfacing, snow plowing techniques and grass-covered embankments. This paper presents the results of the analysis on heat balance for each section during the first three years in service to determine the short term effectiveness of the techniques.

ASSESSING LAND SUITABILITY FOR RESIDENTIAL DEVELOPMENT IN PERMAFROST REGIONS: A MULTI-CRITERIA APPROACH TO LAND-USE PLANNING IN NORTHERN QUEBEC, CANADA

Northern Quebec (Nunavik) presents an important intersection between population growth and climate change. The Inuit population of Nunavik has the fastest growth rate in any region of Canada. Land-use planning is an urgent and pressing need for northern communities built on permafrost, where there are considerable risks to development in areas where permafrost may thaw. As northern communities work to adapt to climate changes, they will be in great need of confident recommendations about locations of future development projects. This paper presents a case-study of the community of Tasiujaq and assesses the probability of thaw settlement of the surface, a process seriously affecting infrastructure stability. A method is developed for quantifying uncertainty in the resulting map, expressed as a function of judgmentbased uncertainty in the various factors that can influence eventual map quality. The best estimate of vulnerability and of the confidence in that estimate can be expressed in a single, simple map that allows an analyst to convey both of these vital aspects of the assessment process.

Syngenetic dynamic of permafrost of a polar desert solifluction lobe, Ward Hunt Island, Nunavut

Repeated freeze–thaw cycles on slopes trigger sorting and solifluction mass movements, while subsequent displacement of material modifies the geomorphology of slopes as well as permafrost dynamics. This study focuses on the geomorphology and the cryostratigraphy of a polar desert stone-banked solifluction lobe with the objective to clarify the impact of slow mass movements on ground ice aggradation. The morphology of the solifluction lobe was characterized by peripheral ridges of coarse gravel, partially surrounding a depression filled with finer sediments saturated with water and covered by organics. Cryostratigraphic analysis demonstrated that the solifluction lobe’s formation led to the development of a syngenetic layer of permafrost with an ice content that varied according to the location in the lobe. The ice-rich cryofacies formed in the central depression of the lobe should act as a buffer to potential active layer deepening, slowing down its thawing, whereas the ice-poor cryofacies formed under th...

Remote sensing evaluation of High Arctic wetland depletion following permafrost disturbance by thermo-erosion gullying processes

Northern wetlands and their productive tundra vegetation are of prime importance for Arctic wildlife by providing high-quality forage and breeding habitats. However, many wetlands are becoming drier as a function of climate-induced permafrost degradation. This phenomenon is notably the case in cold, ice-rich permafrost regions such as Bylot Island, Nunavut, where degradation of ice wedges and thermo-erosion gullying have already occurred throughout the polygon-patterned landscape resulting in a progressive shift from wet to mesic tundra vegetation within a decade. This study reports on the application of the normalized difference vegetation index to determine the extent of permafrost ecosystem disturbance on wetlands adjacent to thermo-erosion gullies. The analysis of a GeoEye-1 image of the Qarlikturvik valley, yielding a classification with five classes and 62% accuracy, resulted in directly identifying affected areas when compared to undisturbed baseline of wet and mesic plant communities. The total we...

Using Air Convection Ducts to Control Permafrost Degradation Under Road Infrastructure: Beaver Creek Experimental Site, Yukon, Canada

Thermal degradation of permafrost under road infrastructure regularly results in thaw settlement and severe structural damages. The present study discusses the results obtained by the implementation of a mitigation technique at a test section along the Alaska Highway near the Alaska-Yukon border (Beaver Creek). The objective of this study was to test possible way to slow down or prevent permafrost degradation under road embankment. Longitudinal air convection duct is a heat exchanger device based on fluid mechanics allowing for extraction of heat from the embankment by natural convective heat transfers during winter. Thermal analysis of the air temperature inside the ducts indicated that there was a strong thermal gradient between the inlets and the outlets, with air temperatures being 6 to 10˚C higher at the outlet than at in the inlet of the ducts. The cooling effect of the air convection duct system elevated the permafrost table by about 1 m over 3 years. This indicates that air convection ducts have a very good potential for heat extraction within road embankment and the underlying permafrost. This technique will likely find rapid applications in the engineering community aiming to develop adaptation strategies to climate warming for road infrastructure.