520, Chemin de la Côte Ste-Catherine
Université de Montréal
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Common in alpine and polar environments, perennial icy-snow patches consist of superimposed ice accumulations overlaid by firn which could persist for several centuries and millennia. This cryospheric component is generated by local snow drift over-accumulations which gradually metamorphose into firn and then pluriannual ice (Serrano et al., 2011). The icy-snow patches are considered as an intermediate state in the seasonal snow to glacier continuum (Glazirin et al, 2003). In non-glaciated polar desert settings, such as in the High Arctic regions and in the Antarctic dry valleys, melt water delivered by perennial icy-snow patches through the summer represent the major source of water input into the hydro-morphological system of catchments and generally favour the development of local wetlands with freshwater ecosystems. Due to their general upslope position, the icy-snow patches are the driver of several hydro-morphological processes along the polar toposequences. They affect water storage and flowing, geomorphic processes, soil moisture, weathering, biological activity, active layer thickness and permafrost cryofacies. As all cryospheric components, icy-snow patches are highly sensitive to climate fluctuations, making them a good indicator of climate change. Following an air temperature warming, their mass balance tends to become negative (i.e. greater annual snow/ice loss than gain) and a rapid reduction of their area and thickness has recently been observed in the Arctic (Woo and Young, 2014). The shrinkage of the icy-snow patches in polar deserts is expected to trigger major disequilibrium in the whole hydrological, geomorphological and biological geosystems of polar regions.
For 15 years, Ward Hunt Island (83.1°N; 74.1°W) has become an important reference site of the program Northern Ellesmere Island in the Global Environment (NEIGE) which aims to study the extreme geosystems and ecosystems in the Canadian High Arctic and their responses to the climate changes. Ward Hunt Island is home to the northernmost CEN research station. The site is of great interest due to its extreme high latitude, its polar arid climate, the presence of the northernmost lake in Canada, a pronounced relief and a great diversity of periglacial landforms and processes (Vincent et al., 2011). The island is non-glaciated but multiple perennial icy-snow patches lay in topographic depressions, breaks-of-slope and leeward sides of hills, which provide an ideal setting for my research. This PhD project addresses the geomorphological research questions of the NEIGE (GEO-NEIGE) targeted at understanding the complex system of interactions between the cryosphere (snow, ice, ground ice), mass movements on slopes and the morphological evolution of Ward Hunt lake.
The impact of the perennial icy-snow patches and the seasonal snowbanks on landscape dynamics has been studied through the concept of nivation that gathers gelifraction, sediment transfer/deposition, and solifluction processes linked to the presence of the snow patches and their meltwater. Researches on nivation have been quite prolific in the 1980’s, especially in the alpine environment, with authors like Ballantyne (1978); Thorn (1978) and Hall (1980). In the High Arctic polar desert, some studies focused on the hydrological impact of perennial icy-snow patches and snowbanks on wetland formation and dynamic in small watersheds (e.g. Ballantyne, 1978; Lewkowicz et Young 1990; Woo et Young, 2003), however detailed studies addressing their geomorphological significance are very scarce in scientific literature.
My research is thus motivated by the need to fill the gaps in scientific knowledge about the role of the icy-snow patches on the evolution of the polar desert landscape, and by the importance to evaluate the magnitude of the potential environmental changes brought by the recent shrinkage of ice patches.
The overall objective is to provide baseline data on the icy-snow patches characteristic and dynamic, and to qualify and quantify the significance of hydro-morphological processes driven by icy-snow patches in the evolution of the toposequences and of the lake in Ward Hund Island. More specifically, the project encompasses 3 objectives:(i) to characterize the spatial distribution of the icy-snow patches, to estimate their mass balance and to analyze the physics, geochemistry and crystallography of the firn and ice which compose it.
(ii) to characterize the hydrological regime of the icy-snow patches and their implications on the storage and transfers of water and sediment, and quality of runoff along the toposequences.
(iii) to demonstrate how the sediment inputs linked to the solifluction and denudation processes driven by inflow of meltwater from icy-snow patches control the morphology of the toposequences and the bathymetry of Ward Hunt Lake.
The project supports the hypothesis that the meltwater delivered by the icy-snow patches during the short thaw season lead to an hydrological and sedimentary connectivity between the upper portion of the toposequences and the lake. This dynamic interaction between icy-snow patches, slopes, permafrost and the lake is major in the control of the landscape evolution in Ward Hunt Island. On the slopes, meltwater flows are expected to be main driver of soil denudation, sediment transfer/deposition and downslope soil creep. That create specific landforms and environments along the toposequences such as water tracks, blockstreams, wetland, solifluction sheet flows and gelifluction lobes. On the lower portion of the slopes, the input of sediments, water and nutrient brought by the meltwater may have a great importance on active layer development, permafrost structure, biochemistry and sediment budget of the lake.
Davesne, G., Fortier, D., Domine, F., Gray, J.T., 2017. Wind-driven snow conditions control the occurrence of contemporary marginal mountain permafrost in the Chic-Choc Mountains, south-eastern Canada: A case study from Mont Jacques-Cartier. The Cryosphere, 11(3): 1351-1370. DOI: 10.5194/tc-11-1351-2017, 2017.
Gray, J.T., Davesne, G., Fortier, D., Godin, E., 2017. The thermal regime of mountain permafrost at the summit of Mont Jacques-Cartier in the Gaspé Peninsula, Québec, Canada: A 37 year record of fluctuations showing an overall warming trend. Permafrost and Periglacial Processes, 28(1): 266-274. DOI: 10.1002/ppp.1903.