The fate of water from melting ground ice in degrading permafrost environment

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Among the geohazards associated with permafrost degradation which impact the sustainable development of Northern Canada, the vulnerability to thaw subsidence is widespread. The thaw consolidation of permafrost is closely related to water content, cryostructure, soil texture, rates of thawing and dissipation of pore water pressure. However, little is known on the fate of water from melting ground ice in degrading permafrost. How does the pore water dissipation control the thaw consolidation? Where the meltwater is flowing into the ground? Is the meltwater recharging the aquifers at depths or is it migrating at the ground surface and ultimately finding its way in lakes, rivers, and oceans? ***As a research hypothesis and a positive feedback, the thaw subsidence which depends on the dissipation of pore water pressure accelerates the rate of permafrost degradation. The warm boundary at the ground surface is moving downwards toward the degrading permafrost body at depths which increases the permafrost thawing. ***For testing this research hypothesis, the objectives are to: ***1) observe, describe, and monitor in the field the processes of permafrost degradation, ***2) measure the thaw consolidation properties of ice-rich permafrost from laboratory tests, ***3) simulate the heat transfer, thaw consolidation and flow of meltwater which are taking place in degrading permafrost, ***4) compare these simulated processes with the observations, and ***5) anticipate the permafrost degradation in the future. ***The study site is located in the discontinuous permafrost zone close to Umiujaq in northern Quebec, Canada, where ice-rich permafrost mounds are already degrading. Long-term monitoring series of ground temperature and thaw subsidence data are already available for several locations. ***The methodology used in this research program relies heavily on ground truth from careful field observations using different monitoring techniques (automated thermistor cables, water level loggers, LiDAR surveys and visible and infrared photogrammetry), geotechnical and geophysical tools (permafrost sampling, electrical resistivity and seismic refraction tomography), and lab tests on ice-rich permafrost samples (thaw consolidation and hydraulic conductivity). Numerical modelling of thermal-hydro-mechanical processes will be performed to simulate permafrost degradation following different scenarios of climate changes. ***The expected outcomes from this research program are a better understanding of the physical processes which are taking place in degrading permafrost and the improvement of numerical modelling of heat transfer with phase change, thaw consolidation, meltwater migration and flow to anticipate permafrost degradation due to climate changes. From the knowledge developed in this research program, adaptation strategies could be established to insure the sustainable development of Northern Canada.