Geomorphology of thermo-erosion gullies - case study from Bylot Island, Nunavut, Canada

Etienne Godin, Daniel Fortier

In the proceedings of: GEO2010 Calgary: 63rd Canadian Geotechnical Conference & 6th Canadian Permafrost Conference

Session: T3-E

ABSTRACT: In the valley of glacier C-79 on Bylot Island, snowmelt water runoff is creating thermo-erosion of permafrost wetlands. This process contributes to the rapid formation of gullies in ice-wedge polygons. One gully had been observed since 1999 and had a growth of 748 m since then. The geomorphology of this gully is characterized by an active thermo-erosion zone near the gully head, a poorly-active zone near the outlet and a moderately active zone in-between. Feedback mechanisms contribute to the erosion processes governing the development of the gully, accelerating erosion at its head and stabilizing it at its outlet. Erosion features such as sinkholes, collapses and baydjarakhs were consequently observed in the gully. Thermo-erosion processes have remained active and have had an impact on the ecosystem for more than a decade.

RÉSUMÉ: La thermo-érosion induite par la fonte du couvert nival cause la dégradation du pergélisol dans la vallée glaciaire C-79 sur l'Ile Bylot. Ce processus contribue à la formation rapide de réseaux de ravinement dans les polygones à coin de glace. L'observation d'un ravin depuis sa formation en 1999 et de son évolution jusqu'à 748 m en 2009, révèle trois types de zones d'érosion caractérisant sa géomorphologie : une zone de thermo-érosion très active en amont, une zone intermédiaire, et une zone faiblement active à proximité de l'exutoire. Les mécanismes de rétroaction amplifient l'érosion en tête de ravin et la stabilisent à l'exutoire. Des composantes géomorphologiques tels que des puits, effondrements et baydjarakhs sont conséquemment observées dans le ravin. Le déclenchement du processus de thermo-érosion souterrain exerce un impact sur l'écosystème depuis plus d'une décennie. 1 INTRODUCTION

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