Articles | Volume 13, issue 5
Research article
08 Mar 2016
Research article |  | 08 Mar 2016

Nonlinear thermal and moisture response of ice-wedge polygons to permafrost disturbance increases heterogeneity of high Arctic wetland

Etienne Godin, Daniel Fortier, and Esther Lévesque

Abstract. Low-center polygonal terrains with gentle sloping surfaces and lowlands in the high Arctic have a potential to retain water in the lower central portion of ice-wedge polygons and are considered high-latitude wetlands. Such wetlands in the continuous permafrost regions have an important ecological role in an otherwise generally arid region. In the valley of the glacier C-79 on Bylot Island (Nunavut, Canada), thermal erosion gullies were rapidly eroding the permafrost along ice wedges affecting the integrity of the polygons by breaching and collapsing the surrounding rims. Intact polygons were characterized by a relative homogeneity in terms of topography, snow cover, maximum active layer thaw depth, ground moisture content and vegetation cover (where eroded polygons responded nonlinearly to perturbations, which resulted in differing conditions in the latter elements). The heterogeneous nature of disturbed terrains impacted active layer thickness, ground ice aggradation in the upper portion of permafrost, soil moisture, vegetation dynamics and carbon storage.

Short summary
Bowl-shaped ice-wedge polygons in permafrost regions can retain snowmelt water and moisture in their center. On Bylot Island (NU, CA), a rapidly developing thermal erosion gully eroded the polygons' ridges, impacting the polygon centers' ground moisture and temperature, plant cover and species. An intact polygon was homogeneous in its center for the aforementioned elements, whereas eroded polygons had a varying response following the breach, with heterogeneity as their new equilibrium state.
Final-revised paper