Nonlinear thermal and moisture dynamics of high Arctic wetland polygons following permafrost disturbance

Abstract

Abstract. Low-centre polygonal terrain developing within gentle sloping surfaces and lowlands in the high Arctic have a potential to retain snowmelt water in their bowl-shaped centre and as such 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 are rapidly eroding the permafrost along ice wedges affecting the integrity of the polygons by breaching and collapsing the surrounding rims. While intact polygons were characterized by a relative homogeneity (topography, snow cover, maximum active layer thaw depth, ground moisture content, vegetation cover), eroded polygons had a non-linear response for the same elements following their perturbation. The heterogeneous nature of disturbed terrains impacts active layer thickness, ground ice aggradation in the upper portion of permafrost, soil moisture and vegetation dynamics, carbon storage and terrestrial green-house gas emissions.

Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems

“…The spatial distribution and life cycle of press and pulse disturbances will also govern the impact that they have on the delivery of biogeochemical constituents to aquatic ecosystems. For example, TEFs (thermo-erosional features) are discretely distributed across the landscape, following variations in topography (affecting, for example, snow cover; Godin et al, 2015) and ground ice content. While these features can be numerous in impacted areas (Lacelle et al, 2015) they take up a relatively small percentage of the total landscape area (1.5 % in Alaska; Krieger, 2012).…”

Effects of changing permafrost and snow conditions on tundra wildlife: critical places and times

“…These gullies can create, over a period of only a few years, new drainage channels and completely change the local hydrology (Fig. 8e), which has cascading effects on the surrounding landscape, including change in the topography, snow cover, maximum active layer thaw depth, and ground moisture content (Godin et al 2015).…”

“…Our review identifies the buffer layer, particularly its snow component, as the most influential part of the permafrost system for the ecology of tundra wildlife. Godin et al 2015;Gilg et al 2009;Bilodeau et al 2013aBilodeau et al , 2013cZimova et al 2016 Weather conditions during fall onset of the snowpack have long-lasting effects on its insulating properties (Insulation)…”

Thermo-erosion gullies boost the transition from wet to mesic vegetation

“…Species richness and abundance were determined in each polygon in July 2009 or 2010 using randomly placed 70 cm × 70 cm quadrats within areas that were representative of habitats. Abundance of vascular plants, lichens, mosses, Nostoc, fungi, cryptogamic crust, bare ground, litter, standing dead, standing water, sings of grubbing, 5 and geese feces was evaluated as cover percentages using photography analyses. Three quadrats were vertically photographed at each site at ca 1.3 m from the ground (see detailed protocols in Chen et al, 2010 andthe IPY CiCAT, 2012).…”

“…For instance, permafrost impedes water to drain to deeper soil layers maintaining a perched water table and saturated soils across the Arctic (Woo, 2012;Natali et al, 2015). These wet habitats are dominated by highly pro- 5 ductive graminoid species which offer abundant high quality food for arctic herbivores (Manseau and Gauthier, 2003;Doiron, 2014) while significantly contributing to methane emission (Brummel et al, 2012;Bouchard et al, 2014). Permafrost degradation that would increase subsurface drainage and reduce the extent of lakes and wetlands at high latitudes (Avis et al, 2011;Jorgenson et al, 2013;Beck et al, 2015) would have 10 major consequences on ecosystem structure and function (Collins et al, 2013;Jorgenson et al, 2013).…”