Distribution of ice-wedge polygons in Kangerlussuaq, Western Greenland, and association with other periglacial landforms 

Abstract

Investigating the regional distribution of ice-wedge polygons allows for the estimation of permafrost conditions in periglacial environments, assess its vulnerability to degradation and anticipate how ice-wedge polygons will respond to climate change. Here we investigate the spatial distribution, substrate, and geometric properties of ice-wedge polygons as well as their relationship with other periglacial landforms in Western Greenland near the settlement of Kangerlussuaq. Ice-wedge polygons are networks of interconnected ice-filled fractures that develop in periglacial environments during cyclical drops of temperatures. To investigate the current state of ice-wedge polygons near Kangerlussuaq we conducted a field campaign in July 2023 as part of the Europlanet Transnational Access program. We mapped and characterized ice-wedge polygons using a series of 2004 aerial photographs and our field observations. Polygons in our research area are decameter scale and are found on hillslopes in a sandy loess material that is overlain by a layer of peat and vegetation. We have observed polygons on hillslopes as steep as 36° which suggests that the slope material in our study area is stable and resistant to solifluction. While the polygons themselves did not display any substantial morphological modification between the 2004 aerial photographs and our study, we observed signs of rapid slope modification in the form of active layer detachment slides (ALDS). These relatively small slides (1.2-1.5 × 102 m3) overprinted ice-wedge polygons morphologies downslope, effectively obscuring the polygons without removing them. The frequency of ALDS in permafrost area could increase under the current context of warming temperatures in the Arctic, which would locally affect the ability of any satellite or aerial based studies to detect ice-wedge polygons on the affected hillslopes. We find that polygons are anti correlated with earth hummocks, another type of periglacial landform that develops in poorly drained sites. This suggests that the presence of polygons on a slope modifies the local hydrology by increasing the drainage efficiency, which inhibits the formation of earth hummocks. Our field observations indeed indicate that polygon troughs modify the local drainage and act as water tracks. We observed soil piping and mobilization of small volumes (~1m3) of subsurface material along these troughs. This removal of material is probably facilitated by the absence of coarse material in the sandy loess that composes these slopes. While the extensive vegetation cover in our study area most probably increases the ground resistance to surface erosion via root consolidation and absorption of ground moisture, we suggest that subsurface erosion along polygon troughs will increase if the magnitude of water flow on these hillslopes increases, which should be expected under the current context of wetter-than-normal conditions in the Arctic due to climate change. Finally, we find that 64 % of all polygonised areas we mapped are found on north-west facing hillslopes and 76% are found on slopes steeper than five degrees, which indicate that topography and insolation have been the most likely controls for the development of ice-wedge polygons in this region.