Recent Thaw and Ponding of Upland Ice-Wedge Polygons Across the Canadian Arctic Archipelago

Wedge ice is the most widespread ground ice type in Arctic permafrost. Tundra polygons are the surface manifestation of underlying ice-wedge networks, which develop over millennia due to thermal contraction cracking of the ground and infilling by snowmelt. Wedge ice is often encountered at the top of permafrost, so near-surface thawing can result in subsidence of the terrain surface, ponding, and the development of high centred polygons. Local-scale observations and high resolution remote sensing have demonstrated that recent ice-wedge thaw is a pan-Arctic phenomenon. In our analysis, we used a combination of the 1985-2017 Landsat satellite image archive, high resolution WorldView satellite images, historical air photos, detailed digital elevation models, and field surveys to show that upland ice-wedge thermokarst has been extensive over a 419 000 km² region within the Canadian Arctic Archipelago. We show that newly formed ice-wedge melt ponds are larger (avg. ~ 100 m²) and more widespread than those previously characterized in most other Arctic regions, which have resulted from several anomalously warm summers since 1998. We also observed that upland polygonal terrain in the lower-Arctic, NWT and Yukon coastlands has shown more limited ice-wedge ponding over the same period under similar warming. The contrasting landscape responses highlight the inherent sensitivity of higher Arctic, formerly glaciated permafrost environments with high massive ground ice content that is being truncated by an active layer lacking ecosystem protection from summer warming. Increasing evidence suggests that ongoing temperatures increases are likely to most rapidly alter these landscapes.