Changes in ice‐wedge activity over 25 years of climate change near Salluit, Nunavik (northern Québec, Canada)

To assess the direct impact of climate change on ice‐wedge (IW) degradation, 16 sites in the Narsajuaq river valley (Nunavik, Canada) that were extensively studied between 1989 and 1991 were revisited in 2016, 2017 and 2018. In total, 109 pits were dug to record soil characteristics and IW shapes and depths. Changes in surface conditions were also noted using side‐by‐side comparisons of recent (2017) and older (1989–1991) land and aerial photographs. During the past 25 years, the active layer reached depths that were 1.2–3.4 times deeper than in 1991, which led to the widespread degradation of IWs in the valley. Whereas 94% of the IWs unearthed in 1991 showed multiple recent growth structures, only 13% of the 55 IWs unearthed in 2017 still had some upgrowth stages left. IW tops are now consistently deeper than the main stages of the IWs measured in 1991. In August 2017, however, about half of the IWs had ice veins connecting them to the base of the active layer, an indication that the recent cooling spell (2010 to present) in the region was enough to reactivate frost cracking and IW growth. This paper highlights how sensitive the Arctic soil system can be to short‐term climate variations.