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Abstract One of the most conspicuous signals of climate change in high‐latitude tundra is the expansion of ice wedge thermokarst pools. These small but abundant water features form rapidly in depressions caused by the melting of ice wedges (i.e., meter‐scale bodies of ice embedded within the top of the permafrost). Pool expansion impacts subsequent thaw rates through a series of complex positive and negative feedbacks which play out over timescales of decades and may accelerate carbon release from the underlying sediments. Although many local observations of ice wedge thermokarst pool expansion have been documented, analyses at continental to pan‐Arctic scales have been rare, hindering efforts to project how strongly this process may impact the global carbon cycle. Here we present one of the most geographically extensive and temporally dense records yet compiled of recent pool expansion, in which changes to pool area from 2008 to 2020 were quantified through satellite‐image analysis at 27 survey areas (measuring 10–35 km²each, or 400 km²in total) dispersed throughout the circumpolar tundra. The results revealed instances of rapid expansion at 44% (15%) of survey areas. Considered alone, the extent of departures from historical mean air temperatures did not account for between site variation in rates of change to pool area. Pool growth was most clearly associated with upland (i.e., hilly) terrain and elevated silt content at soil depths greater than one meter. These findings suggest that, at short time scales, pedologic and geomorphologic conditions may exert greater control on pool dynamics in the warming Arctic than spatial variability in the rate of air temperature increases. 

Since the early 2000s, observations from 14 coastal permafrost sites have been updated, providing a synopsis of how changes in the Arctic System are intensifying the dynamics of permafrost coasts in the 21st Century. Observations from all but 1 of the 14 permafrost coastal sites around the Arctic indicate that decadal-scale erosion rates are increasing. The US and Canadian Beaufort Sea coasts have experienced the largest increases in erosion rates since the early-2000s. The mean annual erosion rate in these regions has increased by 80 to 160 % at the five sites with available data, with sites in the Canadian Beaufort Sea experiencing the largest relative increase. The sole available site in the Greenland Sea, on southern Svalbard, indicates an increase in mean annual erosion rates by 66 % since 2000, due primarily to a reduction in nearshore sediment supply from glacial recession. At the five sites along the Barents, Kara, and Laptev Seas in Siberia, mean annual erosion rates increased between 33 and 97 % since the early to mid-2000s. The only site to experience a decrease in mean annual erosion (- 40%) was located in the Chukchi Sea in Alaska. Interestingly, the other site in the Chukchi Sea experienced one of the highest increases in mean annual erosion (+160%) over the same period. In general, a considerable increase in the variability of erosion and deposition intensity was also observed along most of the sites.