Rare events in the Arctic

Twenty years ago, the Arctic was more resilient than now as sea ice was three times thicker than today. Heavier and more persistent sea ice provided a buffer against the influence of short-term climate fluctuations. Sea ice/atmospheric interactions now point to revisiting the concept of abrupt change. The recent decade has seen Arctic extreme events in climate and ecosystems including some events beyond previous records that imply increased future uncertaintly. While their numbers may increase, the distribution of the type, location, and timing of extreme events are less predictable. Recent processes include albedo shifts and increased sensitivity of sea ice to storms in marginal seas. Such new extremes include Greenland ice mass loss, sea ice as thin and mobile, coastal erosion, springtime snow loss, permafrost thaw, wildfires, and bottom to top ecosystem reorganizations, a consilience of impacts. One cause for such events is due to natural variability in a wavy tropospheric jet stream and polar vortex displacements, interacting with ongoing Arctic Amplification: temperature increases, sea ice loss, and permafrost thaw. This connecting hypothesis is validated by the variability of rare events matching interannual and spatial variability of weather. A proposed way forward for adaptation planning is through narrative/scenario approaches. Unless CO2 emissions are reduced, further multiple types of Arctic extremes are expected in the next decades with environmental and societal impacts spreading through the Arctic and beyond.