Arctic rain on snow events: bridging observations to understand environmental and livelihood impacts

Whenrain falls onan existing coverofsnow,followed bylowtemperatures,orfalls asfreezing rain,it can leave a hard crust. These Arctic rain on snow (ROS) events can profoundly influence theenvironment and in turn, human livelihoods. Impacts can be immediate (e.g. on human travel,herding, or harvesting) or evolve or accumulate, leading to massive starvation-induced die-offs ofreindeer, caribou, and musk oxen, for example. We provide here a review and synthesis of ArcticROS events and their impacts, addressing human-environment relationships, meteorologicalconditions associated with ROS events, and challenges in their detection. From our assessment ofthe state of the science, we conclude that while (a) systematic detection of ROS events, theirintensity, and trends across the Arctic region can be approached by combining data from satelliteremote sensing, atmospheric reanalyses, and meteorological station records; (b) obtainingknowledge and information most germane to impacts, such as the thickness of ice layers, how icelayers form within a snowpack, and antecedent conditions that can amplify impacts, necessitatescollaboration and knowledge co-production with community members and indigenousknowledge-holders.