Anomalous Arctic warming linked with severe winter weather in Northern Hemisphere continents

We have extended a recently developed metric that ingests United States station data—the accumulated winter season severity index—to a global indicator based on temperature and snowfall from reanalysis output. The expanded index is analyzed to reveal relationships between Arctic air temperatures/pressures and the probability of severe winter weather across the Northern Hemisphere midlatitudes. Here we find a direct and quasilinear relationship between anomalously high Arctic temperatures/pressures and increased severe winter weather, especially in northeastern continental regions downstream of maximum regional Arctic warming. Positive temperature trends in the Arctic are associated with positive trends in severe winter weather across the continents in mid- to late-winter, coinciding with an increase in stratospheric polar vortex disruptions. During the era of rapid Arctic warming, variability has decreased over the Arctic Ocean and Europe, but has increased in Canada, the Northern US and northeast Asia, indicating more pronounced shifts in weather conditions. Anomalously high Arctic pressures and temperatures are directly and quasi-linearly linked to incidents of severe winter weather in the northern mid-latitudes, especially downstream of maximum regional Arctic warming, according to an analysis using an updated index of accumulated winter severity.