When the Arctic is warm both cold temperatures and heavy snowfall are more frequent compared to when the Arctic is cold. In this study we find a robust relationship between Arctic temperatures and severe winter weather in the United States. Here we present a more extensive, quantitative analysis of the link between Arctic variability and severe winter weather across the mid-latitudes. However, those studies were limited to just a few months of one particular year. Previous studies have shown qualitatively that anomalously high geopotential heights across the Arctic are linked with extreme weather events across the mid-latitudes in winter 18, 26 and even into spring 27. Surprisingly, however, over the past two to three decades, the increase in extreme weather has included more (not fewer) severe cold-air outbreaks and heavy snowfalls observed both in North America and Eurasia 6, 12, 15, 18, 22, 23, 24, 25. A vigorous debate in the climate community is whether and/or how much the Arctic can influence mid-latitude weather 9, 17 and, in particular, whether a warmer Arctic increases the likelihood of severe cold spells in the mid-latitude continents 18.Īnthropogenic global warming is widely expected to increase certain types of weather extremes, including more intense and frequent heat waves and droughts as well as heavy precipitation events 19, 20, 21. ![]() ![]() This seesaw winter temperature pattern is known as the “warm-Arctic/cold-continents pattern” 16. ![]() In winter, however, cooling trends have been observed across Eurasia and the eastern US 12, 13, 14 along with rapid warming in the Arctic 5, 6, 15. Over recent decades, warming has dominated global temperature trends during three of the seasons 11. Increasing greenhouse gases are contributing to a general warming of the atmosphere and oceans globally 10. While the tropics are usually considered the main driver of boundary-forced variability 3, 4, recent studies have argued that the Arctic is playing an increasingly important role as a boundary-forcing agent owing to its accelerated warming relative to other regions of the globe 5, 6, 7, 8, 9. Forced variability results from boundary conditions, such as sea-surface temperatures, and natural or internal variability results from the chaotic nature of dynamical systems 1, 2. Variability in the day-to-day weather is due to a combination of forced and natural variability. We also show that during mid-winter to late-winter of recent decades, when the Arctic warming trend is greatest and extends into the upper troposphere and lower stratosphere, severe winter weather-including both cold spells and heavy snows-became more frequent in the eastern United States. ![]() However, this relationship is strongest in the eastern US and mixed to even opposite along the western US. As the Arctic transitions from a relatively cold state to a warmer one, the frequency of severe winter weather in mid-latitudes increases through the transition. Using a recently developed index of severe winter weather, we show that the occurrence of severe winter weather in the United States is significantly related to anomalies in pan-Arctic geopotential heights and temperatures. Whether there is any physical link between Arctic variability and Northern Hemisphere (NH) extreme weather is an active area of research. Recent boreal winters have exhibited a large-scale seesaw temperature pattern characterized by an unusually warm Arctic and cold continents.
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