Those changes in atmospheric circulation that are attributed to reduced sea-ice and snow cover at high latitudes are linked to extreme summer weather events in areas that include Europe, Asia and much of North America. This finding is reported a paper published in Nature Climate Change this week.
In the past three decades the Northern Hemisphere has experienced record declines in the summer sea-ice and snow cover at high latitudes, as well as a recent increase in extreme summer events, such as heatwaves and droughts or wash-out summers and floods, in mid-latitude regions. The connection between these factors has, however, been unclear. Qiuhong Tang and colleagues use satellite observations of summer snow cover and sea-ice extent in combination with atmospheric data to investigate circulation patterns and demonstrate the link between the loss of snow and ice and mid latitude weather conditions. They find distinct circulation patterns associated with the reduced snow and ice, with ice loss producing a stronger response. They note that upper atmospheric winds north of 60° N weaken and the jetstream generally shifts northwards - these changes allow weather systems to remain in one location for longer periods, increasing the chance of extreme events. Their results suggest that summer extremes will continue to increase in frequency and intensity as the Arctic experiences more snow and ice loss.
In an accompanying News and Views, James Overland writes that “Greater understanding of the changing Arctic may allow seasonal and longer term weather outlooks to be produced”.