A Mechanism Linking Tropical-Arctic Teleconnection to Northern Hemisphere Mid-Latitude Weather Events

Abstract:

Several lines of research have suggested linkages between Arctic sea-ice loss and the Northern Hemisphere (NH) mid- and high-latitude circulation changes. These studies have collectively suggested various mechanisms in which sea-ice loss is an active modulator of NH mid-latitude large-scale circulation, weather, and extreme events. This is an area of vigorous scientific debate, and a consensus has not emerged; competing hypotheses clearly need to be examined. To contribute to this debate, we propose a new mechanism to explain the observed concurrence of the NH circulation trends and sea-ice loss in the past 30 years. Our mechanism is based on lines of evidence suggesting that the recent summer NH circulation trend in and around the Arctic is both natural and anthropogenic in origin, but natural variability originating primarily from the tropics plays a dominant role in generating the observed circulation pattern—especially the increasing height over Greenland and northeastern Canada—which may play a key role in modulating Arctic sea-ice change and the mid-latitude weather and extreme events over North America at the same time.