The loss of Arctic sea-ice may be responsible for the weakened polar vortex and bitterly cold Northern Hemisphere winters in recent years, according to a study published in Nature Communications.

Successive cold winters in recent years have had critical social and economic impacts on both Europe and the USA. The suggested cause for these extreme drops in temperature has been the polar vortex and while links to reductions in Arctic sea-ice have been made in the past, no firm mechanism has been proposed.

Seong-Joong Kim and colleagues conduct observational analyses and model experiments to reveal a dynamic connection between Arctic sea-ice loss and atmospheric circulation through the polar upper atmosphere. The team show that reduced early winter sea-ice cover in the Siberian sector of the Arctic Ocean can lead to the release of extensive levels of heat into the upper atmosphere. Model simulations suggest that this heat flux can interfere with the structure of the westerly jet stream, which weakens the polar vortex.

Arctic sea-ice loss represents only one of the possible factors that can affect the polar vortex. Other factors must be systematically considered in order to extend our understanding and lead to improved seasonal forecasts.