Highly read on www.agu.org 17 Mar–16 Apr

The Arctic is warming faster than the rest of the Northern Hemisphere; this could be increasing the likelihood of extreme weather events in mid-latitude regions by altering the circulation of air currents in the upper atmosphere.

Jennifer Francis at Rutgers University in New Brunswick, New Jersey, and Stephen Vavrus at the University of Wisconsin-Madison studied changes in 'Rossby waves' — large north-south meanders in high-altitude winds. The authors detected a slowed eastward movement of Rossby waves in a fast-flowing air current called the jet stream, and identified two contributing factors: weaker west-to-east winds and increased wave amplitude. Both of these seem to be linked to earlier spring snow-melt on high-latitude land and to sea-ice loss in summer — two likely consequences of enhanced Arctic warming.

A slowing of jet-stream waves that influence weather leads to more persistent weather patterns in the mid-latitudes. This could raise the likelihood of drought, flooding, cold snaps and heatwaves.

Geophys. Res. Lett. http://dx.doi.org/10.1029/2012GL051000 (2012)