This year's ice melt has broken the 2007 record by an an area larger than the state of Texas. Polar ice experts "thought that it would be many years until we again saw anything like we saw in 2007", said Mark Serreze, director of the National Snow and Ice Data Centre in Colorado.
The unprecedented expanse of ice-free Arctic Ocean has been absorbing the 24-hour sun over the short polar summer. The heat in the water must be released into the atmosphere if the ice is to re-form this autumn. "This is like a new energy source for the atmosphere," said Francis.
This heat and water vapour will affect the all-important jet stream – the west-to-east winds that are the boundary between cold Arctic and the warm mid-latitudes. Others researchers have already shown that the jet stream has been shifting northwards in recent years. Francis and colleagues have recently documented that the jet stream is also slowing down.
"The jet stream is clearly weaker," said Francis. That means weather systems, be it rain or dry conditions, are slow to move on and last longer. Ultimately this can result in "blocking" events, such as the conditions that produced the terrible heatwave in western Russia during the summer of 2010, she said.
This summer, Greenland experienced a similar blocking anti-cyclone, resulting in a record surface melting of its ice sheet. It is not possible to directly connect that block to the prolonged US heatwave and drought this summer, Francis said. However "blocks act like a traffic jam, slowing down weather patterns elsewhere".
These changes are happening much earlier than scientists thought, said James Overland, an oceanographer and researcher at the University of Washington.
"We've only had a little bit of global warming so far," Overland said. As the sea ice continues to decline, the jet stream will likely continue to slow more, and shift further north "bringing wild temperature swings and greater numbers of extreme events" in the future he said. "We're in uncharted territory."