Saturday, September 15, 2012

"We're In Uncharted Territory"

Europe could be plunged into a deep freeze again this winter, a condition linked to the disappearance of Arctic sea ice.  The Jet Stream is moving north and it's slowing, allowing the formation of slow-moving Rossby Waves that loop far south, bringing polar winter air into Europe as far south as the canals of Venice.   This phenomenon was also blamed for Britain's extended drought that was immediately followed this summer by massive flooding through most of the length of Britain.

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 [Rutgers University researcher Jennifer] 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.

...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."

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