Tuesday, February 24, 2015

Warming Arctic behind Boston's deep freeze?

The polar jet stream carries weather around the Northern Hemisphere. Climate researcher Jenifer Francis believes the rapidly warming Arctic is slowing and warping the jet stream, allowing Arctic air to spill farther south in some places (NASA/Goddard Space Flight Center).
A strange thing happened here in Boston over the weekend: The temperature got above freezing. The massive dumps of snow here this winter have been bad enough, but it's the cold that's really done us in, an unbroken stretch of frigid weather that’s made Massachusetts feel more like Montreal -- or Anchorage.

And Rutgers University climate scientist Jennifer Francis has a counterintuitive explanation for all the cold: It's the warming Arctic.
More specifically, Prof. Francis thinks the warming Arctic is causing the jet stream to slow down and get a lot more loopy, which lets big masses of frigid air slip south.
  • GLOBE: The polar jet stream has repeatedly followed a path of steep ridges and toughs over North America, as illustrated here for the period of November 2013-July 2014. Map by NOAA Climate.gov, based on NCEP reanalysis data from NOAA ESRL. 
The jet stream is that powerful, high-altitude circulation system that carries weather around the Northern Hemisphere. The main fuel behind it is the difference in temperature between the Arctic and the warmer regions to the south.
“When the Arctic is warming so fast, that means there's less fuel driving the jet stream,” Francis says. “When the jet stream has less fuel it flows more slowly, and it tends to take these big north-south dips.” More

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