Here’s the latest from EarthNow…

Extreme weather in the Northern Hemisphere is increasingly blamed on Arctic Amplification. What is Arctic Amplification and how does it affect our weather?

The display first shows a satellite image of Arctic sea ice from September 1980. Ice is colored white. The temperature differences between the cold poles and warm tropics, combined with the Earth’s rotation, cause air to flow eastward fastest over the midlatitudes, where most of us live. This is called the jet stream and is shown here in red and blue. 

Approaching North America, the jet stream moves northward over the Rocky Mountains, then dips southward forming a trough toward the East Coast, then northward as a ridge over the Atlantic Ocean. It continues in a similar long wave pattern over Europe, Asia, and the Pacific. Storms develop and track along the jet stream, pushing cold air south (blue portions of jet stream) and warm air north (red portions of jet stream).

Now the display shows the recent Arctic sea ice from September 2012, the lowest ice extent ever recorded by satellites. The current typical jet stream location is now shown, with the previous ice extent and jet stream location typical of 30 years ago shown in pink for comparison. 

During the past few decades, general warming in the atmosphere has accelerated Arctic ice melt, leading to more seasonal ice cover which is not as white and absorbs more sunlight, in turn causing more warming. The Arctic has warmed twice as fast as the rest of the Northern Hemisphere. This is Arctic Amplification.

Scientists have observed that the reduced temperature difference between the North Pole and tropics is associated with slower west-to-east jet stream movement and a greater north-south dip in its path. This pattern causes storms to stall and intensify, rather than move away as they normally used to do. At midlatitudes, more extreme weather results from this new pattern, including droughts, floods, colds spells, and heat waves. 

That’s how Arctic Amplification is affecting our weather.