Warming Arctic, wavy jet stream and extreme weather

Evidence getting stronger

A new study, published in Nature Geoscience, adds to the growing evidence that record-breaking extreme weather events have been influenced by human-induced climatic changes in the Arctic

Jong-Seong Kug et al (2015) used observations and modeling to investigate potential connections between extreme cold winter weather over North America and East Asia last winter and historically low levels of summer sea ice in the Arctic Ocean. They found that the reduced extent of summer sea ice in the Barents-Kara Sea region influenced cold weather in East Asia, while harsh winters in North America related to warmer temperatures in the East Siberian-Chukci Sea region.

Warm conditions in these areas of the Arctic Ocean weakens the polar jet stream (stream of high-speed winds flowing west to east high up in the atmosphere) which is driven by temperature differences between the Arctic and the equator. This, in turn, makes the jet stream pattern more wavy, creating ridges and blocking weather systems so that cold (or hot) conditions get stuck over a longer time period. Which leads to more extreme weather events.

"As we watch the Arctic continue to warm and melt - with regional differences from one year to the next - the research presented by Kug et al may provide early warning of extreme winter weather in heavily populated areas of the northern hemisphere, thereby saving energy and lives" says researcher Jennifer Francis in an interview with the Carbon Brief.

These changes to jet stream patterns are believed to be responsible for Californias long standing drought conditions and record cold winters in eastern United States. This summer parts of Alaska experienced really warm weather that lead to major forest fires, and some 30 whales washed up dead on their shores. Probably due to warmer waters and loss of food supply (krill).
The jet stream, which once used to move over North America horizontally, has become more wavy, pushing warm air north on the left, while drawing cold air from the Arctic south on the right. Source: Arctic News blog
It also influences weather patterns in Europe, causing record  floodings and storms in the UK and warmer weather in central Europe, this year leading to a record drought (loss of soil moisture) that negatively impacted crop yields.

Omega wind heatwave June 28- July 04, 2015. Credit: NOAA


Out of the ashes into the fire

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