The assessment of the potential for recent Arctic changes to influence broader hemispheric weather is a difficult and controversial topic, with considerable skepticism. There is little agreement on problem formulation, methods, or robust mechanisms in the research community.
The topic, however, is a major science challenge, as continued Arctic changes are an inevitable aspect of anthropogenic global change and is an opportunity for improved extended range forecasts at mid-latitudes. An intriguing and increasingly important question from scientists and the broader community is whether recent extreme weather in North America, eastern Asia and northern Europe were merely random events or were related to recent global or Arctic climate change. CliC, the Atmospheric Working Group of IASC, other IASC Working Groups and multiple programs have prioritized the challenge: CliC, WMO/Polar Prediction, NOAA, UK Met Office, and the Icelandic Met Office.
Following an IASC/CliC workshop in Iceland in November 2013, a smaller group met in Seattle during September 2014 to address the difficult topic of the current state of the science. A manuscript has been submitted to Journal of Climate and 28 abstracts on linkages and related topics have been submitted to the ASSW/ICARP III/ISAR session in Japan April 2015. Seattle suggested a way forward through case studies of regional episodic mechanisms.
Two candidates for linkages are increased Siberian high pressure and wave trains of high/low pressures that bring cold air into eastern Asia, and an amplification of the North American ridge/trough structure related to Greenland blocking (a slowing of the wind pattern) affecting cold weather in eastern North America. The abstract and a key figure from the paper submitted to J. Clim. are reproduced on the right.
This topic was represented by an ASSW/ICARP III/ISAR session in Japan April 2015, convened by Jim Overland (Edward Hanna, representing CliC, is a co-convenor). Linkages will continue to be an important topic moving forward in the next few years to decades, so we anticipate that occasional meetings and author workshops will prove fruitful.