Abstract

Amplified warming has recently occurred in the Arctic and is linked with dramatic declines in Arctic sea-ice and mass loss of the Greenland Ice Sheet. At the same time, over the last decade, there has been a notable clustering of extreme weather events in the Northern Hemisphere mid-latitudes, which in the UK (and wider north-west Europe) has included at times record cold/snowy winter weather, and at other times unusually wet, stormy winters, as well as some record wet summer spells. Unusually cold and snowy winter weather was also often seen in the eastern US and in Siberia, while Greenland experienced record warmth in summer 2012, leading to a record surface melt and mass loss of its ice sheet. In the UK and wider Northwest Europe there has been a notable increase in the year-to-year variability of winter weather conditions over the last few decades (sometimes cold and snowy, sometimes wet and stormy), which reflects an striking shift in the atmospheric polar jet stream over the North Atlantic. In summer there has been a significant increase in high-pressure blocking over Greenland in the last 10-20 years, which is linked to a more southerly average jet-stream flow. This lecture will explore how these recent changes in Arctic climate and extreme weather further south may be linked through jet-stream changes. There is a tendency at times for a more amplified (north-south waving) jet-stream flow, which encourages greater exchanges of air masses between mid and high latitudes and is sometimes related to more stationary and persistent mid-latitude weather patterns. Continued global warming through human-enhanced greenhouse gases will most likely spring further surprises. Therefore we will conclude by exploring how mid-latitude extreme weather may respond to continued Arctic climate change during the rest of the Twenty First Century.