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Abstract

A recent increase in mid-latitude extreme weather events has been linked to Northern
Hemisphere polar jet stream anomalies. To put recent trends in a historical perspective, longterm
records of jet stream variability are needed. Here we combine two tree-ring records
from the British Isles and the northeastern Mediterranean to reconstruct variability in the
latitudinal position of the high-summer North Atlantic Jet (NAJ) back to 1725 CE. We find
that northward NAJ anomalies have resulted in heatwaves and droughts in northwestern
Europe and southward anomalies have promoted wildfires in southeastern Europe. We further
find an unprecedented increase in NAJ variance since the 1960s, which co-occurs with
enhanced late twentieth century variance in the Central and North Pacific Basin. Our results
suggest increased late twentieth century interannual meridional jet stream variability and
support more sinuous jet stream patterns and quasi-resonant amplification as potential
dynamic pathways for Arctic warming to influence mid-latitude weather.