The climate is changing: the Arctic Dipole emerges The dramatic
loss of Arctic sea ice in recent years has created a fundamental
new change in the atmospheric circulation in the Northern
Hemisphere that has sped up sea ice loss and is affecting fall
and winter weather across most of the Northern Hemisphere,
according to several recent studies. Arctic sea ice loss peaks
in September and October, exposing a large area of open water
that heats the air above it. This extra heat has helped drive
September - November air temperatures in the Arctic to 1°C
(1.8°F) or more above average over about half of the depth of
the lower atmosphere (Figure 1). This deep layer of warm air has
grown less dense and expanded, pushing the top of the
troposphere (the lower atmosphere) higher. The result has been a
decrease in the pressure gradient (the difference in pressure)
between the North Pole and mid-latitudes. With not as much
difference in pressure to try and equalize, the jet stream has
slowed down in the Arctic, creating a