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(c) Tim Cronin, MIT

How the Arctic warms within days and over decades

Dr Felix Pithan | AWI - Alfred-Wegener-Institut | Helmholtz-Zentrum für Polar- und Meeresforschung | Bremerhaven

Abstract: Global warming is known to be amplified in the Arctic because of strong
positive feedbacks that are specific to high latitudes: As snow and ice
melt, more sunlight is absorbed at the surface in summer (surface albedo
feedback), and surface warming, especially in winter, is concentrated in
the lowest levels, which makes it harder for additional energy to escape
to space (lapse-rate feedback).
In recent years, wintertime warm events with temperatures near the
freezing point around the North Pole have attracted public and
scientific attention. These events are caused by intrusions of warm,
moist mid-latitude air into the central Arctic that lead to development
of cloud liquid, which in turn shields the surface from cooling to space
through the otherwise very transparent Arctic atmosphere.
In this talk, I will give an overview of recent research into the
transformation of air masses that enter or leave the Arctic, discuss how
these events are connected to the feedbacks driving Arctic amplification
of climate change and how the events themselves will change in a warming
climate. Processes ranging from boundary-layer turbulence and cloud
microphysics over radiation and the development of high-pressure systems
to rossby-wave breaking and sudden stratospheric warmings interact to
generate and control these air mass transformations. Activities within
and beyond the ongoing year of polar prediction will provide us with
fascinating, unprecedented insights into these processes in the next few
years.