New Insight Into The Disappearing Arctic Sea Ice - American Geophysical Union

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Volume 87 Number 48 14 November 2006

The dramatic loss of Arctic sea ice is ringing alarm bells in the minds of climate scientists,
policy makers, and the public. The extent of perennial sea ice—ice that has survived a
summer melt season—has declined 20% since the mid-1970s . Its
retreat varies regionally, driven by changes in winds and heating from the atmosphere and
ocean.

Limited data have hampered attempts to identify which culprits are to blame, but new
satellite-derived information provides insight into the drivers of change. A clear message
emerges. The location of the summer ice edge is strongly correlated to variability in
longwave (infrared) energy emitted by the atmosphere (downward longwave flux; DLF),
particularly during the most recent decade when losses have been most rapid. Increasing
DLF, in turn, appears to be driven by more clouds and water vapor in spring over the Arctic.

Reduced ice in spring and summer is important to the climate system because the
timing coincides with strongest insolation, of which ice is an excellent reflector. If enough
ice is lost to allow sufficient extra heat into the Arctic Ocean, such that some can remain
through the winter and reduce ice thickness the following spring, the so-called ice-albedo
feedback will accelerate the loss of ice . Recent accelerating
declines in summer and winter ice extent suggest this threshold has been crossed.
Integrated anomalies in winds and heating over months prior to maximum ice retreat
are likely the primary drivers of ice edge location. New satellite products—downward
longwave and shortwave fluxes (DLF, DSF), zonal and meridional winds (U,V), and temperature
advection (ADV)—provide tools to investigate causes for ice loss.

EDIT

Regional time series of MIAs (Figure 1b) reveal large interannual variability everywhere,
with statistically significant (>99% confidence) trends in the Chukchi and Beaufort seas of
168 and 113 kilometers per decade, respectively. Relationships between MIAs and individual
forcing anomalies are predominantly linear; DLF anomalies are consistently positively
correlated with ice retreat, while DSF anomalies are consistently negatively correlated.
This implies that variability in solar fluxes, owing primarily to varying cloud
opacity, is overwhelmed by opposing changes in emitted longwave radiation. Because DSF
anomalies apparently do not drive MIAs, they are excluded from further analysis.

EDIT

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[phantom power]

1. If "policy makers" are hearing any alarm bells...

they have a peculiar way of showing it.