[asa] What drove the dramatic retreat of arctic sea ice in summer 2007?

http://www.agu.org/pubs/crossref/2008/2008GL034005.shtml

A model study has been conducted of the unprecedented retreat of arctic sea
ice in the summer of 2007. It is found that preconditioning, anomalous
winds, and ice-albedo feedback are mainly responsible for the retreat.
Arctic sea ice in 2007 was preconditioned to radical changes after years of
shrinking and thinning in a warm climate. During summer 2007 atmospheric
changes strengthened the transpolar drift of sea ice, causing more ice to
move out of the Pacific sector and the central Arctic Ocean where the
reduction in ice thickness due to ice advection is up to 1.5 m more than
usual. Some of the ice exited Fram Strait and some piled up in part of the
Canada Basin and along the coast of northern Greenland, leaving behind an
unusually large area of thin ice and open water. Thin ice and open water
allow more surface solar heating because of a much reduced surface albedo,
leading to amplified ice melting. The Arctic Ocean lost additional 10% of
its total ice mass in which 70% is due directly to the amplified melting and
30% to the unusual ice advection, causing the unprecedented ice
retreat.*Arctic sea ice has entered a state of being particularly
vulnerable to
anomalous atmospheric forcing.* [emphasis mine]

The fact that much of the current ice is first-year ice makes 2008 a
possible repeat of 2007. Note this quote of Dr. Mark Serreze of the US
National Snow and Ice Data Center in Boulder, Colorado as quoted by the
Independent:

The issue is that, for the first time that I am aware of, the North Pole is
> covered with extensive first-year ice – ice that formed last autumn and
> winter. I'd say it's even-odds whether the North Pole melts out [in
> September 2008].

*Whoa.*

Rich Blinne
Member ASA

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Received on Fri Jun 27 17:04:00 2008