Because animals and humans respond to seasonally
and regionally varying climates, it is instructive to assess
how much confidence we can have in regional projections
of sea ice from the 20 models provided through the
International Panel on Climate Change Fourth Assessment
Report (AR4) process (IPCC 2007). Based on the selection
of a subset models that closely simulate observed regional
ice concentrations for 1979–1999, we find considerable
evidence for loss of sea ice area of greater than 40% by
2050 in summer for the marginal seas of the Arctic basin.
This conclusion is supported by consistency in the selection
of the same models across different regions, and the
importance of thinning ice and increased open water at
mid-century to the rate of ice loss. With less confidence, we
find that the Bering, Okhotsk and Barents Seas have a
similar 40% loss of sea ice area by 2050 in winter. Baffin
Bay/Labrador shows little change compared to current
conditions. These seasonal ice zones have large interannual/
decadal variability in addition to trends. Large model-tomodel
differences were seen for the Kara/Laptev Seas and
East Greenland. With a careful evaluation process, AR4 sea
ice projections have some utility for use in assessing
potential impacts over large Arctic subregions for a 2020–
2050 time horizon.

Last Updated: 2007-09-20