Using the set of simulations performed with atmosphere-ocean general circulation models (AOGCMs) for the Fourth Assessment Report of the International Panel on Climate Change (IPCC AR4), the projected regional distribution of sea ice for the 21st century has been investigated. Averaged over all those model simulations, the current climate is reasonably well reproduced. However, this averaging procedure hides the errors from individual models. Over the 20th century, the multimodel average simulates a larger sea-ice concentration decrease around the Antarctic Peninsula compared to other regions, which is in qualitative agreement with observations. This is likely related to the positive trend in the Southern Annular Mode (SAM) index over the 20th century, in both observations and in the multimodel average. Despite the simulated positive future trend in SAM, such a regional feature around the Antarctic Peninsula is absent in the projected sea-ice change for the end of the 21st century. The maximum decrease is indeed located over the central Weddell Sea and the Amundsen-Bellingshausen Seas. In most models, changes in the oceanic currents could play a role in the regional distribution of the sea ice, especially in the Ross Sea, where stronger southward currents could also be responsible for a smaller sea-ice decrease during the 21st century. Finally, changes in the mixed layer depth can be found in some models, inducing locally strong changes in the sea-ice concentration.

Last Updated: 2007-02-26