Role of sea ice in forcing the winter climate of Antarctica in a global climate model

Two different experiments have been conducted using the Hadley Centre's atmosphere-only, global climate model to investigate the role of sea ice in forcing the Antarctic climate during the winter months. The first experiment, carried out by the Met Office Hadley Centre, involved forcing the model with observed sea ice concentration from the HadISST1 data set for the period 1870–1999 and showed that the observed temperature at Faraday/Vernadsky station (on the west coast of the Antarctic Peninsula) was well reproduced (correlation coefficient of 0.872) for the period 1973–1999, while at stations around the rest of the continent the observed temperature was not so highly correlated with the modeled temperature. The second experiment used two different yearly repeating sea ice concentrations, one being the average for the period 1975–1979 and the second the average for 1995–1999. The later period has generally less sea ice. This second experiment showed that the climate response to the sea ice forcing in the Amundsen Bellingshausen Sea was confined to the layers closest to the surface, while the response around the rest of Antarctica, where the katabatic wind flowing off the continent plays a role in the process, is over a much deeper layer of the atmosphere. It is also suggested that the katabatic flow may play a role in making the sea ice around East Antarctica insensitive to external climate forcing.

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