Arctic Sea Ice and the Potential for Abrupt Loss

The Arctic is covered by a perennial floating ice cap that waxes and wanes with the seasons. This ice cover has a strong influence on the surface energy budget and global hydrological cycle and hence is an important player in the global climate system. Since satellite monitoring began in 1979, the Arctic sea ice cover has shown dramatic retreat, particularly in summer. Climate models project this retreat to continue into the future because of rising greenhouse gas loading in the atmosphere. Studies suggest that this retreat could be abrupt relative to the forcing, which has implications for the ability of societies and ecosystems to adapt to this change. The potential for abrupt sea ice loss is consistent with the amplifying effect of sea ice variations and the dependence on an inherent freezing temperature threshold. However, it remains unclear whether recent changes and projected losses through the next century are indicative of tipping point behavior or more simply result from increasing anthropogenic forcing combined with large intrinsic variability.