Summary
The area surrounding the Antarctic that is annually covered by sea ice is one of the most conspicuous and well-defined oceanic regions on the planet. In winter, 19 million km2 are ice-covered and in summer only 4 million km2 of sea ice remains. The annual formation of sea ice around the Antarctic has a significant impact on the oceanography of the Southern Ocean and affects global ocean circulation, particularly through the formation of dense Antarctic bottom water. Sea ice also profoundly influences the ecology of the Antarctic region both directly and indirectly. Sea ice is a habitat for organisms, but through its formation and melting, it also modifies the oceanic environment in ways which can alter productivity. As one of the most profound seasonal changes on the planet, the formation and decay of sea ice has a major role in climate processes and is also likely to be impacted by climate change, which in turn has the potential to change the productivity of the Antarctic region. The sea ice zone has supported enormous populations of animals, particularly large vertebrates such as seals, seabirds and whales that in turn have been heavily exploited often to near extinction. Future changes in the productivity of the region will not only have an impact on the sustainable harvesting of the region’s remaining harvestable species – fish and krill – but may well affect the recovery of species which have been over-exploited in the past. This review focuses on the current state of knowledge of the sea ice zone; examines the potential for both climatic and ecological change in the region, and in the context of changes already documented for vertebrates such as seals and seabirds; discusses the potential effects on the largest and most conspicuous vertebrate species of the region, baleen whales.