The Once and Future Battles of Thor and the Midgard Serpent, or: The Westerlies and the Antarctic Circumpolar Current in Global Climate

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Dominated by the Antarctic Circumpolar Current (ACC), the vast Southern Ocean can influence large-scale surface climate features on various time scales. Its climatic relevance stems in part from it being the region where most of the transformation of the World Ocean’s water masses occurs. In climate change experiments that simulate greenhouse gas–induced warming and ozone depletion, the response of the Southern Ocean circulation patterns to the change in the Westerlies make it a region where much of the future oceanic heat storage takes place, though the magnitude of that heat storage is one of the larger sources of uncertainty associated with the transient climate response in such model projections. These links are explored here in a climate model context by analyzing a suite of experiments produced in support of the Intergovernmental Panel on Climate Change’s Fourth Assessment Report. The influence of the predicted change in Southern Ocean circulation over the rate of global atmospheric warming will be examined, as well as potential impacts on polar and global marine ecosystems.