The convective circulation of the world's ocean exerts important controls on two key aspects of the climate system: the transport of heat around the Earth and the degree to which the oceans sequester greenhouse carbon dioxide away from the atmosphere. Models of the past circulation predict variations in its strength that have been implicated in climate change. Marine sediments record changes in ocean chemistry that can be used to test these models. This approach has been pursued with great success in the North Atlantic. The Southern Ocean, on the other hand, is much less studied because of a lack of suitable sediments that record ocean chemistry. And yet, the Southern Ocean and its circulation system may be the key to both heat transport and isolation of a deep ocean carbon reservoir. This proposal seeks to provide key constraints on some of these issues using a unique set of deep-sea coral samples from the Pacific sector (70°S) of the Southern Ocean provided by the British Antarctic Survey and the Alfred Wegener Institute. Specifically we aim to use the radiocarbon ages of the corals, coupled with their calendar ages, to investigate the degree of isolation of the deep Southern Ocean carbon reservoir from the atmosphere, and therefore the extent to which this isolation might explain low atmospheric CO2 during recent glacial periods in Earth history. We also seek to use them to provide basic chemical information on the deep Southern Ocean, information that is key to many studies that use the chemistry of the past North Atlantic Ocean to try to understand ocean circulation.