Intellectual merit: Because changes in ocean circulation have profoundly influenced climate in the past, this research addressed the fundamental role that ocean circulation plays in the regulation of CO2. The work uses radiocarbon in foraminifera tests deposited in sediments off New Zealand to examine how global ocean circulation affects the partitioning of the greenhouse gas CO2 between the ocean and atmosphere. This research has two primary goals: (1) to reconstruct the radiocarbon signature of the glacial southern Pacific to confirm or refute the presence of a deep water mass old enough to account for the glacial?interglacial changes in atmospheric CO2 and (2) to produce a high resolution record of radiocarbon at various intervals the time of deglaciation to provide a Southern Hemisphere perspective which is missing from global CO2 and radiocarbon budgets. These issues can be addressed because ocean circulation can be traced with radiocarbon (14C) because there is a quantifiable difference between the 14C content of atmospheric CO2 gas and that in the ocean where it exists in the form of dissolved carbonate and bicarbonate, This is because there is an equilibrium balance between 14C in the atmosphere and the radioactive decay of 14C in isolated water masses during thermohaline circulation. The research takes advantage of the precise stratigraphic control afforded by volcanic ask layers in cored off-shore sediments from different water depths. Planktonic and benthic foraminiferal pairs will be used to construct vertical profiles of radiocarbon at different depths in the ocean and a time series of set of oxygen isotope data will be collected to track the evolution of changes in shallow waters (600?2500 m) and deep waters (600-4300m) through the time of the last period of deglaciation (17,500 to 9,500 years ago.
Broader impacts Collaborations among United States and New Zealand scientists represent significant investment outreach with international colleagues by US investigators addressing the criteria of enhancing infrastructure for research. The team includes a young investigator with no prior NSF funding and the exchange of a graduate student among the investigators' institutions, addressing criteria for advancing training and learning.
