The PI will measure late glacial through Holocene 231Pa/230Th in a depth transect of cores on the Blake Ridge in the western North Atlantic, with the objective of understanding the mechanisms that control these radioisotopes and their relationship to sediment flux and deposition. The PI argues that this would allow a better use of the Pa-Th method to evaluate the changes in the Atlantic Meridional Overturn Circulation between glacial times and the present. Currently the data relevant to this problem are scattered and thus difficult to interpret. Broader impacts: In addition to promoting better understanding of climate and ocean circulation systems the project will also support teaching, training and learning. A strong outreach element is also a part of the project.