In this project researchers at the Woods Hole Oceanographic Institution and the University of Washington will attempt to develop a method to evaluate anthropogenic changes in the carbon isotopic composition (d 13C) of dissolved inorganic carbon (DIC)in the oceans, the so-called 13C Suess effect. Development of this method should permit reconstruction of the d 13C-DIC and DIC Suess effect globally using both the new WOCE/JGOFS/OACES d 13C-DIC and DIC datasets. These reconstructions will provide, for the first time, global coverage of (1) the relationship between the anthropogenic 13CO2 and 12 CO2 changes, ( 2) the total d 13C of DIC change in the oceans, and (3) the pre-industrial d 13C of DIC distribution. The reconstructions should also be of immediate benefit to modelers of the modern-day global carbon cycle and to the paleoceanographic community.