This project will calibrate and validate shell-derived d18Oseawater estimates that have been derived from paired analyses of Mg/Ca and d18O in planktonic foraminifera against observed d18Oseawater gradients for three meridional coretop transects in the (sub)tropical Pacific, Atlantic, and NW African margin. In addition, an in situ d18Oseawater calibration will be conducted using plankton tow and d18Oseawater surface water samples collected during a recent coring cruise off the Portuguese and NW African margins. The research will test the hypothesis that the "excess Mg/Ca" that he has observed in a series of 58 coretop samples, and its apparent link to salinity, can be isolated and quantified over a larger (sub)tropical ocean domain. This research will also examine systematic changes in foraminifera shell morphology, weight, and shell Mg/Ca heterogeneity associated with "excess Mg/Ca" endmember samples. The Broader Impacts component of this project include support of a PhD student, involvement and mentoring of undergraduate students in elements of the research, and the study of a transformative-level problem that is a fundamental component of many ongoing paleoceanographic research programs.
