Foraminiferal magnesium to calcium ratios (Mg/Ca) are an important and widely used tool in studies of past ocean temperatures. Recent research suggests that variations in salinity could have a greater influence on Mg/Ca paleothermometry than previously believed, with significant implications for interpretations of paleotemperature data. The magnitude of that influence, however, remains under debate. The proposed work, led by researchers at UC Santa Barbara, aims to resolve this problem using a three-pronged approach to quantify the influence of salinity on foraminiferal Mg/Ca: 1) analysis of sediment trap and core-top samples from three regions with large salinity gradients (Arabian Sea, Bay of Bengal, and northwest Africa); 2) synthesis of available sediment trap, core-top, and plankton tow data from low latitudes; and 3) assessment of secondary diagenetic effects on foraminiferal Mg/Ca in high-salinity regions. Comparative and multivariate techniques will be used to evaluate the magnitude of the salinity influence relative to other known influences (e.g., temperature, seasonality, seafloor dissolution) on foraminiferal Mg/Ca.
This research will lead to increased confidence in reconstructions of past temperature and, consequently, in model assessments of climate sensitivity. Knowledge and data sharing will be facilitated by the development of a searchable foraminiferal Mg/Ca database. The project will team a senior faculty member with a junior faculty member who is a member of an underrepresented group, and will provide support for a post-doctoral researcher.
