Mg/Ca thermometry of planktonic foraminifera and application to paleoceanography

Abstract

Planktonic foraminiferal Mg/Ca thermometry has been used in reconstructing past surface-ocean temperature from deep-sea sediments. Mg/Ca paleothermometry has the advantages of enabling reconstructions of past temperature with a precision of ±1° and reconstructions of salinity when combined with oxygen isotope measurements of foraminiferal shell. Previous paleoceanographic studies that employed this method have shed light on the important role of oceanic variability in global climate change at various time scales. However, the method has some limitations, including the fact that carbonate dissolution in the deep sea modifies the Mg/Ca value of foraminifera. The application of Mg/Ca thermometry to paleoceanographic studies, taking into account its basis and limitations, represents a powerful tool in terms of understanding the global climate system. This paper summarizes the principles, applications to paleoceanography, problems, and perspectives of Mg/Ca thermometry.