Collaborative Research: Temperature Dependent Magnesium Isotope Fractionation in Marine Carbonates

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Initial data obtained by scientists from Yale University and Woods Hole Oceanographic Institution indicates a clear temperature-dependent fractionation of d26Mg in aragonitic coral skeletons and the absence of "vital effects". For this reason, this team of scientists plan to carry out laboratory precipitation and coral culturing experiments to develop and apply a new paleothermometer based on the temperature-dependent fractionation of magnesium (Mg) isotopes between fluid and biogenic carbonates. The goals of the work is threefold: (1) determine experimentally Mg isotope fractionation factors as a function of temperature for both aragonite and calcite precipitated from seawater over a wide range of temperature (5-50 C), crystal growth rate, pH, and salinity; (2) establish the temperature dependent Mg isotope fractionation between coral skeleton and seawater, and conduct further tests for potential species dependencies, growth rate dependencies and other "vital effects"; and (3) apply the d26Mg thermometer to reconstruct Atlantic SSTs during the Little Ice Age ~400 years ago. As regards broader impacts, corals would be used to reconstruct past temperature of the ocean using a novel approach, thereby providing the science community with a viable means of extending the instrumental record. One graduate student from Yale University would be supported and trained as part of this project.