Collaborative Research: Temperature Dependent Magnesium Isotope Fractionation in Marine Carbonates

耶鲁大学和伍兹霍尔海洋研究所的科学家获得的初步数据表明，文石珊瑚骨骼中d26 Mg的分馏明显与温度有关，而且没有“生命效应”。 为此，该科学家团队计划进行实验室降水和珊瑚培养实验，以开发和应用基于流体和生物碳酸盐之间镁（Mg）同位素随温度变化的分馏的新古温度计。 本工作的目标有三：（1）在较宽的温度（5-50 ℃）、晶体生长速率、pH和盐度范围内，实验测定海水中沉淀的文石和方解石的Mg同位素分馏因子随温度的变化;（2）建立了珊瑚骨骼与海水之间Mg同位素分馏的温度依赖关系，并进一步检验了可能的种间依赖关系，（3）应用d26 Mg温度计重建400年前小冰期大西洋SST。 至于更广泛的影响，将采用一种新的方法，利用珊瑚来重建海洋过去的温度，从而为科学界提供一种扩大仪器记录的可行手段。 作为该项目的一部分，将支助和培训一名耶鲁大学的研究生。

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.