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，文石珊瑚骨架中的d26 mg明显随温度变化而分馏，不存在“生命效应”。为此，这组科学家计划进行实验室降水和珊瑚培养实验，以开发和应用一种新的古温度计，该温度计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。这项工作的目标有三个：(1)在广泛的温度范围(5-50摄氏度)、晶体生长速度、pH和盐度范围内，通过实验确定从海水中沉淀的文石和方解石的镁同位素分馏系数作为温度的函数；(2)建立珊瑚骨架和海水之间依赖温度的镁同位素分馏，并对潜在的物种依赖性、生长速率依赖性和其他“重要影响”进行进一步测试；(3)应用d26 MG温度计重建约400年前小冰期期间的大西洋SSTs。至于更广泛的影响，将利用珊瑚以一种新的方法重建过去的海洋温度，从而为科学界提供一种扩展仪器记录的可行手段。耶鲁大学的一名研究生将作为该项目的一部分得到支持和培训。

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.