Quantifying the 18O/16O of Glacial Meltwater Pulses Using a Novel LA-ICPMS/IRMS Multiproxy Approach

末次冰期北美大陆大冰原的生长和消融对气候和海洋环流产生了深远的影响。冰川消融期间流入海洋的融水导致海平面上升，并被认为是气候迅速变化的一个原因。然而，单个融水脉冲的相对体积贡献很难限制，并且通常依赖于对北美（劳伦泰德）冰盖融水地球化学稳定同位素组成的假设。事实上，冰原本身具有不均匀的成分，在时间和空间上都是不同的，这使得重建成为一项挑战。这项研究是由加州大学戴维斯分校的科学家进行的，他们开发了一种新技术来确定北美冰盖融水的瞬时氧同位素组成。测量微量元素（Mg/Ca和Ba/Ca）和氧同位素（δ18O）组成将对保存在墨西哥湾沉积物中的浮游有孔虫的单个壳进行测量。该项目的具体目标是：1)完善样品制备和测量方案，2)改进Ba/Ca盐度代理的校准，3)通过使用新方法计算现代密西西比河水来测试该技术，以及4)计算脱冰（终止I）和海洋同位素阶段3的选定间隔期间河流/融水的氧同位素组成。就更广泛的影响而言，资金支持女性博士候选人，并为本科生提供接触最先进分析方法的机会。该方法在古海洋学研究中具有广泛的应用前景。

The growth and decay of large ice sheets over the North American continent during the last glacial period had far reaching effects on climate and ocean circulation. Meltwater input into the oceans during deglaciation caused sea level to rise and has been invoked as a cause for rapid climate change. However, the relative volumetric contributions of individual meltwater pulses has been difficult to constrain, and often relies on assumptions about the stable isotope composition of the North American (Laurentide) ice sheet meltwater geochemistry. The fact that the ice sheets themselves had heterogeneous compositions, varying in both time and space, makes reconstruction a challenge.This research, carried out by scientists at the University of California at Davis, develops a novel technique to determine the instantaneous oxygen isotope composition of meltwater from the North American ice sheet. Measurements of both trace element (Mg/Ca and Ba/Ca) and oxygen isotope (δ18O) composition will be made on individual shells of planktonic foraminifera preserved in sediments of the Gulf of Mexico. Specific goals of the project are to: 1) refine the sample preparation and measurement protocols, 2) improve the calibration of the Ba/Ca salinity proxy, 3) test the technique by computing modern Mississippi River water using the new method, and 4) compute the oxygen isotope composition or river/meltwater during selected intervals of the deglaciation (Termination I) and Marine Isotope Stage 3. In terms of broader impacts, funding supports a female doctoral candidate and offers the opportunity for undergraduates to be exposed to state of the art analytical methods. The methods developed in the course of this work method could potentially be widely applied in paleoceanographic studies.