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

使用新型 LA-ICPMS/IRMS 多代理方法量化冰川融水脉冲的 18O/16O

• 批准号: 1061676
• 负责人: Howard Spero
• 金额: $ 35.96万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-06-01 至 2016-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1061676&HistoricalAwards=false
• 关键词: Quantifying; 18O; 16O; Glacial; Meltwater

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.

末次冰期北美大陆大冰盖的生长和衰减对气候和海洋环流产生了深远的影响。冰川消退期间融水流入海洋导致海平面上升，并被认为是气候迅速变化的原因。然而，个别融水脉冲的相对体积的贡献一直难以约束，往往依赖于北美（Laurentide）冰盖融水地球化学的稳定同位素组成的假设。事实上，冰盖本身具有异质成分，在时间和空间上都有变化，这使得重建成为一项挑战。这项由加州大学戴维斯分校的科学家进行的研究开发了一种新技术，可以确定北美冰盖融水的瞬时氧同位素组成。 微量元素（镁/钙和钡/钙）和氧同位素（#948; 18 O）的组成的测量将在墨西哥湾的沉积物中保存的浮游有孔虫的个别外壳。该项目的具体目标是：1）完善样品制备和测量协议，2）改进Ba/Ca盐度代用品的校准，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）计算冰消（终止I）和海洋同位素阶段3的选定间隔期间的氧同位素组成或河流/融水。就更广泛的影响而言，资金支持一名女博士候选人，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。