Collaborative Research: Time Matters - A Comparison of Diatom 14C and Thermochemical 14C Dating Methods in Sediment Records of Ice Retreat from the East and West Antarctic Margins

海底覆盖着一层厚厚的泥浆，称为沉积物。随着时间的推移，海洋沉积物随着邻近大陆的碎片、大气尘埃和微小海洋生物的骨骼沉积在海底而积累。 随着沉积物在南极洲周围的海洋中积累，它记录了过去的环境条件，包括冰盖的行为，因为冰在最后一个冰河时代之后退缩。 科学家们使用各种化学分析来确定沉积物沉积在海底的时间，因此能够将冰盖行为与过去的特定时期联系起来。 然而，确定南极洲周围沉积物的年龄一直具有挑战性，因为沉积物往往缺乏可以通过传统方法确定年代的材料。在这个项目中，来自南佛罗里达大学和华盛顿大学的研究人员将测试新开发的南极大陆边缘沉积物年代测定方法，并改进自上一个冰河时代以来冰退缩的时间。最终，准确评估南极冰从海洋沉积物芯中撤退的时间将有助于更好地了解地球对不断变化的环境条件的反应。 该项目包括培养一名博士。南佛罗里达大学的学生，为佛罗里达州的教育工作者制作视频，并在一年一度的圣彼得堡科学节上进行公众宣传。 南极边缘沉积物很难准确地确定年代，因为通常在世界海洋中使用的海洋生物的碳酸钙外壳通常不会被保存下来。在这个项目中，来自南佛罗里达大学和华盛顿大学的研究人员专注于两项任务：1）分离热化学稳定性较低的碳（更可能来自与沉积物沉积年龄相同的碳）来自更稳定的碳（更可能是由冰川侵蚀从邻近大陆侵蚀而来）;和2）从海洋硅藻中分离特定的有机化合物，海洋硅藻是南大洋的初级生产者。 这项工作将使用以前从南大洋海底获得的沉积物芯样。 在所研究的每个沉积物岩心的每个深度层，科学家将使用已建立的放射性碳方法来测定这些新制备技术中每一种技术产生的碳的年代。这项工作将确定对缺乏碳酸盐的南极沉积物进行放射性碳测年的最佳做法，这将最终提高对影响过去和未来南极冰盖行为的因素的理解。

The seafloor is covered in a thick layer of mud called sediment. Ocean sediment accumulates over time as debris from adjacent continents, atmospheric dust, and the skeletons of microscopic marine organisms settle on the seafloor. As sediment accumulates in the oceans surrounding Antarctica, it records past environmental conditions including ice sheet behavior as the ice retreated following the last Ice Age. Scientists use a variety of chemical analyses to determine how long ago sediments were deposited on the seafloor, and are therefore able to relate ice sheet behavior to specific periods of time in the past. However, it has been challenging to determine the age of sediments around Antarctica, because the sediments often lack material that can be dated by conventional methods. In this project, researchers from the University of South Florida and the University of Washington will test newly developed methods for dating Antarctic continental margin sediments and refine the timing of ice retreat since the last Ice Age. Ultimately, accurately assessing the timing of Antarctic ice retreat from marine sediment cores will enable a better understanding of Earth's response to changing environmental conditions. This project includes training of a Ph.D. student at the University of South Florida, producing videos for educators in the state of Florida, and public outreach at the annual St. Petersburg Science Fest. Antarctic margin sediments are difficult to accurately date because the calcium carbonate shells of marine organisms that are typically used throughout the world's oceans to date sediments are not often preserved. In this project, researchers from the University of South Florida and the University of Washington focus on two tasks: 1) separating less thermochemically-stable carbon (more likely derived from carbon with an age equal to the depositional age of the sediment) from more stable carbon (more likely eroded from the adjacent continent by glacial erosion); and 2) isolating specific organic compounds from marine diatoms, which are primary producers in the Southern Ocean. The work will use previously collected samples in sediment cores obtained from the Southern Ocean seafloor. At each depth horizon in each sediment core studied, scientists will use established radiocarbon methods to date the carbon derived from each of these new preparation techniques. This work will determine the best practices in radiocarbon dating of carbonate-poor Antarctic sediments, which will ultimately improve understanding of the factors influencing past and future Antarctic ice sheet behavior.