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，称为沉淀物。海洋沉积物随着时间的推移而积累，因为来自邻近大陆的碎片、大气尘埃和微小海洋生物的骨骼定居在海底。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，包括冰盖在上一个冰河时代之后消退时的行为。科学家使用各种化学分析来确定沉积物是在多长时间前沉积在海底的，因此能够将冰盖行为与过去的特定时间段联系起来。然而，确定南极洲周围沉积物的年龄一直是一个挑战，因为这些沉积物往往缺乏可以用传统方法测定年龄的物质。在这个项目中，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，并完善自上一个冰河时代以来冰川消退的时间。最终，准确评估南极冰层从海洋沉积核心退缩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。该项目包括培训南佛罗里达大学的一名博士生，为佛罗里达州的教育工作者制作视频，以及在一年一度的圣彼得堡科学节上进行公众宣传。南极边缘的沉积物很难准确测年，因为世界各地海洋中通常使用的碳酸钙贝壳通常不会被保存下来。在这个项目中，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)从较稳定的碳(更有可能来自年龄等于沉积物沉积年龄的碳)和较稳定的碳(更有可能是被冰川侵蚀的邻近大陆侵蚀的碳)中分离出热化学稳定性较低的碳；以及2)从海洋硅藻中分离特定的有机化合物，硅藻是南大洋的主要生产者。这项工作将使用以前从南大洋海底获得的沉积物岩芯中收集的样本。在每个被研究的沉积物岩心的每一个深度层，科学家们将使用现有的放射性碳法来确定从每一种新的制备技术中获得的碳的年代。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，这最终将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.