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，叫做沉积物。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架沉淀在海底而积累。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，包括上一个冰河时代后冰消退时的冰盖行为。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，因此能够将冰盖的行为与过去特定时期联系起来。然而，确定南极洲周围沉积物的年龄一直具有挑战性，因为沉积物通常缺乏可以用传统方法确定年代的物质。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方法，以确定南极大陆边缘沉积物的年代，并精确确定上一次冰河时代以来冰川退缩的时间。最终，准确地评估南极冰层从海洋沉积物岩心退缩的时间将使我们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。南极边缘沉积物的准确年代很难确定，因为通常在世界海洋中用来测定沉积物年代的海洋生物的碳酸钙壳通常没有被保存下来。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)将热化学稳定性较差的碳（更可能来自年龄与沉积物沉积年龄相等的碳）与较稳定的碳（更可能来自邻近大陆的冰川侵蚀）分离开来；2)从海洋硅藻中分离出特定的有机化合物，硅藻是南大洋的主要生产者。这项工作将使用先前从南大洋海底获得的沉积物岩心中收集的样本。在研究的每个沉积物岩心的每个深度层，科学家们将使用现有的放射性碳方法来确定每种新制备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定年的最佳做法，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.