Postdoctoral Fellowship: OPP-PRF: Tracing Polar Sediments with Short-lived Radioisotopes in 75 years of Arctic and Antarctic Sediment Cores

博士后奖学金：OPP-PRF：用 75 年北极和南极沉积物核心中的短寿命放射性同位素追踪极地沉积物

• 批准号: 2317997
• 负责人: Molly Keogh
• 金额: $ 30.06万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-11-15 至 2025-10-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2317997&HistoricalAwards=false
• 关键词: Postdoctoral; Fellowship; OPP; PRF; Tracing

Climate change is disproportionately affecting polar regions, with the Arctic now warming nearly four times faster than the global average. Polar warming drives coastal erosion and increases sediment delivery to the coastal ocean, affecting ecosystem processes ranging from primary productivity to carbon sequestration. Tracking changes in sedimentation rate is urgently needed to determine current conditions and measure further change. In polar regions, however, two of the most globally reliable sediment tracers, the radioisotopes lead-210 (210Pb) and cesium-137 (137Cs), have yielded mixed results. To understand the distribution and usefulness of these radioisotopes at high latitudes, this research makes use of a wealth of polar sediment cores archived at the Oregon State University Marine and Geology Repository combined with data synthesized from the literature. Results provide the first systematic study of Arctic and Antarctic sediment accretion. Improving the tools we use to track changes in sedimentation will help coastal managers and decisionmakers understand how climate change is impacting polar coastlines and marine environments, and what local communities should expect in the future.Sediment cores will be subsampled and analyzed for the activities of 210Pb (half-life = 22.3 years) and 137Cs (half-life = 30.1 years) using alpha and gamma spectroscopy, respectively. To provide context related to depositional environment, select subsamples will also be analyzed for sediment bulk density, grain size distribution, and organic content. A subset of samples with no measurable 210Pb or 137Cs activity will be analyzed for 14C to determine whether the lack of radioisotopes in a sample is because the core is simply too old, the true surface layer is missing, or because the shorter-lived radioisotopes did not accumulate. By undertaking comprehensive spatial analysis of the distribution of 210Pb and 137Cs in Arctic and Antarctic sediments, this research will achieve three goals: first, measure the activity of short-lived radioisotopes in archived sediment cores, a service to the science community that is urgently needed before the isotopes decay beyond detection; second, produce a comprehensive pole-wide atlas of sediment accretion rates; and finally, conduct a temporal analysis of sedimentation rate changes over the last ~60 to 125 years along the Beaufort Sea coast of northern Alaska, an ecologically and economically important region experiencing environmental transformation due to climate warming.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

气候变化对极地地区的影响尤为严重，北极目前的变暖速度几乎是全球平均水平的四倍。极地变暖导致海岸侵蚀，增加向沿海海洋输送沉积物，影响从初级生产力到碳固存的生态系统过程。迫切需要跟踪沉降率的变化来确定当前状况并测量进一步的变化。然而，在极地地区，两种全球最可靠的沉积物示踪剂放射性同位素铅 210 (210Pb) 和铯 137 (137Cs) 却产生了不同的结果。为了了解这些放射性同位素在高纬度地区的分布和用途，本研究利用了俄勒冈州立大学海洋和地质知识库存档的大量极地沉积物岩心，并结合文献中综合的数据。结果提供了对北极和南极沉积物增生的首次系统研究。改进我们用来跟踪沉积变化的工具将有助于沿海管理者和决策者了解气候变化如何影响极地海岸线和海洋环境，以及当地社区未来应该期待什么。将对沉积物岩心进行二次采样并分析 210Pb 的活动分别使用 α 和 γ 光谱测定 137Cs（半衰期 = 22.3 年）和 137Cs（半衰期 = 30.1 年）。为了提供与沉积环境相关的背景信息，还将分析选定的子样本的沉积物堆积密度、粒度分布和有机物含量。对没有可测量的 210Pb 或 137Cs 活性的样品子集进行 14C 分析，以确定样品中缺乏放射性同位素是否是因为核心太旧、真正的表面层缺失，或者是因为寿命较短的放射性同位素不积累。通过对北极和南极沉积物中 210Pb 和 137Cs 的分布进行全面的空间分析，这项研究将实现三个目标：首先，测量存档沉积物岩心中短寿命放射性同位素的活度，这是科学界迫切需要的一项服务在同位素衰变到无法检测到之前；其次，制作一份全面的全极沉积物堆积速率图集；最后，对阿拉斯加北部波弗特海沿岸过去约 60 至 125 年的沉积率变化进行时间分析，该地区是一个生态和经济重要的地区，正在经历因气候变暖而发生的环境转变。该奖项反映了 NSF 的法定使命，并具有通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。