Targeted Basic Research to Enable Antarctic Science Applications of Cosmogenic-Nuclide Geochemistry

该项目将对地质定年技术进行基础研究，这些技术有助于确定极地地区，特别是南极洲冰川沉积物的年龄。这些技术对于确定极地冰盖在过去地质时期的大小是必要的，包括在过去的温暖气候时期，可能类似于现在和不久的将来的条件。因此，它们代表了估计极地冰盖对气候变暖的响应所需的重要技术能力。由于极地冰盖大小的变化是未来全球海平面变化的最大潜在因素，因此这种能力也与了解未来气候变化可能对海平面产生的影响有关。该项目的研究包括几种观察和实验方法，以提高这些技术的速度、效率、成本和准确性，以及一项科学推广计划，旨在使其他研究人员更广泛地利用所产生的能力。该项目支持一名博士后学者，并为极地和气候科学领域的人力资源开发做出贡献。该项目侧重于宇宙生成核素地球化学的几个领域，这是一种地球化学测年方法，依赖于地表岩石中宇宙射线产生的放射性核素的产生和衰变。对这些核素的测量可用于量化南极冰盖大小变化所覆盖和未覆盖的地点的地表暴露和冰盖的持续时间，从而提供一种重建过去冰盖变化的手段。第一组提出的实验旨在实施一种“虚拟矿物分离”方法来进行宇宙成因惰性气体分析，这种方法可以在不将矿物与宿主岩石物理分离的情况下测量某些矿物中的核素浓度。如果可行，这将大大提高这类分析的速度和成本。第二组实验将侧重于确定和量化一些有关核素的非宇宙起源背景清单的方法，目的是提高宇宙射线产生的这些核素清单的测量灵敏度和精度。第三个重点领域旨在提高测量同一样品中多种宇宙射线产生的核素的能力，这有可能提高基于这些核素的测年方法的准确性，并扩大这些方法可以应用的情况。如果成功，这些实验可能会改善与南极研究相关的宇宙生成-核素地球化学的许多应用，包括冰下基岩暴露测年、数百万年冰川沉积物测年以及有助于理解地貌演化和生态系统动力学的地表过程研究。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project will conduct basic research into geological dating techniques that are useful for determining the age of glacial deposits in polar regions, Antarctica in particular. These techniques are necessary for determining how large the polar ice sheets were in the geologic past, including during past periods of warm climate that likely resemble present and near-future conditions. Thus, they represent an important technical capability needed for estimating the response of polar ice sheets to climate warming. Because changes in the size of polar ice sheets are the largest potential contribution to future global sea-level change, this capability is also relevant to understanding likely sea-level impacts of future climate change. The research in this project comprises several observational and experimental approaches to improving the speed, efficiency, cost, and accuracy of these techniques, as well as a scientific outreach program aimed at making the resulting capabilities more broadly available to other researchers. The project supports a postdoctoral scholar and contributes to human resources development in polar and climate science.The project focuses on several areas of cosmogenic-nuclide geochemistry, which is a geochemical dating method that relies on the production and decay of cosmic-ray-produced radionuclides in surface rocks. Measurements of these nuclides can be used to quantify the duration of surface exposure and ice cover at locations in Antarctica that are covered and uncovered by changes in the size of the Antarctic ice sheets, thus providing a means of reconstructing past ice-sheet change. The first proposed set of experiments are aimed at implementing a 'virtual mineral separation' approach to cosmogenic noble gas analysis that may allow measurement of nuclide concentrations in certain minerals without physically separating the minerals from the host rock. If feasible, this would realize significant speed and cost improvements for this type of analysis. A second set of experiments will focus on means of identifying and quantifying non-cosmogenic background inventories of some relevant nuclides, which is intended to improve the measurement sensitivity and precision for cosmic-ray-produced inventories of these nuclides. A third focus area aims to improve capabilities to measure multiple cosmic-ray-produced nuclides in the same sample, which has the potential to improve the accuracy of dating methods based on these nuclides and to expand the situations in which these methods can be applied. If successful, these experiments are likely to improve a number of applications of cosmogenic-nuclide geochemistry relevant to Antarctic research, including subglacial bedrock exposure dating, dating of multimillion-year-old glacial deposits, and surface-process studies useful in understanding landform evolution and ecosystem dynamics.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.