Carbon 14 Calibration, Production and Reservoir Changes Over the Past 50,000 Years

该奖项将测量成对的铀和钍同位素，以及对300个珊瑚标本的放射性碳测量，这些样品的年代介于12,000到50,000年前。这些数据将把基于树轮碳同位素的时间序列扩展到使用原始珊瑚样本进行放射性碳测定的技术极限。将这些结果与其他人产生的记录结合在一起，研究人员预计将为精确和准确的国际放射性碳校准计划做出贡献，该计划将广泛影响那些将放射性碳数据作为时间衡量标准的科学领域。这项研究的主要理由是，珊瑚分析的初步结果表明，上一次冰川时期的放射性碳时间尺度与以铀和钍方法为基础的时间尺度有5000多年的偏差。地球磁场的变化，太阳的对流，以及来自外层空间的超新星事件，都会影响大气中放射性碳的宇宙射线产生。大气、海洋和生物圈之间的碳交换速率及其衰变，调节着大气中碳同位素的浓度。过去11,500年的这段历史被记录在各种自然档案中，如每年一次的带状树轮、各种沉积、洞穴和珊瑚。放射性碳测年为考古学、人类学、气候学、古海洋学、示踪海洋学、孢粉学、湖泊研究和古物年代测定等许多科学领域提供了一个关键的辐射计时器。与其他地球物理数据结合时，可以将放射性碳时间序列解释为对地球磁场、太阳可变性、磁漂移和与气候有关的变化的监测或测量。

This award will measure paired uranium and thorium isotopes and radiocarbon measurements on 300 coral specimens dated from between 12,000 and 50,000 years before present. These data will extend the tree ring carbon isotope-based time series to the technical limits of radiocarbon determinations using pristine coral samples. Combining such results with records generated by others, the researchers expect to contribute to a precise and accurate International Radiocarbon Calibration program that will broadly impact those fields of science that utilize radiocarbon data as a measure of time. The primary justification of the research is that initial results from the analyses of corals demonstrate that the radiocarbon time scale is more than 5,000 years offset from time scales based on uranium and thorium methods, for the last glacial period. Changes in the Earth's magnetic field, the Sun's convection, and supernova events from outer space all affect the cosmic ray production of radiocarbon in the atmosphere. The carbon exchange rate between the atmosphere, oceans, and biosphere, and its decay, regulate the concentration of carbon isotopes in the atmosphere. This history over the past 11,500 years is recorded in a variety of natural archives such as annually banded tree rings, varved-sediments, speleothems, and corals. Radiocarbon ages provide a critical radiometric chronometer for many fields of science such as archeology, anthropology, climate, paleoceanograhy, tracer oceanography, palynology, lake studies, and antiquities dating. When combined with other geophysical data, it is possible to interpret the radiocarbon time series as a monitor or measure of the Earth's magnetic field, solar variability, magnetic excursions, and climate related changes.