Investigation of Past Variations In Surface Ocean Radiocarbon During The Holocene

这项持续研究的主要目标是利用化石和活珊瑚的年度珊瑚带，在过去的表层海水状态中构建高精度的14C时间历史。这些数据，当与稳定的氧和碳同位素测量（18o和13C）相结合时，揭示了关于上层海洋中14CO2循环以及空气和海洋之间14CO2交换的重要信息。将进行四项实验：1)利用化石珊瑚序列确定古代海洋中14C的十年时间尺度变化是否存在，这些化石珊瑚序列已经通过热电离质谱法用230 Th确定了年代。研究人员将对瓦努阿图和佛罗里达州比斯坎国家公园的珊瑚进行两个时间段的研究。这将允许在全新世存在的极端热条件下比较两种主要洋流（分别是南赤道流和墨西哥湾流）中的14C：2)确定小冰期晚期（公元1680-1730年）北太平洋14C的十年时间尺度变化的存在与否，并将此记录与西南太平洋的14C大变化与古厄尔尼诺事件相关的记录进行比较。北大西洋的珊瑚也将被研究，以检查全球范围内14C变化的程度。3)将在北太平洋的三个地点测量苏斯效应（主要是由于19世纪末以来不含14C的化石燃料二氧化碳导致的14C的降低），在这些地点没有发现可测量的苏斯效应。4)建议对费尔南多·迪诺诺尼亚的一种珊瑚进行收集和高精度的14C分析。赤道大西洋是目前温带和热带海洋中唯一没有原子弹爆炸后14C记录的地方。它对于参数化示踪剂进入大西洋的重要性再怎么强调也不为过。将使用加速器质谱（AMS）技术进行有限数量的高精度14C分析，对每个样品进行多个石墨靶分析。其余的样品（75%）将在UCI放射性碳实验室使用传统的气体计数技术进行高精度测量。

9314691 DRUFFEL The major goal of this continuing research is to construct time histories of high-precision 14C in past surface ocean water regimes using annual coral bands from fossil and living corals. These data, when coupled with stable oxygen and carbon isotope measurements (18 O and 13C), reveal important information regarding the cycling of 14CO2 in the upper ocean and the exchange of 14CO2 between air and sea. Four experiments will be conducted 1) To determine whether decade time-scale variations in 14C were present in ancient oceans using fossil coral sequences that have been absolutely dated using 230 Th by thermal ionization mass spectrometry. Two time periods will be studied in corals from Vanuatu and from Biscayne National Park, Florida. This will allow for the comparison of 14C in two major ocean currents (the South Equatorial Current and the Gulf Stream, respectively), during extreme thermal conditions that existed in the Holocene: the Little Ice Age and the Hypsithermal. 2) To determine the presence or absence of decade time-scale variations in 14C in the North Pacific during the late Little Ice Age (AD 1680-1730), and compare this record to that obtained from the southwestern Pacific where large 14C variations correlated with ancient El Nino events. Corals from the North Atlantic will also be studied, to examine the extent to which the 14C variability was world-wide. 3) The Suess effect (lowering of 14C due mainly to 14C-free fossil fuel CO2 since late 1800s) will be measured at three sites in the northern Pacific, where no measurable Suess effect was found 4)Collection and high-precision 14C analyses are proposed for a coral from Fernando de Noronha. The equatorial Atlantic is presently the only location in the temperate and tropical oceans for which a post-bomb 14C record is not available. Its importance for parameterizing tracer penetration into the Atlantic cannot be overstated. A limited number of high-precision 14C analyses will b e made using Accelerator Mass Spectrometry (AMS) techniques, with multiple graphite target analysis for each sample. The remainder of the samples (75%) will be measured to high- precision at the UCI Radiocarbon Laboratory using conventional, gas-counting techniques.