Studies Related to Establishing a Valid Radiocarbon Ventilation Rate for the Glacial Ocean

与建立冰川海洋有效放射性碳通气率相关的研究

• 批准号: 0435703
• 负责人: Wallace Broecker
• 金额: $ 95.24万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-09-01 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0435703&HistoricalAwards=false
• 关键词: Studies; Related; Establishing; Valid; Radiocarbon

ABSTRACTOCE-0435703Determining how ocean ventilation rates changed during the last glacial and deglacial periods is fundamental to reconstructing global changes in ocean circulation related to major shifts in the Earth's climate. In this project, researchers at the Lamont-Dougherty Earth Observatory of Columbia University will attempt to resolve some of the major problems that have confronted scientists studying these phenomena.The main objective of the project is to use radiocarbon ages from contemporaneous planktonic (surface dwelling) and benthic (bottom dwelling) foraminifera to define the age of deep waters over the period 21,000 - 14,000 14C years before the present time. To this end it will be necessary to make multiple radiocarbon dates on samples from various depths and locations. Recent work has suggested that some core locations may be unsuitable for precise radiocarbon dating due to the presence of secondary carbonate phases forming within the sediment column. A second theme of this project is to investigate the presence of these phases and if possible, determine which sites are ultimately more or less valid for determining ocean ventilation rates. This goal will be addressed by carrying out dissolution experiments on samples that are known to yield anomalous 14C ages, the aim being to isolate and date individually the different phases. Changes in carbon storage and ocean circulation will be investigated by reconstructing changes in deep sea carbonate ion concentrations using the foraminiferal shell weight proxy developed by Lohmann (1995). A further aim of the project will be to use land-based evidence to investigate the relative timing of events occurring at the close of the last glacial period and during deglaciation. This work will be based on precise dating of glacial features and exposure dating of moraines left by retreating glaciers at the end of glacial times.Broader impacts: This study should provide answers to some fundamental questions concerning changes in global climate -- how different was ocean circulation during glacial time and how, if at all, have changes in ocean circulation affected climate in the past. The results from these studies will provide important constraints for paleo- and future climate models.

确定海洋通风率在末次冰期和冰消期是如何变化的，对于重建与地球气候主要变化相关的海洋环流的全球变化至关重要。 在这一项目中，哥伦比亚大学拉蒙特-道金斯地球观测站的研究人员将试图解决研究这些现象的科学家们所面临的一些主要问题。该项目的主要目标是利用同时代南极洲的放射性碳年龄（地表居住）和底栖（底部居住）有孔虫，以确定在现在之前的21，000 - 14，000 14 C年期间的深水沃茨的年龄。 为此，有必要对不同深度和地点的样品进行多次放射性碳测年。 最近的工作表明，由于沉积物柱内形成的次生碳酸盐相的存在，一些岩心位置可能不适合进行精确的放射性碳测年。 该项目的第二个主题是调查这些阶段的存在，如果可能的话，确定哪些地点最终或多或少地适用于确定海洋通风率。 这一目标将通过对已知产生异常14 C年龄的样品进行溶解实验来实现，目的是分离和单独测定不同阶段的年龄。 将利用Lohmann（1995年）开发的有孔虫外壳重量代用指标，通过重建深海碳酸盐离子浓度的变化，研究碳储存和海洋环流的变化。 该项目的另一个目的是利用陆基证据调查末次冰期结束时和冰川消退期间发生的事件的相对时间。 这项工作的基础是精确测定冰川特征的年代和冰川期结束时冰川退缩留下的冰碛暴露年代。更广泛的影响：这项研究应能回答有关全球气候变化的一些基本问题-冰川期海洋环流有多大的不同，以及海洋环流的变化对过去气候有何影响（如果有的话）。 这些研究的结果将为古气候模型和未来气候模型提供重要的约束。