Oceanic circulation modes of the Glacial-Interglacial cycle - high resolution measurements of Neodymium isotopes on Atlantic IODP/ODP sediment cores.

冰期-间冰期循环的海洋环流模式 - 大西洋 IODP/ODP 沉积物核心上的钕同位素的高分辨率测量。

基本信息

批准号：
242773409
负责人：
Professor Dr. Norbert Frank
金额：
--
依托单位：
Institut für Umweltphysik
依托单位国家：
德国
项目类别：
Infrastructure Priority Programmes
财政年份：
2013
资助国家：
德国
起止时间：
2012-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/242773409?language=en
关键词：
Oceanic circulation modes Glacial Interglacial

项目摘要

It is supposed that in the global interplay of hemispheres either the deep water production in the North or in the South Atlantic dominated, having direct and significant influence on the heat budget of the respective hemisphere. Although great efforts have been undertaken in order to reconstruct the past of the extremely climate relevant Atlantic Ocean, it has so far not been possible to identify the role of the ocean circulation as cause or consequence of the in part dramatic climate fluctuations which have taken place in the past 100,000 years. The branch of research considering these questions, the palaeoceanography, faces two essential problems here: On the one hand , the methods used often have weaknesses and limited applicability, especially tracers which take part in the nutrient cycle and are subject to diagenetic processes. On the other hand the temporal and spacial coverage of existing measurements allows only for limited conclusions which may deliver local information which cannot be extrapolated to a global scale. In order to come to reliable results about the oceanic past of heat transport and the distribution of carbon and nutrients it is necessary to collect a high amount of data. The material provided from the IODP/ODP core repositories represents a unique fundament for this work. In the younger past the measurement of the neodymium isotope ratio 143Nd/144Nd emerged as method of choice. The distinct isotopic signatures of water masses originating in the Pacific and the North Atlantic Deep Water render neodymium a unique tracer for the ocean circulation in the Atlantic. The neodymium signature and with it the mixing ratio of the prominent water masses in the past is preserved in ferromanganese accretions in the sediment. The appraoch of careful separation of these accrections from the bulk sediment and the subsequent measurement of their neodymium isotopy serves as a methodology which is, applied on a large scale, uttermost promising. It is applicable wherever there are cores available, it is reliably measurable with modern standard mass spectrometers and the chemical treatment of the sample material is relatively fast and cost-efficient, if the respective experience and the knowledge of the chemical work steps exist. Therefore, using selected IODP/ODP cores the question of the timings of water mass transitions in the Atlantic shall be pursued. It shall be clarified how fast these transitions took place and in which global climatological phase which circulation pattern was prominent. With the aid of box models and the comparison with further tracers (231Pa/230Th, d13C) a comprehensive image of the past glacial-interglacial cycle shall be drawn, allowing inference of the crucial feedback effects and interactions in the climate system, which are directly necessary for the improvement and validation of climate models.

据推测，在全球半球的相互作用中，北大西洋或南大西洋的深水生产占主导地位，对各自半球的热量收支有直接而重大的影响。尽管人们付出了巨大的努力来重建与气候极其相关的大西洋的过去，但迄今为止还不可能确定海洋环流对于已经发生的部分剧烈气候波动的原因或结果。在过去的十万年里。考虑这些问题的研究分支，即古海洋学，在这里面临两个基本问题：一方面，所使用的方法通常存在弱点且适用性有限，特别是参与营养循环并受成岩过程影响的示踪剂。另一方面，现有测量的时间和空间覆盖范围仅允许有限的结论，这些结论可能提供无法外推到全球范围的局部信息。为了获得有关海洋过去的热传输以及碳和营养物分布的可靠结果，有必要收集大量数据。 IODP/ODP 核心存储库提供的材料代表了这项工作的独特基础。在较早的时期，测量钕同位素比 143Nd/144Nd 已成为首选方法。源自太平洋和北大西洋深水的水团的独特同位素特征使钕成为大西洋海洋环流的独特示踪剂。沉积物中的铁锰沉积物中保留了过去主要水团的钕特征及其混合比例。从大量沉积物中仔细分离这些堆积物并随后测量其钕同位素的方法是一种大规模应用的最有前途的方法。它适用于任何有可用核心的地方，它可以用现代标准质谱仪可靠地测量，并且如果存在相应的经验和化学工作步骤的知识，样品材料的化学处理相对快速且具有成本效益。因此，应使用选定的 IODP/ODP 核心来研究大西洋水团转变的时间问题。应澄清这些转变发生的速度有多快，以及在哪个全球气候阶段哪种环流模式最为突出。借助箱模型并与进一步的示踪剂（231Pa/230Th，d13C）进行比较，应绘制过去冰期-间冰期循环的全面图像，从而推断出气候系统中的关键反馈效应和相互作用，这些效应和相互作用可以直接改进和验证气候模型所必需的。