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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，对各自半球的热收支有直接和显著的影响。虽然已经作出了巨大的努力来重建与极端气候有关的大西洋的过去，但迄今为止还无法确定海洋环流的作用是过去10万年中发生的部分剧烈气候波动的原因还是结果。考虑这些问题的研究分支古海洋学在这里面临两个基本问题：一方面，所使用的方法往往存在弱点和适用性有限，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范围只允许得出有限的结论，这些结论可能提供局部信息，而这些信息不能外推到全球范围。为了得到可靠的关于海洋过去的热输送和碳和营养物分布的结果，需要收集大量的数据。从IODP/ODP核心存储库提供的材料代表了这项工作的独特基础。在较年轻的过去，测量钕同位素比率143Nd/144Nd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。在沉积物中的锰铁增生物中保存了钕特征及其过去突出水团的混合比例。从大块沉积物中仔细分离这些吸积物并随后测量它们的钕同位素的方法是一种大规模应用的极有前途的方法。它适用于任何有岩心的地方，它可以用现代标准质谱仪可靠地测量，如果具有相应的化学工作步骤的经验和知识，则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岩心来研究大西洋水团转变的时间问题。应当澄清这些转变发生得有多快，以及在哪个全球气候阶段哪个环流型态突出。借助箱形模式并与进一步的示踪剂（231Pa/230Th, d13C）进行比较，可以绘制出过去冰期-间冰期旋回的综合图像，从而推断气候系统中关键的反馈效应和相互作用，这对气候模式的改进和验证是直接必要的。