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Reconstruction of the Timing of Water Mass Exchange during Progressive Closure of the Central American Seaway in the Pliocene

上新世中美洲航道逐渐关闭期间水体交换时间的重建

基本信息

批准号：
180161436
负责人：
Professor Dr. Martin Frank
金额：
--
依托单位：
Alfred-Wegener-Institut (AWI) Helmholtz-Zentrum für Polar- und Meeresforschung
依托单位国家：
德国
项目类别：
Infrastructure Priority Programmes
财政年份：
2010
资助国家：
德国
起止时间：
2009-12-31 至 2015-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/180161436?language=en
关键词：
Reconstruction Timing Water Mass Exchange

项目摘要

The goal of this project is to reconstruct the history of shallow, intermediate and deep water connections between the Caribbean Sea and the eastern Equatorial Pacific Ocean during the shoaling of the Central American Seaway (CAS) at the present location of Panama between 5.0 and 2.0 million years ago (Ma) using radiogenic isotopes. The progressive closure of the CAS and the associated reorganisation of ocean circulation have been controversially reported as contributing to a warming and a cooling of global climate, as well as increasing moisture supply to the northern hemisphere and hence preconditioning of the inception of Northern Hemisphere Glaciation. We propose to use the radiogenic isotopes of neodymium (Nd) and lead (Pb) as proxies to trace water masses and their mixing on either side of Panama. This study will use samples from ODP cores 999 and 1000 in the Caribbean and 1241 in the eastern tropical Pacific. In each core we will measure the Nd isotope composition of planktonic foraminiferal calcite in order to characterise surface water exchange and mixing, and the Nd and Pb isotope composition of early diagenetic ferromanganese coatings of the same sediment samples to characterise intermediate and deep water exchange and to assess differences and potential phase lags between surface and deeper water signatures. Sampling resolution will initially be at 100 thousand years (kyr), increasing to less than 21 kyr (i.e. sub-Milankovitch) for key periods identified in the 100 kyr resolution study. The aim of this project is to reconstruct the exact timing of CAS closure to deep, intermediate and shallow waters. These results will be compared with the evolution of the strength of North Atlantic Deep Water (NADW) formation and with the timing of changes in the distribution of heat and moisture to high northern latitudes. It will thus allow to better constrain causes and consequences during this key period of global climate evolution.

该项目的目标是利用放射性同位素重建500万至200万年前中美洲航道在巴拿马现址变浅期间加勒比海和东赤道太平洋之间浅水、中层和深水连接的历史。CAS的逐渐关闭和相关的海洋环流重组被有争议地报道为全球气候变暖和变冷的贡献，以及增加北方半球的水分供应，因此预处理北方半球冰川的开始。我们建议使用放射性同位素钕（Nd）和铅（Pb）作为代理跟踪水团和它们的混合在巴拿马的两侧。这项研究将使用加勒比地区ODP岩芯999和1000以及热带太平洋东部ODP岩芯1241的样本。在每个岩心中，我们将测量浮游有孔虫方解石的Nd同位素组成，以确定地表水交换和混合，并测量相同沉积物样品的早期成岩铁锰涂层的Nd和Pb同位素组成，以确定中层和深层水交换，并评估地表水和深层水特征之间的差异和潜在的相位滞后。采样分辨率最初将为10万年（kyr），在10万年分辨率研究中确定的关键时期增加到小于21 kyr（即亚米兰科维奇）。该项目的目的是重建CAS关闭深水、中层和浅水沃茨的确切时间。这些结果将与北大西洋深水形成强度的演变以及北方高纬度地区热量和水分分布变化的时间进行比较。因此，它将有助于在全球气候演变的这一关键时期更好地限制原因和后果。