Intermediate water circulation changes in the western equatorial Atlantic over the past 20,000 years

近2万年赤道西大西洋中层水环流变化

• 批准号: 262668409
• 负责人: Dr. Ines Voigt
• 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: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/262668409?language=en
• 关键词: Intermediate; water; circulation; changes; western

The circulation of Antarctic Intermediate Water (AAIW) is thought to make an important contribution to the global ocean-climate system. In the modern ocean, AAIW supplies a large fraction of the northward flow required to balance the southward export of North Atlantic Deep Water (NADW), and thus represents a key player in the Atlantic meridional overturning circulation (AMOC). Despite of its critical role, a detailed understanding of AAIW over the past 20,000 years and how it participates in the AMOC remains a significant challenge in climate research due to the lack of high temporal resolution climate archives. Abrupt changes in northward penetration of AAIW associated with reductions of the AMOC have been hypothesized for abrupt cold events over the last 20,000 years. Controversy persists as to whether the northward flow of AAIW is waxing or waning during these cold events. Thus, it is clear that a better understanding of the AAIW variability and how it participates in the AMOC is required. High temporal resolution climate archives from the western equatorial Atlantic (referred to hereafter as WEA) can shed some light on the potential role the AAIW plays in contributing to AMOC changes. Two key questions arise from the chain of climate events of the past 20,000 years: (1) To what extent was the AMOC affected by past perturbation in the AAIW overturning circulation, thereby favoring a waxing or waning of AAIW during abrupt cold periods? (2) Which role Southern Hemisphere climate variability plays in driving past perturbation in the AAIW overturning circulation? To address these questions, we propose to reconstruct changes in AAIW/NADW by applying complementary proxies on a transect of 6 selected sediment cores in the WEA that covers the full range of the interface between southern- and northern water masses. The WEA forms a key location in the global ocean conveyor belt, and it thus critical in understanding global ocean-climate changes. First, we will analyze the stable isotopic composition of benthic foraminifera to reconstruct past changes in the intermediate water mass geometry. Second, we will measure the neodymium isotope ratios from the mid-depth WEA transect. This method can also be used as a powerful tool to constrain past changes in water-mass mixing, driven by reorganizations of the AMOC. Third, we will measure the concentrations of redox-sensitive metal which are controlled by the amount of dissolved oxygen at the sea floor. This method can be used to assess information about the underlying formation processes at the AAIW source. The appropriate evaluation of the possible changes in AMOC in the WEA as proposed herein became a major issue, since a weakening in AMOC is predicted for the coming decades. Accordingly, a comprehensive understanding of the different possible behaviors of the WEA is a key element in predicting future climate.

南极中间水的环流被认为对全球海洋气候系统做出了重要贡献。在现代海洋中，AAIW提供了平衡北大西洋深水(NADW)向南输出所需的北向流的很大一部分，因此在大西洋经向翻转环流(AMOC)中扮演着关键角色。尽管AAIW发挥了关键作用，但由于缺乏高时间分辨率的气候档案，详细了解AAIW过去20,000年来的情况以及它是如何参与AMOC的，在气候研究中仍然是一个重大挑战。AAIW向北穿透的突然变化与AMOC的减少有关，在过去的20,000年里，人们假设发生了突然的寒冷事件。对于AAIW向北的流动在这些寒冷事件期间是增强还是减弱，争议仍在继续。因此，显然需要更好地了解AAIW的可变性及其如何参与AMOC。来自赤道西部大西洋(以下简称WEA)的高时间分辨率气候记录可以揭示AAIW在促进AMOC变化方面所起的潜在作用。过去20,000年的气候事件链产生了两个关键问题：(1)过去AAIW翻转环流中的扰动在多大程度上影响了AMOC，从而有利于AAIW在突然寒冷时期的增减？(2)南半球气候变率在驱动AAIW翻转环流中的过去扰动中起到了什么作用？为了解决这些问题，我们建议通过在WEA中选定的6个沉积物岩芯的横断面上应用补充代理来重建AAIW/NADW的变化，该横断面覆盖了南北水团之间的整个界面范围。WEA形成了全球海洋传送带中的关键位置，因此它对于理解全球海洋气候变化至关重要。首先，我们将分析底栖有孔虫的稳定同位素组成，以重建中间水团几何结构的过去变化。其次，我们将测量WEA中层样带的Nd3+同位素比值。这种方法也可以作为一种强有力的工具来约束过去由AMOC重组所驱动的水-质量混合的变化。第三，我们将测量受海底溶解氧量控制的氧化还原敏感金属的浓度。这种方法可以用来评估AAIW来源的潜在形成过程的信息。由于在未来几十年内AMOC的减弱被预测，因此对WEA中AMOC可能发生的变化的适当评估成为一个主要问题。因此，全面了解WEA的不同可能行为是预测未来气候的关键因素。

项目成果

Intermittent development of forest corridors in northeastern Brazil during the last deglaciation: Climatic and ecologic evidence

• DOI: 10.1016/j.quascirev.2018.05.026
• 发表时间: 2018-07
• 期刊: Quaternary Science Reviews
• 影响因子: 4
• 作者: I. Bouimetarhan;C. Chiessi;C. González‐Arango;L. Dupont;I. Voigt;M. Prange;K. Zonneveld

Deglacial changes in the strength of deep southern component water and sediment supply at the Argentine continental margin

阿根廷大陆边缘南部深层水和沉积物供应强度的冰消变化

• DOI: 10.1002/2016pa003079
• 发表时间: 2017
• 期刊: Paleoceanography
• 作者: Warratz;Henrich;Chiessi;Lantzsch
• 通讯作者: Lantzsch

Holocene changes in Antarctic Intermediate Water flow strength in the Southwest Atlantic

西南大西洋南极中层水流强度的全新世变化

• DOI: 10.1016/j.palaeo.2016.09.018
• 发表时间: 2016
• 期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
• 作者: Chiessi;Henrich
• 通讯作者: Henrich

Variability in mid‐depth ventilation of the western Atlantic Ocean during the last deglaciation

• DOI: 10.1002/2017pa003095
• 发表时间: 2017-09
• 期刊: Paleoceanography
• 作者: I. Voigt;A. P. Cruz;S. Mulitza;C. Chiessi;A. Mackensen;J. Lippold;Benny Antz;M. Zabel;Yancheng Zhang;C. Barbosa;A. Tisserand

Holocene shifts of the southern westerlies across the South Atlantic

• DOI: 10.1002/2014pa002677
• 发表时间: 2015-02
• 期刊: Paleoceanography
• 作者: I. Voigt;C. Chiessi;M. Prange;S. Mulitza;J. Groeneveld;V. Varma;Ruediger Henrich