Advection and mixing of deep water masses in the tropical and western North Atlantic Ocean from thorium and protactinium isotopes

钍和镤同位素对热带和北大西洋西部深水团的平流和混合

• 批准号: 199971746
• 负责人: Dr. Sven Kretschmer
• 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: 2011
• 资助国家: 德国
• 起止时间: 2010-12-31 至 2013-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/199971746?language=en
• 关键词: Advection; mixing; deep; water; masses

Natural radionuclides are powerful tracers to identify and quantify transport processes of particles and of water masses in the ocean. The distribution of the isotope pair 231Pa/230Th in Atlantic sediments has been widely used to trace past deep water ventilation. The formation area of deep water in the NW Atlantic has been considered the best example where the sediment record of this tracer can help unravel the history of Atlantic Meridional Overturning Circulation (AMOC). It came as a surprise that recent findings showed a discrepancy between present day ventilation and the 231Pa/230Th signature in surface sediments, which may be due to an unexpectedly large influence of particle composition on the differential removal of the two isotopes to the sediments. The NW Atlantic thus is now a test case for the applicability of 231Pa/230Th as paleocirculation tracer. Here I propose to study the scavenging behaviour of Th and Pa during the early stages of the formation of North Atlantic Deep Water and during its distribution in the tropical Atlantic by analyzing a comprehensive set of dissolved and particulate samples collected in 2010 along the sections of two cruises executed with RV Meteor (M81/1) (GEOTRACES Cruise A11, Canaries – Port of Spain, Trinidad and Tobago in February/March 2010) and during RV Pelagia expedition 64PE319/321 (GEOTRACES Cruise A02, Scrabster, Scotland – Fortaleza, Brasil, April - July 2010) in the tropical and western North Atlantic. These cruises were official GEOTRACES expeditions uniquely focused on the use of ultra trace metal clean sampling facilities. The high-resolution distribution of a large suite of other trace elements and their isotopes (TEIs) will provide the best achievable background to understand the possible influences controlling the scavenging process of trace metals and to investigate possible correction procedures to improve the 231Pa/230Th AMOC ventilation proxy.

天然放射性核素是强有力的示踪剂，可用于确定和量化海洋中粒子和水团的迁移过程。同位素对231 Pa/230 Th在大西洋沉积物中的分布已被广泛用于追踪过去的深水通风。西北大西洋深水区的形成被认为是最好的例子，这种示踪剂的沉积物记录可以帮助解开大西洋经向翻转环流（AMOC）的历史。令人惊讶的是，最近的研究结果表明，现今的通风和231 Pa/230 Th签名之间的差异，在表层沉积物，这可能是由于颗粒组成的差异去除的两种同位素的沉积物的影响出乎意料的大。因此，西北大西洋现在是231 Pa/230 Th作为古环流示踪剂的适用性的测试案例。在这里，我建议通过分析2010年沿着用RV Meteor（M81/1）执行的两次巡航的剖面上收集的一组全面的溶解和颗粒样品，研究北大西洋深水形成的早期阶段及其在热带大西洋的分布过程中Th和Pa的清除行为。（2010年2月/3月，GEOTRACES A11号游轮，加那利群岛-西班牙港，特立尼达和托巴哥）和64 PE 319/321号Pelagia号RV探险期间（GEOTRACES Cruise A02，斯克拉布斯特，苏格兰-福塔莱萨，巴西，2010年4月-7月）在热带和北大西洋西部。这些巡航是GEOTRACES的官方考察，专门关注超痕量金属清洁采样设施的使用。其他微量元素及其同位素（TEI）的大套件的高分辨率分布将提供最好的可实现的背景，以了解可能的影响控制清除过程中的微量金属，并调查可能的校正程序，以提高231 Pa/230 Th AMOC通风代理。