Developing new magnetic tracers of ice sheet instability and ocean circulation in the northern North Atlantic

开发北大西洋北部冰盖不稳定和海洋环流的新型磁示踪剂

• 批准号: 1636381
• 负责人: Joseph Stoner
• 金额: $ 35.94万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-01 至 2020-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1636381&HistoricalAwards=false
• 关键词: Developing; new; magnetic; tracers; ice

The Greenland Ice Sheet would contribute up to 7 meters of sea-level rise if it were to melt completely. Thus, knowing how the ice sheet has responded to past climates, both warmer and cooler than present, provides a natural laboratory to help understand how and/or when the Greenland Ice Sheet may respond in the future. While the geological record from land provides great insights into ice-sheet advance and retreat, these records are generally restricted to the last retreat of the Greenland Ice Sheet. Marine sediments from around Greenland, on the other hand, provide a less detailed record, but one that can be well-dated through many glacial-interglacial cycles providing information on the Greenland Ice Sheet through a range of climate conditions. This project will use newly developed magnetic grain-size separation measurements that are faster and cheaper than traditional isotopic approaches to determine sediment source locations, in order to infer ice-sheet processes. The project will sample and measure the magnetic properties of sediment cores collected from several locations to control for and help assess changes in the sediment transport around Greenland for the last 150 kyrs providing a record of the last two glacial to interglacial transitions and the subsequent interglaciations, including one that is warmer than present. The objective is to obtain a better understanding of the stability of the Greenland Ice Sheet and the ocean currents that transport materials around it. The project supports an early career postdoc, a graduate student and a summer undergraduate student. Public exhibits and presentations will be developed for the Oregon State University Marine Geology Repository. An educational module and short course materials will be developed on the new magnetic unmixing techniques used in this project.This project explores the spatial consistency of the south Greenland Ice Sheet (sGIS) sediment source. The North Atlantic Deep Western Boundary Current (DWBC) sediment transport system and how fundamental change in sediment delivery associated with glacial/interglacial changes in the DWBC both influence and potentially enrich understanding of sGIS retreat and ocean circulation in the North Atlantic. The project will characterize sediment sources by making particle size specific magnetic measurements of core top sediments from the Greenland and Norwegian seas, Holocene age sediments from the Greenland and Iceland Shelf, and Pleistocene age sediments from the deep ocean off the southern Greenland margin. Work on terrestrial samples from Iceland and Greenland show that magnetic properties vary strongly with source and sediment grain size, and by targeting the silt fraction it will be possible to clearly separate materials from the two locations. Magnetic properties of the silt fraction from the deep Eirik Ridge, a marine sediment drift south of Greenland, will be used to track Greenlandic erosional products during glacial terminations and interglaciations allowing for periods of increased sGIS ablation to be inferred. These magnetic grain-size signatures are consistent with the much more difficult to measure radiogenic isotopes, allowing the easier/cheaper magnetic measurements to more completely constrain the system through larger scale sampling. Characterizing the spatial variability in magnetic properties along the Greenland margin and across the Eirik Ridge will inform on, and control for, changes in transport associated with changes in the DWBC that delivers sediment to these regions. End member data derived previously will establish the interpretive framework needed to quantitatively separate magnetic components, and sedimentary processes, with an aim toward addressing the fundamental question of how process drives magnetic variation.

如果格陵兰冰盖完全融化，海平面将上升7米。因此，了解冰盖如何对过去的气候做出反应，无论是比现在更温暖还是更冷，都提供了一个自然实验室，以帮助了解格陵兰冰盖未来如何和/或何时做出反应。虽然来自陆地的地质记录为冰盖的前进和后退提供了很好的见解，但这些记录通常仅限于格陵兰冰盖的最后一次退缩。另一方面，格陵兰周围的海洋沉积物提供了一个不太详细的记录，但可以通过许多冰川-间冰期循环提供格陵兰冰盖在一系列气候条件下的信息。该项目将使用新开发的磁性粒度分离测量方法，这种方法比传统的同位素方法更快、更便宜，以确定沉积物来源位置，从而推断冰盖过程。该项目将对从几个地点收集的沉积物岩心的磁性进行取样和测量，以控制和帮助评估过去15万年来格陵兰周围沉积物迁移的变化，提供最后两次冰期到间冰期的过渡和随后的间冰期的记录，包括一次比现在温暖的间冰期。 目的是更好地了解格陵兰冰盖的稳定性和在其周围运输物质的洋流。该项目支持一名早期职业博士后，一名研究生和一名暑期本科生。 将为俄勒冈州州立大学海洋地质储存库开发公共展览和演示。 将编制一个关于该项目所用新的磁性分离技术的教育单元和短期课程材料，该项目探讨南格陵兰冰盖沉积物来源的空间一致性。北大西洋西部深层边界流（DWBC）沉积物输运系统以及DWBC中与冰川/间冰期变化相关的沉积物输送的根本变化如何影响并可能丰富对北大西洋sGIS撤退和海洋环流的理解。 该项目将通过对格陵兰海和挪威海的岩心顶部沉积物、格陵兰和冰岛大陆架的全新世沉积物以及格陵兰南部边缘深海的更新世沉积物进行粒度特定的磁性测量，确定沉积物来源。对来自冰岛和格陵兰岛的陆地样品的研究表明，磁性随源和沉积物粒度的不同而变化很大，通过针对淤泥部分，将有可能清楚地将两个地点的物质分开。从深Eirik岭，格陵兰岛南部的海洋沉积物漂移的淤泥部分的磁性特性，将被用来跟踪格陵兰的侵蚀产品在冰川终止和间冰期允许增加的sGIS消融期推断。这些磁性粒度特征与更难测量的放射性同位素一致，允许更容易/更便宜的磁性测量通过更大规模的采样更完全地约束系统。表征磁特性的空间变异性沿着格陵兰边缘和整个Eirik海岭将告知，并控制，与DWBC的变化，提供沉积物到这些地区的运输变化。端元数据之前得出的将建立所需的解释框架，以定量分离磁性组件，沉积过程，目的是解决过程如何驱动磁性变化的基本问题。

项目成果

Grain size dependent magnetic discrimination of Iceland and South Greenland terrestrial sediments in the northern North Atlantic sediment record

北大西洋北部沉积物记录中冰岛和南格陵兰陆地沉积物的粒度依赖磁判别

• DOI: 10.1016/j.epsl.2017.06.042
• 发表时间: 2017
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Hatfield, Robert G.;Stoner, Joseph S.;Reilly, Brendan T.;Tepley, Frank J.;Wheeler, Benjamin H.;Housen, Bernard A.
• 通讯作者: Housen, Bernard A.

Particle Size Specific Magnetic Properties Across the Norwegian‐Greenland Seas: Insights Into the Influence of Sediment Source and Texture on Bulk Magnetic Records

• DOI: 10.1029/2018gc007894
• 发表时间: 2019-02
• 期刊: Geochemistry
• 影响因子: 3.7
• 作者: R. Hatfield;B. Wheeler;B. Reilly;J. Stoner;B. Housen