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.

如果要完全融化，格陵兰冰盖将贡献多达7米的海平面上升。因此，知道冰盖对过去的气候如何反应，既温暖又凉爽，这比现在更凉爽，可以帮助您了解将来的格陵兰冰盖如何和/或何时何时响应。虽然来自土地的地质记录为冰上的前进和撤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个撤退。另一方面，来自格陵兰岛周围的海洋沉积物提供了较少详细的记录，但可以通过许多冰川间冰期循环良好的记录，通过一系列气候条件在格陵兰冰盖上提供信息。该项目将使用与传统同位素方法更快，更便宜的磁性晶粒尺寸分离测量值来确定沉积物源位置，以推断冰层过程。该项目将在几个位置收集的沉积物核心的磁性特性并帮助评估格陵兰周围沉积物传输的变化，以期在最后150个kyrs中，提供了最后两个冰川的记录到冰川间过渡和随后的冰间裂缝，其中包括比现在更暖的冰川间的冰川。 目的是更好地了解格陵兰冰盖的稳定性和在其周围运输材料的洋流。 该项目支持早期职业博士后，研究生和夏季本科生。 将为俄勒冈州立大学海洋地质存储库开发公共展览和演讲。 该项目中使用的新磁性不混合技术将开发一种教育模块和短期材料。该项目探讨了南格陵兰冰盖（Sgis）沉积物来源的空间一致性。北大西洋深西部边界电流（DWBC）沉积物传输系统以及与DWBC冰川/冰川间变化相关的沉积物递送的根本变化如何影响又可能丰富对北大西洋的SGIS撤退和海洋循环的理解。 该项目将通过从格陵兰和挪威海，格陵兰岛和冰岛货架上的全新世时代沉积物以及来自南部格陵兰岛南部深海深海的更新世时代的沉积物来对粒度的核心顶部沉积物，全新世时代的沉积物进行特异性磁性测量来表征沉积物。从冰岛和格陵兰的地面样品上进行的工作表明，磁性特性随源和沉积物晶粒尺寸而变化，并且通过靶向淤泥分数，可以将材料与两个位置明确分开。在冰川终止期间，将使用来自格陵兰岛南部的海洋沉积物漂移的深层Eirik Ridge的淤泥馏分（海洋沉积物漂移）的磁性特性，可用于跟踪绿色的侵蚀产物，并允许推断SGIS消融增加的时期。这些磁性晶粒大小的特征与更难测量放射原同位素的更难一致，从而使更容易/更便宜的磁性测量可以通过更大的规模采样更加完全限制系统。表征沿格陵兰边缘和跨eirik山脊的磁性特性的空间变异性将告知并控制与DWBC变化相关的转运变化，而DWBC的变化为这些区域传递了沉积物。先前得出的最终成员数据将建立定量分离磁性组件和沉积过程所需的解释框架，以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