The Atlantic's role in ice age inception and termination: Assessing carbon storage and release with new Brazil Margin profiles from MIS 2 to MIS 6

大西洋在冰河时代开始和终止中的作用：利用新的巴西边际概况（从 MIS 2 到 MIS 6）评估碳储存和释放

• 批准号: 1804030
• 负责人: David Lund
• 金额: $ 37.9万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-06-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1804030&HistoricalAwards=false
• 关键词: Atlantic; role; ice; age; inception

The driver of glacial-interglacial carbon dioxide (CO2) cycles remains one of the most important unresolved questions in the field of paleoclimatology. Lower atmospheric CO2 levels correspond to ice sheet expansion, while rising CO2 levels are a primary driver of ice sheet retreat. Although it has long been assumed that ocean-atmosphere exchange mediates CO2 levels, the underlying mechanisms have remained elusive. During the Last Glacial Maximum (LGM; ~20,000 years ago), the deep Atlantic was more stratified than today, which likely enhanced carbon storage in the abyss. If earlier glacial intervals were characterized by a similar pattern, it would suggest that stratification is fundamental to deep ocean carbon storage and therefore glaciations. Recent studies also suggest the deep Atlantic circulation slowed during the last deglaciation, which may result in carbon accumulation in the surface ocean and atmosphere. If this mechanism is a key driver of ice sheet retreat, then evidence for a weaker deep Atlantic circulation should exist during each deglaciation of the last 140,000 years. The primary goal of this project is to use data from multiple cores in the Southwest Atlantic to assess changes in ocean circulation and carbon storage during the last full glacial cycle. Using sediment cores from approximately 1500 m to 4000 m water depth, the research will assess: 1) the strength of the Atlantic's meridional overturning circulation (AMOC), 2) water column stratification in the South Atlantic, and 3) their relation to oceanic carbon storage. AMOC strength and water column stratification will be reconstructed by analyzing carbon and oxygen isotopic ratios in the shells of benthic (bottom dwelling) foraminifera. Carbon storage will be assessed by analyzing the boron to calcium ratio (B/Ca) in benthic foraminifera during key glacial and interglacial intervals of the last 140,000 years. Each core will be dated using oxygen isotope stratigraphy, a well-known tool in the field of paleoclimatology.The proposed work could transform our understanding of the climate system by creating the first integrated picture of deep Atlantic circulation and carbon storage spanning the last full glacial cycle. The results will therefore provide a unique framework for understanding the source of atmospheric CO2 variability over long timescales. The results should also be useful to the broader paleoclimate community by providing an internally consistent depth transect of cores that can be studied using analyses beyond the scope of the current project. The educational impact of the proposed work includes the participation of a graduate student and two undergraduate students at the University of Connecticut.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

冰期-间冰期二氧化碳（CO2）循环的驱动因素仍然是古气候学领域最重要的未解决问题之一。 大气中二氧化碳浓度降低与冰盖扩张相对应，而二氧化碳浓度上升是冰盖退缩的主要驱动力。 尽管长期以来人们一直认为海洋-大气交换会调节二氧化碳水平，但其根本机制仍然难以捉摸。 在末次盛冰期（LGM；约 20,000 年前）期间，大西洋深海比今天更加分层，这可能增加了深渊中的碳储存。 如果早期的冰川期具有类似的特征，则表明分层是深海碳储存和冰川作用的基础。最近的研究还表明，在上次冰消期期间，大西洋深部环流减慢，这可能导致表层海洋和大气中的碳积累。 如果这一机制是冰盖消退的关键驱动因素，那么在过去 14 万年的每次冰消期间，都应该存在大西洋深部环流减弱的证据。该项目的主要目标是利用西南大西洋多个核心的数据来评估上一个完整冰川周期期间海洋环流和碳储存的变化。该研究将利用水深约 1500 m 至 4000 m 的沉积岩芯评估：1）大西洋经向翻转环流（AMOC）的强度，2）南大西洋的水柱分层，以及 3）它们与海洋碳储存的关系。通过分析底栖有孔虫贝壳中的碳和氧同位素比率，将重建 AMOC 强度和水柱分层。将通过分析过去 14 万年的关键冰期和间冰期期间底栖有孔虫的硼钙比 (B/Ca) 来评估碳储存。每个岩心都将使用氧同位素地层学进行年代测定，氧同位素地层学是古气候学领域的一种众所周知的工具。这项拟议的工作可以通过创建第一张跨越最后一个完整冰川周期的深大西洋环流和碳储存的综合图来改变我们对气候系统的理解。因此，这些结果将为了解长期大气二氧化碳变化的来源提供一个独特的框架。这些结果还应该对更广泛的古气候界有用，因为它提供了内部一致的核心深度断面，可以使用超出当前项目范围的分析进行研究。拟议工作的教育影响包括康涅狄格大学一名研究生和两名本科生的参与。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。