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.

冰川间 - 冰川二氧化碳（CO2）循环的驱动力仍然是古气候学领域中最重要的未解决问题之一。 较低的大气二氧化碳水平对应于冰盖膨胀，而上升的二氧化碳水平是冰盖静修的主要驱动力。 尽管长期以来一直认为海洋 - 大气交换介导二氧化碳水平，但潜在的机制仍然难以捉摸。 在最后一次冰川最大值（LGM；约20，000年前），深大西洋比今天更加分层，这可能会增强深渊的碳储存。 如果早期的冰川间隔的特征是类似的模式，则表明分层是深海碳存储和因此冰川的基础。最近的研究还表明，在最后一次脱气过程中，深大西洋循环速度有所减慢，这可能导致碳在海洋和大气中的积累。 如果这种机制是冰盖撤退的主要驱动力，那么在过去14万年的每次脱位期间，都应存在较弱的深大西洋循环的证据。该项目的主要目标是使用来自西南大西洋的多个核心的数据来评估最后一个完整的冰川周期中海洋循环和碳储存的变化。研究将使用大约1500 m至4000 m的水深，研究将评估：1）大西洋的子午倾覆循环（AMOC）的强度，2）南大西洋的水柱分层； 3）它们与海洋碳储存的关系。 AMOC强度和水柱分层将通过分析底栖（底部住宅）有孔虫壳中的碳和氧同位素比来重建。将在过去140，000年的关键冰川和冰川间间隔内分析底栖有孔虫中的硼与钙比（B/CA）来评估碳储存。每个核心将使用氧同位素地层学日期，这是古气候学领域中众所周知的工具。拟议的工作可以通过创建跨越最后一个完整冰川周期的深层大西洋循环和碳存储的首次集成图片来改变我们对气候系统的理解。因此，结果将提供一个独特的框架，以了解长时间尺度上大气二氧化碳变异性的来源。结果也应通过提供内部一致的深度样本对核心的内部深度横切，可以使用超出当前项目范围的分析来研究。拟议工作的教育影响包括康涅狄格大学的研究生和两名本科生的参与。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子和更广泛影响的评估审查标准通过评估来获得支持的。