Millennial-scale atmospheric CO2 variability during the last deglaciation: Testing the biological pump hypothesis using upper ocean carbon isotope records

末次冰消期间的千年尺度大气二氧化碳变化：利用上层海洋碳同位素记录检验生物泵假说

• 批准号: 1702231
• 负责人: David Lund
• 金额: $ 26.3万
• 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: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1702231&HistoricalAwards=false
• 关键词: Millennial; scale; atmospheric; CO2; variability

The largest increase in atmospheric CO2 in the recent geologic past occurred during the last deglaciation (from 20,000 to 10,000 years ago). As ice sheets in the Northern Hemisphere melted, atmospheric CO2 levels rose by ~30%. Despite extensive research, the underlying cause of the CO2 change has yet to be fully explained. Recent ice core results show that the CO2 rise can be traced to an isotopically light carbon source (i.e. carbon with a low 13C/12C ratio). One possible cause is reduced marine photosynthesis, which would result in the accumulation of light carbon in the surface ocean and atmosphere. Less photosynthesis would also reduce the amount of low 13C/12C carbon that falls from the surface ocean to intermediate depths in the form of organic matter. Thus, reduced marine biological productivity should yield opposing carbon isotopic signals at surface and intermediate depths, with the surface ocean becoming isotopically lighter (lower 13C/12C) and intermediate depths becoming heavier (higher 13C/12C). The results of this work could transform our understanding of the climate system by constraining the source of carbon isotopic signals and therefore the driver of atmospheric CO2 variability during the last deglaciation. The broader educational impact of the proposed work includes the participation of a graduate student and an undergraduate at the University of Connecticut.The primary goal of this project is to use data from multiple locations to assess changes in marine photosynthesis during the last deglaciation. The research team will use high resolution sediment cores from five different locations, including the Southwest Atlantic, the Southeast Atlantic, the Southern Ocean, and Southwest Pacific, and the eastern tropical Pacific. Each core was retrieved from intermediate (~1000 m) depths that should be sensitive to the amount of organic matter falling through the water column. The team will assess variations in photosynthesis by analyzing the carbon isotopic ratio in the fossils of benthic (sea floor dwelling) and planktonic (surface ocean dwelling) organisms. The team will also analyze the ratio of boron to calcium in the benthic fossils to infer overall changes in carbon concentration at intermediate water depths.

在最近的地质历史中，大气二氧化碳的最大增幅发生在最后一次冰川消融期间(从20000年前到10000年前)。随着北半球冰盖的融化，大气中的二氧化碳水平上升了约30%。尽管进行了广泛的研究，但二氧化碳变化的根本原因尚未完全解释。最近的冰芯结果表明，二氧化碳的上升可以追溯到一个同位素较轻的碳源(即低13C/12C比的碳)。一个可能的原因是海洋光合作用减弱，这将导致表层海洋和大气中光碳的积累。较少的光合作用还会减少从表层海洋落到中等深度的有机物质形式的低13C/12C碳的数量。因此，海洋生物生产力下降将在表层和中等深度产生相反的碳同位素信号，表层海洋的同位素变轻(较低的13C/12C)，而中等深度变得较重(较高的13C/12C)。这项工作的结果可能会改变我们对气候系统的理解，因为它限制了碳同位素信号的来源，从而限制了最后一次冰川消融期间大气二氧化碳变异性的驱动因素。这项拟议工作的更广泛的教育影响包括康涅狄格大学的一名研究生和一名本科生的参与。该项目的主要目标是使用来自多个地点的数据来评估最后一次冰川消融期间海洋光合作用的变化。研究小组将使用来自五个不同地点的高分辨率沉积物岩心，包括西南大西洋、东南大西洋、南大洋和西南太平洋以及热带东太平洋。每个岩心都是从中等深度(~1000米)提取的，该深度应该对穿过水柱的有机物数量敏感。该团队将通过分析海底生物(海底生物)和浮游生物(表层海洋生物)化石中的碳同位素比率来评估光合作用的变化。该团队还将分析海底化石中的硼与钙的比例，以推断中等水深碳浓度的总体变化。

项目成果

Less Remineralized Carbon in the Intermediate‐Depth South Atlantic During Heinrich Stadial 1

• DOI: 10.1029/2018pa003537
• 发表时间: 2019-07
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: M. Lacerra;D. Lund;G. Gebbie;D. Oppo;Jimin Yu;A. Schmittner;N. Umling

Carbon isotope minima in the South Atlantic during the last deglaciation: evaluating the influence of air-sea gas exchange

• DOI: 10.1088/1748-9326/ab126f
• 发表时间: 2019-05
• 期刊: Environmental Research Letters
• 影响因子: 6.7
• 作者: D. Lund;J. Hertzberg;M. Lacerra