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.

最近地质二氧化碳的大气二氧化碳的增长最大，是在最后一次脱气期间（从20,000年前到10，000年前）。 随着北半球的冰盖融化，大气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得到充分解释。 最近的ICE核心结果表明，CO2上升可以追溯到同位素轻的碳源（即13c/12c比率较低的碳）。 一个可能的原因是降低了海洋光合作用，这将导致碳在地面海洋和大气中的积累。 较少的光合作用还将减少以有机物形式从地表海到中间深度落下的低13C/12C碳的量。 因此，降低的海洋生物生产力应在表面和中间深度产生相对的碳同位素信号，表面海洋变得更轻（较低的13c/12c），中间深度变得更重（较高的13c/12c）。 这项工作的结果可以通过限制碳同位素信号的来源，从而改变我们对气候系统的理解，从而改变最后一次退化期间大气二氧化碳变异性的驱动力。 拟议工作的更广泛的教育影响包括研究生和康涅狄格大学的本科生的参与。该项目的主要目标是使用来自多个位置的数据来评估上一次回发展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核心，包括西南大西洋，东南大西洋，南大西洋和西南太平洋以及东部热带太平洋。 每个核心从中间（〜1000 m）的深度中检索，这些深度应敏感到通过水柱掉落的有机物量。 该团队将通过分析底栖（海底住宅）和浮游生物（表面海洋住宅）生物体的化石中的碳同位素比来评估光合作用的变化。 该小组还将分析底栖化石中硼与钙的比率，以推断中等水深下碳浓度的总体变化。

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