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.

最近地质时期大气中二氧化碳的最大增加发生在最后一次冰消期（20,000 至 10,000 年前）。 随着北半球冰盖融化，大气中二氧化碳含量上升了约 30%。 尽管进行了大量研究，但二氧化碳变化的根本原因尚未得到充分解释。 最近的冰芯结果表明，二氧化碳的增加可以追溯到同位素轻碳源（即 13C/12C 比率低的碳）。 一个可能的原因是海洋光合作用减少，这将导致轻碳在海洋表面和大气中积累。 光合作用减少也会减少以有机物形式从海洋表层落到中间深度的低 13C/12C 碳的数量。 因此，海洋生物生产力的降低应在表面和中间深度产生相反的碳同位素信号，表层海洋同位素变得更轻（13C/12C更低），而中间深度变得更重（13​​C/12C更高）。 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，从而改变上次冰消期期间大气二氧化碳变化的驱动因素。 拟议工作的更广泛的教育影响包括康涅狄格大学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上次冰消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、西南太平洋以及东热带太平洋。 每个岩心都是从中间深度（~1000 m）取回的，该深度应该对通过水柱落下的有机物的量敏感。 该团队将通过分析底栖（海底居住）和浮游（表层海洋居住）生物化石中的碳同位素比率来评估光合作用的变化。 研究小组还将分析底栖化石中硼与钙的比例，以推断中间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