Diagnosing the origin of isotopically light carbon in the South Atlantic during the last deglaciation: An oceanic or geologic source?

诊断上次冰消期期间南大西洋同位素轻碳的起源：海洋还是地质来源？

• 批准号: 1404915
• 负责人: David Lund
• 金额: $ 30.67万
• 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: 2014
• 资助国家: 美国
• 起止时间: 2014-06-01 至 2017-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1404915&HistoricalAwards=false
• 关键词: Diagnosing; origin; isotopically; light; carbon

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 the large Northern Hemisphere ice sheets 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 coincided with a negative carbon isotopic excursion. Similar although larger carbon isotope anomalies occurred at surface and intermediate depths in multiple ocean basins, pointing to an oceanic source. The largest documented changes occurred from ~1 to 2 km in the Atlantic, suggesting that processes at mid-depth in this basin played a key role in the CO2 rise. Identifying the origin of the carbon isotope signal is essential to unraveling the mechanisms that drove atmospheric CO2 variability in the recent geologic past. The primary goal of this project is to use data from the Southwest Atlantic to diagnose the source of the carbon isotope anomalies during the deglaciation. The researcher team will use a depth transect of high resolution sediment cores from the Brazil Margin to evaluate the relative timing of surface and deep water signals. The team will also use radiocarbon and other chemical analyses of microfossils to infer the origin of the carbon isotope anomaly. Work will focus on testing two competing hypotheses, one that calls for carbon originating from the abyssal ocean and the other that invokes carbon from a geological reservoir. The results could transform our understanding of the climate system by constraining the source of carbon isotopic minima and therefore the driver of atmospheric CO2 variability on glacial-interglacial timescales. The educational broader impacts of the proposed work include the participation of a graduate student and two undergraduates who will pursue independent research projects that complement the overall goals of the project.

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）。 随着北半球大型冰盖的融化，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得到充分解释。 最近的冰核结果表明，二氧化碳的升高与负同位素的负碳相吻合。 尽管较大的碳同位素异常发生在表面和多个海盆中的中间深度，但指向海洋来源。 最大的记录变化发生在大西洋的〜1至2公里，这表明该盆地中期的过程在CO2上升中起着关键作用。 识别碳同位素信号的起源对于揭开在最近地质过去的大气二氧化碳变异性的机制至关重要。该项目的主要目标是使用来自西南大西洋的数据来诊断脱胶过程中碳同位素异常的来源。 研究人员团队将使用来自巴西边缘的高分辨率沉积物核心的深度样本来评估表面和深水信号的相对时间。 该团队还将使用微化石的放射性碳和其他化学分析来推断碳同位素异常的起源。 工作将着重于测试两个相互竞争的假设，一个假设要求碳起源于深渊海洋，另一种源自从地质储层中引用碳的碳。结果可以通过限制碳同位素最小值的来源，从而改变我们对气候系统的理解，从而改变冰川间冰期时间刻度的大气二氧化碳变异性的驱动力。 拟议工作的教育更广泛的影响包括研究生和两个大学生的参与，他们将追求独立的研究项目，以补充该项目的整体目标。