Variability in the Atlantic Meridional Overturning Circulation During Marine Isotope Stage 3

古气候数据显示，在上一个冰河时代，地球的气候发生了巨大变化。从寒冷到温暖的北大西洋气候状态的突然转变，相隔数千年，通常与大气中二氧化碳浓度的增加有关。虽然地表气候在较短的千年时间尺度上也有所不同，但大气二氧化碳在这一时间尺度上的变异性可以忽略不计。大气二氧化碳浓度在较长时间尺度上的变化以及地表气候在两个时间尺度上的变化通常归因于深海内环流的变化，但我们对上一次冰期期间深海环流变异性的了解有限。要了解深海环流变化对地表气候和大气碳的影响，需要详细了解冰川环流的变化情况。该项目支持对一名本科生和一名研究生的教育和培训。作为这项研究的一部分而产生的所有数据都将公开。这些数据对气候模型界也将是有价值的，他们使用古气候数据来测试用于预测未来气候变化的相同模型。海底水温估计将被用于识别过去65,000年来深海环流变化的时间，这些估计是根据热带北大西洋沉积物核心的海底有孔虫的元素比率确定的。模型预测，随着源自北大西洋地区的深层大西洋水的减弱，沉积核心的位置和深度(~550m)将出现大规模而快速的变暖。沉积岩芯具有高的积累速率(30厘米/KYR)，磁化率的变化可以直接与格陵兰冰芯的变化联系在一起。拟议的放射性碳和浮游有孔虫分析将进一步完善年代学。重建上一次冰期期间的深海变异性对于了解深海环流在驱动冰川大气二氧化碳变异性方面的作用至关重要，这种变异性通常只在较长的、几千年的时间尺度上有很大变化。另一方面，确认深海环流在较短的千年时间尺度上确实(或没有)变化，将有助于确定在没有深海环流变化的情况下，是否观察到热带大西洋水文学发生了较大的气候变化。这一发现将意味着，在海洋动力学没有变化的情况下，北大西洋的降温事件会对气候产生重大而广泛的影响。

Paleoclimate data show that the Earth's climate varied dramatically during the last ice age. Abrupt transitions from cold to warm North Atlantic climate states, spaced several millennia apart, were generally associated with increases in atmospheric carbon dioxide concentrations. While surface climate also varied on shorter, millennial time scales, atmospheric carbon dioxide variability on this time scale was negligible. Changes in atmospheric carbon dioxide concentrations on the longer times scale, and surface climate on both time scales, are generally attributed to changes in circulation within the deep ocean, but our knowledge of deep ocean circulation variability during the last ice age is limited. Detailed knowledge of glacial circulation variability is required to understand the influence of deep ocean circulation variability on surface climate and atmospheric carbon. This project supports education and training of an undergraduate student and a post-graduate investigator. All data generated as part of this study will be made publicly available. The data will also be valuable to the climate modeling community, which uses paleoclimate data to test the same models used to predict future climate change.Bottom water temperature estimates, determined from elemental ratios of benthic foraminifera, from a tropical North Atlantic sediment core, will be used to identify times of deep ocean circulation change during the last 65,000 years. Models predict large and rapid warming at the location and depth (~550 m) of the sediment core in association with a weakening of deep Atlantic water originating from the North Atlantic region. The sediment core has high accumulation rates (30 cm/kyr), and variations in magnetic susceptibility that can be tied directly to Greenland ice core δ18O variations. Proposed radiocarbon and planktonic foraminiferal δ18O analysis will further refine the chronology. Reconstructing deep ocean variability during the last ice age is critical to understanding the role of deep ocean circulation in driving glacial atmospheric carbon dioxide variability, which generally varies significantly only on longer, multi-millennial, time-scale. On the other hand, confirming that deep ocean circulation did (or did not) vary on the shorter millennial time scale will help determine whether or not observed large climate shifts in, for example, tropical Atlantic hydrology, occurred in the absence of deep ocean circulation change. Such a finding would imply that episodes of North Atlantic cooling have significant and widespread climate impacts in the absence of changes in ocean dynamics.