EAGER: Improving Ice Core Observations of Large Volcanic Eruptions, and Their Effect on Global Climate Change, with a Novel Sulfur Isotope Method

现代行星尺度变暖的归因与太阳输出，温室气体，自然（火山）和人为气溶胶的强迫之间是一个具有挑战性的和重要的问题。迄今为止，大型火山爆发的冷却效果是通过测量冰芯中的硫酸盐浓度来确定的。然而，只有将二氧化硫注入平流层的火山才能导致全球持续降温，因为对流层中新气溶胶的降雨非常有效。我们需要一种方法来区分那些在冰芯记录中含有大量硫酸盐但没有平流层影响的火山（如圣海伦斯火山爆发）和那些到达平流层的火山，以便在气候归因研究中将它们从火山强迫作用中排除。幸运的是，向平流层注入SO2会在所产生的硫酸盐气溶胶中留下与质量无关的同位素信号。这项研究由加州理工学院的一位教授领导，建立在一种测量小样本硫同位素的新技术基础上，该技术将相关同位素系统的检测限降低了三个数量级以上。这一新方法将用于生成过去1,000年中前100次火山事件冰芯中硫同位素变化的时间序列。研究人员将确定哪些火山爆发实际上进入了平流层，因此导致了全球气候变冷。这些都是气候变暖归因研究中必须考虑的事件。这项研究将集中在格陵兰岛南部的冰芯上。某些事件将在南极冰芯中进行交叉检查，以确认硫酸盐气溶胶的全球分布。这项工作的结果可能会改变我们对气候对二氧化碳增加敏感性的理解。成果将为教育外联工作提供信息。资金还支持一个早期的职业科学家。

The attribution of modern planetary scale warming between forcings associated with solar output, greenhouse gases, and both natural (volcanic) and anthropogenic aerosols is a challenging and important problem. To date the cooling effect of large volcanic eruptions has been determined by measuring sulfate concentrations in ice cores. However, only volcanoes that inject sulfur dioxide into the stratosphere can cause sustained global cooling as the rain out of new aerosols in the troposphere is very efficient. We need a way to distinguish volcanoes with large amounts of sulfate in the ice core record, but no stratospheric impact (like the Mount St. Helens eruption), from those that reached the stratosphere, so that they can be taken out of the volcanic forcing function in climate attribution studies.Fortunately, injection of SO2 into the stratosphere leaves a mass independent isotopic signal on the sulfur of the resulting sulfate aerosols. This research, led by a professor at the California Institute of Technology, builds on a new technique for measuring sulfur isotopes on small samples that lowers the detection limit the relevant isotopic systems by over three orders of magnitude. This new method will be used to generate a time series of sulfur isotope variability in ice cores of the top 100 volcanic events of the last 1,000 years. The researchers will identify which volcanic eruptions actually entered the stratosphere and therefore caused a global climate cooling. These are the events that must be accounted for in climate warming attribution studies. The research will focus on an ice core from South Greenland. Certain events will be cross-checked in ice cores from Antarctic to confirm the global distribution of sulfate aerosol. The results of this work could be potentially transformative in changing our understanding of the sensitivity of climate to CO2 increases. Outcomes will inform educational outreach efforts. Funding also supports an early career scientist.