Continuous-depth analysis of soluble greenhouse gases in ice cores

大气中的温室气体含量继续急剧上升。二氧化碳、甲烷和一氧化二氮的浓度至少高于过去80万年的地球历史。随着地球变暖，我们面临着一个不确定的未来：我们的气候系统将如何应对？什么样的反馈会被触发，或者引爆点会被超越？突变发生的速度有多快？要找到这些问题的答案，我们可以回顾过去。极地冰芯特别有用，因为它们保存着古代空气的样本，我们可以直接测量过去温室气体的变化。目前最先进的冰芯分析是在一根冰芯慢慢融化的过程中不断测量水和空气的化学成分。这种方法已被证明对甲烷非常有效，并在厘米尺度分辨率上创造了前所未有的记录。然而，最重要的温室气体二氧化碳和一氧化二氮还不能用这种方法测量，这限制了我们可以解决的细节。至关重要的是，我们目前的方法很难解决二氧化碳和一氧化二氮在与人类相关的几十年到几个世纪的时间尺度上的自然变化。主要的挑战是二氧化碳和一氧化二氮是高可溶性气体。当冰棒融化时，这两种气体都迅速溶解在水中，很难恢复。该项目将开发一种新方法，从融化的冰芯连续流中有效地提取二氧化碳和一氧化二氮。一系列影响溶解程度的因素将被系统地测试和优化。气体将用一套激光光谱仪进行测量，这套激光光谱仪专门用于从冰中获得的低气体流速。对融水的平行测量将用于约束大气中二氧化碳和富含碳酸盐的尘埃之间的相互作用。将对具有不同温室气体含量的选定南极冰芯样品进行试验，以证明这种创新方法相对于传统技术的可靠性。这项探索性工作推动了我们在测量冰芯中温室气体的方式上的突破。一种能够对三种主要温室气体进行高分辨率在线连续测量的方法将彻底改变冰芯科学。不到十年前，最先进的甲烷分离技术需要多年的分析才能产生一个典型的冰芯记录。今天，同样的分析可以在几个月内完成。这使得冰芯气体研究进入了一个数据丰富的新时代。这项工作旨在为二氧化碳和氧化亚氮的科学研究提供类似的重大规模转变。

Greenhouse gas levels in our atmosphere continue to rise steeply. Concentrations of carbon dioxide, methane and nitrous oxide are higher than at least the last 800,000 years of Earth's history. As our planet warms as a result, we face an uncertain future: how will our climate system respond? What feedbacks might be triggered, or tipping-points surpassed? And how quickly could abrupt changes occur? For answers to these questions, we can look to the past. Polar ice cores are particularly useful because they hold samples of ancient air, on which we can directly measure past changes in greenhouse gases. The current state-of-the-art in ice core analysis involves measuring the chemistry of water and air continuously as a stick of ice core is slowly melted. This method has proven highly effective for methane and has produced unprecedented records at centimetre-scale resolution. However, carbon dioxide, the most important greenhouse gas, and nitrous oxide, cannot yet be measured in this way, which limits the detail we can resolve. Crucially, our current methods make it difficult to resolve natural variability in carbon dioxide and nitrous oxide over human-relevant timescales of decades to centuries. The major challenge is that carbon dioxide and nitrous oxide are highly soluble gases. When ice sticks are melted, both gases quickly dissolve in the water and are difficult to recover. This project will develop a new method to efficiently extract carbon dioxide and nitrous oxide from a continuous stream of melted ice core. A range of factors impacting the degree of dissolution will be systematically tested and optimised. Gases will be measured with a suite of laser spectrometers specially adapted for the low gas flow rates obtained from ice. Parallel measurements on meltwater will be used to constrain the interaction between atmospheric carbon dioxide and carbonate-rich dust. Tests will be carried out on selected Antarctic ice core samples with different greenhouse gas levels to demonstrate the reliability of this innovative method relative to traditional techniques. This exploratory work pushes for a breakthrough in the way we measure greenhouse gases in ice cores. An online, continuous, method that enables high-resolution measurements of the three major greenhouse gases would revolutionise ice core science. Less than a decade ago, state-of-the-art discrete techniques for methane would require many years of analysis to produce a typical ice core record. Today, the same analysis can be done within a few months. This has shifted ice cores gas studies to a new, data-rich era. This work aims to enable a similarly significant scale-shift for scientific studies of carbon dioxide and nitrous oxide.