Continuous-depth analysis of soluble greenhouse gases in ice cores

我们大气中的温室气体水平继续急剧上升。二氧化碳、甲烷和一氧化二氮的浓度至少高于地球历史上过去80万年的水平。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？什么样的反馈可能会被触发，或者超过什么样的临界点？突然的变化会以多快的速度发生？对于这些问题的答案，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，我们可以直接测量温室气体的过去变化。目前最先进的冰芯分析方法是在冰芯缓慢融化时连续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，并在厘米级分辨率上产生了前所未有的记录。然而，二氧化碳，最重要的温室气体，和一氧化二氮，还不能以这种方式测量，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数十年至数百年的人类相关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度可溶的气体。当冰棒融化时，这两种气体都很快溶解在水中，很难回收。该项目将开发一种新的方法，有效地从融化的冰芯连续流中提取二氧化碳和一氧化二氮。将对影响溶出度的一系列因素进行系统测试和优化。气体将用一套专门适用于从冰中获得的低气体流速的激光光谱仪进行测量。对融水的平行测量将用于限制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水平的选定南极冰芯样本进行测试，以证明这种创新方法相对于传统技术的可靠性。这项探索性的工作推动了我们测量冰芯中温室气体的方式的突破。一种在线的、连续的方法，可以对三种主要的温室气体进行高分辨率的测量，这将彻底改变冰芯科学。不到十年前，最先进的甲烷离散技术需要多年的分析才能获得典型的冰芯记录。如今，同样的分析可以在几个月内完成。这使冰芯气体研究进入了一个新的、数据丰富的时代。这项工作旨在为二氧化碳和一氧化二氮的科学研究带来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.